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491.
Oanh do T Ky PT Hang NT Yen PH Hanh TH Cuong NX Luong DV Minh CV Kiem PV 《Natural product communications》2010,5(11):1717-1720
Phytochemical study of the ethanol extract of Sarcandra glabra resulted in the isolation of two new sesquiterpenes, glabranols A (1) and B (2). Their structures were elucidated as 8alpha,9alpha,15-trihydroxylinden-4,7(11)-dien-12,8beta-olide (1) and 1beta,4alpha,7beta,11-tetrahydroxyeudesmane (2), by spectroscopic methods including 1D- and 2D-NMR and FTICR-MS. 相似文献
492.
Phan T. Nam 《Applied mathematics and computation》2009,214(2):374-380
Exponential stability of time-delay systems with nonlinear uncertainties is studied in this paper. Based on the Lyapunov method and the approaches of decomposing the matrix, a new exponential stability criterion is derived in terms of a matrix inequality, which allows to compute simultaneously the two bounds that characterize the exponential nature of the solution. Some numerical examples are also given to show the superiority of our result to those in the literature. 相似文献
493.
Dr. Caroline Barrère Christophe Chendo Dr. Trang N. T. Phan Dr. Valérie Monnier Dr. Thomas Trimaille Prof. Stéphane Humbel Dr. Stéphane Viel Dr. Didier Gigmes Prof. Laurence Charles 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(25):7916-7924
A sample pretreatment was evaluated to enable the production of intact cationic species of synthetic polymers holding a labile end‐group using matrix‐assisted laser desorption/ionization (MALDI) mass spectrometry. More specifically, polymers obtained by nitroxide‐mediated polymerization involving the MAMA‐SG1 alkoxyamine were stirred for a few hours in trifluoroacetic acid (TFA) to induce the substitution of a tert‐butyl group on the nitrogen of nitroxide end‐group by a hydrogen atom. Nuclear magnetic resonance, electrospray ionization tandem mass spectrometry, and theoretical calculations were combined to scrutinize this sample pretreatment from both mechanistic and energetic points of view. The substitution reaction was found to increase the dissociation energy of the fragile C? ON bond to a sufficient extent to prevent this bond to be spontaneously cleaved during MALDI analysis. This TFA treatment is shown to be very efficient regardless of the nature of the polymer, as evidenced by reliable MALDI mass spectrometric data obtained for poly(ethylene oxide), polystyrene and poly(butylacrylate). 相似文献
494.
Oraphin Chaikumpollert Yoshimasa Yamamoto Krisda Suchiva Phan Trung Nghia Seiichi Kawahara 《先进技术聚合物》2012,23(4):825-828
Protein‐free natural rubber was prepared by incubation of natural rubber latex with urea and polar organic solvent in the presence of surfactant. Effect of the polar organic solvent on the removal of the proteins was investigated with respect to chemical affinity and concentration of the solvents. Under a suitable condition, nitrogen content of the deproteinized natural rubber (DPNR) was 0.000 wt%, which was less than that of natural rubber deproteinized with proteolytic enzyme or urea in the presence of surfactant. The removal of all proteins from natural rubber was proved through FT‐IR spectroscopy. Changes in morphology of the DPNR were also investigated by transmission electron microscopy. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
495.
Barrère C Chendo C Phan TN Monnier V Trimaille T Humbel S Viel S Gigmes D Charles L 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(25):7916-7924
A sample pretreatment was evaluated to enable the production of intact cationic species of synthetic polymers holding a labile end-group using matrix-assisted laser desorption/ionization (MALDI) mass spectrometry. More specifically, polymers obtained by nitroxide-mediated polymerization involving the MAMA-SG1 alkoxyamine were stirred for a few hours in trifluoroacetic acid (TFA) to induce the substitution of a tert-butyl group on the nitrogen of nitroxide end-group by a hydrogen atom. Nuclear magnetic resonance, electrospray ionization tandem mass spectrometry, and theoretical calculations were combined to scrutinize this sample pretreatment from both mechanistic and energetic points of view. The substitution reaction was found to increase the dissociation energy of the fragile C-ON bond to a sufficient extent to prevent this bond to be spontaneously cleaved during MALDI analysis. This TFA treatment is shown to be very efficient regardless of the nature of the polymer, as evidenced by reliable MALDI mass spectrometric data obtained for poly(ethylene oxide), polystyrene and poly(butylacrylate). 相似文献
496.
Tyagi P Deratani A Bouyer D Cot D Gence V Barboiu M Phan TN Bertin D Gigmes D Quemener D 《Angewandte Chemie (International ed. in English)》2012,51(29):7166-7170
When pressure is applied to dynamic interactive membranes consisting of micelles composed of a triblock copolymer, their morphologies can be fine-tuned. Membranes with a range of porosities are accessible which can regulate and thereby control filtration performance and also display effective autonomous healing. 相似文献
497.
Nguyen XN Phan VK Chau VM Bui HT Nguyen XC Vu KT Hoang le TA Jo SH Jang HD Kwon YI Kim YH 《Chemical & pharmaceutical bulletin》2010,58(10):1408-1410
One new monoterpenoid glycoside, myresculoside (1), and eleven known compounds, were isolated from methanol extract of Myrica esculenta leaves by repeated column chromatography. The effects of these compounds on angiotensin I-converting enzyme (ACE) inhibition were investigated. Compounds 3 and 4 showed the most potent ACE inhibition with rates of 29.97% and 25.63% at concentration of 100 μM, respectively. Compounds 5, 6, and 11 showed weak activity with inhibitory rates of 0.07-1.41% at concentration of 100 μM. 相似文献
498.
We consider the problem of identifying a nonlinear heat transfer law at the boundary, or of the temperature-dependent heat transfer coefficient in a parabolic equation from boundary observations. As a practical example, this model applies to the heat transfer coefficient that describes the intensity of heat exchange between a hot wire and the cooling water in which it is placed. We reformulate the inverse problem as a variational one which aims to minimize a misfit functional and prove that it has a solution. We provide a gradient formula for the misfit functional and then use some iterative methods for solving the variational problem. Thorough investigations are made with respect to several initial guesses and amounts of noise in the input data. Numerical results show that the methods are robust, stable and accurate. 相似文献
499.
500.
M.H. Phan N.A. Frey M. Angst J. de Groot B.C. Sales D.G. Mandrus H. Srikanth 《Solid State Communications》2010,150(7-8):341-345
DC magnetization and AC susceptibility measurements on LuFe2O4 single crystals reveal a ferrimagnetic transition at 240 K followed by additional magnetic transitions at 225 K and 170 K, separating cluster glass phases, and a kinetically arrested state below 55 K. The origin of giant magnetic coercivity is attributed to the collective freezing of ferrimagnetic clusters and enhanced domain wall pinning associated with a structural transition at 170 K. Magnetocaloric effect measurements provide additional vital information about the multiple magnetic transitions and the glassy states. Our results lead to the emergence of a complex magnetic phase diagram in LuFe2O4. 相似文献