Chemical polarisation of electrons in redox reactions

In the system Ti(III)? H₂O₂? RH (RH is isobutyric acid or isopropanol) the concentration and polarisation of the β-radical decreases during the reaction, while the polarisation of the α-radical increases with the decrease of the α-radical concentration. The second fact is not in accordance with Adrian's model of inducing the polarisation in redox systems during the radical recombination process.     

A Bernasconi model for constructing ground-state spin systems

A Bernasconi model for a one-dimensional chain of quantum particles is considered. It is shown that searching for the ground state of such a quantum system is equivalent to searching for binary sequences with minimum energy levels of the side lobes of the aperiodic autocorrelation function (ACF). A review and new results regarding the construction of such binary sequences are presented.     

Transitions to the relaxor and dipole-glass states in mixed crystals of the potassium dihydrogen phosphate family

Regularities of the formation of the relaxor and dipole-glass states in the systems of mixed ferroelectric-antiferroelectric crystals of the potassium dihydrogen phosphate family are discussed. The problems related to the crystal structure, lattice dynamics, and relaxation processes in dipole glasses and relaxors implemented in systems of this type are considered.     

Deuterated hen egg-white lysozyme crystals: Optimization of the growth conditions and morphology

Deuterated and protonated tetragonal lysozyme crystals are grown using the hanging-drop vapor-diffusion method. The size of the lysozyme crystals grown is determined as a function of the concentration of sodium chloride used as a precipitant. It is found that crystallization leads to the formation of lysozyme crystals with three different habits. Morphological and X-ray diffraction analyses of the deuterated and protonated lysozyme crystals demonstrate that, despite the different habits, all the crystals grown belong to the tetragonal crystal system. The simple forms of lysozyme crystals are revealed. It is shown that the habits of the lysozyme crystals are determined by the specific combinations of simple forms. The mechanisms responsible for the formation of lysozyme crystals with different habits are discussed.     

Neutron studies of the structure and dynamics of Rb1 − x (NH4)xI mixed crystals

The structural and dynamical properties of the x-T phase diagram of the system of Rb_{1 ? x} (NH₄)_xI mixed crystals is of great interest, because such solid solutions are almost free of internal stresses due to almost equal ionic radii of ammonium and rubidium. The x-T phase diagram of Rb_{1 ? x} (NH₄)_xI is studied on samples with ammonium concentration ranging from 0.01 to 0.73 over the temperature range from 15 to 300 K by the methods of powder neutron diffraction and inelastic incoherent neutron scattering. The results obtained by powder neutron diffraction show that the α-β phase transition at low temperature is rather extended and occurs at the ammonium concentrations x = 0.50 and 0.66. The region of orientational state glass is determined by inelastic incoherent neutron scattering at the concentrations x = 0.29 and 0.40 at the temperature T = 20 K.     

Thermal behavior of polymers prepared using the tri-<Emphasis Type="Italic">n</Emphasis>-butylboron–<Emphasis Type="Italic">p</Emphasis>-quinone system

Thermal behavior of polymers [poly(methyl methacrylate), poly(methyl acrylate), polystyrene] prepared in the presence of tri-n-butylboron and a series of p-quinones was studied. The heat resistance of the polymers increases with an increase in the inhibition constant of the p-quinone taken for the synthesis. The enhancement of the heat resistance of the polymer is due to a decrease in the amount of weak bonds and to the formation of associates.     

Isotopic effect in Brillouin light-scattering spectra of a Cs5H3(SO4)4 · xH2O crystal

A Brillouin scattering study of the behavior of hypersonic longitudinal acoustic phonons in crystalline pentacesium trihydrogen tetrasulfate Cs₅H₃(SO₄)₄ · xH₂O (PCHS) and its deuterated analog Cs₅D₃(SO₄)₄ · xD₂O (DPCHS) at temperatures ranging from 420 to 120 K is reported. The effect of deuteration on the crystal lattice dynamics is investigated. The differences in the behavior of hypersonic acoustic phonons in the PCHS and DPCHS crystals suggest the existence of a hydrogen isotope effect in both the high-and low-temperature phases. A possible model of the isotopic effect in the high-temperature phase is discussed. An analysis is made of the acoustic response of the PCHS and DPCHS crystals in the region of the transition to the glasslike phase.     

Dielectric properties of single-crystal deuterated triglycine sulfate (DTGS) in ultra-weak low-and infra-low-frequency electric fields

The complex permittivity ɛ* is studied with separate readings for ɛ′ and ɛ″ at low and infralow frequencies and ultraweak fields. The effective conductivity λ is determined. An Arrhenius dependence is observed for ln ɛ′(1/T), ln ɛ″(1/T), and ln λ(1/T), both in the paraphase and in the polar phase. It is proposed that the conductivity of crystalline DTGS in the paraphase is an ion jump conductivity. Fiz. Tverd. Tela (St. Petersburg) 41, 1073–1075 (June 1999)     

Cutting-off effect at reflection–transmission of acoustic waves in anisotropic media with sliding-contact interfaces

The specific feature of the interface, which maintains sliding contact between elastic media, is that it can be impervious to the wave field existing in one of the adjoined materials. As a result, reflection–transmission of plane acoustic waves at the sliding-contact interface may enjoy the cutting-off effect, which implies that neither bulk, nor inhomogeneous modes are being transmitted at particular angles of incidence. The necessary and sufficient criteria for this phenomenon are obtained for a binary structure, constituted by two elastic half-spaces in sliding contact, and for a sandwich structure with sliding-contact interfaces between the enclosed layer and the substrates. In the generic case of unrestricted anisotropy (triclinic materials), the criterion for cutting-off in a binary structure involves acoustic parameters of solely that of the half-spaces, which contains the incident mode, and proves to be independent of an adjacent medium. The frequency-dispersive criterion for the absence of transmission through a triclinic layer in the sliding-contact sandwich structure is independent of substrates. By appeal to the Stroh formalism, the cutting-off conditions in a binary and a sandwich structure are further elaborated under the assumption that one of the half-spaces, or a layer, is orthorhombic, and its two symmetry planes are parallel, respectively, to the plane of incidence and to the sliding-contact interface with arbitrary adjacent media. It is shown that the transmission cut-off in a binary structure is necessarily accompanied by the absence of mode conversion at reflection, but the reverse is not true. The angles of incidence which give rise to these effects are determined in terms of elastic coefficients. Transmission cut-off through an orthorhombic layer comes about at an arbitrary angle of incidence, related to guided-modes range in the layer, for the corresponding aperiodic infinite set of the frequency values. Relations for the coefficients of reflection and transmission at the sliding-contact interface between two orthorhombic half-spaces are obtained in concise form, expressed solely via normal components of the partial Stroh-normalized traction amplitudes. Provided that the adjoined orthorhombic half-spaces in sliding contact are identical, the same value of wave-vector tangential projection, which stipulates transmission cut-off at the incidence of, say, the fast mode, entails total transmission at the incidence of the slow mode.