Materials Literature
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Ab initio and semiempirical molecular orbital methods have been used to calculate the bulk and surface Raman and hyperRaman spectra of pyridine. Similar calculations for benzene are also reported. For both molecules, we compare the results with available bulk and surface experiments. In all calculations, the polarizab…
The function of a highly mobile loop in Escherichia coli dihydrofolate reductase was studied by constructing a mutant (DL1) using cassette mutagenesis that had four residues deleted in the middle section of the loop (Met16-Ala19) and a glycine inserted to seal the gap. This part of the loop involves residues 16-20 and…
The anodic dissolution of silicon in fluoride media has been investigated by impedance measurements. In nonresonant conditions, behavior typical of metal corrosion is observed: at low positive potentials, up to a first current maximum (regime of porous silicon generation), the main feature of the impedance is an induc…
Experiments on hydrothermal synthesis were conducted using quartz or silicic acid and lime as starting materials at Ca/Si = 2.0. It is possible to synthesize pure hillebrandite (Ca 2 (SiO 3 )(OH) 2 ) having the theoretical composition by heating at 200°C for 10 h or at 250°C for 5 h. The synthesized product is fibrous…
Detailed transmission electron microscopy (TEM) studies have been carried out in order to examine the role of annealing twin boundaries in the cyclic deformation of ramp-loaded polycrystalline copper. It is found that regions adjacent to the twins are preferred sites for earlier formation of persistent slip bands (PSB…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThermal and thermooxidative degradation of poly(ethylene oxide)-metal salt complexesLuigi Costa, Ali M. Gad, Giovanni Camino, G. Gordon Cameron, and M. Younus QureshiCite this: Macromolecules 1992, 25, 20, 5512–5518Publication Date (Print):September 1, 1992Publication Histor…
Abstract The adsorption isotherms of O 2 , N 2 , CH 4 , CO 2 , SO 2 , and NO on five pillared clays (Zr, Al, Cr, Fe, and Ti‐PILCs) are measured. The equilibrium selectivity of CH 4 /N 2 on Al‐PILC is greater than 5.0, which exceeds all known sorbents by a large margin. In addition, high SO 2 /CO 2 equilibrium selectiv…
Three different diameters (0.50, 1, and 2 μm) of monosized spherical pores were introduced, at different volume percents up to 15%, into two submicrometer commercial Zr(Y)O 2 powders which exhibited either sluggish (ZrO 2 –3 mol% Y 2 O 3 ) or rapid (ZrO 2 –8 mol% Y 2 O 3 ) grain growth kinetics. Densification and grai…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTColumnar ordering of liquid-crystalline discotics in Langmuir-Blodgett filmsO. Karthaus, H. Ringsdorf, V. V. Tsukruk, and J. H. WendorffCite this: Langmuir 1992, 8, 9, 2279–2283Publication Date (Print):September 1, 1992Publication History Published online1 May 2002Published…
Holograms are recorded by a 514-nm laser polarized parallel to the molecular director in an azo-dye-doped nematic liquid crystal. For some surface treatments, the recorded holograms persist in the dark. For glass surfaces, exposure to light polarized normal to the molecular director erases the hologram. The hologram a…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTMonotropic liquid crystal behavior in two poly(ester imides) with even and odd flexible spacersRicardo Pardey, Anqiu Zhang, Patricia A. Gabori, Frank W. Harris, Stephen Z. D. Cheng, Jerry Adduci, John V. Facinelli, and Robert W. LenzCite this: Macromolecules 1992, 25, 19, 50…
A polytopic host for several cations and anions or cation/anion aggregates was previously unknown. The anion of the title (structure depicted on the right) is a host/guest system in which the “host”—the shell—consists of electrophilic and nucleophilic components. The cation/anion aggregate (NH4)2Cl2, a section of the…
The composition of films deposited in RF glow discharges fed with tetraethoxysilane and oxygen mixtures has been investigated by means of in situ x‐ray photoelectron spectroscopy and infrared spectroscopy. These results, combined with mass spectrometric investigations of the gas phase, indicate that the overall deposi…
A new, low band‐gap polymer (see figure), a hybrid of polythiophene and polyisothianaphthene, has been synthesized. Current interest in the synthesis of low bandgap polymers is considerable in view of their potentially superior conductivity and nonlinear optical properties. The results complement well the independent…
This paper describes the synthesis and characterization of AB block copolymers based on ω-[(4-cyano-4′-biphenyl)oxy]alkyl vinyl ether (6-n), with alkyl being ethyl (6-2), propyl (6-3), nonyl (6-9), and undecanyl (6-11), with 1H, 1H, 2H, 2H-perfluorodecyl vinyl ether (CF8), poly[(-6-n)-b-CF8]X/Y (where X/Y refers to th…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTstar-Porphyrazines: synthetic, structural, and spectral investigation of complexes of the polynucleating porphyrazineoctathiolato ligandChristopher S. Velazquez, Glenn A. Fox, William E. Broderick, Kevin A. Andersen, Oren P. Anderson, Anthony G. M. Barrett, and Brian M. Hoff…
Azotobacter vinelandii UWD formed polyhydroxyalkanoate (PHA) copolymers containing beta-hydroxybutyrate and beta-hydroxyvalerate (HV) when grown in a medium containing glucose as the primary C source and valerate (pentanoate) as a precursor. Copolymer was not formed when propionate was added to the glucose medium but…
We report erasable holographic recording with a resolution of at least 2500 lines/mm on unoriented films of sidechain liquid-crystalline polyesters. Recording energies of approximately 1 J/cm(2) have been used. We have obtained a diffraction efficiency of approximately 30% with polarization recording of holograms. The…
The entire nucleotide sequence of the Bacillus brevis grsB gene encoding the gramicidin S synthetase 2, which activates and condenses the four amino acids proline, valine, ornithine and leucine has been determined. The gene contains an open reading frame of 13,359 bp which encodes a protein of 4453 amino acids with a…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThe near-infrared spectrum of the guanidinium ion: a local-mode analysisIan M. Walker and Paul J. McCarthyCite this: Inorg. Chem. 1992, 31, 20, 4122–4127Publication Date (Print):September 1, 1992Publication History Published online1 May 2002Published inissue 1 September 1992…