Materials Literature
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We report a systematic study of the first and second hyperpolarizabilities of several small molecules at a consistent level of theory and basis sets. Coupled cluster (CC) methods for correlation, analytical high-order time dependent Hartree–Fock (TDHF) theory for dispersion effects, and polarizability-consistent basis…
The authors report time-resolved photoluminescence spectroscopy of highly porous silicon. Their results show that the luminescence is due to localized quantum-confined excitons in undulating crystalline silicon wires. The resonantly excited photoluminescence spectrum exhibits satellite structure due to momentum-conser…
Abstract The principal chemical mechanisms relevant to the growth of diamond from gaseous hydrogen and hydrocarbon species are presented. The kinetic processes occurring during the activation and transport of the gaseous species to the growing surface are described, with the key processes being the generation and subs…
The spontaneous macroscopic polarization of perovskite ${\mathrm{KNbO}}_{3}$ is calculated as a Berry's phase using the Bloch functions of the tetragonal crystal. The result P=0.35 C/${\mathrm{m}}^{2}$ supports the measured value 0.37 C/${\mathrm{m}}^{2}$ and implies that earlier data from hysteresis loops are too low…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThe electrochemical activity of boron-doped polycrystalline diamond thin film electrodesGreg M. Swain and Rajeshuni. RameshamCite this: Anal. Chem. 1993, 65, 4, 345–351Publication Date (Print):February 15, 1993Publication History Published online1 May 2002Published inissue 1…
The parametrization and optical properties such as absorption, photoluminescence (at 300 K and 77 K) and lifetimes of the lasing transition ( 5 D 0 to 7 F 2 ) of the EuF 3 (1 M%)-doped heavy metal fluoride glass (HMFG) systems of: 48ZrF 4 +24BaF 2 +7AlF 3 +20RF where RF=LiF, NaF and KF are studied. These Eu 3+ glasses…
In this review, the present level of infrared spectroscopy at surfaces is described by using hydrogen-terminated silicon surfaces as model systems. The electronic structure of the adsorbate, H, and the large mass difference between H and Si simplify the interpretation of the data and make it possible for the theories…
An electrochemical method for growing macroscopic fibers of electrically conductive poly(3-methylthiophene) is described. Single fibers of uniform diameter (∼0.1 to 0.7 millimeter) and length greater than 10 centimeters are grown in a capillary flow cell by electrochemical oxidation of the monomer, 3-methylthiophene.…
Brushes of liquid crystalline polymers swollen by nematic solvents are described by an extended Alexander model. Long-main-chain LCP with hairpins are considered. For the case of homogeneous anchoring a second-order tilting phase transition is expected as the grafting density is increased. When the grafting density is…
Abstract A number of polyurethanes (PUs) were synthesized by reacting castor oil with toluene‐2,4‐diisocyanate and hexamethylene diisocyanate and varying the NCO/OH ratio. All these polyurethanes were reacted with some acrylic monomers like ethyl acrylate, n ‐butyl acrylate, ethyl methacrylate, and butyl methacrylate…
Abstract Poly(methyl methacrylate) (PMMA) was photolyzed with monochromatic light of wavelengths 260, 280, 300, 320, 400, and 500 nm in vacuo by the use of the Okazaki Large Spectrograph. UV spectral changes, the quantum yields of main‐chain scission (ϕ cs ), and effects of wavelength were investigated. UV spectral ch…
Abstract The diffusion and permeation coefficients for He, H 2 , D 2 , O 2 , and N 2 in a variety of elastomers were measured by simple manometric methods. The elastomers studied were butyl rubber; Hypalon® 40 and 45; Viton® E60 and GF; Hydrin® 100 and filled Hydrin® 100; Kraton® G, FG, and KG VTEOS; EPDM; epoxidized…
The gene encoding component E, the large subunit, of adenosylcobalamin (coenzyme B12)-dependent glutamate mutase from Clostridium tetanomorphum has been cloned and sequenced. The mutE gene encodes a protein of 485 amino acid residues, with M(r) 53,708. The mutE gene is situated some 1,400 bp downstream of the mutS gen…
Be-doped cubic boron nitride (c-BN) powders, prepared at 5 GPa and 1700 °C by using Li3BN2 as a catalyst, were sintered at 7.7 GPa and 2100 °C without the addition of any sintering aids. The polycrystals so obtained were p-type semiconductors as determined by the electric and thermoelectric methods. Nonlinear current-…
We report x-ray diffraction measurements of the effects of electric fields on charge-density-wave (CDW) structure in ${\mathrm{NbSe}}_{3}$. For fields exceeding the CDW depinning field ${\mathit{E}}_{\mathit{T}}$, the (0 1+Q 0) CDW superlattice peak shifts along ${\mathit{b}}^{\mathrm{*}}$. The shift increases rapidly…
Abstract Shrinkage, retractive stress, and infrared dichroism of the drawn low‐density polyethylene (LDPE) as‐drawn and irradiated by 60 Co‐ray have been measured under different annealing conditions. The shrinkage and the disorientation of the irradiated sample was undergone more rapidly than that of unirradiated one…
Abstract The surface compositions and characteristics of perfluorodecanoic acid (PFDA)‐grafted polyurethane (PU) were investigated to understand its enhanced blood compatibility. The grafting of PFDA was identified by attenuated total reflectance–Fourier transform infrared (ATR–FTIR). The results from angular‐dependen…
Abstract Isothermal and constant heating rate thermogravimetric analysis (TGA) experiments have been performed for examining decomposition of polymers and composites. In practice, low heating rates are necessary to obtain good resolution under nonisothermal conditions thus increasing the time required for experiments.…
The use of high-temperature nuclear magnetic resonance (NMR) spectroscopy provides a means of investigating the structure of refractory aluminate liquids at temperatures up to 2500 K. Time-averaged structural information indicates that the average aluminum coordination for magnesium aluminate (MgAl(2)O(4)) liquid is s…
Textures of calcite crystals from a variety of mineralized tissues belonging to organisms from four phyla were examined with high-resolution synchrotron x-ray radiation. Significant differences in coherence length and angular spread were observed between taxonomic groups. Crystals from polycrystalline skeletal ensembl…