Materials Literature
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Zeolite molecular sieves catalyse the cleavage of carbon–carbon double bonds of various alkenes in the presence of aqueous hydrogen peroxide as an oxidant; titanium silicate molecular sieves, TS-1 and TS-2 exhibit very high activity in the conversion of α-methylstyene into acetophenone.
A series of enthalpy relaxation measurements were carried out for the pure polymers polystyrene (PS) and poly(oxy-2,6-dimethyl-1,4-phenylene) (PPE) and for homogeneous blends thereof. The data were analyzed using Moynihan's four-parameter approach.4 For the pure components the best fit parameter values for the simple…
Preparation of chemically homogeneous cordierite powders of submicrometer size was investigated using alkoxide precursors, synthesized from Mg metal, Al(OBu s ) 3 , and partially prehydrolyzed Si(OEt) 4 . The amount of partial prehydrolysis water in precursor synthesis was changed to study the effects on the hydrolysi…
The crystallography of B2→7R stress-induced martensitic transformation in a Ni-37.0 at%Al alloy was studied using single crystals. The experimental results were compared with predictions of the phenomenological crystallographic theory. The simultaneously measured habit planes and the orientation relationship between p…
Time-resolved powder neutron diffraction has been used to study, in situ, the structural transformations and changes in the hydrogen-atom content of four ion-exchanged (Ca, K, Mg and Na) vermiculites and two natural (Ca and Na) montmorillonites undergoing dehydration. The loss of interlayer water is shown to occur in…
X-Ray absorption near-edge structure and extended X-ray absorption fine structure spectroscopies have been used to characterize iron basket-handle porphyrins in various co-ordinations, stereochemistries and oxidation states. Attention is paid to the square-planar iron(II) complexes, a dioxygen adduct of FeII and a hyd…
Thin films of tin‐doped (ITO for indium tin oxide) with different tin contents produced by a powder pyrolysis technique have been investigated by x‐ray absorption spectroscopy and x‐ray diffraction. In a previous paper, an extended x‐ray absorption fine structure (EXAFS) study at the indium K‐edge and diffraction meas…
Escherichia coli purB encodes adenylosuccinate lyase (ASL), the enzyme that catalyzes step 8 in the pathway for de novo synthesis of IMP and also the final reaction in the two-step sequence from IMP to AMP. Gene purB was cloned and found to encode an ASL protein of 435 amino acids having a calculated molecular weight…
Donor-substituted 4-N-methylstilbazolium toluene-p-sulfonate salts and related salts containing cations with extended conjugation exhibit an unusually high propensity to crystallize in non-centrosymmetric space groups. The new compound 3′,4′-dihydroxy-4-N-methylstilbazolium toluene-p-sulfonate crystallizes in the spac…
The crystal structure of formylurea, C2H4N2O2, has been solved and refined from X-ray powder diffraction data collected on a conventional laboratory diffractometer; this is the first previously unknown organic structure containing only light atoms to be solved by this technique, and suggests that powder diffraction ha…
The behavior of iron hydride was studied by in situ X-ray observations at 6GPa up to 700°C. When the iron-hydrogen system was heated, the dissolution of hydrogen into iron occurred, and bcc iron changed into iron hydride with a dhcp structure passing through a hcp structure, and then transformed into an fcc structure.…
Different dielectric fluids used in HV electrical components were subjected to AC stresses, and the partial discharge (PD) spectra produced under nonuniform and uniform field conditions were recorded with the help of an electrical detector and a multichannel analyzer (MCA) as a function of applied stress. The analysis…
A preliminary presentation is given of a model which explains the picritic lunar mare green glass compositions as composites or magmas derived by polybaric fractional melting. The model accommodates changes in source composition and solidus temperature. As in the Klein and Langmuir model, the final compositions of the…
The nonlinear optical characteristics of AgGaS/sub 2/ were investigated by measuring visible parametric fluorescence with a pump wavelength of 600 nm. A value of d/sub 36/ (AgGaS/sub 2/)=31+or-5*10/sup -12/ m/V for the nonlinear coefficient was determined. The temperature dependence of phase matching up to 100 degrees…
One barrier to producing wood-plastic composites with wood fiber is the poor thermoplasticity of wood fiber. The objective of our study was to determine the plasticization of chemically modified wood fiber through tests on unmodified and esterified fiberboards. Attrition-milled aspen fiber was esterified with neat ace…
Single crystals of bis(1,2,5-thiadiazolo)-p-quinobis(1,3-dithiole)(BTQBT) were grown either by recrystallization from a nitrobenzene solution or by sublimation in nitrogen atmosphere The electrical resistivities were 1.2 × 103Ω cm and 2.7 × 105Ω cm at room temperature for a crystal grown by recrystallization and that…
Abstract Like a liquid solvent, poly(ethylene oxide) dissolves a wide variety of inorganic salts. Ionic conductivity occurs in the amorphous region of the polymer and typically both anions and cations are mobile to some extent. This paper discusses the preparation, thermal behaviour and ionic transport of thin cast fi…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTRapid synthesis of gallium phosphide and gallium arsenide from solid-state precursorsRandolph E. Treece, Gerald S. Macala, and Richard B. KanerCite this: Chem. Mater. 1992, 4, 1, 9–11Publication Date (Print):January 1, 1992Publication History Published online1 May 2002Publis…
A low-energy electron micorscope (LEEM) corrected for spherical and chromatic aberration is proposed which can operate at different imaging modes. The microscope consists of a conical electromagnetic immersion objective lens, a mirror-hexapole corrector, an electron source, and a projector system, which are symmetrica…
A flux linkage model for a three-phase five-legged transformer is derived for the first time. The effects of mutual and leakage inductances, saturation, eddy current loss, hysteresis and residual fluxes of the nonlinear iron core are included. A straightforward and novel method for determining both the apparent and in…