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991.
Yao D Vlessidis AG Gou Y Zhou X Zhou Y Evmiridis NP 《Analytical and bioanalytical chemistry》2004,379(1):171-177
A novel flow-injection chemiluminescence-based method has been developed for determination of superoxide dismutase (SOD) activity. An in-vitro superoxide anion generation xanthine/xanthine oxidase stable source was established on line with FIA/CL-detection apparatus, for measuring SOD activity. This method can detect SOD in the linear range of 0.002–2.00 U mL–1 with a detection limit of 0.001 U mL–1. Another method for detection of superoxide anion is based on the luminol–FeCl3 chemiluminescence (CL) reaction. This method was used to evaluate superoxide release and SOD activity in rats treated with the traditional Chinese herb Pulsatilla chinensis, which resulted in high clearance of hepatitis B virus (HBV) after treatment of a hepatitis B patient. Interestingly, we found that treatment with Pulsatilla chinensis can specifically increase superoxide release by liver tissues and, at the same time, slightly increase extracellular SOD (ECSOD) activity in plasma; in particular it can markedly increase MnSOD activity in mitochondria in liver tissue. This work revealed a possible mechanism whereby Pulsatilla chinensis prevents possible infection (for example HBV) by specifically increasing superoxide release in the liver and increasing MnSOD activity to minimize superoxide-mediated toxicity. 相似文献
992.
Guowu Yao 《Proceedings of the American Mathematical Society》2004,132(8):2483-2493
Let be a sequence of locally quasiconformal harmonic maps on the unit disk with respect to the Poincaré metric. Suppose that the energy densities of are uniformly bounded from below by a positive constant and locally uniformly bounded from above. Then there is a subsequence of that locally uniformly converges on , and the limit function is either a locally quasiconformal harmonic map of the Poincaré disk or a constant. Especially, if the limit function is not a constant, the subsequence can be chosen to satisfy some stronger conditions. As an application, it is proved that every point of the space , a subspace of the universal Teichmüller space, can be represented by a quasiconformal harmonic map that is an asymptotic hyperbolic isometry.
993.
YongHuaLI HalBinKAN BingJunYU 《数学学报(英文版)》2004,20(3):569-576
In this paper, a special kind of partial algebras called projective partial groupoids is defined.It is proved that the inverse image of all projections of a fundamental weak regular ^*-semigroup under the homomorphism induced by the maximum idempotent-separating congruence of a weak regular ^*-semigroup has a projective partial groupoid structure. Moreover, a weak regular ^*-product which connects a fundamental weak regular ^*-semigroup with corresponding projective partial groupoid is defined and characterized. It is finally proved that every weak regular ^*-product is in fact a weak regular ^*-semigroup and any weak regular ^*-semigroup is constructed in this way. 相似文献
994.
Yao Y Kleinman L MacDonald AH Sinova J Jungwirth T Wang DS Wang E Niu Q 《Physical review letters》2004,92(3):037204
We perform a first principles calculation of the anomalous Hall effect in ferromagnetic bcc Fe. Our theory identifies an intrinsic contribution to the anomalous Hall conductivity and relates it to the k-space Berry phase of occupied Bloch states. This dc conductivity has the same origin as the well-known magneto-optical effect, and our result accounts for experimental measurement on Fe crystals with no adjustable parameters. 相似文献
995.
C.H. Song J. Ma Y.Y. Yao X.M. Lu Y.N. Wang C.L. Choy 《Solid State Communications》2004,129(12):775-780
Bi4Ti3O12 (BiT), Bi3.25La0.75Ti3O12 (BLT), Bi4−x/3Ti3−xNbxO12 (BTN) and Bi3.25−x/3La0.75Ti3−xNbxO12 (BLTN) thin films have been prepared by pulsed laser deposition. BTN and BLTN films exhibit a maximum in the remanent polarization Pr at a Nb content x=0.018. At this Nb content, the BLTN film has a Pr value (25 μC/cm2) that is much higher than that of BiT and a coercive field similar to that of BiT. The polarization of this BLTN film is fatigue-free up to 109 switching cycles. The high fatigue resistance is mainly due to the substitution of Bi3+ ions by La3+ ions at the A site and the enhanced Pr arises largely from the replacement of Ti4+ ions by Nb5+ ions at the B site. The mechanisms behind the effects of the substitution at the two sites are discussed. 相似文献
996.
