Spin-spin interactions of Ce3+ ions in the elpasolite crystal Cs2NaInCl6

The EPR method is used to study at T=4.2 K crystals of Cs₂NaInCl₆:Ce³⁺ (1 mol %) at which have elpasolite structure. A solitary cubic Ce³⁺ center and three types of Ce³⁺-Ce³⁺ pairs were observed, for which the spin-spin interaction parameters D and E were determined. It is established that deformation of the local structure results in a shift {Δg} of the pair relative to the g-factor of the solitary center. Models of the solitary center and the three types of Ce³⁺-Ce³⁺ pairs are discussed, as well as the nature of the spin-spin interactions in the pairs. The non-dipole nature of the interactions is established. Possible chains for the creation of an indirect exchange between the Ce³⁺ ions are considered. Fiz. Tverd. Tela (St. Petersburg) 39, 62–67 (July 1997)     

X-ray diffractometry and electrical conductivity of the ceramics LaSrAl(Cu,Ni)O4

A continuous series of solid solutions LaSrAL_1−x Me_xO₄ (Me = Cu, Ni) has been investigated by x-ray diffractometry and by electrical conductivity measurements. The results are of interest from the standpoint of the theory of close-packing, percolation theory, and the theory of the cooperative Jahn-Teller effect. Fiz. Tverd. Tela (St. Petersburg) 39, 985–990 (June 1997)     

Synthesis and structure—activity relationships of cyclopropane-containing analogs of pharmacologically active compounds

The review summarizes information on cyclopropane as an independent pharmacophore group and as a fragment for modification of pharmacological activity level of medicines used in practice. The advantages of a cyclopropane fragment over its bioisosteres are that, on the one hand, this fragment imposes conformational rigidity on the molecules of physiologically active compounds and, on the other hand, the replacement of acyclic terminal and “linker” groups with a cyclopropane fragment increases the metabolic stability of the target structures and extends the scope of their therapeutic action.     

Homogenization of the Neumann problem for the Lamé equations of linear elasticity in domains with a periodic system of channels of small length

The problem of homogenization is considered for the solutions of the Neumann problem for the Lamé system of plane elasticity in two-dimensional domains with channels that have the form of rectilinear cylinders of length ε ^q (ε is a small positive parameter, q = const > 0) and radius a _ɛ. The bases of the channels form an ε-periodic structure on the hyperplane {x ∈ ℝ²: x ₁ = 0} and their number is equal to N _ɛ= O(ɛ⁻¹) as ε → 0. Under the limit condition lim on the parameters characterizing the geometry of the domain, the weak H ¹-limit of the generalized solution of this problem is found. __________ Translated from Trudy Seminara imeni I. G. Petrovskogo, No. 25, pp. 310–322, 2005.     

Effect of high pressure on rearrangement of organosilicon peroxides

Conclusions The thermal rearrangement of organosilicon peroxides to alkoxysiloxanes proceeds with a substantial decrease in the volume activation effect.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 484–485, February, 1978.     

New rearrangement of triphenyl(triphenylsilylperoxy)germane catalyzed by nucleophiles

The peroxide Ph₃GeOOSiPh₃ rearranges in THF solution at ca. 20°C in the presence of fluoride ions or triethylamine to the germasiloxane, Ph₂(PhO)GeOSiPh₃, while thermal rearrangement of the same peroxide gives Ph₃GeOSi- (OPh)Ph₂. The reaction of tris(trimethylsilylmethyl)stannyllithium (I) with one equivalent of the germasiloxane Ph₂(PhO)GeOSiPh₃ in THF yields (Me₃SiCH₂)₃SnPh, (Ph₂GeX)_x and Ph₃SiOLi. Analogous products have been obtained in high yield in the reactions of I with the peroxides Ph₃GeOOSiPh₃ and Ph₃GeOOSiMe₃. It is assumed that the initial step of these reactions is rearrangement of the peroxides, catalyzed by (Me₃SiCH₂)₃Sn anions, with the formation of the germasiloxanes Ph₂(PhO)GeOSiR₃ (R = Ph or Me). The mechanism of this catalytic rearrangement of unsymmetrical peroxides is discussed.     

The adhesive properties of polyfluoroolefin films modified by direct-current discharge

The influence of the treatment of various structures polyfluoroolefine films by the direct-current discharge at the anode and cathode on the properties of the surface (the value of the contact angles of wettability, work of adhesion, and surface energy and its polar and dispersive components) is studied. Measurements of the peel strength of plasma-treated films are conducted. It is shown that the direct-current discharge treatment makes it possible to substantially increase the peel strength of the polyfluoroolefin films.