Materials Literature
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A recently developed electro-optical Pockels effect technique, which allows the dynamic measurement of surface charge distributions, is employed to observe the dynamic behaviour of a partial discharge in a point - dielectric gap. One period of an 8 kV ac voltage is applied to a needle electrode with gap spacings rangi…
We have investigated the partial discharge (PD) due to electrical treeing degradation in low-density polyethylene (LDPE), ethylene - vinyl acetate copolymer (EVA) and ethylene - acrylic acid copolymer (EAA) by a computer-aided partial discharge measurement system which allowed us to obtain phase-resolved PD pulse data…
This review deals with the definition and development of hard magnetic materials with special emphasis on more recent developments in this field. After discussing the fundamental properties of all hard magnetic materials, based on the intrinsic and extrinsic properties, some remarks on the history of hard magnetic mat…
Carbon nanotubes have been opened using a variety of oxidants including and at room temperature. The opened nanotubes have been filled with metals such as Ag, Au, Pd and Pt by simple chemical means. The opened nanotubes, containing a high concentration of acidic functional groups, get covered or closed by reaction wit…
Diamond nanoparticles synthesized by the detonation of explosives were used as an additive in paraffin oil. The tribological properties of the two-phase lubricant of paraffin oil and diamond nanoparticles were investigated. The results show that, under boundary lubricating conditions, this kind of two-phase lubricant…
The crystallization kinetics of poly(L-lactide-co-meso-lactide) were determined over a range of 0% to 9% mesolactide. The kinetics were fit to the nonlinear Avrami equation and then to the Hoffman–Lauritzen equation modified for optical copolymers. The theory was found to fit the data well. The crystallization half-ti…
There are 590,232 federally reported bridges in the US with 186,733 or 31.6 percent being defined as substandard. Developing new methods for inspection and evaluation of bridges has recently received considerable attention. The characterization of aging responses in structural materials entails establishing the fundam…
A series of substituted triarylmethylium cations, including malachite green, tris(4-methoxyphenyl)methylium, and bis(4-methoxyphenyl)phenylmethylium cations, has been prepared adsorbed on tridirectional large pore zeolites Y and β in their H + or La 3+ form, as well as within the novel mesoporous aluminosilicate MCM-4…
The interconversion of model compounds {[(NH 3 ) 3 Cu] 2 (μ-η 2:η 2 -O 2 )} 2+ ( 1 ) and {[(NH 3 ) 3 Cu] 2 (μ-O) 2 } 2+ ( 2 ) has been examined using multireference second-order perturbation theory with an 8-electron/8-orbital active space. At this level of theory, 1 and 2 are separated by only 0.3 kcal/mol, and the b…
Oxygen intercalation into a pyrochlore at room temperature is reported. A simple chemical route was employed. Previously only perovskite or a few closely related phase have demonstrated an ability to act as hosts for such intercalation. The specific system studied was the interstitial solid solution Ce 2 Zr 2 O 7+ x (…
Using dynamic NMR spectroscopy, the kinetic isotope effects of the degenerate single hydron transfer in the conjugate 15 N-labeled porphyrin anion Por-H - dissolved in organic solvents have been measured as a function of temperature. Por-H - was generated by dissolving the labeled parent compound porphyrin together wi…
ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTHighly Enantioselective Epoxidation of trans-Stilbenes Catalyzed by Chiral KetonesDan Yang, Xue-Chao Wang, Man-Kin Wong, Yiu-Chung Yip, and Man-Wai TangView Author Information Department of Chemistry, The University of Hong Kong Pokfulam Road, Hong Kong Cite this: J. A…
A comprehensive electrochemical (cyclic and square-wave voltammetry, coulometry) and static spectroscopic (absorption, resonance Raman (RR), electron paramagnetic resonance (EPR)) study is reported for a series of dimeric and trimeric porphyrin-based arrays. All the arrays consist of tetraarylporphyrins linked via eth…
ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTn-Channel Organic Transistor Materials Based on Naphthalene FrameworksJoyce G. Laquindanum, Howard E. Katz, Ananth Dodabalapur, and Andrew J. LovingerView Author Information Bell Laboratories, Lucent Technologies 600 Mountain Ave., Murray Hill, New Jersey 07974 Cite th…
A set of porphyrin building blocks has been developed for the construction of light-harvesting model compounds and related molecular photonic devices. The porphyrins are facially encumbered to enhance solubility in organic solvents, are employed in a defined metalation state (free base (Fb) or zinc chelate), and bear…
We propose a minimal nonlinear model of brittle crack propagation by considering only the motion of the crack-tip atom. The model captures many essential features of steady-state crack velocity and is in excellent quantitative agreement with many-body dynamical simulations. The model exhibits lattice-trapping. For loa…
Soluble ethyne-linked tetraarylporphyrin arrays that mimic natural light-harvesting complexes by absorbing light and directing excited-state energy have been investigated by static and time-resolved absorption and fluorescence spectroscopies. Of particular interest is the role of the diarylethyne linkers in mediating…
A convenient procedure for the general preparation of bis(methylcyclopentadienyl)vanadium ( 1 ), bis(isopropylcyclopentadienyl)vanadium ( 2 ), and bis( tert -butylcyclopentadienyl)vanadium ( 3 ) and their blue monochloride ( 4 − 6 ) and green dichloride ( 7 − 9 ) derivatives is presented. The X-ray structures of compo…
Alcaligenes eutrophus genes encoding the enzymes, beta-ketothiolase (phaA), acetoacetyl-CoA reductase (phaB), and polyhydroxyalkanoate synthase (phaC) catalyze the production of aliphatic polyester poly-d-(-)-3-hydroxybutyrate (PHB) from acetyl-CoA. PHB is a thermoplastic polymer that may modify fiber properties when…
Luminescent films of porous silicon were obtained by laser ablation of crystalline silicon. The spectral and temporal characteristics of light emission from laser ablated porous silicon (LAPS) films critically depend on the chemical composition of the atmosphere in which they were fabricated. Luminescent characteristi…