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32179 Publications
Synthesis and biological evaluation of 7alpha Re/Tc "3+1" and cyclopentadienyltri- carbonylmetal (CpTM) estrogen mimics based on the conjugated design
Skaddan, M. B.; Wüst, F.; Welch, M. J.; Katzenellenbogen, J. A.;
The diagnosis and staging of breast cancer could be improved by the development of imaging radiopharmaceuticals that provide a non-invasive determination of the estrogen receptor (ER) status of tumor cells. Towards this goal, we have synthesized a number of Re and Tc-labeled estradiol (1) mimics based on the conjugated design, which tethers a metal-containing moiety to an existing steroid. In this study, the 7alpha position of estradiol was chosen as the tether site, due to its well known
tolerance of bulky substituents. 1 The metal was stabilized using either the "3+1" design (2,3), or the cyclopentadienyltricarbonylmetal (CpTM) approach (4,5,6) . In the "3+1" design, a tridentate ligand and a monodentate ligand surround an oxometal core.2 In the CpTM design, a substituted Cp and three carbonyls are coordinated to a Re/Tc(I) center.3,4
The advantages of using the "3+1" and CpTM desings are the well-established stability of both systems, as well as the ability to produce both systems efficiently at the tracer level.2,4
The first tether used was a hexyl spacer, and the synthesis of the precursors for targets 2-6 started with THP-protected estradiol 7 (Scheme 1). After oxidation to ketone 8 using a previously published method, standard alkylation conditions introduced the hexene side chain to form 9 , with BEt3 as an additive to stabilize the enolate and prevent O-alkylation.

Keywords: estrogen, radiotracers, rhenium, technetium
  • Lecture (Conference)
    13th International symposium on Radiopharmaceutical Chemistry, St. Louis, USA 27.6.-1.7.99
  • Abstract in refereed journal
    J. Labelled Cpd. Radiopharm. 42 (Suppl.1) (1999) S153-S155

Publ.-Id: 2084 - Permalink


Derivatization strategies of small biomolecules for the labeling with the organometallic "99mTc(CO)3"-core
Schibli, R.; Alberto, R.; Schaffland, A. O.; Schubiger, P. A.; Abram, U.; Pietzsch, H.-J.; Johannsen, B.;
Small, radiolabeled biomolecules, such as steroids, tracers for the central nervous system and biotin obtained considerable attention in diagnostic nuclear medicine. Nowadays, there are numerous short living isotopes available for SPECT (e.g. 131I) and PET (e.g. 18F, 11C) imaging to label such biological vectors. Despite this fact. Tc-99m is still the isotope of choice for diagnostic purpose because of its ideal decay properties. However, unlike iodinated of fluorinated radiopharmaceuticals, Tc-99m requires a highly sophisticated functionalization and coordination chemistry. Attempts to substitute direct covalent bound isotopes by Tc-99m chelates were, apart from peptides, only partially successful. (1,2) The reason is mainly the size of the introduced chelates (interference with active site of the biomolecule) and the redox sensitivity of 99mTc in the oxidation state +3 and +5. Therefore, alternative approaches are required to overcome these problems by introduction of small, redox inert 99mTc-cores in combination with simple ligand systems.
Although the idea of labeling e.g. steroids with organometallic Re or Tc-compounds was published by Top et al. In 1995 the attempt failed due to synthetic problems of the precursor on the no-carrier added level.(3) Our group recently pioneered the synthesis of the organometallic Tc(I) complex fac-[M(OH2)3(CO)3]+ (M=99mTc 1a, 99Tc 1b, Re 1c) under safe and pressureless conditions in aqueous media in high yields (<95%).(4,5) The compound is characterized by its water solubility, pronounced kinetic inertness (low spin d6 system) and the substitution lability of the three coordinated water molecules enabling effective labeling under mild conditions. The small size of the organometallic center will minimize the interference with the binding side of a biomolecule. Therefore, this new label optimi ...
Keywords: Tc-99m, organometallic, Biotin, WAY
  • Lecture (Conference)
    13th International symposium on Radiopharmaceutical Chemistry, St. Louis,USA, 27.6.-1.7.1999
  • Abstract in refereed journal
    J. Labelled Compd. Radiopharm. 42 (1999) S147-S149

Publ.-Id: 2083 - Permalink


Investigation and optimization of the emission parameters of alloy liquid metal ion sources
Bischoff, L.; Teichert, J.; Hausmann, S.; Ganetsos, T.; Mair, G. L. R.;
Liquid metal ion sources (LMIS) are one of the key elements in focused ion beam (FIB) technology. For special tasks, alloy LMIS are needed which have to be operated at elevated temperatures. For the adjustment of an optimal beam performance in a FIB system the source parameters, temperature of the ion emitter and the energy spread of the different used ion species are of fundamental importance. Emitters wetted with Au73Ge27, Au77Ge14Si9 and Co36Nd64 alloys were investigated with respect to the influence of the source temperature on the emission current - extraction voltage characteristics, the mass distribution, as well as the energy spread of the different emitted ions using an equipment containing of an ExB mass filter and a retarding field energy analyser. The energy spread significantly determines the available FIB spot size and depends also on the emission current, the charge state, and the mass of ions or clusters. The axial angular intensity and the resulting target current of the FIB were measured as a function of the source parameters. Two operating regimes were found. Whether one works in a high stable target current mode and lower resolution (emission current ~ 10 µA), or in the high resolution, high chromatic angular intensity mode (emission current a few µA), at the risk of lower target current including stability, both at source temperatures some ten degrees above the melting point.
Keywords: alloy liquid metal ion source, energy spread, source temperature, focused ion beam
  • Contribution to proceedings
    International Conference on ION BEAM ANALYSIS and European Conference on ACCELERATORS IN APPLIED RESEARCH AND TECHNOLOGY Dresden July 26 - 30 1999
  • Nuclear Instruments and Methods in Physics Research B 161-163 (2000) 1128-1131

Publ.-Id: 2081 - Permalink


Stillegung und Rückbau: Direktmessung alpha-aktiver Nuklide in Bauschutt zur Freigabeentscheidung, Schlußbericht zum Fördervorhaben 02 S 7655 und 02S7655A, Laufzeit: 01.05.1996 bis 31.10.1998
Nebelung, C.; Nitsche, H.;
Beim Abriß von Nuklearanlagen fallen große Mengen Bauschutt an, die mit Radionukliden kontaminiert sein können. Da diese Kontaminationen häufig nahe der Freigrenze liegen, ist für die Entscheidung, ob das Material als radioaktiver Abfall behandelt werden muß oder freigegeben werden kann, eine schnelle und exakte Methode notwendig. Die Bestimmung der ( - und $ - Aktivivtät ist mit in-situ Messungen möglich. Eine direkte Messung der " - aktiven Nuklide im stehenden Gebäude ist auf Grund der geringen Reichweite der " -Strahlung und ihrer Absorption im Beton nicht möglich. Die übliche chemische Analyse der " - aktiven Nuklide ist sehr zeitaufwendig.
Im Rahmen dieses Projektes wurde eine Methode der direkten " - Spektrometrie nach nur mechanischer Präparation des Betons entwickelt. In einem aus zwei Schritten bestehendem Zerkleinerungsprozeß wurden Suspensionen mit mittleren Partikeldurchmessern von 0,5 µm erhalten. Die Meßproben mit einem Durchmesser von 20 cm und Schichtdicken zwischen 0,6 und 5 µm wurden durch Gießen oder Sprühen auf die Probenträger und anschließendes Trocknen hergestellt. Die Spektren dieser Proben wurden in einer Gitterionisationskammer aufgenommen. Durch die Verwendung von Standardbeton mit dotierten Actiniden konnten die Selbstabsorption der " - Strahlung und die Peakform in Abhängigkeit der Schichtdicke ermittelt werden. Unbekannte Betonproben gleicher Geometrie konnten mit Hilfe dieser ermittelten Peakform entfaltet werden.
Das für diese Arbeit entwickelte Programm WINKRUM basiert auf einem geometrischen Modell für Partikelgröße, Partikelverteilung und Packungsdichte. Mit Strahlungstransportberechnungen können Spektren simuliert werden, die ebenfalls eine Peakentfaltung von Multielementspektren ermöglichen.
Mit dieser Direktmessung dünner Meßproben können " - aktive Nuklide bis zu 0,02 Bq/g in Multielementspektren innerhalb von 30 h bestimmt werden.


Keywords: Actinide, Alpha-aktive Nuklide, Alpha-Spektrometrie, Bauschutt, Beton, Dünne Schichten, Freigaberegelung, Freimessung, Kontamination, Nuklearanlagen, Stillegung
  • Other report
    Abschlußbericht BMBF Projekt 02S7655 und 02S7655A Juli 1999

Publ.-Id: 2080 - Permalink


Experimental and Numerical Investigations of the Coolant Mixing in Pressurized Water Reactors
Grunwald, G.; Höhne, T.; Prasser, H.-M.; Rohde, U.; Weiss, F.-P.;
For the analysis of boron dilution transients and main steam line break scenarios the modelling
of the coolant mixing inside the reactor vessel is important. The reactivity insertion due to
overcooling or deboration depends strongly on the coolant temperature and boron concentrati-
on.

The coolant mixing in the downcomer and lower plenum depends significantly on the con-
struction of the reactor vessel and flow conditions are different in each reactor type. In the
German Konvoi type reactors a complicated flow picture with large vortexes was obtained
which is typical probably also for the European Pressurized Water Reactor (EPR). The models
and assumptions for the coolant mixing description used in the coupled neutron kine-
tics/thermohydraulic system codes have to be validated on experimental data from the
Rossendorf coolant mixing model and detailed computational fluid dynamics (CFD) calcula-
tions.

The requirements concerning quality of the experimental results need a non-pressurized test
facility operating with water (room temperature). The reactor vessel is made of Plexiglas? for
flow visualization and LDA measurements. It has to dispose of separately controllable main
coolant pumps in each loop. The measurement instrumentation has to be designed for the
necessary spartial and time resolution.

The three-dimensional flow distribution in the downcomer and the lower plenum of PWRs
was calculated with a computational fluid dynamics (CFD) code (CFX-4).
  • Contribution to proceedings
    7th International Conference on Nuclear Engineering, Tokyo, Japan, April 19-23, 1999, ICONE-7815

Publ.-Id: 2079 - Permalink


SchaumPET – A Setup for Positron Emission Tomography (PET) Investigation of Foam in a Bubble Column
Hensel, F.; Prasser, H.-M.;
The paper describes a Positron Emission Tomograph dedicated to the investigation of the behavior of foam in a bubble column as well as the current planning of experiments using this device. In these experiments, foam generation, foam stability and transport phenomena in the liquid phase are the main topics of interest.
Keywords: positron emission tomography, nonmedical applications, BGO, coincidence logic, bubble column, foam
  • Lecture (Conference)
    Abstract in "4th Topical Meeting on Industrial Radiation and Radioisotope Measurements and Applications · IRRMA99" Conference Program and Abstracts. October 3-7 1999, Raleigh (USA). ISBN 0-89448-646-2, 32
  • Contribution to proceedings
    Abstract in "4th Topical Meeting on Industrial Radiation and Radioisotope Measurements and Applications · IRRMA99" Conference Program and Abstracts. October 3-7 1999, Raleigh (USA). ISBN 0-89448-646-2, 32

Publ.-Id: 2077 - Permalink


Investigation of a Density Measurement Technique using Positron Radiation
Hensel, F.;
The paper describes a density measurement technique using positron radiation. The method is appropriate for the determination of densities ranging from 10 kg/m3 to 100 kg/m3, e.g. for determining the density of foams or the humidity of pressurized gases. The focus of this paper is on the results obtained with an optimized low cost detector geometry. The technique makes use of the positron ranges in the measured matter, which is depending on its density.
Keywords: density measurement, positron, positron annihilation, BGO, coincidence measurement
  • Lecture (Conference)
    4th Topical Meeting on Industrial Radiation and Radioisotope Measurements and Applications, October 3-7 1999, Raleigh (USA). ISBN 0-89448-646-2, 9
  • Applied Radiation and Isotopes 53 (2000) 617-624

Publ.-Id: 2076 - Permalink


Micro-Raman and Ion Channeling Study of Crystal Damage in Si Induced by Focused Ion Beam Co Implantation
Teichert, J.; Bischoff, L.; Hausmann, S.; Voelskow, M.; Hobert, H.;
The lattice damage of silicon produced by ion implantation at extremely high current density of 0.8 A/cm2 (2.5 x 1018 cm-2 s-1) was investigated. In a focused ion beam system, implantation was carried out with 70 keV Co ions, fluences of 1.2 x 1016 cm-2 and 6.7 x 1015 cm-2 into Si (111) at room temperature and elevated temperatures between 355 °C and 400 °C. Radiation damage measurements were performed by Rutherford backscattering/channeling spectroscopy and micro-Raman analysis. The radiation damage was studied as a function of pixel dwell-time and implantation temperature. The critical temperature for amorphization increases with current density. Although the fluence of the focused ion implantation was constant, crystalline layers were obtained for short and amorphous layers for long pixel dwell-times. The critical dwell-time of crystalline/amorphous transition increases with implantation temperature. From the results a typical time for defect annealing of 10-5 s at 400 °C and an activation energy of (2.5±0.6) eV were deduced.
Keywords: focused ion beam, ion implantation, radiation damage, micro-Raman spectroscopy, ion channeling analysis, cobalt implantation
  • Applied Physics A 71 (2000) 175-180

Publ.-Id: 2075 - Permalink


Technologie zur Aktivierung gepreßter Targetmaterialien mit dem Protonenstrahl (12 MeV, 10 µA) des Zyklotrons U-120
Thümmel, H.-W.; Brückner, R.; Guratzsch, H.;
Es wird eine Technologie für die Aktivierung von gepreßten Pulver-Materialien (bis 500 mg) in einem Protonenstrom (10 µA) beschrieben. Das Verfahren wurde für die Herstellung von 94mTc am Rossendorfer Zyklotron U-120 aus angereichertem 94MoO3-Pulver optimiert. Die Bestrahlung des gepreßten Targetmaterials erfolgt in einem evakuierten und drucküberwachten Targetträger mit dünnem Strahleintrittsfenster. Durch die gute Wärmekopplung des Preßlings mit dem wassergekühlten Targetträger und der heli-umgekühlten Fensterfolie kann das Targetmaterial mit einer absorbierten Strahllei-stung bis zu 40 W belastet werden. Bei einem Folienbruch verhindert der geschlosse-ne Heliumkreislauf das Entweichen von radioaktivem Material. Zur Reduktion der Energieabsorption im Target wird die Dicke des Targetmaterials der Wirkungsquer-schnittsverteilung angepaßt. Nach der Entnahme des Targetträgers aus der Bestrah-lungsanlage verbleibt das Targetmaterial bis zur Aufarbeitung in einem radiochemi-schen Labor in dem geschlossenen Targetträger.

