An importance sampling procedure for estimating failure probabilities of non-linear dynamic systems subjected to random noise

The first passage problem for linear and non-linear oscillators excited by white and coloured noise are considered. An iterative variance reduction scheme is used in a framework of a measure change in the space of sample functions according to the Girsanov transformation, which is based on introducing a Markov control process. It is proved that a good approximation to the optimal stochastic control process can be obtained from an equivalent white noise excited linear oscillator. It is shown that this leads to very accurate estimates of the failure probability of the original system. The advantage of this procedure is that expressions for the parameters of the equivalent linear system and the design point oscillations, which are needed to find the control process, are available analytically. The number of samples, the variance of the failure probability estimates and the computational time are reduced significantly compared with direct Monte Carlo simulations.     

Laser–induced thermocapillary deformation of a thin liquid layer

An equation that describes the profile of laser–induced thermocapillary deformation of the thin layer of an absorbing liquid is obtained. Numerical estimates of the deformation profile are in agreement with experimental data. It is shown that with increase in the radiation power, the deformation depth of the liquid layer increases and leads to its rupture.     

Regio- and Stereoselective Synthesis of (Z)-2-Chloro-2-phenyl-1-propylethenyltellanes

Russian Journal of Organic Chemistry - The regio- and stereoselective reaction of tellurium tetrachloride with 1-phenylpent-1-yne was used to develop efficient methods of synthesis of...     

3-Polyfluoroalkyl-1,5-diphenylpyrazoles in Suzuki Cross-Coupling Reactions

Russian Journal of Organic Chemistry - Suzuki cross-coupling was used for modification of 3-polyfluoroalkyl-1-phenylpyrazoles at the position C4. The synthesized 4-bromo- and 4-phenyl derivatives...     

Study of melanin localization in the mature male Calopteryx haemorrhoidalis damselfly wings

Damselflies Calopteryx haemorrhoidalis exhibiting black wings are found in the western Mediterranean, Algeria, France, Italy, Spain and Monaco. Wing pigmentation is caused by the presence of melanin, which is involved in physiological processes including defence reactions, wound healing and sclerotization of the insect. Despite the important physiological roles of melanin, the presence and colour variation among males and females of the C. haemorrhoidalis species and the localization of the pigment within the wing membrane remain poorly understood. In this study, infrared (IR) microspectroscopy, coupled with the highly collimated synchrotron IR beam, was employed in order to identify the distribution of the pigments in the wings at a high spatial resolution. It was found that the melanin is localized in the procuticle of the C. haemorrhoidalis damselfly wings, distributed homogeneously within this layer, and not associated with the lipids of the epicuticle.     

Synthesis of functionally substituted benzaldehydes

A new method of synthesis of functionally substituted benzaldehydes by catalytic debromometoxylation of dibromomethylarenes with benzaldehyde dimethyl acetal has been suggested. Anhydrous zinc chloride has been used as a catalyst. Being soft Lewis acid, it formed no strong complex with aldehyde group and other functional groups. The initial acetal has been readily recovered by the treatment of benzaldehyde isolated from the reaction mixture with trimethyl orthoformate.     

Properties of electrorheological fluids based on nanocrystalline cerium dioxide

Effect of conditions of nanocrystalline cerium dioxide preparation from aqueous solutions on its composition and physicochemical properties and on dielectric characteristics of CeO₂ suspensions in polydimethylsiloxane PMS-20 and the magnitude of electrorheological effect for these suspensions has been analyzed. Relationship between physicochemical properties of CeO₂ nanopowders and polarization and functional characteristics of electrorheological fluids derived therefrom has been established.     

Sorption and cytotoxicity of zinc on hydroxyapatite

The preparation, physicochemical properties, and cytotoxicity of zinc-containing hydroxyapatites (HAP) were considered for further using HAP as carriers for zinc-containing drugs and radiopharmaceuticals.