Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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31745 Publications
Magnetfeldkontrollierte Erstarrungsvorgänge in metallischen Legierungen
Eckert, S.; Boden, S.; Räbiger, D.; Willers, B.;
Metallschmelzen in industriellen Prozessen unterliegen in der Regel verschiedenen Arten von Strömungen. Diese Strömungen haben einen entscheidenden Einfluss auf den Wärme- und Stofftransport, und damit zumeist auch auf die Effizienz des Prozesses oder die Qualität des Endproduktes. Zukünftige Anstrengungen im Hinblick auf eine Optimierung derartiger Anlagen oder Technologien müssen aus diesem Grund eine wirksame Strömungskontrolle berücksichtigen.
Elektromagnetische Felder eröffnen aufgrund des kontaktlosen Zugangs und der einfachen Regelbarkeit eine attraktive Möglichkeit zur Strömungskontrolle. Eine gezielte Einflussnahme setzt aber ein umfangreiches Wissen über das Strömungsfeld und die Wechselwirkung mit den elektromagnetischen Kraftfeldern voraus. Neben numerischen Simulationen sind Modellexperimente mit sogenannten „kalten“ Schmelzen, d.h. mit Flüssigmetallen mit einem Schmelzpunkt < 300°C, ein unverzichtbares Mittel, um die Strömungsvorgänge besser zu verstehen und geeignete Maßnahmen zur Strömungskontrolle zu ergreifen. Die Röntgenradioskopie hat sich dabei als ein wichtiges diagnostisches Mittel herausgestellt, um Erstarrungsvorgänge in-situ zu visualisieren. Auf Grundlage der Bewertung der Grauwertbilder mit Hilfe der "Optical Flow"-Methode ist es erstmalig gelungen, Strömungsstrukturen in unmittelbarer Umgebung zur Erstarrungsfront während der Erstarrung darzustellen.
Im Vortrag werden am Beispiel der Erstarrung Einsatzmöglichkeiten elektromagnetischer Felder in der Gießereiindustrie erläutert.
Keywords: solidification, metal alloys, electromagnetic fields, X-ray radioscopy, Optical Flow
  • Invited lecture (Conferences)
    Seminar "Struktur und Eigenschaften kondensierter Materie", 20.05.2008, Chemnitz, Deutschland

Publ.-Id: 11338 - Permalink


Complexation of Curium(III) and Europium(III) with Urea and in Human Urine
Heller, A.; Barkleit, A.; Bernhard, G.;
The complexation of europium(III) and curium(III) in aqueous urea solution has been studied at pH 1 – 8, I = 0.1 (NaClO4), room temperature and trace metal concentrations using time-resolved laser-induced fluorescence spectroscopy. In case of curium(III) a red shift of the luminescence maximum occurs upon complexation, while for europium(III) emission wavelengths remain unaltered but the peak splitting is changed significantly. Both heavy metals form very weak complexes of the formulae ML3+ which are stable until pH 6. Stability constants were determined to be -0.12 ± 0.05 for europium(III) and -0.31 ± 0.13 for curium(III). In human urine samples the luminescence spectra of both heavy metals differ significantly from those in water and aqueous urea solution. Red shift of the luminescence maximum of curium(III) is more pronounced and peak splitting in case of europium(III) enhanced. Besides that, lifetimes of the species formed in human urine vary markedly from those of the ML3+ complexes with urea. Furthermore, the speciation of the heavy metals seems to depend on the pH of the urine sample.
Keywords: curium(III), europium(III), urea, complexation, urine, heavy metal speciation, TRLFS
  • Contribution to proceedings
    NRC7 - Seventh International Conference on Nuclear and Radiochemistry, 24.-29.08.2008, Budapest, Hungary

Publ.-Id: 11337 - Permalink


Ion irradiation induced local creation of ferromagnetism in Fe60Al40 alloys
Strache, T.; Liedke, M. O.; Fassbender, J.ORC; Möller, W.; Menéndez, E.; Sort, J.; Suriñach, S.; Baró, M. D.; Gemming, T.; Weber, A.; Heyderman, L. J.; Rao, K. V.; Deevi, S. C.; Nogues, J.
Ion irradiation of Fe60Al40 alloys results in the phase transformation from the paramagnetic, chemically ordered B2-phase to the ferromagnetic, chemically disordered A2-phase. The magnetic phase transformation is related to the number of displacements per atom (dpa) during the irradiation. For heavy ions (Ar+, Kr+, Xe+) a universal curve is observed with a steep increase in the fraction of ferromagnetic phase reaching saturation, i. e., a complete phase transformation, at about 0.5 dpa. This proves the purely ballistic nature of the disordering process. If light ions are used (He+, Ne+) a pronounced deviation from the universal curve is observed. This is attributed to bulk vacancy diffusion from dilute collision cascades, which leads to a partial recovery of the thermodynamically favored B2-phase. Comparing different noble gas ion irradiation experiments allows to asses the corresponding counteracting contributions. In addition, the potential to create local ferromagnetic areas embedded in a paramagnetic matrix is demonstrated.
Keywords: magnetism, ion irradiation, binary alloys, intermetallic, FIB, patterning
  • Lecture (Conference)
    Ionenstrahlphysik und Nanotechnologie, GSI-Workshop, 11.-12.04.2008, Darmstadt, Germany

Publ.-Id: 11336 - Permalink


Magnetic lithography on paramagnetic FeAl alloys by selective ion irradiation
Sort, J.; Menendez, E.; Liedke, M. O.; Strache, T.; Fassbender, J.ORC; Gemming, T.; Weber, A.; Heydermann, L. J.; Surinach, S.; Rao, K. V.; Deevi, S. C.; Baro, M. D.; Nogues, J.
The atomically-ordered Fe60Al40 (at. %) alloy is paramagnetic at room temperature but it becomes ferromagnetic when subject to structural disorder [1]. This effect has been recently used to generate arrays of sub-100 nm ferromagnetic dots embedded in a paramagnetic matrix. To selectively induce structural disorder, local irradiation procedures, either through lithographed masks or using focused ion beam, have been utilized. Due to the low ion doses used, the irradiation processes do not induce any surface corrugation, thus circumventing tribological problems. The fabricated entities exhibit a range of magnetic properties depending on the size and shape. Furthermore, when the patterned sheets are annealed at sufficiently high temperatures (i.e., around 900 K), the magnetic properties are erased due to the annealing-induced atomic reordering. This method may be extrapolated to a variety of other intermetallic systems such as Fe2AlMn, Ni3Sn2 or CoGa and also to austenitic steels. The obtained magnetic structures may have technological applications, such as magnetic sensors or patterned recording media.
Partial financial support from the Spanish 2005SGR-00401, MAT2007-66302-C02 and MAT2007-61629 research projects, the EU-RITA program “Center for the Application of Ion Beams in Materials Research” (under contract no. 025646) and the Swedish Agencies VINNOVA and SSF is acknowledged. E. M. acknowledges his FPI fellowship from the Spanish Ministerio de Educación y Ciencia, co-financed by the ESF.
[1] J. Nogués et al., Phys Rev. B Phys. Rev. B 74, 024407 (2006)
Keywords: magnetism, ion irradiation, focused ion beam, binary alloys, disordering
  • Invited lecture (Conferences)
    9th International Conference on Nanostructured Materials, 01.-06.06.2008, Rio de Janeiro, Brazil

Publ.-Id: 11334 - Permalink


Structures and Stoichiometry of Actinide Complexes: Challenges of Combining EXAFS and Quantum Chemistry
Tsushima, S.;
EXAFS spectroscopy has been proved to be a very powerful tool for studying the structures of actinide complexes in aqueous and non-aqueous systems. The application of EXAFS spectroscopy has been extended to the systems with mixed species and / or species with very dilute concentration. Using EXAFS alone, however, has inherent limitations such as a lack of spatial information of the molecules and rather poor radial resolutions which make it difficult to differentiate two or more bonds with similar distances. Factor analysis by Rossberg et al., for example, was proven to be an effective method for separating individual species from the mixed ones [1]. Such method becomes even more powerful if corresponding 3D structural information can be provided by quantum chemical calculations.
Here, I show two examples in which density functional theory (DFT) calculations are proved to be very helpful for actinide speciation studies. In first case, Th(IV) hydroxo and sulfato complexes were studied by DFT calculations. A significant decrease in the coordination number (CN) was observed as a stepwise hydrolysis reaction of Th4+ ion proceeds. The fourth hydrolysis product, Th(OH)40, has a reduced CN of 6 and readily forms a dimeric complex via a Th-OH-Th bridging. The oligomerization makes Th(OH)40 to be an unstable aqueous species. In case of sulfate, the CN and the average Th-O distance of Th(SO4)20 remains essentially as same as Th4+ aquo ion. This result is in agreement with the EXAFS study by Hennig et al. [2].
In the second example, the reduction potential of Pu(VIII) / Pu(VII) couple was studied as the same way as in a recent study [3]. The geometries and the energies of the complexes were calculated at the B3LYP level. The spin-orbit effect for Pu(VII) species was corrected 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 in alkaline solution which indicates that it is difficult to obtain Pu(VIII) in aqueous solution.
REFERENCES
1. A. Roßberg, T. Reich, G. Bernhard, Anal. Bioanal. Chem. 376, 631-638, (2003).
2. C. Hennig, K. Schmeide, V. Brendler, H. Moll, S. Tsushima, A. C. Scheinost, Inorg. Chem. 46, 5882-5892 (2007).
3. S. Tsushima, U. Wahlgren, I. Grenthe, J. Phys. Chem. A 110, 9175-9182 (2006).
  • Invited lecture (Conferences)
    Actinide XAS 2008, 15.-17.07.2008, Soleil, France

Publ.-Id: 11333 - Permalink


Biogeochemical changes induced by uranyl nitrate in a uranium waste pile
Selenska-Pobell, S.; Geissler, A.; Flemming, K.; Merroun, M.; Geipel, G.; Reuther, H.;
Treatments with uranyl nitrate induced strong changes in subsurface bacterial community of a uranium mining waste pile. Most of the bacterial populations, stimulated at the initial stages of the treatment, used the added nitrate for respiration. Mössbauer spectroscopic analyses showed that at the later incubation stages, when nitrate was reduced, reduction of Fe(III) to Fe(II) occurred. Time-resolved laser-induced fluorescence spectroscopic analysis revealed that most of the added U(VI) was bound in phosphate phases of biotic origin.
  • Contribution to external collection
    Broder J. Merkel, Andrea Hasche-Berger: Uranium, Mining and Hydrogeology, Berlin: Springer Verlag, 2008, 978-3-540-87745-5, 743-752

Publ.-Id: 11332 - Permalink


Study of the Influence of Humic Acid on the Am(III) Sorption onto Kaolinite
Krepelova, A.; Sachs, S.; Geipel, G.; Bernhard, G.;
In order to determine the influence of humic acid (HA) on the sorption of Am(III) onto kaolinite batch experiments were performed ([Am(III)] = 1x10-6 M, [HA] = 0 or 10 mg/L, I = 0.01 M NaClO4, pH = 3-10, solid/solution ratio = 1 or 4 g/L, pCO2 = 10-3.5 atm). In addition to that, laser-induced fluorescence spectroscopy was applied to study Am(III) kaolinite surface complexes in absence and presence of HA. The obtained results show that the presence of humic acid can affect the Am(III) migration under environmentally relevant conditions.
Keywords: Americium, Am(III), Humic acid, Kaolinite, Clay, Sorption, Batch experiments, Laser-induced fluorescence spectroscopy
  • Lecture (others)
    4th RTDC-1 Meeting of FUNMIG, 20.-21.05.2008, Bürgenstock, Switzerland

Publ.-Id: 11331 - Permalink


Quasifree Lambda, Sigma0, and Sigma− electroproduction from 1,2H, 3,4He and carbon
Dohrmann, F.;
A comprehensive study of kaon electroproduction on light nuclei has been conducted in Hall C of the Thomas Jefferson National Accelerator Facility by the E91-016 collaboration. Data were obtained using electron beams of 3.245 GeV impinging on special high density cryogenic targets of 1,2H, 3,4He, as well as on a solid carbon target. Specifically, the measurements on 3,4He are the first performed. Previously, the observation of hypernuclear bound states was discussed [1]. This presentation will give the final results of the data analysis, focussing on the quasifree production cross sections for the Lambda and Sigma hyperons for the various target nuclei [2]. We also derive effective proton numbers from our data and compare these numbers with model calculations. Deviations may indicate possible in-medium modifications of the kaon electroproduction mechanism.

[1] F. Dohrmann et al [E91016 collab.] Phys. Rev. Lett. 93 (2004) 242501
[2] F. Dohrmann et al [E91016 collab.] Phys. Rev. C 76 (2007) 054004
Keywords: electroproduction, quasifree, medium modifications, hyperons
  • Lecture (Conference)
    DPG Frühjahrstagung Darmstadt 2008, 10.-14.03.2008, Darmstadt, Deutschland

Publ.-Id: 11330 - Permalink


Time resolution of radiation hard Resistive Plate Chambers for the CBM experiment at FAIR
Bartos, D.; Caragheorgheopol, G.; Dohrmann, F.; Kämpfer, B.; Kotte, R.; Naumann, L.; Petris, M.; Petrovici, M.; Simion, V.; Stach, D.; Williams, C.; Wüstenfeld, J.;
The Compressed Baryon Matter (CBM) experiment at FAIR/Darmstadt studies highly compressed nuclear matter at moderate temperatures in relativistic heavy-ion collisions. CBM uses rare probes for studying fundamental issues of QCD. Currently the technical design of CBM foresees a time-of-flight wall (TOF) equipped with resistive plate chambers (RPCs) 10 m downstream from the target. The inner part of the TOF covers 50-100 mrad around the beam axis with estimated flux densities of charged particles of ~2·10^4 per s and cm², thus radiation hard detector components are indispensable in the forward direction.

RPC tests were conducted at the superconducting electron linac ELBE at FZ Dresden-Rossendorf using MeV electron beams mimicking GeV minimum ionizing particles for detector studies. The pulse width of ~5 ps of the ELBE beam provides the possibility to use its radio frequency directly as a time reference. ELBE also provides high rates (up to 1 mA beam current).

Conventional timing RPCs with standard float glass electrodes are only efficient up to flux densities of < 1·10^3 per s and cm². Accelerating the charge transport requires electrodes with lower volume resistivity while maintaining the time resolution (< 100 ps).

Timing and rate parameters of various RPCs were tested at ELBE, including conventional RPCs with float glass electrodes, as well as RPC electrodes made of special glasses (silicated) with 3-4 orders of magnitude lower volume resistivity than float glass (10^13 Ohm·cm).

Results are reported with emphasis on alternative electrode materials, i.e. polypropylene material and Pestov glass. The NIPNE group developed a prototype RPC with Pestov glass electrodes (10^10 Ohm·cm) read-out via stripe lines or pads.

Also ceramics electrodes are suggested for high rate timing RPCs. New ceramics material have recently become available for laboratory and prototype tests.

These tests will provide data for a decision on the type of high rate RPCs for CBM at FAIR.
Keywords: Gaseous Detectors, Time-of-flight detectors, high rate detectors, new materials
  • Lecture (Conference)
    IEEE Dresden 2008, 19.-25.10.2008, Dresden, Germany
  • Contribution to proceedings
    IEEE Dresden 2008, 19.-25.10.2008, Dresden, Germany
    Conference Record, 978-1-4244-2715-4

Publ.-Id: 11329 - Permalink


Synthesis of inverted spinel ferrite nanocrystals inside ZnO by ion implantation and post-annealing
Zhou, S.; Potzger, K.; Kuepper, K.; Xu, Q.; Schmidt, H.; Helm, M.; Fassbender, J.ORC
The hybrids of magnets and semiconductors show promising magneto-transport properties, and would enable the development of spin-dependent magneto-electronic and magneto-optic devices [1]. The most well studied system is MnAs/GaAs due to its chemically stable interface and the possibility of epitaxy [2]. Large magneto-resistance and Faraday rotation have been observed in GaAs with MnAs nanoclusters. However the Curie temperature of MnAs is 313 K, and limits its application at high temperatures. Spinel ferrites are a group of materials with similar crystal-structure and rich magnetic as well as electronic properties, e.g. NiFeO and CoFeO, are ferrimagnets with large Neel temperatures. Therefore the hybrids of spinel ferrites with semiconductors would allow versatile possibilities for spin-dependent devices. However the integration of ferrites with semiconductors remains challenging due to the fact that the growth of ferrites requires high temperatures and oxygen environment, which is detrimental to conventional semiconductors like Si and GaAs [3]. In this contribution, we show the possibility to incorporate inverted spinel ferrite nanocrystals with ZnO by ion implantation and post-annealing. Their magnetic and electronic properties were investigated by SQUID and x-ray absorption spectroscopy. These nanocrystals are crystallographically oriented inside ZnO, and show superparamagnetic characteristics. Large positive magneto-resistance has been observed, and we will discuss its origin with respect to ordinary magneto-resistance and to magnetic scattering by nano-ferrites. Our results suggest a new magnet-semiconductor heterostructure with potential application in magneto-electronics and microwave devices [3].

[1] G. Prinz, Science 250, 1092 (1990).
[2] L. Daweritz, Rep. Prog. Phys. 69, 2581 (2006).
[3] Z. Chen et al., Appl. Phys. Lett. 91, 182505 (2007).
Keywords: magnetism, diluted magnetic semiconductors, spinell structures, nanocrystals
  • Poster
    16th International Conference on Ion Beam Modification of Materials, 31.08.-05.09.2008, Dresden, Germany

Publ.-Id: 11328 - Permalink


Tuning coercivity in CoCrPt-SiO2 hard disk material
Strache, T.; Tibus, S.; Springer, F.; Rohrmann, H.; Albrecht, M.; Fassbender, J.ORC
In order to continuously increase the storage capacity of modern computer disk drives and push the superparamagnetic limit to the smallest achievable bit sizes the material used has to fulfill a number of requirements: i) Maximum perpendicular magnetic anisotropy to guarantee thermal stability. Granular CoCrPt-SiO2 films are currently the material of choice. ii) Large remnant magnetization to achieve a good signal to noise ratio when reading the bit information. iii) Moderate coercive fields to allow for the writing of the bit information with the limited write head fields available. In order to increase the storage density, smaller grains with larger magnetic anisotropies are required for thermal stability which are accompanied by large coercive fields which obstruct the writing process. One route to overcome this problem is to independently reduce the coercive field without altering the magnetic anisotropy and the remnant magnetization by tailoring the intergranular exchange.
Ion irradiation and implantation has recently been demonstrated to be a viable tool to modify magnetic properties of thin magnetic films and multilayers [1, 2]. Here we demonstrate that by means of ion implantation of Co and Ne a continuous reduction of the coercive field can be achieved without significant modification of the remaining magnetic parameters. In addition to the magnetization reversal behavior of the entire film investigated by magneto-optic Kerr effect and SQUID magnetometry also the magnetic domain configuration in the demagnetized state is imaged by magnetic force microscopy. Moreover, these studies are supported by micromagnetic simulations which allow to further extract information about the intergranular exchange coupling which is the source of the modified coercive field.

