Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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32227 Publications
The inverse approach to Magnetofluiddynamics
Gerbeth, G.;
Today there are two developments for an inverse approach to liquid metal
magnetohydrodynamics. At first, the reconstruction of a three-dimensional
velocity field out of external magnetic field measurements. At second, the
design of tailored magnetic field actions specific for the heat- and mass
transfer needs of the corresponding process. Results for both methods are
presented. The application to the steel flow in the mould are discussed.
  • Lecture (others)
    Lecture at ABB Process Industries, Västeras, Sweden, 27.03.2001

Publ.-Id: 3911 - Permalink


Parametrische Bildgebung von [18F]OMFD Hirn-PET-Studien
Hinz, R.; Bredow, J.;

Ziel:
Das Aminosäurederivat 3-O-methyl-6-[18F]fluoro-L-DOPA ([18F]OMFD) zeigt eine hohe Aufnahme in Hirntumoren im Gegensatz zum normalen Hirngewebe. Ziel dieser Arbeit war die Generierung parametrischer Datensätze des Tracer-Verteilungsraumes in der Positronen-Emissions-Tomographie (PET).
Methodik:
Nach vorangegangener Transmissionsmessung für die Schwächungs- und Streukorrektur wurden dynamische PET-Aufnahmen mit 34 Frames innerhalb von 90 Minuten auf einem hochauflösenden Scanner ECAT EXACT HR+ nach der intravenösen Gabe von 330 MBq [18F]OMFD akquiriert. Zur Reduktion des Rauschens wurden die Bilder nach der iterativen Rekonstruktion mit einem Savitzky-Golay-Filter geglättet. Die Angebotsfunktion wurde entweder extern aus gemessenen venösen Blutproben oder nichtinvasiv aus der A. carotis interna bestimmt. Eine Korrektur auf Metabolite ist bei
[18F]OMFD nicht erforderlich. Für die Erzeugung parametrischer Bilder wird das Eingewebs-Kompartimentmodell zur Beschreibung des kinetischen Verhaltens reversibler Tracer benutzt. Pixelweise werden die Einstromkonstante K1, die Eliminationskonstante k2 und das anteilige Blutvolumen fbv geschätzt. Das Verteilungsraumvolumen Vd des Tracers wird als Quotient von k1 und k2 bestimmt.
Ergebnisse:
In den parametrischen Bildern des Verteilungsraumvolumens ist eine klarere Abgrenzung maligner Areale als in den Aktivitätsverteilungen möglich. Der Wert von Vd ist ein Indikator für die Aminosäuretransporteraktivität in den Zellen, von der angenommen wird, dass sie in Tumorzellen gegenüber Normalgewebe erhöht ist. Das Verhältnis der Vd-Werte von Tumor zu Nichttumor lag bei dem untersuchten Patientenkollektiv zwischen 2,2 : 1 und 3,2 : 1.
Schlussfolgerungen:
Die Berechnung der Verteilungsraumkoeffizienten Vd führt zu einer Quantifizierung onkologischer PET-Studien mit [18F]OMFD, mit der zahlenmäßige Aussagen bei Verlaufskontrollen und interindividuelle Vergleiche möglich werden.

Keywords: Positronen-Emissions-Tomographie Modellierung
  • Lecture (Conference)
    39. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin Hamburg 25.04. - 28.04.2001

Publ.-Id: 3910 - Permalink


Post Test CFD Calculations of Experiments at the ROCOM Mixing Test Facility related to Boron Dilution and Cold Water Transients
Höhne, T.; Rohde, U.; Prasser, H.-M.;
The temperature and boron concentration fields established by the coolant mixing during nominal and transient flow conditions in the reactor pressure vessel of the PWR Konvoi were analyzed by numerical and experimental studies. The validation of the CFD results (CFD-code CFX-4) was carried out at the Rossendorf mixing test facility ROCOM. ROCOM is a 1:5 scaled Plexiglas model of the PWR Konvoi allowing velocity measurements by the LDA technique. Plugs of coolant with low boron acid concentration and/or different temperature are simulated by salt water injection. The CFD calculations were based on the assumption of incompressible turbulent flow. The turbulence was considered by an k--model. The perforated drum, as well as the reactor core with core internals, were represented by the model of a porous body. Calculations were performed for constant flow in the loops as well as for the scenario of an onset of the circulation. For transient CFD-calculation sensitivity studies were performed to check the numerical diffusion and the choice of different turbulence models.
Keywords: Boron Dilution, Coolant Mixing, CFD, PWR
  • Lecture (Conference)
    CFX Users Conference 2001,28-30 May 2001, Berchtesgaden
  • Contribution to proceedings
    CFX Users Conference 2001,28-30 May 2001, Berchtesgaden

Publ.-Id: 3909 - Permalink


Modellierung des Kernkraftwerks Stade Vorarbeiten für Rechnungen mit dem Programm RALOC Mod 4.0AG Teil 1: Zonen, Verbindungen, Strukturen
Krüssenberg, A.-K.; Schaffrath, A.;
Grundlage für die Erstellung des Eingabedatensatzes ist die Nodalisierung, eine Unterteilung des Containments in Bilanzräume (sog. Zonen), die über definierte Strömungswege (sog. Junctions) miteinander verbunden sind. Für die Zonen werden während einer Rechnung Massen- und Energiebilanzen, für die Verbindungen hingegen Impulsbilanzen aufgestellt und gelöst. Zusätzlich können mit Hilfe von sog. wärmeleitenden Strukturen Wärmequellen und -senken definiert werden. Diese erlauben die Modellierung der Zufuhr von Wärme in bzw. die Abfuhr von Wärme aus einzelnen Zonen sowie die Berechnung von Temperaturprofilen in festen Materialien (z.B. Wänden, Einbauten, Armaturen, Leitungen, Komponenten) sowie des Wärmeübergangs an deren Oberflächen.
  • Other report
    FWS 01-1, April 2000

Publ.-Id: 3908 - Permalink


16Alpha-[18F]fluor-17Beta-Estradiol (FES) und [18F]FDG-PET zur präoperativen Diagnostik bei Mamma-Carcinom
Bredow, J.; Richter, B.; Beuthien-Baumann, B.; Römer, J.; Füchtner, F.; Distler, W.; Franke, W.-G.;
ZIEL:
Patientinnen (Pat.) mit hochgradigem V.a. Mamma-CA wurden präoperativ mit FES oder FDG untersucht. Ziel war die Beurteilung von Multizentrizität, axillärem Lymphknotenbefall und Estrogenrezeptorstatus (ER) bzw. metabolischen Aktivität mittels PET sowie der Vergleich mit den histologischen Befunden incl. Estrogenrezeptorstatus.

METHODIK:
Die Pat. wurden radomisiert mit FDG oder FES im klinischen Stadium =pT2 an einem dedizierten PET-System (ECAT EXACT HR+, SIEMENS/CTI) untersucht. FES: Injektion von ca. 220 MBq i.v., 2 bed positions ab Axiallae bis Oberbauch in Bauchlage (Lagerungshilfe) ab 90 min p.i., anschließend ab prox. Oberschenkel bis Schädelbasis in Rückenlage, jeweils mit gemessener Transmissionskorrektur im 2D-Modus. FDG: Injektion von 290-370 MBq i.v., ab 60 min p.i. gleiche Aufnahmeparameter wie bei FES.

ERGEBNISSE:
Es wurden bisher 5 Pat. mit FES und 4 Pat. mit FDG untersucht (Tabelle). Erste Daten zeigen für FES und FDG eine positive Carcinomdarstellung auch bei Multizentrizität. Bei einer Pat. fand sich mittels FES ein falsch-positiver bzw. ein falsch negativer Befund bezüglich der axillären LK und des Estrogenrezeptorstatus.

Lfd...Diagnose postoperativ....Präparat......PET:... .ER.. ..Vergleich PET - Histologie
Nr.........................................................T/LKall...[%]
....................................................................................T.......MZ.......LKax......ER......SUV

1......pT4NxM1G3L1 (MZ)......FDG.............+/-........0.......RP......RP.......(FN).................2,0
2......pT4bN1M1G2...............FES..............-/-........0.......RN......RN........RN.......RN.......0,2
3......pT2N0M0G2L0V0.........FDG..............+/-.......0.......RP......RN........RN...................6,8
4......pT2N1M0G3L1 (MZ)......FES..............+/+...>80......RP......RP........RP.......RP.......4,3
5......pT2M0M0G2L0V0.........FES..............+/-....>80......RP......RN........RN.......RP.......1,5
6......pT4N1M1G3L1.............FDG..............+/+.....20......RP......RP........RP..................4,5
7......pT2N0M0 Dcis (MZ)......FDG..............+/-.......0.......RP......RN........RN..................1,8
8......pT2N1M0L1V1 (MZ)......FES..............+/-.......0.......RP......RP........FN.......FP.......1,6
9......pT4NxM1 (MZ).............FES..............+/+....>90......RP......RP.......(RP)......RP.......7,3

SCHLUSSFOLGERUNGEN:
Erste mittels FES in Deutschland durchgeführte Untersuchungen weisen auf die Eignung zur präoperativen Diagnostik des Mamma-CA hin. Eine abschließende Beurteilung ist bei kleiner Fallzahl noch nicht möglich.
  • Poster
    39. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, Hamburg, 25.-28.4.2001
  • Abstract in refereed journal
    Nuklearmedizin 40 (2001) A82

Publ.-Id: 3907 - Permalink


4. Workshop "Measurement techniques for stationary and transient multiphase flows", Rossendorf, November 16 - 17, 2000
Prasser, H.-M.; (Editor)
In November 2000, the 4th Workshop on Measurement Techniques for Stationary and Transient Multiphase Flows took place in Rossendorf. Three previous workshops of this series were national meetings; this time participants from different countries took part. The programme comprised 14 oral presentations, 9 of which are included in these proceedings in full length. A special highlight of the meeting was the main lecture "Ultrasonic doppler method for bubbly flow measurement" of Professor Masanori Aritomi, Dr. Hiroshige Kikura and Dr. Yumiko Suzuki, which was read by Dr. Hiroshige Kikura. The workshop again dealt with high-resolution phase distribution and phase velocity measurement techniques based on electrical conductivity, ultrasound, laser light and high-speed cinematography. A number of presentations were dedicated to the application of wire-mesh sensors developed by FZR for different applications used by the Technical Universities of Delft and Munich and the Tokyo Institute of Technology. The presentations were in particular:

M. Aritomi, H. Kikura, Y. Suzuki (Tokyo Institute of Technology): Ultrasonic doppler method for bubbly flow measurement

V. V. Kontelev, V. I. Melnikov (TU Nishny Novgorod): An ultrasonic mesh sensor for two-phase flow visualisation

A. V. Duncev (TU Nishny Novgorod): Waveguide ultrasonic liquid level transducers for power generating equipment

H.-M. Prasser, E. Krepper, D. Lucas, J. Zschau (FZR), D. Peters, G. Pietzsch, W. Taubert, M. Trepte (Teletronic Ingenieurbüro GmbH), Fast wire-mesh sensors for gas-liquid flows and decomposition of gas fraction profiles according to bubble size classes

D. Scholz, C. Zippe (FZR): Validation of bubble size measurements with wire-mesh sensors by high-speed video observation

A. Manera, H. Hartmann, W.J.M. de Kruijf, T.H.J.J. van der Hagen, R.F. Mudde, (TU Delft, IRI): Low-pressure dynamics of a natural-circulation two-phase flow loop

H. Schmidt, O. Herbst, W. Kastner, W. Köhler (Siemens AG KWU): Measuring methods for the investigation of the flow phenomena during external pressure vessel cooling of the boiling water reactor SWR1000

A. Traichel, W. Kästner, S. Schefter, V. Schneider, S. Fleischer, T. Gocht, R. Hampel (HTWS Zittau/Görlitz - IPM): Verification of simulation results of mixture level transients and evaporation processes in level measurement systems using needle-shaped probes

S. Richter, M. Aritomi (Tokyo Institute of Technology): Methods for studies on bubbly flow characteristics applying a new electrode-mesh tomograph

Keywords: multiphase flow, measurement instrumentation, workshop, transient flow
  • Open Access LogoWissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-320 Mai 2001

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Publ.-Id: 3906 - Permalink


Non-volatile memories based on Si+ - implanted Gate oxides
Gebel, T.; von Borany, J.; Thees, H.-J.; Wittmaack, M.; Stegemann, K.-H.; Skorupa, W.;
Electrical properties of 20 ... 30 nm gate oxides implanted with Si+ ions are investigated using MOS capacitors and transistor structures. The observed programmming window can reach several volts and the structures exhibit good retention behavior. A first 256k - nvSRAM is demonstrated showing a programming window >1V for write pulses of 12V / 8 ms.
Keywords: nanocrystal, ion implantation, non-volatile memory
  • Microelectronic Engineering 59 (2001) 247-252
  • Lecture (Conference)
    INFOS Conference 2001, 20.-23.06.2001, Udine (Italy)

Publ.-Id: 3904 - Permalink


Die Sorption des Uran(VI) und anderer radiotoxischer Schwermetalle an Kolloidpartikeln im Flutungswasser des Uranbergwerks Königstein
Zänker, H.; Richter, W.;
Das untersuchte Flutungswasser (pH 5,5) enthält Fe(II), welches bei Sauerstoffzutritt Fe(III)-Oxyhydroxidpartikel bildet. Diese Partikel adsorbieren Radionuklide wie Po-210 und Pb-210. Im pH-Bereich von 4 bis 6 wird auch der größte Teil des Urans, welches in sechswertiger Form vorliegt, sorbiert. Radium dagegen ist kaum kolloidgetragen.

Keywords: colloids, particles, uranium, radium, polonium, iron oxyhydroxides, sorption
  • Lecture (others)
    Vortrag Universität Jena, Fachbereich Geologie der Universität Jena, 19. April 2001

Publ.-Id: 3903 - Permalink


TRIDYN_FZR User Manual
Möller, W.; Posselt, M.;
The present report contains the User Manual of the FZR version of the dynamic binary-collision computer simulation code TRIDYN. The present version of the code is based on TRIDYN Vs. 4.0 by W.Möller and W.Eckstein, Department of Surface Physics, Max-Planck Institute of Plasma Physics, Boltzmannstraße 2, 85748 Garching, Germany (1989). Modifications, in particular for PC implementation, quasi-dynamic display and the input dialog have been performed at the Institute of Ion Beam Physics and Materials Research by V.Kharlamov, T.Schwieger, M.Posselt, and W.Möller (1995-2001).
  • Open Access LogoWissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-317 April 2001

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Publ.-Id: 3902 - Permalink


Pulsed Electron-Beam Melting of High-Speed Steel: Structural Phase Transformations and Wear Resistance
Ivanov, Y.; Matz, W.; Rotshtein, V.; Günzel, R.; Shevchenko, N.;
The structural and phase transformations occurring in the near-surface layers of pre-quenched high-speed steel subjected to pulsed electron beam melting have been investigated. Melting was induced by a low-energy (20–30 keV), high-current electron beam with a pulse duration of 2.5 µs and an energy densities ranging from 3 to 18 J/cm2. Using electron microscopy and x-ray diffraction it has been revealed that with increasing beam energy density gradual liquid-phase dissolution of initial globular M6C carbide particles occurs in the near-surface layer of thickness up to ~1 µm. This process is accompanied by formation of martensite crystals (gamma-phase) and an increase of residual austenite (alpha-phase) content. When the carbide particles are completely dissolved, martensitic transformation is suppressed. In this case, a nonmisoriented structure is formed consisting predominantly of submicron cells of -phase separated by nanosized carbide interlayers. Irradiation of cutting tools (drills) in a mode corresponding to an abrupt decrease in the content of M6C particles due to their liquid-phase dissolution enhances the wear resistance of the drills by a factor of 1.7. This is associated with the fixation of undissolved particles in the matrix, the formation of residual compressive stresses and of dispersed M3C carbide particles as well as the high (~50 %) content of the metastable -phase in the surface layer.
Keywords: steel, electron beam melting, scanning electron microscopy, X-ray diffraction, transmission electron microscopy, wear resistance
  • Surface & Coatings Technology 150 (2002) 188-198

Publ.-Id: 3901 - Permalink


Infrarotspektroskopie von Halbleiter-Quantenstrukturen: vom Modellsystem zum Infrarot- und THz-Bauelement
Helm, M.;
please contact the author
Keywords: Infrarotspektroskopie, Halbleiter
  • Lecture (others)
    Kolloquiumsvortrag am Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, Berlin (9.4.2001)

Publ.-Id: 3900 - Permalink


Energy dependence of quantum dot formation by ion sputtering
Facsko, S.; Kurz, H.; Dekorsy, T.;
Ordered quantum dot patterns are generated on GaSb and InSb surfaces due to a
surface instability induced by Ar+ ion sputtering under normal incidence.
The characteristic length of the generated patterns scales with the square
root of the ion energy over the energy range of 75 - 1800 eV. This energy
dependence is compared to the solutions of the isotropic Kuramoto-Sivashinsky
equation and allows the determination of the lateral width of the energy
distribution deposited by the incident ions in the very low energy range. We
show that the observed energy dependence is in agreement with the linear
continuum theory under the assumption that the dominant smoothing process is
due to effective ion induced diffusion without mass transport on the surface.
Keywords: self-organization ion sputtering quantum dots surface roughening
  • Physical Review B 63 (2001) 165329 -1-5

Publ.-Id: 3898 - Permalink


Institute of Ion Beam Physics and Materials Research; Annual Report 2000
von Borany, J.; Jäger, H.-U.; Helm, M.; Möller, W.; Wieser, E.;
Summary of the Scientific Activities of the Institute in 2000
Keywords: Highlight Reports, Short Contributions, Statistics
  • Open Access LogoWissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-314 März 2001

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Publ.-Id: 3897 - Permalink


Synthesis of [1,2-14C]Trichloroacetic acid
Bubner, M.; Fuksora, K.; Matucha, M.; Heise, K.-H.; Bernhard, G.;
Modern trends in investigating the phytotoxic effects of trichloroacetic acid (TCA) have initiated an actual interest in [1,2-14C]TCA with specific activities > 3.7 GBq/mmol. One-pot synthesis starting from potassium [1,2-14C]acetate yielding 80% of [1,2-14C]TCA is described. The specific activity of the product corresponds to that of the potassium or sodium [1,2-14C]acetate and the radiochemical purity is higher than 98%. The synthesis method is usable for the synthesis scale < 1 mmol.
Keywords: Key Words: [1,2-14C]trichloroacetic acid, one-pot synthesis
  • Labelled Comp. Radiopharm

