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971.
The complete 1H and 13C NMR signal assignment of four new photochromic spiro[7H-benzo[de]anthracene-naphthopyrans] was achieved using one- and two-dimensional methods (DEPT, COSY, HSQC, HMBC, NOESY). 相似文献
972.
Almeida IF Fernandes E Lima JL Costa PC Bahia MF 《Journal of photochemistry and photobiology. B, Biology》2008,91(2-3):87-95
Topical natural antioxidants are a useful strategy for the prevention of photoaging and oxidative stress mediated skin diseases. In view of this underlying principle, the screening of natural plant extracts with scavenging activity for pro-oxidant reactive species is a primary requirement for the development of new topical antioxidant formulations. In the present study, an ethanol:water (7:3) extract from Castanea sativa leaves and a ethanol:water (2:3) extract from Quercus robur leaves were evaluated for their putative in vitro scavenging effects on reactive oxygen species (ROS) namely superoxide radical (O(2)(-)), hydroxyl radical (HO()), peroxyl radical (ROO()), hydrogen peroxide (H(2)O(2)) and singlet oxygen ((1)O(2)) as well as on reactive nitrogen species (RNS) namely nitric oxide (()NO) and peroxynitrite (ONOO(-)). The extracts presented a high potency to scavenge the tested reactive species, all the IC(50)s being found at the microg/mL level. IC(50)s (mean+/-SE) for the ROS O(2)(-),HO(),H(2)O(2) and (1)O(2) were 13.6+/-1.8; 216+/-4; 410+/-8; 12.3+/-0.7 microug/mL, respectively, for C. sativa, and 11.0+/-0.5; 285+/-22; 251+/-32; 7.90+/-0.56 microg/mL, respectively, for Q. robur. The ORAC values obtained for ROO() were 1.24+/-0.13 for C. sativa and 1.09+/-0.06 for Q. robur. The IC(50)s (mean+/-SE) for ()NO and ONOO(-) were 3.10+/-0.14 and 1.49+/-0.10 microg/mL, respectively, for C. sativa and 3.13+/-0.11 and 0.95+/-0.02 microg/mL, respectively, for Q. robur. The content of total phenolics for C. sativa and Q. robur were 284+/-9 and 346+/-4 mg of gallic acid equivalents (GAE)/g of lyophilized extract respectively. The observed effects might be of relevance considering the putative interest of these extracts as topical antioxidants. 相似文献
973.
Heitor Breno Pereira Ferreira Tatiana Aparecida Fernandes de Lima Paulo Jorge Sanches Barbeira 《Electroanalysis》2008,20(4):390-395
Cathodic stripping voltammetry with a hanging mercury drop electrode was used in this study to determine chloride ions in automotive fuel ethanol. Choosing the correct stripping voltammetric technique, the correct choice of deposition potential and time provided well defined voltammetric waves with good repeatability and relatively small errors, with a determination limit of 0.13 mg L?1, for only 10 s of deposition time, with better sensitivity and repeatability than the normalized method, as well as consumed less volume of the sample, being suitable for routine analysis. 相似文献
974.
M. Fernanda P. Costa Rogério B. Francisco Ana Maria A. C. Rocha Edite M. G. P. Fernandes 《Journal of Optimization Theory and Applications》2017,174(3):875-893
This paper proposes a self-adaptive penalty function and presents a penalty-based algorithm for solving nonsmooth and nonconvex constrained optimization problems. We prove that the general constrained optimization problem is equivalent to a bound constrained problem in the sense that they have the same global solutions. The global minimizer of the penalty function subject to a set of bound constraints may be obtained by a population-based meta-heuristic. Further, a hybrid self-adaptive penalty firefly algorithm, with a local intensification search, is designed, and its convergence analysis is established. The numerical experiments and a comparison with other penalty-based approaches show the effectiveness of the new self-adaptive penalty algorithm in solving constrained global optimization problems. 相似文献
975.
