Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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31738 Publications
Pressure independence of intensity clamping during filamentation: theory and experiment
Bernhardt, J.; Liu, W.; Chin, S. L.; Sauerbrey, R.;
Because of the dynamic equilibrium between Kerr self-focussing and plasma induced defocusing
and the inexistence of collisional ionization the critical intensity during femtosecond laser
filamentation in air is independent of pressure. An analytical analysis is given which is justified
by a direct experimental verification.
PACS: 42.65.Jx, 52.38.Hb, 52.70.Kz
Keywords: Pressure independence of intensity clamping during filamentation; Theory and experiment
  • Applied Physics B 91(2008)1, 45-48

Publ.-Id: 11012 - Permalink


Laser-Particle-Acceleration
Sauerbrey, R.; Schramm, U.; Keywords: Laser-Particle-Acceleration Electron laser field Laser ion acceleration Applications
  • Invited lecture (Conferences)
    GSI Kolloquium, 22.01.2008, Darmstadt, Deutschland

Publ.-Id: 11011 - Permalink


Laser-driven proton oncology - a unique new cancer therapy?
Ledingham, K. W. D.; Galster, W.; Sauerbrey, R.;
In 2000, the University of Strathclyde, collaborating with the Rutherford Appleton Laboratory, organized the first workshop dealing with the potential of highpower laser technology in medicine. Two areas of potential were identified: firstly the production of positron emission tomography (PET) isotopes; and secondly, the potential for laser-accelerated proton and heavy ion beams for therapy. The attendees, mainly clinicians and radiation physicists, emphasised that the laser community should concentrate on developing laser and target technology for therapy rather than isotope production because of the potential advantages over conventional accelerator technology for that purpose. On the 30 March 2007, the universities of Strathclyde and Paisley organized a follow-up meeting to identify the progress made in laser-driven proton and ion beam technology with applications leading to proton and ion beam therapy for deep-seated tumours. The meeting was supported by the Scottish Uni!
versities Physics Alliance (SUPA) - an organization set up in Scotland to bring together all of the physics departments collaborating with life scientists to work on ground-breaking new science which no single university could attempt. This is a summary of the meeting.
Keywords: highpower laser technology in medicine positron emission tomography (PET) laser-accelerated proton and heavy ion beams for therapy laser-driven proton and ion beam technology

Publ.-Id: 11009 - Permalink


Yttrium-86-labelled human serum albumin microspheres: relation of surface structure with in vivo stability
Schiller, E.; Bergmann, R.; Pietzsch, J.; Noll, B.; Sterger, A.; Johannsen, B.; Wunderlich, G.; Pietzsch, H.-J.;
Introduction:
Radiolabelled particles are an attractive tool in the therapy of malignancies of the liver. We consider particles manufactured from denatured human serum albumin (HSA) as useful carriers of therapeutic radionuclides. Covalent attachment of suitable chelators onto the surface of the spheres promises an easy access to radiolabelled HSA microspheres.

Methods:
We synthesized 1,4,7,10-tetraazacyclododecane-N,N′,N″,N‴-tetraacetic acid (DOTA) bearing smooth, medium-rough and rough surfaced HSA microspheres (mean diameter: 25 μm). In vitro stability of 86Y-labelled particles was determined after incubation in human plasma and in a DTPA challenge experiment. In vivo stability of 86Y DOTA-HSA microspheres was determined after single intravenous application in rats. Subsequently, the particles were completely trapped in the lung microvasculature. Thus, the lung serves in our experiments as target organ.

Results:
DOTA-HSA microspheres were 86Y labelled in reproducible high yields (N95%). No differences between smooth and rough surfaced spheres were found for both DOTA coupling and 86Y labelling. Labelled microspheres showed high in vitro stability in human plasma and in DTPA solution with only 8±1% and 2±0% loss of radioactivity from the surface, respectively, 48 h postinjection (pi). The three batches (smooth, medium-rough and rough surfaced microspheres) differed considerably in their radioactivity recovery in the lungs of rats 48 h pi. Smooth particles showed the highest in vivo stability of the radiolabel on the surface of the spheres, presumably because of slower proteolytic degradation.

Conclusion:
We found that for the preparation of HSA-derived microspheres for radiotherapeutic application, smooth surfaced spheres are superior to rough spheres due to their higher in vivo stability of the radionuclide fixation.
Keywords: Human serum albumin microspheres; Yttrium-86; In vivo stability; Radiolabelled particles; Radiotherapy

Publ.-Id: 11008 - Permalink


Präparative Reinigung polarer, mehrfunktionaler Liganden
Röhrich, A.;
kein Abstract verfügbar
  • Lecture (others)
    Workshop - Möglichkeiten und Grenzen der HPLC in den Lebenswissenschaften, 01.02.2008, Dresden, Deutschland

Publ.-Id: 11007 - Permalink


Soft X-ray Absorption and Emission Spectroscopic Investigation of Carbon and Carbon:Transition Metal Composite Films
Abrasonis, G.; Berndt, M.; Krause, M.; Kuepper, K.; Munnik, F.; Kolitsch, A.; Möller, W.;
Carbon and C:V, C:Co, C:Cu nanocomposite films grown by ion beam cosputtering in the temperature range from room temperature (RT) to 500 °C are investigated. Soft X-ray absorption spectroscopy (XAS) and X-ray emission spectroscopy (XES) have been used to determine electronic structure of the occupied and unoccupied electronic states of the coexisting carbon and transition metal (TM) constituents. The results from the spectroscopy are supplemented by the film composition data and TM inclusion phase structural information obtained by elastic recoil detection analysis and X-ray diffraction, respectively. The TM(2p) XAS shows that V (Cu) is in carbidic (metallic) state over the whole temperature range, while Co shows a transition from a carbidic toward a metallic state when the growth temperature increases from RT to 500 °C. The C(1s) XAS demonstrates that the increase in the growth temperature favors the formation of graphite-like structures in carbon films. On the other hand, the TM metal incorporation strongly promotes the sp3 admixture in the surrounding carbon phase which manifests itself through a significant increase in the intensity of a feature in the C(1s) XAS spectra positioned at ~291 eV resulting from 1s → σ* transitions. In addition, the codeposition of TM atoms with carbon enhances the formation of carbon structures with the prominent peak between π* and σ* regions in the C(1s) XAS spectra positioned at ~288.5 eV. The effect is independent of the TM tendency to form carbides or TM state (carbidic metallic) while its magnitude increases concomitantly with the TM content and decreases when the crystallinity degree of the inclusion phase increases. The results are discussed on the basis of the nanoparticle imposed curvature on the surrounding carbon network and interactions at the atomic level at the C−TM interfaces.

Publ.-Id: 11005 - Permalink


Question of dynamic chirality in nuclei: The case of 134Pr
Tonev, D.; de Angelis, G.; Brant, S.; Petkov, P.; Dewald, A.; Dönau, F.; Balabanski, D. L.; Zhong, Q.; Pejovic, P.; Bazzacco, D.; Bednarczyk, P.; Camera, F.; Curien, D.; Della Vedova, F.; Fitzler, A.; Gadea, A.; Lo Bianco, G.; Lenzi, S.; Lunardi, S.; Marginean, N.; Möller, O.; Napoli, D. R.; Orlandi, R.; Sahin, E.; Saltarelli, A.; Valiente Dobon, J.; Zell, K. O.; Zhang, J.-Y.; Zhang, Y. H.; Frauendorf, S.;
Lifetimes of exited states in 134Pr were measured by means of the recoil distance Doppler-shift and Doppler-shift attenuation techniques. The branching ratios and the electric or magnetic character of the transitions were also investigated. The experiments were performed at IReS, Strasbourg, using the EUROBALL IV spectrometer, in conjunction with the inner bismuth germanate ball and the Cologne coincidence plunger apparatus. Exited states in 134Pr were populated in the fusion-evaporation reaction 119Sn(19F, 4n)134Pr. The possible chiral interpretation of twin bands was investigated in the two-quasiparticle triaxial rotor and interacting boson-fermion-fermion models. The analysis of the wave functions has shown that the possibility for the angular momenta of the proton, neutron, and core to find themselves in the favorable, almost orthogonal geometry, is present but is far from being dominant. The structure is characterized by large beta and gamma fluctuations. The existence of doublets of bands in 134Pr can be attributed to weak chirality dominated by shape fluctuations.

Publ.-Id: 11004 - Permalink


n+ doping of Ge by P implantation and subsequent RTA or FLA
Posselt, M.; Wündisch, C.; Schmidt, B.; Anwand, W.; Grötzschel, R.; Mücklich, A.; Skorupa, W.; Hortenbach, H.; Gennaro, S.; Bersani, M.; Guibertoni, D.; Möller, A.; Pelzing, P.; Clarysse, T.; Simoen, E.; Satta, A.; Bracht, H.;
Abstract not available. For details, please contact the first author.
Keywords: Electrical doping, Germanium, Ion Implantation, Diffusion, Activation
  • Lecture (others)
    Seminar talk at IMEC Leuven (Belgium), 07.02.2008, Leuven, Belgium

Publ.-Id: 11003 - Permalink


Neptunium(V) reduction by humic substances of varying functionality
Schmeide, K.; Bernhard, G.;
The time dependence of the reduction of Np(V) to Np(IV) by humic substances of varying functionality has been studied under anaerobic conditions between pH 3.5 and pH 9.0. Synthetic humic acids with pronounced redox functionality were studied in comparison to natural humic substances. For Np redox speciation in solution solvent extraction, NIR absorption spectroscopy and ultrafiltration were applied. Exemplary, the application of a synthetic HA is shown for the study of the Np(IV) sorption onto kaolinite in the presence of HA.
Keywords: neptunium, pentavalent, tetravalent, humic acid, sorption, reduction
  • Contribution to proceedings
    Plutonium Futures “The Science” 2008, 07.-11.07.2008, Dijon, France
  • Poster
    Plutonium Futures “The Science” 2008, 07.-11.07.2008, Dijon, France

Publ.-Id: 11002 - Permalink


Hydrophile, macrocyclische Amine: Reinigung mit Problemen
Ruffani, A.;
kein Abstract verfügbar
  • Lecture (others)
    Workshop „Möglichkeiten und Grenzen der HPLC in den Lebenswissenschaften“, 01.02.2008, Dresden-Rossendorf, Deutschland

Publ.-Id: 11001 - Permalink


Bis(2-pyridylmethyl) derivatives of 1,4,7-triazacyclononane: promising ligands for radiolabeling of biomolecules
Ruffani, A.;
kein Abstract verfügbar
  • Lecture (Conference)
    5th SUPRAPHONE Meeting, 29.05.-01.06.2008, Prague, Czech Republic

Publ.-Id: 11000 - Permalink


1,4,7-Triazacyclononane (TACN) ligands with pendant pyridyl arms - New versatile bifunctional chelating agents (BFCAs)
Ruffani, A.; Stephan, H.; Steinbach, J.; Gasser, G.; Spiccia, L.; Graham, B.;
INTRODUCTION
Radiopharmaceuticals based on metallic radionuclides, such as 64/67Cu, 99mTc, 186/188Re and 86/90Y, are often used for diagnostic and therapeutic purposes (1, 2). These nuclides are usually enveloped in organic ligands, such as heteromacrocyclic systems. To be effective, the ligands have to show fast metal complexation kinetics, form complexes with high in vitro and in vivo stability and contain a group that can be linked to biomolecules. We have developed a new ligand scaffold - based on bis(2-pyridylmethyl)triazacyclononane (DMPTACN) – that satisfies these requirements. This structure allows for the introduction of linker groups, such as carboxylic acids, maleinimide or isothiocyanate, thereby facilitating coupling of targeting molecules.

RESULTS AND DISCUSSION
A new TACN derivative, containing two pyridyl pendant arms as well as a carboxylic group for coupling to biomolecules has been synthesized and its copper(II) binding properties investigated. Conjugation of a stabilized octapeptide (bombesin βAla-βAla-[Cha13, Nle14]) was successfully achieved via amide coupling (3). Both the free ligand and the bombesin bioconjugate can rapidly form very stable radiocopper complexes. In vitro ligand competition experiments and stability studies in rat plasma medium gave no evidence of transchelation or demetalation. Biodistribution studies of the bombesin conjugate revealed an accumulation of the compound in the pancreas, which is the organ with highest levels of gastrin-releasing peptide receptor (GRPR) targeted by bombesin.
Our radiopharmalogical data indicate that bifunctional chelating TACN agents are attractive candidates for developing new copper radiotherapeutics. In this perspective, particular BFCAs will be attached to carrier molecules, such as oligonucleotides, antibodies and synthetic polymers, to deliver radiocopper isotopes to target tissues.

REFERENCES
1. Anderson C.J., Welch M.J. (1999) Metal complexes as diagnostic tools. Coord. Chem. Rev. 184, 3-66.
2. Volkert W.A., Hoffman T.J. (1999) Therapeutic radiopharmaceuticals. Chem. Rev. 99, 2269-2292.
3. Gasser G., Tjioe L., Graham B., Belousoff M. J., Juran S., Walther M., Künstler J.U., Bergmann R., Stephan H., Spiccia L. (2008)
Synthesis, Copper(II) Complexation, 64Cu-Labeling, and Bioconjugation of a New Bis(2-pyridylmethyl) Derivative of 1,4,7-
Triazacyclononane. Bioconjugate Chem. In press
  • Lecture (Conference)
    7th International Symposium on Polymer Therapeutics: from Laboratory to Clinical Practice, 26.-28.05.2008, Valencia, Spain

Publ.-Id: 10999 - Permalink


Patterning of magnetic structures on austenitic stainless steel by ion beam nitriding
Menendez, E.; Martinavicius, A.; Liedke, M. O.; Abrasonis, G.; Fassbender, J.ORC; Sort, J.; Surinach, S.; Baro, M. D.; Nogues, J.
Nitriding of austenitic stainless steel (ASS) at moderate temperatures (~400ºC) leads to the formation of the supersaturated nitrogen solid solution often called in the literature “expanded austenite” or γN phase [1,2]. This causes an enhancement of the microhardness and the wear resistance without loss of the corrosion resistance. Moreover, this phase shows ferromagnetic behavior, whose origin is linked to the expansion of the austenite (γ) lattice due to the incorporation of nitrogen atoms into interstitial positions [3,4]. Actually, since there is a nitrogen depth profile and the onset of ferromagnetism is connected with nitrogen concentrations of ~15 at.%, the nitrided layer consists of two magnetically different parts (paramagnetic and ferromagnetic) determined by the obtained nitrogen concentration.

In this study, we report the influence of the nitriding temperature and time on the ASS ferromagnetic properties. AISI 304L ASS polycrystalline samples (discs of 10 mm diameter and 2 mm thickness) have been ion beam nitrided in the temperature range of 300-400ºC. The ion energy and the ion current density were ~1 keV and 0.5 mA/cm2 (the corresponding ion flux of ~5•1015 ions•cm-2•s-1), respectively. The processing times were 5 and/or 30 minutes [2]. Periodic arrays of ferromagnetic structures in the micrometer range have been prepared at the surface of the samples using a 2000 mesh Cu transmission electron microscopy grid as a shadow mask (mesh size of 7.5 x 7.5 µm2, 12.5 µm pitch, 20 µm thickness and 3.05 mm diameter). The structure was characterized by X-ray diffraction (XRD) and nuclear reaction analysis (NRA). The magnetic properties were determined by magneto-optical Kerr effect (MOKE) and magnetic force microscopy (MFM).
The XRD patterns of the nitrided ASS samples are presented in Figure 1. The XRD pattern consistent with the FCC lattice structure can be identified for the virgin ASS sample (not shown). For the nitrided samples, each austenite peak exhibits a satellite peak, located at lower diffraction angles which is related with the formation of the “expanded austenite”. The amount of this “expanded” phase increases with the processing temperature, as it is evidenced by the increase of intensity of the γN XRD peaks in detriment to the γ ones.
This is consistent with NRA observations. For instance, a nitrided layer of around 1 µm depth is obtained in the sample nitrided at 400ºC for 30 min, whereas ~15 at.% of nitrogen is obtained around 0.5 µm of depth.
MOKE measurement results of the virgin and the nitrided sample at 400°C for 5 min are compared in Figures 2(a) and 2(b) (patterned area).
It can be seen that the virgin sample does not show any hysteretic behavior, i.e. it is non-ferromagnetic. Conversely, the nitrided samples show clear hysteresis loops indicating the existence of ferromagnetic constituents in the nitrided layer. Figure 2(c) shows the AFM image of a patterned area of the nitrided sample which shows that a moderate sputtering process of the surface has taken place during nitriding resulting in the formation of the periodic array of squared pits. Figure 2 (d) is the corresponding MFM image in an applied magnetic field of 70 mT, where a magnetic dipolar contrast can be clearly seen in each entity, confirming the feasibility of the production of periodic arrays of isolated ferromagnetic structures. It is worth noting that the hysteresis behavior of the continuously nitrided areas and the patterned ones are quite similar due to the fact that the induced ferromagnetic structures are relatively large (micrometer range), leading to entities with magnetic multi-domain configurations.

