Materials Literature
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The influence of various rubbing parameters on the molecular reorientation of thin polyimide orienting layers, used to align liquid-crystal (LC) molecules within liquid-crystal displays, has been studied. For this purpose the optical phase retardation in the polymer layer, explicitly induced during the rubbing treatme…
Conducting‐polymer‐based poducts that are commercially available are the topic of this second part of a two‐part article (the first half appeared last month). Many people are not aware that conducting polymers have reached the marketplace in the form of “coin”‐shaped batteries (see Figure). 3.5.″ floppy disks, and ele…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTDodecatitanates: a new family of stable polyoxotitanatesV. W. Day, T. A. Eberspacher, W. G. Klemperer, and C. W. ParkCite this: J. Am. Chem. Soc. 1993, 115, 18, 8469–8470Publication Date (Print):September 1, 1993Publication History Published online1 May 2002Published inissue…
Abstract The mechanisms which, in isotactic polypropylene, create α phase nuclei on partial melting of β phase spherulites are investigated by thermal analysis and optical and electron microscopy. Nuclei concentrations are determined from recrystallization characteristics. α phase nuclei are formed within β spherulite…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTQuantum size effects in nanocrystalline semiconducting titania layers prepared by anodic oxidative hydrolysis of titanium trichlorideLadislav Kavan, Tiziana Stoto, Michael Graetzel, Donald Fitzmaurice, and Valery ShkloverCite this: J. Phys. Chem. 1993, 97, 37, 9493–9498Publi…
Random tilings that comprise squares and equilateral triangles can model quasicrystals with twelvefold symmetry. A (phason) elastic theory for such tilings is constructed, whose order parameter is the phason field, and whose entropy density includes terms up to third order in the phason strain. Due to an unusual const…
Low-frequency Raman spectra of some glasses have been measured at low temperature. Comparison of the spectra with heat-capacity data shows that in a broad frequency range the Raman intensity is simply proportional to the number of vibrational excitations [density of the vibrational states g(\ensuremath{\nu}) multiplie…
Only five generations of growth are necessary to generate the phenylacetylene dendrimer 1, the largest pure hydrocarbon (C1398H1278) and one of the largest dendrimers (diameter: 12.5 nm). Architectures prepared by the innovative scheme described in this communication quickly acquire a large size due to the unique patt…
We consider a phase-field model of a binary mixture or alloy which has a phase boundary. The model identifies all macroscopic parameters and the interface thickness \ensuremath{\epsilon}. In the limit as \ensuremath{\epsilon} approaches zero, an alternative two-phase alloy solidification model (with a sharp interface)…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTMechanism of manganese porphyrin-catalyzed oxidation of alkenes. Role of manganese(IV)-oxo speciesRamesh D. Arasasingham, Gong Xin He, and Thomas C. BruiceCite this: J. Am. Chem. Soc. 1993, 115, 18, 7985–7991Publication Date (Print):September 1, 1993Publication History Publi…
Abstract With short term shearing at low degrees of supercooling a method has been developed by which nucleation during shearing can effectively be separated from the subsequent crystal growth, which, in these experiments, mainly occurs after the cessation of the flow. In this way the kinetics of nucleation by shear c…
Tetragonal La-modified lead zirconate titanate ceramics with a Zr/Ti ratio of 40/60 (x/40/60) with La contents (x) between 0 and 21 at. % were prepared by the mixed oxide method and were subsequently characterized using dielectric spectroscopy. Small La contents tended to diffuse the dielectric response in the tempera…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTOxygen-17 NMR study of water exchange on gadolinium polyaminopolyacetates [Gd(DTPA)(H2O)]2- and [Gd(DOTA)(H2O)]- related to NMR imagingKaroly Micskei, Lothar Helm, Erno Brucher, and Andre E. MerbachCite this: Inorg. Chem. 1993, 32, 18, 3844–3850Publication Date (Print):Septe…
The unthreading and rethreading of pseudorotaxane 1, which contains two p-phenylene spacers linking two bipyridinium units and a central 1, 5-naphthalenediyl unit, is reversible when an initially oxygen-free solution of 1 in water also containing 9-anthracenecarboxylic acid as a photosensitizes and triethanolamine as…
Structural ceramics for high‐temperature applications should embody the following properties: oxidation resistance, chemical stability, low volatility, resistance to creep deformation, resistance to creep cavitation at interfaces, sufficient toughness at ambient temperature, and thermalshock resistance. These criteria…
SUMMARY The ability of roots to weather phlogopite as shown by the release of interlayer‐K and by the concomitant vermiculitization of the mica was investigated in the rhizosphere of Italian ryegrass ( Lolium multiflorum ), grown for 1 to 32 d on 2–105 μm mica as sole source of both K and Mg. The K‐balance showed that…
This article is based on the lecture, by Dr. María Isabel Sánchez de Rojas (Senior Researcher at the Eduardo Torroja Institute) and it is entitled "European Cement Standars" which was given in the framework of SEMINARIOS TORROJA, Building Technology and Materials.