The technology described has been developed for safe activation of pressed powder materials (up to 500 mg) in a proton beam (10 µA). The procedure has been optimized for the production of 94mTc with the Rossendorf U-120 cyclotron using enriched 94MoO3. The target material is irradiated inside an evacuated and pressure controlled tar-getholder equipped with a thin entrance window for the proton beam. The target with-stands an absorbed beam power of about 40 W as the result of a good heat coupling between the target material and the water-cooled target holder as well as the helium-cooled entrance window. In the case of a window break the closed helium circuit pre-vents the escape of radioactivity. To diminish the energy absorption in the target the thickness is adapted to the distribution of the cross section. After taking the target holder out of the irradiation equipment, the target remains closed in the target holder ...

  • Open Access LogoWissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-265 Juli 1999

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Publ.-Id: 2074 - Permalink


First Application of fac-[99mTc(OH2)3(CO)3]+ in Bioorganometallic Chemistry: Design, Structure, and in Vitro Affinity of a 5-HT1A Receptor Ligand Labeled with 99mTc
Alberto, R.; Schibli, R.; Schubiger, P. A.; Abram, U.; Pietzsch, H.-J.; Johannsen, B.;
Bioorganometallic chemistry comprises the combination of an organometallic transition metal complex and a targeting biomolecule. If ever such a combination should be applied, the synthesis has to be convenient, fast and requires one or two steps only. [99mTc(OH2)3(CO)3]+ 1 can be prepared in one step from [99mTcO4]- in saline and bidentate aromatic amines are very efficient chelators for this organometallic precursor. Consequently, we have derivatized a 5-HT1A (serotonergic) receptor ligand with high affinity and high selectivity for this subclass from the group of the arylpiperazines with a Schiff Base type chelator. In water, 1 radiolabels the receptor ligand in high yield and specific activity.
Keywords: Technetium, serotonin receptor, 5-HT1A, Tc carbonyl complexes, bioorganometallic chemistry, schiff base, radio labelling
  • J. Am. Chem. Soc. 121, 25, 1999, 6076-6077

Publ.-Id: 2073 - Permalink


Numerical Studies of Neutron Distributions in GDT Experiments
Anikeev, A. V.; Noack, K.; Otto, G.;
In the Forschungszentrum Rossendorf the Fast Ion Transport code FIT has been developed on the base of the Monte Carlo method. It allows a detailed analysis of the fast ion field dynamics during GDT experiments [4]. Just, the code has been extended to enable not only the computation of the ion phase space distributions but also that of the neutron source distributions generated by various D-T fusion reactions. By means of FIT calculations the dependencies of the total neutron source strength and of the ion densities on several plasma parameters and operating regimes have been studied. The paper presents the numerical results and gives the physical interpretations.
  • Poster
    26th EPS Conference on Controlled Fusion and Plasma Physics, Maastricht, The Netherlands, 14-18 June 1999, Proceedings Vol. 23J, pp.1497-1500
  • Contribution to proceedings
    26th EPS Conference on Controlled Fusion and Plasma Physics, Maastricht, The Netherlands, 14-18 June 1999, Proceedings Vol. 23J, pp.1497-1500

Publ.-Id: 2071 - Permalink


Study of Hot-Ion Plasma Confinement in the Gas-Dynamic Trap
Anikeev, A. V.; Bagryansky, P. A.; Ivanov, A. A.; Karpushov, A. N.; Kornilov, V. N.; Maximov, V. V.; Murakhtin, S. V.; Noack, K.; Smirnov, A. Y.;
Studies of hot anisotropic ion confinement is one of the main objectives of the experimental program on the gas-dynamic trap (GDT). Hot ions are produced in the trap by injection of six neutral beams with energy 13-17 keV into collisional target plasma. The total injected power was up to 4.5 MW, pulse duration 1.2 ms. The behavior of hot ions with mean energy 3-10 keV and peak density of 0.5-1.0´ 1013 cm-3 was studied in detail in the experiments with plasma β up to 20%. The method of confinement study consists essentially in comparison of the measured ion parameters with those predicted by computer simulations based on theory of Coulomb collisions. Additionally the measurements of D-D neutron flux were used to measure the hot ion distribution along GDT axis.
  • Poster
    26th EPS Conference on Controlled Fusion and Plasma Physics, Maastricht, The Netherlands, 14-18 June 1999, Proceedings Vol. 23J, pp. 1781-1784
  • Contribution to proceedings
    26th EPS Conference on Controlled Fusion and Plasma Physics, Maastricht, The Netherlands, 14-18 June 1999, Proceedings Vol. 23J, pp. 1781-1784

Publ.-Id: 2070 - Permalink


Natural circulation experiments at the ISB-VVER Integral Test Facility and Calculations using the Thermal-Hydraulic Code ATHLET
Krepper, E.;
In 1995 at the integral test facility ISB-VVER in Elektrogorsk near Moscow natural circulation experiments were performed, which were scientifically accompanied by the Forschungszentrum Rossendorf. These experiments were the first of this kind at a test facility, which models VVER-1000 thermal-hydraulics. Using the code ATHLET which is being developed by "Gesellschaft für Anlagen- und Reaktorsicherheit mbH", pre- and post-test calculations were done to determine the thermal-hydraulic events to be expected and to define and tune the boundary conditions of the test. The conditions found for natural circulation instabilities and cold leg loop seal clearing could be confirmed by the tests. The main thermal-hydraulic phenomena were identified and compared with the results gained during similar experiments on VVER-440 test facilities.

  • Lecture (Conference)
    Ninth International Topical Meeting on Nuclear Reactor Thermal Hydraulics, San Francisco, California, October 3-8, 1999, (Conference CD)
  • Contribution to proceedings
    Ninth International Topical Meeting on Nuclear Reactor Thermal Hydraulics, San Francisco, California, October 3-8, 1999, (Conference CD)

Publ.-Id: 2069 - Permalink


Phase formation after high dose aluminium implantation into silicon carbide
Heera, V.; Reuther, H.; Stoemenos, J.; Pecz, B.;
High doses of 350 keV Al+ ions were implanted into 6H-SiC single crystals at 500oC. The phase formation was studied by TEM, SIMS and AES. A critical Al concentration of about 10 at% was found below that the 6H-SiC structure remains stable. The Al atoms
occupy preferentially Si sites in the SiC lattice. The replaced Si atoms seem to be mobile under the given implantation conditions and diffuse out. At higher Al concentrations the SiC matrix is decomposed and precipitates of Si and Al4C3 are formed.
It was found that the Al4C3 precipitates have a perfect epitaxial orientation to the SiC matrix. The phase transformation is accompanied by atomic redistribution and strong volume swelling. The resulting changes in the atomic profiles can be accounted
for by a simple chemical reaction model.
Keywords: Silicon Carbide, Aluminum Implantation, Phase Formation
  • Journal of Applied Physics 87 (2000) 78-85

Publ.-Id: 2068 - Permalink


Single-Crystalline CoSi2 Layer Formation by Focused Ion Beam Synthesis
Hausmann, S.; Bischoff, L.; Teichert, J.; Voelskow, M.; Möller, W.;
The effects of accumulated radiation damage which arise from the excessive current density employed
during focused ion beam implantation are described. The dwell time during beam scanning significantly
influences the focused ion beam synthesis of CoSi2 in Si. At sufficiently low accumulated damage,
single-crystalline CoSi2 layers are obtained, similarly to conventional ion implantation. A procedure is
described which enables the reduction of radiation damage induced by a focused ion beam to the level of
conventional ion implantation. This is of importance for the formation of single-crystalline CoSi2 layers.
  • Poster
    Microprocesses and Nanotechnology Conference 99, Yokohama, Japan, July 6-8, 1999
  • Japanese Journal of Applied Physics Vol. 38 (1999) pp. 7148-7150

Publ.-Id: 2067 - Permalink


Atomistic simulation of ion implantation and its application in Si technology
Posselt, M.; Schmidt, B.; Feudel, T.; Strecker, N.;
Atomistic computer simulations based on the binary collision approximation (BCA) are very well suited to predict the dependence of as-implanted dopant profiles on implant parameters like energy, dose and direction of incidence as well as on the arrangement of oxide, poly-Si and other materials on the single-crystalline Si substrate. In particular channeling effects, the enhanced dechanneling due to accumulation of radiation defects during ion bombardment and due to preexisting ion-beam-induced defects can be simulated in a reasonable manner. The BCA code Crystal-TRIM was successfully integrated into 1D and 2D process simulators for the Si technology. The application of the trajectory splitting algorithm and the lateral duplicatioin method ensures a high computational efficiency.
Keywords: Ion Implantation, Computer Simulation, Defects, Channeling, Silicon Technology, Process Simulation
  • Materials Science and Engineering B71 (2000) 128-136
  • Invited lecture (Conferences)
    E-MRS 1999 Spring Meeting, Symposium F: Process Induced Defects in Semiconductors, Strasbourg, France, June 1-4, 1999 (invited lecture)

Publ.-Id: 2066 - Permalink


Gold Complexes with Thiosemicarbazones and Phosohine Thiolates
Ortner, K.; Abram, U.; Hilditch, L.; Zheng, Y.; Dilworth, J.;
Square-planar AuIII complexes are isoelectronic to PtII compounds which are frequently used for cancer therapy. Recently, cancerostatic properties have also been reported for dichloro[2-(dimethylamino-methyl)phenyl-C1,N]gold(III), [Au(damp-C1,N)Cl2] (I) [1], although the mechanism of cytotoxic action may well be different. This encourages us to study the ligand exchange chemistry of this type of compound more in detail.
We have synthesized and structurally characterized a series of AuIII complexes with bi- and tridentate thiosemicarbazones as well as with chelating phosphine thiol ligands which surprisingly stabilize gold in its formal oxidation state "+3".
Reactions of (I) with thiosemicarbazones result in a cleavage of the Au-N bond and protonation of the liberated dimethylamino group. Airstable, zwitterionic compounds are formed. The thiosemicarbazones co-ordinate as deprotonated chelate ligands substituting Cl-. Fig. 1 illustrates an example with the bidentate vanillinethiosemicarbazone. Remaining Cl- ligands can be replaced by further ligand exchange reactions, e.g. with thiolates.
  • Poster
    37. IUPAC-Kongress, Berlin, August 1999

Publ.-Id: 2065 - Permalink


Rhenium and Technetium Complexes with Pyridylphosphines
Abram, U.; Alberto, R.; Dilwort, J.; Zheng, Y.; Ortner, K.;
Technetium and rhenium co-ordination chemistry is of particular interest due to the favourable nuclear properties of 99mTc (Eg = 140 keV, half-life t1/2 = 6.02 h) which makes this isotope the workhorse for diagnostic nuclear medicine. The b-emitting rhenium nuclides 186Re and 188Re are under investigation for possible applications in radioimmunotherapy. Fundamental co-ordination chemical studies form the basis for the development of new Tc and Re radiopharmaceuticals.
Diphenyl(2-pyridyl)phosphine (PPh2py) and tris(2-pyridyl)phosphine (Ppy3) are a versatile ligands which can co-ordinate as a monodentate or chelating ligands depending on the requirements of the metal center.
The potentially bidentate ligand PPh2py reacted with (NEt4)2[MI(CO)3X3] complexes (M = Re, Tc) to give (NEt4)[MI(CO)3X2(PPh2py-P)] or [MI(CO)3X(PPh2py-P)2] depending on the amount of the ligand used. The reaction with (NBu4)[TcVINCl4] yielded [TcVNCl2(PPh2py-P)2] whereas from the reaction with (NBu4)[ReOCl4] the complexes [ReVOCl3(PPh2py-P,N)], [ReVOCl3(OPPh2py-O,N)], [ReIVCl4(OPPh2py-O,N) and [ReIVCl3(OH)(OPPh2py-O,N)] have been isolated. Reduction of the metal center and formation of diphenyl(2-pyridyl)phosphine oxide (OPPh2py) occurs using an excess of PPh2py and heating of the reaction mixtures under reflux.
All products have been characterised spectroscopically and by X-ray structure analysis. Monodentate co-ordination via phosphorus has been found for the rhenium(I) carbonyl complexes and [TcVNCl2(PPh2py-P)2]. In the latter compound a trigonal-bipyramidal coordination sphere is formed with the phosphines as axial ligands. The chelated complexes show small N-Re-P and N-Re-O bite angles due to the 4-membered or 5-membered chelate rings. The pyridine nitrogen occupies the axial position (trans to "O2-") in [ReOCl3-(PPh2py-P,N)] whereas equatorial co-ordination is found in [ReOCl3(OPPh2py-O,N)].
The reaction of (NEt4)2[ReI(CO)3Br3] with Ppy3 gave [Re(CO)3Br(Ppy3-N,N')] whereas with o ...
  • Poster
    37. IUPAC-Kongress, Berlin, August 1999

Publ.-Id: 2064 - Permalink


Untersuchung zur Sorption von Huminsäure und Uran(VI) an den Kristallflächen des Schichtsilikates Muskowit
Krawczyk-Bärsch, E.; Schmeide, K.; Arnold, T.; Pompe, S.; Heise, K.-H.; Bernhard, G.;
In aeroben Batchexperimenten wurde der Einfluß von Huminsäure auf die Sorption von U(VI) u.a. auf dem Schichtsilkat Muskowit im pH-Bereich zwischen 3,5 und 9,5 untersucht (SCHMEIDE et al., 1998). Hierbei wurden 0,5 g der pulverisierten Probe (63µm - 200µm Körnung) in Kontakt mit einer Uranyl(VI)-Konzentration von 1.10-6 M und einer Huminsäure-konzentration von 5 mg/L gebracht, während die Ionenstärke mit 0,1 M NaClO4-Lösung konstant gehalten wurde. Aus den Ergebnissen ergibt sich eine pH-Wert abhängige Huminsäure-Sorption, die ihr Maximum (~ 83 %) bei einem pH von 4,5 bis 5 aufweist. Verglichen mit den U-Sorptionsversuchen, die in Abwesenheit von Huminsäure durchgeführt wurden (Zorn, 1999), wird die Sorption von U in Gegenwart von Huminsäure im pH-Bereich von < 5,8 vergrößert (67 % bei pH 5,5).

