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  • 1990-1994  (7)
  • 1
    Digitale Medien
    Digitale Medien
    Cross sections for nuclear reactions in collisions of238U+238U and238U +197Au near and below the coulomb barrier (1991)
    Springer
    The European physical journal 340 (1991), S. 303-314 
    Details
    ISSN: 1434-601X
    Schlagwort(e): 25.70.CD ; 25.70.Lm ; 25.85.−W
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Cross sections for nuclear reactions at beam energies near and below the spherical Coulomb barrier V c were measured in the very heavy collision systems238U +238U and238U +197Au. The most probable reaction channel with mass transfer is the one-neutron transfer. Its excitation function is understood in terms of Rutherford trajectories together with the quantal process of neutron tunnelling over large distances. In addition, the exchange of up to 15 nucleons is observed down to 0.90 V c . The excitation functions for the multi-nucleon transfer products have much steeper slopes than that for one-neutron transfer, and are steeper for238U +197Au than for238U +238U, suggesting that nuclear contact is established in the associated collisions. The angular distribution for one selected multi-nucleon transfer product,227Th, shows that its formation occurs in more central collisions within contact times shorter than about 10−21 s. There is no evidence for very longlived di-nuclear systems in the these reactions.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01294679
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  • 2
    Digitale Medien
    Digitale Medien
    Scanning tunneling microscopy study of pinning-induced vortex lattice distortion in ion-irradiated NbSe2 (1994)
    Springer
    The European physical journal 94 (1994), S. 213-215 
    Details
    ISSN: 1434-6036
    Schlagwort(e): 61.16.Ch ; 61.80.Jh ; 74.60.Ge ; 74.70.Ad
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We observe vortex pinning in 2.2 GeV Au-ion irradiated NbSe2 by scanning tunneling microscopy (STM) at 3K. The ion irradiation generates columnar defects which act as pinning sites. At various external magnetic fields the vortex arrangement is clearly resolved but shows strong distortion. The location of individual defects is extracted from STM data and compared to the vortex arrangement.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01320670
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  • 3
    Digitale Medien
    Digitale Medien
    Competition between binary reactions and fusion in heavy-ion collisions at the Coulomb barrier (1992)
    Springer
    The European physical journal 342 (1992), S. 411-427 
    Details
    ISSN: 1434-601X
    Schlagwort(e): 25.70.Cd ; 25.70.Jj ; 25.70.Lm
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Mass and charge distributions for binary reaction channels have been measured for the reactions86Kr with76Ge,104Ru and130Te at the Coulomb barrier using chemical separations andγ-ray spectroscopy. These systems span the region where dynamical hindrance to complete fusion sets in. The binary reactions can be subdivided into two components associated withi) reflection from the outer potential barrier (quasielastic), andii) reseparation after passing the barrier (complex reactions). The sum of complex-reaction channels and evaporation residues from complete fusion can be reproduced by a barrier passing calculation. The fraction of the barrier passing flux leading to reseparation increases from 26±10% for the lightest system to more than 90% for the heaviest system. The data indicate that fusion hindrance is primarily caused by reseparation shortly after passage of the barrier before Swiatecki's conditional saddlepoint is overcome, resulting in partitions close to the entrance channel configuration. In addition, for the heaviest system, a quasifission component representing somewhat less than 20% of the barrier-passing flux was observed. From the missing masses of fragment pairs we can deduce that the reseparating complex-reaction products have kinetic energies well below the fusion barrier and share the excitation energy in a way similar to the sawtooth-like curve known from low-energy fission. The quasielastic, predominantly one- and two-nucleon transfer channels, have strongly varying cross sections for the three systems despite similar effectiveQ-values. A systematics of one-neutron transfer cross sections at the Coulomb barrier is established and shown to differ considerably from the smooth behaviour observed at energies 20–30% above the barrier. The connection to nuclear polarization phenomena and orbit matching is pointed out.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01294952
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  • 4
    Digitale Medien
    Digitale Medien
    Electromagnetic and nuclear fission of238U in the reaction of 100, 500, and 1000 A·MeV208Pb with238U (1994)
    Springer
    The European physical journal 350 (1994), S. 221-227 
    Details
    ISSN: 1434-601X
    Schlagwort(e): 25.85.-w ; 25.70.-z
