Thermal motion in SrTiO3at room temperature: Anharmonic or disordered?
A high-resolution structural study of strain-free SrTiO3 in its cubic phase at room temperature shows that the oxygen thermal motion is not very significantly anharmonic.
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Flows of Nematic Liquid Crystals
The first liquid crystal was discovered about a century ago by Reinitzer (1888), who observed that the organic crystal cholesteryl benzoate melted at a temperature of 145°C yielding a turbid fluid which, upon the further addition of heat, became clear at a temperature of 179°C. The turbid fluid was found to exhibit op…
Theory of nuclear spin relaxation by translational self-diffusion in liquid crystals: Nematic phase
The theory of intermolecular nuclear spin relaxation by translational self-diffusion in liquid crystals is developed. Torrey's treatment of simple liquids is extended and modified for the liquid-crystalline phases by taking into account the anisotropy of the molecular motion, the elongated molecular shape, and the spi…
A Geometrical Model for Chemically Bonded TMS and PDS Phases
A geometrical model is developed for monomeric TMS and PDS phases that are chemically bonded to silica. Using experimental data for maximum surface coverage and considering amorphous silica as a collection of distorted crystals, we calculate that each nm2 of the silica surface contains 2.3 modified hydroxyl groups, 1.…
Molecular structure of diaquo-.alpha.,.beta.,.gamma.,.delta.-tetraphenylporphinatoiron(III) perchlorate and perchlorato-.alpha.,.beta.,.gamma.,.delta.-tetraphenylporphinatoiron(III). Two new structural types for iron(III) porphyrins
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTMolecular structure of diaquo-.alpha.,.beta.,.gamma.,.delta.-tetraphenylporphinatoiron(III) perchlorate and perchlorato-.alpha.,.beta.,.gamma.,.delta.-tetraphenylporphinatoiron(III). Two new structural types for iron(III) porphyrinsM. E. Kastner, W. Robert Scheidt, Toshio Ma…
Effect of free‐volume fluctuations on polymer relaxation in the glassy state
Abstract As is most clearly seen in the results of A. J. Kovacs on the volumetric relaxation following changes in temperature, the initial relaxation in polymers is surprisingly rapid, considering how slowly relaxation becomes later. We suggest that this rapid initial relaxation is due to relaxing molecular rearrangem…
Coprecipitation of borate-boron with calcium carbonate.
The behavior of borate-boron in a calcium bicarbonate parent solution during the precipitation of calcium carbonate has been studied experimentally. The amount of borate-boron coprecipitated with calcium carbonate is proportional to the concentration of borate-boron dissolved in a parent solution, and this relationshi…
Structure of the quenched form of polypropylene
Abstract X‐ray diffraction has been used to further investigate the quenched form of polypropylene. The diffractometer traces were analyzed by a mathematical peak separation procedure which assumed a combined Cauchy and Gaussian shape for the peaks. The results confirmed that the quenched form contains about 60% of am…
Determination of the number of cross‐links in a protein gel from its mechanical and swelling properties
Abstract The relation between the chemical structure of a protein and the physical properties of a heat‐set gel of that protein has been investigated. The physical properties of the gel are determined by means of mechanical experiments in which the viscoelastic properties of the gel are determined in terms of the stor…
Defect model of the smectic A-nematic phase transition
It is shown that phase transitions in three dimensions breaking up an ordered state by polar defect lines can be modelled on the xy model, at least if the interaction of the lines is only steric. The analogy is established for a lattice model by means of a xy high-temperature expansion for spin 1/2. The defect model i…
The vibronic theory of ferroelectricity
A review of the foundation, developments and latest results of the so-called vibronic theory of ferroelectricity—a new approach to the microtheory of spontaneous polarization and ferroelectric phase transitions in crystals incorporating the interactions of electrons with nuclear displacements (vibronic interactions),…
Physical studies of nematic azoxybenzenes. I. Magnetic susceptibilities and the order parameter
The anisotropy of the magnetic susceptibility and the density of the series of nematic p,p′-di-n-alkyl and p,p′-di-n-alkoxy azoxybenzenes are reported as a function of temperature. Assuming that the molecules are effectively axially symmetric the anisotropy of the susceptibility is a direct measure of the nematic orde…
Chemical energy accommodation at catalyst surfaces. Flow reactor studies of the association of nitrogen atoms on metals at high temperatures
The fate of the energy release in highly exoergic surface-catalysed chemical reactions is of considerable fundamental interest and influences catalyst volatilization/sintering, the aerodynamic heating of hypersonic glide vehicles subject to bombardment by atomic nitrogen and atomic oxygen, etc. To provide the first av…
Properties of some rodlike polymers in solution
Abstract The properties of poly (1, 4‐phenylene terephthalamide) ( PPTA ), Kevlar, and a poly(benzobisoxazole) ( PBO ) in solution are investigated. Molecular characterization using light scattering and viscometry on dilute solutions shows PBO and PPTA to have a rodlike conformation. Both are prone to interchain aggre…
One-dimensional dielectric-flexoelectric deformations in nematic layers
A general theoretical framework for a unified description of various flexoelectric effects in uniform d.c. electric fields is developed. With this framework four basic geometries are studied theoretically as follows : a) homeotropic layer under the action of a d.c. electric field normal to the optic axis ; b) homeotro…
Blends of poly(ϵ‐Caprolactone) with poly(vinyl chloride). I. Morphology
Abstract The morphology of blends of poly(ϵ‐caprolactone) (PCL) with poly(vinyl chloride) (PVC) was investigated. The observations made with the optical microscope and electron microscopes indicate that for the blends rich in PCL, the samples are almost completely filled with spherulites composed of lamellas radiating…
Properties and Structure of the Binary Tellurite Glasses Containing Mono- and Di-valent Cations
MO1/2-TeO2 (M: Li, Na, K, Rb, Cs, Ag, Tl), MO-TeO2 (M: Be, Mg, Ca, Sr, Ba, Zn, Cd, Pb) 2成分系のガラス化範囲及びガラスの密度, 屈折率, 熱膨張, 赤外吸収スペクトルを測定した. TeO2含量の多い組成では, 熱膨張係数の大きさ, paratelluriteとの赤外吸収スペクトルの比較により, Te4+はひずんだ四方錐配位をとり, おそらく層状網目を形成するものと推定した. TeO3三方錐のみを含む結晶の赤外吸収を基にガラス中のTeO3三方錐のTe-O伸縮振動を帰属した. その吸収強度の変化から, 1価の系では33mol%付近から, MgO,…
Molecular tilt in the smectic C phase : a zigzag model
We have collected data concerning the molecular tilt angle of 4 smectic C compounds, presenting a second order transition to a smectic A phase. We have completed these data by direct measurements, using the conoscopic technique, for the tilt angle of the optical axis, and the X-ray technique, to follow the varying thi…
Dielectric Study of Ferroelectric Properties in Chiral Smectic C
Measurements of electric permittivity, and polarization are reported for chiral liquid crystal DOBAMBC. Dielectric hysteresis was found. Temperature-variations of spontaneous polarization and relaxation time are studied. The dielectric properties of chiral smectic C and those of crystalline ferroelectrics are compared.
Physical studies of nematic azoxybenzenes. II. Refractive indices and the internal field
The ordinary refractive index and the birefringence are reported for two homologous series of nematic liquid crystals, the p,p′-di-n-alkyl and p,p′-di-n-alkoxy azoxybenzenes. It is found that the high-frequency dielectric anisotropy is proportional to the anisotropy of the magnetic susceptibility. For axially symmetri…