[1] M.P. Fewell et al., Surf. Coat. Technol. 131, 300 (2000)
[2] G. Abrasonis, et al., J. Appl. Phys. 97, 083531 (2005)
[3] O. Öztürk and D.L. Williamson, J. Appl. Phys. 77, 3839 (1995)
[4] J. Baranowska, Vacuum 81, 1216 (2007)
Keywords: magnetism, stainless steel, nitriding, patterning, ion
  • Poster
    International Conference on Magnetics, Intermag 2008, 04.-08.05.2008, Madrid, Spain

Publ.-Id: 10998 - Permalink


Sc3AlN - A New Perovskite
Höglund, C.; Birch, J.; Beckers, M.; Alling, B.; Czigány, Z.; Mücklich, A.; Hultman, L.;
Sc3AlN with perovskite structure has been synthesized as the first ternary phase in the Sc-Al-N system. Magnetron sputter epitaxy at 650 °C was used to grow single-crystal, stoichiometric Sc3AlN(111) thin films onto MgO(111) substrates with ScN(111) seed layers as shown by elastic recoil detection analysis, X-ray diffraction, and transmission electron microscopy. The Sc3AlN phase has a lattice parameter of 4.40 Å, which is in good agreement with the theoretically predicted 4.42 Å. Comparisons of total formation energies show that Sc3AlN is thermodynamically stable with respect to all known binary compounds. Sc3AlN(111) films of 1.75 µm thickness exhibit a nanoindentation hardness of 14.2 GPa, an elastic modulus of 249 GPa, and a room-temperature electrical resistivity of 41.2 µΩ cm.

Publ.-Id: 10997 - Permalink


Entwicklung des Neutronentransportcodes TransRay und Untersuchungen zur zwei- und dreidimensionalen Berechnung effektiver Gruppenwirkungsquerschnitte
Beckert, C.;
Standardmäßig erfolgt die Datenaufbereitung der Neutronenwirkungsquerschnitte für Reaktorkernrechnungen mit 2D-Zellcodes. Ziel dieser Arbeit war es, einen 3D-Zellcode zu entwickeln, mit diesem Code 3D-Effekte zu untersuchen und die Notwendigkeit einer 3D-Datenaufbereitung der Neutronenwirkungsquerschnitte zu bewerten. Zur Berechnung des Neutronentransports wurde die Methode der Erststoßwahrscheinlichkeiten, die mit der Ray-Tracing-Methode berechnet werden, gewählt. Die mathematischen Algorithmen wurden in den 2D/3D-Zellcode TransRay umgesetzt. Für den Geometrieteil des Programms wurde das Geometriemodul eines Monte-Carlo-Codes genutzt. Das Ray-Tracing in 3D wurde auf Grund der hohen Rechenzeiten parallelisiert. Das Programm TransRay wurde an 2D-Testaufgaben verifiziert.
Für einen Druckwasser-Referenzreaktor wurden folgende 3D-Probleme untersucht: Ein teilweise eingetauchter Regelstab und Void (Vakuum oder Dampf) um einen Brennstab als Modell einer Dampfblase. Alle Probleme wurden zum Vergleich auch mit den Programmen HELIOS (2D) und MCNP (3D) nachgerechnet. Die Abhängigkeit des Multiplikationsfaktors und der gemittelten Zweigruppenquerschnitte von der Eintauchtiefe des Regelstabes bzw. von der Höhe der Dampfblase wurden untersucht. Die 3D berechneten Zweigruppenquerschnitte wurden mit drei üblichen Näherungen verglichen: Lineare Interpolation, Interpolation mit Flusswichtung und Homogenisierung. Am 3D-Problem des Regelstabes zeigte sich, dass die Interpolation mit Flusswichtung eine gute Näherung ist. Demnach ist hier eine 3D-Datenaufbereitung nicht notwendig. Beim Testfall des einzelnen Brennstabs, der von Void umgeben ist, erwiesen sich die drei Näherungen für die Zweigruppenquerschnitte als unzureichend. Demnach ist eine 3D-Datenaufbereitung notwendig. Die einzelne Brennstabzelle mit Void kann als der Grenzfall eines Reaktors angesehen werden, in dem sich eine Phasengrenzfläche herausgebildet hat.
Keywords: Reactor physics, calculational methods, neutron transport, transport methods, ray tracing, cross sections, cell calculation, absorber rod, void
  • Open Access LogoWissenschaftlich-Technische Berichte / Forschungszentrum Dresden-Rossendorf; FZD-492 2008

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Publ.-Id: 10996 - Permalink


Radiation damage in helium-implanted diamond
Nasdala, L.; Grambole, D.; Harris, J. W.; Wildner, M.; Hofmeister, W.;
Diamond platelets were implanted with 8.8 MeV He2+ ions, the equivalent of alpha particles generated in the natural 212Po ---> 208Pb decay (Th decay chain). Implantation densities were varied in the range 1012 - 1017 ions per cm². Visible green colouration was produced at He2+ fluences _>1015 cm-2. The radioinduced colour is mainly due to a broad absorption band at ca. 16000 cm-1, which is assigned to the GR1 centre. Raman line scans showed that a narrow, stongly damaged area is formed ca. 29 µm below the sample surface. This corresponds very well with the distribution of Frenkel-type defects as predicted by Monte Carlo simulations using the SRIM program 1. Raman data obtained from naturally radiocoloured diamonds are discussed in light of our new results.
1 Ziegler JF, Biersack JP, Littmark U. The stopping and range of ions in solids. Pergamon Press, New York, 1985.
  • Lecture (Conference)
    8th International Conference on Raman Spectroscopy Applied to the Earth Sciences (GeoRaman08), 02.-06.06.2008, Ghent, Belgium
  • Contribution to proceedings
    8th International Conference on Raman Spectroscopy Applied to the Earth Sciences (GeoRaman08), 02.-06.06.2008, Ghent, Belgium
    Book of abstracts, 52

Publ.-Id: 10995 - Permalink


The origin of the Energy-Dose window in Separartion-by-Implanted-Oxygen (SIMOX) materials processing
Koegler, R.; Ou, X.; Skorupa, W.; Moeller, W.;
Separation-by-Implantated-Oxygen (SIMOX) is an established technique to manufacture a buried oxide layer in silicon (SOI) by ion implantation and annealing. The so called energy-dose window defines implantation parameters suitable for the formation of a continuous buried oxide layer with the lowest ion dose. The study concerns the reason why defined combinations of ion energy and ion dose result in a high quality oxide layer. Excess defects induced by the O implantation are shown to influence the oxide layer formation. The depth distribution of excess defects fits very well with the final depth position of the oxide layer for O implants in the energy-dose window.
Keywords: Ion implantation, silicon-on-insulator, SIMOX, defects, oxygen

Publ.-Id: 10994 - Permalink


Comparative investigation of the interaction of uranium with lipopolysaccharide and peptidoglycan
Barkleit, A.; Moll, H.; Bernhard, G.;
Microorganisms are very important for the bioremediation of the environment because they are able to adsorb radionuclides and other heavy metals. They significantly influence mobilization and immobilization of metal ions in soils.
We investigated representative the complexation of the uranyl ion with main parts of bacterial cell walls. Lipopolysaccharide (LPS) is the principal component of the cell wall of gram-negative bacteria, whereas peptidoglycan (PGN) represents the basis of the cell wall of gram-positve bacteria. Both biomolecules contain a high density of metal-binding functionalities like carboxyl, amino, and hydroxyl groups. LPS offers additionally a high amount on phosphoryl groups, which are missing in PGN.
We investigated the interaction of the uranyl cation (UO22+) with the biopolymers LPS and PGN by using potentiometric titration and time-resolved laser-induced fluorescence spectroscopy (TRLFS) over a wide pH range (2.4 – 9) and at environmentally relevant low uranium concentrations (10-4 – 10-5 M).
Using potentiometric titration, the dissociation constants of the respective functional groups were determined. Furthermore essential uranyl complexes and their stability constants were identified.
With the aid of time-resolved laser-induced fluorescence spectroscopy (TRLFS) the luminescence properties of uranyl complexes with the biopolymers and the associated stability constants were investigated. At low pH values both biomolecules effect an increase of the luminescence intensity and a red-shift of about 8-10 nm, compared to the free UO22+ ion. With LPS the luminescence intensity increases up to pH 8. In contrast to LPS, the PGN polymer causes a decrease of the luminescence intensity over pH 4.5, indicating, that a non-luminescent complex has built.
As a result from both methods, we found that the uranyl ion prefers with LPS phosphoryl coordination, whereas PGN, with a lack of phosphoryl groups, forms stable carboxylate complexes.
  • Lecture (Conference)
    5th International Conference Uranium Mining Hydrogeology (UMH V), 14.-18.09.2008, Freiberg, Germany
  • Contribution to external collection
    Broder J. Merkel, Andrea Hasche-Berger: Uranium, Mining and Hydrogeology, Berlin: Springer Verlag, 2008, 978-3-540-87745-5, 753-754

Publ.-Id: 10993 - Permalink


Theoretical study on the highest oxidation states of Pu
Tsushima, S.;
It has been demonstrated recently that quantum chemical calculations can accurately perdict redox potentials of An(VI)/An(V) couples (An = U, Np, Pu, Am) if multireference effect and spin-orbit effects are treated properly [1,2]. The An(VI)/An(V) redox potentials obtained at the multireference CASPT2 level calculations with spin-orbit corrections were found to have fairly good agreement with those obtained by experiments.
Here, I extend such calculations to the higher oxidation states of actinide, namely Pu(VII) and Pu(VIII). Pu(VII) is known to be meta-stable in aqueous solution. Recently, Nikonov et al. have suggested that Pu(VIII) may be obtained by the ozonation of Pu(VI), although they were not able to find a direct evidence for the presence of Pu(VIII) [3]. The present work aims to discuss from a theoretical point of view whether or not Pu(VIII) may exist in water. Geometry optimizations and energy calculations of the complexes were performed at the B3LYP level, and spin-orbit effects were calculated separately at the CASSCF level.
The redox potential of the PuVIIIO4(OH)22-/ PuVIIO4(OH)23- couple was found to be as high as ~1.7V. At very high pH, Pu(VII) may exist as a penta-oxo complex, PuVIIO5(OH)4-. The redox potential of PuVIIIO5(OH)3-/ PuVIIO5(OH)4- couple was found to be ~1.3V. Spin-orbit effect was found to play a very important role for the total redox potential because the ground state energy lowering of Pu(VII) due to the spin-orbit splitting depends highly on the number of coordinating oxo ligands. The effect of coordinating ligands (OH-, CO32- etc.) and coordination number on the total redox potential was also studied. The calculations suggest that Pu(VIII) is unlikely to exist in both acidic and alkaline aqueous solutions, while Pu(VIII) may be present in non-aqueous solvents with a large redox window.

[1] Tsushima,S; Wahlgren, U.; Grenthe, I. J. Phys. Chem. A 2006, 110, 9175.
[2] Shamov, G.A.; Schreckenbach, G. J. Phys. Chem. A 2005, 109, 10961.
[3] Nikonov, M.V.; Gogolev, A.V.; Tananaev, I.G.; Myasoedov, B.F. Radiochemsitry 2004, 46, 340.
Keywords: Plutonium, quantum chemistry, redox potential
  • Lecture (Conference)
    Plutonium Futures "The Science" 2008, 07.-11.7.2008, Dijon, France

Publ.-Id: 10992 - Permalink


Natural and Engineered Nanoparticles in the Environment: A presentation of current activities of the AK Aquatic Nanoscience & Nanotechnology
von der Kammer, F.; Baalousha, M.; Baun, A.; Hassellov, M.; Delay, M.; Thieme, J.; Zänker, H.; Neumann-Hensel, H.; Handy, R.; Hochella, M.;
For more than two decades aquatic chemistry is constantly gaining knowledge about nanoscale processes in the environment. While in early years the co-transport of contaminants in the saturated zone of aquifers has been in the focus of aquatic nanosciences and nanogeosciences, nowadays the research activities have broadened and span across several disciplines. In the course of R & D activities on nanomaterials the question of the behavior, fate and useful or adverse effects of nanoparticles in the environment arose and has boosted the activities quite substantially. The working group Aquatic Nanosciences and Nanotechnology has responded to the current development by inviting European scientists from different fields to contribute their expertise into the group’s discussions and activities while still keeping the core expertise on characterization techniques inherited from the former working group “Colloids”. In 2007 the working group organized an international workshop which was held in Vienna during the 10th and 11th December. The aim of the event was to offer a platform for bridging the different disciplines and exchange the current knowledge in the fields. Scientists from aquatic and environmental chemistry, nanogeosciences, nano-engineering, eco-toxicology and risk assessment presented their contributions to the current state of the art. The overall conclusions drawn from 29 presentations are given.
Keywords: Natural nanoparticles, engineered nanoparticles, environment, natural waters
  • Lecture (Conference)
    Wasser 2008. Jahrestagung der Wasserchemischen Gesellschaft, 28.-30.04.2008, Trier, Germany

Publ.-Id: 10991 - Permalink


Dipole-strength functions studied in photon-scattering experiments at ELBE
Schwengner, R.;
Dipole-strength functions studied in photon-scattering experiments at ELBE
  • Invited lecture (Conferences)
    Seminar, 15.01.2008, Durham, North Carolina, USA

Publ.-Id: 10990 - Permalink


P implantation into preamorphized germanium and subsequent annealing: Solid phase epitaxial regrowth, P diffusion, and activation
Posselt, M.; Schmidt, B.; Anwand, W.; Grötzschel, R.; Heera, V.; Mücklich, A.; Wündisch, C.; Skorupa, W.; Hortenbach, H.; Gennaro, S.; Bersani, M.; Giubertoni, D.; Möller, A.; Bracht, H.;
Phosphorus implantation (30 keV, 3x1015 cm−2) into preamorphized Ge and subsequent rapid thermal or flash lamp annealing is investigated. During annealing a significant P diffusion in amorphous Ge is not observed. However, the fast solid phase epitaxial regrowth causes a rapid redistribution of P. After completion of the regrowth and at temperatures above 500 °C, a concentration-dependent diffusion of P in crystalline Ge takes place and leads to considerable loss of P toward the surface. An appreciable influence of implantation defects on the diffusion coefficient of P is not detected. For 60 s rapid thermal annealing at 600 °C and for 20 ms flash lamp annealing at 900 °C, the junction depth and the sheet resistance vary between 140 and 200 nm and between
50 and 100 Ohm, respectively, and the maximum electrical activation of P is about 3–7 x1019 cm−3
Keywords: Germanium, electrical doping, ion implantation, annealing, diffusion, activation, solid-phase epitaxial regrowth
  • Journal of Vacuum Science & Technology B 26(2008), 430-434

Publ.-Id: 10989 - Permalink


Beschleunigen mit Licht
Schramm, U.; Keywords: Laserplasma Beschleuniger
  • Invited lecture (Conferences)
    Physikalisches Kolloquium, 23.10.2007, Dresden, Germany

Publ.-Id: 10988 - Permalink


Equation of state for strongly interacting matter: collective effects, Landau damping and predictions for LHC
Schulze, R.; Bluhm, M.; Kämpfer, B.;
Abstract for the description of the hydrodynamic phase of strongly interacting matter in relativistic HIC the equation of state (EOS) is of utmost importance. Lattice QCD can provide useful information on the EOS, mainly for small net baryon densities. The QCD quasiparticle model (QPM) provides a means to map lattice results into regions relevant for a variety of experiments. Recent work has enabled us to include collectives modes and damping effects into the QPM. Among physical implications are predictions for forthcoming heavy-ion collisions at LHC/ALICE.
Keywords: QCD, equation of state, EOS, quasiparticle, model, plasmon, plasmino, plasmons, plasminos, quark, gluon, plasma, Landau, damping, characteristics
  • Contribution to proceedings
    XLVI International Winter Meeting on Nuclear Physics, 20.-26.1.2008, Bormio, Italy
    Proceedings of the XLVI International Winter Meeting on Nuclear Physics, Milano: Università degli Studi di Milano, 63-69
  • Contribution to WWW
    arXiv-Preprint: http://arxiv.org/abs/0803.1571
  • Lecture (Conference)
    XLVI International Winter Meeting on Nuclear Physics, 22.01.2008, Bormio, Italien

Publ.-Id: 10987 - Permalink


Prospects for Applications of Laser-Accelerated Particles
Schramm, U.; Sauerbrey, R.;
Invited talk on possible medical applications of laser accelerated particle beams
Keywords: laser ion acceleration, FELs
  • Invited lecture (Conferences)
    International Symposium on Ultrafast Intense Laser Science ISUILS 07, 24.-27.9.2007, Pisa, Italy

Publ.-Id: 10986 - Permalink


Focusing and transport of laser-accelerated protons with quadrupoles
Schollmeier, M.; Geißel, M.; Flippo, K.; Becker, S.; Blazevic, A.; Grüner, F.; Harres, K.; Nürnberg, F.; Rambo, P.; Schramm, U.; Schreiber, J.; Schwarz, J.; Atherton, B.; Habs, D.; Hegelich, B. M.; Roth, M.;
Focusing and transport of laser-accelerated protons with quadrupoles
Keywords: Laser acceleration of ions, beam transport, quadrupole lenses PMQ
  • Contribution to external collection
    in: GSI Jahresbericht, Darmstadt: GSI, 2008

Publ.-Id: 10985 - Permalink


Laser-Particle-Acceleration and Prospects of the application of laser-accelerated particles
Schramm, U.;
Tutorial on laserparticle acceleration and applications of such beams.
Keywords: Tutorial lectures
  • Invited lecture (Conferences)
    International Workshop on Prospectives of High Density Short Pulse Lasers, 07.-11.1.2008, Cairo, Egypt

Publ.-Id: 10984 - Permalink


Complexation studies of Uranium(VI) by Sulfur and Nitrogen Containing Model Ligands in Aqueous Solution
Raditzky, B.; Schmeide, K.; Geipel, G.; Bernhard, G.;
The long-term safety assessment of nuclear waste disposals requires detailed knowledge of the transport and interaction behavior of actinides within the technical, geotechnical and geological barriers. The migration and interaction behavior of actinides can be effectively influenced by humic substances, biopolymers ubiquitous in natural environments, due to their ability for complex and colloid formation and their redox properties. It is known, that especially their carboxylic and phenolic OH groups are able to complex metal ions. In addition to these oxygen containing functional groups, humic substances also offer sulfur and nitrogen containing functionalities.

