Materials Literature
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Molecular dynamics simulations of lithium metasilicate (Li(2)SiO(3)) glass have been performed. The motion of lithium ions is divided into slow (A) and fast (B) categories in the glassy state. The waiting time distribution of the jump motion of each component shows power law behavior with different exponents. Slow dyn…
It is well recognized that pH plays a significant regulatory role in most cellular processes. Increasingly, there is interest in transmembrane pH gradients, particularly with respect to tumor growth and response to therapy. NMR offers a non-invasive approach to monitoring cellular pH and detecting changes in response…
The crystal structure of a rubidian cesian phlogopite-1M from pegmatite exocontacts at Red Cross Lake, Manitoba, monoclinic, a = 5.343(1),6 = 9.247(2),c = 10.397(3) Å, β = 100.04(2)°, V= 505.8(2) Å 3 , has been refined to an R index of 4.5% based on 519 observed reflections measured with graphite-monochromated MoΚα X-…
In this study, the effects of ionizing radiation on the aromatic polymers polyethersulfone (PES) and polyetheretherketone (PEEK) were investigated. UV light, /spl gamma/ rays and a high-energy electron beam were used as radiation sources. A range of techniques has been utilized to investigate changes in PES and PEEK a…
ADVERTISEMENT RETURN TO ISSUEPREVCommunication to the...Communication to the EditorNEXTPoly(p-phenyleneethynylene)s Are Thermotropic Liquid Crystalline†Lioba Kloppenburg, David Jones, John B. Claridge, Hans-Conrad zur Loye, and Uwe H. F. BunzView Author Information Department of Chemistry and Biochemistry, The Univers…
Abstract The coalescence behavior of immiscible blends was determined by annealing the melt without shear. The kinetics and the mechanism of coalescence were observed for blends of thermoplastic polyurethane (TPU) and polyolefins. Two different types of measurements were used to observe coalescence in quiescent melt a…
This report provides guidelines in selecting materials for satellites and space platforms, designed to operate within the Low-Earth orbit environment, which limit the effects of atomic oxygen interactions with spacecraft surfaces. This document should be treated as an introduction rather than a comprehensive guide sin…
The crystal structure of sulfathiazole [4-amino- N -(2,3-dihydro-2-thiazolylidene)benzenesulfonamide, C 9 H 9 N 3 O 2 S] polymorphic form V has been determined from high-resolution synchrotron X-ray powder diffraction data. The structure is monoclinic, space group P 2 1 / n , Z = 8, with two molecules in the asymmetri…
We observe prewetting films of 8CB (4'-n-octyl-4-cyanobiphenyl) spreading at room temperature on silicon wafers by ellipsometry and x-ray reflectivity. Ellipsometry indicates the formation of a nondense monolayer spreading in front of a 45-A-thick film. X-ray reflectivity, performed using a ribbon geometry for the liq…
The sliding friction and wear of three different grain‐size aluminas were studied from room temperature through 1000°C. The coefficient of friction revealed two distinct regions of decrease with increased temperature, with a transition at ∼700°C. Below 700°C, the coefficient of friction decreased rapidly with increase…
A series of oligo( m -phenylene ethylene)s having triethylene glycol ester-linked side chains (i.e., 2-[2-(2-methoxyethoxy)ethoxy]ethyl esters) were prepared, and their supramolecular organization in the solid-state was studied. These oligomers are amphiphilic, having a nonpolar aromatic hydrocarbon backbone that is a…
A woven‐fabric Hi‐Nicalon™‐fiber reinforced SiC‐matrix composite has been fabricated by using a multiple polymer infiltration‐pyrolysis (PIP) process. The three‐point bend strength, at room temperature, of the composite is examined as a function of total porosity of the composite. The porosity of the composite decreas…
Additions of Bi 2 O 3 were used to enhance densification and to promote grain growth during sintering of NiO–CuO–ZnO ferrite. With a small amount of Bi 2 O 3 (0.5–2.5 wt%) present as a sintering aid in NiO–CuO–ZnO ferrite, the densification rate and final sintered density are greatly increased, but the activation ener…
Polarized first-order Raman scattering studies at 300 K were carried out in L-asparagine monohydrate crystal in order to obtain the general assignment of its phonon spectra. A careful analysis of the vibrational spectra shows that the assignment of the fundamental vibrational modes can be done on the basis of amino, c…
A 7-azaindole adduct of boroxine, B 3 O 3 Ph 3 (7-azaindole), 1, was obtained from the reaction of PhB(OH) 2 with 7-azaindole. The crystal structure of 1 shows that the 7-azaindole ligand is bonded to the boroxine molecule through a B−N bond and an H···O hydrogen bond. Compound 1 is fluorescent in solution and the sol…
X-ray diffraction (XRD) studies on single-walled carbon nanotube (SWNT) samples prepared by the arc-discharge method were reported. The XRD profile was basically explained to be a result of triangular packing of SWNTs with a lattice constant of 17.1 Å and an average nanotube radius of 7.1 Å. We found an anomalous chan…
This paper reports the formation of ß‐silicon carbide by the process of pyrolyzing rice husks (RH). The sequence of transformations and the mechanism of formation of crystalline silica, carbon, and silicon carbide from RH were investigated in detail. The structural evolution of silicon carbide particulates during the…
The valence electronic properties of some unsubstituted and peripherally substituted oxo-titanium phthalocyanines are reported. Semiempirical quantum chemical calculations show that the nature of peripheral substituents has a strong bearing on the valence electronic properties, including the state dipole moments and a…
Elastomeric poly(propylene) with low percentages of isotactic pentads and high molecular weight was synthesized using unbridged “oscillating” metallocenes. The polymer sample with the highest [mmmm] content (22%) shows a small amount of crystallinity, which is highly influenced by the thermal history, and differs sign…
Star poly(lactides) with well defined molecular architectures have been synthesized from multifunctional dendritic initiators derived from 2,2′-bis(hydroxymethyl)propionic acid (bis-MPA) derivatives. The bis-MPA derivatives, in the presence of stannous 2-ethylhexanoate, generated new polymeric structures with accurate…