Elektronenmikroskopische Untersuchungen (REM) sollten im Anschluß an die Batch-experimente Aussagen zum Sorptionsverhalten an den Kristallflächen der Minerale liefern. Hierzu wurden einzelne Muskowitplättchen in Kontakt mit einer Huminsäure-Lösung der Konzentration von 40 mg/L für jeweils 1 und 18 Stunden gebracht. Die Huminsäure wurde zuvor filtriert (50 nm Filterporengröße), um u.a. Bakterien abzutrennen Die Einstellung der pH-Werte richtete sich nach den Ergebnissen aus den Batchexperimenten und wurde bei pH 4 für hohe Adsorption und zum Vergleich bei pH 7 für geringe Adsorption gewählt. Die Ergebnisse zeigen trotz starken Spülens der Proben mit entionisiertem H2O einen Überzug ("coating") des gesamten Bereiches der Mineralplättchen mit Huminsäure bei einer Verweildauer von 18 Stunden und einem pH von 4 in der Versuchsanordnung. Es kann daraus geschlossen werden, daß eine Sorption von U(VI) in diesem Fall überwiegend an der Huminsäure und nicht am Mineral stattgefunden hat. Im Gegensatz dazu zeigen die Proben, die lediglich für 1 Stunde in der Huminsäure verweilten kein vollständiges "coating". Erkennbar sind einzelne kugelige Huminsäurepartikel sowie Agglomerate v ...
  • Poster
    Workshop "Radiochemische Analytik beim Betrieb und Rückbau kerntechnischer Anlagen, der Deklaration von Abfällen und im Strahlenschutz", 06.-07.09.99 in Dresden

Publ.-Id: 2063 - Permalink


In-situ observation of electron-beam induced ripening of Ge clusters in thin SiO2 layers
Klimenkov, M.; Matz, W.; von Borany, J.;
A TEM technique was employed for the in-situ observation the Ge-clusters ripening process. Subsequent irradiation with electron beams of 200kV and 300kV acceleration energy lead to formation of a nanocluster band in the middle of thermally grown SiO2 thin layer implanted with Ge+. A number of micrographs taken during the ripening show the detailed information about process. The velocity of ripening can be controlled by changing of the irradiation intensity. The performed experiments pointed that ripening take place even for sample temperatures far below 1000K the activation threshold of thermal processes.
Keywords: Transmission Electron Microscopy, Nanocluster, Irradiation Effects
  • Nucl. Instr. Meth. in Phys. Res. B 168 (2000) 367-374

Publ.-Id: 2062 - Permalink


Preparation of Fluorine-18 labelled Sugars and Derivatives and their Application as Tracer for Positron-Emission-Tomography
Beuthien-Baumann, B.; Hamacher, K.; Oberdorfer, F.; Steinbach, J.;
The usefulness of 18F-labelled carbohydrates, especially 2-deoxy-2-[18F]fluoro-D-glucose, to study pathophysiological processes in man non-invasively using positron-emission-tomography (PET) led to a widespread investigation of different 18F-labelled sugars and sugar derivatives. In consideration of the short half-life of fluorine-18 (T1/2=110 min) synthetic strategies concerning precursor design, labelling conditions and deprotection of the intermediate compounds were developed to guarantee an efficient high radiochemical yield synthesis for diagnostic purposes. Besides some aspects of medical application of 2-deoxy-2-[18F]fluoro-D-glucose, a few synthetic strategies are described reflecting development work on promising 18F-labelled sugars for diagnostic purposes during the last two decades
Keywords: Positron-emission-tomography; 18F-Labelled carbohydrates; Medical application
  • Carbohydrate Research 327 (2000) 107-118

Publ.-Id: 2061 - Permalink


A new one-dimensional Particle-In-Cell model for multiphase vessel flow
Lucas, D.;
A new one-dimensional Particle-In-Cell transport model for multiphase flow in a vessel is presented. The model aims at the consistent simulation of discontinuities as the top level of a multi-phase mixture. That makes it possible to include models for the transient behaviour of a foam layer on top of a mixture for example. The transport model, which is the basic component of a new computer code will be described. Flexible interfaces allow the implementation of models, constitutive laws or correlations for extra effects like phase transfer, generation and coalescence of bubbles or drops, foam behaviour, heat transfer, discharge from the vessel a.s.o. Due to these interfaces and a transparent code structure the code is a suitable basis for the development, test and validation of models. It allows the completion or the replacement of such models according to the specific application.


Keywords: transient simulation, multiphase flow particle method, numerical diffusion, chemical reactor depressurisation, foam discontinuity
  • Journal of Thermal Sciences 38 (1999) 758-768

Publ.-Id: 2060 - Permalink


Nitridorhenium(V)-Komplexe mit Dimercaptobernsteinsäuredimethylester. Präparation, Charakterisierung und Kristallstruktur von [Re{NC(CH3)2PPhMe2}(DMSMe2)2]
Seifert, S.; Leibnitz, P.; Spies, H.;
Die Reaktion von [ReNCl2(Me2PhP)3] 1 mit zwei Äquivalenten Dimercaptobernsteinsäuredimethylester (DMSMe2) in Aceton führt zur Bildung eines neutralen, diamagnetischen Rhenium(V)-DMSMe2-Komplexes unter Anlagerung einer Phenyldimethylphosphanisopropyl-Gruppierung am nukleophilen Nitrid-Stickstoff. Der entstehende Komplex 2 [Re{NC(CH3)2(Me2PhP)}(DMSMe2)2] kristallisiert triklin in der Raumgruppe P1, a = 12,334(7), b = 12,412(7), c = 12,414(8) Å; alpha = 60,14(3)°, beta = 67,98(3)°, gamma = 80,63(6)°; Z = 2. Das Rhenium befindet sich in einer quadratisch-pyramidalen Anordnung der Donoratome. Die beiden meso-DMSMe2-Liganden sind in syn-endo-Stellung angeordnet. Die Rhenium-Stickstoff-Bindung ist mit 1,697(12) Å nur wenig länger als in Nitridokomplexen und vergleichbar mit anderen Re-N-C-Bindungsabständen. Der Angriff des Lösungsmittels am Nitridostickstoffatom wird in Aceton (2) und Methylethylketon unter Bildung von 3 beobachtet. Massenspektrometrisch wird darüberhinaus nachgewiesen, daß auch eine Reaktion des Nitridostickstoffatoms mit dem Kondensationsprodukt des Methylethylketons erfolgt unter Bildung von [ReN{C(CH3)(C2H5)CH2C(O)C2H5(Me2PhP)}(DMSMe2)2]) 4.
Keywords: Rhenium complexes; nitrido compounds; DMS complexes; X-ray diffraction
  • Zeitschrift fuer anorganische und allgemeine Chemie 1999, 625, 1037-1040

Publ.-Id: 2059 - Permalink


Tritium Depth Profiling in Carbon by Accelerator Mass Spectrometry
Friedrich, M.; Pilz, W.; Sun, G.; Behrisch, R.; Garcia-Rosales, C.; Bekris, N.; Penzhorn, R.-D.;
Tritium depth profiling measurements by accelerator mass spectrometry have been performed at the facility installed at the Rossendorf 3 MV Tandetron. In order to achieve a uniform erosion at the target surface inside of a commercial Cs ion sputtering source and to avoid edge effects, the samples were mechanically scanned and the signals were recorded only during sputtering at the centre of the sputtered area. The sputtered negative ions were mass analysed by the injection magnet of the Tandetron. Hydrogen and deuterium profiles are measured with the Faraday cup between the injection magnet and the accelerator, while the tritium is counted after the accelerator with semiconductor detectors. Depth profiles have been measured for carbon samples which had been exposed to the plasma at the first wall of the Garching fusion experiment ASDEX-Upgrade and from the European fusion experiment JET, Culham/UK. The tritium contents of the samples from JET were one up to five orders higher compared to the samples from ASDEX-Upgrade. The problem of the detector overloading during measurements of samples with a high tritium content has been solved by installation of a scanning system in the AMS beamline, which enables defined scanning of the tritium beam over an aperture in front of the detector.
Keywords: Accelerators, Ion Beam Analysis, Mass Spectrometry, Nuclear Fusion
  • Contribution to proceedings
    Proceedings 8th International Conference on Accelerator Mass Spectrometry, Wien, September 6-10, 1999, Nuclear Instruments and Methods B
  • Nuclear Instruments and Methods in Physics Research B 161-163 (2000) 216-220

Publ.-Id: 2058 - Permalink


SYNTHESIS OF A NEW TRACER FOR CANCER IMAGING: 16alpha-[18F]FLUOROESTRADIOL-3,17beta-DISULPHAMATE
Römer, J.; Füchtner, F.; Steinbach, J.;
The synthesis of 16alpha-[18F]fluoroestradiol-3,17beta-disulphamate ([18F]FESDS) being a new potential radiotracer for investigations in positron emission tomography is described. 16alpha-[18F]Fluoroestradiol ([18F]FES) is converted with excessive sulphamoyl chloride in absolute acetonitrile in presence of an alkali. Using kryptofix 2.2.2 and K2CO3 as alkali, [18F]FESDS was obtained in yields of 50 - 60%.
Keywords: Synthesis, 18F labelling, radiotracer
  • Lecture (Conference)
    8th Conference of Central European Division of International Isotope Society, Bad Soden, 10.-11.6.1999

Publ.-Id: 2057 - Permalink


Vibration analysis of the pressure vessel internal of WWER-1000 type reactors with consideration of fluid-structure interaction
Perov, S.; Altstadt, E.; Werner, M.;
The influence of fluid-structure interaction (FSI) on vibration modes is investigated using the finite element method. The method of modelling is verifyed by comparing the finite element results with the exact analytical solution of a simple fluid-shell test system. It is shown that the method of coupling between structural and fluid elements is important for the accuracy of the eigenfrequencies. The vibration modes of the reactor pressure vessel and its internals of a WWER-1000 type reactor are calculated. The FSI causes a considerable down shift of the shell mode frequencies of pressure vessel, core barrel and thermal shield. Some bending modes which exhibit a relative displacement between pressure vessel and core barrel or between core barrel and thermal shield are significantly affected too. Some simple analytical approaches to consider the FSI are discussed on the basis of the numerical results.
Keywords: fluid-structure interaction, finite-element-method, pressurized water reactor
  • Annals of Nucl. Energy 27 (2000) 1441-1457

Publ.-Id: 2055 - Permalink


Pulsations of the Mass Flow Rate during Pressure Relief
Lucas, D.; Prasser, H.-M.;
During two­phase blowdown from pressure vessels considerable pulsations of the discharged mass flow rate were found. Regions of instability were predicted by a linear stability analysis. The oscillations are caused by the following feedback circuit: boil up ­ level movement ­ void fraction of the discharged mixture ­ critical discharge rate ­ velocity of pressure decrease ­ boil up. They were also found at transient simulations. Finally the instabilities were confirmed by experiments. The possibility of the occurence of oscillations increases with the volume of the ventline and the volume void fraction of the discharged mixture. They may influence the pressure relief from pressure vessels as well as from chemical reactors.
Keywords: Two-Phase Flow, Instability, Pressure Relief, Analysis of Stabilty
  • International Journal of Thermal Sciences 42(2003)5-14

Publ.-Id: 2054 - Permalink


The use of acoustic emission to determine characteristic dynamic strength and toughness properties of steel
Richter, H.; Böhmert, J.; Viehrig, H.-W.;
The dynamic J integral at crack initiation (Jid) and dynamic yield stress (σyd) are useful parameters to characterize elastic-plastic material behaviour under rapid loading rates. The critical step for evaluating Jid and σyd under the condition of the three point impact bending test is the detection of the crack initiation and of the yield point in the impact load-deflection curve, respectively.

This paper presents an acoustic emission (AE) based method to determine the ductile crack initiation and additionally the beginning of yield. The experimental techniques used to evaluate σyd and Jid include both instrumented pendulum impact tests with the AE transducer within the striker (tup) and medium rate three point bend (TPB) tests with additional AE transducers on the specimen surface.

