On the equilibrium shapes of a conducting drop in a uniform and nonuniform electric field

The equilibrium shape of a drop in the electrostatic field of a point charge and a point dipole is asymptotically calculated in terms of the dimensionless deformation of the shape and a ratio between the drop’s radius and the distance to the point charge (dipole). Irrespective of the degree of nonuniformity of the field, the prolate spheroidal deformation (typical of the uniform field) is shown to be the main reason for the change in the equilibrium shape of the spherical drop. When the nonuniformity of the field grows, the equilibrium shape becomes more and more asymmetric and different from the spheroidal one. This, all other things being equal, may influence the critical conditions for the instability of the drop’s surface against an induced charge. It follows from the aforesaid that the drop in the field of the dipole will be the first to undergo instability with the electrostatic pressure on the drop being the same.     

Modelling and design optimization of textiles via homogenization

This article deals with optimization of large structures of linear elastic material with contact modeled by Robin-type boundary conditions. Homogenization is used to represent the structures as homogenous elastic bodies and is essential for formulation of the optimization problems, where optimization of the effective properties is considered. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Pd-catalyzed asymmetric reactions using resorcinol- and hydroquinone-based P∗,P∗-bidentate diamidophosphites

Readily available isomeric bisdiamidophosphites with P∗-stereocentres have been prepared using resorcinol and hydroquinone as simple and cheap starting materials. Palladium catalytic systems containing these P∗,P∗-bidentate ligands afforded 99% and 70% ees in asymmetric allylic substitution and desymmetrization processes, respectively. The influence of the precatalyst, substrate, nucleophile, and solvent on the enantioselectivity is discussed.     

Instability of a charged droplet in an inhomogeneous electrostatic field of a thin rod

The problem of stability of oscillations of a charged droplet in an inhomogeneous electrostatic field of a thin charged rod is investigated in the nonlinear formulation using the asymptotic expansion in two small parameters, namely, the dimensionless equilibrium droplet strain and the ratio of the droplet oscillation amplitude to the droplet radius. It is shown that, when the droplet charge is less than the Rayleigh critical charge, in the inhomogeneous electrostatic field the droplet instability implementation mechanism remains the same as for the charged droplet in the field of a point charge. As the oscillation mode number increases, the critical field parameter reaches saturation tending to the horizontal asymptotics. The longer the rod, the higher the level of the asymptotics. As the rod length increases, the amplitudes of the related droplet oscillations and the increments of the unstable droplet oscillations in the electrostatic field of the rod decrease.     

Instability of a Charged Droplet in an Inhomogeneous Electrostatic Field of a Rod of Finite Thickness

The instability of a charged droplet of an ideal liquid in an inhomogeneous electrostatic field of a rod of finite thickness maintained at a constant electrostatic potential is investigated within the framework of analytic asymptotic calculations. It is shown that the mode amplitudes and the drop oscillation frequencies increase with the rod thickness. The critical conditions of instability of the droplet reduce by several times as compared with the critical conditions of implementation of its instability in the electrostatic field of an infinitely thin filament maintained at a constant electrostatic potential. An analytic dependence between the charge and field parameters, critical for implementation of the instability of a charged droplet in an inhomogeneous electrostatic field and dependent on the rod thickness, is found.     

Analysis of Characteristics of the Sensing Elements for the Fiber-Based Evanescent Wave Spectroscopy in the Mid-IR

Characteristics of the sensing element of a fiber sensor for evanescent wave mid-IR spectroscopy have been studied within the electromagnetic theory of fiber waveguides by using the problem of determining the concentration of aqueous acetone solutions as an example. A multimode chalcogenide fiber was used as a sensing element. It has been shown that the selective excitation of the fiber modes may provide the possibility to increase the sensitivity of the fiber sensing element, decrease the minimum detectable concentration of a substance in a solution, and enhance the range of measured solution concentrations.     

A new method for preparing carbenes

Russian Chemical Bulletin -     

Charged particle motion in the field of a short laser pulse of relativistic intensity

The electron motion in the field of the laser radiation of relativistic intensity was analyzed using the Lorentz force. In the laser pulse field, an initially rest electron does not move along trajectories such as “figure eight”. At relativisitic intensities, the electron oscillations in an optical field are significantly anharmonic.     

Nonsimple relationships between the P-chiral diamidophosphite and the arylphosphine moieties in Pd-catalyzed asymmetric reactions: combinatorial approach and P,P-bidentate phosphine-diamidophosphites

A small family of P,P^∗-bidentate C₁-symmetric ligands containing 1,3,2-diazaphospholidine rings with stereogenic phosphorus atoms has been prepared. Palladium catalytic systems with these phosphine-diamidophosphites afforded 95% and 63% ees in asymmetric allylic substitution and desymmetrization processes, respectively. The influence of the nature of both the phosphine and diamidophosphite moieties of these compounds on the enantioselectivity is discussed. The ‘mixed-ligand approach’ in Pd-catalyzed asymmetric allylation with participation of some new P^∗-monodentate diamidophosphites and PPh₃ is also considered.     

Polymeric film formation in spin coating

The results of numerical modeling of polymeric film formation under mass force action are presented. The instability of non‐Newtonian liquid front edge at the initial stage of flow over a disk is studied. The quasi‐stationary shape of the liquid film (in front edge vicinity) speading over the surface is determined for certain rheology laws. At the modeling of the second stage of coating flow, the special attention was paid to the effects connected with the two‐dimensional character of the flow. The impact of rheological properties of a liquid on the free surface shape was studied using codes that calculate the two‐dimensional non‐stationary flow of non‐Newtonian liquid. The factors that determine the final shape of polymeric coating free surface are discussed.