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991.
Charles F Osgood 《Journal of Number Theory》1981,13(4):515-540
An effective proof of Shidlovski's Theorem is presented. The proof utilizes partial differential operators. A number of generalizations of Shidlovski's Theorem are proven, including results about approximation at more than one point. Additionally, partial differential equations are considered. The new methods give a particularly direct proof of Shidlovski's Theorem. 相似文献
992.
X-irradiation of a single crystal of 2-chloro-2,2'-spirobis(1,3,2-benzodioxaphosphole) yields the oriented PVI radical anion formed by electron capture. Directions of maximum values of the magnetic hyperfine tensors of 31P, 35Cl, and 37Cl are coincident and oriented along the P—Cl linkage, indicating an octahedral structure with the unpaired electron and chlorine in axial positions. 相似文献
993.
Charles S. Peskin 《纯数学与应用数学通讯》1989,42(1):79-113
The goal of this paper is to derive the fiber architecture of the left ventricle from first principles. The principles used are (i) mechanical equilibrium, (ii) a stress tensor that is the sum of a hydrostatic pressure and a fiber stress, (iii) the assumption that fiber tubes have constant cross-sectional area along their length, (iv) axial symmetry, and (v) the approximation that the thickness of the ventricular wall is small in comparison with the other wall dimensions. From these hypotheses, it is deduced that the cardiac muscle fibers are approximate geodesics on a nested family of toroidal surfaces centered on a degenerate torus in the equatorial plane of the heart. (Exact geodesics are ruled out by the theory.) Formulae are derived for the fiber surfaces and the fiber-angle distribution through the wall, and a differential equation is derived for the shape of the middle surface of the left ventricle. The results are in substantial agreement with experimental observations. 相似文献
994.
Michael E. Jung Richard W. Brown Jeffrey A. Hagenah Charles E. Strouse 《Tetrahedron letters》1984,25(34):3659-3662
Cycloaddition of the benzopyrone 10b with 1,1-disubstituted alkenes 12, 14, and 16 produces fair yields of the lactones 13, 15, and 17, AB-ring analogues of the anthracyclines. 相似文献
995.
The effect of temperature T and weight-average molecular weight M?w on the rate of spreading of polystyrene melts on plane solid surfaces has been examined. The activation energy E of spreading was estimated to be 25.2 ± 3 kcal/mole, which is of the same magnitude as the activation energy for flow of polystyrene melts. The rate of spreading was found to be inversely proportional to M?w raised to the 1.5 power. This rate of spreading, measured as the time rate of increase in the liquid–solid contact area, dA/dt, could be expressed as where γ1v is the melt surface tension and θd and θs are the dynamic and static contact angles, respectively. The numerical value of K has been calculated to be (6.025 ± 3.693) × 10?14 in the temperature range of 110–260°C and for the values of M?w from 2000 to 37000. 相似文献
996.
The air oxidation of 1-benzyl-3, 4-dihydroisoquinolines is shown to be a self-sensitized photo-oxidation proceeding via singlet oxygen. 相似文献
997.
998.
999.
Charles W. Jefford Gérald Bernardinelli Jean-Claude Rossier Shigeo Kohmoto John Boukouvalas 《Tetrahedron letters》1985,26(5):615-618
4-Methyl-4-naphthoquinol and its 5-methyl derivative on treatment with per-Amberlyst 15 are converted to the corresponding cis-2,3-epoxides in high yields. The latter structure was determined by X-ray crystallography. 相似文献
1000.
Light scattering from nonequilibrium electron-hole plasma excited by picosecond laser pulses in GaAs
A picosecond dye laser is used to excite electron-hole plasma of density between 1018 to 1019 cm-3 in GaAs. The plasma density and distribution function within ? 20 psec of excitation is probed by Raman scattering. The lineshape of the single particle excitation spectra of the plasma can be explained only by assuming that the electron distribution function is in nonthermal equilibrium. 相似文献