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71.
A heavy and hard peak-shaped inclusion in an elastic body provokes to concentration of eigenvalues in the low-frequency range of the spectrum and localization of the corresponding eigenmodes near the peak tip. To cite this article: S.A. Nazarov, C. R. Mecanique 335 (2007). 相似文献
72.
We consider a quasistatic problem of frictional contact between a viscoelastic body and a moving foundation. The contact is with wear and is modeled by normal compliance and a law of dry friction. The novelty in the model is that it allows for the diffusion of the wear debris over the potential contact surface. Such kind of phenomena arise in orthopaedic biomechanics and influence the properties of joint prosthesis. We derive a weak formulation of the problem and state that, under a smallness assumption on the problem data, there exists a unique weak solution for the model. To cite this article: M. Shillor et al., C. R. Mecanique 331 (2003). 相似文献
73.
Nearly repetitive structures can present at least two kinds of vibration modes: localized modes and modulated ones. In this Note, the multiple scale method is applied to characterize a packet of modulated modes. In this respect, only small size problems are to be solved: periodic problems posed on a few basic cells and amplitude equations, which define a sort of homogenized model for this type of modes. It is established that the influence of the non-repetitive part of the structure is accounted by a boundary condition. To cite this article: E.M. Daya et al., C. R. Mecanique 331 (2003). 相似文献
74.
El Mostafa Daya Bouazza Braikat Noureddine Damil Michel Potier-Ferry 《Comptes Rendus Mecanique》2002,330(5):333-338
By homogenization theory, one can predict the vibrations of long repetitive structures in the low frequency range. Beyond this range, many modes have a modulated shape. Based on a multiple scale analysis, a continuum model is presented, that is able to account for this class of modes. This model involves a real coefficient that can be computed from the finite element resolution of problems defined on a few basic cells. An application in 2D elasticity is presented. To cite this article: E.M. Daya et al., C. R. Mecanique 330 (2002) 333–338. 相似文献
75.
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77.
We describe here an analytical method of A431 cell membrane chromatography (A431/CMC) (CMC, cell membrane chromatography) combined with RPLC for recognition, separation, and identification of target components from traditional Chinese medicines (TCMs) Radix Caulophylli. The A431 cells with high expressed epidermal growth factor receptor (EGFR) were used to prepare the stationary phase in the CMC model. Retention fractions on the A431-CMC model were collected using an automated fraction collection and injection module (FC/I). Each fraction was analyzed by RPLC under the optimized conditions. Gefitinib and erlotinib were used as standard compounds to investigate the suitability and reliability of the A431 cell membrane chromatography-RPLC method prior to screening target component from Radix Caulophylli total alkaloids. The results indicated that caulophine and taspine were the target component acting on the epidermal growth factor receptor. This method could be an efficient way in drug discovery using natural medicinal herbs as a source of novel compounds. 相似文献
78.
A high-performance liquid chromatography (HPLC) coupled with triple quadrupole mass spectrometry (MS/MS) method was developed for rapid determination of 13 isoflavones in Radix puerariae. A novel shell-type column, namely Kinetex core-shell C(18) column (50 mm×2.1 mm id, 2.6 μm), and gradient elution were used during the analysis. The chromatographic peaks of 13 investigated compounds were identified by comparing their retention time and MS data with the related reference compounds. Multiple-reaction monitoring (MRM) was employed for the quantitative analysis with negative ionization mode. All calibration curves showed good linearity (r(2)>0.9990) within test ranges. The LOD and LOQ were lower than 0.017 and 0.873 μg/mL on column, respectively. The intra- and inter-day precisions for 13 analytes were <1.17 and 2.17%, respectively, and the recoveries were 93.1-104.4%. The validated method was applied for quantitative analysis of 13 isoflavones in 7 species of Radix puerariae. The result demonstrated that HPLC-MS/MS system with Kinetex column could be a promising analytical tool for the determination of isoflavones in traditional Chinese medicines, which is helpful for comprehensive evaluation of quality of R. puerariae. 相似文献
79.
We developed a simple, rapid and reliable method for determination of 20 common amino acids based on derivatization with 9‐fluorenylmethyl chloroformate (FMOC‐Cl) and RP‐LC/UV, this method was first introduced into quantitative analysis of amino acids. The amino groups of amino acids were trapped with FMOC‐Cl to form amino acid‐FMOC‐Cl adducts which can be suitable for LC‐UV. Chromatographic separation was performed on a C18 column with a mobile phase gradient consisting of acetonitrile and sodium acetate solution. This method was shown to be sensitive for 20 common amino acids. In the intra‐day precisions assay, the range of RSDs was 3.21‐7.67% with accuracies of 92.34‐102.51%; for the inter‐day precisions assay, the range of RSDs was 5.82‐9.19% with accuracies of 90.25‐100.63%. The results also indicated that solutions of amino acids‐FMOC‐Cl can be kept at room temperature for at least 24 h without showing significant losses in the quantified values. The validated method was successfully applied to the determination of major four kinds of amino acids in R. isatidis samples (Arg, Pro, Met and Val). The total content of amino acids in different origin R. isatidis was 13.32‐19.16 mg/g. The differences between R. isatidis samples were large using HCA. 相似文献
80.
Polyacetylenes are main toxic ingredients in Bupleurum longiradiatum, a poisonous plant that has ever been misused as substitutes for Chaihu (Bupleuri Radix). For the first time, a high-performance liquid chromatography method coupled with diode array detector and mass spectrometry (HPLC-DAD-MS) was developed for qualitative and quantitative analysis of nine polyacetylenes in Bupleurum species. All references, including two new polyacetylenes, were isolated from B. longiradiatum and purified using a semi-preparation HPLC chromatography. The analysis was performed on a TSKgel ODS-100V C18 column (3 μm, 150 mm x 4.6 mm i.d.) using a gradient system of acetonitrile and water, with diode array detection (254 nm). The method was validated for linearity, precision, accuracy, limit of detection and quantification. A total of 27 Bupleurum samples were examined with this method, which showed a great variety in the distribution and contents of the polyacetylenes. It was found that polyacetylenes (1-8) were the main ingredients in B. longiradiatum, while a few kinds of polyacetylenes (5-8) were also identified in B. smithii, B. smithii var. parvifolium, B. bicaule and B. angustissimum. However, no polyacetylenes (1-9) were detected in the authentic Chaihu samples and the other Bupleurum species. The results indicated that the toxic B. longiradiatum could readily be distinguished from other medicinal Bupleurum species based on the polyacetylene profiles, and the guidelines and quality control of polyacetylenes for Chaihu are useful. The acute toxicity of the ethanol extract of B. longiradiatum and its fractions was also investigated. 相似文献