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Within the macroscopic Landau-de Gennes approach, we examine the Gaussian normal mode fluctuations of semi-infinite nematic liquid crystals in a regime of critical wetting. It is argued that surface free-energy potentials that strongly suppress the long-range nematic order favor the appearance of bound biaxial nematic-director fluctuation modes, located in the domain occupied by the thermodynamic phase wetting the wall. Instead, substrates enhancing the orientational order promote the existence of uniaxial nematic-director local excitations. Close to the phase coexistence temperature both types of local exciations are strongly softened as compared to their bulk counterparts and acquire characteristic cusplike low-energy spectra. These spectrum peculiarities are directly connected to the critical behavior of the mean-field interface position and can provide a valuable insight on the nature of surface interactions and critical wetting phenomena in nematic liquid crystals. Possible changes in the local director mode properties resulting from the critical interface position fluctuations and order electricity effects are also discussed., 13 pages, RevTex, 3 eps figures. Phys. Rev. E, submitted

We have synthesized and characterized by IR, UY,1H, and13C NMR spectroscopy new spiropyrans based on 2-thioxo-3 phenyl-5,5-dimethyl-1,3-oxazolidine. We have studied their photochromic properties in 2 propanol at -80°C. In the electronic spectra of photo-induced farms, we have detected two long-wavelength absorption bands in the 370–438 and 480–677 nm region.

We report on onset of a surface induced phase in droplets of OOBA liquid crystals desplaying optical properties typical for the smectic-A state. The latter state does not exist in the bulk phase diagram of the system. The surface phase appears in a temperature range close to the bulk nematic- smectic-C transition temperature TNC . The results are interpreted through a Landau-de Gennes type model with additional δ function terms.

Our microtextural as well as depolarized light scattering analyses of 4-n-octyloxybenzoic acid liquid crystal droplets provide evidence for a possible smectic A ordering induced by the free surface. This appears near the bulk smectic C-nematic transition at T SCN. A simple mean field analysis, based on a Landau-de Gennes-Benguigui free energy functional with an additional surface parameter K s, allows, in principle, the possibility for a smectic A surface phase at temperatures slightly above T SCN.

We present arguments in favor of the suggestion that the Marshall-Peierls phase relationships and the Lieb-Mattis level ordering survive the frustration in the squarelattice Heisenberg antiferromagnet for relatively strong frustration parameters.

Lorsqu'on etudie les polaritons de surface dans les metaux magnetiques il est necessaire de tenir compte de la dispersion spatiale de la permittivite dielectrique e et de la susceptibilite magnetique μ. On obtient les relations de dispersion pour les polaritons de surface, en supposant que les dispersions spatiales et temporelles sont importantes pour e et μ

A new method for calculation the energy of S = 1/2 Heisenberg antiferromagnet /AFM/ in Gutzwiller state is developed. The method is analogous to low-temperature expansion /LTE/ in statistical physics

The diamagnetic susceptibility of a twinning plane at temperatures slightly higher than the localized superconductivity temperature T c as well as the heat capacity jump at T = T c are calculated. The possibility of an appreciable increase of the superconductivity temperature in small particles containing twinning planes is studied.

The process of microfiltration carried out in the regimen of destruction of concentrational polarization layer decreases considerably the retention of admixture proteins in filtrational concentration of virus suspension. This allows the membrane technology to be used not only for concentration but also for profound purification of the virus-containing allantoic fluid for preparation of inactivated influenza virus. Using the microfiltration method, vaccine preparations of any influenza virus strain may be obtained without loss of biological activity. The resultant vaccine is highly immunogenic and safe for man. The filtration technology makes it possible to restore the preparations discarded because of low virus titres or excess protein content.