Materials Literature
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ABSTRACT Most biominerals appear to be composites of organic material and mineral. Whether biosilica is such a composite is unresolved because of a lack of evidence for such organic components. We present evidence that organic material exists within diatom biosilica and can be extracted using HF/NH 4 F solutions from…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTCatalysis by heteropoly compounds. 20. An NMR study of ethanol dehydration in the pseudoliquid phase of 12-tungstophosphoric acidKwan Young Lee, Takeo Arai, Shinichi Nakata, Sachio Asaoka, Toshio Okuhara, and Makoto MisonoCite this: J. Am. Chem. Soc. 1992, 114, 8, 2836–2842P…
This article presents a survey of the literature on X-ray diffraction by mesomorphic comb-like polymers. Special emphasis is placed upon two points: it is often possible to study the localization of the backbone in the smectic phases by considering the intensities of the Bragg reflections from the layers. It is also p…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTOrigin of orientation phenomena observed in layered Langmuir-Blodgett structures of hairy-rod polymersStefan Schwiegk, Thomas Vahlenkamp, Yuanze Xu, and Gerhard WegnerCite this: Macromolecules 1992, 25, 9, 2513–2525Publication Date (Print):April 27, 1992Publication History P…
The phenomenon of pressure-induced crystalline →amorphous phase transformation in ice Ih has been studied with constant-pressure molecular dynamics calculations. It was found that although the temperature dependency of the transformation pressure resembles that of the extrapolated melting curve, the actual mechanism i…
Ferroelectric thin films are playing a growing role as key elements in variety of devices. For various techniques of ferroelectric thin film preparation, the sol-gel processing is one of the most promising. In comparison with different deposition techniques, we survey the intrinsic advantages and the recent improvemen…
Electron hopping in redox polymer-modified electrodes requires coincident ion movement to maintain electroneutrality, and transport effects can arise due to either process. In this paper, the equation for diffusion/migration by electron hopping is used with the classical Nernst-Planck equation for mobile ionic species…
It is well known that charge carrier mobilities μ in molecularly doped polymers, determined by transient photoconductivity experiments, depend on the temperature T, the mean distance p between dopant molecules and the electric field E. Recently introduced deconvolution procedures have made possible the systematic anal…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTHigh-spin chemical bonding of metal monocarbonothioyl and -carbonyl [MCS and MCO] (M = Sc, Ti, V, Cr, Cu)G. H. JeungCite this: J. Am. Chem. Soc. 1992, 114, 9, 3211–3213Publication Date (Print):April 1, 1992Publication History Published online1 May 2002Published inissue 1 Apr…
An experimental study of formative times and the Topler's constant approach to modeling the breakdown event is presented. The authors deal with the dependence of formative time and Topler's constant on the macroscopic parameters of the insulation. Results obtained were statistically treated and the Topler's constant d…
We observed a spontaneous transition from a vertical chevron texture to a striped texture (striped ``bookshelf'' texture) in a surface-stabilized film of ferroelectric liquid crystal mixture (ZLI 4237-000, from E. Merck). The transition takes place gradually, at temperatures more than 20 \ifmmode^\circ\else\textdegree…
The copper(I) complexes [Cu(4-Xdmpz)] 3 (where X = H, Cl, Br, I and CH 3 ; dmpz = 3,5-dimethylpyrazolate) and the copper(II) complexes [Cu(4-Xdmpz) 2 ] x have been synthesized and characterized. Qualitative solubility, infrared spectroscopic, and differential scanning calorimetric studies are reported for all complexe…
A simple atomistic model with two harmonic potentials between layers of atoms describes surface relaxations equivalent to those found as kink solitary waves in ferroelastic crystals. The parameters of the model are expressed in terms of the entropy term in a Landau potential and the Ginzburg gradient energy. We discus…
Ideally oriented to complex a metal ion, the three carbonyl groups of triolide 1 are parallel and pointing in the same direction. Upon complexation with a sodium ion, the ring adjusts by arching inward, tilting the CO groups towards each other. The preparation of triolide 1 from poly(R)-3-hydroxybutanoate is surprisin…
The thermal conductivities of two-dimensional crystalline, amorphous, and quasicrystalline classical models are studied via the nonequilibrium molecular-dynamics method. The behavior of the high-temperature thermal conductivities of crystal and glasses are reproduced. The difference between the thermal conductivities…
Diamond films, deposited on silicon substrates through microwave-assisted chemical vapor deposition, have been polished with a 500-eV beam of oxygen ions through the use of a planarizing layer. The films' surface roughness, in excess of 1 microm (rms) and 6 microm (peak to valley), was reduced to 35 nm (rms) and 217 n…
Abstract A model is presented to interpret the results of XPS electron take‐off experiments obtained for natural oxide films on polycrystalline tantalum. The high‐resolution spectrum of Ta 4f shows signals from Ta, TaO and Ta 2 O 5 . The angle variations of the intensity ratios Ta 2 O 5 /Ta and TaO/Ta show that the em…
The feasibility of applying the double-layer capacitor to uninterruptible power systems and electric vehicles is addressed. The double-layer capacitor improves energy storage density by two orders of magnitude over the traditional electrolytic capacitors. Compared to batteries, the energy density of the double-layer c…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTHydroxo and azolate derivatives of pentafluorophenyl-nickel(II) complexes. Crystal structure of [NBu4]2[{Ni(C6F5)2(.mu.-OH)}2] and [NBu4]2[{Ni(C6F5)2}2(.mu.-OH)(.mu.-pyrazolato)]Gregorio Lopez, Gabriel Garcia, Gregorio Sanchez, Joaquin Garcia, Jose Ruiz, Juan A. Hermoso, Ang…
We have studied the martensitic transformation in a family of Cu-Al-Be crystals: We have measured the entropy change of the transition using a high-sensitivity calorimeter, and the elastic anisotropy of the high-temperature phase as a function of temperature by an ultrasonic method. Both entropy change and elastic ani…