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排序方式: 共有102条查询结果,搜索用时 15 毫秒
81.
82.
Julio Hervé Andriamadio Léa Herilala Rasoanaivo Daniela Benedec Ana-Maria Gheldiu Mihaela Duma 《Natural product research》2015,29(23):2188-2196
The purpose of this work was to evaluate chemical constituents, antioxidant and antimicrobial activities of Artabotrys hildebrandtii, an endemic medicinal plant from Madagascar. Ethanol extracts from the leaves and stem bark were tested to evaluate DPPH free radical scavenging, using butylated hydroxytoluene and quercetin as standard antioxidants. An high-performance liquid chromatography/mass spectrometry method was developed to investigate the presence of phenolic compounds in the studied samples; gentisic acid, chlorogenic acid, hyperoside, isoquercitrin, rutin, quercitrin, quercetol, apigenin and luteolin were identified. Total polyphenolic content was determined by a spectrophotometric method using Folin–Ciocâlteu reagent. Results showed the efficiency of A. hildebrandtii leaves extract against strains of Staphylococcus aureus and Listeria monocytogenes, as the inhibitory activity is more powerful compared to Gentamicin, used as the standard drug. The leaves of A. hildebrandtii can be considered an important source of polyphenols, especially of rutin, with good antioxidant and antimicrobial activities. 相似文献
83.
84.
Ana-Maria Matei 《Comptes Rendus Mathematique》2002,335(3):255-258
Let be a domain with Lipschitzian boundary of a compact Riemannian manifold (M,g) and p>1. We prove that we can make the volume of M arbitrarily close to the volume of while the first eigenvalue of the p-Laplacian on M remains uniformly bounded from below in terms of the the first eigenvalue of the Neumann problem for the p-Laplacian on . To cite this article: A.-M. Matei, C. R. Acad. Sci. Paris, Ser. I 335 (2002) 255–258. 相似文献
85.
IR spectra of adsorbed CO species after prolonged contact with the catalyst surface show that surface carbon is formed and it participates in methane synthesis.
- , CO , , .相似文献
86.
The analysis of conductive solid samples by r.f. capacitively coupled plasma at atmospheric pressure
Sorin D. Anghel Tiberiu Frentiu Ana-Maria Rusu Lucia Bese E. A. Cordos 《Fresenius' Journal of Analytical Chemistry》1996,355(3-4):252-253
A radiofrequency capacitively coupled plasma (rf CCP) with tip-ring electrode geometry has been used for the analysis of Al, Co, Cr, Cu, Mn, Mo, Ni, and V in low and medium alloyed steel. The sample is used as one of the electrodes of the plasma torch. The influence of plasma power, argon flow rate and distance between the electrodes on the analytical signals has been studied. The limits of detection are in the range of 0.001 to 0.048%. The dynamic range is three orders of magnitude. 相似文献
87.
Anghel SD Frentiu T Darvasi E Rusu AM Simon A Cordos EA 《Analytical and bioanalytical chemistry》1996,355(3-4):250-251
The excitation temperatures of Ar and Fe, the ionization temperatures of Ar and Ca and the electron number densities have been determined for a radiofrequency capacitively coupled plasma in the tip-ring electrode geometry. The temperatures and the electron number densities possess their maximum value close to the electrodes. 相似文献
88.
Ana-Maria Castravet 《Proceedings of the American Mathematical Society》2007,135(12):3783-3788
A conjecture of Pukhlikov states that a smooth Fano variety of dimension at least 4 and index one is birationally rigid. We show that a general member of the linear system given by the ample generator of the Picard group of the moduli space of stable, rank 2 bundles with fixed determinant of odd degree on a curve of genus at least 3 is not birationally rigid.
89.
POPESCU Ana-Maria 《高等学校化学研究》2014,30(5):800-805
This study deals with SnO2-based ceramic anodes doped with Sb2O3 and CuO, aiming at contributing new data regarding their electrochemical behavior in cryolite melts. The performances of the anodes were evaluated by anodic polarization, cyclic voltammetry, and current efficiency and corrosion measurements. The investigation proves that the anodic process of SnO2-based inert anodes occurs at a low overvoltage and the oxygen discharge takes place in one step with an exchange of two electrons. The current efficiency and corrosion were proved to be dependent on the electrolysis parameters and composition of electrolysis bath. For a long term electrolysis, the dissolution of the anode in the cryolite-alumina melt produced small aluminium contamination(ca. 0.2%, mass fraction). 相似文献
90.
The authors prepared,characterized and preliminary studied the properties of some neoteric solvents-ionic liquids based on choline chloride,i.e.,three ionic liquids based on the eutectics of choline chloride(2-hydroxyN,N,N-trimethylethanaminium chloride) with,respectively,urea,malonic acid and citric acid.The obtained mixtures were clear and colorless ionic liquids at room temperature.The thermophysical properties,namely,density,viscosity,and electrical conductivity of these mixtures were investigated as a function of temperature within a range of 298-353 K.Correlations for the temperature dependence of the measured properties were generated and discussed in terms of Arrhenius theory.Finally the electrochemical windows of the eutectic liquids were determined. 相似文献