Materials Literature
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Intershell spacings between carbon nanotubes ${\stackrel{^}{d}}_{002}$ ranging from 3.59 \AA{}A to 3.62 \AA{}A, with an uncertainty of \ifmmode\pm\else\textpm\fi{}0.06 \AA{}A, are deduced by using the in-plane C-C bonding length in the graphene hexagonal network as an internal calibration standard for the digital imag…
The diatom flora from two high altitude, tropical lakes is reported in this paper. These lakes (“Lago de la Luna” and “Lago del Sol”) lie within the crater of one of the major volcanoes in Central México: the Nevado de Toluca (4,620 m asl). Both had diluted, acidic water (pH ≤ 6, electrical conductivity (E.C.) ≤ 25 μS…
Abstract Pyrolysis coupled with GC/MS was used to study thermal degradation products of styrene—butadiene rubber (SBR). Introduction of samples, using the pyrolysis carrier gas through the split injection port, followed by sub-ambient focusing of pyrolysis products gave reproducible chromatograms. The styrene content…
Thermodynamic parameters for E. coli chorismate mutase are reported. In addition, site-directed mutagenesis studies provide a direct mechanistic link to yeast chorismate mutase, further indicating the importance of entropic restriction and hydrogen bonding in the enzymic catalysis of Claisen rearrangements.
Cu-doped Al-, Ti-, and Zr-pillared montmorillonites obtained by various procedures have been investigated with the aid of electron spin resonance (ESR). The major species present in pillared montmorillonites exchanged with copper at low pH are physisorbed square planar tetraaquo-complexes [Cu(H 2 O) 4 ] 2+ . Only at t…
Abstract The pressure dependence of the phonon modes in the layered semiconductor γ‐InSe has been investigated experimentally and theoretically for pressures up to 11 GPa. The mode Grüneisen parameters of all Raman‐active zone‐center phonons have been determined by Raman scattering under pressure. In addition, feature…
Corrosion properties of pulse-plated Zn-Ni alloy coating on a steel substrate were investigated using the neutral salt-spray test (ASTM B 117-81) and the potentiodynamic polarization technique (ASTM G 5-82). Performance of these alloy coatings with various Ni contents (up to 62 wt%) was compared to that of laboratory-…
The spin-wave dispersion relations in the ferromagnet MnSb, and the antiferromagnet CrSb, have been measured, by neutron inelastic scattering, along high-symmetry directions in reciprocal space, as a function of temperature. The effect of composition is discussed. The dispersion in CrSb is found to rise very steeply a…
Abstract DSC measurements around the glass transition in the homologous series of seven poly( n ‐alkylmethacrylate)s (alkyl=methyl, ethyl, propyl, butyl, pentyl, hexyl, octyl) are presented. The step height Δ c p decreases linearly with the number of n ‐alkyl C‐atoms in the side chain. The usual glass step in the DSC…
Binary magnesium alloys containing chromium, manganese, or titanium were made using a physical vapour deposition technique. The corrosion resistance of the alloys was assessed in aqueous chloride solutions using total immersion tests in quiescent 600 mmol L−1 NaCI solutions. Alloying with manganese or titanium was fou…
The stimulated emission cross section σp for the 1060 nm transition of Nd3+ in lead borate and bismuth borate glasses has been determined from fluorescence measurements. The compositional dependence of σp, which has been evaluated using radiative transition probability, refractive index of the host glass, effective fl…
A (1012) twin boundary in deformed alpha-Ti has been observed by highresolution electron microscopy. The observations are in agreement with a model calculated using a many-body potential. A twinning dislocation is predicted by the topological theory and characterized directly in the experimental image with the circuit…
By using a 3-methoxy-4-hydroxy-benzaldehyde (MHBA) crystal as frequency doubler at room temperature, an efficient blue light output for near IR automatic tunable picosecond parametric laser is obtained, and blue-violet light output by frequency doubling of GaAlAs laser diode is also realized. A 404.5 nm light, with ou…
Inorganic materials can encapsulate organic dye molecules in a variety of ways. Those considered here are simple inorganic salts that have adsorbed, oriented, and overgrown dyes during growth from solution, which promise spectroscopic and photonic applications. The Figure shows KH 2 PO 4 crystals in which dyes carryin…
Abstract 1,4:3,6‐Dianhydrosorbitol (DAS) was used as chain extender in the preparation of new segmented polyurethane elastomers, based on polyoxytetramethylene or hydrogenated polybutadiene soft segments and 4,4′‐diphenylmethane diisocyanate (MDI). These materials exhibit a two‐phase microstructure, due to the thermod…
To address basic questions concerning proteins of the Sulfolobus acidocaldarius cell envelope, cell ghosts (empty cells consisting of cytoplasmic membrane complexed with the glycoprotein S-layer) were isolated and analyzed by standard biochemical methods. The constituent proteins included the two dissimilar subunits a…
The kinetics of curing tetraglycidyl 4,4′-diaminodiphenyl methane (TGDDM) or of the mixture TGDDM/diglycidylether of bisphenol A (DGEBA) by bis(m-aminophenyl)methylphosphine oxide (BAMPO) was studied using differential scanning calorimetry. At low advancement of curing (<50%), the low activation energy interaction bet…
A distributional method to solve the Einstein’s field equations for thin shells is formulated. The familiar field equations and jump conditions of Darmois-Israel formalism are derived. A careful analysis of the Bianchi identities shows that, for cases under consideration, they make sense as distributions and lead to j…
Silicate glasses of the composition (Li 2 O) x (SiO 2 ) 100−x ( x = 0, 20, 33.3, and 40) have been prepared and characterized by X‐ray and neutron diffraction experiments using the technique of isotopic substitution. Thus, at each composition, a set of independent diffraction patterns allows the discussion of the shor…
Abstract The polymerization of 2‐acetoxymethyl‐2‐alkyltrimethylene carbonates (alkyl = methyl: AMTC, alkyl = ethyl: AETC) and of 2‐methoxycarbonyl‐2‐methyltrimethylene carbonate (MMTC) in toluene with sec ‐butyllithium as initiator results in the respective polymer with yields between 78% and 88%. The analysis of the…