[1] J. Fassbender, D. Ravelosona, Y. Samson, J. Phys. D: Appl. Phys. 37, R179 (2004).
[2] J. Fassbender, J. McCord, J. Magn. Magn. Mater. 320, 579 (2008).
Keywords: magnetism, ion irradiation, magnetic storage, hard disk, coercivity, anisotropy, magnetic domains
  • Lecture (Conference)
    16th International Conference on Ion Beam Modification of Materials, 31.08.-05.09.2008, Dresden, Deutschland

Publ.-Id: 11327 - Permalink


Magnetic microstructures created by local interface mixing
Strache, T.; Fassbender, J.ORC; Grenzer, J.; Möller, W.; Kaltofen, R.; Mönch, I.; McCord, J.
Magnetic micro- and nanostructures are of great interest due to the fundamental physics involved if the dimension is shrunk as well as due to the application potential in storage, sensing and logic devices. For the creation of such structures typically lithography is used in combination with either etching or lift-off processes. In both cases the magnetic element is defined by isolated topographic structures. An alternative approach relies on the local ion irradiation of a magnetic multilayer structure. As a result of the ion irradiation an interfacial mixing between ferromagnetic layers and non-magnetic interlayers is achieved which consequently reduce and finally fully suppress the ferromagnetism. In order to demonstrate this behaviour Ni80Fe20/Ta multilayers with a different number of repetitions are used. The structural and magnetic properties are investigated by x-ray reflectivity and magneto-optic Kerr effect magnetometry as a function of noble gas irradiation fluence and number of multilayer repetitions. The experimental results are accompanied by TRIDYN simulations. In addition magnetic microstructures are created by means of large area ion irradiation through lithographically defined masks. By choosing the irradiation fluence the exchange coupling between the microstrucutres can be switching on and off. The magnetic domain configuration in these elements is imaged by means of Kerr microscopy and magnetic force microscopy. Thus the modified magnetization reversal curves can be interpreted on the basis of the micromagnetic domain structure.
Keywords: magnetism, ion irradiation, magnetic patterning, intermixing, Kerr microscopy
  • Poster
    16th International Conference on Ion Beam Modification of Materials, 31.08.-05.09.2008, Dresden, Germany

Publ.-Id: 11326 - Permalink


Ion beam induced magnetic transformation in layered structures: nonmagnetic to ferromagnetic and vice versa
Dev, B. N.; Fassbender, J.ORC; Grenzer, J.; Schell, N.; Bischoff, L.; Schmidt, B.; Grötzschel, R.; Allenstein, F.; Beddies, G.; McCord, J.
A nonmagnetic to ferromagnetic transformation is observed when a Pt/C multilayer stack (total thickness ~ 60 nm, thickness of individual layers ~ 2 nm) with a small amount of Fe impurity, grown on a glass substrate, is irradiated with 2 MeV Au ions [1]. Using a subnanometer depth resolution technique it was found that ion beam induced preferential migration of Fe from C to Pt layers and the subsequent formation of FePt nanoparticles were responsible for the magnetic transformation [2]. Fe concentration in the C layers decreases exponentially with increasing ion fluence with simultaneous increase of the coercive field in the magnetic hysteresis loop. An example of ion beam induced opposite transformation, namely, ferromagnetic to nonmagnetic, is shown using a Si(5nm)/Ni(10 nm)/Si trilayer system, where ion-beam-induced atomic displacements across the Si/Ni interfaces form a mixed Ni1-xSix layer leading to a ferromagnetic to nonmagnetic transformation. In this case, with increasing ion (30 keV Ga) fluence the coercive field in the hysteresis loop decreases with increasing ion fluence and eventually magnetization is destroyed at a critical fluence. Having identified the critical fluence, a focused ion beam (FIB, 30 keV Ga) was used to fabricate a lateral multistrip pattern in this thin (10 nm) magnetic layer with alternate magnetic/nonmagnetic strips of nanometer dimensions. Magnetooptical Kerr effect microscopy reveals the anisotropy of the magnetic domain structure along and perpendicular to the FIB-patterned strips. In the light of the observed phenomena, future developments in the area of nanotechnology, such as ultrahigh density magnetic storage devices, single-electron spin-valve transistors etc. will be discussed. Some nanoscale structures that can be fabricated using FIB will offer the possibility of exploring new scientific aspects, such as magnons in ordered ferromagnetic spot arrays, in these structures.

[1] B. N. Dev, S. Bera, B. Satpati, D. K. Goswami, K. Bhattacharjee, P. V. Satyam, K. Yamashita, O. M. Liedke, K. Potzger, J. Fassbender, F. Eichhorn and R. Groetzschel,
Microelectronic Engineering 83, 172 (2006).

[2] S. Bera, K. Bhattacharjee, G. Kuri and B. N. Dev
Phys. Rev. Lett. 98, 196103 (2007).
Keywords: magnetism, ion irradiation, magnetic transformation, XRD, Kerr microscopy
  • Poster
    16th International Conference on Ion Beam Modification of Materials, 31.08.-05.09.2008, Dresden, Deutschland

Publ.-Id: 11325 - Permalink


Ga+ ion irradiation-induced changes of magnetic ordering in Pt/Co(3nm)/Pt films
Jaworowicz, J.; Kisielewski, M.; Maziewski, A.; Sveklo, I.; Jamet, J.-P.; Ferre, J.; Mougin, A.; Vernier, N.; Fassbender, J.ORC; Henschke, A.; Bourhis, E.; Gierak, J.
In Pt/Co(d)/Pt ultrathin film structures a spin reorientation transition (SRT) from out-of-plane to in-plane magnetization states is known to occur at a critical Co thickness d=dSRT ~ 1.8nm. For thinner Co thicknesses this SRT can also be forced by ion irradiation. In the present work we demonstrate that also the reverse SRT, i. e. from in-plane to out-of-plane, can be achieved by ion irradiation in certain cases. Therefore, easy-plane magnetized Pt/Co(3nm)/Pt samples were irradiated by 30 keV Ga+ ions with doses D ranging from 1014 to 5x1016 ions/cm2. The ion irradiation induced effects were investigated by polar magnetooptical microscopy, magnetometry and atomic/magnetic force microscopy. At low dose the reverse SRT is observed with a large out-of-plane magnetization component giving rise to a square perpendicular hysteresis loop. Sub-micrometer perpendicular magnetic domain structures either field-induced or in the demagnetized state confirm this new behavior. At higher dose, the easy magnetization direction is turned in-plane again. Topologically, a film swelling effect is first evidenced at low dose, but surface etching dominates at higher dose. Similar effects are also observed under quasi-uniform irradiation performed by scanning a focused ion beam (FIB) on the Pt/Co(3nm)/Pt structure. The results will be also compared to those reported earlier for d < dSRT, where ion irradiation leads to a reduction of the Curie temperature, coercivity and magnetic anisotropy [1,2].
This work was partially supported by EU MC TOK project NanomagLab No MTKD-CT-2004-003177 and EU-RITA program “Centre for Application of Ion Beams in Materials Research” under contract no. 025646. J.J. has benefited of an EC Marie-Curie fellowship (contract MEST CT 2004-51437).

[1] J. Ferré, J.-P. Jamet, in Handbook of Magnetism and Advanced Magnetic Materials, H. Kronmüller, S. Parkin (eds), (2007) John Wiley & Sons, Ltd.
[2] J. Fassbender, J. McCord, J. Magn. Magn. Mat. 320 (2008) 579.
Keywords: magnetism, ion irradiation, FIB, magnetic anisotropy, Kerr microscopy
  • Poster
    16th International Conference on Ion Beam Modification of Materials, 31.08.-05.09.2008, Dresden, Germany
  • Poster
    Louis Neel Colloquim, 30.09.-03.10.2008, La Grande Motte, France

Publ.-Id: 11324 - Permalink


Irradiation induced magnetic patterning of soft-magnetic thin films
McCord, J.; Kaltofen, R.; Quandt, E.; Fassbender, J.ORC
Numerous applications of ferromagnetic materials in magneto-electronics are based on multi-layer thin film technology. For most of the relevant applications the magnetic films are patterned by lithographic processes, which result in isolated magnetic elements. Here, we demonstrate the lateral alteration of magnetic properties of soft-magnetic thin films by ion irradiation. In contrast to traditionally patterned thin films, the interaction within the patterned structure occurs through direct magnetic exchange, resulting in novel effective magnetic properties and magnetization states fundamentally differing from conventionally magnetic thin films.
The method and a summary of ion-induced modifications of fundamental magnetic properties of different materials will be shown on single layer crystalline and amorphous thin films, and multi-layered systems. Examples include laterally modulated saturation polarization as well as locally varying magnetic anisotropy alignment, both resembling anisotropic as well as patterned soft-magnetic film behavior. The scaling behavior for the resulting structures will be discussed and the data will be compared to effects known so far only from multi-layered magnetic layers. Moreover it will be shown, that not only the regular static magnetic behavior, but also the magnetization dynamics of systems can be tuned and laterally modified by ion irradiation.
The local modulation of magnetic properties opens exciting new opportunities to the tuning of the integral properties of soft-magnetic thin films and establishes an additional path to thin film magnetic structures with novel functionality.

J. McCord, R. Schäfer, K. Theis-Bröhl et al., J. Appl. Phys. 97, 10K102 (2005).
J. McCord, J. Fassbender, E. Quandt et al., Appl. Phys. Lett. 89, 162502 (2005).
J. Fassbender, J. McCord, JMMM 320, 579–596 (2008).
J. McCord, L. Schultz, J. Fassbender, Adv. Mater., accepted for publication.
Keywords: magnetism, ion irradiation, ion implantation, Kerr microscopy, exchange spring, magnetic domains
  • Lecture (Conference)
    16th International Conference on Ion Beam Modification of Materials, 31.08.-05.09.2008, Dresden, Germany

Publ.-Id: 11323 - Permalink


Generation of micro/nano-scaled magnetic structures on AISI 304L austenitic stainless steel by ion beam nitriding
Menendez, E.; Martinavicius, A.; Liedke, M. O.; Abrasonis, G.; Fassbender, J.ORC; Sommerlatte, J.; Nielsch, K.; Surinach, S.; Baro, M. D.; Nogues, J.; Sort, J.
Nitriding of austenitic stainless steel 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]. 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 [2].

The influence of the processing temperature and time on the structural and magnetic properties of AISI 304L austenitic stainless steel, after ion beam nitriding, has been investigated by x-ray diffraction (XRD), nuclear reaction analysis (NRA), magneto-optical Kerr effect (MOKE) magnetometry and atomic/magnetic force microscopy (AFM/MFM). Furthermore, periodic arrays of ferromagnetic structures in the micrometer and sub-micrometer range have been prepared after nitriding through either 2000 mesh Cu transmission electron microscopy grids (mesh size of 7.5 x 7.5 µm2, 12.5 µm pitch, 20 µm thickness and 3.05 mm diameter) or self-assembled porous alumina membranes (5 µm thickness), both acting as shadow masks. The local character of the induced ferromagnetism is confirmed by magneto-optical Kerr effect measurements together with magnetic force microscopy imaging.


[1] G. Abrasonis, et al., J. Appl. Phys. 97, 083531 (2005)
[2] O. Öztürk and D.L. Williamson, J. Appl. Phys. 77, 3839 (1995)
Keywords: magnetism, ion beam processing, nitriding, stainless steel, magnetic patterning
  • Poster
    16th International Conference on Ion Beam Modification of Materials, 31.08.-05.09.2008, Dresden, Germany

Publ.-Id: 11322 - Permalink


Direct generation of nanoscale ferromagnetic dots by selective ion irradiation of paramagnetic FeAl alloys
Menendez, E.; Sort, J.; Liedke, M. O.; Strache, T.; Fassbender, J.ORC; Möller, W.; Gemming, T.; Weber, A.; Heyderman, L. J.; Surinach, S.; Deevi, S. C.; Rao, K. V.; Sommerlatte, J.; Nielsch, K.; Baro, M. D.; Nogues, J.
Fe60Al40 (at. %) alloys show an interesting combination of magnetic and structural properties, where atomically ordered Fe60Al40 is paramagnetic at room temperature, whereas disordered Fe60Al40 becomes ferromagnetic [1]. The transformation from paramagnetic B2-phase to the ferromagnetic, A2-phase can be accomplished by means of homogeneous ion irradiation procedures. Furthermore, local ion irradiation procedures (i.e., focused ion beam or ion irradiation through masks) have been also used in order to fabricate periodic arrays of sub-50 nm ferromagnetic structures embedded in a paramagnetic matrix. Due to the low fluences used, this method does not induce any roughening of the surface, leading to topographically featureless dots. The fabricated entities exhibit a range of magnetic properties depending on the size and shape, which were investigated by means of magneto-optical Kerr effect magnetometry, while the local character of the induced ferromagnetism was examined by magnetic force microscopy. Interestingly, when the patterned sheets are annealed at sufficiently high temperatures, the ferromagnetic properties are removed due to the annealing-induced atomic reordering. Hence, these methods may lead to a novel type of patterned recording media free from tribological and exchange coupling effects. Moreover, these approaches can be easily extrapolated to a variety of other systems exhibiting disorder-induced magnetism.

[1] J. Nogués et al., Phys Rev. B Phys. Rev. B 74, 024407 (2006)
Keywords: magnetism, ion irradiation, FIB, magnetic patterning, binary alloys, disordering
  • Invited lecture (Conferences)
    16th International Conference on Ion Beam Modification of Materials, 31.08.-05.09.2008, Dresden, Germany

Publ.-Id: 11321 - Permalink


Influence of Cr-ions on the magnetic behaviour of FeCo film
Gupta, R.; Ansari, R.; Khandelwal, A.; Fassbender, J.ORC; Gupta, A.
Implantation of Cr-ions in Fe70Co30 thin film have been performed to modify its structural and magnetic properties. From the XRD results, the lattice constant as well as the grain size of the film is increasing with the ion fluence. 1 X 1017 ions/cm2 Cr-ions reduces the coercivity of the film from 140(3) Oe to 44(3) Oe. Coercivity of the film follows the exponential decay as a function of Cr-ions fluence. 35 keV (projectile range 13.5 nm) and 100 keV Cr-ions (projectile range 34.3 nm) have been used to understand the effects of magnetic Cr-ions and the effects of ballistic collision cascade on the MOKE signal. Similar changes on the coercivity behaviour of the film implanted with these two energies have been observed. It appears that the implantation process creates a solid solution of Cr in FeCo without any other additional treatment in the film. After 5 X 1016 Cr-ions, film exhibit four fold magnetic anisotropy.
Keywords: magnetism, ion implantation, magneto-optic kerr effect, magnetic anisotropy
  • Nuclear Instruments and Methods in Physics Research B 266(2008), 1407-1410

Publ.-Id: 11320 - Permalink


Two-fold origin of the deformation-induced ferromagnetism in bulk Fe60Al40 (at-%) alloys
Menendez, E.; Sort, J.; Liedke, M. O.; Fassbender, J.ORC; Surinach, S.; Baro, M. D.; Nogues, J.
The transition from the atomically ordered B2-phase to the chemically disordered A2-phase and the concomitant deformation-induced ferromagnetism have been investigated in bulk polycrystalline Fe60Al40 (at.%) alloys subjected to compression processes. A detailed correlation between structural, magnetic and mechanical properties reveals that the generated ferromagnetism depends on the stress level but is virtually independent of the loading rate. The mechanisms governing the induced ferromagnetism also vary as the stress level is increased. Namely, in the low-stress regime both lattice cell expansion and atomic intermixing play a role in the induced ferromagnetic behavior. Conversely, lattice expansion seems to become the main mechanism contributing to the generated ferromagnetism in the high-stress regime. Furthermore, a correlation is also observed between the order-disorder transition and the mechanical hardness. Hence, a combination of magnetic and mechanical measurements can be used, in synergetic manner, to investigate this deformation-induced phase transition.
Keywords: magnetism, binary alloys, ordering, disordering, ball milling, lattice expansion
  • Open Access LogoNew Journal of Physics 10(2008), 103030

Publ.-Id: 11319 - Permalink


Patterning of magnetic structures on austenitic stainless steel by local ion beam nitriding
Menendez, E.; Martinavicius, A.; Liedke, M. O.; Abrasonis, G.; Fassbender, J.ORC; Sommerlatte, J.; Nielsch, K.; Surinach, S.; Baro, M. D.; Nogues, J.; Sort, J.
Periodic arrays of ferromagnetic structures with micrometer and sub-micrometer lateral sizes have been prepared at the surface of a paramagnetic austenitic stainless steel by means of ion beam nitriding through different types of shadow masks (such as transmission electron microscopy grids or self-assembled porous alumina membranes). This method takes advantage of the formation of the ferromagnetic supersaturated nitrogen solid solution γN phase (i.e., expanded austenite) upon nitriding at moderate temperatures. The local character of the induced ferromagnetism is confirmed by magneto-optical Kerr effect measurements together with magnetic force microscopy imaging. Furthermore, the influence of the nitriding temperature and time on the induced ferromagnetic and structural properties has been analyzed.
Keywords: Magnetism, Ion-beam processing; X-ray diffraction; Austenitic steels; Interstitial diffusion; Magnetic patterning

Publ.-Id: 11318 - Permalink


Dynamic interaction between vortices, antivortices and holes in domain walls investigated by means of time resolved Photoemission Electron Microscopy (PEEM)
Kuepper, K.; Wintz, S.; Buess, M.; Raabe, J.; Quitmann, C.; Fassbender, J.ORC
In this work we study the interaction of vortex cores with either holes in domain walls of Landau structures or other vortices and antivortices, which are also interconnected through the adjacent domain walls of a single cross-tie structure.
During the last few years the investigation of magnetic vortices and their dynamic properties has attracted great attention due to the fundamental interest in the physics of solitons and since they might be used as non volatile memory devices in future applications, e. g. [1,2]. One striking feature of magnetic vortices is that the cores are attracted and can be trapped by artificial defects. If more than one of such defects are created a switching between different vortex core trapped states, which might serve as discrete levels in a multivalent memory device, can be achieved. We report the imaging of the magnetic excitation spectrum in presence of holes, fabricated by focused ion beam milling, in the magnetic domains and domain walls of Landau structures by means of x-ray magnetic circular dichroism photoemission electron microscopy (XMCD-PEEM). The vortex core in the center of the structure is not modified by ions, here we investigate the interaction of unmodified vortex cores with holes far away (> 1 Mikrometer) in the domain walls and the domains of Landau structures. Due to the very high lateral and temporal resolution the magnetization dynamics and the corresponding Eigen modes (Fig. 1), which are characteristic for the vortex-hole interaction, are investigated in detail [3]. Analyzing the vortex movement unravels an acceleration of the vortex gyrotropic mode if holes are present in the middle of domain walls. The presence of holes in the middle of domains has no significant influence on the vortex speed. The experimental results are compared to micromagnetic simulations.

