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91.
Dorina Mitrea 《Mathematical Methods in the Applied Sciences》2004,27(17):2067-2080
This paper is concerned with the solvability of the hyperbolic Maxwell system in Lipschitz cylinders via integral methods. By means of the Laplace transform, the original hyperbolic Maxwell system is reduced to a family of stationary Maxwell equations indexed by ω, the Laplace variable. The crux of the matter is establishing how all relevant constants in the main estimates for this family of Maxwell equations depend on ω. Among other things, appropriate norms and weighted Sobolev spaces are considered so that the integral equation method works. The solution is expressed in terms of retarded potentials. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
92.
Comprehensive evaluation of biogenic amines and related drugs’ antiradical activity using reactive 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical 总被引:1,自引:0,他引:1
A comprehensive study of biogenic amines and related drugs as free radical scavengers and potential antioxidants was carried out using the stable free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH·). The results of the effect of test duration and the relative concentration on the ability of the compounds to scavenge the DPPH· were investigated and discussed. The antiradical activity of amines was compared with the activity of some reference antioxidants (phenols, phenolic acids, flavonols and other antioxidants). Some particular insights related to the mechanism of reactivity toward the DPPH· were investigated by carrying out kinetic studies in methanol for different relative concentrations. According to the obtained results, catecholamines and especially their related drugs (D-dopa, adrenalone, S-(?)-carbidopa and isoprenaline) showed a fast reactivity towards DPPH· and the highest antiradical activity which increased in a concentration-dependent manner. Moreover, catecholamines proved to be more powerful scavengers than ascorbic and caffeic acids even at low concentrations while their related drugs (D-dopa, adrenalone and S-(?)-carbidopa) showed higher antiradical activity than gallic acid for all of the investigated concentrations. 相似文献
93.
Fana‐Maria Coman Denisa Leonte Alexandra Toma Dorina Casoni Laurian Vlase Valentin Zaharia 《Journal of separation science》2020,43(14):2784-2793
Reversed‐phase thin‐layer chromatography and reversed‐phase high‐performance liquid chromatography were used for lipophilicity determination of a library of 30 thiazole chalcones and aurones previously synthetized in our laboratory. The experimental lipophilicity data have been compared with theoretical lipophilicity parameters estimated by various computational methods. Good correlations between the experimental and calculated lipophilicity parameters have been found for both investigated classes of compounds. Correlations between the lipophilicity of the thiazole chalcones and aurones and their antiproliferative activity were discussed. The methodologies and data gathered in this study will contribute to the lipophilicity studies of chalcones and aurones derivatives, two important classes of compounds in medicinal chemistry. 相似文献
94.
Dorina Bodi Christiane Ringling Caroline Schödel Angelika Preiß-Weigert Hildburg Fry 《Chromatographia》2013,76(11-12):651-662
A comprehensive survey of matrix effects on the LC–MS/MS analysis of the banned antibiotic growth promoters carbadox and olaquindox in feed was carried out. Various factors of sample preparation procedure and measurement were systematically investigated by pre- and post-extraction addition and postcolumn infusion experiments. In general, strong signal suppression up to 70 % for carbadox and up to 90 % for olaquindox was observed when using different extraction solvents and techniques as well as different chromatographic conditions. Reduction of matrix effects was achieved by SPE clean-up and dilution of sample extracts. Nevertheless, matrix effect profiles determined by postcolumn infusion revealed, that reduction of signal suppression at a respective retention time cannot guarantee improvement of the methods performance. If high variability of matrix effects is present along the chromatographic run, accuracy might decrease despite reduced signal suppression. Besides method parameters, different feedingstuffs were investigated and showed similar matrix effects. 相似文献
95.
Thin‐layer chromatography—an image‐processing method for the determination of acidic catecholamine metabolites
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A sensitive and convenient method for acidic catecholamine metabolites (including homovanillic acid, vanillylmandelic acid, 3,4‐dihydroxymandelic acid, and 3,4‐dihydroxyphenylacetic acid) determination was developed based on thin‐layer chromatography and image‐processing analysis. The metabolites were separated without a prederivatization step using reversed phase RP‐18W high‐performance plates. The mobile phase composition, detection, and quantification conditions were systematically investigated through several trials. The reaction with 2,2‐diphenyl‐1‐picrylhydrazyl radical allowed specific detection of acidic catecholamine metabolites with a high sensitivity and a wide linear range. The limit of detection and the limit of quantification were in the range of 13–103 and 18–120 ng/spot, respectively, in all cases. Mean recoveries determined were in the range 95–106% for all of the investigated compounds. The proposed method allowed rapid simultaneous determination of acidic catecholamine metabolites from spiked human urine sample. 相似文献
96.
97.
The chromatographic behaviour of the parabens has been investigated on RP‐18F254S, RP‐18WF254S, CNF254S, Diol F254s and silica gel 60F254 plates impregnated with different oils (paraffin, olive, sunflower and corn) using methanol–water mixtures in different volume proportions as mobile phases, the regression determination coefficients being excellent (higher than 0.98 for the majority of compounds). Moreover, highly significant correlations were obtained between different experimental indices of lipophilicity (RM0, b and scores corresponding to the first principal component (PC1)) and computed log P values. All types of stationary phases investigated appear to be highly suited for estimating the lipophilicity of the parabens. 相似文献
98.
In this paper, the authors present their results regarding the cellular division rate and the percentage of chromosomal aberrations in the root meristematic cells of agricultural plants when cultivated in the presence of different concentrations of aqueous ferrofluid, ranging between 10 and 250 μL/L. The agricultural species (Zea mays) with a major role in the life of people was chosen for the experimental project. The water-based ferrofluid was prepared following the chemical co-precipitation method, using tetramethylammonium hydroxide as magnetite core stabilizer. Microscopic investigations (cytogenetic tests) resulted in the evaluation of the mitotic and chromosomal aberration index. They appeared to increase following ferrofluid addition. 相似文献
99.
Alessandro D'Aprano Ines Dorina Donato Vincenzo Turco Liveri 《Journal of solution chemistry》1990,19(7):711-720
Densities and viscosities of n-pentanol +n-octane mixtures in the temperature range 0 to 45°C are reported. The data are discussed in terms of molar excess volumes, molar excess fluidities and molar excess activation energies of viscous flow in order to obtain structural information of the mixtures. It is shown that the structural modifications of n-pentanol and n-octane upon mixing, significantly contribute to the parameters governing the viscous flow and the volume of the mixtures. 相似文献
100.
We consider two basic potential theoretic problems in Riemannian manifolds: Hodge decompositions and Maxwell's equations. Here we are concerned with smoothness and integrability assumptions. In the context of Lp forms in Lipschitz domains, we show that both are well posed provided that 2−<p<2+, for some >0, depending on the domain. Our approach is constructive (in the sense that we produce integral representation formulas for the solutions) and emphasizes the intimate connections between the two problems at hand. Applications to other related PDEs, such as boundary problems for the Hodge Dirac operator, are also presented. 相似文献