Materials Literature
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Abstract The local spin formalism ( Clark, A. E.; Davidson, E. R. J Chem Phys 2001, 115, 7382–7392 ) for computing expectation values 〈 S A · S B 〉 that appear in the Heisenberg spin model has been extended to semiempirical single determinant wave functions. An alternative derivation of expectation values in restricte…
Thermodynamically, polymer crystallization is a first-order transition that involves overcoming an energy barrier. Building a molecular kinetic model that links this macroscopic concept with experimental observations has been and still remains a difficult issue. It requires a physical picture that can show how a three…
The effect of frozen storage (-10 and -30 degrees C), formaldehyde, and fish oil on collagen, isolated from cod muscle, was investigated. Salt- and acid-soluble collagen fractions as well as insoluble collagen indicated changes in solubility on frozen storage. Differential scanning calorimetry (DSC) showed a highly co…
The novel five- and seven-membered ring appended aminoporphyrazines 3 and 12 have been prepared via mixed Linstead macrocyclization. The structures of both have been unequivocally established by X-ray crystallographic studies. Reductive deselenation of selenadiazole 3 in the presence of 9,10-phenanthrenequinone or 2,3…
The structure of a crystal of Sr(0.61)Ba(0.39)Nb(2)O(6) has been solved and refined as an incommensurate structure in five-dimensional superspace. The structure is tetragonal, superspace group P4bm(pp1/2,p - p1/2), unit-cell parameters a = 12.4566 (9), c = 7.8698 (6) A, modulation vectors q(1) = 0.3075 (6) (a* + b*),…
Two new benzocarbaporphyrins with four or five alkyl substituents have been synthesized by the "3 + 1" MacDonald methodology. At lower temperatures, the proton NMR spectrum of the asymmetrically substituted carbaporphyrin 8 gave two NH resonances, while carbaporphyrin 9, which retains a plane of symmetry, gave only on…
A group of twelve new and three known silicon phthalocyanines having axial ligands and peripheral groups which provide varying amounts of steric protection to the ring face and ring periphery has been assembled. These are SiPc[OSi( n -C 6 H 13 ) 3 ] 2, 1, (known), SiPc[OSi( i -C 4 H 9 ) 2 ( n -C 18 H 37 )] 2, 2, SiPc(…
Chemical recycling of poly(ethylene terephthalate) (PET) flakes to terephthalic acid (TPA) and oxalic acid was investigated by simultaneous hydrolysis and oxygen oxidation in concentrated NaOH. PET flakes were hydrolyzed to sodium terephthalate and ethylene glycol (EG) in NaOH solutions before oxygen introduction. Bec…
A new three-dimensional, random grid based cellular automaton model for the simulation of the evolution of a materials microstructure during recrystallization and grain growth is presented. The paper describes how the model can be linked to space and time coordinates and illustrates how theoretical analytical models d…
In iodine-bridged binuclear Pt compounds, ${R}_{4}[{\mathrm{P}\mathrm{t}}_{2}(\mathrm{p}\mathrm{o}\mathrm{p}{)}_{4}\mathrm{I}]n{\mathrm{H}}_{2}\mathrm{O}$ and ${R}_{2}^{\ensuremath{'}}[{\mathrm{P}\mathrm{t}}_{2}(\mathrm{p}\mathrm{o}\mathrm{p}{)}_{4}\mathrm{I}]n{\mathrm{H}}_{2}\mathrm{O}$ ($\mathrm{p}\mathrm{o}\mathrm{…
Cr 2 O 3 nanoparticles of controlled particle size were prepared by calcination of a precursor, Cr(OH) 3 , obtained by precipitation with sodium hydroxide. Samples were characterized by transmission electron microscopy and x-ray diffraction. Average particle sizes ranged from 20 to 200 nm. The magnetic properties of C…
The first example of ammoximation of bulky ketones over highly hydrophobic titanium incorporated ethane bridged hybrid mesoporous silsesquioxane with high selectivity of oximes is presented.
Recently, a new class of smectic liquid crystal phases characterized by the spontaneous formation of macroscopic chiral domains from achiral bent-core molecules has been discovered. We have carried out Monte Carlo simulations of a minimal hard spherocylinder dimer model to investigate the role of excluded volume inter…
Sandwich-type polyoxometalates (POMs), namely [WZnM2(ZnW9O34)2]q- [M = Mn(II), Ru(III), Fe(III), Pd(II), Pt(II), Zn(II); q = 10-12], are shown to catalyze selectively the epoxidation of chiral allylic alcohols with 30% hydrogen peroxide under mild conditions (ca. 20 degrees C) in an aqueous/organic biphasic system. Th…
Nano-phase transition of an organic−inorganic nanocomposite under vapor infiltration of tetraethoxysilane (TEOS) or tetramethoxysilane (TMOS) was found in mesoporous thin film preparation. The rearrangement into a hexagonal periodic structure implies high mobility of the surfactant−silicate composites in solid phase.…
Spraying cerium and zirconium precursors dissolved in carboxylic acids into a methane-oxygen flame resulted in well-structured nanocrystals of ceria-zirconia mixed oxides with high temperature stability and surface area.
Abstract For Abstract see ChemInform Abstract in Full Text.
We present a comprehensive study of the coupled tetrahedra-compound Cu2Te2O5Br2 by theory and experiments in external magnetic fields. We report the observation of a longitudinal magnon in Raman scattering in the ordered state close to quantum criticality. We show that the excited tetrahedral-singlet sets the energy s…
In recent photodoping experiments Decca et al. [PRL 85, 3708 (2000)] have observed an unusually long-ranged proximity effect between the superconducting and insulating phases of YBCO. Here we critically examine the claim in that reference that such long range is anomalous. We show that, once the novel nature of the ex…
We report thermal expansion measurements carried out on a single-crystal of the giant magnetocaloric effect material Gd5(Si0.43Ge0.57)4. At the magneto-structural phase transition at T_0 ~ 240 K, large steps in the relative length change DELTAL/L along the principle crystallographic axes are observed. The single-step…