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p palan BS 《Physical review letters》1987,58(16):1597-1599
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Molar extinction coefficients of some carbohydrates viz. l-arabinose (C5H10O5), d-glucose (C6H12O6), d-mannose (C6H12O6), d-galactose (C6H12O6), d(-) fructose (C6H12O6) and maltose (C12H24O12) in aqueous solutions have been determined at 81, 356, 511, 662, 1173 and 1332 keV by gamma ray transmission method in a
narrow beam good geometry set-up. These coefficients have been found to depend upon the photon energy following a 4-parameter
polynomial. These extinction coefficients for different sugars having the same molecular formula have same values varying
within experimental uncertainty. Within concentration ranges studied, Beer-Lambert law is obeyed very well. 相似文献
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In this paper we deal with the measurement of parameters of the gravitational wave signal emitted by a coalescing binary system
of compact stars. We present the results of Monte Carlo simulations carried out for initial LIGO, incorporating the first
post-Newtonian corrections to the waveform. Using the parameters so determined, we estimate the direction to the source. We
stress the use of the time-of-coalescence rather than the time-of-arrival of the signal to determine the direction of the
source. We show that this can considerably reduce the errors in the determination of the direction of the source. 相似文献
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van Eis MJ van Der Linde BS de Kanter FJ de Wolf WH Bickelhaupt F 《The Journal of organic chemistry》2000,65(14):4348-4354
In contrast to the terminal phosphinidene complex PhPW(CO)(5) (2), which adds to [5]metacyclophane (1) in a 1,4-fashion, dichlorocarbene preferentially adds in a 1,2-fashion to the formal "anti-Bredt" type double bond of the aromatic ring of 1 to afford the norcaradiene 11b, which immediately rearranges to the bridged cycloheptatriene 12b and further by a [1,5] sigmatropic chlorine migration to the isomeric 13b as the first observable product. More slowly, the latter isomerizes via a dissociative mechanism to give 15b. A computational study supports the notion that the [1,5] chlorine migration in the rearrangement 12b --> 13b, for which an activation barrier of 70.2 kJ mol(-)(1) was calculated, is essentially concerted with minor charge separation. In contrast, the analogous [1,5] chlorine migration in the flat model compound 7,7-dichlorocycloheptatriene (12a) displays features of a dissociative pathway. 相似文献
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The nonminimal coupling of a massive self-interacting scalar field with a gravitational field is studied. Spontaneous symmetry
breaking occurs in the open universe even when the sign on the mass term is positive. In contrast to grand unified theories,
symmetry breakdown is more important for the early universe and it is restored only in the limit of an infinite expansion.
Symmetry breakdown is shown to occur in flat and closed universes when the mass term carries a wrong sign. The model has a
naturally defined effective gravitational coupling coefficient which is rendered time-dependent due to the novel symmetry
breakdown. It changes sign below a critical value of the cosmic scale factor indicating the onset of a repulsive field. The
presence of the mass term severely alters the behaviour of ordinary matter and radiation in the early universe. The total
energy density becomes negative in a certain domain. These features make possible a nonsingular cosmological model for an
open universe. The model is also free from the horizon and the flatness problems. 相似文献