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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 7422-7426 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The band structure of hexagonal boron nitride (BN) has been calculated using an ab initio linear combination of pseudoatomic-orbitals method. The calculated band structure confirms a previous finding that this material is an indirect band-gap insulator and has two empty interlayer bands. Projected densities of states are compared with the experimental x-ray emission spectra of B and N K edges and the agreement is good. This good agreement between the present ground-state calculation and the experimental x-ray emission spectra supports our previous finding that there should be very little valence electron relaxation effect on x-ray emission spectra. A real-space Green's function technique and the Z+1 approximation have been used to calculate the exciton spectra of B and N K edges. The first peak at 192 eV in B K edge is found to be a bound exciton with a binding energy of 1.7±0.4 eV. Only resonance is found for the N K edge. The calculated exciton spectra agree very well with the experimental quantum-yield and electron-energy-loss spectra.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 2174-2178 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A theory of ultrafast time-resolved x-ray diffraction is presented. We show that for the case in which vibrational relaxation is fast, the x-ray diffraction intensities in pulse laser heating are determined by the Debye–Waller factor. We also show how the scattering intensities of the diffraction spots change with the position of the dissociating atoms in a time-resolved x-ray diffraction experiment studying dissociation reactions in solids. Our results show that the scattering intensities change in both the fully dissociated and the partially dissociated cases, and that time-resolved x-ray diffraction could be a useful tool in probing dissociation reactions in solids.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 6510-6512 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Measurements of the low field resistive anisotropy (LFRA) in amorphous Fe91Zr9 with and without hydrogen loading are presented. The temperature dependence of these data is compared with model calculations of the quadrupolar term [〈〈S2Z〉T〉J−S(S+1)/3], from which it is concluded that the model calculations reproduce both the temperature and the exchange bond dependence of this transport coefficient.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 5964-5966 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Measurements of the spontaneous resistive anisotropy(SRA)—basically the difference between the longitudinal and transverse magnetoresistance extrapolated to zero induction—in amorphous FeZr as a function of field (0–1 T) and temperature (1.5–300 K) are presented. The Fe concentrations investigated range from 89 to 92 at. % and the effects of hydrogenation have also been studied. For the hydrogen-free samples a nonzero SRA develops at the ferromagnetic ordering (Curie) temperature Tc and persists to the lowest attainable temperature, with no obvious anomaly in the vicinity of the proposed transverse-spin freezing temperature Txy. With the inclusion of hydrogen, both Tc and the magnitude of the SRA increase, and attempts are made to correlate such increases with the changes in band structure and mean iron moment.
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 288-290 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Various approximations in the calculations of electron energy-loss cross section and x-ray absorption coefficient have been evaluated using the Si L2,3 edge as an example. It was found that the random phase approximation, for which the cross terms are neglected in the expressions of electron energy-loss cross section and x-ray absorption coefficient, is a very good approximation. The dipole approximation in the calculation of the electron energy-loss cross section was found to begin to break down even at small acceptance half angles, such as 12.5 mrad. For energy losses larger than that of the Si L2,3 edge the dipole approximation will break down faster. This approximation also fails for a large scattering angle even at a small energy loss. The electron energy-loss cross section and x-ray absorption coefficient of the Si L2,3 edge has been calculated and compared. The large difference in relative intensity reported experimentally between the two spectra is not confirmed in this study. More experimental comparisons between electron energy loss and x-ray absorption spectra are recommended for Si and other compounds.
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  • 6
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 4518-4525 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A new unified parametrization scheme for the complete neglect of differential overlap method, applicable to heavy atom systems is formulated. The exponents ζμ and electronegativities X(μ) of atomic orbitals are corrected by the relativistic Dirac–Fock expectation values of atomic orbital radii and energy levels. This leads to the possibility of calibrating the β0 parameters directly by the equilibrium geometric configuration of molecules. The parametrization for hydrogen, halides, and rare earth series, as well as some test calculations for compounds of these elements, have been carried out to show the utility of the scheme. The results demonstrate that the present scheme can give satisfactory MO levels and ionization potentials as well as correct molecular geometry.
