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  • 1990-1994  (14)
  • 1985-1989  (12)
Materialart
Erscheinungszeitraum
Jahr
  • 1
    ISSN: 1434-601X
    Schlagwort(e): 25.55.−e
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Cross section measurements of thed(3He,p)4He reaction have been extended to an energy as low asE cm =5.4 keV. The data have an improved accuracy compared with previous work and confirm the existence of electron screening. The combined analysis of the present and previous data leads to an electron screening potential ofU e =123 ± 9 eV. A similar analysis of previous data for3He(d, p)4He leads toU e =186 ± 9 eV. Both screening potentials differ due to the molecular and atomic aggregate state of the targets involved in these investigations and are significantly larger than expected from available atomic physics models, supporting the general trend in studies of electron screening.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    The European physical journal 350 (1994), S. 93-94 
    ISSN: 1434-601X
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The observed M1 capture amplitude in7Li(p,γo)8Be At Ep=80−0 keV originates predominantly from the low-energy tail of a resonance at 441 keV, thue removing a recent criticism on the extrapolation of S(E) data such as for7Be(p,γ)8B.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    The European physical journal 346 (1993), S. 309-318 
    ISSN: 1434-601X
    Schlagwort(e): 61.80.f ; 61.80.M
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Mylar foils have been irradiated under typicalPIXE conditions using the Bochum nuclear microprobe. The induced radiation damage was investigated with theHEIS technique for studies of the chemical composition and theSTIM technique for studies of the extent of axial and lateral damage. The data show that the current density of the microbeam influences the extent of axial and lateral damage in the foils, while the fluence of the microbeam causes changes in chemical composition: more than one-half of the originalH andO abundances are lost, while theC abundance — after a 15% drop within the first few seconds — increases slowly with fluence. Furthermore, the thickness of the foil affects the final chemical composition of the sample only at large fluences. The results indicate that some caution is necessary in the interpretation of PIXE analyses of trace elements in biological or medical samples using nuclear microprobes.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 4
    ISSN: 1434-601X
    Schlagwort(e): 27.30.+t ; 97.10.Cv ; 97.10.Tk ; 97.30.Qt ; 98.58.Ca
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Nuclear levels of23Mg near and above the proton threshold were investigated with high resolution. A new level has been identified at 7.643 MeV (66 keV above the proton threshold) with a possible Jπ=(3/2, 5/2)+. Some other spin-parity and excitation-energy assignments are also made. These results enable the reaction rate estimate of22Na(p,γ)23Mg with much smaller uncertainties, which is critical for the Ne-E problem in nuclear astrophysics.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 5
    ISSN: 1432-2048
    Schlagwort(e): Arachis ; Cell culture ; Enzyme induction (cell culture) ; Phenylalanine ammonia-lyase ; Phytoalexin ; Stilbene synthase
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract A peanut (Arachis hypogaea L.) cell-suspension culture susceptible to selective induction of stilbene formation was established. The principles of defense responses of the whole plant were found to be retained in the artificial system. The suspension culture was characterized by its growth curve and by various biochemical parameters. In the stationary phase, reached 8 d after transfer to a new medium, the formation of stilbenes and stilbene synthase could be induced without altering the levels of other enzymes. Eighteen hours after applying an artificial elicitor (ultraviolet-C light) or 4 h after eliciting with a crude preparation of Phytophthora cambivora cell walls, phenylalanineammonia-lyase activity was increased eightfold and stilbene-synthase activity 20-fold. The activity of phenylalanine ammonia-lyase reached its peak at a slightly different time from that of stilbene synthase. The main products of L-phenylalanine metabolism in the induced cells were resveratrol, 3,3′,5-trihydroxy-4′-methoxystilbene and isopentenylresveratrol. Likewise, feruloyl-CoA reductase, as a parameter of lignin formation, was enhanced following induction, albeit with a different time course and with a less steep increase than found for phenylalanine ammonia-lyase and stilbene synthase.
