Materials Literature
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We report constant-pressure Monte Carlo simulations of a system of hard ellipses with aspect ratios k=2, 4, and 6. The results show three different phases: isotropic, nematic, and solid, except for k=2, where no nematic phase is formed. In all cases the fluid-solid transition appears to be first order. However, the is…
Motions of small molecules in an amorphous polymer below its glass transition temperature Tg have been studied using molecular dynamics simulation. An infinite length chain model having 600 interacting sites, each representing a CH2 unit, is used. The system, which is composed of the infinite length chain and ten sphe…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTPolyoxometalate systems for the catalytic selective production of nonthermodynamic alkenes from alkanes. Nature of excited-state deactivation processes and control of subsequent thermal processes in polyoxometalate photoredox chemistryRoman F. Renneke, Marzia Pasquali, and C…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTAlkene oxidation catalyzed by a ruthenium-substituted heteropolyanion, SiRu(L)W11O39: the mechanism of the periodate-mediated oxidative cleavageRonny Neumann and Chalil Abu-GnimCite this: J. Am. Chem. Soc. 1990, 112, 16, 6025–6031Publication Date (Print):August 1, 1990Public…
Negatively charged ions with significantly different radii, e.g. Cl⊖, Br⊖ and I⊖, can be encapsulated as guest molecules in VO-cluster shells such as {V18O42} 1. According to X-ray structure analyses the encapsulated ions are fixed in the center of 1 and are surrounded by 18 V atoms and 24 O atoms. The distance from…
Anaerobically growing Escherichia coli cells contain the enzyme pyruvate formate-lyase which catalyses the non-oxidative cleavage of pyruvate to acetyl-CoA and formate. The enzyme is subject to interconversion between inactive and active forms. The active form contains an oxygen-sensitive organic free radical located…
D-Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) from Thermotoga maritima, a hyperthermophilic eubacterium, has been isolated in pure crystalline form. The enzyme is a homotetramer with a subunit molecular mass of 37 kDa. The sedimentation coefficient of the native enzyme is 7.3 X 10(-13)s, the isoelectric point is…
Abstract The MM3 molecular mechanics program has been extended to conjugated systems. A VESCF method is applied to the pi‐system to calculate bond orders, from which various stretching and torsional parameters are obtained. The procedure gives somewhat better results than the analogous MM2 calculations. It has been ap…
Methanothermus fervidus grows optimally at 83 degrees C. A protein designated HMf (histone M. fervidus) has been isolated from this archaeal hyperthermophile that binds to double-stranded DNA molecules and increases their resistance to thermal denaturation. HMf binding to linear double-stranded DNA molecules of greate…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTEnhanced oxygen storage capacity of cerium oxides in cerium dioxide/lanthanum sesquioxide/alumina containing precious metalsTakeshi. Miki, Takao. Ogawa, Masaaki. Haneda, Noriyoshi. Kakuta, Akifumi. Ueno, Syuji. Tateishi, Shinji. Matsuura, and Masayasu. SatoCite this: J. Phys…
Optical absorption measurements of the 2.0-eV band and photoluminescence measurements of the 1.9-eV emission, excited by various excitation bands, were carried out on high-purity silica glasses subjected to γ-ray irradiation. Two, and possibly three, different forms of nonbridging oxygen hole centers were deconvoluted…
Abstract The crystal structures of (BEDT–TTF)2[MHg(SCN)4] (M=K at 298 and 104 K and M=NH4 at 298 K) were determined by X-ray analyses. A donor layer and an anion sheet stack alternately along the b-axis. The packing pattern of the donor is close to α-phase, while an anion sheet constructs a thick two-dimensional polym…
The spin and orbital contributions to the magnetic moments of Fe, Co, and Ni are calculated from first principles, using the linear muffin-tin orbitals method with the spin-orbit coupling treated at each variational step. In these calculations the spin and orbital moments agree with previously reported results obtaine…
Abstract— Excited state emission and absorption decay measurements have been made on the cage‐type cryptate complexes [M bpy.bpy.bpy] n+ , where M n+ = Na + , La 3+ , Eu 3+ , Gd 3+ or Tb 3 + and [bpy.bpy.bpy] is a tris‐bipyridine macrobicyclic cryptand. Excitation has been performed in the high intensity 1 π‐π* crypta…
Structure and morphology of polycrystalline diamond films prepared by chemical vapor deposition (CVD) have been studied using x-ray texture analysis, angle-resolved optical reflection, and scanning electron microscopy. The films under investigation exhibit a pronounced 110 fiber texture, i.e., a preferential alignment…
An investigation of the interrelationships between strength, crack‐resistance ( R ‐curve) characteristics, and grain size for alumina ceramics has been carried out. Results of identation‐strength measurements on high‐density aluminas with uniform grain structures in the size range 2 to 80 μm are presented. A theoretic…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTPredicting the stability of cyclic disulfides by molecular modeling: effective concentrations in thiol-disulfide interchange and the design of strongly reducing dithiolsJohn A. Burns and George M. WhitesidesCite this: J. Am. Chem. Soc. 1990, 112, 17, 6296–6303Publication Dat…
Using the trace gas diffusion method, the vapour resistance of three clothing ensembles (two permeable and one impermeable) was determined for four subjects, sitting, standing or walking at 0-3 and 09 m/s, combined with three wind speeds of <0-15, 0-7 and 41 m/s. Sitting increased vapour resistance by 12-36%, whereas…
Despite extensive study over the years, the chemical processes involved in the atmospheric corrosion of iron and its alloys remain poorly understood. Most conceptual studies have ignored the chemical influence of the trace anions (Cl − , , , , etc.) present in the atmosphere and in precipitation. This review, presente…
The pitting and intergranular corrosion behavior of alloy AA(1) 2090 (Al-2Li-3Cu, UNS(2) A92090) in a 3.5 wt% NaCl solution was investigated. Techniques used included potentiodynamic polarization, galvanic couples, and pH measurements in simulated crevices. Polarization scans were performed on under-aged and peak-aged…