Fixed-point theorems for S-KKM maps

A number of new fixed-point results are presented for S-KKM self maps. Also the notion of essentiality for S-KKM maps is introduced.     

Dead cores of singular Dirichlet boundary value problems with ϕ-Laplacian

The paper discusses the existence of positive solutions, dead core solutions and pseudodead core solutions of the singular Dirichlet problem (ϕ(u′))′ = λf(t, u, u′), u(0) = u(T) = A. Here λ is the positive parameter, A > 0, f is singular at the value 0 of its first phase variable and may be singular at the value A of its first and at the value 0 of its second phase variable. This work was supported by grant no. A100190703 of the Grant Agency of the Academy of Sciences of the Czech Republic and by the Council of Czech Government MSM 6198959214.     

The influence of the entrance channel mass asymmetry on the reaction mechanism

We have tried to investigate the influence of the entrance channel mass asymmetry on the reaction mechanisms associated with heavy ion collisions. Two systems, one very much asymmetric (O+Mo) and the other one almost symmetric (Cr+Fe), were studied in detail by measuring evaporation residues, deep inelastic collision products and fission fragments. An important fraction of the fragments observed in the Cr+Fe system exhibits all the characteristics of fission fragments. The analysis of these data seems to indicate that these fission like products are most likely emitted by a long lived composite system having not reached full statistical equilibrium for all the degrees of freedom. As a consequence, the fusion cross section for this symmetric system is too low as compared to predictions based on a critical distance approach for fusion, whereas the asymmetric system (O+Mo) is well understood in term of the same model.     

Electronic properties of tin dichalcogenides (SnS2 and SnSe2)

Using Phillips and Van Vechten's theory the homopolar gap (E_h), ionic gap (E_c) and Penn gap (E_p) have been derived for the layered compound semiconductors SnS₂ and SnSe₂. The values of E_p so derived have been found to be in agreement with the values obtained from the Grimes-Cowley modification of the Penn model, and also with the reflectance spectra of the respective materials. Using the above data the Phillips ionicity has been calculated and the octahedral coordination of SnS₂ and SnSe₂ has been discussed on the basis of the calculated value of ionicity. The bond electronic polarizability has been evaluated using Chemla's approach and the values so obtained have been found in agreement with the values obtained from the Clausius-Mossottirelation. The Varshni formula has been shown to explain fairly well the temperature dependence of energy gap and the constants involved have been derived. The calculated isobaric temperature gradient of E_g[($\text{?E}{}_{\mathrm{g}}\text{?T)}{}_{\mathrm{p}}$] has been found to be in accordance with the reported values, and the electron lattice interaction has been evaluated.     

Unsteady state heat flow in epidermis and dermis of a human body

We investigate the unsteady state temperature distribution in human skin where subcutaneous tissues are not present. The mathematical model is employed for a onedimensional unsteady state case, taking the blood mass flow rate and metabolic heat generation variable with respect to the position in the dermis. The metabolic heat generation depends on the tissue temperature. The thermal conductivity is taken constant but different in two layers. The problem has been solved using Laplace transform and Bessel functions. Numerical results for a simple case are discussed.     

Mixed convective non-steady 3-dimensional micropolar fluid flow at a stagnation point

The problem of mixed convective non-steady three dimensional flow of a micropolar fluid near the stagnation point of a blunt nosed body has been discussed. The governing set of differential equations are solved using the Finite Element Method. The velocity and microrotation distribution are shown graphically to depend upon four parameters namely the micropolar parameter, Grashof number, buoyancy parameter and the degree of acceleration. The conclusions are quite interesting from the application point of view. Received on 4 June 1997     

Line narrowing beyond natural linewidth in radiation matter interaction

A review of the various linear and nonlinear methods used to obtain resolution beyond natural linewidth is given. Based on the lecture given at the International Symposium on Theoretical Physics, Bangalore, November 1984.     

Resolution beyond natural linewidth via flourescence in modulated beams

A new method is proposed for obtaining spectral resolution beyond the natural linewidth using excitation by a laser beam whose intensity is weakly modulated in time at a low frequency ν. Th modulated fluorescence at 2ν, is shown to posses subnatural linewidth. The resolution of two lines lying within the natural linewidth of each other is explicitly considered.