References:
[1] S. B. Choe et al., Science 304, 420 (2004), J. Raabe et al., Phys. Rev. Lett. 94, 217204 (2005).
[2] B. van Waeyenberge et al., Nature 444, 461 (2006)
[3] K. Kuepper et al., manuscript in preparation.
[4] K. Kuepper et al., Phys. Rev. Lett. 99, 167202 (2007)
Keywords: magnetism, magnetization dynamics, vortex, antivortex, defects, time-resolved, magnetic imaging
  • Invited lecture (Conferences)
    IEEE International Magnetics Conference - Intermag 2008, 04.-08.05.2008, Madrid, Spain
  • Invited lecture (Conferences)
    Workshop on high temporal and spatial resolution studies of magnetic nanostructures, 27.06.-02.07.2008, Augustow, Poland

Publ.-Id: 11317 - Permalink


Ga+ ion irradiation-induced out-of-plane magnetization in Pt/Co(3nm)/Pt films
Jaworowicz, J.; Kisielewski, M.; Maziewski, A.; Sveklo, I.; Jamet, J.-P.; Ferre, J.; Mougin, A.; Vernier, N.; Fassbender, J.ORC
Ion beam irradiation under weak or moderate fluence allows to modify and even control the magnetic properties of thin film structures [1–2]. So, this method stands now as an elegant technique for magnetic nanopatterning [3].Spin reorientation transition form in-plane to out-of-plane state in Pt/Co/Pt film with cobalt thickness 3nm after irradiation by 30 keV Ga+ ions with doses of 0.5 x 1015 and 1015 ions/cm2 was observed. Experiments were made with magneto-optical base microscopy and magnetic force microscopy.

[1] C. Chappert, H. Bernas, J. Ferré, V. Kottler, J.-P. Jamet, Y. Chen, E. Cambril, T. Devolder, F. Rousseaux, V. Mathet, H. Launois, Science 280 (1998) 1919.
[2] J. Fassbender, J. McCord, J. Magn. Magn. Mat. 320 (2008) 579
[3] J. Ferré, J.-P. Jamet, in Handbook of Magnetism and Advanced Magnetic Materials, H. Kronmüller, S. Parkin (eds), (2007) John Wiley & Sons, Ltd, p 1710
Keywords: magnetism, ion irradiation, perpendicular anisotropy, Kerr microscopy, MFM
  • Poster
    IEEE International Magnetics Conference - INTERMAG 2008, 04.-08.05.2008, Madrid, Spain

Publ.-Id: 11316 - Permalink


Single Pi- production in np collisions for excess energies up to 90 MeV
Abdel-Bary, M.; Brinkmann, K.-T.; Clement, H.; Doroshkevich, E.; Dshemuchadse, S.; Erhardt, A.; Eyrich, W.; Freiesleben, H.; Gillitzer, A.; Jäkel, R.; Karsch, L.; Kilian, K.; Kuhlmann, E.; Möller, K.; Morsch, H. P.; Naumann, L.; Paul, N.; Pizzolotto, C.; Ritman, J.; Roderburg, E.; Schroeder, W.; Schulte-Wissermann, M.; Sefzick, T.; Teufel, A.; Ucar, A.; Ullrich, W.; Wintz, P.; Wüstner, P.; Zupranski, P.;
The quasifree reaction np -> pppi- was studied in a kinematically complete experiment by bombarding a liquid-hydrogen target with a deuteron beam of momentum 1.85GeV/c and analyzing the data along the lines of the spectator model. In addition to the three charged ejectiles the spectator proton was also detected in the large-acceptance time-of-flight spectrometer COSY-TOF. It was identified by its momentum and flight direction thus yielding access to the Fermi motion of the bound neutron and to the effective neutron 4-momentum vector Pn which differed from event to event. A range of almost 90MeV excess energy above threshold was covered. Energy-dependent angular distributions, invariant-mass spectra as well as fully covered Dalitz plots were deduced. Sizeable pp FSI effects were found as were contributions of p and d partial waves. In comparison with existing literature data the results provide a sensitive test of the spectator model. The behavior of the elementary cross-section σ01 close to threshold is discussed in view of new cross-section data.
Keywords: 13.75.Cs - Nucleon-nucleon interactions (including antinucleons, deuterons, etc.). 25.10.+s - Nuclear reactions involving few-nucleon systems.
  • European Physical Journal A 36(2008), DOI: 10.1140/epja/i2007-10543-x

Publ.-Id: 11315 - Permalink


Radiation Source ELBE – Electromagnetic Radiation for Fundamental Research
Justus, M.;
Since 2003, the Radiation Source ELBE at the Research Centre Dresden-Rossendorf (FZD) delivers infrared light, X-rays and Bremsstrahlung of high intensity for fundamental research. The experimental proposals are associated with the FZD programs “Advanced Materials Research”, “Cancer Research” as well as “Nuclear Safety Research and come from the institute itself, as well as from international guests.
The design and the technical implementation of the 40 MeV superconducting electron beam linear accelerator are explained with regard to the generation of the different types of secondary radiation. The article also highlights beam diagnostics and optimization of the beam quality and availability with respect to the different demands on its main properties (energy, bunch charge, emittance, time structure) and the ongoing installation of facility parts.
Keywords: ELBE
  • Lecture (Conference)
    DPG Frühjahrstagung Freiburg 08, 03.-07.03.2008, Freiburg, Deutschland

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Publ.-Id: 11314 - Permalink


Die numerische Auswertung von Kleinwinkelstreukurven
Küchler, R.;
Aus dem Streubild der Kleinwinkelstreuung kann im Allgemeinen, die die Streuvertei-lung erzeugende Struktur nicht eindeutig rekonstruiert werden. Die Ursache dafür wird erörtert und die damit verbundenen Einschränkungen bei der rechnerischen Auswertung der Streukurven an Beispielen veranschaulicht. Dies geschieht an Streukurven, die mit bekannten Größenverteilungen berechnet wurden. Weiterhin wird untersucht, welche Fit- Ansätze sich zur Auswertung der Kleinwinkelstreuexperimente am besten eignen. Als Fit- Ansätze wurden Reihenentwicklungen nach Trigonometrischen- und Polynomfunkti-onen und eine theoretisch motivierte Funktion verwendet. Neben dem entscheidenden Vergleich mit der Streukurve der Ausgangsfunktion werden die Ergebnisse auch den Rechnungen gegenübergestellt, die mit der weit verbreiteten Glatter- Methode erzielt werden.
Keywords: small-angle scattering, data evaluation, indirect fourier transformation, density distribution
  • Open Access LogoWissenschaftlich-Technische Berichte / Forschungszentrum Dresden-Rossendorf; FZD-496 2008

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Publ.-Id: 11313 - Permalink


First CoMFA Characterization of Vesamicol Analogs as Ligands for the Vesicular Acetylcholine Transporter
Szymoszek, A.; Wenzel, B.; Scheunemann, M.; Steinbach, J.; Schüürmann, G.;
Vesamicol derivatives are promising candidates as ligands for the vesicular acetylcholine transporter (VAChT) to enable in vivo imaging of cholinergic deficiencies if applied as positron emission tomography radiotracers. So far, optimization of the binding affinity of vesamicol-type ligands was hampered by the lack of respective quantitative structure–activity relationships. We developed the first quantitative model to predict, from molecular structure, the binding affinity of vesamicol-type ligands toward VAChT employing comparative molecular field analysis (CoMFA) for a set of 37 ligands, covering three different structural types (4-phenylpiperidine, spiro, and tropan derivatives of vesamicol). The prediction capability was assessed by leave-one-out cross-validation (LOO) and through leaving out and predicting 50% of the compounds selected such that both the training and the prediction sets cover almost the whole range of experimental data. The statistics indicate a significant prediction power of the models (q2 (LOO) = 0.66, q2 (50% out) = 0.59–0.74). The discussion includes detailed analyses of CoMFA regions critical for ligand−VAChT binding, identifying structural implications for high binding affinity.

Publ.-Id: 11312 - Permalink


A population balance approach for polydispersed bubbly flows considering size dependent bubble forces
Krepper, E.; Frank, T.; Lucas, D.; Prasser, H.-M.; Zwart, P.;
A generalized inhomogeneous Multiple Size Group (MUSIG) Model based on the Eulerian modeling framework was developed in close cooperation of ANSYS-CFX and Forschungszentrum Dresden-Rossendorf and implemented into CFX-10. By simulating a poly-dispersed gas-liquid two-phase flow, the mass exchanged between bubble size classes by bubble coalescence and bubble fragmentation as well as the momentum exchange due to bubble size dependent bubble forces have to be considered. Particularly the lift force has been proven to play an important role for establishing a certain bubble size distribution dependent flow regime.
The derived model has been validated against experimental data from the TOPFLOW test facility at the Forschungszentrum Dresden-Rossendorf (FZD). The wire-mesh technology measuring local gas volume fractions, bubble size distributions and velocities of gas and liquid phases was applied. Numerous tests investigating air-water flow and steam-water flow at saturation conditions in vertical pipes having a length up to 8 m and a diameter up to 200 mm were performed and used for model validation. Furthermore in order to check the model framework for a more complex flow situation, further experiments on the flow field around a half moon shaped asymmetric obstacle were performed and the flow conditions were simulated by applying the inhomogeneous MUSIG model in direct comparison.
The paper describes the main concepts of the CFD model approach and presents model validation and application cases. The inhomogeneous MUSIG model approach was shown to be able to describe bubbly flows with higher gas content. Particularly the separation phenomenon of small and large bubbles, which was proven to be a key phenomenon for the establishment of the corresponding flow regime, is well described. Weaknesses in this approach can be attributed to the characterization of bubble coalescence and bubble fragmentation, which must be further investigated.
Keywords: bubbly flow, CFD, non-drag forces, bubble breakup, bubble coalescence, population balance, validation
  • Lecture (Conference)
    6th International Conference on COMPUTATIONAL FLUID DYNAMICS in the Oil & Gas, Metallurgical and Process Industries, 10.-12.06.2008, Trondheim, Norway
  • Contribution to proceedings
    6th International Conference on COMPUTATIONAL FLUID DYNAMICS in Oil & Gas, Metallurgical and Process Industries, 10.-12.06.2008, Trondheim, Norway

Publ.-Id: 11311 - Permalink


A study of uranium phosvitin complexation using ATR FT-IR and EXAFS spectroscopy
Li, B.; Raff, J.; Rossberg, A.; Foerstendorf, H.;
Phosvitin is a highly water soluble 34 kDa protein containing 10 % (w/w) phosphate groups. It serves as an ideal model for the investigation of the interaction of U(VI) with phosphorylated proteins by attenuated total reflection Fourier-transform infrared (ATR FT-IR) spectroscopy and EXAFS spectroscopy.
In our study, phosvitin and its complex with U(VI) were first studied in aqueous solution at various pH values by ATR FT-IR. In order to understand the inter-atomic coordination of the U(VI) to the functional groups of the protein, in particular to phosphate groups, the samples containing U(VI) phosvitin complex with different U(VI) concentrations were additionally investigated by EXAFS spectroscopy.
Different protonated states of phosphate groups on the protein have been first identified by infrared spectra of phosvitin in solution at different pH. Comparing the spectra with those of inorganic phosphate solutions, it is obvious that at pH 4 the phosphate groups appear as dihydrogen phosphate, and at pH 8 as hydrogen phosphate.
Upon the adsorption of uranium onto phosvitin the protein is irreversible denatured. Infrared spectra of the protein, which were denatured thermally in the absence of U(VI) or denatured by other bivalent metal ions, recorded at pH 4 demonstrate that deprotonation occurs during the protein denaturation. Among those spectra, the U(VI) phosvitin complexes with lower U(VI) concentrations (10−4 M, and 10−5 M) show a unique peak at or even lower than 918 cm−1, while this peak appears at 925 cm−1 for the complex with higher U(VI) concentration (10−3 M). As the characteristic νas(UO22+) mode representing a U(VI) complexation to carboxylic groups appears at 923 cm−1 on the IR spectra, the discovered unique peak indicates coordination of the U(VI) predominately to phosphate groups of the phosvitin.
The EXAFS spectra of the U(VI) phosvitin complex are in good agreement to the spectra of other organic U(VI) phosphate complexes confirming the results from IR spectroscopy. The formation of a U(VI) complex, which is similar to the so-called “Feldman complex” is discussed.
Keywords: Phosvitin, uranium, phosphorelated protein, ATR FT-IR, EXAFS
  • Contribution to proceedings
    BioMetals 2008, 14.-18.07.2008, Santiago de Compostela, Spain
  • Poster
    Biometals 2008, 14.-18.07.2008, Santiago de Compostela, Spain

Publ.-Id: 11310 - Permalink


MULTIMAG - A MULTIpurpose MAGnetic system for physical modelling in magnetohydrodynamics
Pal, J.; Cramer, A.; Gundrum, T.; Gerbeth, G.;
At laboratory scales, liquid metal model experiments are an important tool to understand the details of the flow structure and the transport properties of flows occurring in real-scale facilities, as well as to validate the multitude of numerical codes for flow simulations. Our MULTIpurpose MAGnetic field system facility is based on a compact coil system to investigate the influence of different magnetic fields on electrically conducting fluids. Several features distinguish MULTIMAG from other systems: (i) With its large experimental volume of H = 400 mm and D = 365 mm industrially relevant parameter can be achieved. (II) Due to the absence of any ferromagnetic materials, the possibility of linear superposition of different magnetic field types (rotating, traveling, pulsating, DC-homogen and -cusp) exists. (III) Special developed current sources allow arbitrary waveforms for each of the field types in any phase relation. Besides the main aim to describe MULTIMAG, the present paper instances results of performed flow measurements.
Keywords: Magnetohydrodynamics, Stirring device, Tailored magnetic fields
  • Flow Measurement and Instrumentation 20(2009), 241-251

Publ.-Id: 11309 - Permalink


Non-covalent interactions between nucleosides and molecular clips – comparison of phosphate, phosphonate and sulphate containing clips
Raditzky, B.;
Water-soluble clips are possible molecules to study the weak, non-covalent interactions, responsible for many biological processes. The association between nucleosides and sulphate containing clips, with naphthalene or anthracene sidewalls, has been studied by time-resolved laser-induced fluorescence spectroscopy with ultrafast pulses (fs-TRLFS). The determined association constants for the 1:1 complexes range from log Ka = 3.9 – 4.2. The measured spectra assumes the appearance of excited state species.
Keywords: moleculare clips, nucleosides, sulphate clips, fs-TRLFS, association
  • Lecture (Conference)
    5th SUPRAPHONE/4th WG Meeting COST D31, 29.-31.05.08, Prague, Czech Republic

Publ.-Id: 11308 - Permalink


Ion bombardment of shape memory alloy (SMA) Ni-Ti films
Martins, R. M. S.; Schell, N.; von Borany, J.; Mücklich, A.; Siva, R. J. C.; Mehesh, K. K.; Braz Fernandes, F. M.;
Ni-Ti films were deposited by magnetron cosputtering using a chamber installed into the six-circle goniometer of the Rossendorf BeamLine at ESRF. The in-situ XRD studies enable us to identify different steps of the structural evolution during growth and annealing. The use of diverse type of substrates and the effect of the application of a bias voltage to the substrate during film deposition were major tools in this study. When a negative bias voltage is applied, it causes a higher energetic ion bombardment of the growing film, resulting in an enhanced surface-atom mobility, but at sufficiently high voltage, leads to defect formation. Cross-sectional TEM and SEM micrographs have shown a change in the morphology of the films linked with different levels of bias voltages (0, -45 and -90V in this study). The transformation behaviour of the sputtered Ni-Ti films (as shown by electrical resistivity measurements) is influenced by the energy of the bombarding ions. The microstructure details resulting from the deposition using different bias values are discussed.
Additionally, it has been commissioned an ion gun allowing post-deposition ion irradiation or ion bombardment during sputter deposition. In this first series of experiments, a Ni-Ti film was irradiated with He ions after deposition (without exposing the film to the atmosphere, i.e. reduced surface oxide formation) thus modifying deliberately the microstructure of the film locally. A layer of approximately 50% of the thickness of the film was selectively removed at the irradiated region (6 x 6 mm²).
This type of studies will be very useful for the easier design and miniaturization of Ni-Ti films based devices in the field of micro-electro-mechanical systems (MEMS).
Keywords: thin films, shape memory alloy, ion irradiation, X-ray studies, ROBL
  • Lecture (Conference)
    Microscience 2008, 23.-26.06.2008, London, United Kingdom

Publ.-Id: 11307 - Permalink


Synchronized force and PIV measurements on an electromagnetically forced separated flow
Cierpka, C.; Weier, T.; Gerbeth, G.;
Periodic addition of momentum by wall--parallel electromagnetic forces has a strong influence on the separated region of a stalled airfoil. The controlled flow possesses typically a small number of relatively large vortices, which are believed to be related to the control mechanism.
In the present paper synchronized force and particle image velocimetry measurements of the excited flow at a NACA 0015 (\alpha = 20^{\circ}, Re = 1\cdot10^{5}) will be presented.
Keywords: flow separation control, PIV, NACA0015
  • Lecture (Conference)
    ICTAM2008 - International Congress of Theoretical and Applied Mechanics, 24.-30.08.2008, Adelaide, Australia
  • Contribution to proceedings
    ICTAM2008 - International Congress of Theoretical and Applied Mechanics, 25.08.-29.09.2008, Adelaide, Australia, 978-0-9805142-1-6

Publ.-Id: 11306 - Permalink


Was misst die „Perfusion-CT“?
van den Hoff, J.; Hietschold, V.; Abramyuk, A.; Abolmaali, N.; Kotzerke, J.;
Ziel/Aim:
Dynamische CT-Untersuchungen nach Kontrastmittelgabe (KM) bilden die Grundlage der als „Perfusion-CT“ bezeichneten Quantifizierungsverfahren, welche zunehmend zur Bewertung der Gewebeperfusion genutzt werden. Diese Ansätze finden z.Zt. v.a. Beachtung bei onkologischen Untersuchungen an PET/CT-Geräten, um simultan Informationen zu Tumorstoffwechsel (PET)
und -perfusion (CT) zu erhalten. Ziel dieser Arbeit war eine Analyse der Aussagekraft der verwendeten Modelle unter Beachtung messtechnisch gegebener Randbedingungen.

