Deformation of styrene—divinylbenzene copolymers and hypercrosslinked polystyrenes during solvent adsorption and desorption

An automated procedure was developed for monitoring fast changes in the size of spherical samples of polymers during their contact with a solvent or drying. The kinetics of bulk deformation in these processes was studied for a series of cross-linked polymers, viz., gel-type and porous styrene—divinylbenzene copolymers and poly(divinylbenzenes), and hypercrosslinked polystyrenes. Gel, macroporous, and hypercrosslinked polystyrenes are substantially different in the rate, mechanism, and degree of swelling, which is associated with the principal differences in their physical structures. An unusual effect of a sharp decrease followed by a temporary increase in the volume of porous polystyrene and poly(divinylbenzene) materials were observed during desorption (evaporation) of organic solvents. Water desorption is accompanied by an excessive bulk compression of porous granules giving rise to negative deformations, which gradually relax to the state equilibrium for the dry polymer. The results of dynamic desorption porometry (for water desorption) are indicative of a bimodal size distribution of micropores in hypercrosslinked polystyrene. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 467–476, March, 2007.     

On quadratic differentials on multiply connected domains that are perfect squares

The paper considers the problem on extremal decomposition of a multiply connected domain G ⊂ ℂ in the case where the associated quadratic differential is a perfect square. It is shown that in the case considered, the value of the functional for this extremal decomposition is the least one in a certain class of decompositions. Bibliography: 10 titles. Dedicated to the 100th anniversary of G. M. Goluzin’s birthday __________ Translated from Zapiski Nauchnykh Seminarov POMI, Vol. 337, 2006, pp. 113–133.     

Interdiffusion of hydroxyl groups and of doping additions between a bearing pipe and a deposited layer in billets of fiber light guides

Using Raman spectroscopy, a quantitative analysis of the distribution of OH⁻ ions on the boundary between a bearing pipe and a glass layer deposited from chlorides in billets for quartz fiber light guides is carried out. Water penetrated into the light-reflecting shell to a depth of several tenths of a millimeter, depending on the composition of the doping layer (i.e., ultimately on the temperature of the depsoition process). A. F. Ioffe Physical-Technical Institute, Academy of Sciences of Russia, 26, Politekhnicheskaya St., St. Petersburg, 194021, Russia. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 4, pp. 548–550, July–August, 1997.     

Electronic phase separation in a low-temperature tetragonal phase of lanthanum-strontium cuprates according to 139La NQR data

A nonuniform electron density distribution is observed in La_{1−x− y} Nd_ySr_xCuO₄ and La_1−x−y Eu_ySr_xCuO₄, and long-lived magnetic fluctuations in these compounds are studied. The dynamics of the magnetic fluctuations depends strongly on the magnetic properties of the rare-earth ions, which stabilize the low-temperature tetragonal phase. Pis’ma Zh. éksp. Teor. Fiz. 67, No. 5, 344–349 (10 March 1998)     

Change in the nature of the Ni diffusion mechanism on the Si(111) surface with adsorption of Co atoms

The diffusion of Ni on a Si (111) surface is investigated by LEED and Auger electron spectroscopy. It is found that, in contrast to the process on the initially clean Si (111)−7×7 surface, on Si (111) surfaces with submonolayer Co coverages the nature of the Ni transport mechanism changes at a temperature of about 750 °C, and the Ni surface diffusion coefficients increase sharply below this temperature. Pis’ma Zh. éksp. Teor. Fiz. 66, No. 9, 611–614 (10 November 1997)     

Application of a separating transformation to estimates of inner radii of open sets

We obtain solutions of new extremal problems of the geometric theory of functions of a complex variable related to estimates for the inner radii of nonoverlapping domains. Some known results are generalized to the case of open sets. __________ Translated from Ukrains’kyi Matematychnyi Zhurnal, Vol. 59, No. 10, pp. 1313–1321, October, 2007.