Publ.-Id: 3896 - Permalink


ROBL - A synchrotron radiation beamline for Radiochemistry and Materials Research
Matz, W.; Schell, N.; Eichhorn, F.; Prokert, F.; Reich, T.; Funke, H.; Berberich, F.;
The Forschungszentrum Rossendorf has built a synchrotron radiation beamline at the ESRF, Grenoble, for radiochemistry and materials research. The radiochemistry set-up at ROBL is the only dedicated station in Europe for XAS experiments on actinides in solid or liquid samples. The materials end station is mainly for diffraction and reflectometry studies on thin films and has capabilities for in-situ experiments in film growth or temperature induced structural changes. The possibilities for materials research at ROBL are demonstrated by some experiments performed.
Keywords: synchrotron radiation, ROBL, EXAFS instrumentation, X-ray diffraction, thin films, reflectivity, in-situ experiments, ion implantation
  • Lecture (Conference)
    2nd International Workshop JINR Synchrotron Radiation Source (DELSY-2001), 02.-06.04.2001, Dubna, Russia

Publ.-Id: 3893 - Permalink


Studies of the development of texture in TiN films by use of in situ synchrotron x-ray scattering
Schell, N.; Matz, W.; Bottiger, J.; Chevallier, J.; Kringhoj, P.;
During growth the micro-structural development of TiN films was studied – especially the change in texture with film thickness. The films were deposited by use of a magnetron sputtering source in a vacuum chamber equipped with two magnetron sources and mounted on a goniometer located at a synchrotron radiation beam line. X-ray diffraction and reflectivity measurements were carried out in situ to follow the microstructure as a function of film thickness. With the deposition parameters that were chosen, a crossover was observed: grains with a (002) plane parallel to the film surface dominate at small thickness, while, at larger thickness, (111) grains dominate. Recrystallization was identified as a mechanism that controls this texture development. The driving force for change of orientation of the individual grains arise from minimalization of the sum of the surface energy and the strain energy of the individual grains.
Keywords: thin film growth, sputter deposition, texture developments, TiN, in-situ experiments, synchrotron radiation
  • Journal of Applied Physics 91, No. 4, (2002) 2037-2044

Publ.-Id: 3892 - Permalink


Influence of dose rate and temperature on ion-beam-induced defect evolution in Si investigated by channeling implantation at different doses
Posselt, M.; Bischoff, L.; Teichert, J.;
A focused ion beam system is applied to study the dose dependence of the shape of Ge channeling implantation profiles at two very different dose rates (1018 and 1011 cm-2 s-1), and for implantation temperatures of 2500C and RT. A simple model for the buildup of radiation damage is developed to describe the dechanneling effect of defects formed during ion bombardment. The use of this model in atomistic computer simulations yields Ge depth profiles which agree well with measured data. The lifetime of ion-beam-induced defects at 2500C was estimated to be in the order of 100 s. At RT, some defect relaxation was found between 10 microseconds and 100 s after ion impact.
Keywords: ion implantation, radiation damage, channeling, computer simulation
  • Applied Physics Letters Vol. 79 , Nr. 10 (2001) 1444-1446

Publ.-Id: 3891 - Permalink


Investigation of Si-nanocrystal memory structures obtained by r.f. sputtering
Schmidt, J. U.;
Currently effects related to carrier confinement in nanometer sized silicon structures are extensively studied. So it has been shown that Si in spite of its indirect band
gap can efficiently emit photons due to carrier recombination provided that low dimensionality is achieved. Further a novel Si-nanocrystal floating gate MOSFET
memory structure has been proposed. In all these applications the formation of Si-quantum dots is a critical step being tackled using a variety of methods. Our
approach is rf magnetron sputtering, a popular thin film preparation technique compatible with conventional Si-technology and providing an elegant way to prepare
device quality SiO2 thin-films, but also SiO2/nanocrystalline (nc)-Si/SiO2 thin-film systems. SiO2 films were prepared by sputtering from an high purity quartz
target and characterized by TEM, FTIR, Current-Voltage and Capacitance-Voltage measurements. The electrical properties of the sputtered oxide films are
comparable to those of thermally grown oxides. By alternate sputtering from Si and SiO2-targets thin-film systems have been prepared. For the latter charge
storage in the nc-Si-floating gate has been demonstrated.
Keywords: silicon,nanocrystal,MOS,Capacitance-voltage measurements,sputtering,memory
  • Lecture (Conference)
    Tagung der Deutschen Physikalischen Gesellschaft, Hamburg 26. - 30. März 2001 Fachverband Dünne Schichten (DS 19.3)

Publ.-Id: 3887 - Permalink


Step Edge Diffusion and Step Atom Detachment in Surface Evolution: Ion Erosion of Pt(111)
Michely, T.; Kalff, M.; Comsa, G.; Strobel, M.; Heinig, K.-H.;
The temperature dependent morphological evolution of Pt(111) under 1 keV Xe normal
incidence ion bombardment has been investigated up to 600 monolayers removed.
Coarsening of the surface structures during erosion and a qualitative change in
roughness evolution between 650 and 700 K are found to be caused by different
atomic processes: the former by diffusion of atoms along steps, the latter by the
onset of step atom detachment.
Keywords: Ion Erosion, platinum, STM, kinetic Monte-Carlo simulation
  • Physical Review Letters 86 (2001) 2589

Publ.-Id: 3886 - Permalink


Nanostructured Arrays Formed by Finely Focused Ion Beams
Zuhr, R. A.; Budai, J. D.; Datskos, P. G.; Meldrum, A.; Thomas, K. A.; Warmack, R. J.; White, C. W.; Feldman, L. C.; Strobel, M.; Heinig, K.-H.;
Nanoparticles can be formed in a variety of substrates by ion implantation and
thermal annealing. These particles range from a few to several hundred nanometers
in diameter and may be metals or semiconductors containing either single or multiple elements. Particles formed in this way are not uniform in size and are randomly
distributed throughout the implant region. The purpose of this work is to make
uniformly spaced lattices of colloidal particles of more uniform size by using a finely
focused ion beam to implant ions only into a microscopic region at each point of
a two-dimensional array. Simulations using a kinetic
lattice Monte Carlo code indicate that such implants should form localized distributions of colloids that may Ostwald ripen into a single large colloid at each
lattice site. Such a composite would exhibit greatly improved optical characteristics. Initial work is being done with 30 keV Ga and As in Si. Particle formation
as a function of implant and annealing conditions will be discussed
Keywords: nanostructure, focused ion beam, ion beam synthesis
  • Lecture (Conference)
    American Physical Society, Centennial Meeting March 20-26, 1999, Atlanta, GA, USA

Publ.-Id: 3885 - Permalink


Strong electroluminescence of Sn-implanted silicon dioxide layers
Rebohle, L.; von Borany, J.; Fröb, H.; Gebel, T.; Skorupa, W.;
The blue-violet electroluminescence (EL) of Sn-implanted SiO2 layers thermally grown on crystalline Si has been investigated at room temperature and compared with the corresponding photoluminescence (PL) spectra. It was shown that power efficiencies up to 2.5·10-4 can be achieved, and that the power efficiency slightly decreases for high injection currents. Because of the excellent correspondence between the EL and the PL spectra we interpreted the EL as due to a radiative triplet-singlet transition of a Sn-related oxygen deficiency center. Based on the electrical measurements, we assume that the luminescence centers will be excited either by impact excitation of hot electrons moving in the conduction band of SiO2 or by field ionization of luminescence centers in conjunction with hopping conduction.
Keywords: electroluminescence tin implanted silicon dioxide
  • Mat. Sci. Eng. C 19 (2001) 373

Publ.-Id: 3884 - Permalink


Nitrogen incorporation and loss during ion nitriding of Al
Telbizova, T.; Chevolleau, T.; Möller, W.;
Ion nitriding of Al has been performed by a N2 reactive ion beam using a hot filament ion source. Quantitative determination of N incorporation and loss has been estimated at a beam energy of 1.6 keV with two ion current densities of 0.1 and 0.2 mA/cm2 and substrate temperature of 350°C. For this purpose, a characterisation of the ion beam has been carried out by an energy selective mass spectrometer. The analysis shows that the beam consists solely of N2+ and N+ ions with a composition of about 80 % and 20 %, respectively. The ion energy distribution of both N2+ and N+ consists of a single narrow peak with a full width at half maximum of about 10 eV and a mean ion energy corresponding to the applied beam potential. From the beam parameters, N loss due to sputtering and backscattering has been calculated using dynamic binary collision computer simulations. After an initial transient, the stationary partial sputtering yield of N is predicted to be 0.45, while the amount of backscattered N is about 5 % of the incident N fluence. The N loss obtained from the simulation is consistent with the incident fluence and the total amount of incorporated N measured by Nuclear Reaction Analysis (NRA).
Keywords: ion source, ion nitriding, sputtering yield, backscattering, Al, AlN
  • Nuclear Instruments and Methods in Physics Research B 184 (2001) p. 347

Publ.-Id: 3881 - Permalink


Autoradiographische Untersuchungen zu 5-HT1A und 5-HT2A- Rezeptoren nach sozialer Isolation
Schiller, L.; Kretzschmar, M.; Brust, P.; Oehler, J.;
Frühere Untersuchungen haben gezeigt, dass im Verlaufe sozialer Isolation - tierexperimentelles Modell gestörten Sozialkontaktes - serotonerge Alterationen Anteil an den neurobiologischen Veränderungen haben, die den auffälligen Verhaltensänderungen
zugrunde liegen. Die durch Bindungsassays nachgewiesenen Veränderungen von KD und Bmax Werten serotonerger Rezeptorpopulationen deuten an, dass eine Reihe lokaler quantitativer Veränderungen serotonerger Rezeptoren in verschiedenen Hirnregionen zu erwarten sind .
Mittels autoradiographischer Untersuchungen wurde die lokale Verteilung von spezifischen Rezeptorpopulationen, insbesondere von 5-HT1A und 5-HT2A Rezeptoren im Cortex, Hippocampus, Amygdala, Striatum und N. acccumbens verfolgt. Nach 28 Tagen zeigt sich eine massive Abnahme der 5-HT1A Rezeptordichte im Cortex, Hippocampus, Substantia nigra und in der Amygdala , die auch weitestgehend nach 12 Wochen Isolation noch nachweisbar ist. Die Dichte der 5-HT2A Rezeptoren ist ebenfalls nach 28 Tagen in den untersuchten Hirnregionen signifikant vermindert, während nach 12 Wochen kaum noch Veränderungen nachgewiesen werden können. In der Tendenz ist im Striatum und im N.accumbens sogar eine up-Regulation zu erkennen. Die Ergebnisse werden in Beziehung zu neurochemischen und Verhaltensveränderungen diskutiert.
  • Poster
    3. Mitteldeutsche Psychiatrie-Tage, Magdeburg, 15.-17.03.2001

Publ.-Id: 3879 - Permalink


Anwendung des Instrumentierten Kerbschlagbiegeversuch zur Ermittlung von Referenztemperaturen nach dem Master-Curve-Konzept
Viehrig, H.-W.; Böhmert, J.; Dzugan, J.;
The instrumented impact test is suitable for the determination of fracture mechanical pa-rameters. In this paper the determination of the dynamic fracture toughness values in the lower ductile-to-brittle transition region is presented. The fracture toughness is determined at the onset of cleavage fracture and evaluated by the Master Curve (MC) concept. The MC concept allows to quantify the variation of fracture toughness with the temperature within the lower ductile-to-brittle transition region. Limit curves of fracture toughness for defined fail-ure probabilities and a reference temperatures can be determined using this method. This paper presents the application of the master curve concept to the reference temperature de-termination through the thickness of reactor pressure vessel (RPV) steel plate. The reference temperatures determined with dynamic fracture toughness values (T0dy) are compared with quasi-static reference temperatures (T0st) and Charpy-V transition temperatures (TT). The T0dy, T0st and TT increase from the surface to the middle of the RPV steel plate. Compared with T0st, the T0dy values are higher approximately 70 to 90 K.
Keywords: reactor pressure vessel steel, instrumented impact testing, J integral,fracture toughness, dynamic loading, Master Curve
  • Materialwissenschaft und Werkstofftechnik, Vol. 32, No. 6, June 2001, pp. 568-573

Publ.-Id: 3878 - Permalink


Simultaneous preparation of 16alpha-[18F]fluoroestradiol-sulphamates in an automated module. A high-yield procedure for 16alpha-[18F]fluoroestradiol-17beta-sulphamate
Römer, J.; Füchtner, F.; Steinbach, J.; Kasch, H.;
After successful synthesizing 16alpha-[18F]fluoroestradiol-3,17beta-disulphamate in an automatic procedure, we studied the conditions for obtaining 16alpha- [18F]fluoroestradiol-mono-sulphamates in a similar manner. The described procedure can simultaneously provide approximately 3 GBq of 16alpha-[18F]fluoroestradiol-3-sulphamate and 1 GBq of 16alpha-[18F]fluoroestradiol-17beta-sulphamate of high radiochemical purity. By treating 16alpha-[18F]fluoroestradiol-3,17beta-disulphamate with Kryptofix 2.2.2 and potassium carbonate, 16alpha-[18F]fluoroestradiol-17beta-sulphamate also becomes available at high radioactivity.
Keywords: fluorine-18; nucleophilic fluorination; sulphamoylation; automated synthesis; PET tracer
  • Poster
    14th International Symposium on Radiopharmaceutical Chemistry, Interlaken/Schweiz, 10.-15.06.2001
  • Journal of Labelled Compounds and Radiopharmaceuticals 44 (2001) 689-700

Publ.-Id: 3877 - Permalink


Synthesis and host-guest properties of multi-crown-dendrimers towards sodium pertechnetate and mercury(II) chloride
Stephan, H.; Spies, H.; Johannsen, B.; Gloe, K.; Gorka, M.; Vögtle, F.;
Multi-crown-dendrimers of four different generations have been synthesized by grafting 4, 8, 16 and 32 benzo[15]crown-5 units at the periphery of POPAM-dendrimers. The binding of sodium pertechnetate and mercury(II) chloride by the multi-crown-dendrimers has been studied by liquid-liquid extraction using the radioactive probes 22Na+, 99TcO4-, and 203Hg2+. The third- and fourth-generation dendrimers 3 and 4, in particular, are capable of extracting mercury(II) with high efficiency ( ca. 12 HgII ions per dendrimer molecule, even at low generation). It has been shown that the guest molecules investigated preferentially encapsulated inside the dendrimers.


Keywords: dendrimers; crown compounds; pertechnetate; mercury; solvent extraction
  • Eur. J. Inorg. Chem. (2001) 2957-2963

Publ.-Id: 3876 - Permalink


Novel technetium(III) mixed-ligand chelates for the design of lipophilic complexes stable in vivo
Pietzsch, H.-J.; Seifert, S.; Drews, A.; Syhre, R.; Spies, H.; Leibnitz, P.; Tisato, F.; Refosco, F.;
The most frequently used technetium compounds suitable for coupling the metal to biologically active molecules are square-pyramidal oxo complexes based on tetradentate N2S2 ligands (1). Properties and thus the in vivo behaviour of such complexes are strongly influenced by the presence of the quite polar [Tc=O]3+ unit. Whether such a polarity is beneficial or not is not obvious and depends on the requirements for specific radiotracers, e.g. for receptor-targeting agents or for metabolic tracers. Another crucial point in tracer design is the stability of the respective Tc chelate towards ligand exchange in vivo. Recently it was shown that the applicability of the "3+1" mixed-ligand Tc(V) chelates is limited because of their reaction with glutathione in vivo (2,3). So there is a considerable interest in alter-native chelate systems that combine lower polarity with enhanced in vivo stability. Such systems are based on oxo-free Tc cores at lower oxidation state.
Here we describe novel types of Tc(III) mixed-ligand complexes. Both chelate systems fulfil the requirements for a lipophilic, non-polar building block stable against ligand exchange reaction in vivo. They offer the advantage of high versatility in conjugating biomolecules as described for the "3+1"-series (4).

Keywords: Tc-99m, Tc(III) mixed-ligand complexes, thiolato ligands, isocyanides, phosphines
  • Lecture (Conference)
    14th International Symposium on Radiopharmaceutical Chemistry, Interlaken/Schweiz, 10.-15.06.2001
  • Abstract in refereed journal
    Journal of Labelled Compounds and Radiopharmaceuticals 44 Suppl.1, (2001), S39-S41

Publ.-Id: 3875 - Permalink


Synthesis and autoradiographical evaluation of novel high-affinity Tc-99m ligands for the serotonin 5-HT1A receptor
Drews, A.; Heimbold, I.; Varnäs, K.; Hall, H.; Halldin, C.; Pietzsch, H.-J.; Syhre, R.; Seifert, S.; Brust, P.; Johannsen, B.;
Despite tremendous effort in the development of Tc-99m complexes to image post-synaptic CNS receptors, various attempts failed so far (1). The combination of sufficient brain uptake and high affinity to the receptors (IC50 < 1 nM) seems to be crucial. Our studies are focused on complexes for serotonin 5-HT1A and 5-HT2A receptors. Recently we succeeded in synthesizing of complex I, which is a high affinity Tc-99m ligand for the 5-HT1A receptor derived from the well known serotonin 5-HT1A antagonist WAY 100635 and shows a subnanomolar affinity (0.13 nM) and a brain uptake of 0.20 % ID in rats, 5 min post injection (2). Figure 1 shows the structure of the complex I.

Here we report on the synthesis of new high-affinity Tc-99m ligands for the 5-HT1A receptor with improved brain uptakes. The complexes are evaluated in receptor binding assays, by in vitro autoradiography in post mortem human brain and by in vivo studies.