Methodik/Methods:
Zwei Modelle wurden betrachtet: 1. das in der Perfusion-CT als Patlak-Modell bezeichnete, 2. die adiabatische Lösung des „tissue homogeneity“ Modells (vgl. z.B. [2]). Aus den Lösungen der Modellgleichungen wurden Gewebeantwortkurven berechnet und im Hinblick auf Parameteridentifizierbarkeit und korrekte Parameterinterpretation analysiert.

Ergebnisse/Results:
Der als „Patlak-Modell“ bezeichnete Ansatz ist identisch mit einem irreversiblen 1-Kompartment-Modell zzgl. eines Blutvolumenterms, welches auf die frühe Phase des KM-Transits angewandt wird. Eine Analyse verfügbarer Daten (z.B. [1)) zeigt, dass die allgemein als Perfusion interpretierte Steigung K des entsprechenden Patlak-Plots numerisch typischerweise um den Faktor 5-10 von realistischen Perfusionswerten abweicht. Wir interpretieren dies dahingehend, dass dieser Parameter, welcher dem unidirektionalen KM-Transport in den Extravasalraum entspricht, i.a. unkorreliert zur Gewebeperfusion ist, da die effektive Extraktion des KM sehr klein ist (typischerweise kleiner als etwa diejenige von FDG). Vielmehr entspricht dieser Parameter eher dem PS-Produkt des KM im Zielgewebe. Das „tissue homgeneity“ Modell enthält die Perfusion explizit als freien Parameter. Die Quantifizierung setzt jedoch voraus, dass die Boluspassage durch das Kapillarbett mit so hoher zeitlicher Auflösung erfasst wird, dass diese vom Zeitverhalten im arteriellen Blut unterscheidbar bleibt. Dies erscheint aufgrund der beschränkten statistischen Genauigkeit und verschiedener systematischer Fehlerquellen (wie Bewegungsartefakten) praktisch kaum möglich.

Schlussfolgerungen/Conclusions:
Der Begriff Perfusion-CT suggeriert die Fähigkeit, die Perfusion aus der Gewebediffusion von Kontrastmitteln analog zum Einsatz diffusibler Tracer in der PET bewerten zu können. Diese Fähigkeit ist aber im Allgemeinen nicht gegeben. Eine kritische Bewertung der Aussagekraft des Verfahrens, namentlich im Hinblick auf den Einsatz an PET/CT-Geräten bei onkologischen Fragestellungen erscheint dringend geboten.

Literatur/References:
(1) Ng, QS et al.: „Lung cancer perfusion at multi-detector row CT: reproducibility of whole tumor quantitative measurements.“, Radiology 239(2), pp. 547-53 (2006).
(2) Stewart et al.: „Correlation between hepatic tumor blood flow and glucose utilization in a rabbit liver tumor model.“, Radiology 239(3), pp. 740-50 (2006).
  • Lecture (Conference)
    46. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, 23.-26.04.2008, Leipzig, Germany
  • Abstract in refereed journal
    Nuklearmedizin 47(2008)2, A60

Publ.-Id: 11305 - Permalink


Vergleich einer 2D- und 3D-basierten ROI-Auswertung beim F-18-DOPA-Hirn-PET in einem Normalkollektiv
Oehme, L.; Hofheinz, F.; Wolz, M.; Pötzsch, C.; van den Hoff, J.; Kotzerke, J.;
Ziel/Aim:
Die in der Parkinsondiagnostik relevanten Strukturen, Nucleus caudatus und Putamen, sind komplexe dreidimensionale Strukturen. Ziel der Untersuchung war es, die Ergebnisse der bisherige 2D-basierte ROI-Auswertung (CAPP-Software, Siemens/CTI) mit einer ROI-Auswertung im 3D-Datensatz (Softwarepaket ROVER, ABX Radeberg) zu vergleichen.

Methodik/Methods:
Ausgewertet wurden neun F-18 -DOPA-Hirn-PET-Datensätze gesunder Kontrollpersonen (positives BfS-Gutachten und Ethikvotum). 60 min nach 150 mg Carbidopa per os sowie nach 10 min Transmissionsmessung erfolgte die dynamische Akquisition über 90 min mit Injektion von 185 MBq F-18-DOPA i.v. (ECAT EXACT HR+, Siemens/CTI). Die Auswertung erfolgte in einem Pseudo-2D-Verfahren (Summenbild 10-90min p.i., Ausrichtung Putamen horizontal, Addition von 4 Schichten auf Höhe von Nucl. Caudatus und Putamen, Positionierung von ROIs vordefinierter Größe und Anzahl über Nucl. Caudatus, Putamen, Referenzgewebe occipital) und in einem 3D-Datensatz (freie Positionierung o.g. ROIs vordefinierter Größe und Anzahl in allen 3 Raumebenen). Die Dopamin-Einstromraten wurden mittels Patlak-Analyse bestimmt. Beide Auswerteverfahren wurden verblindet von zwei Untersuchern ausgeführt. Verglichen wurden die Abweichungen innerhalb einer Auswertemethode zwischen den Untersuchern (U1, U2) sowie die Abweichungen zwischen den zwei Auswertemethoden (2D, 3D).

Ergebnisse/Results:
Die Auswertung mit der 3D-Methode war schneller und wurde als einfacher empfunden. Weder innerhalb einer Auswertemethode zwischen den 2 Untersuchern noch zwischen den 2 Auswertemethoden eines Untersuchers waren signifikante Unterschiede zu finden. Über das Kollektiv gemittelt betrugen die Einstromraten (1/min, m+/-sd) für U1-2D; U2-2D; U1-3D; U2-3D: Nucl. Caudatus rechts 0,0181+/-0,0010; 0,0174+/-0,0018; 0,0175+/-0,0022; 0,0174+/-0,0017; Nucl. Caudatus links 0,0185+/-0,0013; 0,0180+/-0,0019; 0,0179+/-0,0013; 0,0183+/-0,0020; Putamen rechts 0,0185+/-0,0006; 0,0180+/-0,0018; 0,0185+/-0,0013; 0,0185+/-0,0017; Putamen links 0,0185+/-0,0013; 0,0180+/-0,0018; 0,0182+/-0,0018; 0,0183+/-0,0015. Die relativen Abweichungen (Differenz/Summe) liegen für alle Paarvergleiche jeweils (gemittelt über alle ROIs) innerhalb +/-2 % (sd < 5 %), allerdings gibt es auch Ausreißer mit Unterschieden größer als +/- 10 %.

Schlussfolgerungen/Conclusions:
Die 2D- als auch die 3D-basierte Auswertung mittels Standard-ROIs definierter Anzahl und Größe lieferten in diesem Normalkollektiv vergleichbare Ergebnisse, wobei die 3D-Methode einen geringeren Zeitbedarf erfordert und als einfacher empfunden wird. In einem weiteren Schritt werden beide Auswertemethoden auf Datensätze von Patienten mit M. Parkinson mit unterschiedlicher Krankheitsintensität angewendet, um die Variabilität der Ergebnisse in Abhängigkeit von Auswertemethode und Untersucher abschätzen zu können.
  • Poster
    46. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, 23.-26.04.2008, Leipzig, Germany
  • Abstract in refereed journal
    Nuklearmedizin 47(2008)2, A108

Publ.-Id: 11304 - Permalink


Determination of harmonic and pulsed eddy current distributions in a liquid metal
Forbriger, J.; Galindo, V.; Gerbeth, G.; Stefani, F.;
The spatio-temporal distribution of harmonic and pulsed eddy currents in the liquid metal alloy GaInSn positioned above an excitation coil is 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. Deformations of the eddy current distribution due to a non-conducting ring immersed into the liquid metal are measured and compared with numerical results.
  • Contribution to proceedings
    7th International PAMIR Conference on Fundamental and Applied MHD, 08.-12.09.2008, Presqu´île de Giens, France
    Proceedings of the 7th International PAMIR Conference on Fundamental and Applied MHD, Reims: Universite de Reims Champagne-Ardenne, 809-813
  • Lecture (Conference)
    7th International PAMIR Conference on Fundamental and Applied MHD, 08.-12.09.2008, Presqu´île de Giens, France

Publ.-Id: 11303 - Permalink


Constraining the geodynamo by sequences of field reversals
Fischer, M.; Gerbeth, G.; Stefani, F.;
Using a spherically symmetric mean field dynamo model with a quenched helical turbulence parameter alpha under the influence of noise and external periodic forcing we try to constrain its essential parameters by typical features of field reversal. Our results indicate that the geodynamo works in a highly supercritical state, that the relative strength of the periodic forcing due to the Milankovic cycle of the Earth’s orbit eccentricity is approximately 15 per cent of the general dynamo strength, and that the magnetic diffusion time is significantly reduced in comparison with the diffusion time resulting from the molecular conductivity.
  • Contribution to proceedings
    7th International PAMIR Conference on Fundamental and Applied MHD, 08.-12.09.2008, Presqu´île de Giens, France
    Proceedings of the 7th International PAMIR Conference on Fundamental and Applied MHD, Reims: Universite de Reims Champagne-Ardenne, 225-229
  • Lecture (Conference)
    7th International PAMIR Conference on Fundamental and Applied MHD, 08.-12.09.2008, Presqu´île de Giens, France

Publ.-Id: 11302 - Permalink


Liquid metal experiments on the helical magnetorotational instability
Stefani, F.; Gerbeth, G.; Gundrum, T.; Szklarski, J.; Rüdiger, G.; Hollerbach, R.;
The magnetorotational instability (MRI) plays an essential role in the formation of stars and black holes. By destabilizing hydrodynamically stable Keplerian flows, the MRI triggers turbulence and enables outward transport of angular momentum in accretion discs. We present the results of a liquid metal Taylor-Couette experiment under the influence of helical magnetic fields that show typical features of MRI at Reynolds numbers of the order 1000 and Hartmann numbers of the order 10. Particular focus is laid on an improved experiment in which split end caps are used to minimize the Ekman pumping.
  • Contribution to proceedings
    7th International PAMIR Conference on Fundamental and Applied MHD, 08.-12.09.2008, Presqu´île de Giens, France
    Proceedings of the 7th International PAMIR Conference on Fundamental and Applied MHD, Reims: Universite de Reims Champagne-Ardenne, 97-101
  • Lecture (Conference)
    7th International PAMIR Conference on Fundamental and Applied MHD, 08.-12.09.2008, Presqu´île de Giens, France
  • Magnetohydrodynamics 45(2009)2, 135-143

Publ.-Id: 11301 - Permalink


Synthese und radiopharmakologische Charakterisierung von Kohlenstoff-11 markierten Chromenderivaten als neuartige nicht-steroidale Liganden für den Glucocorticoidrezeptor (GR)
Steiniger, B.; Bergmann, R.; Pietzsch, J.; Wüst, F.;
Ziel/Aim:
Glucocorticoidrezeptoren (GR) nehmen innerhalb der Hypothalamus-Hypophysen-Nebennieren (HHN)-Achsenregulation eine wichtige Rolle ein. Störungen dieses wichtigen neuroendokrinen Regelsystems sind charakteristisch für verschiedene neuropsychiatrische Erkrankungen, wie z.B. Depression [1]. Ziel der vorliegenden Arbeit war die Entwicklung von Radiotracern für die Darstellung von GR im Gehirn mittels PET. Dabei sollten besonders verschiedene GR-bindende Chromenderivate als neueuartige nicht-steroidale GR-Liganden mit 11C markiert und radiopharmakologisch charakteri-siert werden.

Methodik/Methods:
Ausgehend von chromenbasierten Sulfonamiden wurden verschiedene nicht-steroidale Verbindungen als Liganden für den GR synthetisiert. Die Markierung der Desmethyl-Vorstufen erfolgte in einem automatisierten Synthesemodul über eine regioselektive O-Methylierung mit [11C]MeI. Die radio-pharmakologische Charakterisierung der hergestellten Verbindungen umfasste Bioverteilungs-untersuchungen, Autoradiographie und dynamische Kleintier-PET-Untersuchungen mit normalen Wistar-Ratten.

Ergebnisse/Results:
Die Radiomarkierung mit [11C]MeI konnte durch die Verwendung von NaH als Base und DMF als Lösungsmittel regioselektiv als O-Methylierung durchgeführt werden. Die als Konkurrenzreaktion stattfindende N-Methylierung konnte dadurch weitgehend unterdrückt werden. Die 11C-markierten Chromenderivate konnten in radiochemischen Ausbeuten von 33% und spezifischen Aktivitäten von 15 GBq/µmol erhalten werden. Bioverteilungsstudien zeigten Hirnanreicherungen von bis zu 1.6 %ID/g nach 5 min und 0.6 %ID/g nach 60 min. In den Kleintier-PET Aufnahmen waren GR-reiche Gehirnareale wie der Cortex gut sichtbar.

Schlussfolgerungen/Conclusions:
Das vorgestellte Chromengerüst eignet sich als vielversprechende Leitstruktur für die Entwicklung neuer GR-bindender Radiotracer mit moderater Lipophilie. Weitere radiopharmakologische Untersuchungen sind für eine abschließende Bewertung der vorgestellten Verbindungen als PET-Radiotracer für die Darstellung von GR im Gehirn notwendig.

Literatur/References:
[1] E. R. De Kloet et al. Endocr. Rev. 1998 19(3):269-301.
  • Lecture (Conference)
    46. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, 23.-26.04.2008, Leipzig, Germany
  • Abstract in refereed journal
    Nuklearmedizin 47(2008)2, A31

Publ.-Id: 11300 - Permalink


A Novel Approach for Predicting the Positron Emitter Distributions Produced during Therapeutic Ion Irradiation
Priegnitz, M.; Fiedler, F.; Kunath, D.; Laube, K.; Parodi, K.; Sommerer, F.; Enghardt, W.;
In-beam PET is a valuable method for a beam-delivery independent dose monitoring in radiation therapy with ion beams. The clinical feasibility of in-beam PET has been demonstrated for carbon and proton beams up to now. From radiobiological point of view it is highly desirable to perform tumor irradiation also with other ions. To extend the application of in-beam PET also to these ions, extensive knowledge about positron emitter production via nuclear fragmentation reactions during ion irradiation is necessary. To model the positron emitter production correctly, cross
sections for all possible nuclear reactions occurring in the tissue during irradiation and leading to positron emitters are required. Since for many ions of therapeutic interest these cross sections are not available in the required energy range, a novel approach for estimating the positron emitter production from experimental data is introduced. The prediction of positron emitter distributions is based on depth dependent thick target yields, which are deduced by linear superposition of measured yields in water, graphite and polyethylene as reference materials. First results on the prediction of positron emitter distributions in polymethyl methacrylate (PMMA) targets induced by Li and C irradiation are presented. By comparison with data deduced from experiments, it is shown that a rather accurate prediction of positron emitter distribution in PMMA is possible with this method.
  • Contribution to proceedings
    IEEE Dresden 2008, 19.-25.10.2008, Dresden, Germany
  • Lecture (Conference)
    IEEE Dresden 2008, 19.-25.10.2008, Dresden, Germany

Publ.-Id: 11299 - Permalink


Synthesis and in vitro evaluation of new diphenyl ether derivatives as serotonin transporter ligands
Guo, Y.; Chen, X.; Jia, H.; Deuther-Conrad, W.; Brust, P.; Steinbach, J.; Vercouillie, J.; Liu, B.;
For the development of new ligands as potential imaging agents for the serotonin transporter (SERT), a series of diphenyl ether derivatives have been synthesized, characterized, and evaluated for their in vitro binding affinities to the SERT. Among the above compounds, 2-(2-((dimethylamino)methyl)-4-fluorophenoxy)-5-bromobenzenamine (15) and 2-(2-((dimethylamino)methyl)-4-fluorophenoxy)-5-iodobenzene amine (16) show high binding affinities for the SERT with K i values of 0.28 and 0.20 nmol·L−1, respectively. They can be further labeled with carbon-11, fluorine-18, iodine-123 or bromine-76, and evaluated as useful imaging agents for the SERT. Moreover, the study of the structure-activity relationship (SAR) provides some useful information for the future design of new ligands.
Keywords: serotonin transporter - diphenyl ether - imaging agents - in vitro evaluation

Publ.-Id: 11298 - Permalink


Bacterial and archaeal communities' composition of uranium-contaminated soils in Bulgaria
Radeva, G.; Kenarova, A.; Buchvarova, V.; Flemming, K.; Selenska-Pobell, S.;
The uranium mining waste piles, mill tailing, and disposal sites in several regions of Bulgaria are highly contaminated with toxic metals as a result of the U mining and milling performed in the past. In order to suggest appropriate bioremediation strategies for such environments, the phylogenetic composition and structure of the microbial communities in two uranium-contaminated sites were characterized by using molecular approaches. Three soil samples were studied: two of them were collected from different depths of a U mill tailings (Metallurg Buhovo, located in western Bulgaria), and the third - from a former U mining site (mine Sliven, South-Eastern Bulgaria). 16S rRNA gene libraries were generated from total community DNA, using universal bacterial and archaeal oligonucleotide primer sets. Four hundred fifty bacterial clones were analyzed and grouped in sixty eight operational taxonomic units (OTUs). Three hundred ninety two archaeal clones of the clone libraries from the two U mill tailings soil samples were organized in fourteen archaeal OTUs. Rarefaction analysis indicated a high diversity of bacterial sequences, while the archaeal sequences were less diverse. Most of the bacterial sequences were affiliated with Proteobacteria from Alpha- Beta-, and Gamma- subdivisions. 16S rRNA gene sequences representing Bacteroidetes, Acidobacteria, Verrucomicrobia, Actinobacteria, and Gemmatimonadete were found in various numbers as well. Our results showed that the composition of the microbial communities in the two different studied ecosystems was diverse and environment-specific. Acidobacteria and Bacteroidetes were predominant in the soil samples collected from the U mill tailings, whereas Gammaproteobacteria and Actinobacteria were characteristic for the soil from the U mining waste. All archaeal 16S rRNA gene sequences retrieved from the U mill tailings soil samples were affiliated with the group 1.1b of the mesophilic soil Crenarchaeota which still does not contain any cultured representatives. Closely related 16S rRNA gene sequences were repeatedly found earlier in soil samples from different U mining waste piles and mill tailings in the east part of Germany.
Taken into account the significance of Crenarchaeota in the global nitrogen cycle, the studied soil samples were assayed also for the presence of ammonia monooxygenase subunit A (amoA) gene. Using PCR primers targeting archaeal amoA genes, two clone libraries were constructed and analyzed.
Keywords: 16S rRNA, bacterial diversity, Archaea, uranium mining wastes
  • Contribution to proceedings
    XII International Congress of Bacteriology and Applied Microbiology, 05.-09.08.2008, Istanbul, Turkey

Publ.-Id: 11297 - Permalink


Accumulation of Heavy Metals by Microorganisms: Biomineralization and Nanocluster Formation
Selenska-Pobell, S.; Merroun, M.;
Bacteria and archaea are the most ubiquitous organisms in terrestrial and aquatic environments. They play a major role in deposition and weathering of a large variety of minerals enriched with or consisting mainly of different metals, such as iron, manganese, copper, gold, and even radionuclides (e.g. uranium). The structure of biologically synthesized minerals is strongly influenced by the metabolic properties of the bacterial or archaeal strains involved in their production and also by the metal binding potentials of their cell wall components.
This chapter is focused on cell wall dependent accumulation and biomineralization of iron and uranium. By using transmission electron microscopic analysis in combination with x-ray absorption and time-resolved laser-induced fluorescence spectroscopic analyses it is demonstrated that the Gram-negative and most of the Gram-positive bacteria as well as some archaea immobilize U(VI) at their cell walls or extracellularly in a form of uranyl phosphate compounds. However, some Gram-positive bacteria which possess highly ordered proteinaceous surface layers (S-layers), are immobilizing U(VI) not only by phosphate groups mainly from their peptidoglycan but also by the carboxylic groups of the aspartate and glutamate stretches of their S-layers.
In addition, the cell wall supported formation of metallic palladium nanoclusters by some bacteria is presented as well. Despite the different mechanisms of the biological deposition of Pd by Gram-negative and Gram-positive bacteria, the nanoparticles formed by both organisms have almost identical size and catalytic activity.
  • Contribution to external collection
    König, H., Claus, H., Varma, A.: Prokaryotic Cell Wall Components – Structure and Biochemistry, Heidelberg: Springer Verlag, 2010, 483-500

Publ.-Id: 11295 - Permalink


Biodistribution and metabolism of hCT-derived cell-penetreting peptides
Bergmann, R.; Rennert, R.; Közle, I.; Franke, J.; Schlesinger, J.; Neundorf, I.;
Introduction:
Cell-penetrating peptides (CPP) derived from the native peptide hormone human calcitonin (hCT) represent a high potential drug delivery system for in vivo intracellular targeting of diagnostic and therapeutic compounds. Cell penetration of hCT-derived substances was
verified in vitro, however, the knowledge about CPP in vivo distribution and metabolism is very limited. Therefore we studied the in vivo radiopharmacology of 68Ga radiolabeled DOTAmodified, hCT-derived CPP in rats using small animal PET.

