223,329 research outputs found
Preparation of (R)-2-chloro-1-(m-chlorophenyl)ethanol by Lipozyme TL IM-catalyzed second resolution
No full text(R)-2-Chloro-1-(m-chlorophenyl)ethanol, a precursor of (R)-3-chlorostyrene oxide which is the key chiral intermediate for the preparation of several beta 3-adrenergic receptor agonists was prepared in 40% yield and 99% ee by the Lipozyme TL IM-catalyzed second resolution of the corresponding racemate in the presence of vinyl acetate. (C) 2012 Shi Wen Xia. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved
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The system identification and control of Hammerstein system using non-uniform rational B-spline neural network and particle swarm optimization
Get PDFIn this paper a new system identification algorithm is introduced for Hammerstein systems based on observational input/output data. The nonlinear static function in the Hammerstein system is modelled using a non-uniform rational B-spline (NURB) neural network. The proposed system identification algorithm for this NURB network based Hammerstein system consists of two successive stages. First the shaping parameters in NURB network are estimated using a particle swarm optimization (PSO) procedure. Then the remaining parameters are estimated by the method of the singular value decomposition (SVD). Numerical examples including a model based controller are utilized to demonstrate the efficacy of the proposed approach. The controller consists of computing the inverse of the nonlinear static function approximated by NURB network, followed by a linear pole assignment controller
Phlogacanthus yangtsekiangensis C. Xia & Y. F. Deng, comb. nov.
No full textPhlogacanthus yangtsekiangensis (H. Lév.) C. Xia & Y. F. Deng, comb. nov. Basionym: Strobilanthes yangtsekiangensis Léveillé (1915: 7).⎯ Cystacanthus yangtsekiangensis (H. Lév.) Rehder (1935: 315). Type:⎯ CHINA. Yunnan: Dêqên Xian, Rives du fleuve Bleu à Ta-Tchai, 400–450 m, May–June 1912, E. E. Maire s.n. (holotype E!) Cystacanthus affinis Smith (1916: 103), syn. nov. Type: ⎯ CHINA. Yunnan: Lijiang Shi, Fengkow Valley, Lat. 27°40’N ”, 8000 ft., June 1914, G. Forrest 12493 (holotype E!; isotype A!, K!). Cystacanthus yunnanensis Smith (1916: 104), syn. nov. Type:⎯ CHINA. Yunnan: Dengchuan Xian, Tengchwan Valley, Lat. 26°5’N, 7000 ft, May 1913, G. Forrest 10007 (holotype E!). Distribution:— Phlogacanthus yangtsekiangensis is endemic to China and occurs in Sichuan and Yunnan. Ecology:—This species grows in thickets in the valley at the elevation of 400–2200 m. Conservation status:— Phlogacanthus yangtsekiangensis was collected from more than thirty localities and has a large area of occurrence in Jinsha Jiang Valley in N Yunnan and SW Sichuan Provinces which cover more than 20000 km 2. It is thus considered to be of Least Concern (LC) according to the IUCN (2001, 2011) Red List criteria and categories.Published as part of Xia, Chun & Deng, Yunfei, 2013, Phlogacanthus yangtsekiangensis, a new combination in Chinese Acanthaceae, pp. 58-60 in Phytotaxa 104 (1) on pages 58-59, DOI: 10.11646/phytotaxa.104.1.9, http://zenodo.org/record/477660
Skyrmion-skyrmion and skyrmion-edge repulsions in skyrmion-based racetrack memory
No full textMagnetic skyrmions are promising for building next-generation magnetic memories and spintronic devices due to their stability, small size and the extremely low currents needed to move them. In particular, skyrmion-based racetrack memory is attractive for information technology, where skyrmions are used to store information as data bits instead of traditional domain walls. Here we numerically demonstrate the impacts of skyrmion-skyrmion and skyrmion-edge repulsions on the feasibility of skyrmion-based racetrack memory. The reliable and practicable spacing between consecutive skyrmionic bits on the racetrack as well as the ability to adjust it are investigated. Clogging of skyrmionic bits is found at the end of the racetrack, leading to the reduction of skyrmion size. Further, we demonstrate an effective and simple method to avoid the clogging of skyrmionic bits, which ensures the elimination of skyrmionic bits beyond the reading element. Our results give guidance for the design and development of future skyrmion-based racetrack memory
