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排序方式: 共有198条查询结果,搜索用时 15 毫秒
51.
Núñez-Vergara LJ Farias D Bollo S Squella JA 《Bioelectrochemistry (Amsterdam, Netherlands)》2001,53(1):103-110
This paper reports the feasibility of free radicals formation from flutamide by using cyclic voltammetry. The electrochemical characteristics and the reactivity of the one-electron reduction product from flutamide in mixed media with thiol compounds and the nuclei acid bases are characterized. Results from this paper show the thermodynamic feasibility of free radical formation expressed for both the cathodic peak potential and the second-order rate constant values. The reactivity of the radical towards thiol compounds (glutathione, cysteamine, N-acetylcysteine) and the nuclei acid base, adenine, thymine and uracil were quantitatively assessed through the calculation of the respective interaction rate constants. Based on these results, the following tentative order of reactivity towards the xeno/endobiotics is as follows: cysteamine > uracil > glutathione > adenine > N-acetylcysteine > thymine. The stability of the nitro radical anion electrochemically generated from flutamide showed a linear dependence with pH. 相似文献
52.
53.
We give a special ordered set (SOS) approach that optimizes a discontinuous separable piecewise linear function, even when a mixed-integer programming (MIP) model is not available for it. When a MIP model is available, our SOS model gives a linear programming relaxation bound that is as good as the MIPs. 相似文献
54.
Summary The adsorptive stripping voltammetric behaviour of Arsenazo III, Eriochrome Black T, 4-(2-pyridylazo) resorcinol, Mordante Blue 9 and their uranyl complexes has been investigated in detail. All compounds and complexes adsorb on the static mercury drop electrode. Results are presented and the limitations of the methods are discussed. 相似文献
55.
Voltammetric determination of copper and lead in gasoline using sample preparation as microemulsions. 总被引:1,自引:0,他引:1
Carlos E Cardoso Wagner F Pacheco Rangel Sarubi Márcio L N Ribeiro Pércio A M Farias Ricardo Q Aucélio 《Analytical sciences》2007,23(9):1065-1069
A voltammetric method for the determination of Cu(II) and Pb(II) in gasoline using sample preparation as three-component solutions (gasoline:propan-1-ol:water, 25:60:15 v/v/v) is proposed. HNO(3) was employed as a supporting electrolyte and to allow the use of aqueous inorganic standards for calibration, even if the analyte species originally in gasoline is present as a metallo-organic form. A square-wave anodic sequential determination was used by measuring the stripping current of Cu(II) (at +104 mV) using a glassy carbon electrode (GCE) and, in a second run, measuring the Pb(II) stripping current (at -470 mV) using a bismuth-film deposited on the surface of the GCE. The method allowed the quantification of 1.7 x 10(-9) mol L(-1) of Cu and 1.4 x 10(-10) mol L(-1) of Pb employing a 1500-s accumulation time. Recovery tests using analyte spiked three-component solutions prepared with commercial gasoline samples enabled recoveries of Cu and Pb from 97 +/- 8 to 102 +/- 5%. 相似文献
56.
Bruno Fonsêca Feitosa Charlene Maria de Alcntara Amanda Beatriz Sales de Lima Adriano SantAna Silva Alfredina dos Santos Araújo Mnica Tejo Cavalcanti Edna Mori Isaac Moura Araújo Pablo Antonio Maia de Farias Polrat Wilairatana Henrique Douglas Melo Coutinho 《Molecules (Basel, Switzerland)》2022,27(18)
The inappropriate use of synthetic antibiotics has become a global public health problem. Therefore, the study of new alternatives for the treatment of infectious diseases is relevant and natural bioactive products are on the rise. This study conducted a scientific prospection of bioactive natural products with promising applications in the chemical control of microorganisms. A systematic review of the most recent articles was performed according to the following three steps: (i) eligibility assessment, (ii) screening, and (iii) inclusion of articles and information extraction. There has been an increase in the number of scientific publications on bioactive natural products for microbial control in the CAPES and SciELO databases (2001–2021). Seventeen relevant articles were included, most of which focused on extracts. Ascorbic acid, chlorogenic acid, chrysin, and quercetin were the most cited compounds. Natural products were shown to be effective in inhibiting more than 30 microorganisms. A discussion was presented on the research trends. 相似文献
57.
I. Lima M.L.F. Farias N. Percegoni D. Rosenthal J.T. de Assis M.J. Anjos R.T. Lopes 《Spectrochimica Acta Part B: Atomic Spectroscopy》2010
Characterization of trabeculae structures is one of the most important applications of imaging techniques in the biomedical area. The aim of this study was to investigate structure modifications in trabecular and cortical bones using non destructive techniques such as X-ray microtomography, X-ray microfluorescence by synchrotron radiation and scanning electron microscopy. The results obtained reveal the potential of this computational technique to verify the capability of characterization of internal bone structures. 相似文献
58.
Tiago C. Adorno Alexander I. Breev Antonio J. D. Farias Jr. Dmitri M. Gitman 《Annalen der Physik》2023,535(7):2300118
The problem of the electromagnetic radiation produced by charge distributions in the framework of a semiclassical approach proposed in the work by Bagrov, Gitman, Shishmarev, and Farias Jr. [J. Synchrotron Rad. 27 , 902–911 (2020)] is addressed here. In this approach, currents, generating the radiation are considered classically, while the quantum nature of the radiation is kept exactly. Quantum states of the electromagnetic field are solutions of Schrödinger's equation, and relevant quantities to the problem are evaluated with the aid of transition probabilities. This construction allows us to introduce the quantum transition time in physical quantities and assess its role in radiation problems by classical currents. Radiated electromagnetic energies are studied in detail and a definition for the rate at which radiation is emitted from sources is presented. In calculating the total energy and rate radiated by a pointlike charged particle accelerated by a constant and uniform electric field, it is discovered that these results are compatible with results obtained by other authors in the framework of the classical radiation theory under an appropriate limit. Numerical and asymptotic analyses of the results are also performed. 相似文献
59.
Gaiao Eda N Martins VL Lyra Wda S de Almeida LF da Silva EC Araújo MC 《Analytica chimica acta》2006,570(2):283-290
The exploitation of digital images obtained from a CCD camera (WebCam) as a novel instrumental detection technique for titration is proposed for the first time. Named of digital image-based (DIB) titration, it also requires, as a traditional titration (for example, spectrophotometric, potentiometric, conductimetric), a discontinuity in titration curves where there is an end point, which is associated to the chemical equivalence condition. The monitored signal in the DIB titration is a RGB-based value that is calculated, for each digital image, by using a proposed procedure based on the red, green, and blue colour system. The DIB titration was applied to determine HCl and H3PO4 in aqueous solutions and total alkalinity in mineral and tap waters. Its results were compared to the spectrophotometric (SPEC) titration and, by applying the paired t-test, no statistic difference between the results of both methods was verified at the 95% confidence level. Identical standard deviations were obtained by both titrations in the determinations of HCl and H3PO4, with a slightly better precision for DIB titration in the determinations of total alkalinity. The DIB titration shows to be an efficient and promising tool for quantitative chemical analysis and, as it employs an inexpensive device (WebCam) as analytical detector, it offers an economically viable alternative to titrations that need instrumental detection. 相似文献
60.