Methodology:
Three hCT-derived peptides (hCT(9-32), LGTYTQDFNKFHTFPQTAIGVGAPNH2; [f12,16]-hCT(9-32), LGTfTQDfNKFHTFPQTAIGVGAP-NH2; random (rd)-hCT(9-32), FLTAGQNTIQTPVKTGGHFPFADY-NH2) were at the N-terminus modified with DOTA. The biodistribution and kinetics of the radiolabeled 68Ga-DOTA-hCT(9-32) or 68Ga-DOTA-[f12,16]-hCT(9-32) or 68Ga-DOTA-rd-hCT(9-32) were studied with small animal PET. The arterial blood at different time points, and urine were analyzed for radio-metabolites.

Results:
The radio-peptides were eliminated mainly by the renal system, more than 50% of the injected dose was found at 60 min after injection in the urine, only small amounts of the activity were detected in the intestine. The general activity retention in the body was low, except the kidneys. The blood clearance of the original peptides reached terminal half-lifes of 68Ga-DOTAhCT(9-32) 15.9 min, 68Ga-DOTA-[f12,16]-hCT(9-32) 20.9 min, 68Ga-DOTA-rd-hCT(9-32) 15.8 min; the relative AUC in comparison to 68Ga-DOTA-hCT(9-32) were 100%, 170%, and 51%, respectively. The patterns of metabolic cleavage in the arterial blood were different. The 68Ga-DOTA-[f12,16]-hCT(9-32) was metabolized to three radio-metabolites after 30 min, the other radiopeptides were degraded to more than five radioactive metabolites.

Conclusion:
It was shown that D-amino acid modifications of the sequence hCT(9-32) resulted in an increased in vivo stability and lower retention in the kidney cortex. The blood clearance and the elimination of the 68Ga-DOTA-peptides were relatively high and should be decreased by
structural changes to enhance the tissue uptake of this drug carrier system.
  • Lecture (Conference)
    19th Meeting of the International Research group in Immuno-Scintigraphy and Therapy (IRIST), 25.-28.06.2008, Krakow, Poland

Publ.-Id: 11294 - Permalink


Bacteria Heavy Metal Interactions: Biomineralization and Nanoclusters Formation
Selenska-Pobell, S.;
Bacteria exhibit fascinating resistant mechanisms to extreme temperatures, acidity, alkalinity, high metal, radionuclide, and salt concentrations. For this reason, they occupy not only the moderate habitats of humans, animals, plants, and insects but also extremely harsh environments such as hot springs, permafrost, acidic mine drainages, “dead” sees, etc.
Due to their ubiquitous distribution in terrestrial and aquatic environments bacteria play a major role in deposition and weathering in the earth’s crust of a large variety of minerals enriched with or consisting mainly of different metals, such as iron, manganese, copper, gold, and even radionuclides (e.g. uranium). The structure of biologically synthesized minerals is strongly influenced by the metabolic properties of the bacterial or archaeal strains involved in their production and also by the differences in their cell wall organization.
  • Invited lecture (Conferences)
    Invited talk at Ben Gurion University of the Negev, 02.04.2008, Negev, Israel

Publ.-Id: 11293 - Permalink


A comparative study of n.c.a. sodium [18F]fluoroacetate and sodium [11C]acetate in xenotransplanted tumor bearing mice
Bergmann, R.; Richter, S.; Pietzsch, J.; Beuthien-Baumann, B.; Wüst, F.;
Objectives :
This study describes the radiosynthesis of [18F]fluoroacetate (18F-FAC), radiopharmacological characterization, and molecular imaging of oxidative metabolism in tumor bearing mice using 18F-FAC in comparison with 11C-ACE.

Methods :
The radiosynthesis of n.c.a. sodium 18F-FAC was performed in two step reaction sequence and subsequent SPE purification in a remotely controlled synthesis module.
Biodistribution, metabolism and small animal PET studies of 18F-FAC and 11C-ACE were carried out in rats and HT-29 tumor-bearing mice.

Results :
18F-FAC was obtained in radiochemical yields of 20-25% within 50 min. Biodistribution data showed higher initial radioactivity uptake in most organs and tissues for 18F-FAC; the initial brain uptake of 0.67 %ID/g at 5 min p.i. followed by a 22% clearance at 60 min p.i. Both radiotracers can clearly delineate the tumor. The tumor-to-muscle ration was 1.8 for 18F-FAC and 1.5 for 11C-ACE. Unlike 11C-ACE, 18F-FAC shows a slow transport of the free radiotracer from the blood pool into the tumor, and 10% of the free fraction of 18FFAC is trapped in tumor tissue.

Conclusions :
The highly reproducible remotely-controlled two step/one pot synthesis of 18FFAC represents an alternative to previously published synthesis routes. The successful PET imaging of xenotransplanted human colorectal adenocarcinoma tumor HT-29 by means of 18F-FAC shows that the radiotracer may not only be restricted for imaging of previously reported prostate cancer tumors. However, the exact mechanism of 18F-FAC tissue uptake remains unclear and should be subject of further studies.

Research Support : Supported in part by the EU FP6 ‘‘BioCare’’, proposal #505785.
  • Lecture (Conference)
    2008 SNM Annual Meeting, 14.-18.06.2008, New Orleans, USA

Publ.-Id: 11292 - Permalink


The impact of implantation defects in SIMOX processing
Kögler, R.; Ou, X.;
The impact of implantation induced point defects in SIMOX (Separation by IMplantation of OXygen) processing is explained. The origin of the so-called energy-dose window is shown to be the point defects generated by the oxygen implantation.
Keywords: Oxygen implantation, SIMOX, point defects
  • Lecture (Conference)
    Arbeitstreffen "Punktdefekte", 03.-04.04.2008, Dresden, Deutschland

Publ.-Id: 11291 - Permalink


CFD simulation of convective flow boiling of refrigerant in a vertical annulus
Koncar, B.; Krepper, E.;
In this paper a forced convective boiling of Refrigerant R-113 in a vertical annular channel has been simulated by a custom version of the CFX-5 code. The employed subcooled boiling model uses a special treatment of the wall boiling boundary, which assures the grid invariant solution. The simulation results have been validated against the published experimental data. In general a good agreement with the experimental data has been achieved, which shows that the current model may be applied for the Refrigerant R-113 without significantly changing the model parameters. The influence of non-drag forces, bubble diameter size and interfacial drag model on the numerical results has been investigated as well.
Keywords: forced convective boiling, refrigerant R-113, CFD simulations, validation
  • Nuclear Engineering and Design 238(2008), 693-706

Publ.-Id: 11290 - Permalink


Fluctuations due to nonlocal collisions
Morawetz, K.;
It is shown that the collision integral describing the nonlocal character of collisions leads to the same mean-field fluctuations in the one-particle distribution as proposed by Boltzmann-Langevin pictures. It is argued that this appropriate collision integral contains the fluctuation-dissipation theorems in equilibrium itself and therefore there is no need to assume additionally stochasticity. This leads to tremendous simplifications in numerical simulation schemes.
  • Poster
    International Workshop on Chaos and Collectivity in Many-Body System, 05.-08.03.2008, Dresden, Germany

Publ.-Id: 11288 - Permalink


The concept of correlated density and its application
Morawetz, K.; Lipavsky, P.; Kolacek, J.; Brandt, E. H.; Schreiber, M.;
The correlated density appears in many physical systems ranging from dense interacting gases up to Fermi liquids which develop a coherent state at low temperatures, the superconductivity. The underlying quantum statistical theory in nonequilibrium is the nonlocal kinetic theory developed earlier. One consequence of the correlated density is the Bernoulli potential in superconductors which compensates forces from dielectric currents which allows to access material parameters.
  • Poster
    72. Jahrestagung der DPG und DPG Frühjahrstagung des Arbeitskreises Festkörperphysik, 25.-29.03.2008, Berlin, Germany

Publ.-Id: 11287 - Permalink


Contribution of the surface dipole to deformation of superconductors
Morawetz, K.; Lipavsky, P.; Kolacek, J.; Brandt, E. H.; Schreiber, M.;
The interaction of the ionic lattice with the superconducting condensate is treated in terms of the electrostatic force in superconductors. It is shown that the surface dipole supplies the force responsible for the volume difference of the normal and superconducting states. Assuming this mechanism we argue
that the usual parametrization of the theory of deformable superconductors should be revisited.
  • Poster
    72. Jahrestagung der DPG und DPG Frühjahrstagung des Arbeitskreises Festkörperphysik, 25.-29.03.2008, Berlin, Germany

Publ.-Id: 11286 - Permalink


Enhancement of pairing near reasonant atoms
Morawetz, K.;
A correlated fermion system is considered surrounding a finite cavity with virtual levels. The pairing properties are calculated and the influence of the cavity is demonstrated. To this end the Gell-Mann and Goldberger formula is generalized to many-body systems. We find a possible enhancement of pairing temperature if the Fermi momentum times the cavity radius fulfills a certain resonance condition which suggests an experimental realization.
  • Poster
    International Workshop on Chaos and Collectivity in Many-Body Systems, 05.-08.03.2008, Dresden, Germany

Publ.-Id: 11285 - Permalink


Surface deformation and magnetocapacitance of superconductors
Morawetz, K.; Lipavsky, P.; Kolacek, J.; Brandt, E. H.;
Electrostatic potentials have been measured at surfaces of superconductors in order to access directly the gap and material parameters. The reason why no thermodynamic corrections are measured as predicted by the theory, e.g. by Rickayzen, has remained a puzzle for almost 30 years. The solution is found in the Budd-Vannimenus theorem due to the surface dipoles. To access thermodynamic corrections one has to look deeper in the bulk like in an experiment by Kumagai et al measuring the quadrupole shift of the NMR in YBCO. The found large magnitude and unexpected sign is explained by the charge transfer between Cu chains and planes. To this end we develop the theory of electrostatic potentials above the Abrikosov vortex lattice within Bardeen's extension of the Ginzburg-Landau theory to low temperatures including the surface dipole.
As applications it is proposed:
(i) The deformation of the crystal due to the presence of vortices is calculated and the corresponding effective mass of vortices is suggested to be measured.
(ii) We found a jump of the magnetocapacitance at the surface critical magnetic field which should be experimentally accessible.

The experimentally confirmed Bernoulli potential is a consequence of the correla ted density which follows from the concept of nonlocal kinetic theory. Therefore we see this Bernoulli potential as a justification of our kinetic equation of nonlocal and non-instantaneous character which has unified the achievements of transport in dense gases with the quantum transport of dense Fermi systems.
  • Invited lecture (Conferences)
    1st Bilateral Estonian-German Workshop, 30.04.-02.05.2008, Tartu, Estland

Publ.-Id: 11284 - Permalink


Phase diagram for interacting Bose systems
Maennel, M.; Morawetz, K.; Schreiber, M.;
no abstract available
  • Lecture (Conference)
    72. Jahrestagung der DPG und DPG Frühjahrstagung des Arbeitskreises Festkörperphysik, 25.-29.03.2008, Berlin, Germany

Publ.-Id: 11283 - Permalink


The chemical potential for the inhomogeneous electron liquid in terms of its kinetic and potential parts with special consideration of the surface po tential step and BCS-BEC crossover
Morawetz, K.; March, N. H.; Squire, R. H.;
The chemical potential $\mu$ of a many-body system is valuable since it carries fingerprints of phase changes. Here, we summarize results for $\mu$ for a three-dimensional electron liquid in terms of average kinetic and potential energies per particle. The difference between $\mu$ and the energy per particle is found to be exactly the electrostatic potential step at the surface. We also present calculations for an integrable one-dimensional many-body system with delta function interactions, exhibiting a BCS-BEC crossover. It is shown that in the BCS regime the chemical potential can be expressed solely in terms of the ground-state energy per particle. A brief discussion is also included of the strong coupling BEC limit.
  • Lecture (Conference)
    72. Jahrestagung der DPG und DPG Frühjahrstagung des Arbeitskreises Festkörperphysik, 25.-29.03.2008, Berlin, Germany

Publ.-Id: 11282 - Permalink


Dominant motion vs. localization in quasiperiodic chains
Morawetz, K.; Schreiber, M.;
Chains of coupled clusters arranged in a quasiperiodic sequence are analyzed with respect to the dynamics of wave packets. The recurrence probability is shown to show characteristic plateaus described by an interplay of localization and dominant motion. A three-mode model is developed which allows to understand the features of the recurrence probability as well as of the time-dependent width of the wave packets. The relation to waiting probabilities and anomalous diffusion is worked out. The consequences for the transmission coefficient realizable in experiments by sequences of quasiperiodic chains are discussed and the generalizations towards two-dimensional tilings are presented.
  • Lecture (Conference)
    72. Jahrestagung der DPG und DPG Frühjahrstagung des Arbeitskreises Festkörperphysik, 25.-29.03.2008, Berlin, Germany

Publ.-Id: 11281 - Permalink


Surface superconductivity and capacitance of superconductors under electric and magnetic fields
Morawetz, K.; Lipavsky, P.; Kolacek, J.; Brandt, E. H.; Schreiber, M.;
A superconducting layer exposed to a perpendicular electric and parallel magnetic field is considered within the Ginzburg-Landau (GL) approach. The GL equation is solved near the surface and the surface energy is calculated. The nucleation critical field is shown to be changed in dependence on the magnetic and electric field. Special consideration is payed to the induced magnetic-field effect caused by diamagnetic surface currents. The latter effect constitutes the main contribution to the effective inverse capacitance which determines the effective penetration depth.
The surface energy becomes strongly dependent on the width of the sample.
An experimental realization is suggested for determining the change in the effective capacitance of the layer.
  • Lecture (Conference)
    72. Jahrestagung der DPG und DPG Frühjahrstagung des Arbeitskreises Festkörperphysik, 25.-29.03.2008, Berlin, Germany

Publ.-Id: 11280 - Permalink


VVER-1000 main steam line break analysis using the coupled code system DYN3D/ATHLET
Kliem, S.; Kozmenkov, Y.; Höhne, T.; Rohde, U.; Weiß, F.-P.;
Calculations using the coupled code system DYN3D/ATHLET were performed in the frame of the OECD/NEA MSLB benchmark for a VVER-1000 reactor. The coolant mixing inside the reactor pressure vessel was treated using a validated empirical mixing model implemented into the DYN3D/ATHLET code.
Using very conservative boundary conditions (reduced scram worth, two stuck rods, running MCP throughout the whole transient) a return-to-power was predicted.
For the assessment of the empirical mixing model a time dependent calculation using the computational fluid dynamics code CFX-10 was performed. For that analysis, a detailed model of the reactor pressure vessel consisting of the inlets nozzles, downcomer, lower plenum and a part of the core and having 4.67 million unstructured tetra cell elements was used. For the considered case with running main coolant pumps, this calculation shows a sector formation at the core inlet with a certain amount of mixing at the edges of the sector.
A core calculation using these CFX results as boundary conditions predicted also a return-to-power with a maximum value being about 200 MW lower than in the coupled code calculation. This variation calculation confirms the applicability of the empirical mixing model. The comparison shows also, that in this way results with a reasonable degree of conservatism can be obtained.
  • Contribution to proceedings
    International Conference on the Physics of Reactors (PHYSOR'08), 14.-19.09.2008, Interlaken, Switzerland
    Proceeedings of the International Conference on the Physics of Reactors 2008, CDROM paper 311, Villigen: Paul Scherrer Institut, 978-3952140956
  • Lecture (Conference)
    International Conference on the Physics of Reactors (PHYSOR'08), 14.-19.09.2008, Interlaken, Switzerland

Publ.-Id: 11279 - Permalink


Nanocluster in implantierten Lichtemitter-Bauelementen durch ms-Temperung
Skorupa, W.; Rebohle, L.; Prucnal, S.; Kanjilal, A.; Sun, J. M.; Cherkouk, C.; Helm, M.; Nazarov, A.; Behar, M.;
Die effiziente Erzeugung silizium-basierter Elektrolumineszenz ist eine Schlüsselproblematik, die für den avisierten Übergang von der Nanoelektronik zur Nanophotonik von entscheidender Bedeutung ist. Im Vortrag wird über die Korrelation von Temperzeit, der Größe von Seltenerde-Nanoclustern und deren Einfluß auf die Elektrolumineszenz-Ausbeute in Lichtemitter-Bauelementen berichtet, die auf implantierten, thermisch gewachsenen SiO2-Schichten auf Si-Wafern basieren.
Keywords: nanocluster, rare earth, ion implantation, electroluminescence, silicon-based light emitting devices
  • Lecture (Conference)
    Workshop Ionenstrahlphysik und Nanotechnologie, 11.-12.04.2008, Darmstadt, Germany