Results obtained from the tests indicate that the AE method is capable of detecting general yielding and the onset of ductile crack growth (initiation). Different types of pulse shaped AE signals can be observed. They were connected with characteristic features during the loading process

  • Nuclear Engineering and Design 188 (1999), 241-254

Publ.-Id: 2052 - Permalink


The ELBE Radiation Source Project
Enghardt, W.; Gabriel, F.; Gippner, P.; Grosse, E.; Guratzsch, H.; Janssen, D.; Michel, P.; Nething, U.; Neubert, W.; Prade, H.; Schilling, K.-D.; Schwengner, R.; Seidel, W.; Steegmüller, U.; vom Stein, P.; Wagner, W.; Wenzel, M.; Wolf, A.; Wünsch, R.;
  • Acta Physica Polonica B, No. 5, Vol. 30 (1999), pp. 1639-1645

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Publ.-Id: 2051 - Permalink


Inhibition of the Oxidation of Intermetallic TiAl by Ion Implantation
Hornauer, U.; Günzel, R.; Reuther, H.; Richter, E.; Wieser, E.; Möller, W.;
The effect of ion beam implantation and plasma immersion ion implantation of chlorine on the high temperature oxidation of titanium aluminides above 800 °C in air was investigated. Thermogravimetric oxidation tests (TGA) were performed to examine the long term protection. Depth profiling with Auger electron spectroscopy (AES) was used to investigate Cl diffusion and oxide formation during the first stage of oxidation. A microscopic model of the chlorine effect will be discussed. A systematic variation of the implantation energy and fluence shows that there is a narrow regime of the Cl concentration for optimum protective effect at 900°C in air. The oxidation rate after this incubation time is reduced by about 2 orders of magnitude compared to untreated Ti50Al and is nearly independent of the fluence. The effect is almost independent of the implantation energy in the range of 15 keV to 1 MeV. First results of plasma immersion ion implantation of chlorine show that it is possible to use this technique to implant also large and complex surfaces.
Keywords: Implantation, TiAl, Intermetallics, Oxidation, high temperature oxidation,Plasma immersion ion implantation, PSI
  • Lecture (Conference)
    8th Week of Doctoral Students (WDS), Charles University, Prag 1999, 24.06.1999

Publ.-Id: 2050 - Permalink


Molecular-dynamics simulations of steady-state growth of ion-deposited tetrahedral amorphous carbon films
Jäger, H.-U.; Albe, K.;
Atomic-scale modeling of ta-C thin film deposition by molecular dynamics simulations is an indispensable tool for understanding growth, structure and properties of diamond-like carbon in detail. Even if much progress has been achieved in recent years, simulations comparable to experiments are for several reasons still an enormeous challenge: A large number of impacts has to be calculated in order to achieve steady-state growth conditions. Long time intervals between individual impacts, which correspond to real ion fluxes, are necessary to allow for full structural relaxation of the growing film. The simulation ensemble has to be large enough, so that the dynamics of atoms in the growing film is not affected by external thermostats. Finally, force-field calculations are necessary, which are computationally efficient, but allow for a realistic description of the chemical specifities of the growing amourphous carbon structures.

In this contribution we present classical molecular-dynamics simulations, which try to balance the above-named criteria and deliver results directly comparable to experiments. All simulations were performed on base of the Brenner-potential, but with a slightly modified interaction radius, which corrects several shortcomings of the original form. Using this computationally efficient and chemically accurate potential function we have calculated the impacts of 1200 carbon atoms with 15 ps relaxation time after every impact. In contrast to previous works our simulations were performed for realistically thermalized targets and yield steady-state film structures, which were carefully analyzed. The sp3-contents for the deposited ta-C films vary between 58 % and 90 % for the C+ ion energies E = 30-80 eV and are in good agreement to experimental findings.

  • Poster
    MRS 1999 Fall Meeting, Nov. 29 - Dec. 3, Boston,USA; Symp. U: Amorphous and Nanostructured Carbon
  • Poster
    10th European Conference on Diamond, Diamond-Like Materials, Carbon Nanotubes, Nitrides & Silicon Carbide, 12 - 17 September 1999, Prague, Czech Republic

Publ.-Id: 2049 - Permalink


Bericht der Frühjahrstagung der Studiengruppe für Elektronische Instrumentierung vom 22.-24. März 1999 in der Ruhr-Universität in Bochum
Gabriel, F.;
  • Open Access LogoWissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-261 Mai 1999

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Publ.-Id: 2048 - Permalink


Interface-mediated synthesis of hydroxyapatite
Pham, M. T.; Matz, W.; Reuther, H.; Richter, E.; Steiner, G.; Oswald, S.;
The interface water vapour-titanium was employed for a controlled synthesis of surface-supported hydroxyapatite. In this approach, a Ti surface was doped with Ca and P by ion implantation and then subjected to a hydrothermal treatment in a water vapour autoclave. Ion implantation served to prepare a reactive blend of finely dispersed reactants in a stoichiometric ratio incorporated within the network of an outermost layer of the substrate surface. Needle-like carbonate hydroxyapatite in an overlayer was identified to deposit on the surface. The results suggest interface-mediated thin film formation and phase transformation.
Keywords: biomaterials, surface coating, hydroxyapatite, titanium implants, ion implantation, materials technology
  • J. Biomed. Materials Research 59 (2002) 254-258

Publ.-Id: 2047 - Permalink


Nitrogen and boron implantation into austenitic stainless steel
Mändl, S.; Günzel, R.; Richter, E.; Möller, W.;
  • Journal of Vacuum Science and Technology B 17 (2), Mar/Apr 1999, 832-835
  • Lecture (Conference)
    4th Int. Workshop on PBII, Dearborn, June 2-4, 1998

Publ.-Id: 2046 - Permalink


Synthesis and characterization of the bromide and hydride derivatives of rhenium(I) 1,2-bis(diphenylphosphinite)ethane complexes
Bolano, S.; Bravo, J.; Carballo, R.; Garcia-Fontan, S.; Abram, U.; Vazquez-Lopez, E.;
  • Polyhedron 18 (1999) 1431-1436

Publ.-Id: 2045 - Permalink


Comparative Study of a Boron Dilution Scenario in VVER Reactors
Ivanov, K. N.; Grundmann, U.; Mittag, S.; Rohde, U.;
Subsequent studies have identified many scenarios which can lead to reactivity excursions due to boron dilution. The comparative study, presented in this paper, deals with the so-called "restart of the first reactor coolant pump" scenario and its reactor-dynamic consequences for the both VVER reactor types - VVER-440 and VVER-1000. The transient simulations were performed using the three-dimensional core dynamics code DYN3D. The DYN3D modeling features, including recent developments, as well as the cross-section generation methodology, involved in these calculations, are described. The analyzed accident scenario is outlined together with the assumptions made. The results of core response in this boron dilution accident for both VVER reactors have been compared within ranges, determined by the two reactivity values of interest: the criticaly limit and the reactivity initiated accident (RIA) limit.
Keywords: VVER-reactors boron dilution transient three-dimensional core dynamics reactivity initiated accidents computer code DYN3D group constants cross section library comparisons
  • Annals of Nuclear Energy 26 (1999) 1331-1339

Publ.-Id: 2044 - Permalink


The stability of 2-[18F]fluoro-deoxy-D-glucose towards epimerisation under alkaline conditions
Meyer, G. J.; Matzke, K. H.; Hamacher, K.; Füchtner, F.; Steinbach, J.; Notohamiprodjo, G.; Zijlstra, S.;
Alkaline hydrolysis of 1,3,4,6-tetraacetyl-2-(18F]fluoro-deoxy-D-glucose in the course of 2-[18F]fluoro-deoxy-D-glucose (18FDG) synthesis offers special advantages over acidic hydrolytic procedures, because the reaction time is short and thermal requirements are very mild. In view of the possible epimerization of 2-[18F]fluoro-deoxy-D-glucose a multi-centre study has been performed to check the safety of this method for routine production of 18FDG in view of the quality standards set by the European Pharmacopoeia. The study revealed that in using 0.33 M NaOH for the hydrolysis, a limitation of the reaction temperature to 40°C and a restriction of the reaction time to 5 min represent reaction conditions, which reliably limit the epimerization of 18FDG to 18FDM to 0.5%. Regarding the quality requirements on FDG as set forth by pharmacopoeial standards, alkaline hydrolysis of the intermediate in routine 18FDG production is a safe and efficient reaction pathway, which furthermore obviates the requirement to check for other 2-substituted deoxy-D-glucose derivatives.
  • Applied Radiation and Isotopes 51 (1999) 37-41

Publ.-Id: 2042 - Permalink


Ion beam synthesis of narrow Ge nanocluster bands in thin SiO2 films
von Borany, J.; Heinig, K.-H.; Grötzschel, R.; Klimenkov, M.; Strobel, M.; Stegemann, K.-H.; Thees, H.-J.;
This paper reports on self-organization of narrow bands of Ge nanoclusters in thin thermally grown SiO2 layers by means of ion beam synthesis. Although the implanted Ge profile is distributed over almost the whole SiO2, a delta-like nanocluster band very close to, but well separated from the Si/SiO2 interface is formed under specific implantation and annealing conditions. The evolution of this band can be explained by a model taking into account collisional ion beam mixing and reactions near the Si/SiO2 interface, which describes in good agreement the experimental results. The reliable fabrication of such cluster bands are the basis for new memory applications.
Keywords: ion beam synthesis, thin SiO2 films, nanocluster, self-organisation, non-volatile memories
  • Microelectronic Engineering 48 (1999) 231-234
  • Lecture (Conference)
    Insulating Films on Semiconductors,INFOS'99, Kloster Ban7, Germany, June 16-19,1999

Publ.-Id: 2041 - Permalink


Dendrimere als selektive Carrier und medizinische Diagnostika
Stephan, H.; Berger, R.; Spies, H.; Johannsen, B.; Klein, L.; Vögtle, F.;
Dendrimere sind aufgrund ihrer Fähigkeit zur Wirt/Gast-Wechselwirkung und ihrer einzigartigen Oberflächenfunktionalität in der nuklearmedizinischen Diagnostik sowie als synthetische kationische Liposomen von großem Interesse.

Durch Einbau spezieller Haftgruppen für Technetium in divergent aufgebaute Dendrimere auf Basis eines Poly(aminoamido)- bzw. Poly(propylenimin)-Grundgerüstes kann sowohl die spezifische Aktivität erhöht als auch die Bioverteilung gesteuert werden. Das Komplexbildungsverhalten dieser neuartigen Dendrimere soll im homogen wäßrigen Einphasensystem studiert sowie die Transporteigenschaften im organisch-wäßrigen Zweiphasensystem charakterisiert werden. Außerdem sind in-vitro-Bestimmungen der radiopharmakologisch relevanten Größen wie Proteinbindung und Lipophilie sowie in-vivo-Untersuchungen zur Bioverteilung vorgesehen.

Erste Ergebnisse liegen für Harnstoff-funktionalisierte Dendrimere vor. Diese Verbindungsklasse (vgl. Abb.) ist deutlich lipophiler als kommerziell erhältliche PAMAM- und PPI-Dendrimere.

Insbesondere die Alkylharnstoff-Dendrimere binden Oxoanionen effektiv und sind in der Lage, Pertechnetat aus einer wäßrigen Lösung in Chloroform zu extrahieren.
Biologisch relevante Substrate wie AMP, ADP und ATP werden mit bemerkenswerter Abstufung in die organische Phase überführt. Dabei konnte mittels massenspektrometrischer Untersuchung nachgewiesen werden, dass von einem Dendrimer 5 Moleküle ATP gebunden werden.
  • Poster
    Statusseminar "Funktionale Supramolekulare Systeme", Frankfurt am Main, 21.-22. Juni 1999

Publ.-Id: 2040 - Permalink


Coupling of the Thermohydraulic Code ATHLET with the Neutron Kinetic Core Model DYN3D
Grundmann, U.; Lucas, D.; Rohde, U.;
  • Lecture (Conference)
    International Conference "Thermophysical Aspects of WWER-Type Reactor Safety", Obninsk, Russia, 21. - 24. November 1995
  • Contribution to proceedings
    International Conference "Thermophysical Aspects of WWER-Type Reactor Safety", Obninsk, Russia, 21. - 24. November 1995, Proc. Vol. 2, pp. 155 - 164

Publ.-Id: 2037 - Permalink


BRICK - ein Simulationstool für Mehrphasenströmungen in Behältern auf der Basis einer Partikelmethode
Lucas, D.;
In dem neu entwickelten 1-D-Behältermodell BRICK werden die Transportvorgänge in
Behältern auf der Grundlage einer neu entwickelten Partikelmethode gelöst.
Die Methode zielt auf die Vermeidung numerischer Diffusion, was insbesondere bei der Berücksichtigung von Diskontinuitäten, wie z.B. dem Gemischspiegel, von
Vorteil ist. Die implizite Wiedergabe der aktuellen Position des Gemischspiegels sowie ein spezielles Interface ermöglichen die Beachtung der Entwicklung einer
Schaumkrone am Übergang zwischen dem Zweiphasengemisch und dem Gasraum.

