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Abstract A new type of chiral solid mesophase was obtained by evaporating the solvents from solutions or jellies of chiral 12-hydroxyoctadecanoic acid (12HOA). The mesomorphic solids exhibited some optical properties characteristic of a helicoidal mesophase: (1) spherulitic or Schlieren texture under a polarizing micr…
The program for the synthesis of nonabsorbing thin film systems by the method of gradual evolution [J. A. Dobrowolski, Appl. Opt. 4, 937 (1965)] has been extended to include new features and to handle absorbing materials. In the analysis mode the new program calculates the spectral transmittance, reflectance, and abso…
The x-ray diffraction pattern of liquid ZnCl2 has been measured. The distances and coordination numbers derived from the data indicate that the Cl− ions are closed packed, and that the Zn2+ ions are located in the tetrahedral holes typical of such a structure.
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXT[Rh10As(CO)22]3-. Example of encapsulation of arsenic by transition-metal carbonyl clusters as illustrated by the structural study of the benzyltriethylammonium saltJose L. VidalCite this: Inorg. Chem. 1981, 20, 1, 243–249Publication Date (Print):January 1, 1981Publication H…
Ruled gratings of 0.33–3.33-μm wavelength fabricated with SiO, SiO2, and In2O3-SnO2 are used to study the topographical effects of the surface on the twisted nematic (TN) alignments of liquid crystals (LC’s). The types of LC’s are Schiff base, azoxy, biphenyl, biphenyl ester, and phenyl cyclohexane. All of the LC’s, e…
Manganese(III) tetraphenylporphin MnIII(tpp)Cl catalyses the specific oxidation of olefins to ketones by O2 in the presence of [NBu4][BH4]; the latter reagent further reduces the ketones to the alcohols.
Nous examinons le comportement de solutions diluées de « bâtons durs », en présence de diverses perturbations extérieures : a) Près d'une paroi plane agissant de façon purement stérique (pas d'adsorption), la concentration en monomères est réduite sur une distance L (L, longueur des bâtons). Nous évaluons le profil de…
The properties and morphology of the cholesteric « blue » phase (BP) are discussed in terms of the « quasicrystalline » (QC) hypothesis, which states that the BP is ordered with three-dimensional translational periodicity. The lattice parameter of the « crystalline » BP is comparable to optical wavelengths, giving ris…
Liquid‐crystalline Heterocycloalkanes. I. Synthesis and Properties of Substituted 1,3‐Dioxanes The synthesis of 2,5‐disubstituted 1,3‐dioxanes is described, their melting and clearing points and their physical properties (dielectric anisotropy, viscosity, transition enthalpies, optical birefringence) are investigated.…
The optical absorption, emission, and excitation spectra for the Eu 5+ ion in the alkali halides have been investigated at room temperature. It was found that the magnitude of the 10Dq splitting of the 4f 6 5d configuration into its t 2g and e g components caused by the cubic crystalline field follows the spectrochemi…
Yeast enolase as prepared by current procedures is inherently chemically homogeneous, though deamidation and partial denaturation can produce electrophoretically distinct forms. A true isozyme of the enzyme exists but does not survive the purification procedure. The chemical sequence for both has been established. The…
Dielectric and light scattering spectroscopy are the most sensitive methods for the direct observation of low-frequency excitations in incommensurate phases. In several cases they have been successfully used for the observation of amplitudon and phason modqs. Whereas the amplitudon below the normal-incommensurate tran…
Measurements we have made of electric permittivities have revealed new pre-transitional effects in nematics with cyano end groups. These effects have been found to be related to the discontinuity in the mean permittivity at TNI observed for these nematics and they have been attributed to pre-transitional changes in th…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTKinetics of doping and degradation of polyacetylene by oxygenJ. M. Pochan, D. F. Pochan, H. Rommelmann, and H. W. GibsonCite this: Macromolecules 1981, 14, 1, 110–114Publication Date (Print):January 1, 1981Publication History Published online1 May 2002Published inissue 1 Jan…
The tunneling of the Wannier exciton from its metastable free state to the stable self-trapped state is described in the context of the multi-phonon nonradiative transition. The escape path through the adiabatic potential barrier is determined by a variational method: the tunneling is assumed to occur along a trial in…
X-ray diffuse scattering studies of one dimensional conductors (TMTSF) 2ReO4 and (TMTSF)2NO3 reveal the formation of low temperature superstructures which might involve an ordering of the counter ions ReO-4 and NO-3. The superstructure reflections are characterized by wave vectors q = (1/2, 1/2, 1/2) for the perrhenat…
The x-ray-diffraction spectra of ${\mathrm{Ba}}_{2}$Na${\mathrm{Nb}}_{5}$${\mathrm{O}}_{15}$ have been investigated by means of a precession camera between room temperature and 500\ifmmode^\circ\else\textdegree\fi{}C, across the orthorhombic-tetragonal transition near ${T}_{\mathrm{I}}=300$\ifmmode^\circ\else\textdegr…
Raman scattering and optical-depolarization measurements have been employed in investigations of the ferroelectric phase transition in $\mathrm{K}{\mathrm{Ta}}_{1\ensuremath{-}x}{\mathrm{Nb}}_{x}{\mathrm{O}}_{3}$ in the limit $x<~0.05$. The critical niobium concentration for which ${T}_{c}\ensuremath{\approx}0$ K w…
Order in the orientations of bond angles in bulk smectic liquid crystals is investigated. A simple model which couples in-plane bond orientations to a tilt degree of freedom is solved in the mean-field approximation. In addition to the usual smetic-$A$ and smetic-$C$ phases, there is an untilted hexatic phase, with lo…
A method for the determination of carbon in soils and soil extracts is described. It involves the dry combustion of samples in a standard tube furnace and the direct titrimetric determination of the evolved carbon dioxide as carbonic acid in a sodium hydroxide trap. Liquid samples are dried onto a siliceous earth bed…