Materials Literature
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The surfaces of AlN powders, which are particularly sensitive to moisture and atmospheric oxygen, are characterized by x-ray photoelectron spectroscopy (XPS). The powders used were exposed to ambient air and then heat treated at 100 °C in air, argon, or nitrogen gas. Bremsstrahlung-excited Auger electron spectroscopy…
Glassy and melt atactic polypropylene microstructures obtained via energy minimization and Monte Carlo simulation are subjected to geometric analysis (Delaunay tessellation followed by volume and connectivity analysis) in order to determine the clusters of sites where a hard sphere penetrant of radius 0–2.5 Å can resi…
In a two-chamber ultrahigh vacuum system, epitaxial TiO2 thin films have been deposited by metalorganic chemical vapor deposition on single crystal oxide substrates over a temperature range of 250–800 °C, using titanium (IV) isopropoxide as the precursor. During the initial stage of epitaxial film deposition, the grow…
Target-specific superparamagnetic contrast agents may allow the localization of specific tissues such as tumors by magnetic resonance imaging (MRI). In this report the preparation and in vitro characterization of tumor-specific superparamagnetic particles (SMP) are described. Particles of uniform size (9.6 +/- 0.8 nm)…
SUMMARY The ability of the roots of rape ( Brassica napus ) to promote the transformation and dissolution of a phlogopite mica was studied in the rhizosphere. Rape was cropped for 1 to 32 d on 2–105 μm phlogopite as sole source of both K and Mg. The chemical balance of K and Mg revealed that rape was able to induce a…
Cellulose-binding protein A (CbpA), a component of the cellulase complex of Clostridium cellulovorans, contains a unique sequence which has been demonstrated to be a cellulose-binding domain (CBD). The DNA coding for this putative CBD was subcloned into pET-8c, an Escherichia coli expression vector. The protein produc…
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…