Hao B Zhao G Kang PT Soares JA Ferguson TK Gallucci J Krzycki JA Chan MK 《Chemistry & biology》2004,11(9):1317-1324
L-pyrrolysine, the 22(nd) genetically encoded amino acid, was previously deduced to be (4R, 5R)-4-substituted-pyrroline-5-carboxylate attached to the epsilon-nitrogen of lysine based on the crystal structure of the M. barkeri monomethylamine methyltransferase (MtmB). To confirm L-pyrrolysine's identity, structures of MtmB have been determined following treatment with hydroxylamine, N-methylhydroxylamine, or dithionite. Analysis of these structures has provided additional support for the presence of the pyrroline ring and, together with previous mass spectroscopy data, has led us to assign the C(4)-substituent to a methyl group. Based on this assignment, synthetic L-pyrrolysine was prepared by chemical methods. Detailed study of this chemically synthesized L-pyrrolysine has allowed us to characterize its physical properties, to study its chemical stability, and to elucidate the role of its C(4) substituent. Future applications of this synthetic L-pyrrolysine include its in vivo incorporation into recombinant proteins. 相似文献
997.
Here we report a simple approach to develop assays based on the hydrogelation of small molecules for quick detecting inhibitors of enzymes. 相似文献
998.
We have developed a new technique for rapid microfabrication that uses electrophoretically delivered particles and an optical trap. The material particles, micrometer- and nanometer-sized polystyrene beads in aqueous solution, are continuously delivered to an optical trap by means of the electrophoretic effect inside glass capillaries or similar microstructures. The optical trap is used to manipulate and deposit the polystyrene beads onto a substrate. The continuous, on-demand delivery of particles allows for microfabrication in two and three dimensions with high speed and high efficiency and without material waste. This new technique has many potential applications in microelectronics and biotechnology. 相似文献
999.
Multi-line laser transitions from one metastable triplet state to another at wavelengths of 2.92, 3.01, 2.69 and 2.60 μm have
been obtained through high pulse repetition frequency longitudinal discharge in a mixed gas of strontium vapor and helium
buffer gas. The intensity ratio of these laser lines was 5:4:4:1. As far as we know, these laser lines have never been reported
except for 3.01 μm. Some mechanisms for forming a population inversion are initially discussed on the basis of analyzing features
of corresponding energy-level structure and experimental phenomena. It is reasonable to name this kind of laser as an M–M
transition laser according to the feature of the lasing process.
Received: 15 October 2002 / Published online: 9 April 2003
RID="*"
ID="*"Corresponding author. Fax: +86-0571/8795-1328, E-mail: pbl66@zju.edu.cn 相似文献
1000.
L.?Si Email author Y.L.?Chang J.?Ding C.K.?Ong B.?Yao 《Applied Physics A: Materials Science & Processing》2003,77(5):641-643
In order to search for new materials for the application of magnetic refrigeration, the polycrystalline perovskite compound Nd2/3Sr1/3MnO3 was prepared by a solid-state method. The dependence of the magnetization on the applied field and temperature was measured near the Curie temperature. In terms of Maxwells equation, the temperature dependence of the absolute value of the isothermal magnetic entropy change |SM| at various applied fields from 1 T to 5 T was determined. The results showed that a large magnetic entropy change was observed in this compound. The maximum magnetic entropy change |SMmax|can reach 3.25 J/kgK with an applied field of 1 T at the Curie temperature of 257.5 K, which equals that of Gd. At 5 T applied field, it is 7.57 J/kgK. Such good magnetocaloric properties make this compound a promising candidate for the application of magnetic refrigeration in the room-temperature range. PACS 74.25.Ha; 75.30.-m; 75.30.Sg; 75.50.-y; 75.60.-d 相似文献