Materials Literature
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On présente quelques propriétés spectroscopiques, de verres dopés, importantes pour la conception de mini-lasers telles que : forces d'oscillateur, section. efficace laser, durée de vie radiative et rendement quantique en fonction de la concentration. Deux verres, un tellurite de lithium et un phosphate de cadmium pot…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTNitric Acid Oxidation of High-Density Polyethylene. Organic Chemical AspectsL. Russell MelbyCite this: Macromolecules 1978, 11, 1, 50–56Publication Date (Print):January 1, 1978Publication History Published online1 May 2002Published inissue 1 January 1978https://pubs.acs.org/…
Abstract Feldspar grains or their pseudomorphs from the different weathering zones are studied with the SEM. Weathering commences with dissolution to form voids in the grains. Close to the rock, the first product is allophanic material present as globules adhering to the voids in the grains. In the δ zone the product…
A new aluminium silicate has been produced under hydrous conditions from Al2O3-SiO2 oxide mixes with Si/Al ratios close to unity, at pressures greater than 100 kilobars and at about 1, 000°C. X-ray powder photographs indicated one dominant new phase. From analyses of the electron diffraction Laue zones of minute fragm…
Thermoelectric generators have no moving parts, are silent in operation and are compact, and, when coupled to an isotropic heat source, can operate unattended over long periods in inhospitable and inaccessible environments. In recent years, thermoelectric generators have found increased application in situations where…
The topological classification of distortions in ordered media leads naturally to a distinction'between singular distortions (defects) and non singular distortions. However, in cholesteric liquid crystals, where the order parameter contains components with different rigidities, the optically observed distortions prese…
The equilibrium adsorption–desorption behaviour of small, positive polystyrene latex particles onto much larger, negative polystyrene latex particles, in which both sets of particles carry adsorbed poly(vinyl alcohol)(PVA) molecules, has been studied as a function of the molar mass of the PVA, and the ionic strength.…
Elastic moduli and fracture toughness were determined for several glasses in the systems soda‐alumina‐silica, calcia‐alumina‐silica, and soda‐boric oxide‐silica. Results for the aluminosilicates are analyzed in terms of Al 3+ :Na + ratios. The mechanical properties do not show maxima or minima at the Al 3+ :Na + ratio…
The threshold characteristics of an instability in the form of longitudinal flexo-electric domains, arising in thin layers of liquid crystals exposed to a d.c. field were investigated for two nematic mixtures based on azoxy-and ester compounds. The experimental dependences of the threshold voltage and the domain perio…
Abstract The nucleation and growth behavior of a poly(1‐butene) melt has been measured as a function of undercooling and shear rate. Experiments were conducted using a parallel‐plate rotary shearing device with polarized light microscopy as the measuring technique. An exponential increase of nuclei with time at consta…
Abstract A model for amorphous metals is proposed. The model is based on the 13 atom icosahedron which is the minimum energy structure for a 13 atom cluster. An amorphous metal is considered as containing a high density of these structural units. The material surrounding the icosahedra is partially ordered. The spaces…
Article Studies of structure and dynamics of solid polymers by elastic and inelastic neutron scattering was published on January 1, 1978 in the journal Pure and Applied Chemistry (volume 50, issue 11-12).
C2-oxygenated compounds composed mainly of ethanol were catalytically produced from CO and H2 under atmospheric pressure over pyrolysed Rh carbonyl clusters dispersed on specific metal oxides such as TiO2, ZrO2, and La2O3.
Abstract The parameters governing electron backscattering from thin films and from bulk solids are reviewed: Atomic scattering cross‐section, atomic number, single/multiple scattering, film thickness, scattering angular distribution, angle of incidence, diffraction effects. Their influence on some important contrast m…
Ultrasonic velocities at 5 and 10 MHz and spontaneous strains of KD 3 (SeO 3 ) 2 were measured and the results were compared with those for KH 3 (SeO 3 ) 2 . Elastic constants were obtained from the velocity data. The phase transition of KD 3 (SeO 3 ) 2 accompanies an instability of the soft s 44 mode alone, as in the…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTPropagation and Depropagnation Rates in the Anionic Polymerization of ε-Caprolactone Cyclic OligomersKoichi Ito and Yuya YamashitaCite this: Macromolecules 1978, 11, 1, 68–72Publication Date (Print):January 1, 1978Publication History Published online1 May 2002Published iniss…
Summary The authors report on the presence of a new alga (which appears to belong to the Rhodophyta) in the thermal acidic environments near the solfatane fumaroles of Campi Flegrei (Naples, Italy). On the ground of the microscopical observations, the authors emphasize that the characteristics of this alga are so pecu…
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Abstract The crystal structure of isotactic poly(4‐methyl‐1‐pentene) was determined by x‐ray analysis. The unit cell is tetragonal, P 4 b 2, with α = 18.70 Å and c (fiber axis) = 13.68 Å; it contains four molecular chains each consisting of seven monomeric units in the fiber period. The molecular conformation is essen…
Laser flash photolysis has been used to characterise the triplet state of metal-free (H2Pc) and copper phthalocyanine (CuPc) in dilute (10–6 mol dm–3) solution in chloronaphthalene. This first observation of the triplet state of CuPc indicates that its lifetime is very short (∼35 ns), but the quantum efficiency of tri…