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  • 7
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 63 (1993), S. 3553-3555 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on the operation of an all-optical beam deflector whereby the deflected signal beam can be more powerful than the driving beam. Therefore, we have transferred the modulation of the driving beam to the signal beam with power gain and angular deflection rate of 10 mrad/kW. The main component of our deflector is a sample of Cd(S,Se) doped glass and its operation is based on the cross-bending effect.
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  • 8
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 59 (1991), S. 2666-2668 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A two-color "z'' scan method is introduced to characterize the nonlinear refraction of optical materials in their absorptive region. We demonstrate the method by measuring the sign and the magnitude of the frequency nondegenerate nonlinearity in the absorptive region of semiconductor doped glasses.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Oecologia 84 (1990), S. 398-403 
    ISSN: 1432-1939
    Keywords: Isopoda ; Litter quality ; Consumption rates ; Assimilation efficiency ; Feeding preference
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The feeding behaviour of four sympatric isopods from a Hong Kong forest has been investigated. The study included two armadillids (Formosillo raffaelei and Orodillo maculatus) and two philosciids (Burmoniscus ocellatus and Burmoniscus sp.). When given a choice of eight types of litter, all isopod species showed significant dietary selection, and food preferences were similar. Berchemia racemosa (Rhamnaceae) was most readily consumed, followed by Celtis sinensis (Ulmaceac), while feeding rates on Cinnamomum camphora (Lauraceae) were low. The armadillids exhibited a narrower dietary spectrum than the philosciids. All isopods showed significant differences in consumption rates when each litter type was presented separately to them. Cinnamomum camphora was eaten the slowest, while Celtis sinensis and Berchemia racemosa were the top-ranked species. Although patterns of litter ranking based on percentage eaten or feeding rates were similar, all isopods ate more food when given a mixture of leaves than when presented with a single litter type. Assimilation rates were, in general, positively related to feeding rates. On this basis, it appears that assimilation may influence food preference. There were no clear relationships between food preference or feeding rates and ash, calcium, copper, soluble tannin or energy content of the litter. This finding may indicate the benefits of isopods maintaining a mixed diet, consuming certain litter species to meet their calcium or copper requirements and then switching to others so as to meet daily energy needs and to avoid excessive injection of tannins or plant allelochemicals.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Euphytica 70 (1993), S. 151-157 
    ISSN: 1573-5060
    Keywords: interspecific hybridization ; Leptosphaeria nodorum ; Septoria nodorum ; rate-reducing resistance ; Triticum spp. ; wheat, durum wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Resistance to septoria nodorum blotch in Triticum monococcum, T. tauschii, T. timopheevii, T. dicoccum and T. durum was evaluated on plants at the three-leaf stage in greenhouse tests. A high frequency of resistant genotypes was found in T. monococcum, T. tauschii and T. timopheevii, but not in T. dicoccum and T. durum. The resistance of F1 plants of crosses of resistant T. monococcum (PI 289599) and T. timopheevii (PI 290518) accessions with susceptible common wheat cv. Park and durum wheat cv. Wakooma, respectively, was evaluated on the basis of percentage leaf necrosis, lesion number, lesion size and incubation period. No dominance was found for long incubation period, but various dominance relationships occurred for low percentage leaf necrosis, low lesion number and small lesion size, depending on the cross. Multiple regression analysis showed that lesion number contributed more to percentage leaf necrosis than lesion size or incubation period. Resistance to septoria nodorum blotch was transferred successfully from T. timopheevii to cultivated durum wheat. Resistant BC1F7 lines, recovered from the T. timopheevii (PI 290518) × Wakooma cross, showed normal chromosome behaviour at meiosis (14 bivalents) and were self-fertile. However, an effective level of resistance was not recovered in lines derived from the other interspecific crosses.
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