  • Lecture (Conference)
    1. Chemnitzer Verfahrenstechnisches Kolloquium, 25.-26. November 1998, TU Chemnitz
  • Contribution to external collection
    1. Chemnitzer Verfahrenstechnisches Kolloquium, 25.-26. November 1998, TU Chemnitz

Publ.-Id: 2036 - Permalink


Modellierung der Kühlmittelvermischung im Ringraum von Druckwasser- reaktoren mit Hilfe von Methoden der numerischen Fluiddynamik
Höhne, T.;

Es wurden für die Simulation die DWR Konvoi und WWER-440 ausgewählt, wobei hierbei sich auf die Netzgenerierung des Downcomerbereiches und des untereren Plenums beschränkt wurde. Hierbei wurde das dreidimensionale Strömungsberechnungsprogramm CFX 4.1 eingesetzt, welches die Navier-Stokes-Gleichungen löst. Das verwendete Turbulenzmodell war das k-Epsilon-Modell. Die Strömung des Kühlmittels wurde inkompressibel gerechnet. Es wurde Wert auf eine möglichst originalgetreue Gestaltung des Stutzenbereiches / Schrägen bzw. Erweiterungen im Downcomer und Rundungen der Stutzenpartien gelegt. Der Bereich hoher Geschwindigkeitsgradienten wurde mit einem dichteren Grid generiert.
  • Lecture (Conference)
    Workshop Kompetenzerhaltung Kerntechnik, KTG-Jahrestagung, München, 28.5. 1998

Publ.-Id: 2034 - Permalink


Coolant Mixing in Pressurized Water Reactors
Höhne, T.;
The three-dimensional flow distribution in the downcomer and the lower plenum of PWR's was calculated with a computational fluid dynamics (CFD) code (CFX-4) and the results were presented at the conference
  • Lecture (Conference)
    AEA Technolgy, CFD, User Conference, Unterhaching, 19.-20.5. 1998
  • Contribution to proceedings
    AEA Technolgy, CFD, User Conference, Unterhaching, 19.-20.5. 1998

Publ.-Id: 2033 - Permalink


Effects of titanium and aluminum incorporations on the structure of boron nitride thin films
Kolitsch, A.; Wang, X.; Manova, D.; Fukarek, W.; Möller, W.; Oswald, S.;
Boron nitride (BN) based composite thin films have been prepared by ion beam assisted deposition (IBAD) employing two electron beam evaporators. 3~5 at.% either Ti or Al was incorporated into the BN composite films. Fourier transform infrared (FTIR) spectroscopy was used for phase identification of the BN composite films. The influences of the Ti and Al additions on the cubic phase formation in the BN films are reported. It has been found that the Al incorporation has a strong negative effect on cubic BN (cBN) formation. No cubic phase can be obtained under the presently chosen ion-bombardment parameters. However, the disturbance of 3~5at.% Ti addition depending on the preparation conditions for the BN thin films, only shifts the threshold of ion/atom ratio of the IBAD process which is required for cBN formation to a higher value. In order to understand the different behaviors of the Ti and Al incorporations, the chemical states of the Ti and Al additions in the BN composite films were examined by X-ray photoelectron spectroscopy (XPS), indicating preferential formation of TiB2 and AlN, respectively.
Keywords: Composites, cubic boron nitride, ion beam assisted deposition
  • Diamond and Related Materials 8 (1999) 386-90

Publ.-Id: 2030 - Permalink


Improvement of the Oxidation Resistance of gamma Titanium Aluminides by Microalloying with Chlorine using Ion Implantation
Schumacher, G.; Lang, C.; Schütze, M.; Hornauer, U.; Richter, E.; Wieser, E.; Möller, W.;
High oxidation resistance of gamma titanium aluminides can be achieved by the formation of a continuous scale of slowly growing Al2O3. The formation of such a scale was stimulated by the addition of small amounts of chlorine. The additions were incorporated by ion implantation into the sample. The g-TiAl samples were oxidized at 1173 K in air for 100 h. Even if chlorine is present in very small quantities, it has a highly beneficial effect on the oxidation resistance (microalloying effect). The kinetics are changed from mixed TiO2/Al2O3- kinetics for unimplanted specimens to pure Al2O3- kinetics for chlorine implanted specimens.
  • Materials and Corrosion 50, 162-165 (1999)

Publ.-Id: 2029 - Permalink


Protection of gamma-based TiAl against High Temperature Oxidation using Ion Implantation of chlorine
Hornauer, U.; Günzel, R.; Reuther, H.; Richter, E.; Wieser, E.; Möller, W.; Schumacher, G.; Dettenwanger, F.; Schütze, M.;
The effect of ion beam implantation and plasma immersion ion implantation of chlorine on the high temperature oxidation of titanium aluminides above 800 °C in air was investigated. Thermogravimetric oxidation tests (TGA) were performed to examine the long term protection. Depth profiling with Auger electron spectroscopy (AES) was used to investigate Cl diffusion and oxide formation during the first stage of oxidation. A microscopic model of the chlorine effect will be discussed. A systematic variation of the implantation energy and fluence shows that there is a narrow regime of the Cl concentration for optimum protective effect. The time to form a protective Al2O3 layer depends on the local Cl concentration. The oxidation rate after this incubation time is reduced by about 2 orders of magnitude compared to untreated Ti50Al and is nearly independent of the fluence. The implantation energy is not a sensitive parameter, because the implanted chlorine profile changes very quickly during high temperature oxidation.
Keywords: implantation, plasmaimmersion, TiAl, oxidation, chlorine
  • Surface and Coatings Technology 125 (2000) 89-93
  • Lecture (Conference)
    EMRS '99, Strasbourg

Publ.-Id: 2028 - Permalink


Microalloying effects in the oxidation of TiAl materials
Schumacher, G.; Dettenwanger, F.; Schütze, M.; Hornauer, U.; Richter, E.; Wieser, E.; Möller, W.;
The influence of microalloying on the oxidation behavior of gamma-TiAl based alloys was studied. The microalloying elements were added by ion implantation. Oxidation tests at 1173 K in air showed that the addition of chlorine into TiAl improves the oxidation resistance resulting in a decrease of the oxidation rate by about 2 orders of magnitude compared to unalloyed TiAl. Microstructural investigations revealed that the formation of an protective alumina layer on top of Cl-implanted TiAl is the cause for the decrease in the oxidation rate. AES measurements in the initial stage of oxidation showed that chlorine is located under the alumina layer in the metal phase. Thermodynamic calculations, investigations on the temperature dependence of the chlorine effect and the oxidation kinetics of preoxidized Cl-implanted samples support the model of a selective Al-transport via AlCl. Furthermore, the influence of small additions (in the ppm range) of P, B, C and Br on the oxidation kinetics of g-TiAl-based alloys has been investigated. P, B and C implanted TiAl showed a different oxidation behaviour and oxide scale microstructure compared to Cl and Br microalloyed TiAl. Especially the P implanted sample revealed an extensive nitride formation connected with a breakaway oxidation after 100 h.
  • Intermetallics Vol. 7 10 (1999) 1113-1120

Publ.-Id: 2027 - Permalink


Calculation of a Mixed Convection Flow Benchmark Using Different CFD Codes
Krepper, E.; Willschütz, H.-G.; Weiß, F.-P.;
New reactor designs comprise passive elements for decay heat removal. Computational-Fluid-Dynamics codes are an appropriate tool for the assessment of the efficiency of those components. Most of these codes are based either on the Finite-Volume or the Finite-Element method. Because of the importance for reactor safety these numerical tools have to be thoroughly validated using results from experimental setups.
The governing mechanism in passive components for decay heat removal is natural convection and heat transfer with internal heating. To assess the capability describing mixed convection flow, post test calculations of an IAHR benchmark exercise were performed (Kamide et. al, 1991). The commercial codes CFX-4® and ANSYS/FLOTRAN® were used, representing the Finite-Volume Method and the Finite-Element Method respectively.
This paper presents a discussion of the problems and capabilities of each code to calculate complex flow regimes and temperature fields.
  • Lecture (Conference)
    Jahrestagung Kerntechnik '99, Tagungsbericht S. 135-138, Karlsruhe 18.-20. Mai 1999
  • Contribution to proceedings
    Jahrestagung Kerntechnik '99, Tagungsbericht S. 135-138, Karlsruhe 18.-20. Mai 1999

Publ.-Id: 2024 - Permalink


First application of the metallotricarbonyl concept to design CNS receptor imaging agents based on Technetium-99m
Johannsen, B.; Pietzsch, H.-J.; Reisgys, M.; Hoepping, A.; Scheunemann, M.; Spies, H.; Brust, P.; Schibli, R.; Schubiger, P. A.; Alberto, R.;
There has been considerable interest in the development of technetium-99m radiopharmaceuticals for imaging CNS receptors.
Apart from [99mTc]TRODAT-1 for the dopamine transporter (1), the strategies applied so far for specific CNS radiotracers failed in the ultimate goal of providing imaging agents. Both in the integrated approach with the chelate meant to be part of the pharmacophore and the pendant approach simply attaching the chelate moiety to highly potent antagonists, the chelate unit often proved to be more crucial than initially anticipated. Although the currently available chelate units make it possible to alter and adjust overall properties such as size, shape, charge, polarity (oxo, dioxo, oxo-free) and lipophilicity, insufficient receptor affinity or negligible initial brain uptake remain an unsolved problem. The introduction of the small organometallic "Tc(CO)3" moiety into the design of 99mTc radiopharmaceuticals (2-4) considerably extend the versatility in designing new technetium or analogous rhenium complexes. The low-pressure synthesis of a Tc-carbonyl precursor as inaugurated by Alberto et al. (2) allows a convenient exploitation of the potential of the "Tc(CO)3" moiety in radiotracer design. We became particularly interested in studying the suitability of the new building block for the synthesis of Tc and Re based receptor-binding agents. Based on earlier work on thioether ligands (5) we have chosen a bidentate thioether group to link the Tc(I) tricarbonyl center with a receptor-ligand moiety. In a previous work, we applied this concept already to a steroid (6). Alternatively, a bidentate N-donor anchor group has been considered well suitable for combining the Tc(I) tricarbonyl center with the antagonist moiety.
Here we report the synthesis and in vitro receptor affinity of three candidates (Fig. 1) for the 5-HT1A receptor, 5-HT2A receptor, and dopamine transporter, respectively, in order to demonstrate the suitability of the concept.
Keywords: Tc-99m, CNS receptor ligands, chelate unit, Tc carbonyl complexes
  • Poster
    13. Intern. Symposium on Radiopharmaceutical Chemistry, Saint Louis, USA 1999 Konferenzbericht
  • Abstract in refereed journal
    J. Labelled Comp. Radiopharm. 42 (1) (1999) S48-S50

Publ.-Id: 2023 - Permalink


Synthesis and Autoradiographic Evaluation of a Novel High-Affinity Tc-99m Ligand for the 5-HT2A Receptor
Pietzsch, H.-J.; Scheunemann, M.; Kretzschmar, M.; Elz, S.; Pertz, H. H.; Seifert, S.; Brust, P.; Spies, H.; Syhre, R.; Johannsen, B.;
The successful development of [99mTc]TRODAT as ligand for the dopamine transporter has shown the feasibility to image specific transporters in the brain with radiotracers based on Tc-99m (1). In contrast to this achievement and despite the efforts many groups have devoted so far, the search for Tc-99m complexes with affinity to post-synaptic CNS receptors have not yet reached the same stage of development (2). As one of the consequences for the design of serotonin-5-HT2A receptor binding Tc-99m complexes an affinity of < 1nM is believed to be a prerequisite for further progress. Aiming at such a high affinity, we have pursued our design concept starting from ketanserin as lead structure for 5-HT2A receptor binding ligands (3, 4).
Here we report on the synthesis of a new high-affinity Tc-99m ligand that meets the requirement of picomolar affinity. The complex is evaluated in various receptor binding assays and by in vitro autoradiography.

Keywords: Serotonin-5-HT2A receptor, Tc-99m receptor ligand, ketanserin analogue, ligand synthesis, in vitro autoradiography, receptor binding assay
  • Poster
    13. Intern. Symposium on Radiopharmaceutical Chemistry, Saint Louis, USA 1999
  • Abstract in refereed journal
    J. Labelled Cpd. Radiopharm. 42 (1999) S345-S347

Publ.-Id: 2022 - Permalink


Investigations on Pressure Relief at Forschungszentrum Rossendorf
Lucas, D.;
The most important activities of the Institute of Safety Research regarding to the development sensors two-phase flow measurement and pressure relief are presented. A new developed electrode-mesh sensor allows a very fast (1024 frames per second) tomographic measurement of the void or gas fraction. The sensor is used e.g. for investigations on the transition between flow regimes. For the transient simulation of pressure relief the BLDN code and the BRICK code are available. The BRICK code bases on a new Particle-In-Cell (PIC) transport model, which avoids numerical diffusion. This is advantageous in case of the consideration of generation and decay of foam. A special interface allows to include a foam model. Investigations on the influence of short living foams on the pressure relief process are presented as well as investigations on pulsations of the mass flow rate, which may occur during the blowdown process under certain conditions.
  • Lecture (Conference)
    Presentation at the DIERS User Group meeting, Las Vegas, NV, April 14-16, 1999

Publ.-Id: 2021 - Permalink


Erste Nachrechnungen von Druckentlastungsexperimenten bei durchgehender Reaktion mit dem Programm BRICK
Lucas, D.;
Die Nachrechnungen von Druckentlastungsexperimenten bei durchgehender Reaktion dienen Validierung des Computerprogramms BRICK. Dafür stehen experimentelle Daten der Inburex GmbH Hamm (Kalorimeterversuche), des Wilhelm-Jost-Instituts Hamm (Entlastung eines 280 l Reaktors) sowie eigene kleinmaßstäbliche Experimente (Entlastung eines 1,95 l Reaktors) zur Verfügung. Als Reaktionssysteme wurden die Methanol/Essigsäureanhydridveresterung (verdampfendes System), die Ammoniumperoxodisulfatzersetzung (gasbildendes System) und Wasserstoffperoxidzersetzung (sowohl gasbildend als auch verdampfend) genutzt. Die Übereinstimmung zwischen den Rechnungen und den experimentellen Daten ist gut. Einen wesentlichen Unsicherheitsfaktor stellen die Wärmeströme über die Behälterwand vor. Daher sollten insbesondere die Korrelationen für die Wärmeübergänge sowohl für die Behälterinnenwand als auch an der Außenwand erweitert und ergänzt werden.
  • Lecture (Conference)
    47. Sitzung des DECHEMA/GVC-Arbeitsausschuß "Sicherheitsgerechtes Auslegen von Chemieapparaten", Frankfurt am Main, 9./10. März 1999

Publ.-Id: 2020 - Permalink


BRICK - ein Simulationstool für Mehrphasenströmungen in einem Behälter auf der Basis einer Partikelmethode
Lucas, D.;
Das Programm BRICK beruht auf einer neuen Lösungsmethode für die Modellierung
von Transportvorgängen in Behältern. Die Grundgedanken der Methode, welche zur Klasse der Particle-In-Cell (PIC) Methoden gehört, werden vorgestellt.

