Effect of Microwave Irradiation on the Cross-Linking of Polyvinyl Alcohol

The possibility of dehydration (cross-linking) of polyvinyl alcohol upon microwave irradiation of thin polymer films was examined. The properties of polyvinyl alcohol samples treated by convection heating and irradiation were compared. Immobilization of polyvinyl alcohol on polymer matrices by microwave irradiation was studied.     

Anreicherung von Spuren Seltener Erden aus Mineralwässern durch Ionenaustausch

In the described analysis of mineral waters, after the throughflow of the sample through a column with Dowex 50 WX 12 in H⁺ form, the main cations are first eluted by 1.6 N HCl and then the rare earths by 6 N HCl. The latter are separated by ion-exchange chromatography on Dowex 50WX8 in NH₄ ⁺ form, the elution being performed with ammonium citrate pH 4.19. The presence of rare earths in the eluate was ascertained spectrophotometrically by means of their reaction with xylenol orange in the presence of cetylpyridinium bromide. In mineral waters from the West-Bohemian spa region it was possible to find traces of trivalent La, Ce, Pr, Nd, Sm + Gd, Y, Dy, Ho, Er, Tm, Yb and Lu.     

Aggregation and photoisomerization of amphiphilic crown-ether styryl dye in monolayers at the interface

The molecules oftrans-isomer of styryl dye1a, containing the benzo-18-crown-6 moiety and the methoxybenzothiazole residue with theN-octadecyl substituent, were shown to form stable, highly ordered monolayers at the water/air interface. Increasing the surface pressure of the monolayer results in the formation of the H-aggregated molecules of compound1a. The H-aggregates tend to dissociate to the monomerictrans-form, when the monolayer forms in the Langmuir-Blodgett film (LB film). The light irradiation of the LB films leads to the partially reversibletrans-cis-photoisomerization of compound1a, whose efficiency is much lower than that observed in an acetonitrile solution of1a. The aggregation of cis-1a isomers in the LB film is suggested to hamper the reversecis-trans-isomerization. The aggregation oftrans-1a molecules in the LB films does not occur in air, but, after dipping in an aqueous solution, molecules of the LB film slowly form J-aggregates. A model of the structural organization oftrans-1a molecules in the LB films was proposed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2490–2496, October, 1996.     

Restrictions on exact current correlation functions and reliability of sum-rule results

Criteria of reliability are studied for results obtained within the sum-rule approach in QCD and in some toy models. The criterion of validity of the approximation for current correlation functions based on operator-product expansion within Borel sum rules, suggested previously in the literature, is critically reexamined. A new criterion of validity of a perturbative approximation that makes use of the Källen-Lehmann representation and finite-energy sum rules is proposed. The stability of criteria against small variations in expansion coefficients is investigated in an exactly solvable model and in QCD.     

Modification of solids with polymer nanolayers as a process for manufacture of novel biomaterials

The results of study on the chemical deposition of polymeric coatings of a nanoscale thickness on porous and flat inorganic matrices and encapsulation of nano-and microparticles in polymer shells are discussed. Procedures for the deposition of homogeneous defect-free coatings are detailed by using polytetrafluoroethylene, polyaniline, and their derivatives as examples. The matrices modified with nanosized polytetrafluoroethylene and polyaniline layers are promising biomaterials for one-step isolation of nucleic acids from complex biological mixtures (cell and tissue lysates, whole blood, plant feedstock), as well as for high-performance chromatography of proteins and other biopolymers. Approaches to the fabrication of polymer shells on luminescent nanocrystals of (CdSe)ZnS via the inclusion of the nanocrystals in micrometer-sized particles based on acrolein-styrene copolymers and the formation of polymer shells directly on nanoparticles are discussed. It was shown that polymer-functionalized luminescent nanocrystals hold promise as bioanalytical reagents.     

Effect of fillers and solvents on the properties of polystyrene coatings

The mechanism of coating formation from solutions of atactic polystyrene in xylene and carbon tetrachloride has been investigated. It has been established that, as the filler content increases, in coatings formed from polystyrene solutions containing an evaporating solvent the growth of the internal stresses and the thermophysical characteristics is characterized by similarity of slope, as distinct from the case of coatings obtained from systems containing a polymerizing solvent. It is shown that the nature of the solvent has an important effect on the character of the interaction at the polymer—filler interface and on the structure and properties of the coatings.Kucherenko Central Scientific-Research Institute of Structural Design. Institute of Physical Chemistry, AS USSR, Moscow. Translated from Mekhanika Polimerov, Vol. 4, No. 6, pp. 1127–1129, November–December, 1968.     

The linear theory of dislocations and disclinations in elastic shells

A stress state of a thin linearly elastic shell containing both isolated as well as continuously distributed dislocations and disclinations is considered using the classical Kirchhoff–Love model. A variational formulation of the problem of the equilibrium of both a multiply connected shell with Volterra dislocations as well as shells containing dislocations and disclinations distributed with a known density is given. The mathematical equivalence between the boundary-value problem of the stress state of a shell caused by distributed dislocations and disclinations and the boundary-value problem of the equilibrium of a shell under the action of specified distributed loads is established. A number of problems on dislocations and disclinations in a closed spherical shell is solved. The problem of infinitesimally deformations of a surface when there are distributed dislocations is formulated.