The aim of this work is to determine the influence of various sulfur and nitrogen containing functional groups on the uranium(VI) complexation and to evaluate their contribution in comparison to oxygen containing functional groups. For this, simple organic model ligands that can occur as building blocks for humic substances are used in the first instance with the objective to transfer the results to humic substances. In this study, results are presented for the uranium(VI) complexation by the organic ligands benzenesulfonic acid and 4-hydrxybenzenesulfonic acid as well as anthranilic and nicotinic acid. The complex formation constants for the uranium(VI) complexation were determined applying time-resolved laser-induced fluorescence spectroscopy (TRLFS) as a function of pH.
Keywords: uranium(VI), fs-TRLFS, TRLFS, benzenesulfonic acid, 4-hydroxybenzenesulfonic acid, anthranilic acid, nicotinic acid, complexation
  • Contribution to proceedings
    Seventh International Conference on Nuclear and Radiochemistry (NRC7), 24.-29.08.2008, Budapest, Hungary
  • Lecture (Conference)
    Seventh International Conference on Nuclear and Radiochemistry (NRC7), 24.-29.08.2008, Budapest, Hungary

Publ.-Id: 10983 - Permalink


Qualitätssicherung bei der PET/CT für die Bestrahlungsplanung
Zips, D.; Richter, C.;
kein Abstract vorhanden, da Vortrag
  • Lecture (others)
    Strahlenschutz und Qualitätssicherung bei modernen strahlentherapeutischen Verfahren und in der klinisch-strahlentherapeutischen Forschung, 08.12.2007, Dresden, Deutschland
  • Lecture (others)
    Strahlenschutz und Qualitätssicherung bei modernen strahlentherapeutischen Verfahren und in der klinisch-strahlentherapeutischen Forschung, 03.-04.04.2009, Dresden, Deutschland

Publ.-Id: 10982 - Permalink


4D-PET/4D-CT Bildgebung und ihre Anwendung in der Strahlentherapie
Richter, C.;
kein Abstract vorhanden, da Vortrag.
  • Lecture (others)
    OncoRay Seminar, 06.12.2007, Dresden, Deutschland

Publ.-Id: 10981 - Permalink


Momentum Control of Charged Particles with Light
Schramm, U.;
Laser cooling at ESR and laserplasma particle acceleration.
Keywords: laser cooling, laser plasma acceleration
  • Invited lecture (Conferences)
    GSI Atomic Physics Seminar, 30.1.2008, Darmstadt, Germany

Publ.-Id: 10980 - Permalink


On three-dimensional magnetic field effects during metal deposition in cuboid cells
Mutschke, G.; Cierpka, C.; Weier, T.; Bund, A.; Eckert, K.; Mühlenhoff, S.; Yang, X. G.; Hess, A.;
This paper will discuss recent experimental and numerical results from the authors' labs on the effects of moderate magnetic fields in electrochemical reactions. It is well established that the influence of the Lorentz force due to external homogeneous magnetic fields, known as magnetohydrodynamic (MHD) effect, manifests itself in the majority of cases in increased mass transport. However, a careful analysis of the governing equations shows that often a three-dimensional modeling of this effect is necessary. We will present numerical simulations of copper electrolysis in cuboid cells under the influence of homogeneous magnetic fields of different directions in the limiting current regime. In most cases there is a complex interplay of natural and magnetically driven convection. A comparison with recent experimental results (flow and concentration gradient visualization) will be given.

Acknowledgments: This work was supported by the German Science Foundation in frame of the collaborative research center 609 "Electromagnetic flow control in metallurgy, crystal growth and electrochemistry"

References:

1) K. Kim & T.Z. Fahidy, "An analysis of free-convective magnetoelectrolysis in constant magnetic fields", J. Electrochem. Soc. 142 (1995) 4196-4204
2) A.Bund, S.Koehler, H.Kuehnlein, W.Plieth, "Magnetic field effects on electrochemical processes", Electrochimica Acta 49 (2003) 147—152.
3) A. Bund, A. Ispas, G. Mutschke, "Magnetic field effects on electrochemical metal depositions", submitted to: Science and Technology of Advanced Materials, 2007
4) T. Weier, K. Eckert, S. Muehlenhoff, C. Cierpka, A. Bund, M. Uhlemann, Electrochem. Commun., 9 (2007) 2479.
Keywords: Magnetoelectrochemistry, Electrolytic metal deposition, magnetic field, Lorentz force
  • Lecture (Conference)
    213th ECS Meeting, 18.-22.05.2008, Phoenix, Arizona, United States
  • ECS Transactions 13(2008)16, 9-13

Publ.-Id: 10979 - Permalink


Minimization of topological defects in ion-induced ripple patterns on silicon
Keller, A.; Facsko, S.; Möller, W.;
The evolution of self-organized nanoscale ripple patterns induced by low energy ion sputtering of silicon was investigated. The quality of the patterns was monitored by calculating a normalized density of topological defects from atomic force microscopy images. A strong dependence of the normalized defect density on the applied ion fluence is observed with a well pronounced minimum at intermediate fluences. Simulations using the damped Kuramoto-Sivashinsky equation yield good agreement with the experiments and are further used to study the dynamics of single pattern defects.

Publ.-Id: 10978 - Permalink


THEREDA – Thermodynamic Reference Database for Nuclear Waste Disposal in Germany
Gester, S.; Altmaier, M.; Brendler, V.; Hagemann, S.; Herbert, H.-J.; Marquardt, C.; Moog, H.; Neck, V.; Richter, A.; Voigt, W.; Wilhelm, S.;
The disposal of radioactive waste including the assessment of long-term safety is an open question in Germany. In addition to the choice of the repository host rock (salt, granite, clay) the basic necessity of a consistent and bindingly used reference database exists. Only by means of such a database it is possible to assess potential failure scenarios accurately and to make well-founded predictions about the long-term safety. Specific needs for waste repository and remediation projects in Germany are comprehensive datasets also covering high temperatures and high salinities. Against this background, available databases (NEA-TDB, IUPAC, NAGRA-PSI) do not suffice all these requests and are limited in their use, partly because of high restrictions and resulting incompleteness of thermodynamic datasets. Other databases rely on heterogeneous and therefore inconsistent data yielding in inadequately reproducible and plausible model calculations. Due to these deficiencies THEREDA, a joint project of institutions leading in the field of safety research for nuclear waste disposal in Germany, was started. It will provide consistent thermodynamic datasets and enhance the transparency and reliability of safety analyses.
Within the project THEREDA we seek to compile data of high quality, accordance and traceability, mainly from existing databases, and to complement this basis particularly with datasets for high saline systems (Pitzer and SIT parameters) and systems at elevated temperatures. Persistent data gaps are closed via estimated values. The identification of such gaps can also aid decisions about the scheduling of experimental programs. Each dataset included in THEREDA is documented in detail and gets a grade of quality attached. Higher grades of quality are allocated to thermodynamic parameters derived from experimental data, namely from non-thermochemical experiments, whereas estimated values determined from systematic trends in thermodynamical behavior or from studies of chemical analogs get lower ratings. Furthermore, numerical data uncertainties and the quality of data sources (primary or secondary literature, peer-reviewed or non-certified) are categorized.
THEREDA will represent a source of information on thermodynamic data that will be publicly accessible and free of charge via Internet (www.thereda.de) and set up on a SQL-database. A broad use of the database is ensured by export functions tailored to important geochemical codes such as EQ3/6, PHREEQC, GWB and ChemApp.
Keywords: THEREDA, database, nuclear waste disposal, long-term safety, thermodynamic data, quality assurance, high saline systems, Pitzer, SIT
  • Contribution to proceedings
    2008 International High-Level Radioactive Waste Management Conference (2008 IHLRW), 07.-11.09.2008, Las Vegas, Nevada, United States
    Steps Toward Reality for Safe Disposal, 978-0-89448-062-1, 287-290
  • Lecture (Conference)
    2008 International High-Level Radioactive Waste Management Conference (2008 IHLRW), 07.-11.09.2008, Las Vegas, Nevada, United States

Publ.-Id: 10977 - Permalink


Sorption of uranium(VI) on ferrihydrite – Influence of atmospheric carbonate on surface complex formation investigated by ATR-FT-IR spectroscopy
Foerstendorf, H.; Heim, K.;
The migration behaviour of uranium in the geosphere is generally influenced by sorption processes in aqueous media. The solubility, mobility and bioavailability is determined by the molecular interactions between the dissolved actinide species and mineral surfaces in groundwater aquifers. In its hexavalent form, uranium usually exists in the environment as the dioxouranyl cation (UO22+) which can form highly soluble complexes with a variety of anionic species commonly increasing the solubility of uranium. However, since there is a high affinity of the UO22+ ion to hydrous iron oxides the mobility of U(VI) can be considerably reduced in the environment. The affinity of U(VI) to hydrous ferric oxides is strongest in the pH range from 5 to 8. But it is also dependent on the composition of the liquid phase. Strong complexing ligands such as carbonate potentially inhibit adsorption of U(VI) onto the mineral phase (1). Therefore, the structures of the uranyl surface complexes at iron hydroxide mineral phases such as hematite and ferrihydrite (Fh) in the presence of CO2 are still in the focus of recent spectroscopic investigations (2,3).
In this work we present results from sorption experiments of U(VI) on Fh using Attenuated Total Reflection Fourier-transform Infrared (ATR-FT-IR) spectroscopy which provide in situ spectral information of the sorption processes in aqueous solution. The sorption of the UO22+ ion was investigated at mildly acidic conditions in atmospheric equilibrium and under an inert gas atmosphere in order to study the influence of dissolved CO2 on the sorption process. The infrared spectra show a similar surface complex of the uranyl ion at the Fh-phase irrespective of the presence of atmospheric CO2. However, the binding of the carbonate ligand to the mineral phase changes considerably upon sorption of the actinide ion and a change from a monodentate to a bidentate binding upon sorption of UO22+ is concluded. Furthermore, we investigated the sorption and desorption behavior of carbonate ions on pristine Fh and after sorption of UO22+ onto the iron oxide phase.

References
(1) Hsi, C. D.; Langmuir, D. Geochim. Cosmochim. Acta 1985, 49, 1931-1941.
(2) Bargar, J. R.; Reitmeyer, R.; Davis, J. A. Environ. Sci. Technol. 1999, 33, 2481-2484.
(3) Ulrich, K. U.; Rossberg, A.; Foerstendorf, H.; Zänker, H.; Scheinost, A. C. Geochim. Cosmochim. Acta 2006, 70, 5469-5487.
Keywords: Ferrihydrite, ATR FTIR spectroscopy, uranium(VI), carbonate, sorption
  • Poster
    7th International Conference on Nuclear and Radiochemistry, 24.-29.08.2008, Budapest, Hungria

Publ.-Id: 10976 - Permalink


Infrared spectroscopic comparison of the aqueous species of uranium(VI) and neptunium(VI)
Müller, K.; Foerstendorf, H.; Brendler, V.; Bernhard, G.;
The distribution of aqueous species of actinide(VI) ions primarily defines their geochemical reactions, e.g. complexation in solution, sorption onto mineral and biological phases, and the formation of colloids, and thus, influences the migration behaviour in the environment. In aqueous solution under normal conditions both uranium and neptunium exist as dioxoactinyl ions AnO2n+ (An = U, Np). They form different complexed species depending on their concentration level, pH range and the presence of potential ligands, such as carbonate.
In recent years, the aqueous U(VI) system has been investigated intensively, in contrast to Np(VI). However, the stability constants used for thermodynamic calculations often arise from non-structural experiments, such as potentiometry and ion exchange, performed at defined sample parameters (1,2). Up to now, a spectroscopic verification of uranyl and neptunyl species is lacking in particular at low concentrations and at neutral pH conditions, reasonably in an environmental context. Thus, speciation modelling using extrapolated data, might be inadequate for the assessment of actinide migration.
In this study we used Attenuated Total Reflectance Fourier-transform Infrared (ATR-FTIR) spectroscopy to compare hydrolysis and carbonate complexation reactions of both U(VI) and Np(VI). Such comparative vibrational study is feasible since the ions NpO22+ and UO22+ are linear and symmetrical. The results are relevant for a comprehensive understanding of actinyl(VI) complexation in aqueous solution.
The experiments were performed at a micromolar concentration level (≤ 100 µM) and in the pH range 2 – 7 under both oxic and anoxic atmosphere. In the infrared spectra the asymmetric stretching vibrations ν3 of the free ions, UO22+ and NpO22+, found in solutions at very acidic pH, are observed at similar wavenumbers, 961 and 964 cm–1. Upon increasing the pH the IR spectra provide evidence for the formation of hydroxo complexes of both actinyl(VI) ions at pH ≥ 3, which is contradictive to current thermodynamic speciation modelling. Since the comparison of the spectral differences between the two actinides show red-shifted bands to a similar extent it can be assumed that analogous hydrolysis species are formed.

(1) Guillaumont, R.; Fanghänel, T.; Fuger, J.; Grenthe, I.; Neck, V.; Palmer, D. A.; Rand, M. H. Update on the Chemical Thermodynamics of U, Np, Pu, Am and Tc.; Elsevier: Amsterdam, 2003.
(2) Grenthe, I.; Fuger, J.; Lemire, R. J.; Muller, A. B.; Nguyen-Trung, C.; Wanner, H. Chemical Thermodynamics of Uranium. ; 1st ed.; Elsevier Science Publishers B. V.: Amsterdam, 1992.
  • Contribution to proceedings
    NRC 7 - Seventh International Conference on Nuclear and Radiochemistry, 24.-29.08.2008, Budapest, Hungary
    Book of Abstracts, 978-963-9319-80-6, 275
  • Poster
    NRC7 - Seventh International Conference on Nuclear and Radiochemistry, 24.-29.08.2008, Budapest, Hungary

Publ.-Id: 10975 - Permalink


U(VI) species sorbed on the green algae Chlorella vulgaris - a TRLFS and EXAFS study
Günther, A.; Roßberg, A.; Raff, J.; Geipel, G.; Bernhard, G.;
Algae in soil and water can have a significant influence on the transport of actinides in the biological and geological environment in particular on the load pathway soil - plant - animal - human. The chemical characterization of the radionuclide species is essential for a reliable assessment of the migration. Due to the relative simple structure of mono-cellular green algal cells and their properties to bind high amounts of heavy metals and actinides they are used as model organisms for the investigations of different biosorption and bioaccumulation processes.
Sorption studies with Chlorella vulgaris cells have shown that up to 40 % of the initial uranium is bound by the algal cells at pH 3. The uranium removal is almost complete at pH 5 and 6 in our experiments. The use of the time-resolved laser-induced fluorescence spectroscopy (TRLFS) and X-ray absorption spectroscopy (XAS) is an effort to obtain information about the possible structure and the spectroscopic properties of the sorbed U(VI) species on the algal cells in comparison to those of the initial uranyl species in the contact solution.
The luminescence spectroscopic investigations of formed algal uranyl complexes indicate that the binding of U(VI) to carboxyl groups plays a dominating role at pH 3, whereas a minor impact of organic phosphate compounds on the U(VI) sorption can not be excluded. In contrast, at pH 5 and 6 the phosphate groups are mainly responsible for the removal and binding of U(VI) by formation of organic and/or inorganic uranyl phosphates. The results of the uranium LIII-edge extended X-ray absorption fine structure (EXAFS) spectroscopic measurements support these evidence.
  • Contribution to proceedings
    NRC7 - 7th International Conference on Nuclear and Radiochemistry, 24.-29.08.2008, Budapest, Hungary
  • Lecture (Conference)
    NRC7 - 7th International Conference on Nuclear and Radiochemistry, 24.-29.08.2008, Budapest, Hungary

Publ.-Id: 10974 - Permalink


Einfluss der Oberflächeneigenschaften von Kohlenstoffnanotubes auf ihr Verhalten in der Umwelt
Schierz, A.; Zaenker, H.; Bernhard, G.;
Kohlenstoffnanotubes (CNTs) weisen einzigartige mechanische, elektronische und chemische Eigenschaften auf. Mit dem zunehmendem Einsatz dieser Materialien in Industrie- und Konsumgütern kann, realistisch betrachtet, ein unbeabsichtigter Eintrag in die Umwelt nicht ausgeschlossen werden. Bislang veröffentlichte Studien zum Verhalten und zum Lebenszyklus von CNTs in der Umwelt sind unzureichend.
Im Rahmen der Arbeit wird der Zusammenhang zwischen Oberflächeneigenschaften, Suspensionsstabilität und Sorptionseigenschaften von CNTs diskutiert, um Vorhersagen über das Verhalten dieser Materialien nach einer unbeabsichtigten Freisetzung in die Umwelt zu treffen.
  • Contribution to proceedings
    2. Symposium "Nanotechnology and Toxocology in Environment and Health, 02.-03.04.07, Leipzig, Deutschland

Publ.-Id: 10973 - Permalink


Microscopic and spectroscopic investigation of the U(VI) interaction with monocellular green algae
Vogel, M.; Günther, A.; Raff, J.; Bernhard, G.;
The green alga Chlorella vulgaris has the ability to bind high amounts of uranium(VI) in the pH range from 3 to 6 and to a lesser extend at higher pH values. The uranium removal is almost complete at pH 4.4 and 6 by metabolic active and inactive cells under the given experimental conditions. Laser-induced fluorescence spectroscopy was used for the characterization of uranyl species formed in solutions and biomass. Fluorescence spectroscopic investigations indicate differences of the formed algal uranyl complexes in dependence of the metabolic activity of cells and the uranyl speciation. Scanning electron microscopy demonstrates that the algal cell wall is involved in the binding of U(VI).
  • Lecture (Conference)
    5th International Conference Uranium Mining Hydrogeology (UMH V), 14.-18.09.2008, Freiberg, Germany
  • Contribution to external collection
    Broder J. Merkel, Andrea Hasche-Berger: Uranium, Mining and Hydrogeology, Berlin: Springer Verlag, 2008, 978-3-540-87745-5, 693-702

Publ.-Id: 10972 - Permalink


Complexation of Curium(III) and Europium(III) with Urea
Heller, A.; Barkleit, A.; Bernhard, G.;
To understand the toxicity, transport, deposition and elimination of man-made radioactive elements in the human organism, it is crucial to elucidate their chemical behavior and properties on a molecular level. The present work is part of a project to determine the speciation of curium(III) and its lanthanide analog europium(III) in human urine in order to identify potential decontamination agents, to discover possible metabolism pathways in the organism and to detect differences and similarities in the chemistry of trivalent lanthanides and actinides. The aim of this work was to investigate the complexation of curium(III) and europium(III) with urea, the main component of mammal urine. Since both elements exhibit unique luminescence properties, the complexation was studied by time-resolved laser-induced fluorescence spectroscopy with an excitation wavelength of 395 nm. The europium(III) and curium(III) concentration was 3x10-5 M and 3x10-7¬ M, respectively, in all series. The urea concentration was varied between 0.001 and 5 M, the pH ranged from 1 to 8. All measurements were carried out in a glove box under nitrogen atmosphere.

