Sesquiterpene lactones of new stereostructural types from laser trilobum

The newly established structures of sesquiterpene lactones from Laser trilobum showed that these lactones belong among the stereostructural types of germacranolides, guaianolides, eudesmanolides and elemanolides.     

A theory of inelastic behavior of materials Part I. Ideal inelastic materials

Archive for Rational Mechanics and Analysis -     

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New books

     

Effects of polymer–fiber interactions on rheology and flow behavior of suspensions of semi-flexible fibers in polymeric liquids

Rheological properties of suspensions of fibers in polymeric fluids are influenced by fiber–polymer interactions. In this paper, we investigate this influence from both experimental and modeling standpoints. In the experimental part of this investigation, we have changed the fiber–polymer interactions by treating the surface of the fibers. The resulting effects are observed using scanning electron microscopy and dynamic mechanical analysis techniques and quantified from the measurements of the viscosity in the start-up of shear flows and dynamic tests in the linear viscoelastic range region. The results are interpreted with the help of a mesoscopic rheological model developed for suspensions of fibers in viscoelastic fluids.     

Generalized reflective cum coreflective classes in Top and Unif

The Herrlich's problem from [8] whether there are nontrivial classes of topological spaces that are both almost reflective or injective and almost coreflective or projective, is investigated in a more general setting using cone and cocone modifications of the classes used in the problem. We look also at the problem for uniform spaces. Typical results: There is no nontrivial multiprojective and orthogonal class of topological spaces; There is a reflective class of uniform spaces that is almost coreflective in Unif.Work on this paper was initiated while the first author was a C.N.R. visitor of the University of L'Aquila. Partial financial assistence by Charles University Grant 349/1994 is also acknowledged.     

Minimal polynomial and the rank of principal submatrices of a matrix

The following theorem is proved: If r is the degree of the minimal polynomial of a matrix A then there exists a principal submatrix of A with order r and rank at least r-1.     

A theory of non-radiative transfer of excitation energy in solids

A theory of non-radiative transfer of excitation energy in solids is elaborated for the case of strong interaction of an atom of the sensitizer and an atom of the activator with the oscillations of the whole crystal lattice.     

On periodical behaviour in societies with symmetric influences

We propose a simple model of society with a symmetric functionw(u, v) measuring the influence of the opinion of memberv on that of memberu. The opinions are chosen from a finite set. At each step everyone accepts the majority opinion (with respect tow) of the other members. The behaviour of such a society is clearly periodic after some initial time. We prove that the length of the period is either one or two.     

Long range substituent effects relfected in the 13C NMR spectra of allyl alcohols and their derivatives

Acylation of allyl alcohols induces strong carbon shifts, shielding γ and deshielding δ effects. These shifts are a consequence of through-bond polarization of the olefinic carbons. Allyl ethers show similar, but milder perturbations. The olefinic carbon shifts reveal a strong concentration dependence. This effect, in greatly reduced form, is also observed in non-oxygenated alkenes. Hydrogen bonding by alcohols enhances the chemical shift difference in olefinic carbon pairs by increased polarization.