  • Lecture (Conference)
    Statement auf dem GVC-Expertengespräch "Computational Fluid Dynamics", Düsseldorf, 3. September 1998

Publ.-Id: 2019 - Permalink


Dynamische Simulation von Druckentlastungsvorgängen mit dem Programm BRICK
Lucas, D.;
Das Programm BRICK gestattet die Berechnung des zeitlichen Verlaufs wichtiger Größen (Druck, Temperatur, Massenaustrag) bei der Druckentlastung chemischer Reaktoren auf Grundlage einer Particle-In-Cell (PIC) Methode. Die wichtigsten Einzelmodelle des Programms werden erläutert. Beispiele zur Validierung werden diskutiert.
  • Lecture (Conference)
    45. Sitzung des DECHEMA/GVC-Arbeitsausschuß "Sicherheitsgerechtes Auslegen von Chemieapparaten", Frankfurt am Main, 21./22. April 1998

Publ.-Id: 2018 - Permalink


Massenstromschwankungen bei der Druckentlastung von Reaktoren
Lucas, D.; Prasser, H.-M.;
  • Lecture (Conference)
    42. Sitzung des DECHEMA/GVC-Arbeitsausschuß "Sicherheitsgerechtes Auslegen von Chemieapparaten", Forschungszentrum Rossendorf, 15-16. Oktober 1996

Publ.-Id: 2017 - Permalink


Simulation des transienten Verhaltens mehrphasiger Strömungsfelder in einem Blow-Down System
Mewes, D.; Brodhagen, A.; Prasser, H.-M.; Lucas, D.;
  • Poster
    zum Schwerpunkt-Kolloquium der Volkswagenstiftung zur "Modellierung komplexer Systeme in der Verfahrenstechnik", Aachen, 22.-23. Februar 1996

Publ.-Id: 2016 - Permalink


Untersuchungen zu möglichen Ursachen von Schwingungen des Massenstroms an der Entlastungsarmatur bei Druckentlastungsvorgängen
Lucas, D.; Prasser, H.-M.;
  • Lecture (Conference)
    am Institut für Verfahrenstechnik der Universität Hannover, 30.1.1996

Publ.-Id: 2015 - Permalink


Schnelle Gittersensoren für Gasgehalt, Gasgeschwindigkeit und Volumenstrom in einer Zweiphasenströmung
Prasser, H.-M.;
Im Forschungszentrum Rossendorf wurde ein Gittersensor entwickelt, der die Ermittlung von momentanen Gasverteilungen mit einer örtlichen Auflösung von ca. 3 mm bei einer Meßfolge von derzeit 1200 Hz erlaubt. Er basiert auf der Messung der momentanen örtlichen elektrischen Leitfähigkeit des Zweiphasengemischs. Mit dem Sensor wurde eine Luft-Wasser-Strömung in einer vertikalen Rohleitung in weiten Bereichen der Leerrohrgeschwindigkeiten visualisiert und Voidanteile gemessen. Durch die gute Auflösung des Sensors werden Gasblasen in mehreren, zeitlich aufeinanderfolgenden Verteilungen abgebildet, was die Untersuchung von Blasengrößenverteilungen und deren Evolution entlang des Strömungsweges ermöglicht. Mit zwei hintereinander angeordneten Sensoren wurden durch Anwendung der Kreuzkorrelation Profile der Gasgeschwindigkeit gemessen.
Keywords: two-phase flow, measurement methods, wire-mesh sensor, vertical pipe flow, flow pattern, gas fraction, gas velocity
  • Lecture (Conference)
    Seminarvortrag Universität GH Essen, 06. Mai 1999

Publ.-Id: 2014 - Permalink


Meßtechniken in der Zweiphasenströmung
Prasser, H.-M.;
Im Forschungszentrum Rossendorf wurde ein Gittersensor entwickelt, der die Ermittlung von momentanen Gasverteilungen mit einer örtlichen Auflösung von ca. 3 mm bei einer Meßfolge von derzeit 1200 Hz erlaubt. Er basiert auf der Messung der momentanen örtlichen elektrischen Leitfähigkeit des Zweiphasengemischs. Mit dem Sensor wurde eine Luft-Wasser-Strömung in einer vertikalen Rohleitung in weiten Bereichen der Leerrohrgeschwindigkeiten visualisiert und Voidanteile gemessen. Durch die gute Auflösung des Sensors werden Gasblasen in mehreren, zeitlich aufeinanderfolgenden Verteilungen abgebildet, was die Untersuchung von Blasengrößenverteilungen und deren Evolution entlang des Strömungsweges ermöglicht. Mit zwei hintereinander angeordneten Sensoren wurden durch Anwendung der Kreuzkorrelation Profile der Gasgeschwindigkeit gemessen.

Keywords: two-phase flow, measurement methods, wire-mesh sensors, flow patterns, vertical pipe flow
  • Lecture (Conference)
    Vortrag am IKE des Forschungszentrums Karlsruhe am 04.05.1999

Publ.-Id: 2013 - Permalink


Die Verknüpfung von Teilmodellen auf der Grundlage der Dimensionsanalyse
Hoppe, D.;
Für den Zweck der Modellbildung wird es im Beitrag als einfacher angesehen, erst Teilmodelle des zu beschreibenden Objektes zu erzeugen und diese nachher zu einer gesamtheitlichen Struktur miteinander zu verknüpfen, als das Objekt unmittel bar in seiner Gesamtheit zu modellieren. Aus dieser Sicht wird untersucht, wie die Verknüpfung von vorgegebenen Teilmodellen auf systematische Weise mit Hilfe der sogenannten Dimensionsanalyse durchgeführt werden kann. Das Strukturierungs problem wird dabei auf das Lösen eines linearen algebraische Gleichungssystems zurückgeführt. Strukturelle Restriktionen werden entweder durch eine geeignete Problemformulierung oder dadurch berücksichtigt, daß der formal gefundene Lö sungsraum nachträglich eingeschränkt wird. Anwendungsmöglichkeiten dieses Kon zeptes werden an verschiedenartigen Beispielen gezeigt.

Keywords:
  • Open Access LogoWissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-263 Juni 1999

Downloads:

Publ.-Id: 2012 - Permalink


Experimental and Numerical Investigation of One and Two-Phase Natural Convection in Storage Tanks
Aszodi, A.; Krepper, E.; 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. Several tests were performed both with heating from the bottom and with heating from the side walls. In recent tests in addition to thermocouples, the tank was equipped with needle probes for measuring of the local void fraction. The paper presents experimental and numerical investigations of single and two phase heating up processes of tanks with side wall heating. The measurement of the temperature and of the void fraction makes interesting phenomena evident. which could be explained by an own 2D model. The gained experimental results may be used for the validation of boiling models in 3-D CFD codes.
Keywords: heating up, large pools, natural circulation, boiling, experiments, two-phase flow measurements, cfd-simulation
  • Lecture (Conference)
    EUROTHERM Seminar No. 63, Single and Two- Phase Natural Circulation, Genoa September 1999, Proceedings edited by M. Misale and F. Mayinger, pp. 43-49, ISBN 88-900433-1-8
  • Contribution to proceedings
    EUROTHERM Seminar No. 63, Single and Two- Phase Natural Circulation, Genoa September 1999, Proceedings edited by M. Misale and F. Mayinger, pp. 43-49, ISBN 88-900433-1-8

Publ.-Id: 2011 - Permalink


Simulation of a Buoyancy Influenced Forced Fluid Flow Using a Finite Volume and a Finite Element Code
Krepper, E.; Willschütz, H.-G.; Weiß, F.-P.;
New reactor designs comprise passive elements for decay heat removal. Computational-Fluid-Dynamics codes are an appropriate tool for the assessment of the efficiency of those components. Most of these codes are based either on the Finite-Volume or the Finite-Element method. Because of the importance for reactor safety these numerical tools have to be thoroughly validated using results from experimental setups.
The governing mechanism in passive components for decay heat removal is natural convection and heat transfer with internal heating. To assess the capability describing mixed convection flow, post test calculations of an IAHR benchmark exercise were performed. The commercial codes CFX-4® and ANSYS/FLOTRAN® were used, representing the Finite-Volume Method and the Finite-Element Method respectively.
This paper presents a discussion of the problems and capabilities of each code to calculate complex flow regimes and temperature fields.
Keywords: mixed convection flow, cfd-code simulation, CFX-4.2, ANSYS/FLOTRAN
  • Lecture (Conference)
    Eurotherm Seminar No. 63: Single and Two-Phase Natural Circulation, Genua, 6.-8.9.1999, Proceedings edited by M. Misale and F. Mayinger, pp. 137-143, ISBN 88-900433-1-8
  • Contribution to proceedings
    Eurotherm Seminar No. 63: Single and Two-Phase Natural Circulation, Genua, 6.-8.9.1999, Proceedings edited by M. Misale and F. Mayinger, pp. 137-143, ISBN 88-900433-1-8

Publ.-Id: 2010 - Permalink


Numerical Simulation of the Coolant Mixing in pressurized water reactors
Höhne, T.;

The behavior of PWRs during cold water or boron dilution transients is strongly influenced by the distribution of coolant
temperature and boron concentration at the core inlet. This distribution is the needed input to 3-dimensional neutron kinetics to
calculate the power distribution in the core. It mainly depends on how the plugs of cold or unborated water formed in a single loop
are mixed in the downcomer and in the lower plenum.

To simulate such mixture phenomena requires the application of 3-dimensional CFD (computational fluid dynamics) codes. The
calculations are based on the CFD Code CFX-4. The results of the simulation have to be validated against mixture experiments at
scaled facilities.

Therefore, in the framework of a research project funded by BMBF, the institute created a 1:5 mixture facility representing first the
geometry of a German pressurized water reactor and later the European Pressurized Water Reactor (EPR) geometry.
  • Lecture (Conference)
    Jahrestagung Kerntechnik, Mai 18-21 1999, Karlsruhe, S. 139
  • Contribution to proceedings
    Jahrestagung Kerntechnik, Mai 18-21 1999, Karlsruhe, S. 139

Publ.-Id: 2009 - Permalink


Measurements and CFX-Simulations of a Bubbly Flow in a Vertical Pipe
Krepper, E.; Prasser, H.-M.;
In the Forschungszentrum Rossendorf a measurements techniques test loop was constructed. Air water flow in a vertical tube was investigated using different two phase flow measuring techniques. The paper describes the used measuring techniques and some performed experiments. The code CFX-4.2 with its implemented two phase models was used, to simulate bubbly flow and to compare calculated void profiles with the measured results.
Keywords: bubble flow, two-phase flow measurement techniques, cfd simulations
  • Lecture (Conference)
    CFX International Users Conference, Friedrichshafen, 21.-24.6.1999 (Conference-CD)
  • Contribution to proceedings
    CFX International Users Conference, Friedrichshafen, 21.-24.6.1999 (Conference-CD)

Publ.-Id: 2008 - Permalink


NUMERICAL SIMULATION OF THE COOLANT FLOW IN PRESSURIZED WATER REACTORS
Höhne, T.;
The behavior of PWRs during cold water or boron dilution transients is strongly influenced by the distribution of coolant temperature and boron concentration at the core inlet. This distribution is required as an input to 3-dimensional neutron kinetics to calculate the power distribution in the core. It mainly depends on how the plugs of cold or unborated water formed in a single loop are mixed in the downcomer and in the lower plenum [1]. The reactivity insertion due to penetration of unborated coolant into the core depends on the degree of mixing. Weak mixing can result in recriticality and possibly in significant power release. The same is true for cold water insertion into the core due to overcooling of a coolant loop in the case of a steam line break. Coolant mixing is also of interest under steady state normal operation conditions. Slight differences in the cold leg temperatures can occur due to small asymmetries in the primary circuit loops.

To simulate such mixture phenomena requires the application of 3-dimensional CFD (computational fluid dynamics) codes. The results of the simulation have to be validated against mixing experiments at scaled facilities. The calculations are accomplished using the CFD Code CFX-4.2 [2].

As a first step, steady state mixing conditions in the downcomer and lower plenum are considered. Qualitatively different flow fields were found in different reactor types depending from the downcomer geometry. Calculated results were compared with experiments.
  • Lecture (Conference)
    CFX International Users Conference, Friedrichshafen, Germany 19-24 June 1999, CD-ROM, No. 27
  • Contribution to proceedings
    CFX International Users Conference, Friedrichshafen, Germany 19-24 June 1999, CD-ROM, No. 27

Publ.-Id: 2007 - Permalink


Entwicklung eines iterativen 3D Rekonstruktionverfahrens für die Kontrolle der Tumorbehandlung mit Schwerionen mittels der Positronen-Emissions-Tomographie
Lauckner, K.;
At the Gesellschaft für Schwerionenforschung in Darmstadt a therapy unit for heavy ion cancer treatment has been established in collaboration with the Deutsches Krebsforschungszentrum Heidelberg, the Radiologische Universitätsklinik Heidelberg and the Forschungszentrum Rossendorf.

For quality assurance the dual-head positron camera BASTEI (Beta Activity meaSurements at the Therapy with Energetic Ions) has been integrated into this facility. It measures ß+-activity distributions generated via nuclear fragmentation reactions within the target volume.
BASTEI has about 4 million coincidence channels. The emission data are acquired in a 3D regime and stored in a list mode data format. Typically counting statstics is two to three orders of magnitude lower than those of typical PET-scans in nuclear medicine.

Two iterative 3D reconstruction algorithms based on ISRA (Image Space Reconstruction Algorithm) and MLEM (Maximum Likelihood Expectation Maximization), respectively, have been adapted to this imaging geometry. The major advantage of the developed approaches are run-time Monte-Carlo simulations which are used to calculate the transition matrix.
The influences of detector sensitivity variations, randoms, activity from outside of the field of view and attenuation are corrected for the individual coincidence channels.

