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71.
Paula Gomes Maria João Araújo Eduardo F. Marques Soraia Falcão Rodrigo O. Brito 《合成通讯》2013,43(12):2025-2036
Double-chained surfactants with potential biocompatibility have been prepared in high yields by lysine acylation with four natural saturated fatty acids (C6 to C12) and with cis-undec-5-enoic acid. The surfactants were found to assemble into nanotubules in aqueous medium and, when mixed with a commercial cationic surfactant, to spontaneously form liposomes. 相似文献
72.
Tiago E. Frizon Daniel S. Rampon Hugo Gallardo Aloir A. Merlo Paulo H. Schneider Oscar E.D. Rodrigues 《Liquid crystals》2013,40(6):769-777
A simple and efficient procedure for the synthesis of a new class of organoselenium liquid crystal compounds was developed. The coupling of aryl bromides with elemental selenium was catalysed using copper oxide nanopowder in the presence of potassium hydroxide employing dimethyl sulfoxide as the solvent. This is the first report of the synthesis and characterisation of liquid crystal-based diselenides. Their mesophases were characterised by polarising optical microscopy and differential scanning calorimetry. Compounds 1, 2 and 4b exhibited the smectic A phase. In addition, these compounds showed weak blue fluorescence in solution (λmax. em. 350–405 nm) and a Stokes shift of around 90 nm. 相似文献
73.
Carlos Victor Montefusco-Pereira Maria José de Carvalho Ana Paula de Araújo Boleti Lorisa Simas Teixeira Humberto Reis Matos Emerson Silva Lima 《Applied biochemistry and biotechnology》2013,170(6):1367-1378
Diabetes mellitus is a metabolic disease characterized by abnormally high plasma glucose levels, leading to major complications, such as insulin resistance, obesity, hyperlipidemia, and hypertension, also with alterations in the immune and neuronal systems. Brazilian plants have been studied as important sources for new molecules with medicinal properties. The genus Passiflora known as “Maracujá” has been used as a traditional folk medicine for a long time, so an investigation was performed regarding an endemic kind of passion fruit (Passiflora nitida Kunth) from Amazonas, Brazil. Here, we aimed to determine its potential biological activity against metabolic syndrome, oxidative stress, pain, and inflammation. The hydroethanol leaf extract revealed an in vitro α-glucosidase inhibitory activity of 50 % inhibitory concentration (IC50)?=?6.78?±?0.31 μg/mL and an α-amylase inhibition of IC50?=?93.36?±?4.37. In vivo, experiments of different saccharide tolerance resulted in significant glycemia control and, with alloxan-diabetic mice, resulted in a decrease of total cholesterol, a hypoglycemic effect, and an antioxidant activity by thiobarbituric acid-reactive substances measurement. Also, it decreased the carrageenan-induced edema volume and the rate of writhing as a nociceptive response. These results indicate positive effects of P. nitida extract and its potential to inhibit metabolic syndrome. 相似文献
74.
Sofia Batista Emília Silva Sara Galhardo Paula Viana Maria José Cerejeira 《International journal of environmental analytical chemistry》2013,93(8-9):601-609
In two Portuguese agricultural areas, "Beira Litoral" and "Ribatejo e Oeste", several pesticides regularly applied in vineyards, maize, potato, tomato for industry, apple, pear and rice were detected in ground water. Atrazine was the most frequently detected, being found in 70% of the total of 79 sites selected in the year 2000, followed by its metabolites desethylatrazine and desisopropylatrazine with frequencies of detection, respectively, of 56% and 48% and by simazine (37%), alachlor (25%), metolachlor (24%) and metribuzin (15%). Other pesticides and metabolites i.e. 3,4-dichloroaniline, dimethoate, f and g -endosulfan, lindane, molinate and prometryn were also detected but at lower occurrences. Pesticides were detected mainly in ground water wells used for irrigation purposes, although in some locations they were also found in water wells used for human consumption. In this study, it was also observed a seasonal variation of pesticide residues in ground water of shallow and deep wells. 相似文献
75.