Publ.-Id: 11278 - Permalink


Assembly, structure, and performance of an ultra-thin film organic field-effect transistor (OFET) based on substituted oligothiophenes
Haubner, K.; Jaehne, E.; Adler, H.-J.; Koehler, D.; Loppacher, C.; Eng, L. M.; Grenzer, J.; Herasimovich, A.; Scheinert, S.;
We report on the improved assembly and characterization of a small molecule organic field-effect transistor (OFET). Novel alpha-omega-dicyano substituted beta-beta'-dibutylquaterthiophene molecules (DCNDBQT) were synthesized and characterized by UV–Vis spectroscopy, differential scanning calorimetry, thermal gravimetric analysis and cyclic voltammetry. The ultra-thin organic film formation on TiO2 templates was effectively promoted through the specifically designed bifunctional self assembly molecules (SAM) 5-cyano-2-(butyl-4- phosphonic acid)-3-butylthiophene (CNBTPA). Excellent structural properties were found for up to 9 DCNDBQT molecule thick films prepared through UHV vacuum sublimation as investigated with UHV non-contact atomic force microscopy (nc-AFM) and X-ray diffraction. Both X-ray and nc-AFM data indicate that the DCNDBQT molecules form a well-ordered terraced structure exhibiting step heights of 1.5 nm to 2.0 nm layers. Hence, the DCNDBQTmolecules are linked to the functional SAM interface layer by H-bond interactions (see structure model) standing quasi perpendicular to the TiO2 template, and thus providing optimal orbital overlap neigh-bouring thiophene rings. The vacuum sublimated DCNDBQT molecules form a closed packed and dense molecular layer that was used to construct and operate a nanoscopic OFET-structure. The resulting field mobilities of 10^–5 cm^2 /V /s reflect a high current density in our ultrathin but highly ordered structure.
Keywords: organic field-effect transistor (OFET)

Publ.-Id: 11277 - Permalink


Flow structure and concentration distribution in seemingly parallel magnetic and electric fields
Weier, T.; Cierpka, C.; Eckert, K.; Uhlemann, M.; Bund, A.;
We aim to show that flow field and concentration measurements are a valuable aid in understanding magnetoelectrochemical phenomena. Two examples, the flow field in a cylindrical cell and the concentration distribution near a circular millielectrode, will be discussed. Both cases have in common that at first sight electric and magnetic fields seem to be parallel. However, in reality, Lorentz forces are generated at locations, where the assumption of parallelism is locally violated, inducing convection phenomena of surprising complexity.
  • Lecture (Conference)
    7th PAMIR International Conference on Fundamental and Applied MHD, 08.-12.09.2008, Presqu´île de Giens, France
  • Contribution to proceedings
    7th International pamir Conference on Fundamental and Applied MHD, 08.-12.09.2008, Presqu´île de Giens, France, 333-337

Publ.-Id: 11276 - Permalink


Biodiversität im Filter: Wie Forscher helfen, Uran-Altlasten zu beseitigen
Raff, J.; Pollmann, K.;
Mikrobiologen im Forschungszentrum Dresden-Rossendorf entwickeln intelligente Filtersysteme zur Entfernung oder Rückgewinnung von Metallen aus Wässern, indem sie den Überlebensmechanismus von Bakterien nutzen. Vor wenigen Jahren fanden sie Bakterien mit verblüffenden Eigenschaften auf einer Uran-Abfallhalde im sächsischen Johanngeorgenstadt. Wie am Beispiel des Isolates Lysinibacillus sphaericus JG-A12 gezeigt werden konnte, haben die Bakterien im Laufe der Evolution eine spezielle Schutzschicht entwickelt, um sich vor dem toxischen Schwermetall Uran zu schützen. Die Schicht besteht aus besonderen Hüllproteinen, die auf der Zelloberfläche nanoskalige Gitter ausbilden und dazu dienen, giftige Metalle am Eindringen in die Zelle zu hindern, für das Überleben des Bakteriums wichtige Substanzen jedoch passieren zu lassen.
Die Forscher kopieren für ihre neuartigen Filtersysteme diese genialen Vorbilder aus der Natur. Sie stellen Bioverbundmaterialien aus Hüllproteinen auf der Grundlage von konventionellen Immobilisierungsverfahren her bzw. beschichten herkömmliche Filtermaterialien mit den Hüllproteinen. Im Ergebnis erhalten sie Filter, die nur die Metalle aus dem Wasser holen, die entfernt oder gewonnen werden sollen, und das selbst bei niedrigsten Konzentrationen. Durch die Verwendung unterschiedlicher Proteine sollen zukünftig Filtermaterialien für verschiedene Metalle hergestellt werden und derartig miteinander kombinierbar sein, dass schließlich eine individuelle Wasserbehandlung möglich wird. Bis zur großtechnischen Anwendung dieser Verfahren werden jedoch noch einige Jahre vergehen.
  • Poster
    Parlamentarischer Abend der Leibniz-Gemeinschaft, 06.05.2008, Berlin, Deutschland

Publ.-Id: 11275 - Permalink


Simulation von ATWS-Transienten in Druckwasserreaktoren
Kliem, S.; Mittag, S.; Rohde, U.; Grundmann, U.; Weiß, F.-P.;
Im Rahmen von Sicherheitsanalysen für KKW werden auch Transienten mit unterstelltem Ausfall der Reaktorschnellabschaltung (RESA) betrachtet. Bei diesen ATWS-Transienten (Anticipated Transients Without Scram) wird angenommen, dass das mechanische Einfahren der Regel- und Abschaltstäbe vollständig versagt, wenn es infolge eines bestimmten Ereignisses angefordert wird. Bei einem derartigen Versagen der RESA wird die Leistungsentwicklung im Reaktorkern ausschließlich durch die neutronenkinetische Rückkopplung über Brennstofftemperatur, Moderatortemperatur und –dichte sowie Borkonzentration bestimmt.
Die ATWS-Transiente „Ausfall der Hauptspeisewasserversorgung mit Nichtabschalten der Hauptkühlmittelpumpen“ wurde mit dem gekoppelten neutronenkinetisch/thermohydraulischen Programmkomplex DYN3D/ATHLET analysiert. Dabei wurde der Einfluss systemtechnischer und neutronenkinetischer Randbedingungen auf die Rechenergebnisse untersucht. Bei den durchgeführten Rechnungen handelt es sich um methodische Untersuchungen und nicht um Nachweisführungen.
Die Reduktion der Abblasemenge aus dem Primärkreislauf, welche die Unsicherheiten beim zweiphasigen kritischen Ausströmen abdecken soll, hat unter den ausgewählten Variationen den größten Einfluss auf den Druckverlauf im Primärkreislauf, der bei der betrachteten Transiente der wichtigste Sicherheitsparameter ist.
Die Veränderung der Kernbeladung (Variation der Anzahl der MOX-Brennelemente) hat einen großen Einfluss auf die Reaktivitätskoeffizienten der Brennstofftemperatur und der Moderatordichte. Über diese zwei Koeffizienten wird der Primärdruck stark beeinflusst. Wesentliches Ergebnis ist, dass das berechnete Druckmaximum mit Erhöhung der Anzahl der MOX-Brennelemente deutlich niedriger ausfällt.
Mit einer statistischen Variation der globalen Rückkopplungsparameter wurden für eine konkrete Kernbeladung die Auswirkungen von Unsicherheiten, die sich bei der Erstellung der Zweigruppen-Wirkungsquerschnittsdaten ergeben können, auf den Verlauf der betrachteten Transiente analysiert. Die Bereiche für die statistische Variation der Daten wurden auf Grund von Erfahrungswerten vorgegeben. Die Variation des Reaktivitätskoeffizienten der Moderatordichte bewegt sich dabei in einem ähnlichen Bereich, wie er sich bei der Variation der Anzahl der MOX-Brennelemente er-gab, der Variationsbereich des entsprechenden Koeffizienten der Brennstofftemperatur ist ungefähr doppelt so groß. Im Ergebnis ergibt sich eine größere Streuung des berechneten Maximaldrucks. Eine Streuung der Koeffizienten um ± 20 % ergibt eine Streubreite im Maximalwert des Drucks im Primärkreislauf von 2.17 MPa, die entsprechenden berechneten Toleranzgrenzen sind 18.26 und 20.43 MPa. Eine Sensitivitätsanalyse ergab, dass der Primärdruck in größerem Maß vom Dichtekoeffizienten abhängt, der Koeffizient der Brennstofftemperatur beeinflusst das Druckmaximum bei gleicher relativer Variation nur halb so stark.
  • Contribution to proceedings
    Jahrestagung Kerntechnik 2008, 27.-29.05.2008, Hamburg, Germany
    Tagungsband der Jahrestagung Kerntechnik 2008, CDROM, Berlin: INFORUM GmbH
  • Invited lecture (Conferences)
    Jahrestagung Kerntechnik 2008, 27.-29.05.2008, Hamburg, Germany
  • atw - International Journal for Nuclear Power 54(2009)2, 100-110

Publ.-Id: 11274 - Permalink


Study of the L-shell ionisation of gold by 3.0-18.2 MeV nitrogen-ion bombardment
Palinkas, J.; Sarkadi, L.; Schlenk, B.; Török, I.; Kalman, G.; Bauer, C.; Brankoff, K.; Grambole, D.; Heiser, C.; Rudolph, W.; Thomas, H. J.;
The angular distributions of the L x-ray line intensities of gold have been measured by nitrogen-ion bombardment in the 3.0-18.2 MeV energy region. From the measured data absolute subshell ionisation cross sections and the anisotropy parameter of the Ll x-ray line have been deduced. Comparing the experimental data with the first-order perturbation theories significant deviations have been found, especially for the L2-subshell ionisation cross section and for the anisotropy parameter of the Ll x-ray line.
  • Journal of Physics B 17(1983), 131-145

Publ.-Id: 11273 - Permalink


CO2 laser nitriding of titanium
Raaif, M.; El-Hossary, F. M.; Negm, N. Z.; Khalil, S. M.; Kolitsch, A.; Möller, W.; Höche, D.; Kaspar, J.; Schaaf, P.; Mändl, S.;
Samples of pure titanium were laser nitrided by continuous wave CO2 laser irradiation in mixtures of nitrogen and argon gas with different ratios. In all cases, TiN formed in the surface. The properties and the characteristics of the processed samples were evaluated using nanoindentation technique, optical microscopy, surface roughness measurements, X-ray diffraction and wear resistance measurements. It was found that the nitrogen content in the gas atmosphere has a massive effect on the microstructure and the mechanical properties of the laser nitrided samples. For all treated samples, the mechanical properties are improving with the nitrogen content in the gas atmosphere. Moreover, the thickest TiN layers with high values of the microhardness and good wear resistance were obtained for the titanium sample that was treated in 80% N2 and 20% Ar. In addition, the strain and the grain size of the coatings formed at the surface of the laser nitrided titanium samples were determined from X-ray data.
Keywords: laser nitriding, TiN
  • Journal of Physics D: Applied Physics 41(2008), 085208

Publ.-Id: 11272 - Permalink


Ion implantation followed by laser/pulsed plasma/ion beam annealing: a new approach to fabrication of superconducting MgB2 thin films
Piekoszewski, J.; Werner, Z.; Barlak, M.; Kolitsch, A.; Szymczyk, W.;
The paper presents a new approach to formation of superconducting MgB2 thin films: ion implantation followed by annealing in an unconventional second step treatment using pulsed laser, plasma, or ion beams. Merits and drawbacks of individual approaches are discussed.
Keywords: superconductivity
  • Nukleonika 53(2008)1, 7-10

Publ.-Id: 11271 - Permalink


Infrared spectroscopic identification of aqueous neptunium species
Müller, K.; Foerstendorf, H.; Brendler, V.;
In the safety assesment of underground disposal of radioactive waste neptunium (Np) is one of the most relevant radionuclides. Due to its long half-life, its hazardous to human health and its mobility under aerobic conditions Np-237 is considered as a possible long-term pollutant of the ecosystem from the safety point of view. The distribution of aqueous neptunium species, as there are the free neptunyl ions of Np(V) and Np(VI) and various complexes arising from hydrolysis or carbonate complexation, primarily defines its geochemical reactions and migration behavior in the environment.

Current knowledge about Np speciation is mainly based on data obtained by non-structural experiments such as potentiometric titration [1]. A spectroscopic verification of these Np species is still incomplete. There are only few EXAFS and Raman spectroscopic studies [2-4], using very high Np concentrations. Attenuated Total Reflectance Fourier-transform Infrared (ATR-FTIR) spectroscopy is a useful technique for the identification of different molecular species and it allows the direct measurement of liquid samples to obtain important spectral information even at low neptunyl concentrations relevant to environmental conditions.

In this study we investigate the Np speciation in aqueous solution using ATR-FTIR spectroscopy focusing on micromolar neptunyl concentrations. We work with varied experimental conditions, i.e. Np oxidation state (Np(V) and Np(VI)), wide pH range (pH 2 – 10), inert gas atmosphere, ionic strength. We present the first IR spectra of aqueous Np solutions and compare our results critically to thermodynamic calculations.

[1] R. Guillaumont et al. (OECD-NEA TDB), Update on the Chemical Thermodynamics of Uranium, Neptunium, Plutonium, Americium and Technetium, Elsevier, 2003.
[2] Gregoire-Kappenstein, A. C. et al., Radiochim. Acta 91, 665 (2003).
[3] Jones, L. H. et al., J. Chem. Phys. 21, 542 (1953).
[4] Madic, C. et al., Inorg. Chem. 22, 1494 (1983).
  • Lecture (Conference)
    V Ibero-American Congress of Environmental Physics and Chemistry, 14.-18.04.2008, Mar del Plata, Argentina
  • Contribution to proceedings
    V Ibero-American Congress of Environmental Physics and Chemistry, 14.-18.04.2008, Mar del Plata, Argentina
    Las Fronteras de la Física y Química Ambiental en Ibero América: libro de actas del V congreso iberoamericano de física y química ambiental, Buenos Aires, Argentina: Universidad Nacional de San Martin, 978-987-1435-05-0, 39

Publ.-Id: 11270 - Permalink


Enhanced electric dipole strength below particle-threshold as a consequence of nuclear deformation
Rusev, G.; Schwengner, R.; Beyer, R.; Erhard, M.; Grosse, E.; Junghans, A. R.; Kosev, K.; Nair, C.; Schilling, K. D.; Wagner, A.; Dönau, F.; Frauendorf, S.;
Photoabsorption cross sections up to the neutron-separation energy were measured for the stable even-mass isotopes 92-100Mo in photon-scattering experiments. The photon-scattering data were analyzed in a novel way by taking into account the intensity of unresolved levels at high excitation energy and high level density. Simulations of gamma-ray cascades were performed to estimate the intensity distribution of inelastic transitions to low-lying levels and, hence, to deduce intensities and branching ratios of the ground-state transitions needed for the determination of the absorption cross section. The present (gamma,gamma') data can be combined for the first time with (gamma,n) data which allows us to obtain the absorption cross section in the energy range from about 4 MeV up to the giant dipole resonance for a series of isotopes. The absorption cross section below the neutron-separation energy increase with the number of neutrons above the neutron shell closure at N = 50. Calculations using a quasiparticle-random-phase approximation in a deformed Woods-Saxon potential describe this effect as a consequence of the increasing nuclear deformation.
Keywords: photon scattering, photoabsorption cross section, dipole strength function, nuclear deformation, random phase approximation

Publ.-Id: 11269 - Permalink


Sorption von U(VI) in Abwesenheit und Gegenwart von Huminsäure an Kaolinit und Opalinuston
Joseph, C.;
Die Sorption von Uran(VI) an Kaolinit in Abhängigkeit der Ionenstärke und des Salzsystems (NaClO4, Opalinustonwasser) wurde untersucht. Zusätzliche Uran(VI)-Sorptionsversuche fanden in Abwesenheit oder Gegenwart von C-14-markierter Huminsäure statt. Die Huminsäuresorption an Kaolinit wurde zusätzlich untersucht. Erste Ergebnisse zur Uran(VI)-Sorption an Opalinuston (optimales S/L-Verhältnis) konnten vorgestellt werden.
Keywords: uranium(VI), humic acid, kaolinit, opalinus clay, sorption
  • Lecture (others)
    Workshop zum Forschungsvorhaben "Wechselwirkung und Transport von Actiniden im natürlichen Tongestein unter Berücksichtigung von Huminstoffen und Tonorganika", 01.-02.04.2008, München, Germany

Publ.-Id: 11268 - Permalink


Komplexierung von U(VI) durch stickstoffhaltige Modellliganden
Raditzky, B.;
Im Vortrag werden Ergebnisse zur spektroskopischen Bestimmung von Stabilitätskonstanten für die U(VI)-Komplexierung durch organische Modellliganden vorgestellt. Insbesondere werden die stickstoffhaltigen Liganden Anthranilsäure und Nicotinsäure betrachtet.
Keywords: Uran, hexavalent, Benzolsulfonsäure, 4-Phenolsulfonsäure, Anthranilsäure, Nicotinsäure, TRLFS
  • Lecture (others)
    Workshop zum Forschungsvorhaben "Wechselwirkung und Transport von Actiniden im natürlichen Tongestein unter Berücksichtigung von Huminstoffen und Tonorganika", 01.-02.04.2008, München, Germany

Publ.-Id: 11267 - Permalink


Current without external bias and diode effect in shuttling transport of nanoshafts
Morawetz, K.; Gemming, S.; Luschtinetz, R.; Eng, L. M.; Seifert, G.; Kenfack, A.;
A row of parallely ordered and coupled molecular nanoshafts is shown to develop a shuttling transport of charges at finite temperature. The appearance of a current without applying an external bias voltage is reported as well as a natural diode effect allowing unidirectional charge transport along one field direction while blocking the opposite direction. The zero-bias voltage current appears above a threshold of initial thermal and/or dislocation energy.
Keywords: Current without bias, ratchets, OFET, nanotubes, shuttling transport
  • Open Access LogoNew Journal of Physics 10(2008)103014, 1-8

