Materials Literature
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The effects of high external pressures on the micro-Raman spectra of potassium chromate, K 2 CrO 4 , and potassium tungstate, K 2 WO 4 , have been investigated for pressures approaching 45 kbar. There is no evidence for a pressure-induced phase transition in the chromate, but there is clearly such a transition at ∼13…
Abstract Polyetheretherketone‐polydimethylsiloxane (PEEK–PDMS) block copolymers were synthesized from the condensation of dimethylamino terminated PDMS and hydroxy terminated PEEK oligomers in 1‐chloronapthalene. Yields for block copolymers synthesised from low molecular weight PDMS oligomers were good but yields were…
The characteristics of excimer lasers and the nature of ablation and etching processes are described. The two kinds of laser ablation mechanisms, thermal and electronic, are discussed. Thermal processes all rely on an intense laser pulse to heat a surface very rapidly. Electronic mechanisms do not rely on heating. Two…
Some optical investigations including measurements of birefringence and angle between the extinction positions in different domains, have been performed on [N(CH3)4]2MnCl4, In addition the domain structure has been studied using an optical microscope. The observed anomalies in the birefringence measurements clearly co…
Abstract The effects of rubber content, particle size and interparticle spacing on the fracture behaviour of toughened polymers over a range of strain rates and temperatures are discussed with particular reference to high‐impact polystyrene and rubber‐toughened nylons. It is concluded that the limiting factor in deter…
The effect of local anesthesia containing epinephrine on the survival of split- and full-thickness skin grafts remains unclear. In this blinded study, Xylocaine with or without epinephrine was injected subdermally prior to harvesting of split-thickness and full-thickness skin grafts on the dorsum of rabbits. After pro…
We first briefly draw the reader’s attention to some of our papers recently published in other journals. Then, after some comments on the admittance and impedance operators, we introduce the Calderon projectors, and we show how the operator formalism can be used in grating problems. Finally, we present theoretical con…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTLandau theory of symmetry-breaking transitions: a basis for clarification of diffraction studies of phase behaviorHugo F. FranzenCite this: Chem. Mater. 1990, 2, 5, 486–491Publication Date (Print):September 1, 1990Publication History Published online1 May 2002Published iniss…
Aspiration is a serious complication of oral contrast media (CM). The authors investigated the effects of iotrolan, iopamidol, and diatrizoate in rats' lungs. To quantify the lung damage induced by CM, pulmonary water and hemoglobin contents were determined. Arterial blood-gas exchange (pH, PCO2, and PO2) also was det…
Improvements of welding processes by plasma or laser require a good knowledge of the microscopic properties of the liquid associated to the melted area. The development of new high temperature NMR probes allows to reach such a goal. In the case of alumina bearing liquids, the analysis of the 27Al resonance line shows…
The effect of pH on phosphate sorption by soil samples from two coarse-textured pedons of typic Paleudults in the perhumid tropical zone of Nigeria was studied by equilibrating air-dried soil samples adjusted to pH 3.5–6.5 for 48 h with 10 ppm P and 60 ppm P solutions at two concentrations of CaCl2 and NaCl. Phosphate…
The phase transitions undergone by [N(CH3)4]2 MnCl4 crystals in the 10–300 K temperature range have been explored through the absorption and emission spectra as well as lifetime measurements. The present measurements confirm the existence of phase transitions at Tc3 = 268.7 K and Tc4 = 175.6 K and provide clear eviden…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTA New Pentacyclic Triterpene from Abutilon pakistanicumZaheer Ahmed, Syed Najam-ul-Hussain Kazmi, and Abdul MalikCite this: J. Nat. Prod. 1990, 53, 5, 1342–1344Publication Date (Print):September 1, 1990Publication History Published online1 July 2004Published inissue 1 Septem…
Three new series of cyanoaryl 4-alkylthioxybenzoates have been synthesized and characterized. The 4-cyanophenyl series displays only transient mesomorphic properties while the 6-cyano-2-naphthyl and 4-cyanobiphenyl series exhibit the classical nematic and smectic A phases; a reentrant nematic phase is also found in th…
Abstract Good yields of arecolone and isoarecolone were obtained by treating the N,O ‐dimethylamides of arecaidine and isoarecaidine, respectively, with methylmagnesium chloride. Other substituted arecolones were synthesized by this same strategy.
SiC polycrystalline layers were deposited on a graphite substrate from a gas mixture of CH3SiCl3+H2(+Ar) at temperatures in the range of 800–1200 °C. The effects of the source gas flow rate (CH3SiCl3+H2), total pressure, linear velocity and Ar flux addition on the phase of the deposits were examined in some detail. Th…
The underlying physical principles of electromigration, which is one of the principal wearout mechanisms of the metal conducting tracks in LSI and VLSI circuits, are introduced. Track lifetime is believed to be influenced by the track dimensions, composition and passivation layer. These effects are considered. Differe…
Abstract Presently, a suitable theory to predict the T g vs. composition relationship for a given polymer‐plasticizer blend, based on detailed molecular structure and molecular energitics considerations, is not available. In particular, the plasticizer efficiency parameter, k , which is uniquely defined at low‐to‐mode…
Abstract Poly(l,4‐cyclohexylene dimethylene terephthalate) (PCT) exhibits superior heat deflection temperature when compared to conventional polyesters such as poly(butylene terephthalate) or poly(ethylene terephthalate). It is subject to degradation, however, at the processing temperatures normally employed to extrud…
Abstract The fundamental skeleton of the tropones possessing a unique heptagonal structure is predicted to be aromatic with positive resonance energies and conforming to the topological charge stabilization rule (TCS rule). Similarly, naturally occurring tropolones also nicely fit the theory that conformity to the TCS…