In aqueous solution the luminescence spectrum of europium(III) shows two typical peaks at 585-595 and 610-620 nm, respectively. Each of these peaks is slightly split, the first one into two peaks with emission maxima at 588 and 591nm, respectively, the second one into two peaks with luminescence maxima at 612 and 616 nm, respectively. Upon complexation with urea the position of all peaks remains unaltered but the ratio of the split peaks in the 610-620 nm range changes. Furthermore luminescence in this wavelength range is significantly increased by complexation. The lifetime of the europium(III)-aqua-ion was determined to be 110 µs. In contrast the complex exhibits a considerably longer lifetime (> 120 µs). Analysis of the time-resolved spectra indicated the formation of a 1:1 complex. At an urea concentration of 1 M the complex is stable till pH 6 but starting at pH 7 the luminescence spectrum changes due to formation of europium(III) hydroxides. Using the factor analysis program SPECFIT the stability constant of the complex log ß110 was determined to be -0.08.

In contrast to europium(III), the luminescence spectrum of curium(III) in aqueous solution shows only one emission peak at 593 nm. Upon complexation with urea the peak is red-shifted to 598 nm and the luminescence intensity decreases. The lifetime of the curium(III)-aqua-ion was determined to be 68 µs but the lifetime of the complex is considerably longer (> 75 µs). Analysis of the time-resolved spectra indicated the formation of a 1:1 complex. At an urea concentration of 1.5 M the complex is already formed at pH 1 and till pH 5 the luminescence spectra are identical. Starting at pH 6 the luminescence intensity decreases significantly due to the formation of curium(III) hydroxides. Using the factor analysis program SPECFIT the single spectra of the different species were calculated and the stability constant of the complex log ß110 was determined to be between -0.8 and -0.9.

Comparing the complexation of urea with europium(III) and curium(III), it seems that the latter is complexed inferior to the first one although it is obvious that both form very weak complexes. This can be explained with the structure of urea in aqueous solution over the whole pH range investigated in this study. The results obtained indicate that urea unlikely plays a role in heavy metal binding in urine and that other substances will have greater complexing potential.
Keywords: europium(III), curium(III), complexation
  • Poster
    Seventh International Conference on Nuclear and Radiochemistry, 24.-29.08.2008, Budapest, Hungary

Publ.-Id: 10971 - Permalink


Helical magnetorotational instability in a liquid metal experiment with reduced Ekman pumping
Stefani, F.; Gerbeth, G.; Gundrum, T.; Szklarski, J.; Rüdiger, G.; Hollerbach, R.;
The magnetorotational instability (MRI) is one of the most promising candidates to explain turbulence and angular momentum transport in accretion disks which is essential to understand the mass accumulation of stars and black holes. Only recently, a possible connection of MRI with the dynamo process in the Earth's core was discussed. We study a special type of MRI in a Taylor-Couette experiment with the liquid metal alloy GaInSn under the influence of a helical magnetic field (Phys. Rev. Lett. 97, 184502; Astrophys. J. 649, L145-L147; New J. Phys. 9, 295). This helical MRI sets in at Reynolds numbers of the order 1000 and Hartmann numbers of the order 10, quite in contrast to the standard MRI with an purely axial magnetic field which would require much larger values. Particular focus is laid on recent results of a modified experiment with strongly reduced Ekman pumping at the endplates in which sharper transitions between stable and unstable regimes are observed.
  • Open Access LogoAbstract in refereed journal
    Geophysical Research Abstracts 10(2008), 01989

Publ.-Id: 10969 - Permalink


Stochastic resonance in a noise triggered relaxation oscillation model of Earth's magnetic field reversals
Stefani, F.; Fischer, M.; Gerbeth, G.; Günther, U.; Sorriso-Valvo, L.;
One of the most interesting features of Earth's magnetic field reversals is their pronounced asymmetry, including a slow dipole decay and a fast recreation of the reversed dipole. This asymmetry indicates a possible connection with relaxation oscillations as they were early studied by van der Pol. A simple mean-field dynamo model (Phys. Rev. Lett. 94 (2005), 184506) is analysed with view on this similarity, and a comparison of the time series and the phase space trajectories with those of paleomagnetic measurements is carried out. For the case of highly supercritical dynamos a very good agreement with the paleomagnetic data is achieved (Earth Planet. Sci. Lett. 143 (2006), 828; Geophys. Astrophys. Fluid Dyn. 101 (2007), 227). Deviations of both numerical and paleomagnetic reversal sequences from Poisson statistics are touched upon (Phys. Earth Planet. Inter. 164 (2007), 197). The observed clustering property of reversals is interpreted as a feature of ''punctuated equilibrium'' which is, in turn, typical for metastable systems. We show that both metastability and the relaxation oscillation character have their common root in the typical spectral behaviour of the non-selfadjoint dynamo operator. In addition, we try to constrain the most essential parameters of the dynamo model by the typical time scale of individual reversals, the clustering characteristics, and the stochastic resonance phenomenon (arxiv.org/0709.3932). The latter was recently shown to appear with a time period typical for the Milankovitch cycle of the Earth's orbit eccentricity.
  • Open Access LogoAbstract in refereed journal
    Geophysical Research Abstracts 10(2008), 02003

Publ.-Id: 10968 - Permalink


Optical contrast in ion-implanted amorphous silicon carbide nanostructures
Takahashi, S.; Dawson, P.; Zayats, A. V.; Bischoff, L.; Angelov, O.; Dimova-Malinovska, D.; Tsvetkova, T.; Townsend, P. D.;
Topographic and optical contrasts formed by Ga+ ion irradiation of thin films of amorphous silicon carbide have been investigated with scanning near-field optical microscopy. The influence of ion-irradiation dose has been studied in a pattern of sub-micrometre stripes. While the film thickness decreases monotonically with ion dose, the optical contrast rapidly increases to a maximum value and then decreases gradually. The results are discussed in terms of the competition between the effects of ion implantation and surface milling by the ion beam. The observed effects are important for uses of amorphous silicon carbide thin films as permanent archives in optical data storage applications.
Keywords: amorphous silicon carbide; Ga+ ion irradiation; SNOM; optical data storage application.
  • Journal of Physics D: Applied Physics 40(2007)23, 7492-7496

Publ.-Id: 10967 - Permalink


Thermodynamical Data of uranyl carbonate complexes from Absorption Spectroscopy
Götz, C.; Geipel, G.; Bernhard, G.;
Aqueous uranyl carbonate complexes play an important role in the hydrogeology of uranium mining areas and nuclear waste disposals. Many publications are available for the stability of uranyl carbonate complexes, but thermodynamical data like the enthalpy or entropy are rare. We determined thermodynamical data from spectroscopic studies for the uranyl carbonate complex UO2(CO3)34- in the temperature range from 5°C to 70°C. We found for the reaction enthalpy the value 36.25 ± 4.31 kJ/mol and for the reaction entropy a value of 297.082 ± 13.839 J/(K∙mol).
Keywords: Uranyl, Carbonates, uranylcarbonate, thermodynamics, equilibrium constant
  • Poster
    5th International Conference Uranium Mining and Hydrogeology (UMH V), 14.-18.09.2008, Freiberg, Germany
  • Contribution to external collection
    Broder J. Merkel, Andrea Hasche-Berger: Uranium, Mining and Hydrogeology, Berlin: Springer Verlag, 2008, 978-3-540-87745-5, 907-914

Publ.-Id: 10966 - Permalink


P0607-Verfahren zum Bestimmen einer Materialzusammensetzung einer Materialprobe
Kraft, G.; Enghardt, W.; Würschig, T.;
Verfahren zum Bestimmen der Materialzusammensetzung einer Strahlung abstrahlenden Materialprobe (12) mit den folgenden Verfahrensschritten: Aufnehmen (P2) eines Spektrums der in einem Detektormaterial durch die Strahlung deponierten Energie; Bestimmen einer in einem ersten Energiebereich deponierten ersten Energie (F1), einer in einem zweiten Energiebereich deponierten zweiten Energie (F2) und einer in einem dritten Energiebereich deponierten dritten Energie (F3); Zuordnen (P4) eines ersten Farbparameters (F1) zu der ersten deponierten Energie, eines zweiten Farbparameters (F2) zu der zweiten deponierten Energie und eines dritten Farbparameters (F3) zu der dritten deponierten Energie und Vergleichen (P5) der zugeordneten Farbparameter (F1, F2, F3) mit vorgegebenen Werten für die Farbparameter (R1, R2, R3), wobei die vorgegebenen Werte (R1, R2, R3) typischen Farbparametern einer vorbestimmten Materialzusammensetzung entsprechen.
  • Patent
    DE 10 2006 033 662 A1 - 24 Jan. 2008

Publ.-Id: 10965 - Permalink


Detektoranordung zur winkelauflösenden Detektion von Strahlung und Verfahren zum Betrieb desselben
Kraft, G.; Enghardt, W.; Würsching, T.;
Detektoranordnung (1) zur winkelauflösenden Detektion von Strahlung mit mindestens einem Detektorelement (2), welches eine Vorderseite (3) und eine Rückseite (4), ein erstes Detektormaterial und ein zweites Detektormaterial zwischen der Vorderseite (3) und der Rückseite (4) aufweist, wobei ein Raum zwischen der Vorderseite (3) und der Rückseite (4) des Detektorelementes (2) von mehreren Bereichen (6) aus dem ersten Detektormaterial und mindestens einem Bereich (5) aus dem zweiten Detektormaterial ausgefüllt ist und jeder Bereich die Vorderseite (3) mit der Rückseite (4) des Detektorelementes (2) verbindet und wobei eine Kollimation von durch die Vorderseite (3) in das Detektorelement (2) eintretender Strahlung (γ) durch die Detektormaterialien erfolgt.
  • Patent
    DE 10 2006 033 661 A1 - 24 Jan. 2008

Publ.-Id: 10964 - Permalink


Complexation of Uranium(VI) by Sulfur and Nitrogen Containing Model Ligands in Aqueous Solution
Joseph, C.; Raditzky, B.; Schmeide, K.; Geipel, G.; Bernhard, G.;
The long-term safety assessment of nuclear waste disposals requires detailed knowledge of the transport and interaction behavior of actinides within the technical, geotechnical and geological barriers. Humic substances, ubiquitous in natural environments, are able to influence the migration of actinides due to their ability for complex and colloid formation and their redox properties. It is known, that especially their carboxylic and phenolic OH groups are able to complex metal ions. In addition to these oxygen containing functional groups, humic substances also offer sulfur and nitrogen containing functionalities.
The aim of this work is to determine the influence of various sulfur and nitrogen containing functional groups on the uranium(VI) complexation and to evaluate their contribution in comparison to oxygen containing functional groups. For this, simple organic model ligands that can occur as building blocks for humic substances are used in the first instance with the objective to transfer the results to humic substances.
In this study, results are presented for the uranium(VI) complexation by the organic ligands benzenesulfonic and 4-hydroxybenzenesulfonic acid as well as for nicotinic and anthranilic acid. The complex formation constants for the uranium(VI) complexation were determined applying UV-vis absorption spectroscopy and time-resolved laser-induced fluorescence spectroscopy (TRLFS) as a function of pH.
Interestingly, we did not see any interaction of the uranyl ion with benzenesulfonic acid (BSA). In contrast, for the uranium(VI) complexation by 4-hydroxybenzenesulfonic acid (HBSA) the formation of a 1:1 complex was detected. The stability constant for this complex of the type MpHqLr was determined with log ß101 = 3.9 ± 0.03.
Keywords: Uranium, complexation, benzenesulfonic acid, 4-hydroxybenzenesulfonic acid, nicotinic acid, anthranilic acid
  • Poster
    5th International Conference Uranium Mining Hydrogeology (UMH V), 14.-18.09.2008, Freiberg, Germany
  • Contribution to external collection
    Broder J. Merkel, Andrea Hasche-Berger: Uranium, Mining and Hydrogeology, Berlin: Springer Verlag, 2008, 978-3-540-87745-5, 539-548

Publ.-Id: 10963 - Permalink


Interaction of uranium(VI) with peptidoglycan
Barkleit, A.; Moll, H.; Bernhard, G.;
Bacteria have a great influence on the migration behaviour of heavy metals in the environment. Peptidoglycan (PGN) forms the main part of the outer membrane of Gram-positive bacteria. We investigated the interaction of the uranyl cation (UO22+) with PGN from Bacillus subtilis by using potentiometric titration and time-resolved laser-induced fluorescence spectroscopy (TRLFS) over a wide pH range (2.4 – 9) and at environmentally relevant low uranium concentrations (10-4 – 10-5 M). The PGN polymer contains a high density of functional groups for metal ion binding, like carboxyl, amino and hydroxyl groups.
With potentiometric titration the dissociation constants of the functional groups and the corresponding site densities could be detected. We found four functional groups, which can be dedicated to two different carboxyl functionalities, amino and hydroxyl groups. Using the same technique, two different uranyl PGN complexes could be identified, one complex with a carboxyl ligand (R-COO-UO2+) and a second complex with additional hydroxyl coordination (R-COO-UO2+-HO-R). The complex stability constants were determined to be log beta = 5.16 ± 0.13 for the first, and log beta = 13.00 ± 0.05 for the second complex, respectively.
TRLFS measurements show from pH 2.4 to 4.5 a red shift of the peak maxima of about 8 – 10 nm, in comparison to the free uranyl ion, connected with an increase of the luminescence intensity. Over pH 4.5 up to pH 9 the luminescence intensity decreases. The time resolved measurements show beneath the lifetimes of the free uranyl ion (1800 ± 200 ns) and the known uranyl hydroxides only one additional lifetime (224 ± 54 ns) which can be dedicated to a uranyl PGN complex species. From these we conclude that the two uranyl PGN complex species found by potentiometry can also be identified with TRLFS. The first complex (R-COO-UO2+) shows luminescence activity, but the second complex (R-COO-UO2+-HO-R) not. Complex stability constants for these two complexes were determined using the computer program SPECFIT. They are in good accordance to those calculated from potentiometric titrations.
  • Lecture (Conference)
    7th International Conference on Nuclear and Radiochemistry (NRC7), 24.-29.08.2008, Budapest, Hungary

Publ.-Id: 10962 - Permalink


On the three-dimensional character of the magnetohydrodynamic effect during metal electrodeposition in cuboid cells
Mutschke, G.; Bund, A.;
The influence of external homogeneous magnetic fields during electrochemical metal deposition in cuboid cells is shortly reviewed. By analytical means, supported by numerical simulations, it is shown that a simplified two-dimensional approach is often misleading and has to be replaced by a more complex three-dimensional treatment as only the solenoidal part of the Lorentz force can cause convection.
Keywords: Magnetoelectrochemistry, electrochemistry, Lorentz force, metal deposition, limiting current, numerical simulation

Publ.-Id: 10961 - Permalink


Temperature-Jump-Induced Structural Transition in DNA Monitored by Rapid Scan FTIR-Difference-Spectroscopy
Fahmy, K.; Savchuk, O.; Khesbak, H.;
Conformational substates of B-DNA have been reported to be involved in DNA recognition by proteins [1]. BI and BII substates, that co-exist in B-DNA, differ in the phosphate backbone conformation about the C3'-O3'-P segment related to the variability of the dihedral e and z angles (see figure left [2]). Typical IR marker bands have previously been identified which allow assessing the relative population of BI and BII conformers by FTIR spectroscopy for DNA from salmon testes, poly(dG-dC) and the d(CGCGAATTCGCG)2 dodecamer [3]. So far, BI/BII dynamics studies were restricted to static FTIR spectroscopy under isothermal relaxation at low temperatures . We have attempted to monitor the BI/BII transition under defined native-like conditions using rapid scan FTIR-difference-spectroscopy at a time resolution of 70 ms. An ATR-cell accessory was designed that allows both, the application of flashes to induce small temperature jumps and the adjustment of constant humidity of the sample. The latter is critical to address the role of backbone hydration in the dynamics of the BI/BII transition.
  • Poster
    XIIth European Conference on the Spectroscopy of Biological Molecules, 01.-06.09.2007, Bobigny, France

