排序方式: 共有21条查询结果,搜索用时 15 毫秒
1.
Shaza M. Al-Massarani Ali A. El-Gamal Adnan J. Al-Rehaily Ebtesam S. Al-Sheddi Mai M. Al-Oqail Nida N. Farshori Alden S. Estep Nurhayat Tabanca James J. Becnel 《Molecules (Basel, Switzerland)》2021,26(4)
Chromatographic purification of the alcoholic extract from the aerial parts of the Saudi plant Nuxia oppositifolia (Hochst.), Benth., resulted in five isolated phenolic compounds. Two flavones, hispidulin (1) and jaceosidin (2), and the phenylethanoid glycosides, verbascoside (3), isoverbascoside (4), and conandroside (5), were identified and their chemical structures were determined by spectroscopic analyses. The insecticidal activity of compounds 1 and 2, in addition to 11 compounds isolated in a previous research (6–16), was evaluated against the Yellow Fever mosquito, Aedes aegypti. Four compounds displayed adulticidal activity with LD50 values of 2–2.3 μg/mosquito. Free radical scavenging properties of the plant extracts and compounds (1–5) were evaluated by measuring the 1,1-diphenyl-2-picrylhydrazyl radical (DPPH) and 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonate radical cation (ABTS•+) scavenging activity. All compounds exhibited notable activity, compared with the positive control, l-Ascorbic acid. This study suggests that N. oppositifolia could be a promising source of secondary metabolites, some with lethal adulticidal effect against Ae. aegypti. 相似文献
2.
We study the dynamical behavior of the discontinuous Galerkin finite element method for initial value problems in ordinary differential equations. We make two different assumptions which guarantee that the continuous problem defines a dissipative dynamical system. We show that, under certain conditions, the discontinuous Galerkin approximation also defines a dissipative dynamical system and we study the approximation properties of the associated discrete dynamical system. We also study the behavior of difference schemes obtained by applying a quadrature formula to the integrals defining the discontinuous Galerkin approximation and construct two kinds of discrete finite element approximations that share the dissipativity properties of the original method.
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In this article we consider the problem of computing the dominant eigenvalue of the linearization of a nonlinear operator. We define a power method that converges under natural conditions on the nonlinear operator. This nonlinear power method does not require the linearization itself, but only the action of the nonlinear operator on arbitrary functions. We apply this method to investigate the stability of equilibrium solutions of differential equations. 相似文献
4.
R. J. Estep C. W. McCluskey B. A. Sapp 《Journal of Radioanalytical and Nuclear Chemistry》2008,276(3):737-741
In this report we describe the multiple isotope material basis set (MIMBS) method for isotope identification and show that
it can overcome limitations of ordinary response function fitting and the single isotope material basis set method (SIMBS)
when applied to ideal simulated NaI spectra, for an example attenuator and isotope library. Our simulations demonstrate that
ordinary response function fitting has difficult identifying isotopes when attenuation is a factor, and that the SIMBS method
can fail when multiple isotopes are present, so the more computationally intensive MIMBS method may be required for these
situations. Its effectiveness in analyzing more realistic spectra remains to be demonstrated. 相似文献
5.
We develop a reliable efficient method for computing solutions to the Poisson equation a with randomly perturbed coefficient. We assume the perturbation to be piecewise constant and use a non-overlapping domain decomposition algorithm, where the domains coincides with regions where the perturbation is constant, to solve the equations. On each sub-domain we use an truncated Neumann series to approximate the inverse of the local stiffness matrix. By doing so we can solve for all samples simultaneously in a very efficient way. We derive a posteriori error estimates and construct an adaptive algorithm to tune the method parameters automatically. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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Numerical Algorithms - 相似文献
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8.
Digby D. Macdonald M. E. Estep M. D. Smith J. B. Hyne 《Journal of solution chemistry》1974,3(9):713-725
The influence of N,N-dimethylformamide, N,N-dimethylacetamide, 2-pyrrolidinone, N-methyl-2-pyrrolidinone, and N-t-butyl-2-pyrrolidinone on the temperature of maximum density (TMD) of water has been investigated. Heats of solution for these compounds and for diethylsulfoxide, tetramethylene sulfoxide, tetramethylene sulfone, dimethyl sulfoxide, and tetrahydrofuran in water at 23°C are also reported. These data, together with published TMD and heat of solution data for other solutes, are used to examine the relationship between the enthalpy change on dissolution of a solute in water and the effect of the dissolved substance on the structure of water as reflected by changes in the temperature of maximum density of the system. 相似文献
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We analyze a multiscale operator decomposition finite element method for a conjugate heat transfer problem consisting of a fluid and a solid coupled through a common boundary. We derive accurate a posteriori error estimates that account for all sources of error, and in particular the transfer of error between fluid and solid domains. We use these estimates to guide adaptive mesh refinement. In addition, we provide compelling numerical evidence that the order of convergence of the operator decomposition method is limited by the accuracy of the transferred gradient information, and adapt a so-called boundary flux recovery method developed for elliptic problems in order to regain the optimal order of accuracy in an efficient manner. In an appendix, we provide an argument that explains the numerical results provided sufficient smoothness is assumed. 相似文献