Materials Literature
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The syntheses of the parent compounds [(p-Bu(t)-calix[4]-(O)2(OR)2)Fe-L] [R = Me, L = THF, 5; R = Bu(n), L = THF, 6; R = PhCH2, L = THF, 7; R = SiMe3, L = none, 8] have been performed by reacting the protonated form of the dialkylcalix[4]arene with [Fe2Mes4] [Mes = 2,4,6-Me3C6H2]. All of them undergo one-electron oxid…
A new class of amphiphilic linear−dendritic diblock copolymers based on hydrophilic linear PEO and hydrophobic dendritic carbosilane were synthesized using a divergent approach at the allyl end group of the allyl-terminated PEO. The amphiphilic nature of these block copolymers was highly dependent on the size of the h…
[reaction: see text] Diverse Lewis acids and Bronsted acids were examined in the two-step, one-flask synthesis of meso-tetraphenylporphyrin, N-confused tetraphenylporphyrin, and tetraphenylsapphyrin. The scope of acid catalysis was found to be very broad, with 35 of 45 acids providing TPP in yields ranging from 5% to…
ADVERTISEMENT RETURN TO ISSUEPREVReviewNEXTSurface Analysis: X-ray Photoelectron Spectroscopy and Auger Electron SpectroscopyNoel H. Turner and John A. SchreifelsView Author Information Department of Chemistry, George Washington University, Washington, D.C. 20052 Department of Chemistry, George Mason University, Fairf…
Quantum Monte Carlo simulations of interacting electrons in solids often use Slater-Jastrow trial wave functions with Jastrow factors containing one- and two-body terms. In uniform systems the long-range behavior of the two-body term may be deduced from the random-phase approximation (RPA) of Bohm and Pines. Here we g…
White light tunable phosphors are obtained from a sol-gel derived siliceous network to which oxyethylene units are covalently grafted by means of urea or urethane cross-linkages. The bright photoluminescence is ascribed to an unusual convolution of distinct emissions originated in the NH groups of the urea or urethane…
Titration of methacrylic acid / ethyl-acrylate copolymers is studied experimentally and theoretically. At low salt concentrations, this polyacid exhibits a plateau in the titration curve below the neutralization point. The plateau has been often attributed to a first-order phase transition associated with polymer conf…
We have developed the simultaneous optical measurement method by using the optic fiber bundles specialized for combinatorial samples combined with the arrayed charge coupled devices. This also can be used for experiments done at cryogenic temperatures. The smoother dependence upon various growth parameters could be ob…
We report high-throughput optimizations for various material parameters of Mg,Zn<SUB>1-x</SUB>O and Zn<SUB>1-x</SUB>Cd<SUB>x</SUB>O alloy films, Al-doped ZnO films, Mg<SUB>x</SUB>Zn<SUB>1-x</SUB>O/ZnO single quantum wells and superlattice structures with using combinatorial laser MBE. Combinatorial chips including nin…
Using the method of Fourier spectroscopy, the IR absorption and reflection spectra were obtained in the frequency region 240 divided by 5000 cm<SUP>-1</SUP> for different types of high- purity silica glasses (v-Sao<SUB>2</SUB>), containing from 0.1 to 10<SUP>3</SUP> ppm of the hydroxyl groups OH. The analysis of the p…
The crystal and molecular structure of a new ferroelectric [C 5 H 6 N] + ReO 4 - was determined by the x-ray diffraction method at 350 K, 293 K and 220 K. In all three phases its structure is orthorhombic, with the following sequence of space groups: Cmcm Cmc 2 1 Pbca . In the two high-temperature phases, the pyridini…
The structural parameters of nanoscale silver particles embedded in a silicate glass matrix have been determined by temperature-dependent EXAFS spectroscopy at the Ag K edge for two particle sizes of 2.5 and 6 nm. EXAFS measurements allowed us to probe both the oxygen environment of silver ions separated within the gl…
Measurements by x-ray diffraction, secondary ion mass spectrometry and atomic force microscopy are reported for single crystalline KTaO 3 after thermal treatment under oxidizing conditions in the temperature range of 700 to 1100 °C. The formation of a series of new phases KO*(KTaO 3 ) n of Ruddlesden-Popper type is ob…
Aromatic polyamides represent an important class of polymeric materials from both the academic and the industrial points of view. Unfortunately, because of strong intermolecular interactions mainly due to hydrogen bonding, their solubility in common organic solvents is often extremely poor. In most cases, this drawbac…
Thin films of symmetric diblock copolymers confined between two hard, flat and parallel surfaces have been investigated by means of Monte Carlo simulations on a simple cubic lattice. The upper surface is homogeneous, either neutral or preferential to one of the two blocks, and the lower surface is stripe-patterned, wi…
The influence of the cations on bond length, valence, and torsion angle of S4(2-) and S5(2-) anions was examined in a series of solid alkali tetra- and pentasulfides by relating their Raman spectra to their known X-ray structures through a force-field analysis. The IR and Raman spectra of BaS4.H2O and the Raman spectr…
Many petroleum companies have been using a tool developed by MPC for evaluating materials operating in the creep range. This method has now been recognized for inclusion in API RP579 on fitness-for-service. This paper reports on the method and explains the materials properties used therein. The MPC Omega method concen…
ADVERTISEMENT RETURN TO ISSUEPREVCommunication to the...Communication to the EditorNEXTPolyimides Derived from Novel Unsymmetric DianhydrideHai Bin Zheng and Zhi Yuan WangView Author Information Department of Chemistry, Carleton University, 1125 Colonel By Drive, Ottawa, Ontario, Canada K1S 5B6 Cite this: Macromolecul…
We show that in strong (quantizing) magnetic fields "ordinary" free magnetic polaron in diluted magnetic semiconductors (of type $A^2MeB^6$, where Me=Fe, Mn) exists in the form of vortex lattice quite similar to that in type II superconductors (Abricosov vortex lattice). The region of external parameters (like externa…
Molecular dynamics computer simulations which employ the embedded-atom potential show that nanowires of gold exist as multishelled structures. We simulate double-walled gold nanowires and calculate the capacitance of a finite nanometer-size cylindrical capacitor. For the sizes for which multishelled nanowires appear i…