Keywords: serotonin 5-HT1A receptor, Tc-99m receptor ligand, receptor binding assay, in vitro autoradiography
  • Poster
    14th International Symposium on Radiopharmaceutical Chemistry, Interlaken/Schweiz, 10.-15.06.2001
  • Abstract in refereed journal
    J. Labelled Cpd. Radiopharm. 44, Suppl. 1 (2001), S544-S546

Publ.-Id: 3874 - Permalink


Synthese, physikalisch-chemische Charakterisierung und Bestimmung der Löslichkeit von Erdalkaliuranyltricarbonato-komplexen M2[UO2(CO3)3].xH2O; M = Mg, Ca, Sr, Ba
Amayri, S.; Geipel, G.; Reich, T.; Bernhard, G.;
Uransekundärminerale sind in verschiedenen Uranerzbergbaugebieten (u.a. Schneeberg; Joachimstal, Adrinapole, Arizona) nachgewiesen worden. Aus der Kenntnis der Bildung von Erdalkaliuranylcarbonaten wie Bayleyit (M = Mg) und Liebigit (M = Ca) können wichtige Hinweise über den Transport und die Immobilisierung von Uran unter umweltrelevanten Bedingungen abgeleitet werden.
Ein Ziel der Arbeit war es, Syntheseverfahren für Ca-, Mg-, Sr- und Ba-Uranyltricarbonate zu erarbeiten bzw. zu optimieren und die Syntheseprodukte physikalisch-chemisch zu charakterisieren. Als Analysemethoden wurden Röntgendiffraktometrie, Elementaranalyse, ICP-MS, Thermoanalyse [1] durchgeführt. Desweiteren wurden die Produkte mit spektroskopischen Methoden wie IR, Raman, TRLFS und EXAFS untersucht.
Die Synthesen erfolgten in der Regel durch die Umsetzung von Uranylnitratlösung mit Erdalkalinitrat- oder -chloridlösung und Natriumcarbonat im pH-Bereich von 7 bis 8 [2]. Die charakterisierten Substanzen wurden für die Bestimmung ihrer Löslichkeit und für Speziationsuntersuchungen verwendet.
Hauptziel dieser Arbeit war die Bestimmung der Löslichkeit dieser Uranminerale, da bisher keine Daten bekannt sind. Die Löslichkeitsexperimente wurden bei 25°C im pH-Bereich von 7,0 bis 9,0 in 0,1 M NaClO4 - Lösung durchgeführt. Unter Gleichgewichtsbedingungen wurden die Festphasen mittels Röntgendiffraktometrie und die Lösungen mit TRLFS und EXAFS analysiert. Die Ergebnisse zeigten, daß bei pH 7,0 bis 9,0 die Minerale als Festphase vorliegen. Mittels TRLFS wurden in den Lösungen auch M2[UO2(CO3)3](aq)-Komplexe nachgewiesen.
Die Löslichkeit der Erdalkaliuranyltricarbonate vermindert sich in der Reihe von Magnesiumuranyltricarbonat (0.230 mol/l pH: 8,0) zum Bariumuranyltricarbonat (1.31x10-3 mol/l pH: 8,0) entscheidend [3]. Analoges Verhalten zeigt die Löslichkeit der entsprechenden Erdalkalicarbonate.


Literatur:

[1] J. Cejka; Reviews in Mineralogy (Uranium: Mineralogy, Geochemistry and the
Environment) volume 38,(1999) 521-622
[2] M. Bachelet , Cheylon E., Douis M.and Goulette G.; Bull. Soc. Chim. France 19 (3),
(1952) 565
[3] S. Amayri; Dissertation an der TU-Dresden in Vorbereitung (2001)
  • Lecture (Conference)
    GDCH-Tagung in Würzburg, 23.09.-29.09.2001

Publ.-Id: 3873 - Permalink


EXAFS investigations of erth alkaline metal uranyl tricarbonato complexes
Amayri, S.; Reich, T.; Bernhard, G.;
Carbonate and bicarbonate are the common anions found in significant concentrations in many natural waters, and they are strong complexation agents for actinide ions. Seepage, flooding and mining waters from the uranium mining area in the southeast of Germany (Saxony and Thuringia), contain relatively high amounts of magnesium, calcium, carbonate and sulfate ions. In these waters the pH values range from 7.0 to 8.0 and the uranium content is about 0.02 mmol/L where magnesium, calcium and carbonate concentrations are 11.6 mmol/L, 6.9 mmol/L and 3.9 mmol/L, respectively /1/.
Recently we were able to confirm the existence of the natural complexes Ca2UO2(CO3)3(aq) and Mg2UO2(CO3)3(aq) by spectroscopic measurements /2/.
We performed Extended X-ray Absorption Fine Structure (EXAFS) measurements at the uranium LIII- edge to study the structures of these complexes. The obtained results by EXAFS of these complex solutions are compared with those from the corresponding EXAFS and XRD data related to the secondary minerals of uranium, liebigite, Ca2[UO2(CO3)3]×10H2O and bayleyite, Mg2[UO2(CO3)3]×10H2O and they are in good agreement.

References:

/1/ Bernhard, G., G. Geipel, V. Brendler, H. Nitsche: Uranium speciation in waters of different
uranium mining areas, J. of Alloys and Compounds 201 (1998) 271-273.
/2/ Bernhard, G., G. Geipel, V. Brendler, H. Nitsche: Speciation of Uranium in Seepage Waters of a
Mine Tailing Pile Studied by Time-Resolved Laser-Induced Fluorescence Spectroscopy (TRLFS),
Radiochim. Acta 74 (1996), 87-91.
  • Poster
    Eurokonferenz Actinide-XAS-2000, 10.09.-12.09. 2000, Grenoble

Publ.-Id: 3872 - Permalink


Retention of the potential energy of multiply charged argon ions incident on copper
Kentsch, U.; Tyrroff, H.; Zschornack, G.; Möller, W.;

The retained fraction of the potential energy of argon ions incident on copper has been measured using stationary calorimetry at charge states up to 9+ and kinetic energies ranging from 75 eV and 240 eV per ionic charge. An average fraction of 30% to 40% is found with little dependence on the charge number and on the kinetic energy. The retention of the total energy ranges 60% to 75% and can mainly be accounted for by the retained fraction of the potential energy and the collisional energy lost by reflected ions and sputtered target atoms.

Keywords: PACS Nos. 61.80.Jh, 41.75.Ak, 79.20.Rf, 52.50.Gj
  • Physical Review Letters 87 (2001) 105504/1-4

Publ.-Id: 3871 - Permalink


Growth of low stress cubic boron nitride films by simultaneous medium energy ion implantation
Fitz, C.; Kolitsch, A.; Fukarek, W.; Möller, W.;
It is demonstrated that the intrinsic stress in cubic boron nitride films can be significantly relaxed during growth by simultaneous medium energy ion implantation. The stress in the growing film has been studied in-situ using cantilever curvature measurements and has been reduced to below 2 GPa by simultaneous Ar+ or N+ ion implantation with an energy of 70 keV and 35 keV, respectively. The resulting cubic boron nitride films show an increased long term stability. The results reveal that the stress in cBN is not reduced due to segregation of boron at grain boundaries.
Keywords: PACS Nos. 68.55.Jk, 68.55.Ln, 68.60.Bs, 81.15Jj, 61.80.Jh
  • Applied Physics Letters Vol. 80 Number 1 , 7 January 2002, 55-57

Publ.-Id: 3870 - Permalink


Interactions of three eco-types of Acidithiobacillus ferrooxidans with U(VI)
Merroun, M.; Selenska-Pobell, S.;
The interaction of uranium with cells of three recently described eco-types of Acidithiobacillus ferrooxidans recovered from uranium mining wastes was studied. The uranium sorption studies demonstrated that the strains from these types possess different capability to accumulate and tolerate uranium. The amount of uranium biosorbed by all A. ferrooxidans strains increased with increasing the concentration of uranium. We have found that the representatives of type II accumulate significantly higher amounts of uranium in comparison to the other A. ferrooxidans strains. The investigations of the tolerance to uranium showed that the types I and III are resistant to 8 and 9 mM of uranium respectively, whereas the type II does not tolerate more than 2 mM of uranium. The recovery of the accumulated uranium by desorption was investigated using various desorbing agents as sodium carbonate, sodium citrate and EDTA at different concentrations. Sodium carbonate was the most efficient desorbing agent, removing 97% of the uranium sorbed from the cells of A. ferrooxidans type III, and 88.33 and 88.50% from the cells of the types I and II, respectively.



  • Biometals 14 (2): 171-179 (2001)

Publ.-Id: 3869 - Permalink


EXAFS investigations of uranium (VI) interaction with bacteria
Hennig, C.; Panak, P. J.; Reich, T.; Raff, J.; Selenska-Pobell, S.; Roßberg, A.; Funke, H.; Merroun, M. L.; Bernhard, G.;
Mobilization of heavy metals in the environment due to industrial activities is of serious concern due to the toxicity of these metals in humans and other forms of life. Uranium is an example of these metals, and is considered one of the most seriously threatening heavy metals mainly because of its high toxicity, not so much radioactivity. Activities associated with the nuclear industry, mining and wastewater treatment have brought excessive amounts of uranium into the environment. In uranium deposits a number of acidophilic chemolithoautotrophic ( Acidithiobacillus ferrooxidans, for instance) bacteria have been identified which are able to oxidise sulphide minerals, elemental sulfur, ferrous iron. Sequence analysis of the 16S rRNA genes of several reference strains and uranium mining waste pile isolates of A. ferrooxidans revealed specific signatures which distinguish three types within the species. These types differ in their capability to accumulate and tolerate uranium /1/.
Uranium (VI) complexes formation at cell surfaces of A. ferrooxidans types was studied using uranium LIII-edge Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy. In all samples uranium is coordinated by two axial oxygen atoms (Oax) at distance of 1.77-1.78 Å. The average distance between uranium and the equatorial oxygen atoms (Oeq) is 2.35 Å. The coordination number for Oeq is 5-6.
Using U-C and U-P phase and amplitude functions, the third and the fourth peak in the FT of A. ferrooxidans give a distance of 2.91 and 3.58 ± 0.02Å, respectively. The latter is the same U-P bond distance as for the organic uranyl phosphate (U(VI)-ATP complex). But we do not exclude the possibility of implication of sulfur because these 2 elements (P and S) are close each other in the periodic system of elements and EXAFS can not distinguish between them. In addition, the P (or S) is bonded in a monodentate mode to the uranyl ion. A bidentate bounding would give a atomic distance of approximately 3.2 Å.
Moreover, no structural differences were observed between the uranium complexes formed by the 3 types of A. ferrooxidans. However, the EXAFS spectra are indicating a formation of uranium complexes which are different from those formed by Bacilli /2/.


/1/ M. Merroun et al., Interaction of three types of Acidithiobacillus ferrooxidans with uranium, Biometals (in preparation).
/2/ C. Hennig et al., EXAFS investigation of uranium(VI) complexes formed at Bacillus cereus and Bacillus sphaericus surfaces, Radiochim. Acta (in press).
  • Poster
    Second Euroconference and NEA Workshop on Speciation, Techniques, and Facilities for Radioactive Materials at Synchrotron Light Sources, Grenoble, Frankreich, 10.-12.09.2000

Publ.-Id: 3868 - Permalink


Die Bedeutung von Kolloiden in der aquatischen Umwelt. Ein Beitrag der AG "Kooloide" aus der Wasserchemie.
Hofmann, T.; Baumann, T.; Bundschuh, T.; Kammer, F.; Leis, A.; Schmitt, D.; Schäfer, T.; Thieme, J.; Totschke, K.-U.; Zänker, H.;
In den vergangenen Jahren wurde grundsätzlich akzeptiert, dass Kolloide unter bestimmten Randbedingungen einen erheblichen Beitrag zum Transport von Stoffen in aquatischen Systemen leisten können. Nach wie vor ist jedoch umstritten, welche Relevanz der kolloidale Transport bei einer Vielzahl von Fragestellungen hat.
  • Poster
    Jahrestagung Chemie 2001, Bad Wildungen 21.-23.5.

Publ.-Id: 3866 - Permalink


Plasma Diagnostic of a Plasma Immersion Ion Implantation Process for protecting TiAl Alloys against High Temperature Oxidation using Chlorine
Hornauer, U.; Günzel, R.; Richter, E.; Wieser, E.; Möller, W.; Dettenwanger, F.; Schütze, M.;
Plasma immersion ion implantation (PIII) from a chlorine containing plasma has been used in order to improve the high temperature oxidation behavior of titanium aluminide alloys. This process is promising since the subsurface Cl concentration, which is needed for optimum protection against oxidation, can be quickly obtained (approx. fluence 1·1016 Cl/cm-2) in a PIII process.
A PIII system being resistant against the strongly etching Cl2 plasma is presented. Plasma diagnostics of the Cl2 plasma sustained by an ICP source using Langmuir probe measurements is discussed. For the electro-negative Cl plasma, the measurements are examined regarding the influence of negative ions. The implantation of Cl is correlated to the plasma parameters using AES depth profiling of the surface after implantation. The high temperature oxidation behavior is tested using thermogravimetrical analysis (TGA) in air at 900 °C and microstructural investigations of the oxide scale. PIII implantations of Cl2 with 30 kV HV pulses (effective energy 15 keV) show a strong reduction of the oxidation at 900 °C in air, which is comparable to conventional beam line im-plantations of Cl at 15 keV.

Keywords: plasma diagnostic, langmuir, chlorine, Plasma immersion, TiAl, oxidation
  • Lecture (Conference)
    Plasma-Based Ion Implantation (PBII) 2001, 26-28.6. Grenoble, France

Publ.-Id: 3865 - Permalink


Investigation for Safer Initiation of Grignard Reactions
Hessel, G.; Hulzer, G.; Kryk, H.; Schmitt, W.;
Due to the spontaneous heat release during the initiation of the strongly exothermic Grignard reaction, these reactions dispose of considerable harzard potentials. Therefore, the knowledge of thermody-namic and thermokinetic parameters is one of the prerequisites for safe formation of Grignard rea-gents in production plants. To obtain more accurate results, these studies on the formation of Grignard reagents were carried out in a closed reaction calorimeter by dosing the pure bromobenzene deriva-tive for the first time. The molar reaction enthalpy per mole bromobenzene derivative was determined with a standard deviation of about 5%.
Keywords: Grignard reaction, Initiation, in-situ FTIR-specrometer
  • Lecture (Conference)
    Proceedings of the 3rd European Congress of Chemical Engineering, Nuremberg 26-28 June 2001, on ECCE-CD / Contents / 2. Sustainable Development, 2.2 Chemical Risk Management
  • Abstract in refereed journal
    Chemie Ingenieur Technik 73, 6 (2001) 611
  • Contribution to proceedings
    Proceedings of the 3rd European Congress of Chemical Engineering, Nuremberg 26-28 June 2001, on ECCE-CD / Contents / 2. Sustainable Development, 2.2 Chemical Risk Management

Publ.-Id: 3864 - Permalink


Mechanism for the generation of coherent longitudinal-optical phonons in GaAs/AlGaAs multiple quantum wells
Yee, K. J.; Lim, Y. S.; Dekorsy, T.; Kim, D. S.;
We show that coherent optical phonons in GaAs multiple quantum wells are generated in a completely different way compared to bulk GaAs. Unlike in GaAs where the ultrafast screening of electric fields by photogenerated charge carriers is known to be dominant, three distinctive generation mechanisms contribute simoultaneously in multiple quantum wells.
Keywords: coherent phonons, multiple quantum wells, femtosecond spectroscopy
  • Physical Review Letters 86 (2001) 1630-1633

Publ.-Id: 3862 - Permalink


Investigation of natural convection in large pools on the example of heating up the secondary side of an emergency condenser
Krepper, E.; Hicken, E. F.; Jaegers, H.;
Natural convection is a basic principle for a lot of industrial processes. As an example for the investigation of natural convection phenomena, the paper describes investigations of a passive heat removal system in advanced designs of nuclear power plants. The SWR1000 concept of Siemens AG includes emergency condensers. In the Research Centre Jülich at the NOKO test facility experiments were performed, to investigate the heat transfer capability under different operation modes. In the last time the heating up phenomena on the secondary side were investigated in detail. The paper describes simulations performed in the Forschungszentrum Rossendorf using the CFD-code CFX-4 of AEA-Technology and comparisons to the experiments. Performing additional calculations, measures to avoid undesired temperature stratification were investigated.
Keywords: natural convection, large pools, heating up experiments, CFD calculations, comparison experiment - calculations, influence of geometry effects
  • Lecture (Conference)
    Int. Conf. on "Advances in computational heat transfer", Palm Cove, Australien Mai 2001, Proc. Vol. 2, pp. 835-842
  • International Journal of Heat and Fluid Flow Vol. 23 (2002) pp. 359-365
  • Contribution to external collection
    Int. Conf. on "Advances in computational heat transfer", Palm Cove, Australien Mai 2001, Proc. Vol. 2, pp. 835-842

Publ.-Id: 3861 - Permalink


Irradiation effects on toughness behaviour and microstructure of VVER-type Pressure Vessel Steels
Böhmert, J.; Viehrig, H.-W.; Ulbricht, A.;
The irradiation sensibility and the annealing behaviour were studied on seven different heats from VVER 440 and VVER 1000-type reactor pressure vessel steels. The specimens were irradiated at the Rheinsberg prototype VVER 2 reactor to mean neutron fluences between 43 - 127.6A1018 n/cm² [E > 0.5 MeV] and afterwards toughness and strength properties were determined. In addition the microstructure was analysed using SANS technique. There is an obvious trend regarding the correlations between the irradiation-induced changes of transition temperature, hardness and volume fraction of microstructural features of the radius near of approx. 0 to 2 nm. The main parameters of influence are the neutron fluence and the nickel content. The nickel-containing VVER 1000-type pressure vessel steel is more sensible against irradiation than the VVER 440-type steel which has a low content of nickel. For the last one the sensibility against radiation embrittlement depends on content of copper and phosphorus. Annealing at 475 °C (100 h) reduces the irradiation effect but not completely in every case.
Keywords: Radiation embrittlement, reactor pressure vessel steel, small angle neutron scattering, microstructure
  • Journal of Nuclear Materials 297 (2001) 251-261

Publ.-Id: 3860 - Permalink


Axial Distribution of DD-Neutron Yield in GDT under Skew Injection of Deuterium Neutral Beams
Ivanov, A. A.; Anikeev, A. V.; Bagryansky, P. A.; Karpushov, A. N.; Kornilov, V. N.; Maximov, V. V.; Noack, K.;
Experiments with 3 MW deuterium injection have been carried out in the Gas Dynamic Trap (GDT) to simulate the axial profile of the fusion reaction intensity in the proposed neutron source based on the GDT. Quite narrow angular distribution function of the fast ions produced by an oblique neutral beam injection results in a peaked axial profile of the fusion yield. This strong peaking is essential to produce an intense neutron flux in the testing zones of the GDT-based neutron source.
The scintillation counters were installed in the central cell of the device to monitor the DD fusion reaction products: neutrons (2.45 MeV) and protons (3,02 MeV). They were closely located to the plasma column inside of the vacuum chamber in oreder to avoid contribution from the scattered neutrons and to improve the spatial resolution of the measurements. The axial profiles of the fusion neutrons and protons have been measured in the high-beta regime of the GDT operation.
In the paper the experimental data are compared with the results of numerical simulations. The conclusion may be drawn that the kinetics of the fast ion relaxation and scattering is determined by classical Coulomb collisions.
Keywords: fusion, 14 MeV neutrons, neutron source, gas dynamic trap, material irradiation, neutral beam injection, deuterium injection, DD fusion products, scintillation counters
  • Poster
    International Conference on Open Systems for Plasma Confinement, July 3-6, 2000, Tsukuba, Japan, Proc. in Transactions of Fusion Technology Vol. 39, p. 213 (2001)
  • Contribution to proceedings
    International Conference on Open Systems for Plasma Confinement, July 3-6, 2000, Tsukuba, Japan, Proc. in Transactions of Fusion Technology Vol. 39, p. 213 (2001)

Publ.-Id: 3857 - Permalink


Femtosecond-Laser-Induced Spectroscopy - A new tool to study interactions of actinides with organic ligands
Geipel, G.; Bernhard, G.; Rutsch, M.;
Laser induced spectroscopic methods are an excellent tool for the study of complex formation of actinides with various ligands at relatively low concentrations. Laser-induced Photoacoustic spectroscopy and Time-resolved Laser-induced Fluorescence spectroscopy are well-known methods. These methods are inappropriate for metal ions which show no change in their spectroscopic properties with complexation. In the case of organic actinide complexes it is possible to use the dependence of fluorescence of the organic ligands on actinide concentration in order to determine complex formation constants. The fluorescence lifetimes of organic ligands in aqueous solution at room temperature are below 20 ns. To study fluorescence properties of theses organic substances laser systems with ultrashort pulses are inevitable. We, therefore, have installed a femtosecond-laser-induced fluorescence spectroscopy system in our laboratory.
The lasersystem provides femtosecond laserpulses in the wavelength range from 250 nm to 10 µm and a pulse duration of 130 fs. The repetition rate is 1 kHz. The emitted fluorescence signal is detected with an intensified CCD camera, with gate width between 80 ps and 6 ns. The delay for time resolved spectra can be adjusted between 0 and 20 ns after the laser pulse with stepwidth down to 25 ps.
We validated this time-resolved laser-induced fluorescence system by studying the fluorescence behavior of salicylic acid and 5-sulfosalicylic acid at pH 4.0 as function of the uranium(VI) concentration. Using a static quenching mechanism the complex formation constants are calculated to be log KI=0.1M= -1.12 ± 0.03 for salicylic acid and log KI=0.1M= -0.67 ± 0.08 for 5-sulfosalicylic acid, respectively, assuming a 1:1 complex formation. The data from the NIST database /1/ are log KI=0.1M= -1.0 and log KI=0.1M= -0.72, respectively. For the actinides neptunium and plutonium much less data are available. Complex formation constants of various substituted benzoic acids with these actinide elements are reported.