Microlepidoptera of Hong Kong: Oecophoridae II: description of three new species of the genus Va r i a c m a Wang
No full textWang, Shu-Xia, Yuan, Gai-Xia, Kendrick, Roger C. (2011): Microlepidoptera of Hong Kong: Oecophoridae II: description of three new species of the genus Va r i a c m a Wang. Zootaxa 2762: 31-36, DOI: 10.5281/zenodo.20144
Fig 1. – Dendrocalamus velutinus N.-H. Xia, V. T. Nguyen & V. D in Dendrocalamus velutinus N.-H. Xia, V. T. Nguyen & V. D. Vu (Poaceae), a new species from Vietnam
No full textFig 1. – Dendrocalamus velutinus N.-H. Xia, V. T. Nguyen & V. D. Vu. A. Culm and dormant bud; B. Culm sheath (abaxial view); C. Culm sheath (adaxial view); D. Leaf; E. Leaf ligule; F. Flowering branch; G. Pseudospikelet; H. Prophyll; I. Glume; J. Lemma; K. Palea; L. Pistil; M. Anther. [A-C: V. T. Nguyen NVT224, FSIV; D-M: V. T. Nguyen NVT260, FSIV] [Drawn by V. T. Nguyen]Published as part of Nguyen, Van Tho, Le, Viet Lam, Vu, Van Dung & Xia, Nian-He, 2012, Dendrocalamus velutinus N.-H. Xia, V. T. Nguyen & V. D. Vu (Poaceae), a new species from Vietnam, pp. 255-259 in Candollea 67 (2) on page 257, DOI: 10.15553/c2012v672a6, http://zenodo.org/record/571021
Finite time lyapunov exponents and extreme concentration fluctuations in 2d turbulence
No full textThe statistics of the Finite time Lyapunov exponent (FTLE) has been investigated in detail in laboratory 2D flows. The balance of the forward and backward FTLE suggests the incompressible nature of the turbulence in both the electromagnetic and Faraday wave driven experiments. The tail in the PDF of the FTLE field is correlated with the extreme concentration of the passive scale, the ‘unmixing’ events
Inactivation of human plasma kallikrein and factor XIa by protein C inhibitor
No full textThe inhibition of kallikrein and factor XIa by protein C inhibitor (PCI) was studied. The method of Suzuki et al. [Suzuki, K., Nishioka, J., & Hashimoto, S. (1983) J. Biol. Chem. 258, 163-168] for the purification of PCI was modified in order to avoid the generation of proteolytic activity and subsequent inactivation of PCI. With the use of soybean trypsin inhibitor, an efficient inhibitor of kallikrein and factor XIa, the generation of proteolytic activity was avoided. The kinetics for the inactivation of activated protein C (APC), kallikrein, and factor XIa by PCI were determined. In the absence of heparin, no inactivation of APC was observed, in contrast to kallikrein and factor XIa, which are inhibited with second-order rate constants of (11 +/- 4) X 10(4) and (0.94 +/- 0.07) X 10(4) M-1 s-1, respectively. Addition of heparin potentiated the inhibition of APC [(1.2 +/- 0.2) X 10(4) M-1 s-1] and factor XIa [(9.1 +/- 0.7) X 10(4) M-1 s-1] by PCI, whereas the inhibition of kallikrein by PCI was unchanged [(10 +/- 1) X 10(4) M-1 s-1]. The second-order rate constants for the inhibition of kallikrein or factor XIa by PCI were similar to the second-order rate constants for the inhibition of their isolated light chains by PCI, indicating a minor role for the heavy chains of both molecules in the inactivation reactions. With sodium dodecyl sulfate-polyacrylamide slab gel electrophoresis and immunoblotting, complex formation of APC, kallikrein, and factor XIa with PCI could be demonstrated. APC and kallikrein formed 1:1 molar complexes with PCI.(ABSTRACT TRUNCATED AT 250 WORDS
Inactivation of Factor XIa by Plasma Protease Inhibitors