Publ.-Id: 10960 - Permalink


Flavor Diagonal and Off-Diagonal Susceptibilities in a Quasiparticle Model of the Quark-Gluon Plasma
Bluhm, M.; Kämpfer, B.;
The Taylor coefficients of flavor diagonal and off-diagonal susceptibilities as well as baryon number, isovector and electric charge susceptibilities are considered within a phenomenological quasiparticle model of the quark-gluon plasma and successfully compared with lattice QCD data for two degenerate quark flavors. These susceptibility coefficients represent sensible probes of baryon density effects in the equation of state. The baryon charge is carried, in our model, by quark-quasiparticle excitations for hard momenta.
Keywords: quark-gluon plasma, susceptibility, quasiparticle model

Publ.-Id: 10959 - Permalink


D(E)RY Motif- A Conserved Proton Dependent Modular Switch In Class-1 GPCRs
Madathi, S.; Fahmy, K.;
Activation of G protein-coupled receptors (GPCRs) orginates in ligand-induced structural changes that are transmitted across the plasma membrane to the cytosolic receptor surface. In rhodopsin-like class-1GPCRs, protonation of a carboxylic acid (Glu134 in rhodopsin) in the conserved cytosolic D(E)RY motif in transmembrane helix 3 (TM3) is coupled to receptor activation. Here, we have investigated the proton-sensitivity of the structure of synthetic peptides consisting of 30amino acids derived from TM3 of bovine rhodopsin (rho) and the chemokine receptor CCR3. ATR- Fourier-transform-infrared (FTIR) spectroscopy reveals a helical structure of the rho-TM3 peptide in PC vesicles and detergent micelles, where Glu134 exchanges protons with the solvent at a pKa of 5.5-6.0 as determined from the pH sensitivity of the COO- stretching mode. The amide I modes reveal a proton-induced helical turn formation in rho-TM3 and CCR3-TM3. The conformational change in the ERY motif is affects also the Tyr136 fluorescence which exhibits a strong pH sensitivity (pKa of 6) which is abolished upon replacement of Glu134 by Gln in rho-TM3. Förster-Resonance-Energy-transfer from a C-terminal Trp to DANSYL-labelled lipids in mixed micelles and lipid vesicles evidences that the D(E)RY motif constitutes an autonomous proton-driven conformational switch which couples protonation to helical turn formation and probably helix insertion depth. We propose that the protonation-controlled hydrophobicity profile at the cytosolic end of TM3 provides a pH-sensitive module that couples helix packing in the active receptor conformation of class I GPCRs to proton exchange reactions with the cytosol.
  • Poster
    FEBS Workshop The Biology of Modular Protein Domains, 08.-13.09.2007, Seefeld in Tirol, Austria

Publ.-Id: 10958 - Permalink


Curium(III) Speciation in Aqueous Solutions of Bacterial Siderophores
Moll, H.; Glorius, M.; Bernhard, G.;
Actinides have been and will be introduced into shallow and deep groundwater environments via various human activities. The process of interaction between naturally occurring chelating substances and metals may influence the migration behavior of hazardous actinides in the environment once they have been released. Siderophores are chelating substances produced by microorganisms under iron-deficient conditions. For example, Powell et al. [1] demonstrated the occurrence of hydroxamate siderophores produced by microorganisms in concentrations ranging from 10-7 to 10-8 M in a variety of soils. In general catechol and hydroxamate groups in siderophores are the main functional groups involved in binding with actinides. As an example, Pseudomonas species are ubiquitous soil and groundwater bacteria that synthesize bacterial pyoverdin-type [2-5] and hydroxamate siderophores [6]. The observed mobilization effects of siderophore molecules on radionuclides probably due to the formation of strong soluble species motivated detailed investigation of their complexation characteristics, using a radionuclide suitable for spectroscopic methods.
To overcome the lack of information about actinide(III) siderophore interactions, we thus present findings regarding the complexation of curium(III) with pyoverdins (PYO) and desferrioxamine B (DFO), obtained using time-resolved laser-induced fluorescence spectroscopy (TRLFS). The excellent luminescence properties of curium(III) were used to explore its complexation behavior with the two different bioligands at environmentally relevant curium(III) concentrations.
(A) PYO: Pseudomonas fluorescens (CCUG 32456) cells isolated from the granitic rock aquifers at the Äspö Hard Rock Laboratory (Äspö HRL), Sweden, secreted a pyoverdin mixture containing 4 main components [5].
(B) DFO: Desferrioxamine B (DFO) is a microbial produced trihydroxamate siderophore which is commercially available and could occur naturally in soils. Recently Essen et al. [6] could show the production of desferrioxamine siderophors by Pseudomonas stutzeri (CCUG 36651). This strain was also isolated at the Äspö Hard Rock Laboratory.

We explored the unknown luminescence properties, lifetimes and individual luminescence emission spectra of the formed Cm(III) species. The strength of the complex formation of the two bioligands will be discussed on the basis of the spectroscopic properties obtained in their individual systems. The results of this study increase our understanding of the mobilization of actinides by siderophores secreted by resident bacteria in a natural environment.

[1] Powell, P.E., et al., Nature 287 (1980) 833-834.
[2] Budzikiewicz H., Fortschr. Chem. Org. Naturst. 87 (2004) 83-237 .
[3] Kalinowski B.E., et al., Geomicrobiol. J. 23 (2006) 157-164.
[4] Moll, H., et al., BioMetals 21 (2008) 219-228.
[5] Moll, H., et al., Geomicrobiol. J. 25 (2008) 157-166.
[6] Essen, S.A., et al., Appl. Environ. Microbiol. 73 (2007) 5857-5864.
Keywords: Curium; Pyoverdin; Desferrioxamine B; Fluorescence spectroscopy; TRLFS; Complexation
  • Contribution to proceedings
    7th International Conference on Nuclear and Radiochemistry (NRC7), 24.-29.08.2008, Budapest, Hungary
  • Poster
    7th International Conference on Nuclear and Radiochemistry (NRC7), 24.-29.08.2008, Budapest, Hungary

Publ.-Id: 10957 - Permalink


Results of a 20 minutes decay measurement of a patient irradiation by the in-beam PET scanner
Fiedler, F.; Parodi, K.; Pawelke, J.; Pönisch, F.; Priegnitz, M.; Shakirin, G.; Enghardt, W.; Möckel, D.;
no abstract available
Keywords: in-beam PET
  • Open Access LogoContribution to external collection
    in: GSI Jahresbericht, Darmstadt: GSI, 2008

Publ.-Id: 10956 - Permalink


Alpha-irradiation effects in SiO2
Krickl, R.; Nasdala, L.; Götze, J.; Grambole, D.; Wirth, R.;
Natural and synthetic crystalline α-quartz, as well as synthetic SiO2 glass, were irradiated with different doses of 8.8 MeV He2+ ions. The irradiation-induced alteration was characterised using Raman and cathodoluminescence (CL) spectroscopy, optical microscopy, transmission electron microscopy (TEM) and CL and electron microscope imaging. The initially dull bluishviolet CL colour of the two α-quartz samples was found to be transformed to bright yellow in the irradiated areas. The emission maximum was observed 45 μm below the surface, which corresponds well with correlated helium trajectory lengths and defect density distribution. Both, total intensity and radial intensity distribution of the CL emission change with the irradiation dose. Observations suggest a nonlinear, approximately logarithmic increase of the CL intensity depending on the alpha dose. Significant broadening of Raman bands is only observed near the far end of helium trajectories. This broadening is not only caused by the structural radiation damage but also by strain between strongly and lowly damaged areas.
Keywords: Alpha-quartz, radiohalo, cathodoluminescence, Raman spectroscopy, He implantation, irradiation, radiation damage, transmission electron microscopy

Publ.-Id: 10955 - Permalink


Effects of alpha-irradiation on SiO2 phases
Krickl, R.; Grambole, D.; Götze, J.; Wirth, R.; Nasdala, L.;
Aureoles surrounding radioactive inclusions – so called radiohaloes – are a common feature often observed in several rock-forming minerals. These alterations are caused by the action of alpha-particles (i.e. He2+ ions) emitted into the host mineral.
While in some cases (e.g. biotite, cordierite) the most striking feature of radiohaloes is a strongly enhanced absorption of light, there are commonly no visible changes found in quartz. In this mineral, alpha irradiation leads to a marked change in the emission behaviour, which can be very well observed using cathodoluminescence (CL) imaging.
In the present study several micro- and nano-techniques [i.e., Raman spectroscopy, CL spectroscopy, and transmission electron microscopy (TEM)] were used to study the alteration in synthetic radiohaloes, produced by artificial alpha irradiation of various SiO2 samples. Alpha-quartz of natural and synthetic origin as well as synthetic SiO2 glass were implanted with different doses of 8.8 MeV He2+ ions (fluences in the range from 1013 to 1017 ions/cm²).
The initially dull bluish-violet CL colour of the crystalline quartz samples was found to be transformed to bright yellow in irradiated areas. Monte Carlo simulations predicted that the observed depth of alteration is in very good agreement with the calculated range of alpha particles in quartz. Both, total intensity and radial intensity distribution of the CL emission change with the irradiation dose. Observations suggest a non-linear, approximately logarithmic increase of the CL intensity depending on the alpha dose. In contrast, no significant change in CL emission was observed in the case of He-irradiated amorphous SiO2.
The changed emission behaviour of He-irradiated areas in alpha-quartz is accompanied by structural damage, caused by the impact of the alpha particles. Significant broadening of Raman bands is only observed near the far end of helium trajectories. This broadening is not only caused by the structural radiation damage but also by strain, inter alia due to (locally heterogeneous) volume expansion of irradiated micro-areas.
Restricted to the end of the helium trajectories, there is a clearly defined, lense-shaped zone, characterised by changed optical and BSE behaviour. The structural state of this region, as investigated by TEM, will be discussed.
  • Lecture (Conference)
    European Geosciences Union General Assembly, 13.-18.04.2008, Vienna, Austria
  • Contribution to proceedings
    European Geosciences Union General Assembly, 13.-18.04.2008, Vienna, Austria
    Geophysical Research Abstracts, EGU2008-A-09731, 10

Publ.-Id: 10954 - Permalink


Component Additivity Approach for Uranium Retardation in Sandstone Host Rocks
Richter, A.; Nebelung, C.; Brendler, V.;
Sandstone is one of the most important host rocks for uranium ore deposits, e.g. in Germany (Königstein) or the Czech Republic (Pribram). Any remediation efforts of respective mining legacies thus require a detailed understanding of this system. Namely the sorption in this complex rock is not well enough investigated yet.
One widely accepted approach (Component Additivity – CA, cf. [1]) to describe the sorption is based on the assumption that the surface of a complex mineral assemblage is composed of a mixture of one or more phases whose surface properties are known from independent studies. An internally consistent SCM database can be developed that describes the adsorption reactions of solutes to each phase. The fitting of data of the complex system is not necessary.
We predicted the sorption of uranium(VI) on sandstone using the results of the surface characterization of the assemblage and published data for adsorption onto the pure mineral constituents. The results were compared with batch sorption experiments using natural and synthetic sandstone (mixture of the main components quartz, muscovite, and hematite).
The sorption of U(VI) on natural and two synthetic sandstone (I and II) was investigated in batch sorption experiments (air atmosphere, 0.1M NaClO4, pH 3-11, [U(VI)] 10-9-10-3M). We had to consider the natural uranium concentration dissolved from the sandstone at low concentrations.
The synthetic sandstone was a mixture of quartz with muscovite and hematite. The surface area (N2-BET) of quartz was 0.047 m2/g, of muscovite 0.88 m2/g, of hematite 0.89 m2/g and of natural sandstone (mainly quartz) 0.69 m2/g.
The pH dependence shows a maximal sorption between pH 6 and 7. The U(VI) sorption varies between 95% (10-9M) and 7% (10-4) on natural sandstone, and between 80% (10-9M) and 2% (10-4M) on synthetic sandstone.
The modeling of U(VI) sorption on sandstone was performed using the CA approach. We assumed just one type of surface sites and applied a model with simple electrostatics, the Diffuse Double Layer Model (DDLM). For the modeling the code MINTEQA2 (Version 4.03, US EPA, May 2006) was used. The aqueous species were taken from the NEA-TDB [2].
As surface reactions we considered the protolysis of quartz, hematite, muscovite, the U(VI) surface complexes of quartz, hematite, muscovite (monomer, dimer) and the ternary U(VI) surface complexes of quartz and hematite with carbonate. The surface area was considered according to the mineral fraction. Despite of a slight shift of the predicted curve to lower pH in both systems, a good accordance with experimental values were found. Obviously, the sorption is strongly influenced by the small amount (0.5%) of hematite.
For the sorption behavior at varying U(VI) initial concentration, a precipitation of schoepite was predicted. As schoepite is an aged mineral, it is unlikely to be formed within the experimental duration of five days. A subsequent exclusion from the list of allowed phases led to a predicted precipitation of both soddyite and metaschoepite.
[1] Davis, J.A. et al. (1998) Application of the surface complexation concept to complex mineral assemblages. Environ. Sci. Technol. 32, 2820-2828.
[2] Guillaumont, R. et al. (2003) Update on the chemical thermodynamics of U, Np, Pu, Am, Tc. Elsevier, Amsterdam.
Keywords: Component Additivity Approach Sorption Surface Complexation Uranium MINTEQA2
  • Lecture (Conference)
    XVII International Conference on Computational Methods in Water Resources (CMWR 2008), 06.-10.07.2008, San Francisco, USA
  • Contribution to proceedings
    XVII International Conference on Computational Methods in Water Resources (CMWR 2008), 06.-10.07.2008, San Francisco, USA
    Proceedings of Computational Methods in Water Resources

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Publ.-Id: 10953 - Permalink


Diode-pumped lasers for ultra-high peak power
Siebold, M.; Hein, J.; Hornung, M.; Podleska, S.; Kaluza, M. C.; Bock, S.; Sauerbrey, R.;
The generation of the highest laser peak intensities at a high degree of system compactness can be achieved by combining modern diode-pump technologies with the chirped pulse amplification technique. In principle, the spectroscopic properties of the gain medium determine the scaling laws of both high output pulse energy and short pulse duration. Here we introduce a novel criterion classifying laser materials with respect to their ability to generate pulses of highest peak power in a diode-pumped solid state laser system. Furthermore, amplified spontaneous emission as well as laser damage issues affecting the efficiency and compactness of a laser amplifier system are discussed.

Publ.-Id: 10952 - Permalink


Broad-band regenerative laser amplification in ytterbium-doped calcium fluoride (Yb:CaF2)
Siebold, M.; Hornung, M.; Bock, S.; Hein, J.; Kaluza, M. C.; Wemans, J.; Uecker, R.;
An output pulse energy of 17.3 mJ has been achieved with a diodepumped Yb:CaF2) regenerative laser amplifier. The bandwidth of the output pulse spectrum was 7.3 nm, being seeded with femtosecond pulses stretched to 2.2 ns. In cw operation a tuning range of 80 nm has been observed. A maximum pulse energy of 44mJ at a repetition rate of 1 Hz has been obtained in Q-switched mode. The laser damage threshold of a Yb:CaF2) crystal has been determined at a wavelength of 1064 nm and a pulse duration of 10 ns.

Publ.-Id: 10951 - Permalink


Flow structure and concentration distribution measurements in seemingly parallel magnetic and electric fields
Cierpka, C.; Weier, T.; Mutschke, G.; Eckert, K.; Uhlemann, M.; Bund, A.;
Characterized by the interplay of Lorentz forces, flow and concentration distributions, magnetoelectrochemical processes are typically quite complex. We aim to show that flow field and concentration measurements by means of Particle Image Velocimetry (PIV) and the relatively new technique Background Oriented Schlieren (BOS) are a valuable aid in understanding the observed phenomena. Two examples, the flow field in a cylindrical cell and the concentration distribution near a circular millielectrode, will be discussed in detail.
Keywords: Background Oriented Schlieren, Particle Image Velocimetry, Electrochemistry, Flow Control
  • Lecture (Conference)
    213th ECS Meeting, 18.-23.05.2008, Phoenix, USA

Publ.-Id: 10950 - Permalink


Hydrogen incorporation in ultrananocrystalline diamond/amorphous carbon films
Kulisch, W.; Sasaki, T.; Rossi, F.; Popov, C.; Sippel, C.; Grambole, D.;
The incorporation of hydrogen within ultrananocrystalline diamond/amorphous carbon composite films has been investigated by nuclear reaction analysis (NRA) and Fourier transform infrared spectroscopy (FTIR). The film bulk contains ca. 7.5-8 % H (for a deposition temperature of 600°C), while the H concentration in the surface region is considerably higher. FTIR measurements show that the hydrogen-rich surface is formed right at the beginning of the deposition process and grows outward as the film thickness increases. It can thus be concluded that surface hydrogen species play an active role in the formation of ultrananocrystalline diamond/amorphous carbon films.