/1/ A.E. Martel, R.M. Smith and R.J. Motekaitis: NIST Critically Selected Stability Constants of Metal
Complexes Database Version 5.0; 1998

  • Lecture (Conference)
    Migration 2001, 16.-21.09.2001, Bregenz, Österreich

Publ.-Id: 3856 - Permalink


Protection of TiAl alloys against high temperature oxidation by Chlorine Plasma Immersion Ion Implantation
Hornauer, U.; Günzel, R.; Richter, E.; Wieser, E.; Möller, W.; Dettenwanger, F.; Schütze, M.;
The effect of plasma immersion ion implantation of chlorine on the high temperature oxidation of titanium aluminides alloys was investigated. PIII implantations of Cl2 at 30 kV (effective energy 15 keV) show a strong reduction of the oxidation at 900°C in air, which is comparable to conventional beam line im-plantations of Cl at 15 keV. A specialized PI³ system for the strongly etching Cl2 plasma was set up. The chamber is coated inside with aluminum foil, in order to protect the chamber and to avoid contamination of the plasma except with Al. The pumping system is chemically resistant. First implantations and plasma diagnostic of an ICP source sustained Cl2 plasma are discussed. The effect on the high temperature oxidation behavior is tested using thermogravimetrical analysis and microstructural investigations
Keywords: plasmaimmersion ionimplantation oxidation TiAl
  • Lecture (Conference)
    SMMIB 2001, Marburg, Germany 9-14 September 2001

Publ.-Id: 3855 - Permalink


Local void measurements in integral-type experiments simulating nuclear power plant transients
Ezsöl, G.; Szabados, L.; Prasser, H.-M.;
The Paks Nuclear Power Plant is equipped with VVER-440/V213-type pressurised water reactors. As known, these reactors have a number of special features, therefore the transient behaviour should be different from PWRs of usual design.
To study the transient behaviour of this type of NPPs an integral-type facility called PMK-2, a scaled-down model of the Paks NPP was designed and constructed in the middle of 1980s and several experiments of different types have been performed.
In the framework of a European Union financed Phare project an upgrading of PMK-2 was performed. Equipments installed are as follows: needle-shaped void-probes for local void measurements, full-flow turbines for velocity measurements, micro-turbines for two-phase flow measurements, three beam gamma densitometer to measure coolant density and to identify flow patterns, and in addition a new data acquisition system has been installed.
This paper deals with the application of void probes for the evaluation of the results of a loss of coolant accident.

Keywords: Nuclear reactor safety, thermal hydraulics, integral test facilities, small break loca, void fraction measurement
  • Lecture (Conference)
    5th World Conference on Experimental Heat Transfer, Fluid Mechanics and Thermodynamics, Thessalonoki, Greece, 24-28 September 2001, Vol. 2, pp. 1637 - 1641.
  • Contribution to proceedings
    5th World Conference on Experimental Heat Transfer, Fluid Mechanics and Thermodynamics, Thessalonoki, Greece, 24-28 September 2001, Vol. 2, pp. 1637 - 1641.

Publ.-Id: 3854 - Permalink


Prevention of Water Hammer in Pipelines in Case of Emergency Shut-Off by Fast Acting Valves
Prasser, H.-M.; Dudlik, A.; Schönfeld, S. B. H.; Fahlenkamp, H.; Schlüter, S.;
The paper presents a method to prevent the water hammer by an adaptive control of the valve closing process. For this purpose, the valve is equipped with a brake system that acts onto the rotation axis of the valve flap. The brake cylinder of the applied hydraulic disk brake is connected to the pipeline just upstream the valve, so that the fluid pressure may activate the brake. By this means the closing is interrupted when the pressure of the fluid increases due to the water hammer. The pressure peak is limited to a maximum pressure given by the user.
The described system does not need any external energy source. Furthermore, it adapts to changes of the pipe system parameters, such as varying pipeline length (e.g. liquid supplied from tanks with a different distance from the valve), fluid velocity or physical properties of the fluid. These are major advantages compared to traditional damping systems, which delay valve closing in a fixed manner.

Keywords: Plant safety, pipelines, water hammer, passive safety systems
  • Poster
    ECCE-3, 3rd European Congress on Chemical Engineering, Nürnberg, 26.-28. Juni 2001, Proc. on CD-ROM, Poster P2 - 60.
  • Contribution to proceedings
    ECCE-3, 3rd European Congress on Chemical Engineering, Nürnberg, 26.-28. Juni 2001, Proc. on CD-ROM, Poster P2 - 60.

Publ.-Id: 3853 - Permalink


Fast Wire-Mesh Sensor for Two-Phase Flow Visualisation with 10 000 Frames per Second
Prasser, H.-M.; Zschau, J.; Peters, D.; Pietzsch, G.; Taubert, W.; Trepte, M.;
The paper presents a new wire-mesh sensor for the fast visualisation of gas-liquid flows with a rate of 10 000 frames per second based on the measurement of the local instantaneous conductivity of the two-phase mixture. With this resolution it is now possible to visualise and quantify individual bubbles at mixture velocities of about 10 m/s. The sensor consists of two electrode grids with 16 electrodes each, placed at a small axial distance behind each other. The conductivity is measured at the crossing points of the wires of the two grids. The high measuring rate was achieved by applying an integrated digital signal processor for the control of the signal acquisition process. For the link to the data acquisition PC an ETHERNET interface is used. The internal memory is sufficient to store 170,000 frames, i.e. a continuous measurement over 17 s is possible. In the paper, results obtained in a vertical two-phase air-water flow are presented.
Keywords: Gas-liquid flow, void fraction measurement, wire-mesh sensor, bubble flow, annular flow
  • Poster
    ECCE-3, 3rd European Congress on Chemical Engineering, Nürnberg, 26.-28. Juni 2001, Proc. on CD-ROM, poster P16 - 1.
  • Contribution to proceedings
    ECCE-3, 3rd European Congress on Chemical Engineering, Nürnberg, 26.-28. Juni 2001, Proc. on CD-ROM, poster P16 - 1.

Publ.-Id: 3852 - Permalink


A comparison of void-fraction measurements during flashing-induced instabilities obtained with a wire-mesh sensor and a gamma-transmission set-up
Manera, A.; Prasser, H.-M.; van der Hagen, T. H. J. J.; Mudde, R. F.; de Kruijf, W. J. M.;
The void fraction produced in an adiabatic section (riser) during flashing-induced instabilities in a natural-circulation steam/water loop is measured by means of a wire-mesh sensor and two gamma-transmission set-ups located just above and below the wire-mesh sensor respectively. In this paper a comparison between the two different measuring techniques is given. The wire-mesh sensor is capable of measuring the time-dependent two-dimensional void-fraction distribution on a grid of 16x16 points equally distributed over a cross section of the riser, while the gamma-transmission set-ups measure the chordal void fraction along a collimated beam through the riser at a certain height.
The high sampling rate of the wire-mesh sensor (up to 1200 Hz) allows to detect both the frequencies characteristic of the flashing process (between 2 and 4 Hz) and the frequencies characteristic of the flashing-induced flow oscillation (below 0.05 Hz). The former frequencies are less visible in the spectrum of the gamma-transmission signal due to the lower signal-to-noise ratio.
The effect of the wire-mesh sensor on the triggering of void production due to the provision of extra nucleation sites is also studied; no significant differences are observed in the main parameters of the instability if the wire-mesh sensor is removed from the experimental loop.

Keywords: boiling water reactor stability, two-phase flow, wire-mesh sensors, gamma densitometers, void fraction measurement
  • Lecture (Conference)
    4th International Conference on Multiphase Flow, New Orleans, Lousiana, USA - May 27 to June 1, 2001. Proc. CD-ROM, paper 436.
  • Contribution to proceedings
    4th International Conference on Multiphase Flow, New Orleans, Lousiana, USA - May 27 to June 1, 2001. Proc. CD-ROM, paper 436.

Publ.-Id: 3851 - Permalink


Stress relaxation and phase stability of cubic boron nitride films during annealing and ion implantation
Fitz, C.; Fukarek, W.; Möller, W.;
The high intrinsic stresses in cBN films after deposition are reduced significantly employing thermal treatment and ion implantation. In-situ stress measurement and ex-situ polarized infrared reflection spectroscopy are utilized to study stress relaxation and the phase stability. Argon ion implantation into cBN films at room temperature and at 340°C reveals that the critical fluence for amorphization increases with increasing temperature. The fraction of cBN transformed into sp2 bonded BN by Ar ion implantation decreases with increasing substrate temperature for the same amount of stress release.
Keywords: cubic boron nitride, intrinsic stress, annealing, ion implantation, infrared spectroscopy
  • Thin Solid Films 408 (2002) 155

Publ.-Id: 3850 - Permalink


Metallic impurity gettering to defects remaining in the Rp/2 region of MeV-ion-implanted and annealed silicon
Peeva, A.; Koegler, R.; Brauer, G.; Werner, P.; Skorupa, W.;
Damage has been observed in MeV-ion-implanted Si away from the maximum of the nuclear energy deposition profile, mainly around the half of the projected ion range, Rp/2, after annealing at temperatures between 700°C ad 1000°C. This damage is primarily created by the implanted ions and consists of intrinsic defects remaining so small that they have not been observed by techniques sensitive to the lattice structure (RBS/C, TEM). The only way to detect this damage is to decorate it with metals and to measure the metal distribution. In this study the formation and disappearance of the Rp/2 damage has been investigated by Cu gettering in Si +-ion implanted Si versus temperature and time of the annealing cycle. The defects undergo a defect evolution during annealing which results in a decrease of the width of the damage layer with increasing temperature and prolonged time of the annealing. It is mostly believed that an excess of vacancies around Rp/2 getter metal impurities. Nevertheless, by means of positron annihilation spectroscopy no vacancy defects have been observed. In contrast in our XTEM investigation we found small (20-30nm) interstitial loops in the Rp/2 region. The creation of these loops is triggered by injected interstitials resulting from the ion milling procedure used during TEM specimen preparation. The ion bombardment of Si give rise to self-interstitials that diffuse extensively at room temperature and may modify the existing interstitial clusters to bigger agglomerates which can be observed by XTEM.
Keywords: ion implantation, gettering
  • Materials Science in Semiconductor Processing 3 (2000) 297-301

Publ.-Id: 3848 - Permalink


Transition strengths in magnetic dipole bands in 82Rb, 83Rb and 84Rb
Schwengner, R.; Rainovski, G.; Schnare, H.; Wagner, A.; Dönau, F.; Hausmann, M.; Iordanov, O.; Jungclaus, A.; Lieb, K. P.; Napoli, D. R.; de Angelis, G.; Axiotis, M.; Marginean, N.; Brandolini, F.; Alvarez, C. R.; Keywords: Nuclear structure, in-beam gamma spectroscopy, magnetic rotation, tilted-axis cranking model.
  • Contribution to proceedings
    Proceedings der Konferenz NP2001, 5.3. - 8.3.2001, Göttingen, Deutschland

Publ.-Id: 3847 - Permalink


Structural relation between Si and SiC formed by carbon ion implantation
Eichhorn, F.; Schell, N.; Mücklich, A.; Metzger, H.; Matz, W.; Kögler, R.;
The formation of crystalline SiC by implantation of C ions into silicon is not a single-step process. The implantation results in an elastic distortion of the Si matrix lattice and in a formation of crystalline SiC particles depending on ion fluence and thermal conditions at implantation and post-annealing.
The growth of the SiC particles in the Si matrix was studied with different x-ray scattering techniques and high-resolution transmission electron microscopy. Crystallites of the 3C-SiC polytype are formed in a buried layer. Three groups of crystallites with different orientation relation to the Si matrix are found: with a random orientation like a powder material, with a fibre texture axis parallel to the surface normal, and completely aligned to the Si matrix lattice due to a partially coherent growth of SiC in the Si matrix. The thermal treatment favours the growth of highly oriented material: a higher implantation temperature is more efficient than a post-implantation treatment even at higher temperatures.

Keywords: SiC, Si, ion beam synthesis, x-ray diffraction, texture study, reciprocal space map
  • Journal of Applied Physics 91 (2002) 1287 - 1292

Publ.-Id: 3846 - Permalink


18F-Labeled Neurotensin(8-13) Analogues for Tumour Imaging in vivo
Bergmann, R.; Heichert, C.; Wittrisch, H.; Kretzschmar, M.; Rodig, H.; Scheunemann, M.; Tourwé, D.; Iterbeke, K.; Chavatte, K.; Zips, D.; Reubi, J. C.; Johannsen, B.;
4-([18F]fluoro)benzoyl-neurotensin(8-13) (18FB-Arg8-Arg9-Pro10-Tyr11- Ile12-Leu13-OH, 1) and three analogues stabilized in one, two and three positions (18FB-Arg8Psi(CH2NH)Arg9-Pro10-Tyr11- Ile12-Leu13-OH, 2, 18FB-Arg8Psi(CH2NH)Arg9-Pro10-Tyr11-Tle12-Leu13-OH, 3, 18FB-Arg8Psi(CH2NH)Arg9-Pro10-DmTyr11-Tle12-Leu13-OH, 4) were synthesized in a radiochemical yield of 25 - 36% and a specific activity of 5 - 15 GBq/mmol. The peptides were evaluated in vitro and in vivo for their potential to image tumours, overexpressing neurotensin receptor 1 (NTR1) by positron emission tomography (PET). The analogues exhibited in vitro binding affinity in the low nanomolar range to NTR1-expressing human tumours, measured by quantitative receptor autoradiography (IC50: 1 0.42±0.05 nM, 2 0.91±0.20 nM, 3 4.1±0.60 nM) , HT-29 (IC50: 24.0±4.2 nM) and WiDr cells and to sections of tumours derived from these cell lines in mice. The radiotracers were internalised in the cells in vitro, and the fluorinated peptides were able to mobilize intracellular Ca2+ of WiDr cells. In in vivo studies in rats and in mice bearing HT-29 cell tumours, only a moderate uptake of the radioligands into the studied tumours was observed, presumingly due to degradation in vivo and fast elimination by the kidneys of rats and by the liver of mice. The pathway of the fast enzymatic degradation of the non-stabilized or not sufficiently stabilized 18F-labeled peptides was elucidated. The main catabolic product is the 18FB-Arg8Psi(CH2NH)Arg9-Pro10. In vivo, in comparison with the other analogues, the specific tumour uptake expressed as tumour-to-muscle relation was highest for the radioligands 3 and 4. The blood clearance of the analogues was reduced by co-injection of peptidase inhibitors.
The 4-[18F]fluorobenzoyl label on the N-terminal arginine, the introduction of one reduced peptide bond and two bulky amino acid residues (Tle, DmTyr), are tolerable for a high in vitro affinity to the neurotensin receptor 1 (NTR1) and the ability to be internalised in receptor-positive tumour cells. Only the double and threefold-stabilized (3, 4) exhibited a remarkable specific tumour uptake which was, however, not sufficient for tumour imaging in the abdomen. Additional efforts are required to improve molecule stabilization against enzymatic attack and to enable receptor-based tumour imaging.
This work was partially supported by the BIOMED grant BMH4-CT98-3198 of the EC.