No full textFactor XIa is a plasma protease that, by activating Factor IX, plays an important role in the early phase of the intrinsic pathway of blood coagulation. Four plasma protease inhibitors, alpha(1)-protease inhibitor, antithrombin III, C1-inhibitor, and alpha(2)-plasmin inhibitor, have been reported to inactivate human Factor XIa, but their quantitative contribution to the inactivation of Factor XIa in plasma has not been fully assessed. Using purified systems, we observed that the second-order rate constants for the reaction of Factor XIa with alpha(1)-protease inhibitor, antithrombin III, and CI-inhibitor were 4.08, 10, and 14.6 M(-1) min(-1) x 10(3), respectively. The pseudo-first-order rate constants, at plasma concentration of the inhibitors, were 1.86 x 10(-1), 4.68 x 10(-2), and 2.4 x 10(-2) min(-1), respectively. These kinetic data predict that alpha(1)-protease inhibitor should account for 68%, antithrombin III for 16%, and C1-inhibitor and the equipotent alpha(2)-plasmin inhibitor each for 8% of the total inhibitory activity of plasma against Factor XIa. The rate of inactivation of Factor XIa in various plasma samples specifically deficient in inhibitors was consistent with these predictions.Factor XI, the zymogen form of Factor XIa, circulates in plasma associated with the contact system cofactor, high molecular weight kininogen (HMW kininogen). Kinetic analysis indicated the existence of a reversible bimolecular Factor XIa-HMW kininogen complex with a dissociation constant (K(d)) = 0.17 muM. The light chain derived from HMW kininogen decreased the inactivation rate of Factor XIa by C1-inhibitor with a K(d) of 0.08 muM for a complex of Factor XIa and the light chain derived from HMW kininogen. The protective effect of HMW kininogen was confirmed by the finding that the inactivation rate of Factor XIa in kininogen-deficient plasma was increased over normal plasma.The present study confirms that alpha(1)-protease inhibitor is the major inhibitor of Factor XIa in plasma, and that the formation of a reversible complex between Factor XIa and HMW kininogen decreases the rate of inactivation of the enzyme by its inhibitors
Inhibition of Factor XIa by Antithrombin I11
Get PDFThe inactivation of human factor XIa by human antithrombin III was studied under pseudo-first-order reaction conditions (excess antithrombin III) both in the absence and in the presence of heparin. The time course of inhibition was followed by using polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. After electrophoresis, proteins were blotted onto nitrocellulose and stained either for glycoprotein or for antithrombin III using antibodies against antithrombin III. Concomitant with factor XIa inactivation, two new slower migrating bands, one of which represented the intermediate complex consisting of one antithrombin III complexed with factor XIa, appeared as a transient band. Complete inactivation resulted in a single band representing the complex of factor XIa with two antithrombin III molecules. Quantitative analysis of the time course of inactivation was accomplished by measurement of the disappearance of factor XIa amidolytic activity toward the chromogenic substrate S2366. Pseudo-first-order reaction kinetics were observed throughout. The rate constant of inactivation was found to be 10(3) M-1 s-1 in the absence of heparin and 26.7 X 10(3) M-1 s-1 in the presence of saturating amounts of heparin. From the kinetic data, a binding constant (Kd) of 0.14 microM was inferred for the binding of antithrombin III to heparin. The time course of inactivation and the distribution of the reaction products observed upon gel electrophoresis are best explained assuming a mechanism of inactivation in which the two active sites present in factor XIa are inhibited in random order (i.e., independent of each other) with the same rate constant of inhibition
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