Materials Literature
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Although colossal magnetoresistance (CMR) materials exhibit large changes in electrical resistance (up to 106%), large magnetic fields (several tesla) must be applied. To obtain a sizeable low-field effect (<102% in several millitesla), it is necessary to incorporate structural discontinuities such as grain bou…
The effect of Jahn-Teller phonons on the magnetic and orbital structure of ${\mathrm{LaMnO}}_{3}$ is investigated using a combination of relaxation and Monte Carlo techniques on three-dimensional clusters of ${\mathrm{MnO}}_{6}$ octahedra. In the physically relevant region of parameter space for ${\mathrm{LaMnO}}_{3},…
The formation of intractable β-sheet crystallites is a major cause of insolubility in proteins that can form β-sheets. To study this phenomenon, recombinant DNA techniques were used to prepare a protein modeling the consensus sequence of Nephila clavipes spider dragline silk, incorporating redox “triggering” residues.…
Using ab initio MP2 and DFT calculations, we have studied the structure of a series of pentacoordinated silicon compounds containing a Si ← N dative bond and the influence of inductive effects on the Si ← N bond. The study includes two series of model systems, namely, Si(NH 3 )X n Y 4 - n (X = OH, Y = H or CH 3; n ran…
A new class of mesostructured metal germanium sulfide materials has been prepared and characterized. The synthesis, via supramolecular assembly of well-defined germanium sulfide anionic cluster precursors and transition-metal cations in formamide, represents a new strategy for the formation of this class of solids. A…
The grain-size effect on the semiconductor-to-metal transition in ZnS has been investigated by in situ high-pressure electrical resistance and optical measurements. It is found that the grain-size effect can elevate the transition pressure of ZnS in a larger pressure range. On the basis of the results obtained and res…
We use a one-dimensional (1D) core-softened potential to develop a physical picture for some of the anomalies present in liquid water. The core-softened potential mimics the effect of hydrogen bonding. The interest in the 1D system stems from the facts that closed-form results are possible and that the qualitative beh…
Classical molecular dynamics simulations are used to examine the indentation of monolayers composed of linear hydrocarbon chains with 8, 13, or 22 carbon atoms that are chemically bound (or anchored) to a diamond (111) substrate. Indentation is accomplished using both a flexible and rigid single-wall, capped [10,10] n…
The spectral dependencies of quantum yields of photostimulated adsorption of oxygen on KBr and ZrO 2 specimens were assessed during photoexcitation into the F centers produced by preirradiation with UV light. The spectral limits of this adsorption were shifted to wavelengths longer than the absorption band edge of the…
A transition structure for the hydride transfer step in dihydrofolate reductase has been characterized in hybrid quantum-mechanical/molecular-mechanical (QM/MM) calculations involving a fully flexible active-site region by means of the GRACE software. The results are compared with in vacuo calculations and the importa…
The amplitudes and the polarizations of the different resonant reflections characterizing the modulation of the orientational order in smectic liquid crystals are derived from the molecular tensorial structure factor. In the case of a commensurate helicoidal modulation, our conclusions are consistent with the previous…
ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTFirst Synthesis of a Bidesmosidic Triterpene Saponin by a Highly Efficient ProcedureBiao Yu, Jianming Xie, Shaojiang Deng, and Yongzheng HuiView Author Information State Key Laboratory of Bioorganic and Natural Products Chemistry, Shanghai Institute of Organic Chemistr…
Crack growth in a homogeneous elastic solid under impact shear loading conditions is analyzed numerically, with the crack constrained to grow along a weak plane directly ahead of the initial crack tip. The configuration analyzed is a plane-strain model of that used in the experiments of Rosakis et al. (1999). A cohesi…
Organophosphoryl polyoxotungstate derivatives [gamma-SiW(10)O(36)(RPO)(2)](4)(-) (R = H (1), Et (2), n-Bu (3), t-Bu (4), C(2)H(4)COOH (5), Ph (6)) have been obtained by reaction of the divacant [gamma-SiW(10)O(36)](8)(-) anion with organophosphonic acids RPO(OH)(2) in acetonitrile. These new heteropolyanions have been…
Nanoscale domain engineering in ferroelectric crystals is demonstrated down to a lateral domain size of 25 nm in diameter using scanning force microscopy (SFM). The various modes of SFM are used to measure both the internal polarization field and external stray field arising from bound surface charges in ferroelectric…
Variations in the electrical and mechanical properties of silsesquioxane spin‐on‐glass thin films are examined as a function of curing time and temperature. Particular attention is paid to the trade‐off between producing low‐dielectric‐constant films, suitable for advanced microelectronic interconnection structures, a…
Aiming to clarify the mechanism of crystal nucleation of polymers, we have made a quantitative investigation about the conformational change of syndiotactic polystyrene (sPS) during the induction period (ca. 30 min) when crystallized at 120 °C, 25 K above the glass transition temperature T g = 95 °C, from the glassy s…
A simple and effective route to preparing bulk nanocrystalline (NC) pure Mg with an average grain size of 20 nm is first proposed by hydrogenation-disproportionation-desorption-recombination (HDDR) followed by spark plasma sintering (SPS) and hot extrusion (HE) techniques. NC Mg is thermodynamically super-stable again…
Siliceous hollow helicoids (Archimedian screw shapes) with spiraling mesoscale channels are the result of a new way of controlling the growth and form of hexagonal mesoporous silica. These novel helicoids (see Figure) are produced when a patch of the hexagonal silicate liquid-crystal film contracts on hydrolytic polyc…
A novel series of poly(arylidene-ether)s containing cyclopentanone was synthesized by polycondensation of 4, 4′-diformyl-α, ω-diphenoxyalkane and 4, 4′-diformyl-2, 2′-dimethoxy-α, ω-diphenoxyalkane with cyclopentanone. The polymers were characterized by elemental and spectral analyses, inherent viscosity, solubility a…