  • Lecture (Conference)
    5. Deutsches Peptidsymposium, Bielefeld, Deutschland, 11.-14.3.2001

Publ.-Id: 3845 - Permalink


A scissors-like excitation on the quadrupole vibrational state in 88Sr
Käubler, L.; Schnare, H.; Schwengner, R.; Prade, H.; Dönau, F.; Grosse, E.; Schilling, K.-D.; Wagner, A.;
Dipole excitations in the spherical nucleus 88Sr, observed in the energy region 4.5 MeV < E_x < 5.5 MeV,
are proposed to be scissors-like excitations on top of the dynamically deformed quadrupole vibrational state.
  • Contribution to proceedings
    Proceedings of the Int. Symposium on Nuclear Structure Physics, Göttingen, March 5 - 8, 2001: Ed. R. Casten et al.; World Scientific 2001, p. 363

Publ.-Id: 3844 - Permalink


PET imaging for quality assurance of heavy ion therapy and potential extension to proton therapy.
Parodi, K.; Enghardt, W.; Hinz, R.; Lauckner, K.; Pawelke, J.; Pönisch, F.; Crespo, P.; Kausch, C.;
no abstract
  • Lecture (Conference)
    International Conference: Imaging Technologies in Biomedical Sciences (ITBS) "Detectors for PET, SPECT, Radiology and for in vitro Imaging", 20-24 May, 2001, Milos Island, Greece
    Book of Abstract (2001) 40-42
  • Contribution to proceedings
    International Conference: Imaging Technologies in Biomedical Sciences (ITBS) "Detectors for PET, SPECT, Radiology and for in vitro Imaging", 20-24 May, 2001, Milos Island, Greece
    Book of Abstract (2001) 40-42

Publ.-Id: 3843 - Permalink


Strukturaufklärung im Submikromolbereich : TRLFS-Untersuchungen zur Cm(III) Sorption an und zum Einbau in Calcit
Stumpf, T.; Fanghänel, T.;
Die Wechselwirkung von Cm(III) (9E-8 mol/L) mit einer Calcit Suspension (1 g/L) wurde mit Hilfe der zeitaufgelösten Laserfluoreszenzspektroskopie untersucht. Dabei konnte ein Cm(III)/Calcit Oberflächenkomplex nachgewiesen und charakterisiert werden. Das Maximum der Fluoreszenzemission dieser Curium Spezies liegt bei 607.5 nm und entspricht damit dem des Tetracarbonatokomplexes Cm(CO3)45- in Lösung. Während das freie Cm-Aquoion von 9 Wassermolekülen umgeben ist, läßt die für den Oberflächenkomplex ermittelte Fluoreszenzlebensdauer von 314 ± 6 ms auf ein Wassermolekül in der ersten Koordinationssphäre des Curiums schließen. Mit zunehmender Cm(III)/Calcit Kontaktzeit nimmt die Stärke des Signals mit einem Emissionsmaximum bei 607.5 nm sukzessive ab und ein sehr weit rot verschobenes Signal wird sichtbar. Die gemessene extreme Verschiebung zu einem Wert von 619 nm ist bisher einmalig und deutet auf eine starke Veränderung des Cm-Ligandenfeldes hin. Für diese Spezies wurde eine Fluoreszenzlebensdauer von 1302 ± 75 ms gemessen. Das entspricht dem theoretisch bestimmten Wert für wasserfreies Curium. Die ermittelte Fluoreszenzlebensdauer und die starke Verschiebung des Cm-Spektrums mit der Dauer der Kontaktzeit ist der spektroskopische Beweis für den Einbau des Curiums in das Calcitgitter.

Lecture (Conference): GDCh Jahrestagung der Fachgruppe Nuklearchemie 2001 in Würzburg, Sept. 2001 (submitted)
  • Lecture (Conference)
    GDCh Jahrestagung der Fachgruppe Nuklearchemie, 24.-26.09.2001, Würzburg, Deutschland

Publ.-Id: 3842 - Permalink


Uran (VI) - Komplexierungen mit Modellverbindungen aus der Pflanzenchemie
Günther, A.; Geipel, G.; Koban, A.; Bernhard, G.;
Radionuklidkontaminationen können über den Belastungspfad Boden-Pflanze-Nahrungskette deutlich zur Strahlenbelastung des Menschen beitragen. Für zuverlässige Abschätzungen der Radionuklidmigrationen in das geologische und biologische Umfeld ist ausgehend von der Verteilung der Nuklide die chemische Charakterisierung der Radionuklidspezies unbedingt erforderlich, um den summarischen Transferfaktor durch chemisch eindeutig identifizierte Parameter zu ersetzen. In verschiedenen Versuchsreihen wurde mit der Bestimmung der chemischen Speziation von U(VI) in Pflanzen begonnen. Durch Untersuchungen mittels zeitaufgelöster Laser-induzierten Fluoreszenzspektroskopie und Röntgenabsorptionsspektroskopie wurde deutlich, daß Uran in der Oxidationsstufe +6 in der Pflanze vorliegt und es Unterschiede zwischen der Angebotsspeziation im Porenwasser des Bodens bzw. in der Hydrokulturlösung und der Akkumulationsspeziation in der Pflanze gibt. Es zeigte sich, daß der chemische Zustand des Urans im Gleichgewicht in der Wurzel, Sproßachse und im Blatt identisch und unabhängig von der Art der Pflanze, den Wachstumsbedingungen und der Angebotsspeziation ist. Die bisherigen spektroskopischen Resultate deuten auf die Bildung von Uranyl-Phophato-Komplexe als Hauptspezies hin. Neben der Phosphatanbindung müssen aber auch carboxylische Bindungen zum Uran in den Pflanzenproben in Betracht gezogen werden.[1]
Ausgehend von diesen Ergebnissen, wurden Modellkomplexierungen von U(VI) mit ausgewählten organischen Liganden durchgeführt, die im Aufbau und Stoffwechsel der Pflanzen eine große Rolle spielen. In Anlehnung an das Verhalten von Schwermetallen im pflanzlichen System wurden Vertreter aus den Substanzklassen Carbonsäuren, Aminosäuren und Peptide, Kohlenhydrate, Lipoide und aus der Gruppe der freien und polymergebundenen Nukleobasen für die Modellkomplexierungen ausgewählt. Für die Untersuchungen des Reaktionsverhaltens von U(VI) gegenüber den ausgewählten Bioliganden werden neben der UV-Vis Spektroskopie insbesondere die zeitaufgelöste Laser-induzierte Fluoreszenzspektroskopie genutzt. Erste Ergebnisse werden hier vorgestellt. Ziel ist es, die erhaltenen spektroskopischen Datensätze mit Daten von kontaminierten Pflanzenproben zu vergleichen, um auf diese Weise U(VI)-Spezies in Pflanzen eindeutig zu charakterisieren.

[1] A. Günther, Zwischenbericht DFG-BE 2234/1-1
  • Lecture (Conference)
    GDCh Jahrestagung Chemie, 23.-29.09.2001, Würzburg, Deutschland

Publ.-Id: 3841 - Permalink


Die Anlagerung von radiotoxischen Schwermetallen an Kolloidpartikel im Flutungswasser einer stillgelegten Urangrube
Zänker, H.; Richter, W.; Schreyer, J.; Jenk, U.;
Das Uranbergwerk Königstein (Sachsen) befindet sich zur Zeit in der Flutungsphase. Es wurde Flutungswasser kolloidchemisch untersucht (pH 5,6; Eh 450 mV; CCa 0,9 mM, CFe 0,3 mM, CU 0,05 mM, CSulfat 1,2 mM, CHydrogenkarbonat 1,0 mM). Nahezu 90% des Fe waren zweiwertig. Auf Grund des Eh-Wertes erwarten wir, daß das Uran sechswertig vorlag. Die Kolloidkonzentration betrug 2 bis 3 mg/l, die Partikelgröße war 100 bis 300 nm. Die Partikel bestanden vor allem aus Fe, Al, S und U.
Grubenwässer können kolloidchemisch zwischen zwei Extreme eingeordnet werden:
(a) Hochmineralisierte Porenwässer mit pH-Werten von 1 bis 3, die ultrafeine Fe(III)-
Partikel im g/l-Bereich enthalten (Partikelgröße <5 nm) und
(b) "Bulk"-Wässer mit pH-Werten um 7, die Fe(III)/Al-Submicronpartikel im Konzen-
trationsbereich von wenigen mg/l enthalten (Partikelgröße 100 bis 300 nm) [1].
Die pH-Abhängigkeit der Schwermetallsorption an Oxyhydroxysulfaten und Oxyhy-droxiden des Fe(III) und Al kann durch sigmoide Kurven mit einem steilen Anstieg bei mittleren pH-Werten ("Adsorption Edge") beschrieben werden. Bei Wässern des Typs (a) findet kaum Adsorption statt (Ausnahmen: 210Pb, Ra-Isotope). Bei Wässern des Typs (b) werden viele radiotoxische Schwermetalle stark sorbiert und sind somit fil-trierbar (210Po, 230Th, 227Ac, 210 Pb). Bemerkenswert ist das Verhalten von U(VI). In karbonatfreien Lösungen zeigt es an Fe(III)-Partikeln eine starke Adsorption bei pH-Werten >4 [2]. In realen "Bulk"-Wässern aus Bergwerken wird die U-Adsorption durch die Bildung von Uranylkarbonatokomplexen jedoch deutlich unterdrückt [1].
Flutungswässer repräsentieren den Übergang von Wässern des Typs (a) in Wässer des Typs (b). In unseren Proben waren stark adsorbierende Nuklide wie 210Po und 210Pb zum größten Teil an Kolloidpartikel gebundenen (filtrierbar). In-teressanterweise erwiesen sich aber auch 60 bis 90% des Urans als kolloidgetragen. Offensichtlich wird bei dem vorliegenden pH-Wert von 5,6 die Uranadsorption weder durch hohe Azidität noch durch Karbonatkomplexierung verhindert.
Der Zutritt von Sauerstoff löst eine Vielfalt von chemischen Reaktionen in den Proben aus. Durch die Oxidation des Fe2+ steigt der Gehalt an Fe(III)-Partikeln (Faktor 10). Trotz der höheren Trägerkolloidkonzentration sinkt der filtrierbare Uranylanteil zunächst. Grund ist der pH-Abfall (bis auf etwa 4,5), den die Fe-Oxidation verursacht. Mit einiger Verzögerung steigt der pH-Wert wieder weil die Ge-samtkarbonatkonzentration durch CO2-Entgasung sinkt; der Hydrogenkarbonatgehalt fällt bis auf <0,05 mMol/l. Beides bewirkt einen Anstieg des filtrierbaren Urananteils auf fast 100%. Alle diese Vorgänge (O2-Zutritt, pH-Variationen, CO2-Entgasung) spielen auch im Bergwerk eine Rolle.
Die oft getroffene Annahme einer ungehinderten Migration von Uranyl in gelö-ster Form ist für pH-Werte von 4 bis 6 "überkonservativ". Scavenging durch Fe(III)-Partikel und Kolloidkoagulation plus Sedimentation kann in diesem pH-Bereich das U(VI) in erheblichem Maße immobilisieren.

[1] Zänker, H. et al.; Radiochim. Acta 88, 619 (2000)
[2] Hsi, C.D. and Langmuir, D.; Geochim. Cosmochim. Acta 49, 1931 (1985)
  • Lecture (Conference)
    GDCh Jahrestagung Chemie Würzburg, Deutschland, 23.-29.09.2001

Publ.-Id: 3840 - Permalink


Energy-dependent anisotropic deformation of colloidal silica particles under MeV Au irradiation
van Dillen, T.; Polman, A.; Fukarek, W.; van Blaaderen, A.;
Spherical silica colloids with a diameter of 1.0 µm, made by wet chemical synthesis, were irradiated with 2–16 MeV Au ions at fluences in the range (2–11)×1014 cm–2. The irradiation induces an anisotropic plastic deformation turning the spherical colloids into ellipsoidal oblates. After 16 MeV Au irradiation to a fluence of 11×1014 cm–2, a size aspect ratio of 5.0 was achieved. The size polydispersity (~3%) remains unaffected by the irradiation. The transverse diameter increases exponentially with ion fluence. By performing measurements as a function of ion energy at a fixed fluence, it is concluded that the transverse diameter increases linearly with the average electronic energy loss above a threshold value of ~0.6 keV/nm. Nonellipsoidal colloids are observed in the case where the projected ion range is smaller than the colloid diameter. The data provide strong support for the thermal spike model of anisotropic deformation.
  • Applied Physics Letters 7 (2001) 910-912

Publ.-Id: 3839 - Permalink


Atomistische Computersimulation der Defektbildung und -evolution in Si bei Ionenimplantation
Posselt, M.;
For further informations, please contact the author (M.Posselt@fz-rossendorf.de).
  • Lecture (Conference)
    39. Arbeitskreis Punktdefekte, Dresden, February 12 - 13, 2001

Publ.-Id: 3838 - Permalink


Understanding of ta-C Film Deposition by Means of Atomistic Simulations
Jäger, H.-U.;
Ion beam deposition of carbon films was studied by molecular-dynamics simulations. Using a slightly modified version1 of the analytical hydrocarbon potential of Brenner, deposition of films with a thickness of up to 10 nm was computed for ion energies E = 10-80 eV, and for substrate temperatures ranging from 100 to 900 K.
The following properties of the calculated films were analysed: (i) sp3 content versus mass density in inner film regions, (ii) binding energies of 3- and 4-fold coordinated carbon atoms in films of different mass densities, (iii) probability distributions for the number of sp3 atoms generated (or annihilated) per deposited ion, and (iv) structure and width of the graphite-like surface regions. As a result, an atomistic picture is provided which shows how the formation of tetrahedral amorphous carbon (ta-C) films is affected by both ion energy and substrate temperature.

1 H.U. Jäger and K. Albe, J. Appl. Phys. 88, 1129 (2000).
  • Poster
    International Conference on Materials for Advanced Technologies (ICMAT 2001), Symp. F: Diamond, Diamond-like Carbon & Related Materials, 1 - 6 July 2001, Singapore

Publ.-Id: 3837 - Permalink


Schnelles Freimeßverfahren auf alpha-aktive Nuklide
Nebelung, C.; Henniger, J.;
Bei der Freimessung von Bauschutt aus dem Abriß von Nuklearanlagen ist eine direkte Messung der alpha-aktiven Nuklide im stehenden Gebäude auf Grund ihrer geringen Reichweite und ihrer Absorption im Beton nicht möglich. Die im Rahmen von BMBF-Projekten entwickelte Methode der direkten Alpha-Spektrometrie von großflächigen dünnen Meßpräparaten nach nur mechanischer Präparation des Betons ermöglicht eine Bestimmung der Actinide bis zu 0,02Bq/g in Multielementspektren [1,2]. Durch die große Fläche wird eine hohe Impulsrate und durch die dünne Schicht eine geringe Selbstabsorption der Alpha-Strahlung und damit eine gute Auflösung der Spektren erreicht. In einem aus zwei Schritten bestehendem Zerkleinerungsprozeß wurden mittlere Partikeldurchmesser von 0,5µm erreicht. Die Grobzerkleinerung erfolgt mit einem Backenbrecher (reiner Beton) oder mit einer Tischfragmentierungsanlage (Trennung von Beton und Armierungseisen), die Feinzerkleinerung durch Naßmahlen mit Spezialmahlkugeln. Die Meßproben mit einem Durchmesser von 20cm und Schichtdicken zwischen 0,6 und 5µm entstanden durch Sprühen mit einer Zweistoffdüse aus der Betonsuspension auf Probenträger und anschließendes Trocknen. Die Suspensionsstabilität konnte durch verschiedene Peptisatoren erhöht werden. Die Alpha-Spektren der Meßproben wurden in einer Gitterionisationskammer aufgenommen. Durch die Verwendung von Standardbeton mit zugefügten Actiniden konnten die Selbstabsorption der Alpha-Strahlung und die Peakform in Abhängigkeit der Probendicke ermittelt werden. Somit konnten die Spektren unbekannter Betonproben gleicher Geometrie entfaltet werden. Das für diese Arbeit entwickelte Programm WINKRUM basiert auf einem geometrischen Modell für Partikelgröße, Partikelverteilung und Packungsdichte. Mit Strahlungstransportberechnungen [3] können Spektren simuliert werden, die ebenfalls eine Peakentfaltung von Mul-tielementspektren ermöglichen.

Das diesem Bericht zugrundeliegende Vorhaben wurde mit Mitteln des Bundesministeriums für Bildung und Forschung unter dem Förderkennzeichen 02 S 7768 gefördert. Die Verantwortung für den Inhalt liegt bei den Autoren.

Literatur
[1] Nebelung, C.; Nitsche, H., Henniger, J.
"Stillegung und Rückbau: Direktmessung alpha-aktiver Nuklide in Bauschutt zur Freigabe-entscheidung Schlußbericht" BMBF 02S 7655 /02S7655A, 1999
[2] Nebelung, C.; Henniger, J.
Schlußbericht zum Fördervorhaben BMBF 02 S 7768 in Vorbereitung
[3] Henniger, J.
"AMOS - ein multivalent nutzbares Programmsystem zur Berechnung von Strahlungstrans-portproblemen", Strahlenschutz : Physik und Messtechnik, Band 1, 26. Jahrestagung des Fachverbandes für Strahlenschutz e.V., Karlsruhe, 24.-26. Mai 1994; Verlag TÜV Rhein-land.

