Materials Literature
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Electrochemical doping of bisulfate ions into single wall carbon nanotube (SWNT) bundles has been studied using coulometry, cyclic voltammetry, mass-uptake measurements, and Raman scattering experiments. A spontaneous charge-transfer reaction is observed prior to the application of an electrochemical driving force, in…
Diffractive optical elements are rapidly finding their way into many practical optical systems, and this has given rise to a spurt of research and developmental activities in this area. IN this paper, the history of these elements is first traced to get a perspective on their current state-of-the- art. The important f…
The concept of characteristic curves (CCs) for analysing the behaviour of limit cycles in elementary DC-DC switching converters is introduced. The CC is derived by considering opposite vector fields in the on and off configurations. Feedback regulated converters with PWM or hysteresis control are investigated using th…
Phosphorescence and optically detected magnetic resonance (ODMR) measurements are reported on four single-tryptophan mutants of lac repressor protein from Escherichia coli: H74W/Wless, W201Y, Y273W/Wless, and F293W/Wless, where Wless represents a protein background containing the double mutation W201Y/W220Y. The singl…
1 H NMR chemical shift assignments were established for N δ 1 H (16.9 ppm) and N ε 2 H (16.1 ppm) of the active-center His57 for the complex of MeOSuc-Ala-Ala-Pro-boroPhe (BoroPhe) with chymotrypsin and for the C ε 1 H proton (9.2 ppm at low pH and 8.5 ppm at high pH) of His57 in uncomplexed chymotrypsin. The assignme…
The pentameric array of canted porphyrins (3‘TPyP)[Ru(TPP)(CO)]4 (1) (3‘TPyP = 5,10,15,20-tetra(3‘-pyridyl)porphyrin, TPP = meso-tetraphenylporphyrin) was synthesized by axial coordination of the 3‘N pyridyl groups of 3‘TPyP to the ruthenium core of four Ru(TPP)(CO) units; a thorough spectroscopic characterization of…
Ordered arrays of ∼4.5 nm diameter silver nanocrystals passivated with dodecanethiol show remarkable thermal stability at temperatures up to 975 K. Defects in the ordered-assembly were the first areas to show signs of melting while much of the structure remained intact. The mechanism for their stability is attributed…
Second and third generation silylalkoxy-terminated carbosilane dendrimers have been used to make high surface area xerogels via an acid-catalyzed sol-gel protocol. These xerogels are micro- and mesoporous and contain a high degree of −OH functionality. An unexpected trend with respect to dendrimer generation and xerog…
Lanthanide nitrate reacted with H2salen at room temperature in MeOH/CH2Cl2 affording a novel polymeric chain complex, [La(H2salen)(NO3)3(MeOH)2]n. The complex displayed an unusual coordination pattern where the imine nitrogen atoms of the H2salen molecule were not coordinated. Instead, the two phenolic oxygen atoms, w…
Microporous silica materials with a controlled pore size and a narrow pore size distribution have been prepared by sol−gel processing using an organic-templating approach. Microporous networks were formed by pyrolytic removal of organic ligands (methacryloxypropyl groups) from organic/inorganic hybrid materials synthe…
Conventional wisdom maintains that β isomers of fully oxidized Keggin heteropolytungstates, [X n + W VI 12 O 40 ] (8 - n ) - (X = main-group or transition-metal cation), are unstable with respect to α structures such that isomeric rearrangements all occur in the direction β → α. Contrary to this view, equilibria betwe…
Intramolecular electron transfers within the mixed valence states of the ligand bridged hexaruthenium clusters Ru 3 (μ 3 -O)(μ-CH 3 CO 2 ) 6 (CO)(L)(μ-L‘)Ru 3 (μ 3 -O)(μ-CH 3 CO 2 ) 6 (CO)(L) (L‘ = 1,4-pyrazine; L = 4-dimethylaminopyridine ( 1 ), pyridine ( 2 ), 4-cyanopyridine ( 3 ), or L‘ = 4,4‘-bipyridine; L = 4-di…
The elastic constant tensors for the hcp phases of three transition metals (Co, Re, and Fe) are computed as functions of pressure using the Linearized Augmented Plane Wave method with both the local density and generalized gradient approximations. Spin-polarized states are found to be stable for Co (ferromagnetic) and…
An effective Hamiltonian is derived in the case of the strong Hund coupling and on-site Coulomb interaction by means of a projective perturbation approach. A physical mechanism for charge ordering in half-doped manganites (R_{0.5}X_{0.5}MnO_3) is proposed. The virtual process of electron hopping results in antiferroma…
A new class of polyimide/silica composites with chemical bonds between the polyimide and silica network has been synthesized by the sol−gel reaction and characterized. The hybrid composite films were obtained by the hydrolysis and polycondensation of (3-aminopropyl)triethoxysilane (APTES) and tetraethoxysilane (TEOS)…
A colossal shift of the maximum resistivity temperature induced by oxygen isotope exchange was registered for 60 nm thick films of the solid solution La0·35Pr0·35Ca0·3MnO3 on perovskite substrates. The magnitude of the effect depends on lattice strain resulting in the largest shift for the film on LaAlO3: the 16O samp…
Monolayers of oligothiophene-substituted alkylsilanes, chlorodimethyl(11-(3-(2,2‘bithienyl))undecyl)silane and chlorodimethyl(11-(3‘-(2,2‘:5‘,2‘ ‘-terthienyl))undecyl)silane, are subject to electrochemical oxidation within the monolayer to afford more highly conjugated oligomers with lower redox potentials. The electr…
The complex (6,13-bis(ethoxycarbonyl)-5,14-dimethyl-1,4,8,11-tetraazacyclotetradeca-4,6,12,14-tetraenato(2−))iron(III) iodide, 3 (chemical formula C 18 H 26 O 4 N 4 FeI·0.5 C 7 H 8 ), has been characterized by X-ray crystallography ( a = 16.063(3) Å, b = 15.895(3) Å, c = 19.703(4) Å, β = 107.11(3)°; monocline; I 2/ a;…
ADVERTISEMENT RETURN TO ISSUEPREVCommunication to the...Communication to the EditorNEXTA Self-Assembled Electric Conductive Network in Short Carbon Fiber Filled Poly(methyl methacrylate) Composites with Selective Adsorption of PolyethyleneGuozhang Wu, Shigeo Asai, and Masao SumitaView Author Information Department of…
A critical review is given of the physics of colossal magnetoresistance (CMR) materials (manganites and other degenerate ferromagnetic semiconductors). The basic idea is that their specific properties (the resistivity peak close to T C, CMR and so on) are not related to the electron{lattice interaction but are caused…