Publ.-Id: 10949 - Permalink


Yrast studies of 80,82 Se using deep-inelastic reactions
Jones, G. A.; Regan, P. H.; Podolyak, Z.; Yoshinaga, N.; Higashiyama, K.; de Angelis, G.; Zhang, Y. H.; Gadea, A.; Ur, C. A.; Axiotis, M.; Bazzacco, D.; Bucurescu, D.; Farnea, E.; Gelletly, W.; Ionescu-Bujor, M.; Iordachescu, A.; Kröll, T.; Langdown, S. D.; Lenzi, S.; Lunardi, S.; Marginean, N.; Martinez, T.; Medina, N. H.; Menegazzo, R.; Napoli, D. R.; Quintana, B.; Rubio, B.; Rusu, C.; Schwengner, R.; Tonev, D.; Valiente Dobon, J. J.; von Oertzen, W.;
We report the results of an experiment in which we studied the near-yrast states in selenium isotopes approaching N = 50 following their population in multinucleon transfer reactions between a 82Se beam and a 192Os target. The level schemes for 80,82Se derived from the current work are compared with restricted-basis shell-model calculations and pair-truncated shell-model calculations. These provide a good description of the yrast sequences in these nuclei using a basis space limited to excitations in the (p3/2 , p1/2 , g9/2 ) and (f5/2 , p3/2 , p1/2 ) orbitals.
Keywords: nuclear Structure, gamma-ray spectroscopy, deep-inelastic reactions, shell model.
  • Physical Review C 76(2007), 054317-1-054317-5

Publ.-Id: 10948 - Permalink


Evolution of ion-induced ripple patterns on SiO2 surfaces
Keller, A.; Facsko, S.; Möller, W.;
The evolution of nanoscale ripple patterns during sub-keV ion sputtering of thermally grown, fused, and single crystalline SiO2 surfaces has been investigated by means of atomic force microscopy. For all three materials, different dependencies of the ripple wavelength and the surface roughness on the ion fluence have been found. Within the Bradley-Harper model of pattern formation, the observed differences are consistent with different amounts of surface and near-surface mass transport by ion-enhanced viscous flow which might result from different surface energies of the SiO2 specimens.
  • Nuclear Instruments and Methods in Physics Research B 267(2009)4, 656-659
  • Lecture (Conference)
    17th International Workshop on Inelastic Ion-Surface Collisions, 21.-26.09.2008, Porquerolles, France

Publ.-Id: 10947 - Permalink


Influence of the Time of Flight Information on the Reconstruction of In-Beam PET Data
Shakirin, G.; Crespo, P.; Enghardt, W.;
At the heavy ion therapy facility at the Gesellschaft für Schwerionenforschung Darmstadt, Germany, an in-beam PET scanner is operated for quality assurance monitoring simultaneously to the therapeutic irradiation. The PET scanner, which is completely integrated into the treatment facility, registers the annihilation γ - rays following the decay of minor amounts of β+ radioactive nuclei produced via nuclear reactions between the ions of the therapeutic beam and the atomic nuclei of the irradiated tissue. From a comparison of the reconstructed activity distributions with those predicted from the treatment plan, deviations between the prescribed and the applied dose distributions can be detected. We investigate how reconstruction of in-beam PET data can profit from the time of flight (TOF) information taking into account specific issues of in-beam PET system, namely, a very low counting statistics and the dual head geometry of the PET scanner which results in missing ray sums in certain directions. We simulated β+-activity distributions based on real treatment plans and generated events measured with a timing resolution 1.2 ns FWHM. We further reconstructed the data via list mode MLEM algorithm and via randomly filled subsets expectation maximization (RFS-EM) algorithm (a modification of OSEM adapted for in-beam PET). Two irradiation situations were evaluated: a relatively small field in the head and neck region (clivus chondrosarcoma) and a large field in the pelvic region (prostate carcinoma). Root mean square error is reduced by 20 % for head and neck field and by 36 % for pelvic field for TOF included reconstructions. Also a significant reduction of specific reconstruction artifacts (in particular, elongation of the images caused by the dual head geometry of the scanner) is observed in TOF included reconstructions versus non-TOF ones for both irradiation cases.
Keywords: in-beam PET, reconstruction, time-of-flight, TOF, MLEM, OSEM
  • Contribution to external collection
    in: GSI Scientific Report 2007, Darmstadt: GSI, 2008

Publ.-Id: 10946 - Permalink


Zellschädigung nach Röntgenbestrahlung
Beyreuther, E.; Lessmann, E.; Pawelke, J.;
Zusammenfassung über die Arbeiten zur Bestimmung des RBW von weicher Röntgenstrahlung
  • Poster
    OncoRay, Strategie-Meeting, 08.-09.01.2008, Gröditz, Germany

Publ.-Id: 10945 - Permalink


In-beam PET monitoring of phantom irradiation with 7Li-ions
Priegnitz, M.; Möckel, D.; Parodi, K.; Fiedler, F.; Sommerer, F.; Enghardt, W.;
No abstract available.
  • Contribution to external collection
    in: GSI Scientific Report 2007, GSI Report 2008-1, Darmstadt: Gesellschaft für Schwerionenforschung mbH, 2008, 381

Publ.-Id: 10944 - Permalink


Uranium(VI) complexation with pyoverdins secreted by a subsurface strain of Pseudomonas fluorescens and Complexation of curium(III) with pyoverdin model compounds – salicylhydroxamic (SHA) and benzohydroxamic acid (BHA)
Moll, H.; Glorius, M.; Bernhard, G.;
The contributions of the Forschungszentrum Dresden-Rossendorf (FZD)/Institute of Radiochemistry (IRC) within the microbe project as part of the international co-operation of the Äspö HRL (Sweden) with the BMWi (Germany) are concentrated in a project addressing the indirect interaction mechanism of a mobilization of actinides by released bioligands in the aquifer system from relevant Äspö bacteria. The ongoing study is focused on: (i) isolation and characterization of microbial ligands produced from a subsurface strain of Pseudomonas fluorescens isolated at Äspö, (ii) interaction of U(VI), Np(V), and Cm(III) with the microbial ligands including compounds simulating the functionality of the microbial ligands and the surface of the bacteria and (iii) spectroscopic characterization of the formed actinide complexes/compounds. The formation constants determined will be used directly in speciation and transport models. This project should help to identify the dominating process of the interaction between actinides and microbes (direct or indirect ones). The research performed in our project improves the understanding of the behavior of colloids and microbes and their respective interaction with radionuclides.
The activities in 2007 were concentrated on (a) complexation studies of U(VI) with the secreted bioligand mixture of P. fluorescens found at Äspö HRL, (b) complexation studies of Cm(III) with relevant pyoverdin model compounds, and (c) complexation studies of U(VI) and Cm(III) with model molecules simulating the functionality of bacterial cell envelopes to explain the interactions of actinides in biologically systems on a molecular level. Selected results of the topics (a) and (b) will be reported here.
Keywords: uranyl, pyoverdins, UV-vis spectra, fs-TRLFS spectra, complexation, Cm(III); Complexation; TRLFS; Hydroxamic acids
  • Other report
    Stockholm: Äspö HRL Annual Report 2007, 2008
    8 Seiten

Publ.-Id: 10943 - Permalink


Measurement of the spatio-temporal distribution of harmonic and transient eddy currents in a liquid metal
Forbriger, J.; Galindo, V.; Gerbeth, G.; Stefani, F.;
Harmonic and transient eddy currents in the eutectic liquid metal alloy GaInSn positioned above an excitation coil are determined by measuring the corresponding voltage drop in an electric potential probe. The resulting spatio-temporal eddy current field is compared with the corresponding analytical expressions for a conducting half-space. Further, a deformation of the eddy current distribution due to a non-conducting torus immersed into the liquid metal is measured and compared with numerical results. The method can be generalized to arbitrary geometries, and might help to validate numerical models for non-destructive testing and magnetic inductance tomography.
Keywords: Eddy currents, Magnetic induction tomography, Nondestructive testing, Liquid metals
  • Measurement Science and Technology 19(2008)4, 045704

Publ.-Id: 10942 - Permalink


Density, viscosity and electrical conductivity of hypoeutectic Al-Cu liquid alloys
Plevachuk, Y.; Sklyarchuk, V.; Yakymovych, A.; Eckert, S.; Willers, B.; Eigenfeld, K.;
New workable aluminium-based light alloys are a key issue in current materials science. In this work, thermophysical properties (density, viscosity and electrical conductivity) of liquid Al96Cu4, Al80Cu20, Al70Cu30, and AlCu4TiMg (wt.%) alloys have been measured in a wide temperature range.
The anomalies with respect to the concentration dependence of the electrical conductivity are explained in terms of the s–d hybridization model. A comparison with data and scaling relations being available in the literature is given.
Keywords: Al-Cu alloys, density, viscosity, electrical conductivity
  • Metallurgical and Materials Transactions A 39(2008)12, 3040-3045

Publ.-Id: 10940 - Permalink


ERDA and Structural Characterization of Oriented Multiwalled Carbon Nanotubes
Gohier, A.; Point, S.; Djouadi, M. A.; Granier, A.; Minea, T. M.; Kreissig, U.; Abrasonis, G.; Kolitsch, A.; Möller, W.;
Oriented multiwalled carbon nanotubes have been synthesized by distributed electron cyclotron resonance plasma enhanced chemical vapor deposition. Elastic recoil detection analysis measurements on multiwalled carbon nanotubes are reported here for the first time. On the basis of the recorded depth profiles, we have developed a simple model to estimate the surface densities of as-grown nanotubes. Besides, nitrogen and hydrogen contents into MWNT, typically less than 6.5 and 8 atom %, respectively, have been characterized as a function of the chemical nature of the catalyst, the synthesis temperature, and the hydrogen carrying diluent gas. These results are discussed with respect to the structural characterization performed by electron energy loss spectroscopy measurements, transmission electron microscopy and X-ray photoelectron spectroscopy.
  • Journal of Physical Chemistry C 111(2008)28, 10353-10358

Publ.-Id: 10939 - Permalink


A new high-quality database for air-water flow in a DN200 vertical duct
Lucas, D.; Beyer, M.; Kussin, J.;
This presentation reports about a new experimental series on air-water upwards pipe flow. The generated database is suitable for investigations on bubble coalescence and fragmentation.
Keywords: two-phase flow, pipe flow
  • Lecture (others)
    Meeting of the German CFD Network for Nuclear Reactor Safety, 23.-24.01.2008, Grosshartpenning, Deutschland

Publ.-Id: 10938 - Permalink


Analyse von Borverdünnungstransienten in Druckwasserreaktoren
Kliem, S.;
Der Vortrag gibt eine Einführung in die Problematik der Borverdünnungstransienten in Druckwasserreaktoren. An einem konkreten Fall werden die Möglichkeiten gekoppelter neutronenkinetisch/thermohydraulischer Rechenprogramme, diese Art von Transienten zu berechnen, gezeigt.
  • Invited lecture (Conferences)
    Seminar für Energieverfahrenstechnik, 18.12.2007, Dresden, Germany

Publ.-Id: 10937 - Permalink


Experimente zu Zweiphasenströmungen an der Versuchsanlage TOPFLOW
Lucas, D.;
Im Vortrag wird ein Überblick zu den durchgeführten Experimenten an der TOPFLOW-Anlage sowie der Nutzung der gewonnen Daten für die CFD-Code-Entwicklung und -validierung gegeben.
Keywords: Zweiphasenströmung, CFD
  • Invited lecture (Conferences)
    Seminar für Energieverfahrenstechnik, 15.01.2008, Dresden, Germany

Publ.-Id: 10936 - Permalink


Linear stability of an alternating magnetic field driven flow in a spinning cylindrical container
Shatrov, V.; Gerbeth, G.; Hermann, R.;
We present a numerical analysis of the free surface liquid metal flow and its three-dimensional linear stability. The flow is driven by an alternating magnetic field in a spinning cylindrical container. The electromagnetic and hydrodynamic fields are fully coupled via the shape of the liquid free surface. The hydrodynamic equations are solved by a spectral collocation method, and the alternating magnetic field distribution is found by a boundary-integral method. The flow stability is analyzed for various magnetohydrodynamic interaction parameter and Ekman numbers assuming a flat free surface. We find that only a sufficiently fast spinning suppresses and stabilizes the flow, but a moderate spinning can significantly destabilize it.
  • Physical Review E 77(2008)4, 046307

Publ.-Id: 10935 - Permalink


Ferromagnetism of Fe implanted ZnO – a phenomenon related to defects?
Zhou, S.; Potzger, K.; Talut, G.; Reuther, H.; Kuepper, K.; Grenzer, J.; Xu, Q.; Helm, M.; Fassbender, J.ORC; Arenholz, E.
ZnO(0001) single crystals annealed in high vacuum have been investigated with respect to their magnetic properties. Annealing at mild temperatures up to 773 K leads to ferromagnetic properties without any transition metal doping. Fe ion implantation at low temperatures leads to similar results. However, no evidence for the relevance of the Fe magnetic moment for the generation of ferromagnetism was observed. Nevertheless, the degradation of the magnetization with time is much less pronounced for the implanted crystals with respect to the purely annealed samples.
Keywords: ZnO, Diluted Magnetic Semiconductors, ion implantation
  • Journal of Physics D: Applied Physics 41(2008), 105011

Publ.-Id: 10934 - Permalink


Curium(III) complexation with desferrioxamine B (DFO) investigated using fluorescence spectroscopy
Moll, H.; Glorius, M.; Bernhard, G.;
Hydroxamate-type siderophores like desferrioxamine B (DFO) are the most common siderophores ubiquitously found in the environment. These naturally occurring chelating substances have the potential to enhance the solubility and mobility of actinides by forming soluble complexes. The unknown interaction between curium(III) and the aqueous DFO species is the subject of this paper. The interaction between soluble species of curium(III) and DFO was studied at trace curium(III) concentrations (3 x 10-7 M) using time-resolved laser-induced fluorescence spectroscopy (TRLFS). Three Cm3+ - DFO species, MpHqLr, could be identified from the luminescence spectra, CmH2DFO2+, CmHDFO+, and CmDFB, having emission maxima at 599, 611, and 614 nm, respectively. The as well large formation constants, log β121 = 31.62 ± 0.23, log β111 = 25.70 ± 0.17, and log β101 = 16.80 ± 0.40, compared to those of other chelating agents illustrate the unique complexation properties of hydroxamate-type siderophores. An indirect excitation mechanism for the curium(III) luminescence was observed in the presence of the DFO molecules.
Keywords: Curium; Desferrioxamine B; Fluorescence spectroscopy; TRLFS; Complexation
  • Bulletin of the Chemical Society of Japan 81(2008)7, 857-862

Publ.-Id: 10933 - Permalink


Photovoltaik-Anlagen im Netzparallelbetrieb: Erfahrungen eines Regionalversorgers
Rindelhardt, U.; Nitzschner, F.;
Die ENSO Strom AG ist der ostsächsische Regionalversorger. Das Netzgebiet reicht von Riesa im Westen bis zur polnischen Grenze im Osten und vom Erzgebirge im Süden bis zur Landesgrenze zu Brandenburg. Die ENSO Strom AG betreibt seit 1998 eine eigene PV-Anlage und veranstaltet seit dieser Zeit jährlich im Frühjahr einen „Solartag“, der zur Information und zum Erfahrungsaustausch der Anlagenbetreiber genutzt wird.
Im ENSO-Netzgebiet wurde 1990 die erste PV-Anlage der damaligen DDR in Betrieb genommen. Größere Zuwächse waren an die folgenden Förderprogramme gebunden. Mit dem 1000-Dächer-Programm erfolgte der erste wesentliche Schritt, nach einer Phase geringen Wachstums begann ab 2000 mit dem 100000-Dächer-Programm und dem EEG ein steiler Aufschwung. Das Leistungsspektrum der Anlagen reicht von 1 kW bis zu 1 MW, die durchschnittliche Leistung der etwa 1100 Anlagen lag Ende 2006 bei knapp 8 kW.
Die Netzintegration der meist kleinen Anlagen gestaltet sich unproblematisch, nur in Ausnahmefällen (Stichleitungen in ländlichen Netzen) waren Netzberechnungen und gegebenenfalls Festlegung anderer Verknüpfungspunkte erforderlich.
Die Ertragsentwicklung der PV-Anlagen im ENSO-Netzgebiet wird seit einigen Jahren verfolgt und auf den genannten Solartagen ausgewertet. Zwei Hauptergebnisse werden hier detailliert vorgestellt. Zum einen wird seit einigen Jahren der Zusammenhang zwischen der Einstrahlung im Netzgebiet und den Standorten der ertragsstärksten Anlagen untersucht. Diese Anlagen sind per se optimal ausgelegt und ausgerichtet. Es ist deutlich, dass zwischen den Standorten der besten Anlagen (Erträge 2006 > 1080 kWh/kW) und den vom DWD ermittelten Gebieten mit unterschiedlicher Einstrahlung kein nachweisbarer Zusammenhang besteht.
Dies deutet darauf hin, dass die den Ertrag bestimmenden technischen Unterschiede zwischen den einzelnen Anlagen größer sind als die Einstrahlungsdifferenzen im Netzgebiet.
Ein zweites interessantes Ergebnis ist die Ertragsentwicklung der besten Anlagen im Verlauf der letzten 4 Jahre. Seit 2003 wurden jährlich die jeweils besten 20 Anlagen ermittelt und deren gemittelter Ertrag (in kWh/kW) mit den entsprechenden Werten der Vorjahre verglichen. Es zeigte sich, dass in den Folgejahren jeweils neu errichtete Anlagen die älteren „Spitzenanlagen“ übertrafen: Das höheren Erträge neu errichteter Anlagen spiegeln offensichtlich technische Fortschritte in Komponentenqualität und Auslegung wider. Die Erträge erreichen Werte, die bisher nur von Anlagen aus dem süddeutschen Raum bekannt wurden.
Keywords: Photovoltaik, Netzintegration, Performance
  • Contribution to proceedings
    23. Symposium Photovoltaische Solarenergie, 05.-07.03.2008, Bad Staffelstein, Germany
  • Poster
    23. Symposium Photovoltaische Solarenergie, 05.-07.03.2008, Bad Staffelstein, Germany