Keywords: Freimessung, Bauschutt, Alpha-Spektrometrie
  • Poster
    GDCH- Tagung Würzburg, 23.9.-29.9.2001

Publ.-Id: 3834 - Permalink


Simulation of Scaled Core-Meltdown-Experiments and Investigation of a Possible Vessel Support against Failure
Willschütz, H.-G.; Altstadt, E.; Weiss, F.-P.; Sehgal, B. R.;
At present the scaled core melt down experiments FOREVER are underway. These experiments are simulating the lower head of a reactor pressure vessel under the load of a melt pool with internal heat sources. Due to the multiaxial creep deformation of the three-dimensional vessel with a highly non-uniform temperature field these experiments are an excellent possibility to validate numerical creep models. A Finite Element model is developed and using the Computational Fluid Dynamic module the temperature field within the vessel wall is evaluated. The transient structural mechanical calculations are then performed applying a new creep model procedure. Additionally the material damage is evaluated considering the creep deformation as well as the prompt plasticity.
After post-test calculations for the FOREVER-C2 experiment, pre-test calculations for the experiments to come are performed. Taking into account both - experimental and numerical results - gives a good opportunity to improve the simulation and understanding of real accident scenarios. Analysing the calculations it seems to be advantageous to introduce a vessel support which can disburden the vessel from a part of the mechanical load and therefore avoid the vessel failure or at least prolongate the failure time as a possible accident mitigation strategy. Additionally, it seems to be possible to install an absolutely passive automatic control device to initiate the flooding of the reactor pit to ensure external vessel cooling in case of a core melt down.
Keywords: FOREVER-Experiment, Coupling of Thermo-Fluid Dynamic and Structural Mechanical FE-Model, Advanced Creep Modelling, Vessel Support as Accident Mitigation Strategy
  • Lecture (Conference)
    16th International Conference on Structural Mechanics in Reactor Technology SMiRT16, Washington, DC, USA, August 12-17, 2001, Paper No. 1145
  • Contribution to proceedings
    16th International Conference on Structural Mechanics in Reactor Technology SMiRT16, Washington, DC, USA, August 12-17, 2001, Paper No. 1145

Publ.-Id: 3832 - Permalink


Effect of temperature on the emission characteristics of liquid metal alloy ion sources
Bischoff, L.; Teichert, J.; Ganetsos, T.; Mair, G. L. R.;
In spite of the fact that a great deal of research has been carried out on liquid metal ion sources, suprisingly few results exist on the temperature dependence of their emission characteristics. In this article we study two liquid metal alloy ion sources (LMAISs), namely Co36Nd64 and Au77Ge14Si9. While the results of the former source were as expected, the latter displayed an entirely different dependence of its emission characteristics on temperature. The unusual results of the Au77Ge14Si9 LMAIS are explained in terms of the abnormal behavior of the surface tension of the alloy with temperature.
Keywords: liquid metal alloy ion source, temperature dependence, emission behavior
  • Journal of Vacuum Science and Technology B19 (1) 2001 76 -78

Publ.-Id: 3830 - Permalink


Investigation on multiphase and multicomponent flows - experiments and measurement devices
Schaffrath, A.; Krüssenberg, A.-K.;
Vertical two-phase flow is normally classified into the four basic flow regimes bubble, slug, churn and annular flow. The transition between the different flow regimes does not occur suddenly and many extensions of this classification can be found in literature. For the prediction of flow patterns empirical and theoretical flow pattern maps have been developed.
  • Lecture (others)
    Politecnico di Milano, Dipartimento di Ingegneria Nucleare, 13.03.2000, Milano, Italy

Publ.-Id: 3823 - Permalink


A mineral-specific thermodynamic sorption database
Brendler, V.; Arnold, T.; Bernhard, G.; Fanghänel, T.;
This paper presents a digitized version of a thermodynamic sorption database, implemented as a relational database under MS Access. The data are required for the parametrization of Surface Complexation Models (SCM). It is mineral-specific and can therefore also be used for additive models of more complex solid phases such as rocks or soils. An integrated user interface helps users to access selected mineral and sorption data, to convert parameter units, to extract internally consistent data sets for sorption modeling, and to export them into formats suitable for other modeling software. Data records comprise of mineral properties, specific surface area values, characteristics of surface binding sites and their protolysis, sorption ligand information, and surface complexation reactions. The following submodels are already implemented, extensions to other variants are straightforward: the Non-Electrostatic Model, the Diffuse Double Layer Model, the Constant Capacitance Model, the Triple Layer Model, and the Basic Stern Model. For every SCM type (where applicable), also the concept of strong and weak binding sites, and the 1-pK approach is included. Surface species composed from up to three different ligands can be incorporated.
An extensive bibliography is also included, providing links not only to the above listed data items, but also to background information concerning surface complexation model theories, related software for data processing and modeling, and sorption experiment techniques. Only very few of the abundant surface complexes proposed in the literature (mostly resulting just from best-fit considerations) are actually validated by spectroscopic evidence or supported by theoretical (quantum-chemical) calculations. If such information is available it is also stored in the database.
The database will help to substitute the at present in risk assessment studies most often applied simplistic distribution coefficients (Kd-values) by the more realistic description of sorption phenomena with SCM. It assists the identification of critical data gaps, the evaluation of existing parameter sets, consistency tests and the establishment of selected reference data sets. As to the knowledge of the authors, so far there is no such digital thermodynamic database for surface complexation equilibria existent world-wide, despite the vast amount of available data.



  • Lecture (Conference)
    Migration 2001, Bregenz, Österreich, 16.-21.09.2001

Publ.-Id: 3822 - Permalink


Structure parameter analysis of Cu(UO2Aso4)2 nH2 using EXAFS spectroscopy
Hennig, C.; Reich, T.; Funke, H.; Roßberg, A.; Rutsch, M.; Bernhard, G.;
kein Abstract vorgesehen
  • Poster
    ESRF Meeting, Grenoble, Frankreich, 19.-21.02. 2001

Publ.-Id: 3821 - Permalink


The effect of secondary iron mineral and colloid formation on uranium sorption during the dissolution of chlorite
Krawczyk-Bärsch, E.; Arnold, T.; Hüttig, G.; Zänker, H.; Brandt, F.; Bernhard, G.;
Chlorite is a common accessory mineral, commonly found in sedimentary and low grade metamorphic rocks like the phyllite in the former uranium mining area of Saxony (Germany). The cur-rent flooding of the mines leads to an interaction be-tween the uranium containing flooding water and the surfaces of the wall rock. During the weathering of phyllite a secondary mineral is formed, which in further investigations [1] was described as ferrihydrite. The source of this secondary mineral is the iron-rich chlo-rite of the phyllite.
Chlorite is a phyllosilicate with a trioctahedral structure, consisting of negatively charged 2:1 layers that alternate regularly with positively charged interlayer sheets [2]. During the weathering of chlorite the main constituents of the octahedral sheets, Mg2+, Fe2+, Fe3+ and Al3+, are released into the aqueous solu-tions. In laboratory experiments the dissolution of chlo-rite was studied with a continuous flow-through reactor and in batch experiments. In this study we will lay em-phasis on the released iron because of its ability to form secondary minerals and colloids.
Experiments: Batch experiments were carried out on an iron-rich chlorite from Flagstaff Hill, California, with a grain size of 63-200 µm. Half a gram of the samples were added to 40 ml deionized water, which was previously adjusted to an ionic strength of 0.1 M with NaClO4. The suspension was aged during 2 months without any pH adjustment. A pH value of 7 was found at the end of the experiment. The freshly formed iron hydroxide particles were separated from the large excess of the micron-size chlorite powder particles by well-defined centrifugations (2500 x g, 1h and 3500 x g, 1h). A defined volume of the centrifugate was filtered through a 50 nm and 15 nm Nuclepore filter in order to fix the ultrafine iron particles on a substrate. The filter membranes were prepared for scanning electron microscopy (SEM).
Results: In SEM investigations spherical particles are detected on the Nuclepore filter. The size of these colloids ranges from 30 to 80 nm. The colloids are mainly arranged as agglomerates, while individual colloids are rarely observed. On several large agglom-erates energy-dispersive X-ray analysis (EDS) were taken in order to get information about the chemistry of these colloids. With this method we were able to detect directly iron colloids of a chlorite suspension at pH 7. The process leading to the formation of colloids can be explained as a consequence of the iron release during the dissolution of chlorite. The dissolved iron oxidizes to ferric iron which subsequently hydrolyses, precipi-tates and forms secondary minerals and iron colloids. The detection of iron colloids was previously described in a suspension of ground phyllite [3], where a com-bined technique of centrifugation at varying centrifugal speed and ICP-MS and AAS of the centrifugates was used. The formation of iron colloids was prevented in the acid region of pH = 4 due to the higher solubility of Fe in this pH region. With decreasing solubility in the neutral and alkaline medium, the released Fe forms iron colloids or precipitates as secondary iron mineral coatings. The formation of iron colloids during the dissolu-tion of chlorite must be taken into consideration in the assessment of contaminant behavior in the nature. Though contributing only little to the mass balance of a water body, iron colloids can show significant adsorp-tion of trace elements because of their high specific surface area and their affinity to heavy metals.
The formation of secondary iron mineral coatings is also of importance for the behavior of contaminants in the nature since coatings significantly change the sur-face properties of the weathering chlorite. The most common secondary iron mineral is ferrihydrite, a poorly crystallized iron mineral with a chemical for-mula of 5Fe2O3 . 9H2O [4] and a large specific surface area. Sorption experiments which were carried out with ur...
  • Lecture (Conference)
    Goldschmidt Conference, Hot Springs, Virginia, USA , 19.5. - 24.5.2001

Publ.-Id: 3820 - Permalink


Complexation of Cm(III) and Eu(III) by glycolic acid: TRLFS studies
Stumpf, T.; Fanghänel, T.; Grenthe, I.; Kim, J. I.;
Complexation processes of Cm(III) and Eu(III) by glycolic acid are studied by time-resolved laser fluorescence spectroscopy (TRLFS). The experiments with curium are performed in 0.1 M and 3.0 M NaClO4. The glycolic acid concentration is varied between 0.01 mol/L and 0.5 mol/L at pH 3. Cm(III) and Eu(III) fluorescence emission spectra are obtained at a fixed glycolic acid concentration of 0.5 mol/L, the pH is varied between 3 and 11. In addition to the Cm3+ aquo ion, two Cm(III)-glycolic acid species are observed by peak deconvolution: Cm(gly)2+ and Cm(gly)2+. Above pH 5 a chelate Cm-glycolate complex is formed. This curium-glycolate complex is characterised by its emission spectrum (peak maximum at 611.2 nm) and its fluorescence emission lifetime (172 ± 8 µs). The corresponding chelate europium-glycolate complex with 300 ± 10 µs lifetime is obtained above pH 6.83. In the pH range 6 to 8 the decay behaviour of the excited state is different in the Cm(III)- and Eu(III)-glycolate system. While a bi-exponential decay behaviour was observed for the Cm-system, indicating slow exchange kinetics in comparison to the fluorescence decay of the exited state, the corresponding Eu-system shows mono-exponential decay behaviour. More over the reversibility of Eu-chelating is much faster than in the case of the Cm(III) complex. The results show that the strength and kinetics of the chelating is different for Cm(III) and Eu(III).

  • Lecture (Conference)
    Actinides-2001, Hayama, Japan vom 4. - 9. November 2001.

Publ.-Id: 3818 - Permalink


The NOKO/TOPFLOW Facility for Natural Convection Flow
Hicken, E.-F.; Jaegers, H.; Schaffrath, A.; Weiß, F.-P.;
For the study of the effectiveness of passive safety systems a high pressure (up to 7 MPa) and high power (up to 4 MW) test facility – named NOKO – has been constructed and operated at the Forschungszentrum Jülich. From 1996-1998 this facility was used for a project within the 4th FP of the EU "European BWR R&D Cluster for Innovative Passive Safety Systems". An overview and selected results are given for the tests with two bundles of the emergency condenser, with the building and plate condenser, with 4 different passive initiators, with a passive flooding system and with decay heat removal tests during shutdown.
It has been decided to decrease substantially the safety research at the Forschungszentrum Jülich; to maintain the experimental competence for two-phase flow the NOKO facility will be transferred to the Forschungszentrum Rossendorf by the end of the year 2000 up to the beginning of the year 2001. The facility will be named TOPFLOW; the main objectives of future tests will be oriented towards more generic research: investigation of steady state and transient two phase flow phenomena especially transient two phase flow patterns, the development of two-phase flow instrumentation, the generation of a data basis for Computational Fluid Dynamic (CFD)-Code validation and testing of heat exchangers and safety systems. An overview will be given about the modifications and improvements related to the test facility and the planned test.
  • Lecture (Conference)
    Technical Committee Meeting on Natural Circulation Data and Methods for Innovative Nuclear Power Plant Design, Session 3, International Atomic Energy Agency, Vienna (Austria), July 18-21, 2000
  • Contribution to proceedings
    Technical Committee Meeting on Natural Circulation Data and Methods for Innovative Nuclear Power Plant Design, Session 3, International Atomic Energy Agency, Vienna (Austria), July 18-21, 2000

Publ.-Id: 3807 - Permalink


Neutron Flux Uncertainty and Covariances for Spectrum Adjustment and Estimations of Pressure Vessel Fluences
Böhmer, B.; Manturov, G.;
Results of estimations of covariance matrices of neutron spectra in VVER-1000 reactor pressure vessel and cavity positions are presented. Two-dimensional calculations with the discrete ordinates transport code DORT in r-theta and r-z-geometries are used to determine the neutron group spectrum covariances including cross-correlations between interesting positions. The new Russian ABBN-93 data set and the CONSYST code are used to supply the transport calculations with neutron group data. All possible sources of uncertainties, as neutron cross sections, fission sources, geometrical dimensions and material densities, were considered, whereas, the uncertainty of the calculation method was assumed to be negligible in view of the available precision of Monte Carlo simulation.
Keywords: fluence covariance, spectrum adjustment, uncertainty analysis, cross-correlation, reactor pressure vessel, reactor dosimetry
  • Lecture (Conference)
    Tenth Symposium of AER on Reactor Physics and Reactor Safety 2000, Moscow (Russia) 18 - 22 September 2000, Proceedings, Vol. I, pp. 345-351
  • Contribution to proceedings
    Tenth Symposium of AER on Reactor Physics and Reactor Safety 2000, Moscow (Russia) 18 - 22 September 2000, Proceedings, Vol. I, pp. 345-351

Publ.-Id: 3802 - Permalink


Technical description of the radiological safety system for X-ray absorption spectroscopy experiments on radioactive samples at the Rossendorf Beamline
Funke, H.; Bernhard, G.; Reich, T.; Matz, W.; Oehme, W.; Claußner, J.; Jansen, K.-H.; Röllig, D.; Nitsche, H.;
The Rossendorf Beamline at the European Synchrotron Radiation Facility is equipped with a unique radiochemistry experimental station. This dedicated station has been designed to perform environmentally relevant experiments on radionuclides, in particular actinides, using synchrotron based X-ray absorption fine structure spectroscopy. The technical concepts and the layout of this experimental station, where radioactive solids and liquids with activities of up to 185 MBq can be studied, are presented. The radiological safety of experimenters, equipment, and of the environment are ensured by the specially developed radiochemistry safety system. The multibarrier concept, the ventilation and air monitoring systems, the radiological protection system, and special software components for recording and visualisation of the safety status are described in detail.

  • Kerntechnik 66(2001) 195-201

Publ.-Id: 3801 - Permalink


Dihydrotetra(4­picoline)siliconchloride­Hexakis­chloroform
Stumpf, T.; Bolte, M.;
The title compound, [C24H30N4Si]2+·2Cl-·6CHCl3, contains a hexacoordinated Si atom located on a crystallographic centre of inversion. The coordination of the Si atom can be described as a slightly distorted octahedron, with the 4-picoline ligands in the equatorial plane and the two H atoms occupying axial positions. The title compound is isomorphous with its analogue where the Cl ions are substituted by Br ions.

Acta Cryst. (2001) E (submitted)
  • Acta Crystallographie

Publ.-Id: 3800 - Permalink


Interaction of Neptunium(V) with Humic Acids of Different Functionalities
Sachs, S.; Schmeide, K.; Geipel, G.; Reich, T.; Heise, K. H.; Bernhard, G.;
In order to improve models used for the predictive modeling of the actinide migration in natu-ral aquifer systems it is necessary to get more precise information about the interaction process between humic acids and actinide ions. This includes for instance a more profound knowledge about humic acid binding sites interacting with actinide ions at different pH values. In addition, natural humic acids contain small amounts of inorganic components, e.g., iron, that cannot be removed by usual purification methods. It is not known whether or not these components may influence the interaction between humic acids and actinide ions.
Applying humic acid model substances and natural humic acids with different functionalities we continue our studies concerning the interaction between humic acids and actinides [e.g., 1,2]. In order to specify humic acid binding sites interacting with actinide ions in the neutral pH range, we study the influence of phenolic OH and other acidic OH groups on the interaction process. We investigate the neptunium(V) complexation in neutral solution by near infra-red absorption spectroscopy and X-ray absorption spectroscopy applying modified synthetic and natural humic acids with blocked phenolic and other blocked acidic OH groups. The influence of inorganic humic acid components on the actinide complexation by humic acids is studied using an "ultra-pure" synthetic humic acid model substance. The neptunium(V) com-plexation of this humic acid is compared to the complexation behavior of natural and synthetic humic acids having small amounts of non-removable inorganic components.

[1] Pompe, S. et al.: Determination and Comparison of Uranyl Complexation Constants with Natural and Model Humic Acids. Radiochim. Acta 82, 89 (1998).
[2] Pompe, S. et al.: Investigation of Humic Acid Complexation Behavior with Uranyl Ions Using Modified Synthetic and Natural Humic Acids. Radiochim. Acta 88, 553 (2000).

Keywords: Humic acid, Synthetic humic acid, Modified humic acid, Phenolic OH groups, Complexation, Neptunium, X-ray absorption spectroscopy, Near infrared absorption spectroscopy
  • Poster
    8th International Conference on Chemistry and Migration Behavior of Actinides and Fission Products in the Geosphere Migration'01,16.-21.September 2001, Bregenz, Austria
  • Lecture (Conference)
    8th International Conference on the Chemistry and Migration Behavior of Actinides and Fission Products in the Geosphere-Migration'01, 16.-21. September, Bregenz, Austria.

Publ.-Id: 3799 - Permalink


Synthesis and preliminary evaluation of N1-methyl-9-[1-hydroxy-3-[18F]fluoro-2-propoxy)methyl]guanine [18F]MFHPG, a new substrate of HSV-1-thymidine kinase
Noll, B.; Noll, S.; Scheunemann, M.; Brust, P.; Friedrich, A.; Hauses, M.; Schackert, H. K.;
no abstract delivered from author
  • Poster
    14th International Symposium on Radiopharmaceutical Chemistry, Interlaken, Switzerland, 10.-15.06.2001

Publ.-Id: 3796 - Permalink


Geschwindigkeitsmessungen im Downcomer der ROCOM Versuchsanlage mittels Laser-Doppler Anemometrie im Vergleich mit numerischen Berechnungen
Höhne, T.; Grunwald, G.; Prasser, H.-M.;
Abstract

An der Vermischungsanlage ROCOM, einem 1:5 skalierten Modell des Druckwasserreaktors Konvoi wurden umfangreiche Geschwindigkeitsmessungen im Downcomer des Reaktordruckbehälters für verschiedene Schleifendurchsätze und Teilschleifenbetrieb durchgeführt. Durch Verwendung eines leistungsfähigen Lasers konnten auch transiente Geschwindigkeitsprofile aufgenommen werden. Einige der gemessenen Profile wurden mit dem numerischen Strömungsberechnungsprogramm CFX-4 nachgerechnet.

Bei Vierschleifenbetrieb konnte eine Unabhängigkeit der Geschwindigkeitsprofile von der Reynoldszahloberhalb über 100 m³/h pro Schleife im Modell nachgewiesen werden. Im Vergleich zu anderen Reaktortypen bestehen im Ringraum des RDB des DWR Konvoi einige konstruktive Besonderheiten, die die Vermischung nachhaltig beeinflussen. Der Downcomer ist verhältnismäßig kurz und besitzt eine diffusorartige Erweiterung unterhalb der Stutzenebene. Unterhalb der Eintrittsstutzen und Austrittsstutzen existieren Rezirkulationsgebiete mit geringen Geschwindigkeitsgradienten. Zwischen den Eintritts- und Austrittsstutzen liegen Gebiete hoher Geschwindigkeitsgradienten. Transiente Messungen bei Anfahren einer Pumpe belegen, daß die Strömung im Downcomer in den ersten Sekunden wie eine Potentialströmung anläuft. Das Geschwindigkeitsmaximum befindet sich dabei noch annähernd unterhalb des entsprechenden Kühlmittelstutzens. Erst mit einer gewissen Zeitverzögerung entwickeln sich die großräumigen Wirbelgebiete, die letztlich zum Geschwindigkeitsmaximum auf der der in Betrieb gegangenen Schleife entgegengesetzten Seite des Ringspalts führen.