Publ.-Id: 11266 - Permalink


International Co-operation in Research - a German View onto the Challenges of Management
Joehnk, P.; Gilge, B.;
Actually there is a worldwide competition for the best ideas and for the best outcome. By now large-scale equipment for research is so expensive, that it’s nearly impossible to buy and run it single nations going it alone. A way out are international co-operation. Thereby appear a lot of new questions that concern particularly the management of such co-operation. The author gives a review about the requirements of research co-operation, some examples from a German institution and the management of programmes and projects. Also the author points out the importance of co-operation for evaluation.
Keywords: International co-operation Reqiurements of research co-operation Role of the State Management of programmes Management of projects Evaluation Management
  • Contribution to proceedings
    Technical Universities: Integration with European and World Education Systems, 22.-24.04.2008, Izhevsk, Russia, 978-5-7526-0353-2, 12-19

Publ.-Id: 11265 - Permalink


A new database on the evolution of two-phase flows in a large vertical pipe
Lucas, D.; Beyer, M.; Szalinski, L.; Schütz, P.;
A comprehensive database with high quality was obtained for stationary upward air-water flows in a vertical pipe with an inner diameter of 195.3 mm using the wire-mesh sensor technology. During the experiments the sensor was always mounted on the top of the test section while the distance between gas injection and measuring plane was varied to up to 18 different L/D by using gas injection chambers at different vertical positions. The gas was injected via holes in the pipe wall. The pressure was kept at 0.25 MPa (absolute) at the location of the active gas injection while the temperature was constant at 30°C 1K. This procedure exactly represents the evolution of the flow along the pipe, as it would be observed for an injection at a constant height position and a shifting of the measurement plane. The experiments were done for 48 combinations of air and water superficial velocities varying from 0.04 m/s to 1.6 m/s for water and 0.0025 m/s to 3.2 m/s for air. From the raw data time averaged data as: radial gas volume fraction profiles, bubble size distributions, radial volume fraction profiles decomposed according to the bubble size and the radial profiles of the gas velocity were calculated. Due to the combination of the new experimental procedure with the high spatial and temporal resolution of the wire-mesh sensor technology the data are have new quality especially regarding their consistency in the evolution with increasing L/D. This closes a gap for data suitable for the development and validation of closure models for two-phase flows and especially for models on bubble coalescence and break up.
Keywords: multiphase flow, bubbly flow, churn turbulent flow, annular flow, bubble size, pipe flow
  • International Journal of Thermal Sciences 49(2010), 664-674

Publ.-Id: 11264 - Permalink


Reduction of antimony by nanoparticulate magnetite and mackinawite
Kirsch, R.; Scheinost, A. C.; Rossberg, A.; Banerjee, D.; Charlet, L.;
Speciation of Sb is strongly influenced by its oxidation state (V, III, 0, -III). Redox processes under anerobic groundwater conditions may therefore greatly alter the environmental behavior of Sb. Employing X-ray absorption and photon spectroscopy, we show here that Sb(V) is reduced to Sb(III) by magnetite and mackinawite, two ubiquitous Fe(II)-containing minerals, while Sb(III) is not further reduced. At the surface of magnetite, Sb(III) forms a highly symmetrical sorption complex at the position else occupied by tetrahedral Fe(III). The Sb(V) reduction increases with pH, at values above pH 6.5 Sb(V) is completely reduced to Sb(III) within 30 days. In contrast, Sb(V) is completely reduced at the mackinawite surface across a wide pH range and within 15 days. Sb(V) reduction proceeds solely by oxidation of surface Fe(II), while the oxidation state of sulfide is conserved. Independent of whether Sb(V) or Sb(III) was added, an amorphous or nanoparticulate SbS3-like solid forms.
Keywords: antimony, reduction, Fe(II), magnetite, mackinawite
  • Mineralogical Magazine 72(2008)1, 185-189
  • Contribution to proceedings
    Geochemistry of the Earth's Surface 8 (GES8), 18.-22.08.2008, London, UK
    abstracts published in "Mineralogical Magazine"
  • Poster
    Geochemistry of the Earth's Surface 8 (GES8), 18.08.2008, London, UK

Publ.-Id: 11262 - Permalink


Reduction of antimony by nanoparticulate Fe3O4 and FeS
Kirsch, R.; Scheinost, A. C.; Rossberg, A.; Banerjee, D.; Charlet, L.;
Antimony finds a wide range of industrial applications, e.g. in flame retardants, brake pads and as a lead-alloy in storage batteries and ammunition and is widely distributed in the environment. Sb may occur in several oxidations states (-III, 0, III, V). Under oxic conditions, Sb0 oxidizes prevalently to SbV, forming the anionic species Sb(OH)6- which is strongly sorbed by Fe oxides[1]. In contrast, SbIII forms an uncharged complex Sb(OH)3(aq), which is more mobile. Under anoxic conditions, SbV and SbIII may be reduced by FeII-bearing minerals. Magnetite (FeIIFeIII2O4) and mackinawite (FeS) have been shown to reduce e.g. Se[2], As[3], and Pu[4]). We therefore investigated the reaction of SbIII and SbV with these two minerals at <1ppm O2 (v/v) using Sb-K XAS.
When SbIII was reacted with magnetite at pH 4.7 to 7.6 during 1 h to 67 d, the oxidation state was stable and only one Sb species was identified by EXAFS. SbIII is coordinated with 4 to 5 iron atoms at a distance of 3.6 Å. FEFF Monte Carlo simulations revealed formation of a highly ordered surface complex on the {111} faces of magnetite. The trigonal pyramidal SbO3 units occupy positions of FeIII tetrahedra, that would be ideally coordinated to six Fe06 octahedra via corner-sharing. The experimental Fe coordination numbers below six suggest that Sb occupies positions near edges of the {111} faces. When SbV was reacted with magnetite, reduction to SbIII increased linearly between pH 4.5 and 6.5, with little influence of reaction time. The SbIII produced by the surface reaction formed the same surface complex as after direct addition of SbIII.
In the presence of mackinawite, SbV was completely reduced to SbIII within 30 d and in the pH range 4.3 - 8.4. The local structure shows SbIII surrounded by three sulfur atoms at a distance of 2.5 Å as in Sb2S3. The lack of more distant atomic shells suggests a highly dissordered structure. Again the resulting surface complex is the same as after direct addition of SbIII. Cryo-XPS measurements of shock-frozen samples show that the S 2p spectra remain unchanged before and after SbV reduction, while a FeIII-shoulder emerged in the Fe 2p spectra after reduction, indicating that SbV was reduced by FeII and not by S. In no case, reduction to an oxidation state below III was observed.

[1] Scheinost et al., Geochim. Cosmochim. Acta 70 (2006) 3299-3312. [2] Scheinost & Charlet, Environ. Sci. Technol. (2008) online. [3] Gallegos et al., Environ. Sci. Technol. 41 (2007) 7781-7786. [4] Powell et al., Environ. Sci. Technol. 38 (2004) 6016-6024.
Keywords: antimony, reduction, mackinawite, magnetite
  • Abstract in refereed journal
    Geochimica et Cosmochimica Acta 72(2008)12, A476

Publ.-Id: 11261 - Permalink


Electronic transport in magnetically ordered Mn5Si3Cx films
Gopalakrishnan, B.; Sürgers, C.; Montbrun, R.; Singh, A.; Uhlarz, M.; von Löhneysen, H.;
Mn5Si3Cx films exhibit antiferromagnetic or ferromagnetic behavior depending on the carbon doping level x. We report a detailed electronic-transport study of films prepared with different x. All films exhibit metallic behavior of the temperature-dependent resistivity ρ(T) with a logarithmic increase towards low temperatures attributed to the structural disorder and the accompanied scattering of conduction electrons by two-level systems. Below 1 K, the Kondo-type behavior ρ(T)~−ln T shows a crossover to Fermi-liquid behavior ρ−T2 independent of the type of magnetic order. The magnetoelectronic properties such as Hall effect and magnetoresistance show clear differences characteristic for the different magnetically ordered phases, i.e., antiferromagnetic vs ferromagnetic.
  • Physical Review B 77(2008), 104414

Publ.-Id: 11260 - Permalink


The Atomic Layer Deposition of HfO2 and ZrO2 using advanced metallocene precursors and H2O as an oxidant
Dezelah, C. L.; Niinistö, J.; Kukli, K.; Munnik, F.; Lu, J.; Ritala, M.; Leskelä, M.; Niinistö, L.;
The atomic layer deposition of HfO2 and ZrO2 thin films was investigated using (CH3C5H4)2Hf(CH3)2, (CH3C5H4)2Hf(OCH3)(CH3), (CH3C5H4)2Zr(CH3)2, and (CH3C5H4)2Zr(OCH3)(CH3) precursors at deposition temperatures between 300 and 500 °C using water vapor as the oxidant. A surface-limited growth mechanism was confirmed at 350 °C for all metal precursors examined. The processes provided nearly stoichiometric HfO2 and ZrO2 films with carbon and hydrogen concentrations below 0.5 and 1.0%, respectively, for representative samples. All films were polycrystalline as deposited and possessed a thin interfacial SiO2 layer. The capacitance-voltage and current density-voltage behavior is reported and discussed for capacitor structures containing films from this study.
Keywords: ALD, hafnium oxide, zirconium oxide, cyclopentadienyl (Cp) complexes, high-k dielectric

Publ.-Id: 11259 - Permalink


Prozessautomatisierung des Versuchsstandes TOPFLOW des Forschungszentrums Dresden Rossendorf
Lenk, S.; Carl, H.; Beyer, M.;
Der Vortrag beschreibt das Steuerungs- und Messdatenerfassungssystem der Versuchsanlage TOPFLOW. Beginnend bei der ursprünglichen Konfiguration des Automatisierungssystems werden die bis heute ausgeführten Erweiterungen und Optimierungen ausführlich erläutert. Des Weiteren beinhaltet der Vortrag Erklärungen zu den an TOPFLOW eingesetzten Hardware- und Softwarelösungen. Außerdem werden die Systemdokumentation und Maßnahmen zur Qualitätssicherung erklärt. Ausgewählte Beispiele zur Anlageninstrumentierung und Erläuterungen zur online Berechnung wichtiger thermo-physikalischer Stoffdaten schließen den Beitrag ab.
Keywords: process automation, OPC interface, ethernet communication, interbus
  • Lecture (others)
    Frühjahrstagung der Studiengruppe für Elektronische Instrumentierung, 07.-09.04.2008, Karlsruhe, Deutschland

Publ.-Id: 11258 - Permalink


Speciation and coordination of U(VI) and U(IV) sulfate in aqueous solution
Hennig, C.;
The abandoned uranium mine Königstein near Dresden/Germany, where uranium ore has been leached by sulfuric acid, is even nowadays concerned from the problem of heavy metal mobility affecting adjacent aquifers used for recovering drinking water. A rising interest can be observed worldwide to use such in situ leaching techniques to obtain uranium from ore mines. At the other hand, the thermodynamics of uranium in presence of high sulfate concentration is actually not well understood, especially under reduced conditions. The extended Debye-Hückel formalism, commonly used to estimate the species distribution and to correct activity coefficients, is above the validity limit in case of high ionic strength originated by the sulfuric acid. The specific ion interaction theory (SIT) and the Pitzer model are useful at higher ionic strengths but partly not to the extent in the directly concerned rock areas. In this study were combined therefore EXAFS, HEXS, XRD, TRLFS and UV-vis spectroscopy to extract the species distribution and the coordination of U(VI) and U(IV) sulfate complexes from model systems with low pH values and high sulfate concentrations [1-3]. For that purpose a spectro-electrochemical cell has been constructed that allowed the investigation of the solutions under controlled redox conditions. The study revealed that in contrast to neutral pH conditions, where U(VI) is highly soluble but U(IV) is nearly insoluble, even U(IV) becomes highly soluble at low pH by forming stable complexes resulting in an enlarged migration capacity.

[1] C. Hennig, K. Schmeide, V. Brendler et al.: EXAFS investigation of U(VI), U(IV), and Th(IV) sulfato complexes in aqueous solution. Inorg. Chem. 46, 5882 (2007).
[2] C. Hennig, W. Kraus, F. Emmerling et al.: The coordination of a U(IV) sulfate monomer in aqueous solution and in solid state, Inorg. Chem. 47, 1634, (2008)
[3] C. Hennig, A. Ikeda, K. Schmeide et al.: The relationship of monodentate and bidentate coordinated uranium(VI) sulfate in aqueous solution. Radiochim. Acta, submitted.
Keywords: Uranium, Sulfat, U(IV), U(VI), EXAFS, HEXS, XRD, TRLFS,UV-vis
  • Lecture (Conference)
    Uranium Mining and Hydrogeology V, 14.-18.09.2008, Freiberg, Germany

Publ.-Id: 11257 - Permalink


Coordinatiom of actinides in aqueous sulfate solution
Hennig, C.; Ikeda, A.; Tsushima, S.; Le Naour, C.; Den Auwer, C.; Wilson, R.;
Structural information on the sulfate coordination of actinides in aqueous solution is actually rather scarce. At the other hand there is often a high sulfuric acid concentration in the environment mines containing pyrite, because pyrite, exposed to aerobic conditions, undergoes a weathering followed by sulfuric acid release. An artificial source of sulfate in natural environment is in situ leaching, so-called solution mining, where sulfuric acid is injected into the ore deposit, as has been used especially for uranium mining in sandstone formations. Due to the lack of information on the coordination of sulfate with actinides in aqueous solution, we investigated Th(IV), Pa(V), U(IV), U(VI), Np(IV), Np(V) and Np(VI) complexes in aqueous sulfate solution by L3-edge EXAFS, high energy x-ray scattering (HEXS), and UV-Vis spectroscopy using samples of 10-50 mM of actinide and total sulfate concentrations, 0.05 ≤ [SO42-] ≤ 10 M. In contrast to the coordination of actinides with carbonate where bidentate coordination always prevails, the coordination with sulfate comprises monodentate and bidentate linkage with a wide variety of combinations. In general, with increasing [SO42-]/[Ann+] ratio the bidentate coordination becomes dominant in solution. As example, at low [SO42-]/[UO22+] ratio, where the UO2SO4(aq) species prevails, the sulfate coordinates in a monodentate and only to a less extend in bidentate fashion. At high [SO42-]/[UO22+] ratio, where UO2(SO4)22- species prevails, bidentate sulfate coordination with the species [UO2(SO4)2bid]2- becomes dominant [1]. In oxidation state IV, up to five coordinating sulfate groups have been observed, mostly with predominant bidentate coordination as for example in the high-charged complex [U(SO4bid)3(SO4mon)2]6- [2]. Pa(V) shows in high excess of sulfate a coordination of monodentate and bidentate sulfate, e.g. the complex [PaO(SO4bid)2(SO4mon)3]7- [3]. Np(IV) and Np(VI) follows the tendency of U(IV) and U(VI), whereas Np(V) is weakly coordinated by sulfate, in accordance with its low formation constant. The attempt to preserve solution species in crystal structures led in most of the cases to a rearrangement of bidentate sulfate groups in solution to monodentate–bridging coordination in solid state. The coordination of the solution complexes was optimized by DFT calculation and the results were compared with the experimental observations.


[1] C. Hennig, K. Schmeide, V. Brendler, H. Moll, S. Tsushima, A.C. Scheinost, Inorg. Chem. 46, 5882, 2007.
[2] C. Hennig, W. Kraus, F. Emmerling, A. Ikeda, A.C. Scheinost, 47, 2987, 2008
[3] C. Le Naour, D. Trubert, M.V. Di Giandomenico, C. Fillaux, C. Den Auwer, P. Moisy,C. Hennig, Inorganic Chemistry 44, 9542, 2005
Keywords: Th, Pa, U, Np, sulfate, EXAFS, HEXS, UV-vis, XRD
  • Lecture (Conference)
    Plutonium Futures "The Science" 2008, 07.-11.7.2008, Dijon, France

Publ.-Id: 11256 - Permalink


Infrared absorption strengths of ion-implanted hydrogenated amorphous silicon
Danesh, P.; Pantchev, B.; Schmidt, B.;
Silicon and hydrogen ion implantations have been used to affect the absorption of the infrared stretching modes in hydrogenated amorphous silicon (a-Si:H). Hydrogen ions have been implanted with ion energy of 16 keV and the doses in the range of 2.2 x 1014 -7.2 x 1016 cm-2. Silicon ion implantation has been carried out with the energy of 160 keV and the doses in the range of 9.5 x 1012 cm-2 -1.7 x 1015 cm-2. The a-Si:H films have been prepared by plasma-enhanced chemical vapor deposition. Nuclear reaction analysis has been used for the determination of the hydrogen concentration in the as-deposited and ion-implanted samples. It has been established that the values of the absorption strengths of stretching modes of the isolated monohydrides, A(2000), and clustered hydrogen forms, A(2100), are not equal and remain constant for all ion implantation doses. A(2100) has been considered as a weighted average of the absorption strengths of polyhydrides and clustered monohydrides, A(2100,SiHx) and A(2100,(SiH)n). It has been established that the ion implantation does not induce any change in the ratio between polyhydrides and clustered monohydrides. It has been suggested that the absorption strengths do not vary when a post-deposition treatment of samples is associated with the introduction of structural defects in the amorphous silicon network.
Keywords: hydrogenated amorphous silicon, ion implantation, infrared absorption spectroscopy, nuclear reaction analysis
  • Thin Solid Films 516(2008)10, 3383-3386

Publ.-Id: 11255 - Permalink


Bacteria –Actinide Interactions: an Environmental Perspective
Merroun, M.; Selenska-Pobell, S.;
Soils, sediments, and waters heavily polluted with radionuclides and other toxic metals, are a reservoir of unusual bacteria well adapted to these toxic environments. These bacteria possess fascinating mechanisms for interaction with and bio-transformation of radionuclides and other heavy metals, thus regulating the mobility of the metals in the environment. Microorganisms can mobilize radionuclides and metals through autotrophic and heterotrophic leaching, chelation by microbial metabolites and siderophores, and methylation, which can result in volatilization. Conversely, immobilization can result from sorption to cell components or exopolymers, intracellular sequestration, or precipitation as insoluble organic and inorganic compounds, e.g. oxalates, sulfides, or phosphates. The present work is intended to give a brief overview of the key processes implicated in the interaction of uranium with bacterial strains isolated from different extreme environments including uranium mining waste piles as well as groundwater of a radioactive repository. For this purpose, a combination of spectroscopic (EXAFS, XANES, TRLFS), microscopic (TEM), microbiological and wet chemistry techniques is used. Elucidating the interaction mechanisms microbe/metals is helpful for understanding the role which bacteria play in the transport and mobility of toxic metals in the environment as well as their biotechnological application in the bioremediation of heavy metal contaminated waters.
  • Lecture (Conference)
    38èmes Journées des Actinides 2008, 12.-15.04.2008, Wroclaw, Poland

Publ.-Id: 11254 - Permalink


Search for exotics in γD => φnp reactions near threshold
Titov, A. I.; Kämpfer, B.;
We discuss coherent and incoherent -meson photoproduction off the deuteron at low energy and small momentum transfer with the aim to check whether the recent experimental data need for their interpretation an inclusion of exotic channels. Our analysis of the differential cross-section and spin-density matrix elements shows that new data on the D → X reaction at Eγ ∼ 2GeV may be understood on the basis of conventional dynamics.

