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A biphasic H2O–C6H6 system, which has MnIII(tetraphenylporphyrin)(Cl) and a phase transfer agent as catalysts and ascorbate as a reducing agent, activates dioxygen leading to selective epoxidation of olefins and hydroxylation of alkanes under mild conditions.
Abstract Eleven well-drained soils formed in till parent materials of varying ages in northeastern Pennsylvania were studied to determine changes in the soils with time. Four profiles (three Lackawanna and one Bath) were formed in Woodfordian till (15,000 yr B.P.), and two (Leck Kill) were formed in Altonian till (>…
The short-time self-mobilities of spherical colloidal particles in concentrated liquid suspensions were measured by photon correlation spectroscopy. For volume fractions Φ ≳ 0.3, theory incorporating two-particle hydrodynamic interactions was not adequate to describe the data, indicating the importance of many-particl…
Electrolytic polymerization of thiophene gives a metallic film with a conductivity of ca. 100 S/cm, and which becomes a semiconductive polymer with an optical absorption edge of 2.0 eV when reduced by electrochemical or chemical means.
Techniques to control metal particle size in a supported catalyst have been investigated. The mean particle size of nickel increases with an increase in the concentration of metal in the catalyst, varying from 2.2 to 25.8% in weight. The effects of metal particle size on reaction selectivity are explained in terms of…
The pyrBI operon of Escherichia coli K-12 encodes the subunits of the pyrimidine biosynthetic enzyme aspartate transcarbamylase (carbamoylphosphate:L-aspartate carbamoyltransferase, EC 2.1.3.2). Expression of this operon apparently is negatively regulated by the intracellular levels of UTP. To elucidate the regulatory…
Below the consolute point of a binary mixture, the presence of a wall which adsorbs preferentially one of the two liquids may induce a new transition, the wetting transition. Above the wetting temperature Tw the phase adsorbed by the wall forms a macroscopic film. This transition has recently been analysed in the fram…
Abstract
A unique theoretical framework is shown to interpret not less than seven different smectic phases observed or expected in polar systems. A free energy with two coupled order parameters having a tendency to condense at two incommensurate wavevectors is used.
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ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTPorphyrinic molecular metalsBrian M. Hoffman and James A. IbersCite this: Acc. Chem. Res. 1983, 16, 1, 15–21Publication Date (Print):January 1, 1983Publication History Published online1 May 2002Published inissue 1 January 1983https://doi.org/10.1021/ar00085a003RIGHTS & PERMI…
The thermal monomerization of 9-cyanoanthracene photodimer (9CNAD) single crystals has been studied using differential scanning calorimetry (d.s.c.) jointly with emission spectroscopy of cleaved surfaces of partially monomerized 9CNAD single crystals. The first exothermic peak, together with the subsequent peaks, is a…
A rapid method is presented for the determination of gypsum and related minerals in natural and synthetic materials, based on the extraction of calcium from the matrix material using slightly ammoniacal water as a solvent with subsequent complexometric titration of the calcium using EDTA. The results compare reasonabl…
A peculiarity in the variation of the shape of the dechanneling function with an increase of the tilt angle has been discovered using Rutherford backscattering and characteristic X-ray methods. The discovered effect is due to the known mechanisms of dechanneling and is described qualitatively on the basis of the Focke…
Abstract The effects of aging at 85°C on a rubber‐modified polystyrene (HIPS) have been studied as a function of aging time in both air and nitrogen. Four different types of physical measurements were carried out on the aged samples. These included mechanical relaxation measurements, tensile stress–strain measurements…
The validity of our nucleation model of deformation twinning previously proposed for fcc metals has been quantitatively examined to determine the stacking fault energy γSF from the twinning stress τT, with particular attention to the orientation dependence of τT of pure copper crystals deformed in tension at 4.2 K. Ma…
The effects of various components on the thermal expansion coefficient of low‐expansion Cu 2 O‐Al 2 O 3 ‐SiO 2 glasses were examined. When a component of glass was substituted by another oxide, the expansion coefficient always increased, except for substitution of Al 2 O 3 by B 2 O 3 . This result indicates that the e…
The designation HT 50, HT 60, and HT 80 in this paper means the grades
The purpose of this paper is to provide (a) a guide for selecting the correct type of dust palliative and application rate for a given situation, (b) information to evaluate alternatives in terms of cost and energy, and (c) application guidelines to ensure the best job for a given situation. Descriptions of current co…
Abstract 13 C‐NMR has been used to examine a number of dichlorocarbene adducts of cis ‐ and trans ‐polybutadiene prepared in a two‐phase system. Dichlorocarbene was generated by reaction of aqueous or solid NaOH or KOH with CHCl 3 in the presence of a phase transfer catalyst. Monomer compositions, comonomer sequence l…