Strömungsuntersuchungen im Downcomer mit Hilfe der LDA-Technik bei naturumlaufnahen Schleifendurchsätzen mit Hinzugabe von Glucose zur Simulation von Dichteeffekten sind geplant.
  • Open Access LogoWissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-334 Oktober 2001

Downloads:

Publ.-Id: 3795 - Permalink


S-[18F]fluoromethyl-(+)-McN5652, evaluation in rats as a tracer for the serotonin transporter
Marjamäki, P.; Zessin, J.; Eskola, O.; Bergman, J.; Grönroos, T.; Haaparanta, M.; Lehikoinen, P.; Forsback, S.; Brust, P.; Steinbach, J.; Solin, O.;
The S-[18F]fluoromethyl analogue of (+)-McN5652 was evaluated by autoradiographic ex vivo studies with rats.
Keywords: (+)-McN5652, [18F]fluoromethyl analogue, [18F]bromofluoromethane, PET, autoradiography, serotonin transporter
  • Poster
    12th International Symposium on Radiopharmacology, 12.-15.06.2001, Interlaken, Schweiz

Publ.-Id: 3794 - Permalink


S-[18F]fluoromethyl-(+)-McN5652 - A potential PET tracer for imaging the serotonin transporter
Zessin, J.; Eskola, O.; Brust, P.; Berman, J.; Marjamäki, P.; Kretzschmar, M.; Grönroos, T.; Wittrisch, H.; Haaparanta, M.; Lehikoinen, P.; Solin, O.; Steinbach, J.; Johannsen, B.;
The S-[18F]fluoromethyl analogue of (+)-McN5652 was prepared by reaction of demethylated (+)-McN5652 with [18F]bromofluoromethane in decay-corrected radiochemical yields of about 18% (related to [18F]fluoride). Autoradiographic ex vivo studies with rats and PET studies with piglets indicate that the 18F-labelled analogue of (+)-McN5652 is a potential PET tracer for the imaging of the serotonin transporter.
Keywords: McN5652, [18F]bromofluoromethane, PET, serotonin transporter
  • Lecture (Conference)
    14th International Symposium on Radiopharmaceutical Chemistry, 10 - 15.6.2001, Interlaken, Schweiz

Publ.-Id: 3793 - Permalink


Neptunium(V) Sorption onto Granite and its Mineral Constituents in the Absence and Presence of Humic Acid
Schmeide, K.; Sachs, S.; Reich, T.; Hennig, C.; Heise, K. H.; Bernhard, G.;
In Germany, besides salt formations also granitic subsurface environments are taken into account as potential host formations for the geological disposal of radioactive waste [1]. For safety assessments of radioactive waste repositories, amongst others, the sorption behavior of radionuclides onto the host rock has to be known. It is determined by various factors including pH, Eh, the presence of inorganic and organic ligands as well as the speciation of radionuclides in the aqueous and solid phase.
In the present work, the sorption of neptunium(V) onto granite and its main mineral constituents quartz, orthoclase, biotite, albite, and muscovite is studied under anaerobic conditions as a function of pH, ionic strength and solid/solution ratio in a series of batch equilibrium experiments. Furthermore, the effect of humic acid on the neptunium sorption is studied for different ligand concentrations. A 14C-labelled synthetic humic acid (type M42, [2]) is used for the experiments. Its sorption behavior is comparable to that of natural humic acids. The oxidation state of neptunium in the presence of humic acid and minerals is followed at selected pH values over a period of three months by NIR absorption spectroscopy. The neptunium sorption is affected by both the pH and the presence of organic material.
Neptunium species on the mineral surface are identified using neptunium LIII-edge extended X-ray absorption fine structure (EXAFS) spectroscopy. The structural parameters of the near-neighbor surrounding of sorbed neptunium are compared to those of neptunium hydrate, hydroxide and humate complexes.

[1] Papp, R.: Gegenüberstellung von Endlagerkonzepten in Salz und Hartgestein. FZKA-PTE Nr. 3, Forschungszentrum Karlsruhe GmbH, Karlsruhe 1997.
[2] Bubner, M., et al.: Isotopically Labelled Humic Acids for Heavy Metal Complexation. J. Labelled Compounds and Radiopharmaceuticals XLI, 1017 (1998).
Keywords: Neptunium, humic acid, sorption, granite, muscovite, orthoclase, quartz, albite, biotite, EXAFS
  • Poster
    8th International Conference on Chemistry and Migration Behaviour of Actinides and Fission Products in the Geosphere: Migration '01, Bregenz, Austria, 16.-21.09.2001

Publ.-Id: 3792 - Permalink


Benchmarking of DYN3D/RELAP5 Code Package using the Fifth AER Dynamic Problem for Coupled Codes
Kozmenkov, Y.; Orekhov, Y.; Grundmann, U.; Kliem, S.; Rohde, U.; Seidel, A.;
The paper presents a brief description of the DYN3D/RELAP5 code package developed on the base of coupling the system code RELAP5 and the 3D neutron kinetics code DYN3D. Elaboration of the coupling interface has been performed in the framework of a joint research project.
The fifth dynamic AER problem for VVER-440 reactor plant has been solved using the code package. Calculation results are compared with the results obtained earlier in the FZR using DYN3D/ATHLET. Code-to-code comparison shows a close agreement between the key transient parameters.
  • Lecture (Conference)
    Tenth Symposium of AER on VVER Reactor Physics and Reactor Safety 2000, Moscow (Russia), 18.-22. September 2000, Proceedings pp. 1043-1048
  • Contribution to proceedings
    Tenth Symposium of AER on VVER Reactor Physics and Reactor Safety 2000, Moscow (Russia), 18.-22. September 2000, Proceedings pp. 1043-1048

Publ.-Id: 3791 - Permalink


On usage of coupled neutron-kinetic and thermal-hydraulic computer code DYN3D/ATHLET to study safety of VVER-1000 type reactors under transient and emergency operational modes
Rohde, U.; Kliem, S.; Seidel, A.; Khalimonchuk, V.; Kuchin, A.;
Presently, increased requirements are imposed to study transient and emergency operation modes of nuclear facilities from point of view of quality and adequacy their simulation. In particular, concerning the Ukrainian NPP's this is connected with the analysis of VVER-1000 safety for a whole number of dsign basic accidents.
The first experience was obtained for the use of the coupled code DYN3D/ATHLET caculating a transient connected with the switching-off of one main coolant pump at the unit 6 of the Zaporizhya NPP.
  • Lecture (Conference)
    Tenth Symposium of AER on VVER Reactor Physics and Reactor Safety 2000, Moscow (Russia), 18.-22. September 2000, Proceedings pp. 913-920
  • Contribution to proceedings
    Tenth Symposium of AER on VVER Reactor Physics and Reactor Safety 2000, Moscow (Russia), 18.-22. September 2000, Proceedings pp. 913-920

Publ.-Id: 3790 - Permalink


Spin-density enhancement in a 119Sn implanted (110)Cr single crystal as evidenced by Mössbauer spectroscopy
Dubiel, S. M.; Cielak, J.; Zukrowski, J.; Reuther, H.;
Magnetic properties of a presurface zone of the bulk, single-crystal (110)Cr, implanted with 119Sn ions were studied by means of conversion electron Mössbauer spectroscopy. A strong enhancement of the magnetic hyperfine field, B, was found. The increase is by a factor of ~2.7 in the average value of B and by a factor of ~2.3 in the most probable value of B (the amplitude of the spin-density waves, SDW's). The observed effects are explained in terms of the interference of two spin-density waves having the same amplitude phase but various polarizations. The relative contributions of the interfering SDW's was estimated as equal to ~60% for those with mutual perpendicular and ~40% for those with mutual parallel polarization.
  • Physical Review B 63 (2001) 060406(R)-1-4

Publ.-Id: 3789 - Permalink


Synthesis, characterization and stability studies of some potential brains seeking agents-trialkyl (triaryl) siloxyalkyl(aryl)-thiolato-3-thiapentane-1,5-dithialato oxorhenium(V) complexes.
Abedin, Z.; Spies, H.;
Neutral lipophilic silicon organic compound of oxorhenium complexes were obtained by the "3+1" mixed ligand approach with the simultaneous complexation of one SSS tridentate ligand and a monodentate S-R ligand with the formation of the oxorhenium(V) complexes. Four trialkyl(triaryl)siloxyalkane(benzene)thiolato-(3-thiapentane-1,5-dithiolato)oxorhenium complexes of the general formula (SCH2CH2SCH2CH2S) ReO (SQOSiR3) were synthesized and studied where
IV, Q = CH2CH2, R = CH2 CH3
V, Q = CH2CH2 CH2, R = CH2 CH3
VI, Q = C6H5, R = CH2CH3
VII, Q = CH2CH2, R = C6H5
Identification and determination of structure of the compounds (IV-VII) and hydrolized products (I-III) were carried out by TLC, HPLC, elemental analysis and IR, UV and NMR spectroscopic methods. Lipophilicity was determined by reverse phase HPLC method. As a role the more lipophilic compounds should have stronger binding with the C18 chain of the column material giving higher retention time. The retention time of the silicon rhenium complexes(IV-(VII) and the corresponding OH compounds (I-III) of the general formula (SCH2CH2SCH2CH2S)ReO(SQOH) where I, Q= CH2 CH2, II, Q= CH2CH2 CH2, R = III, Q=C6H5, were determined as

Compound.....Retention time (min)..............Compound.......Retention time (min)
I.....................2.60.....................................IV....................4.16
II....................2.64......................................V....................4.26
III...................2.87......................................VI....................4.46
I.....................2.60......................................VII.................. 4.93

It observed that the retention time of the compounds increases with the increase of lipophilicity as expected on the reverse phase column and the introduction of alkyl or arylsilyl radical to the oxygen atom greatly increases the lipophilicity. Stability of the silicon rhenium complexes (IV-VII) was studied in acetonitrile-water solution at different temperature and pH by reverse phase HPLC method. Of the four compounds triethylsiloxyalkylthiolato (IV and V) complexes were found to be the most stable with respect to both temperature and pH changes. Trialkylphenylsiloxy compound (VI) was found to be most unstable one. All the compounds were labile in acidic pH. The most lipophilic compound (VII) was less soluble in acetonitrile-water (1:1) system.
  • Lecture (Conference)
    VII. Asia and Oceania Congress of Nuclear Medicine and Biology and IV. International Congress of Nuclear Oncology, 1.-5-10.2000, Istanbul/Turkey
  • Abstract in refereed journal
    Turkish Journal of Nuclear Medicine 9 (2000) 92

Publ.-Id: 3787 - Permalink


Bubble Size Distributions and Radial Profiles in Vertical Pipe Flow
Lucas, D.; Krepper, E.; Prasser, H.-M.;
The paper presents a method for the prediction of the radial gas fraction profile from a given total bubble size distribution. The method is based on the assumption of the equilibrium of the forces acting on a bubble perpendicularly to the flow direction. A large number of bubble classes is assumed. Based on the radial profile of the liquid velocity, radial distributions are calculated separately for all bubble classes. The resulting local bubble size distributions can be used by models for bubble coalescence and break-up. It is supposed, that the attempts for a one-dimensional modelling of bubble coalescence and break-up suffer in case of pipe flow from neglecting the radial profiles of the particle densities for the single bubble classes. The model is the basis of a fast running one-dimensional steady state computer code. The results of the model are compared with experimental data for a number of gas and liquid volume flow rates.
Keywords: Pipe flow, Two-phase flow, Flow regime
  • Poster
    3rd European Congress of Chemical Engineering, Nuremberg, 26 - 28 June, 2001, Conference-CD, File 532.htm; Abstract in Chemie Ingenieur Technik 73 (2001) 640
  • Contribution to proceedings
    3rd European Congress of Chemical Engineering, Nuremberg, 26 - 28 June, 2001, Conference-CD, File 532.htm; Abstract in Chemie Ingenieur Technik 73 (2001) 640

Publ.-Id: 3786 - Permalink


TEM-Untersuchungen an ionenstrahlmodifizierten Materialien
Mücklich, A.;
  • Lecture (others)
    Ehrenkolloquium anläßlich des 65. Geburtstages von Prof. Dr.-Ing. habil. Peter Klimanek an der TU Bergakademie Freiberg am 26. Mai 2000

Publ.-Id: 3785 - Permalink


3-O-methyl-6[18F]Fluor-L-DOPA (OMFD) - First experiences in brain tumor imaging
Franke, W.-G.; Alheit, H.-D.; Beuthien-Baumann, B.; Bergmann, R.; Bredow, J.; Brust, P.; Burchert, W.; Füchtner, F.; Johannsen, B.; Kretzschmar, M.;
F-18 labelled amino acid 3-O-methyl-6[18F]Fluor-L-DOPA (OMFD), not used for diagnostics until now, was synthesized, tested in cell cultures as well as in animals and studied in patients (pts) with recurrences of low differentiated brain tumors. Synthesis is based on a new precursor (N-formyl-3-O-methyl-4-O-Boc-6-trimethylstannyl-L-DOPA-ethyl-ester). Biologic behavior was tested HAT 29 and RBE-4-cell cultures and tumor bearing nude mice. First clinical studies we carried out in recurrent glioblastoma multiforme (4 pts.) with inconclusive MRT and CT. The application of OMFD was based on an individual decision. The aim was to detect localization and extent of recurrent tumor for planning of stereotactic radiotherapy. After 50 min synthesis time a radiochemical yield of 20 - 25% was reached. A high tracer uptake in tumor cells via L-amino-transporter was seen. However there was no evidence for metabolism or incorporation into proteins. Biodistribution in mice showed 60 min p.i. high intratumoral uptake (12.4 ± 1.8% ID/g) and a tumor/blood ratio of 9.5 ± 0.8. Increased radioactivity uptake was found in all pts. 60 min p.i. in the region of the suspected recurrences (lesion/nonlesion 2.2 ± 0.5), only little tracer uptake was found in the whole body scans in muscle, thorax and abdomen. Suspected recurrences were clearly seen in on PET images. Preliminary diagnostic studies in pts. With low differentiated tumor suggest that the new F-18 labelled amino acid is a valuable PET-tracer for tumor imaging.
Keywords: PET; F-18-OMFD; glioblastoma
  • Lecture (Conference)
    VII. Asia and Oceania Congress of Nuclear Medicine and Biology and IV. International Congress of Nuclear Oncology, 1.-5-10.2000, Istanbul/Turkey
  • Abstract in refereed journal
    Turkish Journal of Nuclear Medicine 9 (2000) 64

Publ.-Id: 3784 - Permalink


Studies in caffeine binding - The benefical role of aqueous media
Waldvogel, S. R.; Stephan, H.; Fröhlich, R.;
  • Poster
    2. SFB-Symposium des SFB 452 "Functional Supramolecular Systems", 27.-28.10.2000, Ruhr-Universität Bochum

Publ.-Id: 3783 - Permalink


Comparison of [18F]FHPG and [124/125I]FIAU for imaging herpes simplex virus type 1 tymidine kinase gene expression
Brust, P.; Haubner, R.; Friedrich, A.; Scheunemann, M.; Anton, M.; Koufaki, O.-N.; Hauses, M.; Noll, S.; Noll, B.; Haberkorn, U.; Schackert, G.; Schackert, H. K.; Avril, N.; Johannsen, B.;
Various radiotracers based on uracil nucleosides (e.g 2'-fluoro-2'-deoxy-5-[124I]iodo-1-beta-D-arabinofuranosyluracil, [124I]FIAU) and acycloguanosine derivatives (e.g. 9-[(3-[18F]fluoro-1-hydroxy-2-propoxy)methyl]guanine, [18F]FHPG) have been proposed as suitable substrates for the noninvasive imaging of herpes simplex virus type 1 thymidine kinase (HSV1-tk) reporter gene expression. However, for evaluation of these tracers different in vitro and in vivo models were used which did not permit a direct comparison of selectivity and affinity. Therefore, we directly compared [18F]FHPG and radioiodinated FIAU to assess their potential for PET imaging of transgene expression.
The uptake of [125I]FIAU, [18F]FHPG and [3H]acyclovir was determined in vitro using four different HSV1-tk expressing cell lines and their respective negative controls. The in vitro tracer uptake was generally low in nontransduced cell lines demonstrating low affinity to cellular thymidine kinases. In HSV1-tk expressing cells, [3H]acyclovir showed approximately a 2-fold higher tracer accumulation, the [18F]FHPG uptake increased to approximately 6-fold and the [125I]FIAU accumulation to approximately 28-fold after 120 min incubation of T1115 human glioblastoma cells. Similar results were found in the other cell lines. In addition, biodistribution and PET studies with [18F]FHPG and [124/125I]FIAU were carried out in tumour-bearing BALB/c mice. Significantly higher specific tracer accumulation was found for [125I]FIAU compared to [18F]FHPG. The ratio of specific tracer accumulation between [125I]FIAU and [18F]FHPG increased from 21 (30 min p.i.) to 119 (4 hours p.i.). PET imaging, using [124I]FIAU, clearly visualised and delineated HSV1-tk expressing tumours, whereas only a negligible uptake of [18F]FHPG was observed.
This study demonstrated that in vitro and in vivo, the radioiodine labelled uracil nucleoside FIAU has a significantly higher specific accumulation than the acycloguanosine derivative [18F]FHPG. This suggests that [124I]FIAU should be the preferred reporter probe for PET imaging of HSV1-tk gene expression. However, the use of [124I]FIAU is hampered by the relatively long physical half-life, the low positron emission and the limited availability of the radionuclide. Thus, further attempts to develop suitable PET tracers for the assessment of HSV1-tk gene expression should also focus on 18F-labelled uracil derivatives.

