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  • 1990-1994  (2)
  • 1980-1984  (3)
  • 1
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We have extended the measurements ofK-andL-shell ionization cross sections by electron impact into the ultra relativistic energy region, 0.9≦E≦2.0 GeV, in order to search for a saturation of the cross section. This phenomenon, which is due to the polarization of the target medium, is called density effect. It is predicted to occur at several hundred MeV impact energy and preferentially for lowZ target elements. Theoretical calculations are presented, based on the one-photon-exchange approximation. The absolute measurements of theK-andL-shell cross sections for Ni(K), Cu(K), Ag(K, L) and Au(L) performed at the 2.5 GeV electron synchrotron of the Bonn University, however, exhibit that the cross sections show no saturation but are still increasing. Furthermore, from theK X-ray yields, obtained at 0.9 and 2.0 GeV by bombarding the lowZ elements S, Ca, Mn, Ni and Ge, we obtain for the corresponding cross section ratio σ K (2GeV)/σ K (0.9GeV)=1.08±0.01 on the average. TheK X-ray yield of a composite Ca — Mn target amounts to $$[\sigma _K (Ca;2.0GeV)/\sigma _K (Mn;2.0GeV)]/[\sigma _K (Ca;0.9GeV/\sigma _K (Mn;0.9GeV)] = 0.99 \pm 0.02.$$ . All three results are in disagreement with theory. This severe discrepancy is discussed but the origin for it is not yet understood.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The production of neutral pions in nucleus nucleus collisions with 44 MeV/u Ar projectiles from the accelerator GANIL has been observed. The angular distributions indicate a collective production process, and the pion spectra reflect properties of the collision dynamics.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-0584
    Keywords: MDS ; PCR ; p53 ; Nonradioactive SSCP
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary p53 is one of the most frequently mutated genes in human cancers. Since p53 has been implicated in lymphatic and some myeloid leukemias, such as the blastic phase of chronic myelogeneous leukemia, we sought to address the role of p53 gene mutations within exons 4–9 in myelodysplastic syndromes (MDS), a myeloid preleukemic condition. In order to avoid the potential hazard of using radioactive single-strand conformation analysis (SSCP), we used a nonradioactive SSCP method based on the silver stain of small minigels. In cell lines with known point mutations of the p53 gene, aberrant migrating bands were found. Serial dilutions indicated a sensitivity comparable to radioactive methods. Furthermore, a common polymorphism within the 4th exon of the p53 gene was easily detected. However, of 17 primary samples from patients with MDS, none harbored a p53 gene mutation. We conclude that this nonradioactive method can easily be used to screen for p53-gene mutations, and that p53-gene mutations do not play a major role in the pathogenesis of MDS.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Evaporation residue measurements have been made for the40Ar+40Ca system at high incident energies,E Lab=161, 190, 236 and 273 MeV. A dynamical description of the fusion process is presented, where in a trajectory model both rotational and neck degrees-of-freedom are included. Using this model maximuml-values for fusion are determined and at high incident energies are found to be significantly lower than those found when using the more usual one-dimensional effective nucleus-nucleus potential. The fusion cross sections minus the fission component yields evaporation residue cross sections that are in good agreement with the data. Also, mass distributions of the evaporation residues compare well with statistical-decay model predictions. A comparison is made with the similarly mass-symmetric40Ca+40Ca system.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 619 (1993), S. 109-116 
    ISSN: 0044-2313
    Keywords: Perthioborates, RbBS3, TlBS3, Tl3B3S10 ; preparation ; crystal structures ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: The Perthioborates RbBS3, TIBS3, and Tl3B3S10.RbBS3 (P21/c, a=7.082(2) Å, b=11.863(4) Å, c=5.794(2) Å, β=106.54(2)°) was prepared as colourless, plate-shaped crystals by reaction of stoichiometric amounts of rubidium sulfide, boron, and sulfur at 600°C and subsequent annealing. TlBS3 (P21/c, a=6.874(3) Å, b=11.739(3) Å, c=5.775(2) Å, β=113.08(2)°) which is isotypic with RbBS3 was synthesized from a sample of the composition Tl2S · 2 B2S3. The glassy product which was obtained after 7 h at 850°C was annealed in a two zone furnace for 400 h at 400→350°C. Yellow crystals of TlBS3 formed at the warmer side of the furnace.Tl3B3S10 (P1, a=6.828(2) Å, b=7.713(2) Å, c=13.769(5) Å, α=104.32(2)°, β=94.03(3)°, γ=94.69(2)°) was prepared as yellow plates from stoichiometric amounts of thallium sulfide, boron, and sulfur at 850°C and subsequent annealing.All compounds contain tetrahedrally coordinated boron. The crystal structures consist of polymeric anion chains. In the case of RbBS3 and TlBS3 nonplanar five-membered B2S3 rings are spirocyclically connected via the boron atoms. To obtain the anionic structure of Tl3B3S10 every third B2S3 ring of the polymeric chains of MBS3 is to be substituted by a six-membered B(S2)2B ring.
    Notes: Farblose, plättchenförmige Kristalle von RbBS3 (P21/c, a=7,082(2) Å, b=11,863(4) Å, c=5,794(2) Å, β=106,54(2)°) entstehen aus einem stöchiometrischen Ansatz von Rubidiumsulfid, Bor und Schwefel bei 600°C und anschließendem Tempern. Die zu RbBS3 isotype Phase TlBS3 (P21/c, a=6,874(3) Å, b=11,739(3) Å, c=5,775(2) Å, β=113,08(2)°) erhält man aus dem Ansatz Tl2S · 2 B2S3. Das nach 7 h bei 850°C erhaltene glasige Produkt wird in einem Zweizonenofen 400 h bei 400→350°C ausgelagert. Gelbe Kristalle der Verbindung bilden sich in der wärmeren Ofenzone. Das ebenfalls gelbe Tl3B3S10 (P1, a=6,828(2) Å, b=7,713(2) Å, c=13,769(5) Å, α=104,32(2)°, β=94,03(3)β, γ=94,69(2)°) bildet sich aus stöchiometrischen Mengen von Thalliumsulfid, Bor und Schwefel bei 850°C und anschließendem Tempern.Die ausschließlich tetraedrisch koordiniertes Bor enthaltenden Verbindungen bilden polymere Kettenstrukturen, die sich im Fall des RbBS3 und TlBS3 aus spirocyclisch über die Boratome verknüpften, nichtplanaren Trithiadiborolan-Ringen aufbauen. Ersetzt man in diesen Anionenketten jeden dritten B2S3-Fünfring durch einen B(S2)2B-Sechsring, so erhält man die Anionenstruktur des Tl3B3S10.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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