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  • 2000-2004  (6)
  • 1985-1989  (12)
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  • 1
    Electronic Resource
    Electronic Resource
    Cell-suspension culture of Arachis hypogaea L.: model system of specific enzyme induction in secondary metabolism (1987)
    Springer
    Planta 172 (1987), S. 238-244 
    Details
    ISSN: 1432-2048
    Keywords: Arachis ; Cell culture ; Enzyme induction (cell culture) ; Phenylalanine ammonia-lyase ; Phytoalexin ; Stilbene synthase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00394593
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  • 2
    Electronic Resource
    Electronic Resource
    Energy loss of deuterons in 3He gas: a threshold effect (2000)
    Springer
    The European physical journal 8 (2000), S. 443-446 
    Details
    ISSN: 1434-601X
    Keywords: PACS. 26.20.+f Hydrostatic steller nucleosynthesis – 34.50.Bw Energy loss and stopping power
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: The energy loss of deuterons in 3He gas was measured at Ed = 15 to 100 keV using the 3He pressure dependence of the 3He(d,p) 4He cross-section at a given incident energy. At the highest energies, the observed energy loss is in good agreement with a standard compilation. However, with decreasing energy the experimental values drop steadily below the theoretical values and near Ed = 18 keV they drop sharply (within 1 keV) reaching the domain of nuclear stopping power. This threshold behavior is due to the minimum 1s→ 2s electron excitation of the He target atoms, i.e. it is a quantum effect. Some consequences are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100530050054
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  • 3
    Electronic Resource
    Electronic Resource
    Destruction of26Al in explosive nucleosynthesis (1986)
    Springer
    The European physical journal 323 (1986), S. 1-11 
    Details
    ISSN: 1434-601X
    Keywords: 25.90 ; 95.90
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The26Al(n, p)26Mg reaction has been studied using neutron spectra which closely resembled Maxwell-Boltzmann (M.-B.) distributions with thermal energies ofkT=40 ×10−6, 31 and 71 keV and also forE n =270–350 keV. These energies correspond to stellar temperaturesT 9=4.6×10−7, 0.36, 0.82 and 3.1–4.1, whereT 9 is in units of 109 K. The partial cross sections for thep 0-(p 1-)transition are found to equal 26±10(1,850 ±150), 13±6(124±17), 16±13(84±14) and 21±8(72±15) mb for the above neutron spectra, respectively. The astrophysical reaction rate is determined for the combinedp 0- andp 1-transitions to beN A 〈σν〉=(0.324±0.026, 20.5±2.7, 22.6±4.3 and 38.7±11.1) ×106 cm3 mole−1 s−1. The results are compared with previous investigations and with statistical model calculations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01294550
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  • 4
    Electronic Resource
    Electronic Resource
    Intrastate γ-transitions: A spectroscopic tool? (1987)
    Springer
    The European physical journal 328 (1987), S. 291-299 
    Details
    ISSN: 1434-601X
    Keywords: 23.20 ; 21.10.-k
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01290497
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  • 5
    Electronic Resource
    Electronic Resource
    Absolute cross section of the3He(α,γ)7Be reaction (1988)
    Springer
    The European physical journal 329 (1988), S. 243-254 
    Details
    ISSN: 1434-601X
    Keywords: 25.55.-e ; 27.10 ; 27.20
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The absolute cross section σ(E) of the3He(α, γ)7Be reaction has been measured fromE c.m. =195 to 686 keV. The studies employed both a supersonic jet gas target and an extended gas target, and were carried out by the observation of the prompt capture γ-ray transitions as well as the7Be residual nuclei. The absolute cross sections deduced from the capture γ-rays are in good agreement with most previous work and remove a discrepancy with other earlier work. In comparison, the σ(E) values obtained from the7Be residual nuclei are systematically higher, suggesting a small production of additional7Be by contaminant reactions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01283781
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  • 6
    Electronic Resource
    Electronic Resource
    The cross section of14N(n, p)14C at stellar energies and its role as a neutron poison forS-process nucleosynthesis (1988)
    Springer
    The European physical journal 330 (1988), S. 167-172 
    Details
    ISSN: 1434-601X
    Keywords: 95.30.C ; 97.10.C ; 25.70
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01293392
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  • 7
    Electronic Resource
    Electronic Resource
    The α-12C scattering studied via the Trojan-Horse method (2000)
    Springer
    The European physical journal 7 (2000), S. 181-187 
    Details
    ISSN: 1434-601X