    Materialart: Digitale Medien
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  • 6
    Digitale Medien
    Digitale Medien
    Springer
    The European physical journal 343 (1992), S. 483-487 
    ISSN: 1434-601X
    Schlagwort(e): 12.40.Qq ; 13.25.+m ; 14.40.Cs
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract A direct search for theE R =70 keV resonance in17O(p, α)14N was carried out using17O enriched Ta2O5 targets in combination with a 1 mA proton beam and suitable detectors of large solid angle. The observed upper limit for the resonance strength isωγ≤8×10−10 eV.
    Materialart: Digitale Medien
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  • 7
    ISSN: 1434-601X
    Schlagwort(e): 25.55 ; 97.10
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The 22Ne(α,n)25Mgreaction is thought to be one of the main neutron sources for the astrophysical s-process. Thus cross section data for this reaction have been obtained from near the threshold (E α≈570keV) up toE α=2100 keV using the 4 MV DYNAMITRON accelerator at Stuttgart, the windowless gastarget system RHINOCEROS and a 4π neutron detector. Two new resonances have been observed atE α=623 ± 6 and 838 ± 6 kev, which dominate the reaction rate at T9〈0.3.Possible background reactions are discussed.
    Materialart: Digitale Medien
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  • 8
    Digitale Medien
    Digitale Medien
    Springer
    The European physical journal 345 (1993), S. 333-334 
    ISSN: 1434-601X
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The absolute cross section of the fusion reaction 10B(p, α1γ)7 has been measured at the c.m. energy range E=48 to 159 keV via the 429 keV secondary γ-ray transition. The studies involved high proton currents and thick solid 10Btargets. The resulting cross sections have the same energy dependence as those of the 10B(p,α0)7Bereaction but they are lower by a factor 600.
    Materialart: Digitale Medien
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  • 9
    Digitale Medien
    Digitale Medien
    Springer
    The European physical journal 328 (1987), S. 291-299 
    ISSN: 1434-601X
    Schlagwort(e): 23.20 ; 21.10.-k
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract In the framework of a potential model we have calculated the various bremsstrahlung cross sections into the5Li ground state, includingM 1 andE 2 γ-transitions leading from the high energy wing of the5Li ground state resonance into states belonging to the same resonance at lower energy (intrastate transition). Our calculation supports the hypothesis of Schmalbrock et al. [1] that intrastate transitions ofM 1 andE 2 multipolarity exist. While we find a maximum cross section of roughly 1.4 nb for theE 2 transition, we predict the cross sections forM 1 intrastate transition to be less than 3·10−5nb. An experimental observation of the intrastate γ-ray emission appears to be very difficult due to the dominance of competing resonant (M 1) and direct (E 1) capture processes. Schmalbrock et al. have suggested to deduce magnetic dipole and electric quadrupole moments of resonant states from the measurements of the respectiveM 1 andE 2 intrastate transitions. We will show that theM 1 intrastate cross sections do not yield the appropriate information to determine the magnetic dipole moment. We will also discuss thatE 2 intrastate transitions do not seem to be a suited tool to find the quadrupole moment of an unstable state.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 10
    ISSN: 1434-601X
    Schlagwort(e): 95.30.C ; 97.10.C ; 25.70
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The absolute average cross section 〈σ〉 of the14N(n, p)14C reaction has been measured using neutron spectra that closely resemble Maxwell-Boltzmann distributions with thermal energies of kT=25.0 and 52.4 keV: 〈σ〉=0.81±0.05 and 0.52±0.06 mb, respectively. The resulting reaction rates are nearly the same at T9=0.29 and 0.61, and their average, NA〈συ〉=(1.3±0.1)×105 cm3 s−1 mol−1, is about a factor of three smaller than the previously adopted values obtained by extrapolation between thermal and higher-energy data. Thus, the14N(n, p)14C reaction plays a correspondingly smaller role as a neutron poison fors-process nucleosynthesis.
    Materialart: Digitale Medien
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