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971.
The thermally initiated and platinum-catalyzed polymerization of 1-silacyclobutanes with substitutents containing a trimethylsilyl group was carried out. Soluble, high-molecular-weight, heterochain siltrimethylene polymers were obtained, containing trimethylsilyl groups removed from the main chain by various bridges.A. V. Topchiev Institute of Petrochemical Synthesis, Russian Academy of Sciences, 117912 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 1, pp. 223–225, January, 1992.  相似文献   
972.
973.
974.
975.
We report on a successful attempt to fabricate a Coulomb blockade electrometer consisting of an ultrasmall YBa2Cu3O7−δ (YBCO) island coupled to two gold electrodes through a high-resistance native surface tunnel barrier. A third electrode placed near the island was used as an electrostatic gate. Spectra typical for tunneling into the YBCO superconductor were reproducibly measured. At temperatures below 0.5 K the low-bias conductance was suppressed by the Coulomb blockade. The blockade could be periodically varied by the gate potential. An external magnetic field of up to 5 T strongly influenced the transport via the island but without any change in the period of the Coulomb oscillations. Pis’ma Zh. éksp. Teor. Fiz. 63, No. 2, 112–117 (25 January 1996) Published in English in the original Russian journal. Edited by Steve Torstveit.  相似文献   
976.
Intensity-dependent absorption of 25 ns excimer laser pulses in common UV-window materials was investigated. By employing a calorimetric technique which provides greatly enhanced sensitivity compared to transmissive measurements, two-photon absorption coefficients were determined at intensities of 2–80 MW/cm2 and found to be in good agreement with previous measurements at 10–100 GW/cm2. Also, color-center formation in fused silica was observed. It was possible to quantify transient and cumulative effects as a function of intensity.  相似文献   
977.
The isomerization mechanism of 2′(OH)chalcone (1) in flavanone (2) was studied. The calculations were performed with the semiempirical method AM1, using totally optimized molecular geometries. A 6-step mechanism including several equilibrium states was proposed. It was concluded that: (a) At the conformational equilibrium of 1 there could be 43.9% of s-cis conformer; (b) The acid dissociation of 1 trans-s-trans is considerable; (c) The EE, ΔHf and net charges show that the rotation of ring A of 1 and the formation of ring C of 2 occurs without greater impairments; (d) Although the keto structure is the most stable one, the enolate of 2 is present in the reaction medium; (e) The conversion of enol of 2 in the keto form would be the limiting step of the analyzed isomerization rate.  相似文献   
978.
979.
A quasipotential operator for a system of two scalar particles, and also an integral equation and a normalization condition for the wave function of the connected state, are obtained by the method of two-time Green's functions in an explicitly covariant form. The cases are considered of scalar and electromagnetic interactions of particles of the system.Frantsiska Skoriny Gomel' State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 112–118, June, 1993.  相似文献   
980.
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