Materials Literature
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Second neighbor dominated exchange coupling in CaV4O9 has been obtained from ab initio density functional (DF) calculations. A DF-based self-consistent atomic deformation model reveals that the nearest neighbor coupling is small due to strong cancellation among the various superexchange processes. Exact diagonalizatio…
The mechanical properties of tossa jute fibers were improved by using NaOH treatment process to improve the mechanical properties of composites materials. Shrinkage of fibers during this process has significant effects to the fiber structure, as well as to the mechanical fiber properties, such as tensile strength and…
The conductivity of the Na 2 S 2 O 7 −NaHSO 4 binary system has been measured for 15 different compositions in the full composition range, and in the temperature range 400−700 K. Phase transition temperatures were obtained, and the phase diagram was constructed. It is of the simple eutectic type, where the eutectic is…
Sideroxylonal C (3), a new phloroglucinol dimer, was isolated from the flowers of Eucalyptus albens through bioassay-guided fractionation. The structure elucidation was based on 1D and 2D NMR experiments, MS analysis, and comparison with sideroxylonals A (1) and B (2). Sideroxylonal C inhibited human plasminogen activ…
Colloidal gold nanocrystal superlattices (NCSs) were formed by ligand modification of the nanocrystal surface. The effect of different ligands was compared and it was found that dodecanethiol was most effective in forming NCSs. TEM showed that the superlattice formation from a slightly polydisperse system was a self-s…
Lamellar and hexagonal mesostructured aluminophosphates (AlPOs) were prepared and characterized. The lamellar mesostructured AlPO (APW-1) formed hydrothermally and the condensed framework was composed of alternating AlO 4 and PO 4 units. The hexagonal mesostructured AlPO (APW-2) is formed by transformation of a layere…
The electrochemical oxidation of polyaniline (PAni) films on gold electrodes is studied by simultaneous electron spin resonance (ESR) and UV−vis spectroelectrochemistry. The technique permits the separation of the superimposed UV−vis spectra of three redox states: the protonated reduced polyaniline chains, the deproto…
The classical Lifshitz-Slyozov-Wagner theory of domain coarsening predicts asymptotically self-similar behavior for the size distribution of a dilute system of particles that evolve by diffusional mass transfer with a common mean field. Here we consider the long-time behavior of measure-valued solutions for systems in…
Hexagonal UNi_4B is magnetically frustrated, yet it orders antiferromagnetically at T_N = 20 K. However, one third of the U-spins remain paramagnetic below this temperature. In order to track these spins to lower temperature, we measured the specific heat C of \unib between 100 mK and 2 K, and in applied fields up to…
In order to elucidate the nature of the ground state in the heavy-electron system PrInAg_2, we measured its specific heat for temperatures between 60 mK and 2 K in magnetic fields up to 9 T. The peak maximum of the low temperature anomaly in the specific heat (interpreted as Kondo anomaly) shifts from 0.42 K at zero f…
The chemisorption properties of differently prepared model gold/titania interfaces have been compared with the aim of gaining a better understanding of the synergistic interplay between the constituents in gold/titania catalysts used in low-temperature CO oxidation. The structurally different gold/titania interfaces w…
In part I we adapted the recent analytical mean-field theory of polymer adsorption by Semenov et al. to match the numerical lattice theory of Scheutjens and Fleer (SF). Here we calculate explicitly the contributions of trains, loops, and tails to the adsorbance and their size distributions. We choose conditions in the…
Thermal and spectroscopic investigations have been carried out on a number of glasses with a wide range of compositions in the pseudoternary glass system, Li 2 SO 4 −Li 2 O−B 2 O 3, to understand the role of sulfate ions in modifying the borate glass structure. Both nuclear magnetic resonance (NMR) and infrared (IR) s…
The photophysics and photochemistry of all-trans -α,ω-di(2-thienyl)polyenes (with chain length n = 2, 3, 4) and α,ω-di(3-thienyl)polyenes (with n = 3, 4) have been extensively studied by stationary and pulsed spectrometry. Fluorometric and laser flash techniques were used to measure the quantum yields and lifetimes of…
Reactions of hydrogen peroxide with several lacunary polyoxometalates of the 1:11 series, XW 11 O 39 m - (X = Co 3+, Ga 3+, Fe 3+, Si 4+, and P 5+ ), are reported. Synthetic pathways to new polyoxotungstates incorporating dioxygen moieties (peroxo and/or superoxo) are developed. The key step involves treating lacunary…
Selective catalytic reduction (SCR) of NO x by ethylene was investigated on copper and/or cerium ion-exchanged Al−MCM-41 in the presence of excess oxygen. Ce−Al−MCM-41 showed little activity, but Cu−Al−MCM-41 and cerium-promoted Cu−Al−MCM-41 (i.e., Ce−Cu−Al−MCM-41) were found to be active in this reaction. Higher NO x…
We have studied the adsorption and reaction of oxygen and CO on a stepped Pt surface with varying amounts of Au, using temperature-programmed desorption and reaction (TPD and TPR), low-energy electron diffraction (LEED), high-resolution electron energy loss spectroscopy, and steady-state reaction measurements. When th…
Self-assembled octadecyltrichlorosilane (CH 3 (CH 2 ) 17 SiCl 3, OTS) films were deposited on an oxidized silicon wafer. They were carefully exposed to a low-pressure oxygen direct current (dc) plasma and/or Cr vapor. Subsequently, they were characterized by X-ray photoelectron spectroscopy, near-edge X-ray absorption…
We have measured the equilibrium diameter of cylindrical poly(N-isopropylacrylamide) (NIPA) gels with submillimeter diameters under a mechanical constraint along the uniaxial direction. The linear swelling curve, diameter vs temperature, was obtained in the vicinity of the volume phase transition temperature under iso…
An adjacent dibenzotetraazaporphyrin, in which two benzene units are fused to the adjacent pyrrole rings of tetraazaporphyrin skeleton, has been synthesized as a copper complex for the first time and characterized by electronic absorption and magnetic circular dichroism spectroscopy, by cyclic voltammetry and spectroe…