Refinement of wave-functions of valence electrons of diamond using experimental compton profiles

Refinement of wave-functions of valence electrons of diamond is performed using the available experimental Compton profiles obtained by the data on X-ray and γ-ray scattering. The wave-function of valence electrons is taken in the approximation of sp³-hybridization. Atomic scattering factors predicted by the refined wave-functions are in a satisfactory agreement with the experimental data (Göttlicher et al.).     

Crystallo-optical properties of the SmxTb1−xFeO3 orthoferrites

The paper reports the results of X-ray diffraction studies as well as the angular dependences of rotation of the plane of polarization and birefringes of the Sm_xTb_1−xFeO₃ crystals (x = 0; 0.2; 0.4; 0.55; 0.8; 1). The polar diagrams presented for the plane (001) have the symmetry mm2, while for (110), the symmetry lowers up to the axis of a second order. The gyrotropic measurements made have allowed us to refer the Sm_xTb_1−xFeO₃ to a planar class of an orthorhombic crystal system with the space group C_2v⁹–Pn2a, class mm2. – The magnitude of birefringence for the Sm_xTb_1−xFeO₃ is found to be sensitive both to a crystallographic direction and a composition, the greatest values stand for (110). For (001), a non-monotonous birefringence variation with the composition is observed. The angles between optic axes, calculated by the birefringence magnitudes, are in fair agreement with gyrotropic data for the compositions x = 0.55 – 1.     

On temperature dependence of Debye-Waller factor in V3Si in the temperature range from 8 to 293 K

The temperature dependence of the Debye-Waller factors of vanadium and silicon in V₃Si and that of the X-ray Debye temperature are obtained from the integral intensities of X-ray reflection measured at 11 temperatures ranging from 8 K to 293 K. It shown that the breaks on these curves are observed at T_br = 21.7 K. This fact allows to assume that the phase transition in this compound is accompanied by the rapid change of the atomic vibration frequencies.     

Thermodynamic functions of (InP)x(InAs)1-x from 5 to 300 K

Temperature dependence of the heat capacity of the solid solutions (InP)_x(InAs)_1-x has been investigated over the temperature range from 5 to 300 K. Solid solution samples with x = 1; 0.8; 0.6; 0.4; 0.2; 0.1; 0 produced by means of crystallization from the melt the following annealing and diffusion in the powder at temperature close to solidus have been studied. The absolute values of enthalpy H, entropy S, Gibbs free energy Z as well as their deviations from the additive values have been obtained for the (InP)_x(InAs)_1-x system from the analysis of the thermodynamic properties of the solid solutions of the III–V compounds at low temperatures. The curves for the characteristic temperatures (T) of the solid solutions studied show that the change of the character of the phonon spectrum is negligible, the thermodynamic functions are close to additive, the influence of the enthalpy and entropy of mixing on the deviations from the additive enthalpy and entropy of the alloys is insignificant.     

Thermochemical investigation of guest-host interactions in Werner clathrates of type [Ni(4-Etpy)4(NCS)2]·nG (G=naphthalene derivatives)

The stoichiometry of thermal decomposition and the thermochemistry were studied for [NiL₄(NCS)₂] (I) as a host complex, and for its clathrates of type [NiL₄(NCS)₂]·2G, where L=4-ethylpyridine and guest molecule G=1-methylnaphthalene in clathrate (II), 1-chloronaphthalene in (III) or 1-bromonaphthalene in (IV). For I, the loss of volatile components proceeds in three steps (–2L, –L, –L); the first steps for II–IV also involve the release of G (–2G, –2L). DSC and X-ray powder measurements indicated a phase transition in the host lattice, and allowed differentiation of the escape of G and L molecules. The enthalpy changes give the following sequence of thermodynamic stability for the studied chlathrates: I>II>III.     

Directed growth of pure phosphatidylcholine nanotubes in microfluidic channels

The morphology of self-assembled phospholipid membranes (e.g., micelles, vesicles, rods, tubes, etc.) depends on the method of formation, secondary manipulation, temperature, and storage conditions. In this contribution, microfluidic systems are used to create pure phosphatidylcholine (PC) micro- and nanotubes with unprecedented lengths. Tubes up to several centimeters in length and aligned with the long axis of the microchannel were created from spots of dry films of 1,2-dilauroyl-sn-glycero-3-phosphocholine (DLPC), 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC), and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC). These high aspect ratio structures, which, to our knowledge, represent the first examples of extended tubes formed from pure PC lipids, were examined by fluorescence microscopy, electron and optical microscopy, and optical manipulation tools (i.e., a laser trap and laser scalpel) to characterize structure and stability. In particular, the tubular structure was confirmed by observation of fluorescent dyes that were sequestered within the aqueous cavity or within the phospholipid tube. Compared to other phospholipid tubes, the tubes formed from PC lipids in microfluidic channels show high mechanical stability and rigidity that depend on tube size, age, and storage conditions.     

Differential scanning calorimetry of irradiated polymers

DSC was used to study the influence of fast electron irradiation on the molecular mobility and melting of semicrystalline polymers and copolymers of ethylene and of fluorocopolymer. The heat capacity-temperature dependences obtained in the range from 100 K to 500 K revealed the specific features of the irradiation effect on four relaxational transitions associated with the appearance of segmental motion in different molecular elements of the disordered regions in the polymer. The pronounced dependence of the radiation stability of crystallites on the thermal prehistory of the object under study was found. The results were interpreted on the basis of the decisive role of the molecular mobility and free volume for the predominance of the radiation cross-linking of the molecules. Correlations were established between the characteristics of the thermal transitions and the mechanical properties of the irradiated polymers.     

Degradation of Cellulose Triacetate upon Irradiation with Accelerated Electrons

The radiation-chemical yield G of degradation of cellulose triacetate was calculated from the viscometric data. The radiation dose providing formation of cellulose triacetate with the modified structure and with the desired reactivity was determined.__________Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 3, 2005, pp. 520–521.Original Russian Text Copyright © 2005 by Kasimova, Mnatsakanov, Sirota.