The main aim of this paper is to discuss the almost surely asymptotic stability of the neutral stochastic differential delay equations (NSDDEs) with Markovian switching. Linear NSDDEs with Markovian switching and nonlinear examples will be discussed to illustrate the theory. 相似文献
Triptolide (TP), one of the main bioactive diterpenes of the herbal medicine Tripterygium wilfordii Hook F, is used for the treatment of autoimmune diseases in the clinic and is accompanied by severe hepatotoxicity. CYP3A4 has been reported to be responsible for TP metabolism, but the mechanism remains unclear. The present study applied a UPLC–QTOF–MS-based metabolomics analysis to characterize the effect of CYP3A4 on TP-induced hepatotoxicity. The metabolites carnitines, lysophosphatidylcholines (LPCs) and a serious of amino acids were found to be closely related to liver damage indexes in TP-treated female mice. Metabolomics analysis further revealed that the CYP3A4 inducer dexamethasone improved the level of LPCs and amino acids, and defended against oxidative stress. On the contrary, pretreatment with the CYP3A4 inhibitor ketoconazole increased liver damage with most metabolites being markedly altered, especially carnitines. Among these metabolites, except for LPC18:2, LPC20:1 and arginine, dexamethasone and ketoconazole both affected oxidative stress induced by TP. The current study provides new mechanistic insights into the metabolic alterations, leading to understanding of the role of CYP3A4 in hepatotoxicity induced by TP. 相似文献
A reliable and affordable QuEChERS (quick, easy, cheap, effective, rugged, and safe) methodology in combination with ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC–MS/MS) was successfully developed and validated for the determination of eight bisphenols (BPs) residues containing in meats (chicken, duck, beef, pork, fish, shrimp, and mutton). A novel QuEChERS method optimization was carried out in terms of process efficiency (PE), matrix effect (ME), and extraction recovery (RE). After a simple vortex extraction of the samples with acetonitrile, 1 g sodium acetate was used for salting out (NaAC), and 100 mg primary secondary amine (PSA) purifying reagents were used for purification. The properties of the sorbents were assessed by the obtained parameters, such as matrix effect (ME), linearity, sensitivity, accuracy, and precision. Under the optimal conditions, BPs were well separated on an ACQUITY UPLC BEH ® C18 column in 8 min by gradient elution, and exhibited a good linear relationship (R2?>?0.9988) in the linear range. Moreover, the limits of detection (LODs) and the limits of quantification (LOQs) were located in the range of 0.01– 0.11 μg/kg and 0.03 – 0.37 μg/kg, respectively. The developed method was satisfactory in terms of accuracy (relative recoveries: 76.1% – 113.7%) and precision (relative standard deviations below 10.3%). Finally, the developed method was successfully employed to identify and quantify BPs residues in 28 real meat samples. The proposed QuEChERS-UPLC–MS/MS method is simple, high efficiency, cost-effective, practical, and susceptible to being implemented in routine laboratories to quickly detect the BPs in meats (chicken, duck, beef, pork, fish, shrimp, and mutton). In this sense, the method is useful for obtaining BPs residue data to evaluate the contamination status of BPs in meat food and provide scientific support for scientific supervision.
The antioxidant activities of the petroleum ether, ethyl acetate, n-BuOH and water extract fractions from Dracaena cambodiana Pierre ex Gagnep were evaluated in this study. The ethyl acetate fraction contained the highest amount of total phenolics and total flavonoids, and showed the greatest DPPH˙, ABTS+ and Superoxide anion radical-scavenging capacities. The DPPH˙, ABTS+ and Superoxide anion radical-scavenging capacities of nine compounds isolated from the ethyl acetate fraction were also evaluated. The results indicated that these compounds contributed to the antioxidant activity of D. cambodiana. Therefore, D. cambodiana and these compounds might be used as natural antioxidants. 相似文献
Using techniques based on the continuous and discrete semimartingale convergence theorems, this paper investigates if numerical
methods may reproduce the almost sure exponential stability of the exact solutions to stochastic delay differential equations
(SDDEs). The important feature of this technique is that it enables us to study the almost sure exponential stability of numerical
solutions of SDDEs directly. This is significantly different from most traditional methods by which the almost sure exponential
stability is derived from the moment stability by the Chebyshev inequality and the Borel–Cantelli lemma. 相似文献
The asymptotic properties of the numbers of spanning trees and Eulerian trails in circulant digraphs and graphs are studied.
Let
be a directed circulant graph. Let
and
be the numbers of spanning trees and of Eulerian trails, respectively. Then
Furthermore, their line digraph and iterations are dealt with and similar results are obtained for undirected circulant graphs.
Project partially supported by the National Natural Science Foundation of China (Grant No. 69673042) and by Hong Kong CERG
(HKUST652/95E). 相似文献
Positive results are derived concerning the long time dynamics of fixed step size numerical simulations of stochastic differential
equation systems with Markovian switching. Euler–Maruyama and implicit theta-method discretisations are shown to capture exponential
mean-square stability for all sufficiently small time-steps under appropriate conditions. Moreover, the decay rate, as measured
by the second moment Lyapunov exponent, can be reproduced arbitrarily accurately. New finite-time convergence results are
derived as an intermediate step in this analysis. We also show, however, that the mean-square A-stability of the theta method
does not carry through to this switching scenario. The proof techniques are quite general and hence have the potential to
be applied to other numerical methods. 相似文献