Máira R. Rodrigues 《Journal of carbohydrate chemistry》2013,32(7):733-744
This study reports the synthesis and characterization of hydrophobic derivatives of dextran in which long alkyl chains substituted a proportion of the hydroxyl groups. These derivatives were characterized by 13C and 1H NMR and infrared spectroscopy. Information about hydrophobic associations in aqueous solutions was obtained by fluorescence spectroscopy in the presence of pyrene and nabumetone probes. These results, in addition to the swelling‐index data of derivatives, showed that there are perspectives of using them as a starting point for models of drug delivery. 相似文献
76.
Dr. Mónica Arrate Dr. Aritz Durana Dr. Paula Lorenzo Prof. Dr. Ángel R. de Lera Prof. Dr. Rosana Álvarez Dr. José M. Aurrecoechea 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(41):13893-13900
Carbonyl‐tethered propargylic benzoates undergo intramolecular carbonylpropargylation upon treatment with Et2Zn in the presence of a catalytic amount of Pd0 with the formation of 2‐alkynylcyclopentanol products. A ligand/solvent effect on the cis/trans selectivity (referring to the relative positions of alkynyl and OH groups) of ring‐closure has been found. In a non‐coordinating solvent (benzene), increasing the electron‐donating ability of the phosphine ligand (while decreasing its dissociation ability) leads to an increased tendency towards the trans product. On the other hand, the combination of a coordinating solvent (THF) and PPh3, an easily dissociated phosphine, results in the exclusive formation of cis products. Experimental and computational results are compatible with a divergent behavior of an allenylethylpalladium intermediate that partitions between competitive carbonyl‐addition and transmetalation pathways, each leading to a different diastereoisomer. These results also suggest that the dissociating ability of the phosphine regulates that behavior. 相似文献
77.
Prof. Giuseppe Alibrandi Dr. Valeria Amendola Dr. Greta Bergamaschi Dr. Riccardo Dollenz Prof. Luigi Fabbrizzi Prof. Maurizio Licchelli Dr. Carmelo Lo Vecchio 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(11):3729-3734
The combined activity of the 1.1.1‐cryptand and of a dicopper(II) bistren cryptate complex including chloride makes the Cl? ion be continuously and slowly delivered to the solution, without any external intervention. The 1.1.1‐cryptand slowly releases OH? ions, according to a defined kinetics, and each OH? ion displaces a Cl? ion from the cryptate. Chloride displacement induces a sharp colour change from bright yellow to aquamarine and can be conveniently monitored spectrophotometrically, even in diluted solutions. The 1.1.1‐cryptand is the motor of a molecular dispenser (the dicopper(II) cryptate) delivering chloride ion automatically, from the inside of the solution. 相似文献
78.
79.
Paula?Reis Luísa?Canto e Castro Sandra?Dias M.?Ivette?GomesEmail author 《Methodology and Computing in Applied Probability》2015,17(1):189-206
In reliability theory any coherent system can be represented as either a series-parallel or a parallel-series system. Its lifetime can thus be written as the minimum of maxima or the maximum of minima. For large-scale coherent systems it is sensible to assume that the number of system components goes to infinity. Then, the possible non-degenerate extreme value laws either for maxima or for minima are eligible candidates for the system reliability or at least for the finding of adequate lower and upper bounds for the reliability. The identification of the possible limit laws for the system reliability of homogeneous series-parallel (or parallel-series) systems has already been done under different frameworks. However, it is well-known that in most situations such non-degenerate limit laws are better approximated by an adequate penultimate distribution. Dealing with regular and homogeneous parallel-series systems, we assess both theoretically and through Monte-Carlo simulations the gain in accuracy when a penultimate approximation is used instead of the ultimate one. 相似文献
80.
We consider the numerical solution of the continuous algebraic Riccati equation A*X + XA ? XFX + G = 0, with F = F*,G = G* of low rank and A large and sparse. We develop an algorithm for the low‐rank approximation of X by means of an invariant subspace iteration on a function of the associated Hamiltonian matrix. We show that the sought‐after approximation can be obtained by a low‐rank update, in the style of the well known Alternating Direction Implicit (ADI) iteration for the linear equation, from which the new method inherits many algebraic properties. Moreover, we establish new insightful matrix relations with emerging projection‐type methods, which will help increase our understanding of this latter class of solution strategies. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献