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101.
The semileptonic decay width of heavy baryons such as (Λ
b
→ Λcev) has been estimated in the framework of a nonrelativistic field theoretic quark model where four component quark field
operators along with a harmonic oscillator wave function are used to describe translationally invariant hadronic states. The
present estimation does not make an explicit use of heavy quark symmetry and has a reasonable agreement with the experimentally
measured decay width, polarisation ratio and form factors with the harmonic oscillator radii and quark momentum distribution
inside the hadron as free parameters. 相似文献
102.
R.E. Showalter D.B. Visarraga 《Journal of Mathematical Analysis and Applications》2004,295(1):191-210
A distributed microstructure model is obtained by homogenization from an exact micro-model with continuous temperature and flux for heat diffusion through a periodically distributed highly-heterogeneous medium. This composite medium consists of two flow regions separated by a third region which forms the doubly-porous matrix structure. The homogenized system recognizes the multiple scale processes and the microscale geometry of the local structure, and it quantifies the distributed heat exchange across the internal boundaries. The classical double-diffusion models of Rubinstein (1948) and Barenblatt (1960) are obtained in non-isotropic form for the special case of quasi-static coupling in this homogenized system. 相似文献
103.
Totally fissured media in which the individual cells are isolated by the fissure system are effectively described by double porosity models with microstructure. Such models contain the geometry of the individual cells in the medium and the flux across their interface with the fissure system which surrounds them. We extend these results to a dual-permeability model which accounts for the secondary flux arising from direct cell-to-cell diffusion within the solid matrix. Homogenization techniques are used to construct a new macroscopic model for the flow of a single phase compressible fluid through a partially fissured medium from an exact but highly singular microscopic model, and it is shown that this macroscopic model is mathematically well posed. Preliminary numerical experiments illustrate differences in the behaviour of solutions to the partially fissured from that of the totally fissured case. 相似文献
104.
Summary Consider a solution to a second-order pseudo-parabolic equation with sufficiently smooth time-independent coefficients in
a cylindrical domain. If it vanishes on the cylindrical surface for all times and if its restriction to a fixed instant belongs
toC
2+a
, then its pointwise values decay exponentially as t→∞ while its Dirichlet norm grows expontially as t→−∞. Similar conclusion
still hold for solutions to non-homogeneous equations under non-homogeneous boundary conditions provided the free term and
the boundary data posses these asymptotic behaviors.
Work of the second named author was partially supported by N.S.F. Grant No. GP-19590.
Entrata in Redazione il 29 gennaio 1971. 相似文献
105.
H.D. Hollis Showalter Ellen M. Berman Judith L. Johnson Jerry L. Atwood William E. Hunter 《Tetrahedron letters》1985,26(2):157-160
Reaction of 1,4-dihydroxy-9,10-anthracenedione bistosylates and bistriflates with a range of common nucleophiles is discussed. 相似文献
106.
Ernest Wenkert Timothy D.J. Halls Lawrence D. Kwart Göran Magnusson H.D.Hollis Showalter 《Tetrahedron》1981,37(23):4017-4025
Syntheses of the alkaloids eburnamonine and quebrachamine are presented in which the non-tryptamine portion of the skeleta is constructed by the β-oxycyclopropylcarboxylate preparation-fragmentation route. A similar reaction scheme is utilized for the synthesis of the alkaloids vincadine and epivincadine. 相似文献
107.
D'Sa RA Wang Y Ruane PH Showalter BM Saavedra JE Davies KM Citro ML Booth MN Keefer LK Toscano JP 《The Journal of organic chemistry》2003,68(2):656-657
We report the facile preparation of O2-sulfonated diazeniumdiolates and mechanistic investigation of their reactions with representative nucleophiles. This new class of compounds extends the range of O2-substituted diazeniumdiolates available for potential applications in research and medicine. 相似文献
108.
109.
Raman and resonance-Raman spectra of the I?3 ion isolated within CsI crystals have been studied using 647 nm and 488 nm exciting radiation. Sample temperatures between 300 and 20 K have been used. Eleven overtones of the symmetric stretching mode (nν1) have been observed in the resonance-Raman spectrum excited by the 488 nm Ar+ laser line. Bands centred at 153, 170, 264 and 304 cm?1 have been assigned as ν3, 2ν2, ν1+ν3 and 2ν3(Σ+) respectively. The remaining structure between the nν1 lines has been assigned as due to combinations of these lines with the lattice vibrations of the CsI crystal. 相似文献
110.
In this paper exact asymptotic formulae are found for singularvalues of the Cauchy operator and the logarithmic potentialtype operator (on a bounded domain), as well as their productswith Bergman's projection. It is shown that these spectral characteristicsdetect geometric properties of a domain (area and the lengthof the boundary). The hypothesis "can we hear the shape of adrum", from a paper by J.M. Anderson, D. Khavinson, and V. Lomonosov[Spectral properties of some integral operators arisingin potential theory, Quart. J. Math. Oxford (2) 43 (1992)387-407], is correct in the above sense. 1991 Mathematics SubjectClassification: 47B10. 相似文献