Performance studies show, that the implementation based on MLEM is the algorithm of merit. Since 1997 it has been applied sucessfully to patient data. The localization of distal and lateral gradients of the ß+-activity distribution is guaranteed in the longitudinal sections. Out of the longitudinal sections the lateral gradients of the ß+-activity distribution should be interpreted using a priori knowledge.
Keywords: positron emission tomography, 3D reconstruction algorithm, heavy ion tumour therapy
  • Open Access LogoWissenschaftlich-Technische Berichte / Forschungszentrum Rossendorf; FZR-264 Juni 1999

Downloads:

Publ.-Id: 2005 - Permalink


Dependence of the Ratio between Magnetic and Nuclear Small Angle Neutron Scattering on the Size of the Heterogeneities
Große, M.; Gokhman, A.; Böhmert, J.;
The ratio between magnetic and nuclear small angle neutron scattering (SANS) can provide additional information about the composition and structure of the scattering inhomogenities. The method fails if the material system does not meet the two-phase approach. In this case, by using the indirect transformation method, the ratio can more generally be defined and related to the dependence of the scattering particle size. The method is derived and applied to model systems with two types of non-magnetic spheric inhomogenities in a ferromagnetic matrix.
Keywords: Analysis of materials, Neutron scattering, radiation damage, reactor pressure vessel steel
  • Nuclear Instruments and Methods in Physics Research B 160 (2000) 515-520

Publ.-Id: 2004 - Permalink


Electron emission characteristics of solidified gold alloy liquid metal ion sources
Knapp, W.; Bischoff, L.; Teichert, J.;
Solidified liquid metal ion sources (LMISs) operating with Au alloy wetted hair-pin emitters can be used as high-intensity electron point sources for application in the field of ultrahigh vacuum techniques. A nanotip emitter on a solidified LMIS emitter can be formed by quenching during ion emission mode. I - V characteristics and the performance of the electron emitting LMIS are presented.
Keywords: electron source, field emitter, solidified liquid metal ion source, nanotip emitter
  • Contribution to external collection
    Applied Surface Science 146 (1999) 134 -137
  • Lecture (Conference)
    2nd Int. Vacuum Electron Source Conf., Tsukuba, Japan, July 7 - 10, 1998

Publ.-Id: 2003 - Permalink


Reconstitution Techniques Qualification & Evaluation to Study Ageing Phenomena of Nuclear Pressure Vessel Materials - Resque,
van Walle, E.; Valo, M.; Viehrig, H.-W.; Gage, G.; Wootton, M.; Keim, E.; Debarberis, L.; Horsten, M.;
  • Other report
    Contract FI4SCT960038, Yearly Progress Report 1997, European Commission, Euratom Research Framework Programme 1994-1998 "Nuclear Fission Safety", June 1998, AGE-Resque(98)-P003

Publ.-Id: 2002 - Permalink


Collection and Review of VVER Transient Measurement Data
Kyrki-Rajamäki, R.; Kliem, S.; Mittag, S.;
Technical Reports on VVER transients were provided by IVO, NRI, KI, STCNRS and INRNE. The present report gives a survey of the transients documented by the five organisations mentioned. The main actions and effects observed during each transient are briefly described. An overview of the information contained in the five Technical Reports is provided in tabular form. The tables comprise information on the initial states, the measured parameters, and the time regime of the measurement. For each reactor type, VVER­440 and VVER­1000, respectively, one transient is recommended for coupled codes validation in the current project.
  • Open Access LogoTechnical Report on CEC PHARE project SRR1-95, Forschungszentrum Rossendorf; 1998

Publ.-Id: 2000 - Permalink


SANS-Investigation of the Irradiation-Induced Changes in Reactor Pressure Vessel Steels
Große, M.; Ulbricht, A.;
  • Other report
    Rapport de Experience 1998, LLB Saclay

Publ.-Id: 1998 - Permalink


Marangoni-Konvektion in einer seitlich beheizten ebenen Flüssigmetallschicht unter dem Einfluß eines Magnetfeldes
Gerbeth, G.;
  • Other report
    Schlussbericht, Juli 1998

Publ.-Id: 1997 - Permalink


Magnetohydrodynamic flow around bluff bodies
Gerbeth, G.; Alemany, A.; Shatrov, V.; Krasilnikov, E.;
  • Other report
    Final Report: Januar 1995 - Dezember 1997, Dresden, September 1998, Reference number: INTA

Publ.-Id: 1995 - Permalink


Laboratory Experiments on Dynamo Action
Stefani, F.; Gerbeth, G.; Gailitis, A.; Lielausis, O.;
Despite the great success of dynamo theory during the last decades an experimental verification of magnetic field self-excitation in conducting fluids is still missing. We summarize the outcomes of a workshop held in Riga in June 1998 on various experimental approaches to this topic. The Riga dynamo
experiment is presented in more detail.

  • Lecture (Conference)
    SIAM Annual Meeting, University of Toronto (Canada), 13.-17. July 1998

Publ.-Id: 1994 - Permalink


Numerical Simulation of the Riga Dynamo Experiment
Stefani, F.; Gerbeth, G.; Gailitis, A.;
We present numerical simulations for the Riga dynamo experiment, which is intended
to verify the magnetic field self-excitation in a helical flow of a conducting fluid.
Testing a wide variety of axial and azimuthal velocity profiles we show the importance
of the global helicity for the efficiency of the dynamo. Predictions are made on
the shape of the arising magnetic field and the back-reaction of the
Lorentz force on the flow.
  • Lecture (Conference)
    SIAM Annual Meeting, University of Toronto (Canada), July 13-17, 1998

Publ.-Id: 1993 - Permalink


Numerical Simulation for the Riga Dynamo
Stefani, F.; Gerbeth, G.; Gailitis, A.;
The critical magnetic Reynolds number (Rm) of the Riga dynamo experiment depends
strongly on the shape of its velocity profiles. For given motor power ressources it is
necessary to optimize these profiles in order to achieve self-excitation of the magnetic
field. We present a number of one- and two-dimensional calculations for a variety of
axial and azimuthal velocities. Particularly, we test velocity profiles with maximal
helicity (Bessel function profile). For these velocity profiles the critical Rm can
be reduced by 20 per cent compared to the value for the solid body rotation profile.
The used two-dimensional finite difference solver allows to study the effect of
axially varying profiles, too. In addition, we present some two-dimensional
calculations for further dynamo experiments in cylindrical geometry, including
the flow topologies s1t1, s2t1 and s2t2. The influence of the flow direction and
the effect of a surrounding conducting medium on the critical Rm is investigated
in detail.
  • Lecture (Conference)
    Workshop "Laboratory Experiments on Dynamo Action", Jurmala (Latvia), June 13-16, 1998

Publ.-Id: 1992 - Permalink


Bluff body wake control by magnetic fields
Mutschke, G.; Gerbeth, G.; Shatrov, V.;
We present numerical results on the control of 2-D and 3-D instabilities in the wake of a circular cylinder by means of externally applied magnetic fields. 2-D instability (vortex shedding) can clearly be suppressed with increasing field strength. However, 3-D instability is influenced in a nonmonotonic way, triggered by changes to the 2-D flow. 3-D instability can exist below the 2-D stability threshold, which may lead to a reversal of the order of instabilities for fixed field strength. Strong fields seem to amplify 3-D instability.
  • Lecture (Conference)
    SIAM Annual Meeting, University of Toronto (Canada), July 13-17, 1998

Publ.-Id: 1991 - Permalink


Natural circulation experiments at the ISB-VVER Integral Test Facility and Calculations using the Code ATHLET
Krepper, E.;
In 1995 at the integral test facility ISB-VVER in Elektrogorsk near Moscow natural circulation experiments were performed, which were scientifically accompanied by the Forschungszentrum Rossendorf. These experiments were the first of this kind at a test facility, which models VVER-1000 thermalhydraulics. Using the code ATHLET which is being developed by "Gesellschaft für Anlagen- und Reaktorsicherheit", pre- and posttest calculations were done to determine the thermalhydraulic events to be expected and to define and tune the boundary conditions of the test. The conditions found for natural circulation instabilities and cold leg loop seal clearing could be confirmed by the tests. Besides the thermalhydraulic standard measuring system, the facility was equipped with needle shaped conductivity probes for measuring the local void fractions.
  • Poster
    Int. Conference "TOPSAFE", Valencia (Spain), 1998
  • Contribution to proceedings
    Int. Conference "TOPSAFE", Valencia (Spain), 1998

Publ.-Id: 1990 - Permalink


OECD PWR MSLB Benchmark - Dependence of the Results from Several Parameters
Kliem, S.;
The OECD has defined a benchmark for coupled Cartesian neutron kinetics/thermohydraulics code systems. In the first phase, a plant simulation with point kinetics was requested. The purpose was to test the model response.
In this presentation, the dependence of the results obtained by means of the ATHLET-code from several important parameters is investigated. It was found, that the nodalization of the steamline in the vicinity of the break has an influence on the pressure behaviour and on the time of the return-to-power.
  • Lecture (Conference)
    2nd PWR MSLB Workshop CIEMAT, Madrid (Spain), June 22-23, 1998

Publ.-Id: 1989 - Permalink


Fifth Dynamic AER Benchmark - A Benchmark for Coupled Thermohydraulic System/3D Hexagonal Neutron Kinetic Core Models - Comparison of Results - Level 1
Kliem, S.;
The fifth dynamic benchmark was defined at the 7th AER-Symposium, held in Hörnitz, Germany in 1997. It is the first benchmark for coupled thermohydraulic system/three-dimensional hexagonal neutron kinetic core models. In this benchmark the interaction between the components of a VVER-440 NPP with the reactor core has been investigated. In this presentation, the first results obtained by means of the codes DYN3D/ATHLET (Forschungszentrum Rossendorf), BIPR8/ATHLET (Kurchatov Institute Moscow) und HEXTRAN/SMABRE (VTT Energy Espoo) were compared. Both thermohydraulics and neutron kinetics parameters show dif-
ferences.
  • Lecture (Conference)
    AER Working Group D Meeting, Rez (Czech Republic), May 18-20, 1998

Publ.-Id: 1988 - Permalink


Quantifizierung der hydrodynamischen Parameter in kurzlebigen Schäumen
Kern, T.;
  • Lecture (Conference)
    4. Fachtagung "Anlagen-, Arbeits- und Umweltsicherheit", Köthen, 5./6. November 1998

Publ.-Id: 1987 - Permalink


HEXNEM2 - a New Nodal Method for Hexagonal Geometry
Grundmann, U.; Hollstein, F.;
A new nodal method HEXNEM2 for hexagonal geometry is described. The method is based on a two-dimensional expansion of
the intranodal fluxes. Polynomials up to the second order and exponential functions are used in each group. By this method the singular
terms occurring in the transverse integration methods are avoided. Side averaged and corner point values of fluxes and currents are used
for the coupling of nodes. A calculation scheme for the outgoing partial currents at the sides and similar expressions for the corners from
given incoming values are used in the inner iteration which gives a fast running scheme. The method is tested against 2-dimensional
hexagonal benchmark problems for the VVER-type reactors. The results show that the multiplication factor and nodal powers are predicted
accurately. A considerable improvement can be shown of the results for the VVER-1000 benchmarks compared with the method developed
previously for the code DYN3D and the simpler method HEXNEM1.
  • Lecture (Conference)
    presented at the AER Working Group D Meeting, Rez (Czech Republic), May 18-20, 1998

Publ.-Id: 1986 - Permalink


Type and Annealing Behaviour of Irradiation Defects in Surveillance Materials of the VVER-type Weld Metal Sv-10KhMFT
Große, M.;
  • Lecture (Conference)
    Table Ronde LLB, Saclay (Frankreich), Nov.1998

Publ.-Id: 1985 - Permalink


Influence of magnetic fields on surface driven flows
Gerbeth, G.;
A summary of magnetic field effects on surface driven flows will be given. Own work in the fields
- hydrothermal waves controlled by magnetic fields,
- Marangoni flows at liquid metal surfaces,
- thermoelectrically driven flows,
- levitated spheres and drops,
- Marangoni motion of drops
will be summarized. In addition, literature results about magnetic field influence on floating zone crystal growth or the use of magnetic fields in laser or electron beam welding bill be given. The second part of the lecture will concentrate on possible experiments with magnetic fields under microgravity. Proposals will be presented for discussion for crystal growth with magnetic fields, thermoelectricity, electromagnetic gas injectors, or magnetic field control of electrochemical processes. Emphasis will be put on the problem of diagnostics being inherent to all activities.
  • Lecture (Conference)
    Workshop "Applications of magnetic fields in materials processing under microgravity conditions", Erlangen, Nov. 11-12, 1998

Publ.-Id: 1984 - Permalink


Fundamentals of technical applications of MHD
Gerbeth, G.;
A summary of MHD effects and technical applications will be given based on a classification of the different actions of external magnetic fields and/or external electrical currents. An overview of the different alternating fields (rotating, pulsating, travelling) and static magnetic fields, and their interaction with liquid metal melts will be given. Special emphasis will be put on applications in crystal growth where a contactless melt flow control is important for the convective motions in many growth technologies. Typically steady magnetic fields are used to damp such flows. Surprisingly, active flow driving forces due to alternating magnetic fields can be of stabilizing character, too. Numerical results for the combined action of DC and AC magnetic fields will be presented for two problems: vertical Bridgeman and silicon Czochralski crystal growth. Recent results on MHD turbulence and some destabilizing actions of steady magnetic fields will shortly be mentioned. Special attention will be given to the problem of measuring techniques in liquid metal melts since this is a crucial question for any experimental activities in the field. For instance, any activity for code validation will require model experiments which, in turn, quickly lead to serious measuring problems. Some new results and ideas will be discussed.
  • Lecture (Conference)
    Workshop "The use of Magnetic Fields in Crystal Growth an Metals Casting" , Frankfurt a. M., 1.-2. April 1998

Publ.-Id: 1983 - Permalink


Einsatz von Magnetfeldern bei der Silizium-Czochalski-Kristallzüchtung
Gerbeth, G.; Galindo, V.;
Eine kontaktlose Beeinflussung der konvektiven Strömung in der Schmelze ist in vielen Kristallzüchtungstechnologien von großer Bedeutung. Gewöhnlich werden stationäre magnetische Felder benutzt, um solche Strömungen zu dämpfen. Überraschenderweise können auch aktive Strömungsantriebskräfte, die von instationären magnetischen Feldern erzeugt werden, von stabilisierendem Charakter sein. Wir stellen Resultate der numerischen Simulation der kombinierten Wirkung von homogenen und linearen stationären Magnetfeldern für die Silizium-Czochalski-Kristallzüchtung und von homogenen und rotierenden Magnetfeldern für die Bridgman-Anordnung vor. Es werden bei der Czochalski-Geometrie nicht nur die thermische Konvektion und die Rotation des Kristalls und des Tiegels in Betracht gezogen, sondern auch der Einfluß der antreibenden und/oder dämpfenden elektromagnetischen Kräfte sowie der Einfluß des induzierten elektrischen Stromes und der thermokapillar angetriebenen Strömungen an der freien deformierbaren Schmelzoberfläche. Aufgrund der hohen Reynolds-Zahl der Strömung ist die numerische Simulation laminar nicht mehr möglich. Es werden vergleichende Rechnungen mit einem Null-Gleichungs-Turbulenzmodell, das auf der Prandtl´schen Mischungsweg-Hypothese basiert, und einem anisotropen k-epsilon Turbulenzmodell durchgeführt.
  • Lecture (Conference)
    Berg und Hüttenmännischer Tag, TU Bergakademie Freiberg, 18.06.1998

