Materials Literature
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The structure, surface acidity, and reducibility of WO 3 /SiO 2 systems, obtained by impregnation of the silica support with aqueous paratungstate solutions, are described. The effect of tungsten loading and calcination temperature on the nature and physicochemical properties of tungsten-containing phases has been stu…
The decomposition under thermal treatments of an hydrotalcite sample prepared from Mg and Al chlorides, thus containing Cl - and CO 3 2 - as compensating anions, and of the same sample totally exchanged by CO 3 2 -, was followed by several characterization techniques (in situ XRD, 27 Al NMR, TG, chemical analysis). A…
Dynamical experimental studies on the diffraction efficiencies and the formation of birefringence grating and surface relief grating on doped and/or covalently bonded azobenzene derivatives containing polymer films were carried out using laser beams with different polarizations. From polarization analyses of the first…
ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTSynthesis and Structure of Isolated Silicon Clusters of Nine AtomsVirginie Quéneau, Evgeny Todorov, and Slavi C. SevovView Author Information Department of Chemistry and Biochemistry University of Notre Dame Notre Dame, Indiana 46556 Cite this: J. Am. Chem. Soc. 1998,…
The pressure distribution beneath a conical sandpile, created by pouring sand from a point source onto a rough rigid support, shows a pronounced minimum below the apex (`the dip'). Recent work of the authors has attempted to explain this phenomenon by invoking local rules for stress propagation that depend on the loca…
A molecular mechanism explaining the chemical phenomena that occur during the preparation of silica-supported nickel catalysts by the method of deposition−precipitation is proposed. This mechanism takes into account the fact that either 1:1 nickel phyllosilicate or nickel hydroxide may be formed on silica during depos…
The effect of partial substitution of Fe by Al (Al, Al 2 O 3 ) on the magnetic properties and the corrosion resistance of the sintered NdFeB magnet has been investigated. With the increasing amount of Al, the anisotropy field and the saturation magnetization decrease, but the coercivity increases up to 4 at.% Al and f…
We have previously described an original model called the EVM (energy, volume, and mass) model, which uses only three descriptors, the energy of a polymer segment conformation using molecular mechanics and molecular dynamics, its volume (the occupied space by the atoms as well the unoccupied space between them), and t…
ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTIsocyanate as a Versatile Synthon for Modular Synthesis of Functionalized PorphyrinsJames P. Collman, Zhong Wang, and Andrei StraumanisView Author Information Department of Chemistry, Stanford University, Stanford, California 94305-5080 Cite this: J. Org. Chem. 1998, 6…
Multinuclear NMR spectroscopy has been used to study water bound to subtilisin Carlsberg suspended in tetrahydrofuran (THF), with the water itself employed as a probe of the hydration layer's physicochemical and dynamic characteristics. The presence of the enzyme did not affect the intensity, chemical shift or linewid…
The synthesis and characterization of two rhodium(I)dicarbonyl amethyrin complexes (mono and bis) are presented. X-ray structural results reveal that the amethyrin ligand undergoes significant distortion from planarity as the result of metal complexation and that, in the case of the bis-rhodium complex, the two metal…
Liquid crystals are of major technological importance for display devices, as well as being of fundamental molecular interest. Understanding how their building-block molecules arrange themselves is critical for obtaining improvements in performance. In their research commentary, Heppke and Moro discuss recent findings…
The triplet-photoexcited [5,10,15,20-tetrakis(4-sulfonatophenyl)porphinato]zinc(II) ( 3 ZnTPPS 4- ) ion underwent rapid one-electron oxidation by a series of N -alkyl-4-cyanopyridinium (C n CP + ) ions. In aqueous solution, the quenching rate constants ( k q ≅ 4 × 10 9 M -1 s -1 ) were insensitive to the N -alkyl chai…
ADVERTISEMENT RETURN TO ISSUEPREVCommunication to the...Communication to the EditorNEXTControlling the Selective Light Reflection of a Cholesteric Liquid Crystal of (Hydroxypropyl)cellulose by Electrical StimulationYoshiyuki Nishio, Toshinori Kai, Noritaka Kimura, Kazuhiro Oshima, and Hidematsu SuzukiView Author Infor…
Reaction of the ynamine MeC⋮CNEt 2 with the pentatetraenylidene complexes [(CO) 5 M C C C C C(NMe 2 ) 2 ] (M = Cr ( 3a ), W ( 3b )) at room temperature affords the new heptapentaenylidene complexes [(CO) 5 M C C C C C(NEt 2 )C(Me) C(NMe 2 ) 2 ] (M = Cr ( 5a ), W ( 5b )) in good yield. The spectroscopic data and the X-…
Bulk crystallization is emerging as a new industrial operation for protein recovery. Characterization of bulk protein crystallization is more complex than protein crystallization for structural study where single crystals are grown in flow cells. This is because both nucleation and crystal growth processes are taking…
We study monolayers formed at an air−water interface on a Langmuir trough by telechelic poly(ethylene oxide) polymers end capped with hydrophobic alkane groups (C 12 and C 16 ). The pressure−area isotherms show two plateaus: the first plateau at low coverage already exists for nontelechelic PEO and is attributed to th…
A series of perylene-containing polyimides and copolyimides have been synthesized and characterized by DSC, TGA, NMR, UV−vis, and X-ray powder diffraction measurements. Xerographic electrical measurements indicated that perfectly alternating copolyimides had higher photosensitivities than those of homopolyimides and r…
The laser-induced anisotropy in thin films of an extensive number of cyanoazobenzene side-chain liquid crystalline polytetradecanedioates, -dodecanedioates, and -adipates selectively deuterated at different positions have been investigated with polarized FTIR spectroscopy. The analysis of the segmental orientation bas…
ADVERTISEMENT RETURN TO ISSUEPREVCommunication to the...Communication to the EditorNEXTEnhancing the Degree of Branching of Hyperbranched Polymers by Postsynthetic ModificationChristian Lach and Holger FreyView Author Information Freiburger Materialforschungszentrum FMF and Institut für Makromolekulare Chemie der Albe…