Materials Literature
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A series of novel dis- and trisazo dyes containing a perfluoroalkyl, perfluoroalkylthio and perfluoroalkylsulphonyl groups have been synthesized. The absorption bands of these dyes were more bathochromic than the corresponding alkyl derivatives. The solubility of disazo dyes containing perfluoroalkyl and perfluoroalky…
We have carried out extensive molecular-dynamics simulations of randomly cross-linked polymers and studied the onset of rigidity as the number of cross-links is increased. We find that for our systems, consisting of chains of length N=10, 20, 30, and 50, the shear modulus E vanishes at a concentration of cross-links t…
Abstract Apparatus has been constructed to abrade the flat surface of a rubber disk by rotating it against a stationary knife-blade scraper at constant frictional torque. The ratio of worn surface area to sample volume is relatively large, giving high sensitivity of measurement. Rates of abrasion were measured for sev…
Thermal shock damage in a two‐dimensional woven‐Nicalon (tm) ‐fiber‐reinforced‐CVI SiC‐matrix composite was induced by water quenching and characterized by optical microscopy as a function of quench temperature difference (Δ T ) and number of quench cycles. Mechanical damage generated in flexure on quenched and unquen…
The quasi-one-dimensional conductors (PE${)}_{2}$${\mathrm{PF}}_{6}$\ensuremath{\cdot}2/3THF and (PE${)}_{2}$${\mathrm{AsF}}_{6}$\ensuremath{\cdot}2/3THF (PE = perylene, THF = tetrahydrofuran) undergo a Peierls transition at ${\mathit{T}}_{\mathit{P}}$ = 118 K and 102 K, respectively. We present specific-heat data and…
Abstract Die Kristallstruktur von Ag 5−x Te 3 wurde durch Einkristall‐Röntgenstrukturanalyse ermittelt. Die Struktur besitzt hexagonale Symmetrie (P 6 2m, Nr. 189) mit a = 13,456(9) Å und c = 16,917(9) Å. Die Verbindung besteht aus beweglichen Silberkationen, die in einem Tellur‐Gerüst von Frank‐Kasper‐Polyedern verte…
Fossula, gen. nov., type Fossula arctica spec, nov, is described from Arctic waters influenced by sea ice. It forms ribbon shaped colonies like Fragilariopsis and Fragilaria but differs from these genera in valve and band structure. It differs from Fragilariopsis by having a sternum in the middle of the valve, a labia…
S.177-184
We present experimental photoemission and inverse hotoemission spectra of $SrTiO_{3-\\delta}$ representing electron-doped $d^0$ systems. Photoemission spectra in the presence of electron doping exhibit prominent features arising from electron correlation effects, while the inverse photoemission spectra are dominated b…
Abstract An acid Appalachian soil was amended with two flue gas desulfurization (FGD) by‐products, one consisting of wallboard‐quality gypsum (CaSO 4 ·2H 2 O) and the other containing CaSO 3 ·0.5H 2 O as a major component. Soil columns treated with FGD by‐products were leached with deionized H 2 O under unsaturated co…
The frustule of Cocconeis costata var. costata, its varieties hexagona and pacifica, and C. pinnata (Bacillariophyceae), mainly collected in SE Pacific Ocean coastal and antarctic waters, have been studied. Ultrastructural information is provided for the first time for most of them. The taxa show several common featur…
Abstract Due to the difference in reactivity between free isocyanates and uretdione rings, diisocyanate dimers can be used as blocked isocyanates. They offer the potential advantage that no volatile by‐products are formed. The toluene 2,4‐diisocyanate dimer contains one uretdione ring, formed by dimerization of two is…
Georgia kaolinite dehydroxylated at 950°C for 24 h, then leached with KOH at 90°C for 1 h, shows a well‐resolved 29 Si MAS NMR resonance at −77.5 ppm, within 2 ppm of the calculated position for Si incorporated in γ‐alumina spinel. From a knowledge of the total SiO 2 in the leached sample and its partitioning between…
Although past efforts in universities, government laboratories and industry have tried many materials in an attempt to find a mould suitable for casting titanium alloys, no ceramic mould that is completely resistant to titanium has been developed. Because much of this work was conducted more than 30 years ago and beca…
A preliminary survey of eight rivers and streams has revealed a distinctive epipsammic flora. The different water types support at least three distinctive associations of species. The separation of contaminant diatoms from other communities has been attempted, but there is still a problem, though it can be reduced whe…
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…