K. We (k + we)

Distribution by Scientific Domains

Selected Abstracts

Very High Critical Field and Superior Jc -Field Performance in NdFeAsO0.82F0.18 with Tc of 51 K,

Xiaolin Wang
A new family of oxypnictide superconductors, LaFeAsO0.89F0.11, brings new impetus to the field of high-temperature superconductivity. In this work, we show that the upper critical field values Hc2 (48 K) = 13 T and Hc2(0) can exceed 80,230 T in a high-pressure-fabricated NdO0.82F0.18FeAs bulk sample with Tc of 51 K. We also demonstrate the superior performance of supercurrent density in fields for this new superconductor. [source]

20-O-,-D-Glucopyranosyl-20 (S)-protopanaxadiol (compound K) induces expression of hyaluronan synthase 2 gene in transformed human keratinocytes and fibroblasts and increases hyaluronan in hairless mouse skin

S. Kim
Ginsenosides, the major active ingredient of ginseng, show a variety of biomedical efficacies such as anti-aging, anti-oxidation and anti-inflammatory activities. To understand the effects of 20-O-,-D-glucopyranosyl-20 (S)-protopanaxadiol (compound K), one of the major metabolites of ginsenosides on the skin, we assessed the expression level of approximately 100 transcripts in compound K-treated HaCaT cells using cDNA microarray analysis. Compound K treatment induced differential expression of 40 genes, which have been reported to be involved in the organization of the structure of the extracellular matrix as well as defense responses in human skin cells. One of the most interesting findings is a two-fold increase in hyaluronan synthase2 (HAS2) gene expression by compound K. We found that change in expression of HAS2 gene represents a specific response of HaCaT cells to compound K because hyaluronan synthase 1,3 was not changed by treatment with compound K. We also demonstrated that the compound K effectively induced hyaluronan synthesis in human skin cells and hairless mouse skin. A human clinical study indicated that topical application of compound K containing oil-in-water emulsion showed improvement of xerosis, wrinkle and fine lines in the aged skin. We concluded that compound K has anti-aging effects by the induction of HAS2 gene expression and following hyaluronan synthase. [source]

Thermodynamic calculations for molecules with asymmetric internal rotors.


Abstract The thermodynamic properties of three halocarbon molecules relevant in atmospheric and public health applications are presented from ab initio calculations. Our technique makes use of a reaction path-like Hamiltonian to couple all the vibrational modes to a large-amplitude torsion for 1,2-difluoroethane, 1,2-dichloroethane, and 1,2-dibromoethane, each of which possesses a heavy asymmetric rotor. Optimized ab initio energies and Hessians were calculated at the CCSD(T) and MP2 levels of theory, respectively. In addition, to investigate the contribution of electronically excited states to thermodynamic properties, several excited singlet and triplet states for each of the halocarbons were computed at the CASSCF/MRCI level. Using the resulting potentials and projected frequencies, the couplings of all the vibrational modes to the large-amplitude torsion are calculated using the new STAR-P 2.4.0 software platform that automatically parallelizes our codes with distributed memory via a familiar MATLAB interface. Utilizing the efficient parallelization scheme of STAR-P, we obtain thermodynamic properties for each of the halocarbons, with temperatures ranging from 298.15 to 1000 K. We propose that the free energies, entropies, and heat capacities obtained from our methods be used to supplement theoretical and experimental values found in current thermodynamic tables. 2007 Wiley Periodicals, Inc. J Comput Chem, 2008 [source]

Liquid Rb micrometric droplets confined in paraffin wax: an X-ray absorption spectroscopy study

Simone De Panfilis
We have performed high-quality X-ray absorption measurements on crystalline (c -Rb) and liquid (l -Rb) Rubidium in the range from 15 K to 320 K. Performing a consistent analysis that takes into account the contribution of the medium range structure, we observe that the l -Rb spectrum is compatible with pair correlation function g(r) previously determined by neutron diffraction experiments. Due to the micrometric size of the liquid droplets we were able to observe a slight undercooling down to 290 K. We were also able to study the details of the very strong multielectron excitations channels in terms of resonances, edges and shake-off features at proper theoretical energy values. [source]

Fabrication of Nitrogen-Containing Cordierite Ceramics

Noritaka Saito
We have investigated the crystallization behavior of cordierite-based oxynitride glass prepared by melting a powder mixture of cordierite and silicon nitride. The results indicated that two polymorphs exist: a stable ,-form, which has a low coefficient of thermal expansion, and a metastable ,-form. The time,temperature,transformation diagram of the crystallization of the ,-form shows a typical C-shaped curve that has a nose around 1420 K. Above 1373 K, the ,-form can be directly obtained by the isothermal crystallization of the oxynitride glass and the ,-form inverts to the ,-form at temperatures below 1273 K. We also have fabricated an ,-cordierite ceramic that has a nitrogen content of 1.55 mass%, which is much lower than the content of the batch composition (5 mass%); this is mainly owing to the decomposition reaction of nitrogen in the oxynitride melts and glasses during heat treatment. However, the fabricated nitrogen-containing ,-cordierite ceramics showed the coefficient of thermal expansion of 10,7 K,1, which is comparable with that of the oxide ,-cordierite ceramics. Moreover, Young's modulus of the ,-cordierite ceramics improved with the incorporation of nitrogen. [source]

Improved accuracy for the Helmholtz equation in unbounded domains

Eli Turkel
Abstract Based on properties of the Helmholtz equation, we derive a new equation for an auxiliary variable. This reduces much of the oscillations of the solution leading to more accurate numerical approximations to the original unknown. Computations confirm the improved accuracy of the new models in both two and three dimensions. This also improves the accuracy when one wants the solution at neighbouring wavenumbers by using an expansion in k. We examine the accuracy for both waveguide and scattering problems as a function of k, h and the forcing mode l. The use of local absorbing boundary conditions is also examined as well as the location of the outer surface as functions of k. Connections with parabolic approximations are analysed. Copyright 2004 John Wiley & Sons, Ltd. [source]