Publ.-Id: 1982 - Permalink


Crystal Growth Melt Flow Control by Means of Magnetic Fields
Galindo, V.; Gerbeth, G.;
  • Lecture (Conference)
    Workshop SOLFIDAP, IKZ Berlin, Berlin-Adlershof , 25.-27. Mai 1998

Publ.-Id: 1981 - Permalink


Numerical studies on crystal growth melt flow control using different magnetic fields
Galindo, V.; Gerbeth, G.;
  • Lecture (Conference)
    SIAM Annual Meeting, University of Toronto (Canada), July 13-17, 1998

Publ.-Id: 1980 - Permalink


Separation Control Using Lorentz Forces: Recent Experimental and Numerical Results
Fey, U.; Weier, T.; Gerbeth, G.; Mutschke, G.; Gad-El-Hak, M.;
The flow around bodies moving in weakly electrically conducting fluids can be controlled by applying electromagnetic forces originating from electrodes and permanent magnets suitably placed on the surface of the body. Here we consider the
possibility of separation control for a two-dimensional bluff body and an inclined flat plate by inducing Lorentz forces parallel to the surface. We present physical and numerical experiments at diameter/chord Reynolds numbers in the range of 300--4,000 for the circular cylinder and 2,000--20,000 for the plate. Both steady and time-periodic forcing are applied. The physical experiments are conducted in an open channel with sodium hydroxide as the working fluid. Dramatic separation delays are observed on both bodies for a modest expenditure of energy. Special attention is drawn to lift enhancement due to separation delay for the inclined plate. Direct numerical simulations at low Reynolds numbers confirm the physical tendencies of the experiments.
  • Lecture at: American Physical Society, 51th Annual Meeting of the Division of Fluid Dynamics, Bulletin of the American Physical Society, Philadelphia, 22.-24.11.98

Publ.-Id: 1979 - Permalink


The effect of a superimposed steady magnetic field on nonstationary flow driven by a high frequency AC magnetic in an open cavity
Bojarevics, A.; Gelfgat, Y.; Gerbeth, G.; Cramer, A.;
  • Lecture (Conference)
    Workshop "The Use of Magnetic Fields in Crystal Growth and Metals Casting" Frankfurt a. M., 1.-2. April 1998

Publ.-Id: 1978 - Permalink


Some results on electromagnetic control of flow around bodies
Weier, T.; Gerbeth, G.; Mutschke, G.; Fey, U.; Posdziech, O.; Lielausis, E.; Platacis, E.;
The flow around bodies (cylinder, plate) can be controlled by applying electromagnetic forces originating from electrodes and permanent magnets suitably placed on the surface of the body. There is a large variety for applying those forces with respect to the geometrical arrangement and the electrical current feeding the electrodes. The goals of this approach are flow stabilization, drag reduction or manoeuvrability of the body in an electrically low-conducting fluid like seawater. We present experimental and numerical results for a low Reynolds-number range of 200 < Re < 4000. Experiments were performed using a copper sulphate electrolytic solution and a sodium hydroxide loop. Flows are considered around a cylinder and over a plate, with
Lorentz forces being parallel to the body surface. Experimental results will be presented for the body drag and the wake flow structures depending on different
regimes of electromagnetic forcing. In particular, we distinguish between the
regimes of direct, frequency-variable sinusoidal or pulsed electric currents. Numerical results confirm the physical tendencies at least for lower Reynolds numbers. Parameter ranges will be given for an optimal electromagnetic flow control in terms of drag reduction and flow laminarization. The energetic balance will be discussed.
  • Contribution to proceedings
    Proc. of the International Symposium on SEAWATER DRAG REDUCTION, pp. 395-400, Newport, Rhode Island (USA), 22.-24. Juli 1998

Publ.-Id: 1976 - Permalink


Specimen Reconstitution Technique and Verification Testing for Charpy Size SENB Specimens
Viehrig, H.-W.; Böhmert, J.;
Specimen reconstitution, i.e. the incorporation of a small piece from a previously tested specimen into a compound specimen, allows to multiply the number of tests. That is especially important if the available material is restricted and new parameters have to be measured. For this purpose a technique was developed to reconstitute Charpy size single-edge notch specimens (SENB) from broken halves of Charpy V-notch specimens. The essential tools for producing reconstituted specimens are a stud arc welding set-up and an electric wire discharge machine. The reconstitution technique applied is in accordance with the ASTM- guideline E-1253. The fraction of the insert that is affected by the reconstitution technique is determined by measurements of temperature and hardness gradients and by metallographic examination. The specimen reconstitution technique has been validated for SENB specimens of Charpy geometry. The test methods comprised instrumented impact testing of Charpy V specimens and elastic- plastic fracture toughness testing with precracked and side grooved SENB specimens.
  • Contribution to external collection
    Small Specimen Test Techniques, ASTM STP 1329, W.R. Corwin, S.T. Rosinski, E. van Walle, Eds., American Society for Testing and Materials, July 1998, pp. 420

Publ.-Id: 1975 - Permalink


Magnetohydrodynamik
Thess, A.; Gerbeth, G.;
Der Traum von magnetohydrodynamischen (MHD)-Generatoren und MHD-Schiffsantrieben hat sich nicht erfüllt. Die magnetisch gesteuerte Kernfusion läßt auf sich warten. Doch die Stille trügt:; MHD-Technologien halten erfolgreich Einzug in Metallurgie und Verfahrenstechnik, MHD-Experimente eröffnen neue Perspektiven für die nichtlineare Physik und Turbulenzforschung, und selbst das klassische Problem der Entstehung des Erdmagnetfeldes scheint seiner experimentellen Verifikation nahe zu sein.
  • Physikalische Blätter 54, S. 125, Februar 1998

Publ.-Id: 1974 - Permalink


Velocity Profile Optimization for the Riga Dynamo Experiment
Stefani, F.; Gerbeth, G.; Galitis, A.;
The Riga dynamo experiment is an attempt to show the
self-excitation of a magnetic field in an electrically conducting fluid.
Due to the absence of any scale separation effects, the precise shape of
the velocity profile has a strong influence on the values
of the critical magnetic Reynolds numbers (Rm).
Several numerical codes have been developed and used for the determination
of these critical Rm for arbitrary velocity profiles.
Helicity maximizing
profiles are shown to provide smaller critical Rm than the
solid body rotation flow. We outline how the velocity profiles
have been optimized in an iterative process including flow measurements,
constructive improvements and numerical calculations.
  • A. Alemany, Ph. Marty, .P. Thibault (ed.), Transfer Phenomena in Magnetohydrodynamic and Electroconducting Flows, Kluwer Academic Publishers, Dordrecht 1999, pp. 31-44

Publ.-Id: 1973 - Permalink


Results of Experimente at the NOKO Pilot Plant
Schaffrath, A.; Hicken, E. F.; Jaegers, H.; Prasser, H.-M.;
On the NOKO (emergency condenser) test station constructed at Jülich Research Centre, the operating performance and
effectiveness of the emergency condenser of the boiling water reactor 1000 have been determined in well over 200 tests. It has been
possible to check that the tests were in close agreement with a modified version of ATHLET
  • VGB-Power Tech 78 (1998), Nr. 5, S. 79-84

Publ.-Id: 1971 - Permalink


Experimental and numerical study of an anomalous thermocapillary convection in liquid gallium
Priede, J.; Cramer, A.; Gelfgat, Y.; Bar-Yuseph, P. Z.; Yari, A. L.; Gerbeth, G.;
Thermocapillary Marangoni convection of liquid gallium was studied experimentally and numerically. A specially designed experimental setup ensured an oxide-free surface of the liquid gallium for a very long time. The convective flow at the free surface was found to be directed opposite to both buoyancy-driven and ordinary thermocapillary convection. The anomalous direction of the thermocapillary flow was explained by the presence of a small amount of a surface-active contaminant - lead adsorbed at the free surface. Two different approaches were used to describe the observed phenomenon. First, the flow was treated as a pure thermocapillary convection with a modified dependence of the surface tension on temperature so that to reproduce the measured velocity distribution. Second, a novel physical model was devised for the flow driven by the gradient of the surface tension induced by the temperature dependence of the concentration of the adsorbed layer of contaminant. In contrast to the ordinary thermocapillary convection in low-Prandtl-number liquids, there is a strong coupling between the flow and the driving force in the proposed model resulting in velocity profiles very similar to those observed in the experiment.
  • Physics of Fluids, vol.11, 1998, pp. 3331-3339

Publ.-Id: 1969 - Permalink


Thioether ligands as anchor groups for coupling the "Tc(CO)3" moieties with biologically active molecules
Pietzsch, H.-J.; Reisgys, M.; Alberto, R.; Hoepping, A.; Scheunemann, M.; Seifert, S.; Wüst, F.; Spies, H.; Schubiger, P. A.; Johannsen, B.;
Neutral Re(I) carbonyl complexes with multidentate thioethers of the general formula [ReBr(CO)3(R-S(CH2)2S-R')] were obtained by ligand exchange reaction starting from [ReBr3(CO)3]2-. The thioether ligands bear functional groups (R, R'', such as the carboxyl, propargyl and hydroxyl moiety, which can act as anchor groups for biologically active molecules. First representatives of Re(I) and Tc(I) carbonyl thioether complexes, meant to target CNS neuroreceptors and hormone receptor-positive breast tumors, are described.
  • Book (Authorship)
    Technetium, Rhenium and Other Metals in Chemistry and Nuclear Medicine (Edited by Nicolini M., Mazzi U.) SGE Editoriali Padova (1999), pp. 313-316

Publ.-Id: 1968 - Permalink


Oscillatory and rotational instabilities in electromagnetic levitation
Priede, J.; Gerbeth, G.;
Two different instability mechanisms of electromagnetically levitated bodies are analyzed. The first is due to the virtual coupling between the electric current passing through the magnetic system and the variation of position of the body. This mechanism can result in unstable mass center oscillations of a levitated solid body. Another type of instabilities may occur because of the coupling beween the motion and the electric currents induced in the body. This effect can cause a spontaneous rotation of the body setting in as the frequency of the alternating magnetic field exceeds certain critaical threshold depending on the configuration of the field. This instability can be suppressed by an axial steady magnetic field of strength comparable to that of the levitating field.
  • Lecture (Conference)
    accepted at Symposium „Fluid-Flow Phenomena in Metals Processing“ TMS Annual Meeting, San Diego, USA, February 27 - March 5, 1999
  • Fluid Flow Phenomena in Metals Processing, Eds.: N.El-Kaddah, D.G.C.Robertson, S.T.Johansen, V.R.Voller, The Minerals, Metals & Materials Society, Warrendale (USA), 1999, pp.593-601

Publ.-Id: 1967 - Permalink


Hydrothermal wave instability of thermocapillary-driven convection in a transverse magnetic field
Priede, J.; Gerbeth, G.;
We study the linear stability of a thermocapilary-driven convection in a planar unbounded layer of an electrically conducting low-Prandtl-number liquid heated from the side and subjected to a transverse magnetic field. The thresholds of convective instability for both longitudional and oblique disturbances are calculated numerically and also asymptotically by considering the Hartmann and Prandtl numbers as large and small parameters, respectively. The magnetic field has a stabilizing effect on the flow with the critical temperature gradient for the transition from steady to oscillatory convection increasing as square of the the field strength. So increases also the critical frequency, while the critical wavelength reduces inversely with field strength. These asymptotics develop in a strong enough magnetic field when the instability is entirely due to the jet of the base flow confined in the Hartmann layer at the free surface. In contrast to the base flow, the critical disturbances, having a long wavelength at small Prandtl numbers, extend from the free surface into the bulk of the liquid layer over a distance exceeding the thickness of the Hartmann layer O(Pr-1/2) times. For Ha ? Pr-1/2 the instability is influenced by the actual depth of the layer. For such moderate magnetic fields the instability threshold is sensitive to the thermal properties of the bottom of the layer and the dependences of the critical parameters on the field strength are more complicated. In the latter case, there is a number of various instability modes possible depending on the thermal boundary conditions and the relative magnitudes of Prandtl and Hartmann numbers.
  • Journal of Fluid Mechanics (2000), vol. 404, pp. 211-250

Publ.-Id: 1966 - Permalink


Cylinder wake control by magnetics fields in liquid metal flows
Mutschke, G.; Shatrov, V.; Gerbeth, G.;
In the present paper we are concerned with the control of wake instabilities in the flow of an electrically conducting fluid around a circular cylinder by means of external magnetic fields. Besides the Reynolds number (Re) a second parameter N appears describing the strength of the magnetic body force. This offers, depending on the direction of the magnetic field, a large variety of flow configurations and therefore different transition regimes. We perform a numerical simulation of the unsteady two-dimensional flow and characterize the different flow regimes. Strong magnetic fields are capable to stabilize the 2-D flow and to suppress the shedding of vortices. We present curves of neutral 2-D stability in the (Re,N)-parameter plane separating steady and periodic flow regimes. We further perform a linear 3-D stability analysis of the 2-D flow being either steady or periodic and show how the magnetic field influences the 3-D instabilities. We pay special attention to the case when the magnetic field is aligned with the oncoming flow. Here we find 3-D instability in parameter regions above the 2-D stability curve in the (Re, N)-plane where the flow is 2-D stable (steady). This firstly confirms a general result of Hunt (J.C.R. Hunt, Proc. Roy. Soc. A 293 (1966) 342) obtained from a stability analysis of parallel flows and shows that the magnetic field influences 2-D and 3-D instabilities in a different way.
  • Experimental Thermal and Fluid Science 16 (1998) 92-99

Publ.-Id: 1965 - Permalink


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