Materials Literature
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Molecular geometries, dipole moments, polarizabilities and first-order hyperpolarizabilities for five classic donor−aromatic π system−acceptor NLO chromophores were calculated, using semiempirical methods (PM3), in both vacuum and solvent environments. Solvent effects on the computed molecular geometries were found to…
We present results of the energies of formation and hydration of small clusters and rings containing Si and Al; the results provide a rationalisation of Lowenstein's rule in terms of the energetics of species containing Al–O–Al bridges.
A homogeneous catalytic system based on a suitable Ni(II) diimine derivative and methylaluminoxane affords predominantly syndiotactic polypropylene at subambient temperatures. The polymer microstructure is that expected for a “chain-end” mechanism of steric control. NMR analysis of polymer samples carrying selectively…
The luminescence properties of Bi3+, Eu3+, Dy3+ and energy transfer from Bi3+ to Dy3+ and Eu3+ have been studied in two modifications of Y2SiO5(low-temperature X1 type and high-temperature X2 type) and discussed in relation to their crystal structures. The Bi3+ ion luminesces in the blue region of the spectrum in X1-Y…
Beryllium oxide(BeO)-doped (0.3, 0.6, 0.9, 1.2 and 13.6 wt%) UO2 pellets were fabricated to evaluate the effects of BeO precipitate shape on thermal conductivity. Precipitate distributions were of two types: BeO precipitated almost continuously along a grain boundary (designated BeO continuous type) and spherical BeO…
A heterogeneous reactor model was developed describing kinetic experiments on the heterogeneously catalyzed oxidative coupling of methane in a laboratory fixed-bed reactor. The catalyst produces radicals which react further through gas-phase reactions in the pores of the catalyst and in the interstitial phase. The rea…
Application of thermosensitive polymers as an embolic material for intravascular neurosurgery was investigated. We intended to use thermosensitive polymers to occlude vessels by precipitation in response to body temperature. Copolymers of N-isopropylacrylamide (NIPAM) and N-n-propylacrylamide (NPAM) were selected as t…
Ultrapure poly(vinyl alcohol) (PVA) hydrogels were prepared by exposing an aqueous solution of 15 or 20 wt% PVA to repeated cycles of freezing for 6 or 12 h at -20 degrees C and thawing for 2 hours at 25 degrees C. The adhesive characteristics of the PVA gels in contact with a reconstituted mucus surface were quantifi…
This paper presents a study of the effect of important fabric mechanical properties on drape. The study uses a mathematical modeling technique to simulate fabric drape. Young's modulus in the warp and weft directions, shear modulus, Poisson's ratio, and fabric thickness are the parameters studied in this work. Results…
Two new water soluble squaraine dyes, bis[3-( p -carboxybenzyl)benzothiazol-2-ylidene]squaraine (Sq1) and bis[3-(carboxymethyl)benzothiazol-2-ylidene]squaraine (Sq2), have been synthesized and their photophysical properties have been characterized. Sq1 and Sq2 form dimer aggregates in water that have absorption bands…
The interaction of ATP with the active site of hexokinase is unknown since the crystal structure of the hexokinase-ATP complex is unavailable. It was found that the ATP binding site of brain hexokinase is homologous to that of actin, heat shock protein hsc70, and glycerol kinase. On the basis of these similarities, th…
The Raman spectra of AlCl(3)-LiCl-dimethylsulfone mixtures with different molar compositions have been recorded as a solid (300 K) and as a melt (400 K). In any case, only AlCl(4)(-) ion lines at 120, 179, and 347 cm(-)(1) were observed; we were unable to detect any other chloroaluminate species. Furthermore, some ban…
General expressions for Poisson's ratio are derived for arbitrary orientations of crystals in the tetragonal, hexagonal, and cubic systems; simplified forms are given for cases involving symmetry directions.
A systematic variation of the V 2 O 5 content of the title catalysts reveals a dependence of the activation energy of the selective catalytic reduction of nitric oxide by ammonia on the surface concentration of vanadia. A significant decrease in activation energy (from approximately 80 to 40 kJ/mol) is observed, as th…
Many important crystalline materials do not form single crystals of sufficient size and/or quality for single-crystal diffraction studies, and in such cases it is essential that the crystal structure can be solved from powder diffraction data; however, there are many difficulties associated with solving crystal struct…
Boronic acid-appended spiropyrans have been synthesized in order to detect diols and sugars by a colour change: only when the boron atom could intramolecularly interact with the tertiary amine in the spiropyran moiety, did added diols and sugars change the shift of the spiropyran–merocyanine equilibrium, which was vis…
We have constructed a new class of polymer gel that undergoes translational and rotational motions in water. These polymer gels consist of cross-linked hydrophobic−hydrophilic copolymers, which swell in water-miscible organic fluid but collapse in water. When these gels swollen in organic solvent are placed on support…
A synthesis of meso-substituted porphyrins in anionic sodium dodecyl sulfate micelles has been developed. Polar, functionalized aromatic aldehydes condense reversibly with pyrrole in the micellar phase. Oxidation of the porphyrinogen then provides functionalized porphyrins in yields of 10-48%. Hydrophobic aldehydes co…
Monolithic samples of highly porous poly(styrene/DVB) PolyHIPE® have undergone a number of electrophilic aromatic substitution reactions, namely sulfonation, nitration and bromination. Mild, hydrophobic reagents and homogeneous reaction conditions were sought in an effort to achieve uniform chemical modification, to a…
The anion ClO 4 - and the ion pair of Li + ClO 4 - have been studied by ab initio quantum chemical methods. Optimized geometries for monodentate, bidentate, and tridentate structures have been determined up to the MP2/6-311+G* level of theory. Vibrational frequencies were determined for the ClO 4 - anion and the Li +…