    Keywords: PACS: 24.50.+g direct reactions – 24.10 nuclear reactions models- and methods – 26.20.+f hydrostatic stellar nucleosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: The Trojan-horse method has been suggested as a means to study a two-body reaction at astrophysical energies via a three-body breakup reaction. In order to test this method the 6Li(12C,α12C)2H reaction was studied in a kinematically complete experiment at an incident energy of 18 MeV. Coincidence spectra show the presence of the quasi-free α-12C scattering process. The excitation function of the three-body reaction is calculated in the plane wave impulse approximation assuming quasi-free scattering and is compared with the experimental data. Also, the excitation function of the virtual α-12C elastic scattering is extracted from the three-body reaction cross section at low deuteron momenta and compared with the behaviour of the free scattering cross section.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00013592
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  • 8
    Electronic Resource
    Electronic Resource
    Absolute cross section of p(7Be,γ)8B using a novel approach (2000)
    Springer
    The European physical journal 7 (2000), S. 303-305 
    Details
    ISSN: 1434-601X
    Keywords: PACS: 26.65.+t Solar neutrinos – 25.60.Dz Interactions and reactions cross sections
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: The absolute cross section σ (E) of the radiative capture reaction p(7Be,γ)8B at the center-of-mass energy E = 992 keV has been measured using a radioactive 7Be ion beam and a windowless gas target system filled with H2 gas. The 8B residual nuclides were detected with a recoil separator consisting of momentum and velocity filters and a ΔE-E detector telescope. The 8B yield was observed concurrently with the 7Be + p elastic scattering yield, relating σ(E) to the Rutherford scattering cross section. The resulting value, σ(E) = 0.41 ± 0.11 μb, leads to an S(E) factor at zero energy of S(0) = 16 ± 4 eV b, in fair agreement with recommended values.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00013599
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  • 9
    Electronic Resource
    Electronic Resource
    Improved information on electron screening in 7Li (p,α)α using the Trojan-horse method (2000)
    Springer
    The European physical journal 9 (2000), S. 435-437 
    Details
    ISSN: 1434-601X
    Keywords: PACS. 24.10.-i Nuclear-reaction models and methods – 25.40.-h Nucleon-induced reactions – 26.35.+c Big bang nucleosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: The available astrophysical S(E) factor data for the reaction 7Li (p,α)α at 10 〈 E 〈 1000keV exhibit an exponential increase at low energies due to the effects of electron screening. A parametrisation of the data using a non-resonant, direct process and two subthreshold resonances reproduces the data at energies E≥ 100keV, while at lower energies this calculated S b(E) factor curve for bare nuclides drops below the data, which in turn represent the case of electron-shielded nuclides, i.e. the electron-shielded S s(E) factor. The comparison between S b(E) and S s(E) leads to an electron-screening potential energy U e = 350eV, which is much higher than the adiabatic limit of 175eV and not understood at present. The deduced value of S b(0) is considerably smaller than the previously adopted value of 59keV b, significantly increasing the calculated abundance of 7Li in big-bang nucleosynthesis. The Trojan-horse method was applied to the reaction 7Li (p,α)α to determine the energy dependence of the S b(E) factor for 10 〈 E 〈 370keV, free from the effects of the Coulomb barrier and electron screening. The THM results are close to the calculated S b(E) curve and suggest that the THM may become a powerful way to obtain improved information on low-energy cross-sections and associated electron-screening effects in a model-independent way.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100500070001
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  • 10
    Electronic Resource
    Electronic Resource
    The 27Al (p,γ)28Si reaction: direct capture cross-section and resonance strengths at Ep = 0.2-1.12 MeV (2000)
    Springer
    The European physical journal 9 (2000), S. 479-489 
    Details
    ISSN: 1434-601X
    Keywords: PACS. 25.40.Lw Radiative capture – 25.40.Ny Resonance reactions – 29.40.Mc Scintillation detectors – 27.30.+t 20 ?A? 38
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: The 27Al(p,γ)28Si reaction has been investigated using two different 4π NaI summing detectors. The strength of 26 resonances in the energy range from 200 to 1120 keV has been measured. In addition, yield measurements have been carried out at 9 beam energies in the 490 to 1150 keV range in order to determine the direct capture cross-section. The existing data on the non-resonant mechanism were analysed and combined with the results of the present work. The resulting resonance strengths as well as the deduced direct capture astrophysical S-factor are compared with previous work.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100500070006
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