Publ.-Id: 10931 - Permalink


Safety-oriented on-line monitoring of Grignard reactions
Kryk, H.; Hessel, G.; Schmitt, W.;
Grignard reagents are of vital importance as intermediate products of numerous organic syntheses in the fine-chemical and pharmaceutical industry. They are commonly prepared by reactions between organic halides and magnesium. These so-called Grignard reactions possess considerable hazard potentials due to the spontaneous heat release during the strongly exothermic initiation stage and the high reactivity of the Grignard compounds. From process safety point of view, it is of vital importance to establish industrially applicable methods for an objective real-time detection of the reaction start-up and for educt accumulations in the reaction mixture of the stirred tank reactor during the semi-batch process.
To avoid the use of fragile and expensive on-line analytics, a balance-based on-line monitoring approach for Grignard processes was developed and tested. By solving a set of energy/ mass balances in real-time, concentration profiles of reactants and products can be calculated based on process signals, substance data and plant parameters. Instead of operating under reflux conditions which are commonly used to control the spontaneous exothermic initiation of Grignard reactions, a pressurised vessel process regime is preferred when the on-line monitoring method is applied. In such a way, the accuracy of the calculation can be considerably increased.
Additionally, the approach provides an estimation of the hazard potential due to the reactivity of the organic halide accumulated in the reaction mixture. Assuming an adiabatic behaviour as the worst case, the Maximum Temperature of the Synthesis Reaction (MTSR) and the related pressure in the case of a runaway can be estimated as time-dependent functions and compared with pre-defined thresholds. Furthermore, these safety-relevant parameters enable the optimisation of the process regime. Thus, the reaction can be carried out as a non-stop semi-batch process to increase the space-time yield.
The real-time estimation of safety-relevant parameters, like MTSR courses and corresponding maximum reactor pressure profiles, enables application of advanced control strategies up to the point of a safety-oriented fully automatic control of Grignard reactions.
  • Poster
    1st European Conference on Process Analytics and Control Technology, 22.-25.04.2008, Frankfurt am M., Germany
  • Contribution to proceedings
    1st European Conference on Process Analytics and Control Technology, 22.-25.04.2008, Frankfurt am Main, Germany
    Book of Abstracts, P.15, S. 104

Publ.-Id: 10930 - Permalink


Weld material investigations of a VVER-440 reactor pressure vessel: results from the first trepan taken from the former Greifswald NPP
Rindelhardt, U.; Viehrig, H.-W.; Konheiser, J.; Schuhknecht, J.;
Between 1973 and 1990 4 units of the Russian NPP type WWER-440/230 were operated in Greifswald (former GDR). The operation was stopped after the German reunification, because the units did not completely follow western nuclear safety standards. Material probes from the pressure vessels were gained in the frame of the ongoing decommissioning procedure.
The investigations of this material started with material from the circumferential core weld of unit 1. This weld was annealed after 13 cycles and operated further for 2 cycles. Additionally, starting with cycle 11, dummy assemblies were inserted to reduce the neutron fluence in the RPV wall.
Firstly this paper presents results of the RPV fluence calculations depending on different loading schemes and on the axial weld position based on the Monte Carlo code TRAMO. The results show, that the use of the dummy assemblies reduces the flux by a factor of 2 – 5 depending on the azimuthal position. The fluence increase is reduced to 1/6 at the position of the maximum fluence.
The neutron fluence at the different circumferential welds is closely related to their distance to the core. The circumferential core weld (SN0.1.4) received a fluence of 2.4•1019 neutrons/cm² at the inner surface, it decreases to 0.8•1019 neutrons/cm² at the outer surface. The neutron fluences at the both other welds are 2 resp. 4 orders of magnitude smaller according to their distances to the core. It should be mentioned that in this cases the fluence gradient can be negative through the wall.
The first material investigations were done using a trepan from the circumferential core weld. Master Curve and Charpy V-notch testing were applied. Specimens from 7 locations through the thickness of the welding seam were tested according to ASTM E1921-05. The reference temperature T0 was calculated with the measured fracture toughness values, KJc, at brittle failure of the specimen. Generally the KJc values measured on pre-cracked and side-grooved Charpy size SE(B) specimens of the investigated weld metal follows the course of the Master Curve. The KJc values show a remarkable scatter. More values than expected lie below the 5% fractile. In addition the MC SINTAP procedure was applied to determine T0SINTAP of the brittle fraction of the data set. There are remarkable differences between T0 and T0SINTAP indicating macroscopic inhomogeneous weld metal. The highest T0 was about 50°C at a distance of 22 mm from the inner surface of the weld. It is 40 K higher compared with T0 at the inner surface. This is important for the assessment of ductile-to-brittle temperatures measured with sub size Charpy specimens made of weld metal from the inner RPV wall. This material does not represent the most conservative condition. Nevertheless, the Charpy transition temperature TT41J estimated with results of sub size specimens after the recovery annealing was confirmed by the testing of standard Charpy V-notch specimens.
The VERLIFE procedure prepared for the integrity assessment of WWER RPV was applied on the measured results. It enables the determination of a reference temperature, RTT0 to index a lower bound fracture toughness curve. This curve agrees with the MC 5% fractile as specified in ASTM E1921-05. The measured KJc values are not enveloped by this lower bound curve. However, the VERLIFE lower bound curve indexed with the SINTAP reference temperature RTT0SINTAP envelops the KJc values. Therefore for a conservative integrity assessment the fracture toughness curve indexed with a RT representing the brittle fraction of a dataset of measured KJc values has to be applied.
Keywords: neutron dosimetry, RPV embrittlement
  • Lecture (Conference)
    16th International Conference on Nuclear Engineering, ICONE-16, 11.-15.05.2008, Orlando, USA
  • Contribution to proceedings
    16th International Conference on Nuclear Engineering, ICONE-16, 11.-15.05.2008, Orlando, USA

Publ.-Id: 10929 - Permalink


Uranium(VI) sorption on montmorillonite and bentonite: Prediction and experiments
Nebelung, C.; Brendler, V.;
The sorption characteristics of U(VI) on bentonite and montmorillonite were investigated in batch experiments for understanding the near-field behaviour in geological nuclear repositories. Sorption parameters were determined in batch tests. The sorption on bentonite (KWK) was studied at different dry bulk densities of the clay (1.3, 1.6, 1.9 g/cm3) at pH 8 for the U(VI) concentration dependence (10-4 to 10-9 m). The sorption on the pure mineral montmorillonite (SWy-1) in 0.1 M NaClO4 was determined for the concentration dependence at pH 5.5, and pH dependence between pH 3 and 11). A scientifically founded description of sorption processes at the mineral-liquid surface is possible with the surface complexation models (SCM), the ion adsorption on surface sites as complexation reaction. We use the diffuse double layer model (DDL) to predict the sorption with the code MINTEQA2 (Version 4.03, US EPA May 2006), thermodynamic data of aqueous and solid species from the NEA-TDB [1], the mineral characterization and the respective protolysis data [2] and surface complex constants from [3].
The prediction of U(VI) sorption on montmorillonite at the pH dependence was very good. The modelling of the sorption on montmorillonite and bentonite versus U(VI) concentration shows a good agreement of measured and predicted values.

[1] Guillaumont, R. et al. (2003) “Update on the chemical thermodynamics of U, Np, Pu, Am, Tc. Chemical Thermo-dynamics”, Vol. 5 (OECD Nuclear Energy Agency, ed.), Elsevier, Amsterdam.
[4] Pabalan, R.T. et al. (1997) Aquat. Geochem. 2, 203-226.
[3] Pabalan, R.T. et al. (1998) in: Adsorption of metals by geomedia. Variables, mechanisms, and model applications; Jenne EA (Ed.), Academic Press; San Diego.

Funding by the European Commission (NF-PRO C2-ST-C-01) is gratefully acknowledged.
Keywords: sorption, uranium(VI), montmoroillonite, bentonite, pore water, surface complexation, MINTEQA2
  • Lecture (Conference)
    5th International Conference Uranium Mining and Hydrogeology (UMH V), 14.-18.09.2008, Freiberg, Germany
  • Contribution to external collection
    Broder J. Merkel, Andrea Hasche-Berger: Uranium, Mining and Hydrogeology, Berlin: Springer Verlag, 2008, 978-3-540-87745-5, 525-526

Publ.-Id: 10928 - Permalink


Experiments on the counter-current flow limitation (CCFL) in a model of a pressurised water reactor hot leg
Lucas, D.; Vallée, C.; Beyer, M.; Prasser, H.-M.; Deendarlianto;
Experiments were done on co-current and counter-current flows of air-water and also steam-water for a flat geometry reflecting a hot leg and steam generator inlet chamber of a Pressurized Water Reactor. The focus of the experiments was on the phenomenon of Counter-Current Flow Limitation. For air-water flows the flooding curve was obtained for this special geometry. The main aim of the experiments is however to provide a detailed database for CFD code validation. For this reason a model of a part of the hot leg and the steam generator inlet chamber was equipped with large glass windows to enable high speed camera observations. To use this measuring technique also for steam-water flows a new technology, the so-called pressure tank technology was used for the first time. The test section itself is built-in into a large pressure tank which can be operated for pressures up to 5 MPa. A condenser at the end of the test section guarantees the pressure equilibrium between the inside of the test section and the tank atmosphere. This enables to manufacture the test section from thin materials and to use large glass windows. For the first time steam-water co-current and counter-current flows were observed by high speed video observations at a pressure of 1.5 MPa. Further experiments with pressure up to 5 MPa will follow.
Keywords: stratified flow, CCFL, experiment, high speed video observation, pressure tank
  • Contribution to proceedings
    HEAT 2008, The Fifth International Conference on Transport Phenomena In Multiphase Systems, 30.06.-03.07.2008, Bialystok, Poland
    Transport Phenomena In Multiphase Systems, Volume 1, Bialystok, 325-332
  • Poster
    HEAT 2008, The Fifth International Conference on Transport Phenomena In Multiphase Systems, 30.06.-03.07.2008, Bialystok, Poland

Publ.-Id: 10926 - Permalink


Experimental Evaluation of Functional Imaging for Radiotherapy
Zips, D.; Yaromina, A.; Schütze, C.; Wüllrich, K.; Krause, M.; Krause, M.; Hessel, F.; Eicheler, W.; Dörfler, A.; Brüchner, K.; Menegakis, A.; Zhou, X.; Bergmann, R.; van den Hoff, J.; Beuthien-Baumann, B.; Baumann, M.;
Functional imaging for radiotherapy is expected to provide diagnostic as well as prognostic information, to monitor treatment, to help stratification of patients for specific therapeutic interventions and to guide dose-painting. During the last years radiotracer-based functional imaging with positron emission tomography (PET), mainly using the glucose analogue [18F]2-fluoro-2-deoxy-D-glucose ([18F]FDG), has been widely implemented in radiotherapy for a more accurate staging and an improved target volume definition in a variety of tumor types [1, 2, 4]. While the technology for integration of functional imaging into clinical radiotherapy is increasingly available, the biological implications for radiation response are poorly understood [6]. Importantly, biomarker development needs to account for the specific parameters known to determine the results of curative radiotherapy. Clinical as well as preclinical studies are necessary to exploit the potential of functional imaging to improve outcome after radiotherapy. In the following sections recent findings from experimental studies using xenotransplanted tumors in nude mice carried out in our laboratories are briefly summarized.
Keywords: Functional imaging · Tumor xenografts · Radiotherapy · FDG-PET · Small animal PET · Hypoxia · Proliferation · Cancer stem cells · Local tumor control

Publ.-Id: 10925 - Permalink


CFD-modeling and experiments of insulation debris transport phenomena in water flow
Krepper, E.; Cartland-Glover, G.; Grahn, A.; Weiss, F.-P.; Alt, S.; Hampel, R.; Kästner, W.; Seeliger, A.;
The investigation of insulation debris generation, transport and sedimentation becomes more important with regard to reactor safety research for PWR and BWR, when considering the long-term behavior of emergency core coolant systems during all types of loss of coolant accidents (LOCA). The insulation debris released near the break during a LOCA incident consists of a mixture of disparate particle population that varies with size, shape, consistency and other properties. Some fractions of the released insulation debris can be transported into the reactor sump, where it may perturb/impinge on the emergency core cooling systems.
Open questions of generic interest are for example the particle load on strainers and corresponding pressure drop, the sedimentation of the insulation debris in a water pool, its possible re-suspension and transport in the sump water flow. A joint research project on such questions is being performed in cooperation with the University of Applied Science Zittau/Görlitz. The project deals with the experimental investigation and the development of CFD models for the description of particle transport phenomena in coolant flow. While the experiments are performed at the University Zittau, the theoretical work is concentrated at Forschungszentrum Dresden-Rossendorf.
In the current paper the basic concepts for CFD modeling are described and feasibility studies including the conceptual design of the experiments are presented.
Keywords: CFD, two-fluid approach, fiber flows
  • Nuclear Technology 167(2009)1, 46-59

Publ.-Id: 10924 - Permalink


Spectroscopic study of the uranium(IV) complexation by organic model ligands in aqueous solution
Schmeide, K.; Bernhard, G.;
In the present study, the model ligands citric acid and glutaric acid as well as mandelic acid and glycolic acid were chosen for the uranium(IV) complexation. These ligands stand for a variety of organic ligands in aqueous systems. The complex formation constants for the uranium(IV) complexation were determined applying UV-Vis absorption spectroscopy. Thereby, the hydrogen ion concentration and the ionic strength were varied.
For instance, the complexation of uranium(IV) with citric acid has been investigated in dependence on hydrogen ion concentration (1 M, 0.5 M, 0.1 M and 0.05 M). Thereby, the formation of 1:1 and 1:2 complexes was detected in the citrate media. The stability constants for 1:1 and 1:2 uranium(IV) citrate complexes of the type MpHqLr were determined with log ß101 = 13.5 ± 0.2 and log ß102 = 25.1 ± 0.2. The obtained log ß fit well in the known series of log ß determined for the complexation of further tetravalent actinides (e.g., Pu(IV), Np(IV), Th(IV)) by citric acid.
Keywords: uranium, tetravalent, complexation, citric acid
  • Lecture (Conference)
    5th International Conference Uranium Mining Hydrogeology (UMH V), 14.-18.09.2008, Freiberg, Germany
  • Contribution to external collection
    Broder J. Merkel, Andrea Hasche-Berger: Uranium, Mining and Hydrogeology, Berlin: Springer Verlag, 2008, 978-3-540-87745-5, 591-598

Publ.-Id: 10923 - Permalink


Application of the effective convectivity model to an PWR in-vessel retention scenario
Willschütz, H.-G.; Altstadt, E.; Abendroth, M.;
For the very improbable scenario of a severe accident with core meltdown and for-mation of a melt pool in the lower plenum of a Light Water Reactor (LWR) Pressure Vessel (RPV) computer codes are developed to assess the thermal and mechanical behaviour of the RPV wall. If the RPV wall fails within the lower head region, the melt is discharged into the reactor pit, which can result in severe thermal and mechanical loads for the containment. One accident management strategy could be to stabilize the in-vessel debris or melt pool configuration in the RPV via external flooding.
Based on the successful simulation and analysis work of the FOREVER-experiments (cf. Fig. 1 and [1]) coupled thermo-mechanical models have been developed further to simulate the prototypical scenario of an In-Vessel-Retention in large PWRs [2]. According to the recent publication “An Effective Convectivity Model (ECM) for Simulation of In-Vessel Core Melt Progression in a Boiling Water Reactor” by Tran and Dinh [3] the thermal part of the FE-model developed at FZD is now improved to be able to apply the new ECM approach.
Keywords: In-vessel melt retention, reactor pressure vessel, thermal analysis, effective heat generation
  • Contribution to proceedings
    Jahrestagung Kerntechnik 2008, 27.-29.05.2008, Hamburg, Germany
    Proceedings of the Annual Meeting of Nuclear Technology 2008
  • Lecture (Conference)
    Jahrestagung Kerntechnik 2008, 27.-29.05.2008, Hamburg, Germany

Publ.-Id: 10922 - Permalink


Fracture mechanical analysis of a VVER-440 PTS scenario
Abendroth, M.; Altstadt, E.;
The paper describes the modelling and evaluation of a pressurized thermal shock (PTS) scenario in a VVER-440 reactor pressure vessel due to an emergency case. An axially oriented semi-elliptical crack is assumed to be located in the core welding seam. Two variants of fracture mechanical evaluation are performed: the analysis of a sub-cladding crack and of a surface crack. Three-dimensional finite element (FE) models are used to compute the global transient temperature and stress-strain fields. By using a three-dimensional submodel, which includes the crack, the local crack stress-strain field is obtained. Within the subsequent postprocessing using the j integral technique the stress intensity factors KI along the crack front are obtained. The FE results are compared to analytical calculations proposed in the VERLIFE code. The stress intensity factors are compared to the fracture toughness curve for the weld material.
Keywords: Fracture mechanics, pressurised thermal shock, reactor pressure vessel, finite elements
  • Contribution to proceedings
    Jahrestagung Kerntechnik 2008, 27.-29.05.2008, Hamburg, Germany
    Proceedings of the Annual Meeting of Nuclear Technology, Sankt Augustin: dbcm GmbH
  • Lecture (Conference)
    Jahrestagung Kerntechnik 2008, 27.-29,05,2008, Hamburg, Germany