Susana S. Braga Joana Marques José A. Fernandes Filipe A. Almeida Paz Mª Paula M. Marques Teresa M. Santos Artur M. S. Silva 《Chemical Papers》2017,71(7):1235-1248
The complex [([9]aneS3)RuII(dipa)Cl]Cl (1, where dipa = 2,2′-dipyridylamine) was included into native β-cyclodextrin (β-CD) and permethylated β-CD (TRIMEB) by co-dissolution followed by solvent removal. Two adducts were obtained with a 1:1 host:guest stoichiometry. Solid-state studies of the guest comprised collecting the single-crystal structure of its 3.5 hydrate form and also powder diffraction on the remaining bulk material, showing it is isotypical with the harvested crystal for X-ray analysis. Solid-state studies of the cyclodextrin adducts were carried out by powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), 13C{1H} CP/MAS NMR and FTIR spectroscopies. Biological studies on 1 and its adducts comprised the evaluation of the shift caused by 1 on the melting temperature of DNA (ΔT m), as well as the evaluation of cytotoxicity by the MTT assay on the osteosarcoma MG-63 cell line. 相似文献
976.
Calligonum polygonoides Linnaeus Extract: HPLC‐EC and Total Antioxidant Capacity Evaluation
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Sara M. C. Gomes Isabel P. G. Fernandes Narpat Singh Shekhawat Sunita Kumbhat Ana Maria Oliveira‐Brett 《Electroanalysis》2015,27(2):293-301
Flavonoids in Calligonum polygonoides Linnaeus extract were separated, detected, and identified by reverse‐phase high‐performance liquid chromatography (RP‐HPLC) with electrochemical detection (EC) in combined isocratic and gradient elution using a glassy carbon or a boron doped diamond electrode. Ultrasonication coupled with a microwave‐assisted technique was developed to optimize the extraction of the phenolic compounds. The total antioxidant capacity was quantified using the DPPH. method and voltammetry. The RP‐HPLC‐EC led to the detection of nine different flavonoids: catechin, delphinidin, fisetin, myricetin, epicatechin, kuromanin, rutin, callistephin and procyanidin A2, in a single run by direct injection of the sample extract solution. 相似文献
977.
The problem concerning the propagation of free waves in binary mixtures of monatomic ideal gases is analyzed by using a kinetic model of the Boltzmann equation which is compatible with the two-fluid hydrodynamic theory. Comparison of the theoretical results with available experimental data shows that the two-fluid model equation can be used to describe the wave-vector dependence of the free sound waves in both continuum and kinetic regimes. 相似文献
978.
Amâncio Fernandes 《Comptes Rendus Mecanique》2003,331(5):337-342
A new approach based on a mixed formulation is proposed. The main advantage of such a formulation is that the transverse shear stress continuity is automatically satisfied in a natural way. In order to validate the model, comparisons of the proposed theory to Pagano's exact elasticity solutions are made for a bi-layer and a sandwich plate. To cite this article: A. Fernandes, C. R. Mecanique 331 (2003). 相似文献
979.
980.
Octakis(3-chloropropyl)octasilsesquioxane (S) was organofunctionalized with the PAMAM Dendrimer G.0 (SPD). After functionalization, silsesquioxane interacts with copper chloride and subsequently with potassium hexacyanoferrate (III) to produce the structure CuHSPD. The silsesquioxane functionalized with the PAMAM dendrimer (SPD) and the obtained novel hybrid composite (CuHSPD) were characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS). The CuHSP voltammogram showed two well-defined redox pairs with Eθ′= 0.27 and 0.74 V, that are assigned to the CuI/CuII and FeII(CN)6/FeIII(CN)6 redox pairs, respectively. The graphite paste electrode containing CuHSPD allowed the electrocatalytic determination of ascorbic acid using various electrochemical techniques such as cyclic voltammetry, differential pulse voltammetry, and chronoamperometry. 相似文献