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Grain growth in a 50:50 (vol%) dual‐phase mixture of Al 2 O 3 and c ‐ZrO 2 (cubic zirconia) is severely limited compared with that for either of the single phases. At 1650°C, the growth rates in the duplex composition are 160 and 3500 times lower than that for single‐phase Al 2 O 3 and c ‐ZrO 2 , respectively. The res…
The synthesis of silanols 2 from the corresponding silanes 1 is especially easy, if the latter are allowed to react with dimethyl or methyl(trifluoromethyl)dioxirane (1–18 min reaction time, quantitative yields of enantiomerically pure product after removal of the solvent). The experimental data are consistent with an…
Poly(viny1 chloride) (PVC) has many desirable characteristics that have allowed it to achieve its present status as one of the most important commercial polymers. In spite of its enormous technical and economic importance, PVC still possesses many problems. Its rather low stability to the influence of heat and light r…
Textural, chemical, and mineralogical analyses of authigenic clays in anthracite-rank coal and associated shale from eastern Pennsylvania have allowed a better understanding of the parameters controlling diagenesis and perhaps coalification in this region. Minerals in anthracite occur in distinct assemblages associate…
The electronic structures of CuO and ${\mathrm{Cu}}_{2}$O have been investigated by resonant photoemission at the copper 3p threshold. The experimental data from CuO are compared with the results of a cluster calculation. From this analysis we confirm the dominant ${\mathit{d}}^{8}$ character of the states between 8 a…
Abstract A series of hydrothermal experiments was performed to determine the effect of fluid abundance on the reaction of smectite to illite. Experiments were conducted on K-saturated montmorillonite (<0.1- µ m fraction) in a closed system at 250° to 400°C using run times of 1, 7, 14, 30, and 60 days at 100 MPa (1…
We outline a many-body description of the photoemission and photoabsorption processes that incorporates the multichannel treatment of the atomic dynamical excitations into the framework of multiple-scattering (MS) theory. This generalization is a most natural one, in that the internal structure of the atomic constitue…
A series of x Al 2 O 3 · (1 − x )NaPO 3 glasses (0 ≤ x ≤ 0.275) were prepared and characterized by magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy and by X‐ray photoelectron spectroscopy (XPS). 27 AI MAS NMR spectra reveal that: at low alumina contents ( x < 0.125), Al is in dominantly octahe…
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…