Publ.-Id: 10921 - Permalink


CFD simulation of polydispersed bubbly two phase flow around an obstacle
Krepper, E.; Ruyer, P.; Beyer, M.; Lucas, D.; Prasser, H.-M.; Seiler, N.;
This paper concerns the model of a polydispersed bubble population in the frame of an ensemble averaged two-phase flow formulation. The ability of the moment density approach to represent bubble population size distribution within a multi-dimensional CFD code based on the two-fluid model is studied. Two different methods describing the polydispersion are presented: (i) a moment density method, developed at IRSN, to model the bubble size distribution function and (ii) a population balance method considering several different velocity fields of the gaseous phase. The first method is implemented in the NEPTUNE_CFD code whereas the second method is implemented in the CFD code ANSYS/CFX. Both methods consider coalescence and break-up phenomena and momentum inter-phase transfers related to drag and lift forces.
Air-water bubbly flows in a vertical pipe with obstacle of the TOPFLOW experiments series performed at FZD are then used as simulations test cases. The numerical results, obtained with NEPTUNE_CFD and with ANSYS/CFX, allow attesting the validity of the approaches. Perspectives concerning the improvement of the models, their validation, as well as the extension of their applicability range are discussed.
Keywords: bubbly flow, CFD, population balance method, moment density method, non-drag forces, bubble breakup, bubble coalescence, model validation

Publ.-Id: 10920 - Permalink


Bremsstrahlung in PLUTO simulations
Wüstenfeld, J.;
The talk presents our parametrization of a theoretical calculation of nuceon - nucleon Bremsstrahlung, done by L. Kaptari and B. Kaempfer, that is to be implemented in the PLUTO somulation framework
Keywords: Bremsstrahlung, PLUTO
  • Lecture (Conference)
    HADES Collaboration Meeting XVIII, 30.10.-04.11.2007, Ayia Napa, Cyprus

Publ.-Id: 10919 - Permalink


R&D for RPC - news from ELBE
Wüstenfeld, J.;
The talk presents recent results from our investigations of new nanocomposite materials for the construction of resistive plate counters. This counters are forseen as timing detectors for the upcomming Compressed Baryonic Matter (CBM) experiment at FAIR. These tests where performed at the electron beam of ELBE.
Keywords: RPC, nano composite materials, ELBE
  • Lecture (Conference)
    10th CBM Collaboration Meeting, 25.-28.09.2007, Dresden, Germany

Publ.-Id: 10918 - Permalink


Dosiskontrolle mit PET bei der Schwerionen-Tumortherapie
Priegnitz, M.; Shakirin, G.; Enghardt, W.; Fiedler, F.; Möckel, D.; Pawelke, J.;
Übersicht über die Anwendung des in-beam PET bei der Schwerionentherapie.
  • Poster
    Strategie-Meeting des OncoRay, 07.-08.01.2008, Gröditz, Germany

Publ.-Id: 10917 - Permalink


In-beam PET an harten Photonenstrahlen
Möckel, D.; Kluge, T.; Pawelke, J.; Enghardt, W.;
Übersicht über die Anwendung von in-beam PET bei harten Photonen
  • Poster
    Strategie-Meeting des OncoRay, 08.-09.01.2008, Gröditz, Germany

Publ.-Id: 10916 - Permalink


In-beam PET-Monitoring der Kohlenstoff-Ionentherapie: 10 Jahre Erfahrung in der klinischen Anwendung
Priegnitz, M.; Fiedler, F.; Möckel, D.; Parodi, K.; Pawelke, J.; Shakirin, G.; Skowron, J.; Enghardt, W.;
Ionenstrahlen bieten aufgrund ihrer besonderen physikalischen und biologischen Eigenschaften die Möglichkeit einer präzisen Tumorbestrahlung mit geringer Belastung für das umliegende gesunde Gewebe. Dadurch können auch tief sitzende Tumoren in der Nähe von Risikoorganen bestrahlt werden, die mit konventioneller Strahlung nur eingeschränkt therapierbar sind.
Im Dezember 1997 begann die Behandlung von Krebspatienten mit Kohlenstoffionen an der Gesellschaft für Schwerionenforschung (GSI) in Darmstadt. An dieser europaweit ersten Schwerionentherapie-Pilotanlage sind bis heute ca. 400 Patienten mit Kopf- und Beckentumoren bestrahlt worden.
Da die durch die Ionenstrahlen deponierte Dosisverteilung äußerst empfindlich auf Veränderungen in der Ionen-Reichweite reagiert, ist eine Verifikation der Bestrahlungsfeldposition unabhängig von der Strahlapplikation wünschenswert. Hierzu wurde am Forschungszentrum Dresden-Rossendorf eine Methode entwickelt, die auf der Detektion von Annihilationsphotonen mit PET (Positronen-Emissions-Tomographie) und einem Vergleich der gemessenen, rekonstruierten Aktivität mit Vorhersagen aus der Bestrahlungsplanung beruht. Die Positronen emittierenden Nuklide entstehen während der Bestrahlung durch Kernreaktionen zwischen den Atomkernen des Gewebes und den Ionen des Therapiestrahls. Dieses so genannte in-beam PET-Verfahren ist die zurzeit einzige bekannte Methode zur in-situ und in-vivo Verifikation der Dosisapplikation bei der Bestrahlung mit Ionen. Das Verfahren kam bei nahezu allen an der GSI behandelten Patienten zum Einsatz und führte zu einer Verbesserung des verwendeten Strahlenmodells. Ferner werden sporadische Abweichungen zwischen geplanter und realisierter Teilchenreichweite nachgewiesen. Diese Abweichungen können ihre Ursachen z.B. in temporären anatomischen Veränderungen im durchstrahlten Volumen, in geringfügigen Bewegungen des Patienten während der Bestrahlung oder in Fehlern bei der Patientenpositionierung haben.
Die gewebeabhängige Kinetik des metabolisch verursachten Abtransportes der Aktivität aus dem bestrahlten Volumen ist bisher nur unzureichend bekannt und steht einer quantitativen Berechnung der Dosis aus der gemessenen Aktivitätsverteilung entgegen. Hier kommt ein interaktives Verfahren zur Anwendung, das die Identifikation der Ursachen von auftretenden Abweichungen ermöglicht.
  • Contribution to proceedings
    14. Jahrestagung der Deutschen Gesellschaft für Radioonkologie, 25. Jahrestagung der Österreichischen Gesellschaft für Radioonkologie, Radiobiologie und Medizinische Strahlenphysik, 01.-04.05.2008, Wien, Austria
    Strahlentherapie und Onkologie 184(2008)Suppl. 1, 9-10
  • Lecture (Conference)
    14. Jahrestagung der Deutschen Gesellschaft für Radioonkologie, 25. Jahrestagung der Österreichischen Gesellschaft für Radioonkologie, Radiobiologie und Medizinische Strahlenphysik, 01.-04.05.2008, Wien, Österreich

Publ.-Id: 10915 - Permalink


Synthesis and Application of [18F]FDG-maleimidehexyloxime ([18F]FDG-MHO): A [18F]FDG-based Prosthetic Group for the Chemoselective 18F-Labeling of Peptides and Proteins
Wüst, F.; Berndt, M.; Bergmann, R.; van den Hoff, J.; Pietzsch, J.;
2-[18F]Fluoro-2-deoxy-D-glucose ([18F]FDG) as the most important PET radiotracer is available in almost every PET center. However, there are only very few examples using [18F]FDG as a building block for the synthesis of 18F-labeled compounds. The present study describes the use of [18F]FDG as building block for the synthesis of 18F-labeled peptides and proteins. [18F]FDG was converted into [18F]FDG-maleimidehexyloxime ([18F]FDG-MHO), a novel [18F]FDG-based prosthetic group for the mild and thiol group-specific 18F labeling of peptides and proteins. The reaction was performed at 100°C for 15 min in a sealed vial containing [18F]FDG and N-(6-aminoxy-hexyl)maleimide in 80% ethanol. [18F]FDG-MHO was obtained in 45-69% radiochemical yield (based upon [18F]FDG) after HPLC purification in a total synthesis time of 45 min. Chemoselecetive conjugation of [18F]FDG-MHO to thiol groups was investigated by the reaction with the tripeptide glutathione (GSH) and the single cysteine containing protein annexin A5 (anxA5). Radiolabeled annexin A5 ([18F]FDG-MHO-anxA5) was obtained in 43-58% radiochemical yield (based upon [18F]FDG-MHO, n=6), and [18F]FDG-MHO-anxA5 was used for a pilot small animal PET study to assess in vivo biodistribution and kinetics in a HT-29 murine xenograft model.
  • Bioconjugate Chemistry 19(2008)6, 1202-1210

Publ.-Id: 10914 - Permalink


A new 34-membered N6O4-donor macrocycle: synthetic, X-ray and solvent extraction studies
Wenzel, M.; Gloe, K.; Gloe, K.; Bernhard, G.; Clegg, J. K.; Ji, X.-K.; Lindoy, L. F.;
The synthesis and crystal structure of a new 34-membered N6O4-donor macrocycle 2 is reported. Solvent extraction experiments (water/chloroform) indicated that 2 acts as an efficient extractant towards silver(I) and zinc(II) at pH values beyond 6 while the extraction of iodide and chromate occurs below this pH. A competitive metal extraction experiment at pH 7.2 in which the perchlorate salts of cobalt(II), nickel(II), copper(II), zinc(II) and cadmium(II) were present together in the aqueous phase led to the following order of increasing extraction efficiency: cobalt(II) o nickel(II) o zinc(II) o copper(II) B cadmium(II). A substantial synergistic enhancement of zinc(II) salt extraction was observed for a dual-host extraction system using the macrocycle 2 as cation binder and the tripodal thiourea ligand 3 as anion receptor; in particular, a notable extraction of zinc(II) sulfate was obtained.

Publ.-Id: 10913 - Permalink


Two-photon photocurrent autocorrelation using intersubband transitions at nearly-resonant excitation
Schneider, H.; Maier, T.; Liu, H. C.; Walther, M.;
We investigate nonlinear mid-infrared detection via two-photon transitions involving two bound subbands and one continuum resonance in an n-type multiple quantum well. By varying the excitation energy, we have tuned the two-photon transition from resonant, yielding optimum resonant enhancement with a real intermediate state, to nearly-resonant, with a virtual but resonantly enhanced intermediate state. For autocorrelation purposes, the latter configuration improves time resolution whilst partially retaining a resonant enhancement of the two-photon transition strength.
Keywords: intersubband transition, multiple quantum well, two-photon excitation, mid-infrared detector, ultrafast spectroscopy
  • Open Access LogoOptics Express 16(2008)3, 1523-1528

Publ.-Id: 10912 - Permalink


Experimental investigation and CFD simulation of the behaviour of mineral wool in the reactor sump
Krepper, E.; Cartland-Glover, G.; Grahn, A.; Weiss, F.-P.; Alt, S.; Hampel, R.; Kästner, W.; Seeliger, A.;
The investigation of insulation debris generation, transport and sedimentation becomes important with regard to reactor safety research for PWR and BWR, when considering the long-term behavior of emergency core cooling systems during all types of loss of coolant accidents (LOCA). The insulation debris released near the break during a LOCA incident consists of a mixture of disparate particle population that varies with size, shape, consistency and other properties. Some fractions of the released insulation debris can be transported into the reactor sump, where it may perturb/impinge on the emergency core cooling systems.
Open questions of generic interest are the sedimentation of the insulation debris in a water pool, its possible re-suspension and transport in the sump water flow and the particle load on strainers and corresponding pressure drop. A joint research project on such questions is being performed in cooperation between the University of Applied Sciences Zittau/Görlitz and the Forschungszentrum Dresden-Rossendorf. The project deals with the experimental investigation of particle transport phenomena in coolant flow and the development of CFD models for its description. While the experiments are performed at the University at Zittau/Görlitz, the theoretical modeling efforts are concentrated at Forschungszentrum Dresden-Rossendorf.
In the current paper the basic concepts for CFD modeling are described and feasibility studies including the conceptual design of the experiments are presented.
Keywords: CFD, two-fluid approach, fiber flows
  • Contribution to proceedings
    16th International Conference on Nuclear Engineering, ICONE-16, 11.-15.05.2008, Orlando, Florida, USA
  • Lecture (Conference)
    16th International Conference on Nuclear Engineering, ICONE-16, 11.-15.05.2008, Orlando, Florida, USA

Publ.-Id: 10911 - Permalink


Development of segmented straws for very high-rate capability coordinate detector
Davkov, K.; Davkov, V.; Geyer, R.; Gusakov, Y. V.; Kekelidze, G. D.; Myalkovskiy, V. V.; Naumann, L.; Peshekhonov, D. V.; Peshekhonov, V. D.; Savenkov, A. A.; Tikhomirov, V. O.; Viryasov, K. S.;
To reduce the occupancy of the large-size coordinate detectors, the high-granularity straw tracking chamber has been designed and tested. The main tasks were to improve the detector granularity and provide the best value of the detector radiation thickness. We have developed the techniques of the multiple anode production, assembling of the segmented straws and the low-mass readout by means of flat cable. Testing of the constructed prototypes has shown that these techniques can be applied to build the high-granularity straw detectors.
Keywords: Straw-drift chamber; Tracking detector; High granularity; Small occupancy

Publ.-Id: 10910 - Permalink


Review of available data for validation of nuresim two-phase CFD software applied to CHF investigations
Bestion, D.; Anglart, H.; Carraghiaur, D.; Péturaud, P.; Smith, B.; Andreani, M.; Niceno, B.; Krepper, E.; Lucas, D.; Moretti, F.; Galassi, M. C.; Macek, J.; Vyskocil, L.; Koncar, B.; Hazi, G.;
The NURESIM Integrated Project of the 6th European Framework Program was envisaged to initiate the development of the next-generation common European Standard Software Platform for simulating nuclear reactors. The overall objective of NURESIM Thermalhydraulic sub-project is to improve the understanding and the predictive capabilities of the simulation tools for key two-phase flow thermal-hydraulic processes such as the Critical Heat Flux (CHF). A multi-scale analysis of reactor thermalhydraulics is envisaged and two-phase CFD is developed to allow some zoom on local processes when the resolution of system codes is not sufficient.
Current industrial methods for CHF mainly use the sub-channel analysis and empirical CHF correlations based on large scale experiments having the real geometry of the reactor assembly. The NURESIM-TH activities regarding CHF aim at using two-phase CFD as a tool for understanding boiling flow processes, in order to subsequently help new fuel assembly design and to develop better CHF predictions in both PWR and BWR. A “Local Predictive Approach” may be envisaged for the long term where CHF empirical correlations would be based on local T/H parameters provided by CFD.
This paper presents a review of existing experimental data bases which can be used for validation of the two-phase CFD application to Critical Heat Flux (CHF) investigations with respect to nuclear reactors. The phenomenology of DNB and Dry-Out are detailed identifying all basic flow processes which require a specific modeling in CFD tool. The resulting program of work is given and the current state of the art of the modeling is presented.
Keywords: Critical heat flux, experimenbtal data, CFD simulation

Publ.-Id: 10909 - Permalink


An overview of the Pressurized Thermal Shock issue in the context of the NURESIM project
Lucas, D.; Bestion, D.; Bodèle, E.; Scheuerer, M.; D’Auria, F.; Mazzini, D.; Smith, B.; Tiselj, I.; Martin, A.; Lakehal, D.; Seynhaeve, J.-M.; Kyrki-Rajamäki, R.; Ilvonen, M.; Macek, J.; Coste, P.;
This paper reports activities regarding the simulation of Pressurized Thermal Shock (PTS) performed within the European Integrated Project NURESIM. Some Loss of Coolant Accident (LOCA) scenarios for Pressurized Water Reactors (PWR) may cause Emergency Core Coolant injection into the cold leg and thus lead to PTS situations. They imply the formation of temperature gradients in the thick vessel walls with consequent localized stresses and the potential for propagation of possible flaws present in the material. The present paper, in the area of fluid dynamics, focuses on the study of two-phase conditions that are potentially at the origin of PTS. It summarizes recent advances in the understanding of the two-phase phenomena occurring within the geometric region of the nuclear reactor, i.e. the cold leg and the downcomer, where the ‘PTS fluid-dynamics’ is relevant. Available experimental data for validation of two-phase CFD simulation tools are reviewed and the capabilities of such tools to capture each basic phenomenon are discussed. Key conclusions show that several two phase flow sub-phenomena are involved and can individually be simulated at least at a qualitative level, but the capability to simulate their interaction and the overall system performance is still limited. In the near term, one may envisage a simplified treatment of two-phase PTS transients by neglecting some effects which are not yet well controlled, leading to slightly conservative predictions.
Keywords: PTS, CFD, Nuclear reactor simulation

Publ.-Id: 10908 - Permalink


Simulations of DEBORA data with CFX
Krepper, E.;
In the DEBORA experiments subcooled boiling is investigated heating up Dichlorodifluoromethane (R12) in a side wall heated tube. Radial profiles for gas volume fraction, gas velocity, liquid temperatures and bubble sizes were measured at the end of the heated length. This enables the validation not only of the wall boiling model but also of the models for liquid/gas momentum, heat and mass transfers.
The report describes the model simulating the wall boiling preliminary implemented in CFX-11 which is also implemented in the NEPTUNE code. These approaches are based on the proposal of Kurul and Podowski (1990). Specific model developments concerning the near wall phenomena are described in the report. Furthermore the momentum exchange models used in the CFX simulations are described.
The same parameters for the model correlations adjusted for water/steam flow were applied simulating the fluid R12. To investigate the influence on the results, essential boiling model parameters were varied and the sensitivity of the results is shown. The need of further model development and of further experiments can be confirmed. The validation applying for the different models shows the state and the limits of the present modelling.
The simulations are intended for the comparison to other CFD models e.g. to the NURESIM-CFD platform.
Keywords: Two phase flow, CFD, subcooled boiling, drag forces, non drag forces, experimente, model validation
  • Article, self-published (no contribution to HZDR-Annual report)
    Forschungszentrum Rossendorf 2008
    NURESIM-SP2-TH-D2.2.3.2 (Jauary 2008)
    37 Seiten

Publ.-Id: 10907 - Permalink


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