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921.
Conclusions Karatavic acid has been isolated from the resin of the roots ofFerula karatavica Rgl. et Schmalh; this is an ether of umbelliferone and a hydroxy acid C15H24O3 probably having the humulane type of hydrocarbon skeleton. Two possible structural formulas—(I) and (II)—have been proposed for karatavic acid.Khimiya Prirodnykh Soedinenii, Vol. 4, No. 5, pp. 283–287, 1968  相似文献   
922.
Ketones of the 3-nitro-5-R-1,2,4-triazole series react with hydrazoic acid in concentrated sulfuric acid to give triazolyl-substituted acetamides. Acid hydrolysis of the latter leads to 1-aminoalkyl-3-nitro-5-R-1,2,4-triazoles. Intramolecular cyclization with the elimination of HNO2 and the formation of 2-nitro-5,6-dihydro-1H-imidazo[2,3-b]-1,2,4-triazole was noted in the case of 1-(2-aminoethyl)-3,5-dinitro-1,2,4-triazole.See [1] for communication XX.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1271–1273, September, 1977.  相似文献   
923.
This note consists of two independent parts. In the first part the concept of an (m,c)-system for a set of linear forms is introduced, and a lower bound is obtained for the algebraic complexity of the computation of (m,c)-systems on algebraic circuits of a special form. In the second part, the notion of an -independent set of boolean functions is introduced and a lower bound is obtained for a certain complexity measure for circuits of boolean functions computing -independent sets. As a corollary it is shown that the standard algorithm for multiplying matrices or polynomials may be realized by a circuit of boolean functions in a way that is optimal with respect to a selected complexity measure.Translated from Zapiski Nauchykh Seminarov Leningradskogo Otdeleniya Mathematicheskogo Instituta im. V. A. Steklova Akad. Nauk SSSR, Vol. 60, pp. 38–48, 1976. Main results presented December 12, 1974 and May 29, 1975.The author would like to express his deep appreciation to A. O. Slisenko for his help.  相似文献   
924.
Statistics of random world lines in a fixed electromagnetic field are considered. The equation for a vectorj i is obtained. This vector describes the density of random world lines in a pure ensemble. It is shown that in the two-dimensional space-time this equation coincides with the Dirac equation to within the terms of the order of magnitude of (/L)2 ( is Compton's wavelength,L is a typical length of the system).  相似文献   
925.
A study was made of the temperature dependences of the flow stress 0.1 (T) and of the critical shear stress cr(T) of Cu-15% A1-(1–2)% Co, Cu-8% A1-(2–2.8)% Co, and Cu-4% A1–2% Co alloys containing noncoherent intermetallic particles. In the case of single crystals at temperatures 77–673° K there was a good agreement between the theoretically calculated values of the Orowan hardening and those found experimentally, so that the dependence cr(T) was governed by the temperature dependence of the shear modulus G(T). For polycrystalline samples the usual dependence of the mechanical propertiesties on the grain size was not observed. At temperatures from 77 to 473–573°K the dependence 0.1 (T) was similar to the dependence G(T) and a good agreement was observed between the theoretically calculated dispersion hardening effects with those found experimentally. At temperatures T > 473–573°K the deformation was influenced greatly by grain-boundary glide, which enhanced the dependence 0.1 (T) compared with that expected theoretically.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 85–91, June, 1980.  相似文献   
926.
An investigation was made of the kinetics of changes in the flow stress 0.1, modulation period , and electrical resistivity in the course of ageing of Cu-Ti, Cu-Ti-Al, Cu-Ti-Zn, and Cu-Ti-Ga alloys. There were no dispersion hardening effects during the early stages of the precipitation, corresponding to the = const condition. An increase in 0.1. was observed during the stage of coagulation of the secondary phases. The increase in the flow stress was described using a theory of hardening by coherent particles of the new phase but it did not agree with the theory of hardening of alloys exhibiting spinodal precipitation.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 81–87, May, 1980.  相似文献   
927.
The method of transition probabilities is used to calculate the line width of ferromagnetic resonance in a medium with an inhomogeneous saturation magnetization. It is shown that in addition to linear (with respect to the Fourier components of the function describing inhomogeneities) terms, the perturbation Hamiltonian must include also quadratic terms. The frequency dependence of the contribution of the porosity to H is fundamentally different from the frequency dependence of the magnetic anisotropy contribution. This anisotropy contribution Ha() decreases on increase in the frequency and has a maximum at = (2/3)M, whereas the porosity contribution Hp increases on increase in the frequency and vanishes at = (2/3)M.deceasedTranslated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp.48–52, December, 1980.  相似文献   
928.
We consider the mechanism of macroscopic polarization of semiconducting plates owing to the interaction of free carriers with an impurity level, in which role the level of the residual impurity of compensated semiconductors may appear. This mechanism, in combination with the diffusion-drift mechanism of polarization, results in additional dispersion of the real () and imaginary () parts of the dielectric permittivity, this being particularly significant for semiconductors of thickness smaller than the screening length Ls of free carriers. The character of the behavior of and depends on the relation between the Maxwell relation time M and the times of carrier capture: c and ejection e by an impurity center. For cetm and (/Ls) e/c1 the dispersion of and is the same as for thick plates (/Ls1). For c m e and (/Ls)e/c1 the () curve has a characteristic kink in the region 1/e, indicating additional absorption associated with the ejection of carriers into the surface region.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 11–13, October, 1981.  相似文献   
929.
930.
Conclusions Our studies have revealed that the spectral density of low-frequency current fluctuations in GaAs tunnel diodes can be described by the relation Wi(u, F)=f2 (u)mF, where the nonlinear function f2(u) is not proportional to the rms of excess diode current. The flicker nature of the current noise in tunnel diodes derives from conductance fluctuations on the p-n junction, which occur in tunnel diodes as well as in low-noise transistors at frequencies ranging from near zero to a few kiloheriz and produce noise of almost the same absolute intensty in both kinds of devices.Leningrad Polytechnic Institute. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 20, No. 5, pp. 777–784, May, 1977.  相似文献   
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