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The folding- and azimuthal-angle and velocity distributions for the238U fission fragments have been measured in reactions with 100, 500, and 1000 A·MeV208Pb. These distributions were used to decompose the fission cross section into its electromagnetic and nuclear components. The fraction of electromagnetic fission was found to be 0.16±0.07, 0.48±0.08, and 0.60±0.04, respectively. The electromagnetic fission cross section as a function of the208Pb nucleus energy is compared with theoretical predictions. The measured fission cross section from nuclear reactions (≈1.5 b) is approximately constant between 100 and 1000 A·MeV.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01289586
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  • 5
    Digitale Medien
    Digitale Medien
    Reactions of40Ar with233U,235U, and238U at the barrier (1990)
    Springer
    The European physical journal 335 (1990), S. 421-430 
    Details
    ISSN: 1434-601X
    Schlagwort(e): 25.70.CD ; 25.70.JJ ; 25.70.LM
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Production cross sections for target-like transfer products in reactions of40Ar with233,235,238U at the barrier were determined using radiochemical techniques. The heaviest products detected are isotopes of californium (Z=98). In addition to the quasi-elastic component of the isotopic distributions observed in the vicinity of uranium, there are also relaxed contributions throughout the entire region. The peak positions of the isotope distributions of this component for fixed atomic number, after the transfer of 〉 3 charges, approach closely the minimum of the potential energy surfaces (PES). The experimental results thus indicate the cold formation of the reaction products. A search for long-lived heavy actinides produced, by fusion-evaporation, via isotopes of element 110 and their subsequent decay through α-decay chains, remained unsuccessful at a cross section limit of 21 pb.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01290190
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  • 6
    Digitale Medien
    Digitale Medien
    The influence of columnar defects on the critical current density in (Bi, Pb)2Sr2Ca2Cu3O10 + δAg tapes (1994)
    Springer
    Journal of superconductivity 7 (1994), S. 783-786 
    Details
    ISSN: 1572-9605
    Schlagwort(e): Columnar defects ; critical current density ; tapes ; 2223 BPSCCO ; pinning energy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Physik
    Notizen: Abstract An excellent tool to enhance the critical current density in superconductors is the controlled introduction of defects by irradiation damage. Irradiation with 2.65 GeV Au ions provides the generation of amorphous line defects. Polycrystalline (Bi, Pb)2Sr2Ca2Cu3O10 + δ Ag tapes processed by the powder-in-tube technique were irradiated up to doses of 3.5× 1011 Au ions/cm2 at a temperature of 100 K. On the one hand, our irradiation experiments were performed to investigate the degree ofj c enhancement and, on the other hand, to examine the flux pinning mechanism in (Bi, Pb)2Sr2Ca2Cu3O10 + δ tapes. Characterization of the samples was performed by magnetization measurements using a vibrating sample magnetometer (VSM) up to 13 T in a temperature range between 5 and 100 K. Further, we have measured the relaxation of the magnetic moment before and after irradiation to determine the influence of columnar defects on the activation energyU. A comparison of the irradiation-induced effects with previous results obtained on Bi2Sr2CaCu2O8 + δ irradiation experiments is included.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01320869
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  • 7
    Digitale Medien
    Digitale Medien
    Video-Feedback-Therapie mit dem flexiblen Nasopharyngoskop (1994)
    Springer
    Journal of orofacial orthopedics 55 (1994), S. 197-201 
    Details
    ISSN: 1615-6714
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Beschreibung / Inhaltsverzeichnis: Summary Psychological interviews with cleft palate patients have revealed why a number of these patients do not profit, or do so only on a limited basis, from conventional speech therapy. They don't control articulation by means of the auditory chanal. To treat these patients the video feedback therapy with the nasopharyngoscopy (Witzel et al. [11]) was employed as the initial step. The next step was to expland on this method by establishing indication criteria, necessary diagnostic techniques, and an efficient therapy plan. In this paper a single case study is employed to discuss this method and show the results attained by its use.
    Notizen: Zusammenfassung Aus psychologischen Interviews mit Spaltpatienten wurde deutlich, warum ein Teil der Patienten von der herkömmlichen logopädischen Therapie nicht oder nur unzureichend profitiert. Für diese Patienten wurde die Methode der Video-Feedback-Therapie mit dem Nasopharyngoskop nachWitzel et al. [11] erprobt und erweitert. Krieterien zur Indikation, die notwendige Diagnostik und ein effizienter Therapieaufbau wurden erarbeitet. Die Methode und Ergebnisse werden anhand einer Einzelfallstudie dargestellt und diskutiert.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02285412
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