Materials Literature
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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…
A weak electrolyte model for the mixed‐alkali effect on electrical conductivity and ionic mobility in glass was developed for the dilute foreign alkali region. The basic assumptions are (a) that alkali transport in single‐alkali glasses is due to a small concentration of mobile species and (A) adding small amounts of…
When homothallic cells of Schizosaccharomyces pombe were plated on agar sporulation medium, a few residual divisions were usually observed before induction of conjugation and sporulation. Four cells resulting from the last two residual divisions were usually lined; the "four-lined-cell" formed. Each four-lined-cell co…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSupermolecular structure and thermodynamic properties of linear and branched polyethylenes under rapid crystallization conditionsL. Mandelkern, M. Glotin, and R. A. BensonCite this: Macromolecules 1981, 14, 1, 22–34Publication Date (Print):January 1, 1981Publication History…
Experimental results are reported which show for the first time a transfer inside pairs of ions after their selective excitation by a pulsed laser. This transfer is studied in Pr3+ : LaF3 by monitoring the time dependence of an up-conversion fluorescence. The results show that two mechanisms must be considered, depend…
In a binary isobaric diagram there appears an intermediate smectic phase between a monomolecular smectic A phase and a bimolecular one. By means of several techniques evidence is given for this new mesophase with a liquid-like short range ordering. Some considerations about the long range structure of this novel fluid…
The discotic liquid crystalline mesophase of p-n-hexa-hexyloxytriphenylene was studied using deuterium NMR spectroscopy. Spectra of two selectively deuterated isotopic species were recorded : (i) in which all aromatic positions were substituted, and (ii) in which the substitution was made in the α-carbon side-chains.…
We present an analytic calculation of the normal modes of distortion induced by a small transverse A.C. electric field on a ferroelectric liquid crystal close to its transition temperature Tc between the smectic A and C* phases. These normal modes are superpositions of electric polarization and angular molecular disto…
Iron(III) and manganese(III) porphyrins catalyse the oxygen transfer from iodosylbenzene to aromatic substrates to yield phenolic products; the resultant p-methoxyphenol or p-cresol exhibits a marked NIH shift.
An electron beam with a diameter below 1 nm has been used to measure the resolution of PMMA. Test patterns are written in 30 nm thick PMMA layers coated onto 60 nm thick membrane substrates. Both lateral scattering of electrons in the resist and backscattering from the substrate are negligible for these samples. Preli…
The energy levels of the nickel atom in all of its stages of ionization, as derived from the analyses of atomic spectra, have been critically compiled. In cases where only line classifications are reported in the literature, level values have been derived. Electron configurations, term designations, J-values, experime…
« Nematic lyotropic » phases are anisotropic fluids made of aggregates of amphiphilic molecules dispersed in water. Their nematic behaviour (flow, orientation in a magnetic field) is related to the orientational correlations between the aggregates which are anisotropic particles of finite dimensions. Therefore they ar…
The oil-soluble degradation products formed in heated samples of oil containing zinc di(n-, iso- or s-butyl)dithiophosphate (ZDTP) additives have been identified using 1H and 31P nuclear magnetic resonance spectroscopy. The final degradation product in each case is S,S,S-trialkyltetrathiophosphate, SP(SR)3. The interm…
Furutobeite, (Cu, Ag)₆PbS₄ is a new sulfide species discovered at the Furutobe mine, Akita Prefecture, Japan. It occurs only as minute (< 0.3 mm) grains intimately associated with stromeyerite, galena, sphalerite and tennantite in bornite from upper part of the stratabound sulfide ore zone consisting of sphalerite, ga…