Publ.-Id: 11253 - Permalink


Untersuchung von lateralen und vertikalen Elementverteilungen mittels Kernmikrosonde
Grambole, D.; Herrmann, F.; Klabes, R.; Böhmert, J.; Klemm, W.; Plier, F.;
Die Kernmikrosonde, die am 5 MV Tandembeschleuniger des Zentralinstituts für Kernforschung Rossendorf installiert ist und über eine laterale Auflösung von ca. 4 µm für 3 MeV Protonen verfügt, wurde zur Mikrobereichsanalytik in der Medizin, Werkstofforschung und Geologie eingesetzt. Tiefenprofile von F im menschlichen Zahnschmelz und von O in Zr-Legierungen wurden bestimmt. Mikroeinschlüsse fester und flüssiger Phasen im Quarz wurden ebenfalls analysiert.

Investigation of lateral and vertical element distributions by means of nuclear microprobe:
The nuclear microprobe at the5 MV tandem accelerator of the Central Institute for Nuclear Research Rossendorf with a lateral resolution of about 4 µm for 3 MeV protons was used for microanalysis in medicine, material science, and geology. Depth profiles of F in human tooth enamels and of O in Zr alloys were determined. Microinclusions of solid and fluid phases in quartz were also investigated.
  • Beiträge zur elektronenmikroskopischen Direktabbildung und Analyse von Oberflächen 23(1990), 263-266

Publ.-Id: 11252 - Permalink


Protonenmikrosonde am Rossendorfer Tandemgenerator
Gersch, H.-U.; Grambole, D.; Herrmann, F.; Thomas, H.-J.;
Der Aufbau einer Protonenmikrosonde am Rossendorfer Tandemgenerator wird beschrieben. Testmessungen bei einer Energie von 3 MeV ergaben eine Auflösung von etwa 4 µm bei einem Strahlstrom von etwa 200 pA.

The development of a protonen microprobe at the Rossendorf tandem generator is described. A resolution of about 4 µm with a beam current of 200 pA was reached during first measurements at an energy of 3 MeV.
  • Experimentelle Technik der Physik 30(1982)3, 227-234

Publ.-Id: 11251 - Permalink


Hydrogen determination by means of the 1H(19F,α y) 16O and 1H(15N,α y) 12C resonance reactions
Rudolph, W.; Bauer, C.; Gippner, P.; Grambole, D.; Heiser, C.; Herrmann, F.; Thomas, H.-J.;
Hydrogen surface contamination and depth profiles can be measured by the resonant nuclear reactions 1H(19F,α y) 16O and 1H(15N,α y) 12C. The method was applied to study hydrogen-implanted silicon, amorphous silicon layers and silicon oxide films produced by anodic oxidation.
  • Journal of Radioanalytical and Nuclear Chemistry 83(1984)1, 99-105

Publ.-Id: 11250 - Permalink


Phase diagram and binding energy of interacting Bose gases
Männel, M.; Morawetz, K.; Schreiber, M.; Lipavský, P.;
From the many-body T-matrix the condition for a medium-dependent bound state and its binding energy is derived for a homogeneous interacting Bose gas. This condition provides the critical line in the phase diagram in terms of the medium-dependent scattering length. Separating the Bose pole from the distribution function the influence of a Bose condensate is discussed and a thermal minimum of the critical scattering length is found.
Keywords: BEC, phase diagramm, interacting Bose gases, bound states
  • Physical Review B 78(2008), 054508-1-054508-5

Publ.-Id: 11247 - Permalink


Fluorine determination in the near-surface region of solids using the 19F(p,p'y)19F resonance reaction
Grambole, D.; Bauer, C.; Gippner, P.; Heiser, C.; Rudolph, W.; Thomas, H.-J.;
Fluorine surface contamination and depth profiles were studied using the 19F(p,p'y)19F resonance reaction. Fluorine implanted silicon samples as well as ZrNb plates and Cr-Al layers after a HF-treatment have been examined. The resonance strengths of the narrow 1088 keV resonance were estimated.
  • Journal of Radioanalytical and Nuclear Chemistry 83(1984)1, 107-115

Publ.-Id: 11246 - Permalink


PECVD Si nitride and Si oxide layers - hydrogen analysis and etching after ion implantation
Neelmeijer, C.; Schmidt, B.; Rudolph, W.; Münzer, H.; Grambole, D.; Heiser, C.; Herrmann, F.;
Ion-implantation-induced selective etching of dielectric materials is considerably diminished with increasing hydrogen content.
Making use of the 1H(15N,αy)12C resonance reaction, low-temperature PECVD Si oxide and Si nitride layers were observed to
contain 12 and 23 at.% H, respectively. For different reagents etch rates were measured regarding the virgin and ion-implanted - He+, Ne+ at 60, 100 keV - PECVD films.
  • Nuclear Instruments and Methods in Physics Research B 50(1990), 439-443

Publ.-Id: 11245 - Permalink


Favorable Conditions of Θ+ Formation in γD Reaction
Titov, A.; Kämpfer, B.; Daté, S.; Ohashi, Y.;
We show that a Θ+ signal may appear in the [γD, pK−] missing mass distribution in inclusive γD → pK−X reaction when the pK− pair is knocked out in the forward direction and its invariant mass is close to the mass of Λ(1520). We show that the conditions of the recent CLAS experiment reduce the Θ+ formation probability making it difficult to extract a Θ+ peak from the data.
  • Open Access LogoProgress of Theoretical Physics 168(2007), 86-89

Publ.-Id: 11244 - Permalink


Dynamo action and magnetorotational instability: cosmic magnetism in the liquid metal lab
Stefani, F.;
It is widely known that cosmic magnetic fields are produced by the hydromagnetic dynamo effect. Yet it is less well known that cosmic magnetic fields play an active role in cosmic structure formation by means of the magnetorotational instability (MRI). The last ten years have seen tremendous efforts in studying both effects in the laboratory. In 1999, magnetic field self-excitation was observed nearly simultaneously in the liquid sodium facilities in Riga and Karlsruhe. Recently, self-excitation was also obtained in the French "von Karman sodium" (VKS) experiment, although with the help of iron propellers. The helical MRI was recently studied in the ''Potsdam Rossendorf Magnetic Instability Experiment'' (PROMISE), and an improved version of this experiment (PROMISE 2) has provided sharper transitions between stable and unstable regimes. In the talk, the history of dynamo and MRI experiments is delineated, and some interesting directions of future work are discussed.
  • Invited lecture (Conferences)
    MHD fundamentals, from liquid-metals to astrophysics, 14.-16.04.2008, Bruxelles, Belgium

Publ.-Id: 11243 - Permalink


Plastic foils as primary hydrogen standards for nuclear reaction analysis
Rudolph, W.; Bauer, C.; Brankoff, K.; Grambole, D.; Grotzschel, R.; Heiser, C.; Herrmann, F.;
Plastic materials like polypropylene, polyester (Mylar) and polycarbonate (Lexan or Makrofol E) contain large amounts of hydrogen and their compositions are well known. However, these materials are not stable during ion bombardment. Using the 1H(15N,αγ)12C and 1H(19F, αγ)16O nuclear resonance reaction at energies EN = 6.50 MeV and EF = 6.83 MeV, respectively, we have investigated the behaviour of plastic foils during 15N and 19F ion bombardment. By means of a rotating sample holder low current densities of 1–2 nA/cm² and large irradiated foil areas of up to 10 cm² were realized. Under these measuring conditions the γ-ray yields change only slightly and the initial yields, which correspond to the known compositions of the foils, can be determined with good accuracy. In this way the plastic foils can be used as primary standards for hydrogen content calibration. The method was employed to calibrate an a-Si(H) reference target.
  • Nuclear Instruments and Methods in Physics Research B 15(1986), 508-511

Publ.-Id: 11242 - Permalink


Void measurement in boiling water reactor rod bundles using high resolution gamma ray tomography
Bieberle, A.; Hoppe, D.; Zippe, C.; Schleicher, E.; Tschofen, M.; Suehnel, T.; Zimmermann, W.; Hampel, U.;
We present a high resolution gamma ray computed tomography (CT) system for the measurement of the void distribution in sub-channels in an electrically heated fuel rod bundle at the thermal hydraulic test loop KATHY (AREVA NP GmbH, Germany). This measurement system generates cross-sectional void fraction profiles through the pressure vessel for true-to-scale fuel rod bundles operating under typical nuclear reaction conditions and in steady state. Measurements are non-invasive, thus the two-phase flow in the bundle is not influenced. The gamma ray computed tomography system consists of a collimated 137Cs isotopic source, a gamma radiation detector arc including 320 single elements and a pulse processing unit. The average spatial resolution of the CT system is about 3 mm in plane and 8 mm axial. The thermal design of the detector arc is optimised to keep the temperature of internal components constant under changing environmental conditions. A specially developed gantry was constructed to realise vertical positioning and continuous rotation of the CT system. To determine the void fraction distribution a two-point calibration method is used. Here, data sets at zero and one hundred percent void fraction are required. The non-superposed slice image is generated using the filtered back projection reconstruction algorithm.
Keywords: high resolution gamma ray tomography, void fraction determination
  • Contribution to proceedings
    XCFD4NRS - Experiments and CFD Code Applications to Nuclear Reactor Safety, 10.-12.09.08, Grenoble, France
    PaperNo BOI-06
  • Lecture (Conference)
    XCFD4NRS - Experiments and CFD Code Applications to Nuclear Reactor Safety, 10.-12.09.08, Grenoble, Frankreich

Publ.-Id: 11241 - Permalink


Eta-prime meson production in nucleon-nucleon collisions near the threshold
Kaptari, L. P.; Kämpfer, B.;
The production of eta' mesons in the reactions pp to ppeta' and pn to pn eta' at threshold-near energies is analyzed within a covariant effective meson-nucleon theory. The description of cross section and angular distributions of the available data in this kinematical region in the pp channel is accomplished by including meson currents and nucleon currents with the resonances S_{11}(1650), P_{11}(1710) and P_{13}(1720). Predictions for the pn channel are given. The di-electron production from subsequent eta' Dalitz decay eta' to gamma gamma^* to gamma e^+e^- is also calculated and numerical results are presented for intermediate energy and kinematics of possible experiments with HADES, CLAS and KEK-PS.

Publ.-Id: 11240 - Permalink


Investigating the ESBWR stability with experimental and numerical tools: a comparative study
Rohde, M.; Marcel, C. P.; Manera, A.; van der Hagen, T. H. J. J.; Shiralkar, B.;
In this work, the stability of the Economic Simplified Boiling Water Reactor (ESBWR) has been studied by using a Freon-134a based experimental facility (GENESIS) and two system codes, being ATHLET 2.0a and (to a lesser extent) TRACG. During setting up the GENESIS facility and the numerical calculations, a great effort has been made to approximate the ESBWR system as accurate as possible.
In general, it was found that a sufficient margin to instability exists regarding the ESBWRs nominal point. In addition, a comparison was made between the numerical and experimental results for both the thermal-hydraulic system and the reactor system. Deviations were found between the numerical and experimental results, in spite of the close similarity between the GENESIS facility and the definition of the ESBWR system in the system code. This result shows that predictions regarding real nuclear reactors, based on modeled systems, should be taken with care.

Publ.-Id: 11239 - Permalink


Quantum well infrared photodetector array development and applications
Schneider, H.;
Quantum well infrared photodetector (QWIP) technology has opened up new opportunities to realize focal plane arrays (FPA) for high-performance thermal imaging [1]. High thermal and spatial resolution, low 1/f noise, low fixed-pattern noise, and high pixel operability makes QWIP FPAs appropriate for many applications. Due to their narrow absorption bands with relative spectral widths of the order of 10%, QWIPs are particularly suitable for thermal imaging applications involving several atmospheric transmission bands or several colors within the same band. In this talk, I will report on the development of QWIP structures optimized for thermal imaging applications and on the performance of QWIP cameras which were jointly realized by the Fraunhofer-Institute for Applied Solid State Physics (Freiburg, Germany) and AIM Infrarot-Module GmbH (Heilbronn, Germany). Besides imagers for the 8 – 12 micron long-wavelength infrared (LWIR) and 3 – 5 micron mid-wavelength infrared (MWIR) regimes, a LWIR/MWIR dual-band QWIP FPA will also be discussed.
[1] H. Schneider and H. C. Liu, Quantum Well Infrared Photodetectors: Physics and Applications, ISBN 3540363238, Springer Series in Optical Sciences Vol. 126, 2007.
Keywords: quantum well infrared photodetector, QWIP
  • Lecture (others)
    Seminarvortrag, Shanghai Institute of Technical Physics, Chinese Academy of Science, 24.03.2008, Shanghai, China
  • Lecture (others)
    Seminarvortrag, Suzhou Institute of Nano-tech and Nano-bionics, Chinese Academy of Science, 27.03.2008, Suzhou, China
  • Lecture (others)
    Seminarvortrag, Institute of Semiconductors, Chinese Academy of Science, 02.04.2008, Beijing, China

Publ.-Id: 11238 - Permalink


TEM, SANS and PAS applied to neutron-irradiated pure Fe
Hernández Mayoral, M.; Bergner, F.; Almazouzi, A.; Lambrecht, M.;
Irradiation-induced microstructural features in pure Fe were investigated by a triple of methods: TEM, SANS and PAS. In the talk it will be analyzed, if and how the features detected by the individual techniques reflect themselves in the output of each other method. This information is used in order to derive a coherent picture of irradiation damage in pure Fe.
  • Lecture (Conference)
    14th Meeting of the International Group on Radiation Damage Mechanisms (IGRDM-14), 20.-25.04.2008, Pittsburgh, United States

Publ.-Id: 11237 - Permalink


Flux dependence of cluster formation in neutron irradiated weld material
Bergner, F.; Ulbricht, A.; Hein, H.;
SANS results for an RPV weld material irradiated at two different neutron fluxes up to the same neutron fluence will be presented. We have observed a remarkable effect of flux on the size of irradiation-induced clusters. A rate theory model is applied in order to give a tentative explanation for the findings. Interestingly, the mechanical properties do not show a corresponding flux effect. The results will be faced with observations for another RPV steel exhibiting a different behaviour.
  • Lecture (Conference)
    14th Meeting of the International Group on Radiation Damage Mechanisms (IGRDM-14), 20.-25.04.2008, Pittsburgh, USA

Publ.-Id: 11236 - Permalink


Double photoexcitation involving 2p and 4f electrons in L3-edge x-ray absorption spectra of protactinium
Hennig, C.; Le Naour, C.; Den Auwer, C.;
The L3-edge x-ray absorption spectrum of Pa(V) fluoride in aqueous solution show clear evidence for the double photoexcitation involving 2p and 4f electrons. A comparison with the [2p4f] double-electron excitations observed in the L3-edge x-ray absorption spectra of other actinides (thorium, uranium, neptunium, plutonium and americium) indicates a monotonic increase of the excitation energy. The sharp edge-like structure of the multielectron excitation reveals the origin of a shake-up channel.
Keywords: [2p4f] double-electron excitation, protactinium

Publ.-Id: 11235 - Permalink


Experiments on slug mixing under natural circulation conditions at the ROCOM test facility using high resolution measurement technique and numerical modeling
Kliem, S.; Höhne, T.; Rohde, U.; Weiß, F.-P.;
ROCOM is a four-loop test facility for the investigation of coolant mixing in the primary circuit of pressurized water reactors. Recently, a new sensor was developed for an improved visualisation and quantification of the coolant mixing in the downcomer. This new sensor spans a dense measuring grid and covers nearly the whole downcomer. In the presented work, special emphasis was given to the comparison of the data of this sensor with the results of calculations using the CFD code ANSYS CFX. A coolant mixing experiment during natural circulation conditions has been conducted. The underlying scenario of this experiment is based on a boron dilution scenario following a SBLOCA event. The corresponding CFD code solution has been obtained using the Best Practice Guidelines. All main effects observed in the measurement are described by the calculation. The detailed comparison reveals that the calculation underestimates the coolant mixing inside the reactor pressure vessel.
The measurement data, boundary conditions of the experiment and facility geometry can be made available to other CFD code users for benchmarking.
  • Lecture (Conference)
    XCFD4NRS - Experiments and CFD Codes Application to Nuclear Reactor Safety, 10.-12.09.2008, Grenoble, France
  • Contribution to proceedings
    XCFD4NRS - Experiments and CFD Codes Application to Nuclear Reactor Safety, 10.-12.09.2008, Grenoble, Frankreich
    Proceedings of the XCFD4NRS - Experiments and CFD Codes Application to Nuclear Reactor Safety, CDROM
  • Nuclear Engineering and Design 240(2010)9, 2271-2280
    DOI: doi:10.1016/j.nucengdes.2009.11.015

Publ.-Id: 11234 - Permalink


Advanced two-phase flow measurement techniques at Research Centre Dresden-Rossendorf - sensors, systems and applications
Hampel, U.;
Understanding and modelling of two-phase flow is a key issue in nuclear engineering and in many other engineering fields. The Research Centre Dresden-Rossendorf is, amongst others, engaged in safety research for nuclear light water reactors and performs combined experimental and theoretical work on two-phase flow phenomena. In the frame of this work considerable effort has been spent in the past to develop innovative two-phase flow measuring techniques. Special focus has been given to imaging techniques which are able to resolve phase distributions at high temporal and spatial resolution. The presentation introduces the most advanced of these techniques, including different types of wire-mesh sensors, gamma ray tomography and ultra fast electron beam tomography and discusses application of such techniques and systems in basic research as well as industrial applications.
Keywords: Two-phase flow, flow measurement
  • Invited lecture (Conferences)
    Meeting der Industrial Tomography Systems Ltd., 01.04.2008, Manchester, UK
  • Invited lecture (Conferences)
    Frontier Seminar at Institute of Particle Science and Engineering, Leeds University, 2.4.2008, Leeds, UK
  • Invited lecture (Conferences)
    Research Seminar, School of Chemical, Environmental and Mining Engineering, Nottinhgam University, 3.4.2008, Nottingham, UK
  • Invited lecture (Conferences)
    Research Seminar, Nuclear Physics Group, Positron Imaging Centre, Birmingham University, 4.3.2008, Birmingham, UK

Publ.-Id: 11233 - Permalink


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