Keywords: Gene therapy; FHPG; FIAU; HSV-1 thymidin kinase; PET
  • European Journal of Nuclear Medicine Vol.28, No. 6, (2001) 721-729

Publ.-Id: 3782 - Permalink


Experimental and numerical investigation of one and two phase natural convection in storage tanks
Krepper, E.; Aszodi, A.; Prasser, H.-M.;
Experiments were performed to investigate heating up processes of fluids in storage tanks under the influence of an external heat source. As a consequence of an external fire, the heat-up of the inventory may lead to the evaporation of the liquid and to release of significant quantities of dangerous gases into the environment. Heating the vessel from the side walls, a strong temperature stratification is observed leading to large temperature gradients. At the top of the tank evaporation can start much earlier than the average temperature reaches saturation.
Several tests were performed both with heating from the bottom and with heating from the side walls. The test tank was equipped with thermocouples and with needle probes for measuring of the local void fraction.
In the FZ-Rossendorf calculations were performed using the CFD-code CFX-4. The simulation comprises two phase flow, subcooled boiling at the heated wall and steam release at the tank surface. The paper presents comparisons of measured and calculated temperatures and void fractions. The comparison allows, to test the used models, to clarify weak points of the models and to identify directions of further development of modelling boiling and two phase flow.
Keywords: heat transfer, boiling, single phase natural convestion, two phase flow, experiments, computational fluid dynamics calculations
  • Lecture (Conference)
    4th International Conference on Multiphase Flow, New Orleans, Lousiana, USA - May 27 to June 1, 2001, Conference-CD, Paper 515
  • Contribution to proceedings
    4th International Conference on Multiphase Flow, New Orleans, Lousiana, USA - May 27 to June 1, 2001, Conference-CD, Paper 515

Publ.-Id: 3781 - Permalink


Nutzung erneuerbarer Energien zur Stromerzeugung in den neuen Bundesländern
Rindelhardt, U.;
Schwerpunkte:

- Technische und wirtschaftliche Entwicklungen im letzten Jahrzehnt
- Derzeitige Beiträge der einzelnen erneuerbaren Energien
- Wirtschaftlichkeit unter den aktuellen Rahmenbedingungen
- Mittelfristige Perspektiven der Nutzung erneuerbarer Energien in der Stromerzeugung
  • Lecture (Conference)
    3. Energietechnisches Kolloquium der BTU Cottbus, 6.9.2001, in: BTU Forschungshefte Energie(Hrg. B. Schieferdecker, Ch. Fünfgeld): Energietag Brandenburg 2001, Beitrag 12
  • Contribution to external collection
    3. Energietechnisches Kolloquium der BTU Cottbus, 6.9.2001, in: BTU Forschungshefte Energie(Hrg. B. Schieferdecker, Ch. Fünfgeld): Energietag Brandenburg 2001, Beitrag 12

Publ.-Id: 3780 - Permalink


Validation of Coupled Codes for VVER Reactors by Analysis of Plant Transients
Mittag, S.; Kliem, S.; Weiß, F.-P.; Kyrki-Rajamäki, R.; Hämäläinen, A.; Langenbuch, S.; Danilin, S.; Hadek, J.; Hegyi, G.; Kuchin, A.; Panayotov, D.;
Three-dimensional hexagonal reactor dynamic codes have been developed for VVER type reactors and coupled with different thermal
hydraulic system codes. In the EU Phare project SRR1/95 these codes have been validated against collected real plant transients by the participants from 7 countries. The two experiments chosen for calculation were such that both primary circuit behaviour and fission power behaviour were strongly affected including movements of control rods. Critical boron concentrations, 3-D core power distributions, time behaviour of fission power, coolant temperatures and pressures were the main parameters utilised in the validation. Good accuracy of the results was generally achieved comparable to the measurement accuracy. Confidence in the results of the different code systems has increased and the consequences of certain model changes could be evaluated.
  • Lecture (Conference)
    Tagungsband der Fachtagung der KTG: "Wechselwirkungen Neutronenphysik und Thermofluiddynamik", pp. 4-55 bis 4-66, Forschungszentrum Rossendorf, 31. Januar - 1. Februar 2000
  • Contribution to proceedings
    Tagungsband der Fachtagung der KTG: "Wechselwirkungen Neutronenphysik und Thermofluiddynamik", pp. 4-55 bis 4-66, Forschungszentrum Rossendorf, 31. Januar - 1. Februar 2000

Publ.-Id: 3778 - Permalink


Development and Benchmarking of the DYN3D/RELAP5 Code System
Kozmenkov, Y.; Orekhov, Y.; Grundmann, U.; Kliem, S.; Rohde, U.; Seidel, A.;
The integration of advanced computer codes from different safety analysis areas into code systems of expanded modeling capabilities results in a more detailed and accurate representation of reactor plant structural components. Less conservative predictions of advanced codes are needed to analyse the transients of LWRs. As a result of the joint FZR-IPPE research project, the coupled code system DYN3D/RELAP5 has been developed. The incorporation of the DYN3D spatial kinetics model into the RELAP5 code overcomes the restrictions of the stand-alone codes. AER-5 benchmark calculations for the VVER-440 reactor plant have been performed to validate the code. Code-to-code comparison (DYN3D/RELAP5-DYN3D/ATHLET) of simulation results shows a good agreement and confirm a validity of the developed internally coupled code system.
Keywords: nuclear reactors system codes three-dimensional core model coupled code safety analysis benchmarks
  • Lecture (Conference)
    Jahrestagung Kerntechnik 2001, Dresden, 15 - 17 Mai 2001, Tagungsbericht S. 15 - 18.
  • Contribution to proceedings
    Jahrestagung Kerntechnik 2001, Dresden, 15 - 17 Mai 2001, Tagungsbericht S. 15 - 18.

Publ.-Id: 3775 - Permalink


X-ray waveguides with multiple guiding layers
Pfeiffer, F.; Salditt, T.; Hoghoj, P.; Anderson, I.; Schell, N.;
We have generalized the principle of resonant x-ray beam coupling to waveguiedes containing multiple guiding layers and characterised their x-ray optical properties. By measuring the farfield pattern formed by the interference of the beams, we demonstrate the possibility of using these devices as new tools to tailor the field distribution in the near- and far-field region for specific applications.
Keywords: x-ray waveguides: multiple layered structure; x-ray beam conditioning
  • Phys. Rev. B 62 (2000) 16939-16943

Publ.-Id: 3774 - Permalink


Si/Ge-nanocrystals in SiC(0001)
Heß, G.; Bauer, A.; Kräußlich, J.; Fissel, A.; Schröter, B.; Richter, W.; Schell, N.; Matz, W.; Goetz, K.;
Different SiC-surfaces were coated with thin layers of Si or Ge and subsequently annealed to 900 °C respective 600 °C. According to AFM results, Si- or Ge-clusters, respectively, are formed whose number, size distribution and shape depend on the process parameters. Such samples were investigated with synchrotron x-ray diffraction on the ROBL-beamline at the ESRF. The /2 - scans show for all samples (111)- and (220)-reflections of Si or Ge, respectively. This reveals unambiguously that the clusters grow preferentially in two different orientations (<111>, <110>). Interestingly, for the Ge-samples those reflections are shifted towards the angular position of the corresponding Si-reflection. Such a peak shift could be explained by a lattice distortion due to the lattice mismatch or by the change in the lattice constant due to the formation of a Si/Ge solid solution. The lateral orientation of the (111)- and (110)-clusters was investigated by comparison of the -scans of a cluster-reflection (220-reflection for (111)-clusters and 111-reflection for (110)-clusters) with an appropriate substrate-reflection. This comparison showed that the (111)-clusters as well as the (110)-clusters grow coherently with respect to the substrate.
Keywords: Si/Ge-nanocrystals; SiC; X-ray diffraction
  • Thin Solid Films 380 (2000) 86-88

Publ.-Id: 3773 - Permalink


A two magnetron sputter deposition chamber for in situ observation of thin film growth by synchrotron radiation scattering
Matz, W.; Schell, N.; Neumann, W.; Bøttiger, J.; Chevallier, J.;
The design of a sputter deposition chamber for the in situ study of film growth by synchrotron x-ray diffraction and reflectivity is reported. Four x-ray windows, sealed with low cost, non-hazardous Kapton, enable scattering both in the horizontal as well as in the vertical scattering planes. The chamber fits into a standard six-circle goniometer from Huber which is relatively widespread in synchrotron laboratories. Two miniature magnetrons and additional gas inlets allow for the deposition of compound films or multilayers. Substrate heating up to 650°C and different substrate bias voltage are possible. The performance of the chamber was tested with the deposition of high quality TiN films of different thicknesses.
Keywords: X-ray diffraction; in-situ investigations; sputter deposition; film growth
  • Review of Scientific Instruments Vol 72, Number 8 (2001) 3344-3348

Publ.-Id: 3772 - Permalink


Synthetische Huminsäuren und ihre Anwendung zur Untersuchung des Radionuklidtransports in der Umwelt
Sachs, S.; Bubner, M.; Schmeide, K.; Heise, K. H.; Bernhard, G.;
Die realitätsnahe Beschreibung der Wechselwirkung von Actiniden mit Huminsäuren sowie des Migrationsverhaltens von Actiniden in Gegenwart von Huminsäuren ist unerläßlich für zuverlässige Prognosen zur Ausbreitung von Actiniden in natürlichen Aquifersystemen. Da natürliche Huminsäuren jedoch in Abhängigkeit von ihrer Herkunft unterschiedliche strukturelle und funktionelle Eigenschaften zeigen, ergeben sich Schwierigkeiten bei der Beschreibung ihres chemischen Verhaltens. Zur Erlangung detaillierterer Kenntnisse über die Wechselwirkung von Huminsäuren mit Actiniden wurden verschiedenartige Huminsäuremodellverbindungen mit definierten chemischen Eigenschaften entsprechend dem Melanoidinkonzept entwickelt und hinsichtlich ihrer Eignung als Funktionalitätsmodelle für Huminsäuren untersucht [1]. Darüber hinaus wurden Verfahren zur Synthese von 14C-markierten Huminsäuren mit stabiler Markierung des Molekülgerüsts entwickelt [2], die aufgrund ihrer sehr empfindlichen Nachweisbarkeit in niedrigen Konzentrationsbereichen in Migrationsexperimenten, z.B. zur Untersuchung kinetischer Prozesse [3], einsetzbar sind.
Die vorliegende Arbeit demonstriert am Beispiel der synthetischen Huminsäure vom Typ M42, die mit natürlichen Huminsäuren vergleichbare Carboxylgruppenzahlen hat, die Synthese, die 14C-Markierung und die Modifizierung der Huminsäurefunktionalität als auch deren Einsatz in Komplexierungs- und Sorptionsexperimenten. Die unter Verwendung dieser Huminsäure erzielten Ergebnisse zur Untersuchung der Wechselwirkung von Huminsäuren mit Neptunium(V) werden vorgestellt. Dazu gehören auch Untersuchungen zum Einfluß phenolischer und anderer acider Gruppen auf das Komplexbildungsverhalten von Huminsäuren gegenüber Neptunium(V) im neutralen pH-Bereich. Der Vorteil der Radiotracertechnik durch Einsatz der 14C-markierten Huminsäure vom Typ M42 in Sorptionsexperimenten wird am Beispiel der Neptunium-Sorption an Granit in Gegenwart von Huminsäuren gezeigt.
Erste Ergebnisse zur Synthese von Huminsäuren mit ausgeprägt reduzierenden Eigenschaften werden dargestellt. Diese sollen zur Untersuchung von Redoxvorgängen bei der Wechselwirkung von Huminsäuren mit Actinidionen Einsatz finden.

[1] Pompe, S., Bubner, M., Schmeide, K., Heise, K.H., Bernhard, G., Nitsche, H.: Influence of Humic Acids on the Migration Behavior of Radioactive and Non-Radioactive Substances under Conditions Close to Nature. Synthesis, Radiometric Determination of Functional Groups, Complexation. Report FZR-290, Rossendorf 2000.
[2] Bubner, M., Pompe, S., Meyer, M., Heise, K.H., Nitsche, H.: Isotopically Labelled Humic Acids for Heavy Metal Complexation. J. Labelled Cpd. Radiopharm. XLI, 1057 (1998).
[3] Schmeide, K., Brendler, V., Pompe, S., Bubner, M., Heise, K.H., Bernhard, G.: Kinetic Studies of the Uranium(VI) and Humic Acid Sorption onto Phyllite, Ferrihydrite and Muscovite. In: Report FZKA 6524 (G. Buckau, ed.), Karlsruhe 2000, S. 149-169.
Keywords: Huminsäuren, Modellverbindungen, Synthese, Markierung, Modifizierung, Komplexierung, Neptunium, Sorption
  • Poster
    GDCh-Jahrestagung Chemie 2001, Fachgruppe Nuklearchemie, 24.-26.09.2001, Würzburg

Publ.-Id: 3767 - Permalink


Uranyl(VI) complexes with alpha-substituted carboxylic acids in aqueous solution
Moll, H.; Geipel, G.; Reich, T.; Bernhard, G.; Fanghänel, T.; Grenthe, I.;
Alpha substituted carboxylic acids are present as degradation products of wood in nature and in repositories for low-level radioactive waste. Such substances find extensive application in separation processes of various types, i.e., group separations of 4f and 5f elements. Their interaction with radionuclides was investigated in the pH range 3 to 5 mainly by potentiometry and NMR techniques. Whereas information on their structural and spectroscopic properties are rare.

The complex formation in the binary uranium(VI)-glycolate, -alpha-hydoxyisobutyrate, -alpha-aminoisobutyrate systems in 1.0 M NaClO4 medium was investigated by means of UV-vis and TRLFS. From spectroscopic investigations by UV-vis, single component absorption spectra are suggested and extinction coefficients calculated. An increase in absorption and a red shift of the spectra, 5 nm compared to the free UO22+, are indicating the interaction of UO22+ and a-substituted carboxylic acids already at pH 2. 1:1 complexes are dominating the uranyl speciation in the glycolate, alpha-hydoxyisobutyrate, and alpha-aminoisobutyrate system at pH 2 and 3, respectively. The formation constant of the 1:2 complex of uranyl with alpha-aminoisobutyric acid is reported for the first time at pH 4. A variety of techniques, such as XRD, XAS, TRLFS, and IR, were applied to explore the structure of the main species in solution and in solid state.

This work was supported by the European Union under contract number: HPMF-CT-1999-00342.

Keywords: Uranium(VI), Complex formation, Alpha-substituted carboxylic acids
  • Lecture (Conference)
    MIGRATION '01, 8th International Conference on Chemistry and Migration Behavior of Actinides and Fission Products in the Geosphere Bregenz, Austria September 16 - 21, 2001
  • Radiochimica Acta 91, 11-20 (2003)

Publ.-Id: 3763 - Permalink


Structure of high-spin states in 89Sr and 90Sr
Stefanova, E. A.; Schwengner, R.; Rainovski, G.; Schilling, K.-D.; Wagner, A.; Dönau, F.; Galindo, E.; Jungclaus, A.; Lieb, K. P.; Thelen, O.; Eberth, J.; Napoli, D. R.; de Angelis, G.; Axiotis, M.; Marginean, N.; Martinez, T.; Ur, C. A.; Kröll, T.; Gadea, A.; Kutsarova, T.;

High-spin states of 89Sr and 90Sr were studied via the reactions 82Se(11B,p4n) and 82Se(11B ,p3n), respectively, at a beam energy of 37 MeV. Gamma rays were detected with the GASP spectrometer. The level schemes of 89Sr and 90Sr were extended up to E ≈ 8 MeV and E ≈ 10 MeV, respectively. The level structures in 89Sr and 90Sr were interpreted in terms of the spherical shell model. The calculations were performed in the configuration space (0f5/2, 1p3/2, 1p1/2, 0g9/2) f or the protons and (1p1/2, 0g9/2, 1d5/2) for the neutrons. High-spin level sequences in 89Sr are characterized by coupling the unpaired d5/2 neutron to proton excitations of the core nucleus 88Sr. An equidistant level sequence with ΔJ = 2 found in 90Sr is well described by the configuration π[(0f5/2-2) (0g9/22)] ν(1d5/22) which favors even spins.
Keywords: Nuclear structure, in-beam gamma-ray spectroscopy, shell-model calculations

  • Physical Review C, Vol. 63, 064315-1 - 10

Publ.-Id: 3751 - Permalink


TransRay - ein dreidimensionaler Zellcode auf der Grundlage der Ray-Tracing Technik
Beckert, C.;
Es wurde ein Zellcode (TransRay) entwickelt, der mit Hilfe der Ray-Tracing Technik die dreidimensionale Neutronenflußverteilung berechnet. Ziel war es dabei unter anderem, für dreidimensionale Probleme gemittelte makroskopische Wirkungsquerschnitte zu ermitteln. Als Anwendungsbeispiel werden in dieser Arbeit zwei Fälle betrachtet, der teilweise eingetauchte Regelstab und Void um einen Brennstab als Modell für eine Dampfblase im Moderatorgebiet. Hierfür mußte die Ray-Tracing Methode auf Gebiete mit Void erweitert werden. Das häufig verwendete kommerzielle Programm HELIOS berechnet die gemittelten Wirkungsquerschnitte nur zweidimensional. Für eine bestimmte Eintauchtiefe des Regelstabes muß daher zum Beispiel zwischen den berechneten Werten des vollständig eingetauchten und des gezogenen Regelstabes interpoliert werden. In diesem Artikel wird zunächst die Theorie erläutert und anschließend werden Ergebnisse für die beiden oben erwähnten Fälle am Beispiel der Kernkonfiguration eines Leichtwasserreaktors gezeigt und kurz diskutiert.
Keywords: Ray Tracing Zellcode gemittelte Wirkungsquerschnitte Leichtwasserreaktor Void dreidimensional 3D Transportgleichung Eigenwert Neutronen Neutronenfluß Stoßwahrscheinlichkeiten Zellrechnung
  • Lecture (Conference)
    Jahrestagung Kerntechnik 2001, Dresden, 15.-17. Mai 2001, Tagungsbericht S. 51-54
  • Contribution to proceedings
    Jahrestagung Kerntechnik 2001, Dresden, 15.-17. Mai 2001, Tagungsbericht S. 51-54

Publ.-Id: 3750 - Permalink


Die Dynamik von Strahlenschäden durch fokussierte Ionenstrahlen am Beispiel der Ionenstrahlsynthese
Hausmann, S.;
  • Open Access LogoWissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-313 Januar 2001

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Publ.-Id: 3749 - Permalink


Liquid metal ion source-produced germanium ions for maskless ion implantation
Ganetsos, T.; Aidinis, C.; Bischoff, L.; Mair, G. L. R.; Teichert, J.; Panknin, D.; Popadopoulos, I.;
We report on a prelimery investigation on the maskless implantation of Ge ions into Si for the production of Si 1-x Gex microstructures. The technique employs a focused ion beam system using a liquid metal alloy ion source. Closely spaced simple structures down to about 1 µm in width, with well-defined boundaries, have been produced. On some of these structures, spreading resistance measruements were carried out.
Keywords: Si 1-x Gex microstructures, focused ion beam
  • Journal of Physics D: Appl. Phys. 34 (2001) L 11 - L13

Publ.-Id: 3746 - Permalink


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