Materials Literature
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Abstract A rheological technique is proposed for determining the thermally induced order–disorder transition of block copolymers. In the present investigation, a cone‐and‐plate rheometer was used to measure dynamic storage and loss moduli, G ′(ω) and G ″(ω), as a function of angular frequency ω of a commercial grade p…
Point-contact transistors and Schottky diodes have been formed on synthetic boron-doped diamond. This is the first report of diamond transistors that have power gain. Further, the transistors exhibited power gain at 510°C and the Schottky diodes were operational at 700°C.
The efficiency of a Lyot stop in reducing diffraction effects in a simple optical system is analyzed. The transformation rules of Fourier optics are used to follow the optical signal through the system. This analysis reduces the problem to the evaluation of a two-dimensional integral. An approximate analytic technique…
Abstract The optical properties of bisphenol‐A polycarbonate resin as described by the complex index of refraction, N = n – ik , are derived by Kramers‐Kronig analysis of experimental absorption and reflectance data obtained in the range 40μm ≥ λ ≥ 105 nm. Electronic absorption processes in polycarbonate are character…
In Escherichia coli strains overproducing dinucleoside tetraphosphate hydrolase, the accumulation of dinucleoside tetraphosphates (AppppN, with N = A, C, G, or U) during heat shock or H2O2 treatment was reduced about 10-fold as compared with a control strain. This accumulation neither modified the pattern of the prote…
Solid solutions of AlVO 4 crystallize at lower temperatures than amorphous materials between 50 and 70 mol% Al 2 O 3 prepared by the simultaneous hydrolysis of aluminum and vanadyl alkoxides. They decompose into α‐Al 2 O 3 , and V 2 O 5 , at 775° to 800°C. The compound AlVO 4 prepared from 50 mol% Al 2 O 3 has a tricl…
Abstract The mechanism and rate limitations in aqueous nitrogen oxides absorption are reviewed and data available on chemical kinetics for performance predictions are discussed. Application of a rate relationship to characterize interphase mass transfer for the primary reactant N 2 O 4 is shown, with mass transfer coe…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTMagnetic-field effects in the low-temperature polarized emission and absorption spectra of single-crystal tris(2,2'-bipyridine)ruthenium(2+) bis(hexafluorophosphate) ([Ru(bpy)3](PF6)2)Erich Gallhuber, Gerold Hensler, and Hartmut YersinCite this: J. Am. Chem. Soc. 1987, 109,…
To investigate magnetic hardening mechanisms in sintered Nd-Fe-B magnets, magnetic hysteresis loops of sintered Nd 15 Fe 77 B 8 magnets 100 µm thick, the surfaces of which are sputter-deposited with Nd or Tb metal, were measured at various steps in the sample preparation procedures. The surface grains in as-polished m…
Diagrammatic valence bond calculations are applied to the study of the charge–transfer (CT) excitation spectrum and of the electron–molecular vibration (emv) coupling in mixed regular stack CT crystals. The intersite electrostatic interactions are treated by both mean-field and unscreened point–charge potential approa…
Volume crystallization of this glass is nucleated by Li 3 PO 4 . On heating from room temperature, Li 2 SiO 3 appears around 650°C and then converts to Li 2 Si 2 O 5 around 850°C by reaction with SiO 2 from the melt. Preheating the glass at 1000°C forms larger Li 3 PO 4 nuclei that promote additional crystallization o…
A commercial lithium aluminosilicate glass‐ceramic material is investigated by high‐resolution transmission electron microscopy after different heat treatments. Evidence is presented that epitaxy of β‐quartz crystals on ZrTiO 4 ‐type crystallites is the critical step initiating silicate crystallization.
Recently the problem of the glass transition has been further complicated by the discovery of a phase which forms under conditions similar to those required by the formation of metallic glasses. This new phase (the “quasicrystal”) seems to be structurally intermediate between the glass and the crystal phase, being cha…
A formal expansion in spherical harmonics or Cartesian tensors of the pair correlation function of a liquid subjected to a shear rate is discussed. Expressions for the coefficients to tensor rank 4 are evaluated via a nonequilibrium molecular-dynamics simulation of an inverse twelve soft-sphere liquid undergoing Couet…
The insulation from six 5 kV power cables, which has been in service underground for 6 to 8 years, was examined by infrared (IR) spectroscopy and oxidation induction time (OIT) analysis. Sections of insulation containing water trees were found to contain high levels of ionic contaminants. All insulation samples showed…
Abstract We found 10 miscible pairs of dissimilar polymers that rendered birefringence‐free polymer blends. Each pair consists of a positive birefringence polymer and a negative one. Zero birefringence in the blend is attained as the result of compensation of positive and negative contributions to the overall birefrin…
(Ca,Mg) carbonates have been studied by solution calorimetry at 85C in an acid solvent (lM IJ)I) that was saturated at room temperature with NaCl and contained 0.7 5M CaCl, and 0.25M MgClr. The enthalpy of formation of ordered dolomite from calcite and mag' nesite at 85C is -5.74 + 0.25 kJ/mol, for a formula unit of d…
Abstract Copolymerizations of glycolide with L , L ‐dilactide were conducted in chloroform, 1,2‐dichloroethane and nitrobenzene. Chlorosulfonic acid, triflic acid, boron trifluoride, triethyloxonium tetrafluoroborate, but mainly methyl triflate, were used as initiators. 50°C was found to be an optimum reaction tempera…
Single crystals of copper-based manganese alloys (Cu−1.05, 1.3, 3.3, 5.05 and 11.6 at.%Mn) were grown and deformed in tension at room temperature. The weakbeam method of electron microscopy has been used to resolve the partial dislocations and to determine the stacking-fault energy γ. Contrary to most other Cu alloys,…
Abstract The crystallization behavior of three molecular weight samples of poly(ε‐caprolactone) has been studied as a function of temperature. Crystallization begins in the form of axialities and changes to spherulite growth as time progresses, presumably owing to the molecular weight distribution. Determinations of e…