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排序方式: 共有188条查询结果,搜索用时 437 毫秒
91.
Naira Rezende Maciel Erika Cristina Vargas Oliveira Cindy Hana Okuma José Fernando Topan Lia Queiroz Amaral Pedro Rocha-Filho 《Journal of Dispersion Science and Technology》2016,37(5):646-655
Emulsions are excellent pharmaceutical vehicles used in both the pharmacy and cosmetic industries. Vegetable oils have several effects/benefits on skin and can be used in emulsions to release principal active components for cosmetic purposes. Herein, multiple W/O/W emulsions were formulated in a one-step emulsification method, and the resulting anisotropic structures were characterized by x-ray diffraction measurements. The multiple emulsions obtained were stable and maintained their anisotropic structures over 2 years. WAXS (wide-angle x-ray scattering) measurements of these emulsions suggested that the carbon chains of the surfactant around the globules are disposed in a gel network phase. Furthermore, SAXS (small-angle x-ray scattering) measurements indicated that the surfactant is organized in lamellar layers around the globules. Thus, for the first time, we demonstrated that stable lamellar gel phase multiple emulsions can be made from vegetable oils. In addition to having the advantage of being prepared in one step, these emulsions have desirable characteristics that can be used in the cosmetic industry as natural active principles with low surfactant concentration and the unique features of multiple emulsions with gel phases. 相似文献
92.
In this article we consider a spectral sequence (Er,dr) associated to a filtered Morse-Conley chain complex (C,Δ), where Δ is a connection matrix. The underlying motivation is to understand connection matrices under continuation. We show how the spectral sequence is completely determined by a family of connection matrices. This family is obtained by a sweeping algorithm for Δ over fields F as well as over Z. This algorithm constructs a sequence of similar matrices Δ0=Δ,Δ1,… , where each matrix is related to the others via a change-of-basis matrix. Each matrix Δr over F (resp., over Z) determines the vector space (resp., Z-module) Er and the differential dr. We also prove the integrality of the final matrix ΔR produced by the sweeping algorithm over Z which is quite surprising, mainly because the intermediate matrices in the process may not have this property. Several other properties of the change-of-basis matrices as well as the intermediate matrices Δr are obtained. 相似文献
93.
Maria da Graça Nascimento Sandra Patricia Zanotto Marivania Scremin Marcos Caroli Rezende 《合成通讯》2013,43(14):2715-2721
An alternative procedure for the esterification of alcohols by short-chain carboxylic acids supported on silica is presented. 相似文献
94.
The cationic halochromism of phenolate betaines was reproduced with the aid of a simple theoretical model, by calculation of the longest wavelength transition energies of supermolecules obtained by positioning a cation Mn+ at a variable distance from the oxygen atom of the dye. The theoretical results were compared with experimental data for three systems, Reichardt’s betaine 1, Brooker’s merocyanine 2 and the N-methyl-8-oxyquinolinium dye 3. The model was validated by molecular dynamics simulations of solutions of dye 3, in methanol and DMSO, in the presence of variable concentrations of Na+. 相似文献
95.
B. N. Sismanoglu K. G. Grigorov R. Caetano M. V.O. Rezende Y. D. Hoyer 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2010,60(3):505-516
This paper is dedicated to the study of the electrical and optical
characteristics of direct current microhollow cathode discharges (MHCD) in
argon flow. Experiments have been carried out in order to determine the
so-called Paschen’s curves in a static open MHCD. Current-voltage
characteristics were obtained as a function of the pressure and hole
diameter. MHCD enable stable direct current discharge operation, which could
be ignited for pressures ranging from 12 to 800 Torr, in a very wide range of
current densities and electrodes materials. Optical emission spectroscopy
and analysis of the spectral line broadening of plasma line emissions were
performed in order to measure parameters such as electron number density (2–4 × 1014 cm-3)^{-3}), gas
temperature (460–640 K), excitation
temperature (~ 7000 K) and electron temperature (~ 8500 K), for
current ranging from 7 to 15 mA. Lower gas temperature was measured compared
to the static MHCD ones. 相似文献
96.
Gabriele H. Greco Maria Pia Moschen Eliane Quelho Frota Rezende 《Annali dell'Universita di Ferrara》1998,44(1):27-39
Kaleva [9] has studied the relationships between the metric convergencesH andD of fuzzy convex sets on Euclidean spaces. The distanceH between two fuzzy set is given by Hausdorff distance of their sendographs, whileD is the supremum of the Hausdorff distances of the level sets corresponding to the fuzzy sets. The aim of this paper is to
compareH andD with the variational convergence, called γ-convergence (see De Giorgi and Franzoni [3]). Our analysis which is carried out
in the setting of metric spaces (not necessarily locally compact or vector spaces), improves Kaleva's results.
Sunto Kaleva ha investigato in [9] le relazioni esistenti tra due convergenze metriche, detteH eD, di sottoinsiemi fuzzy di spazi euclidei finito-dimensionali. In questo articolo le convergenzeH eD (la loro definizione dipende dalla distanza di Hausdorff tra insiemi compatti) sono confrontate con la convergenza variazionale, detta γ-convergenza, introdotta da De Giorgi and Franzoni in [3] nel contesto degli spazi topologici. Tale confronto con la γ-convergenza (vedi Teorema 3.7), svolto nell'ambito degli spazi metrici (non necessariamente, localmente compatti o lineari) migliora ed estende i precedenti risultati di Kaleva.相似文献
97.
98.
Pieroni LG de Rezende FM Ximenes VF Dokkedal AL 《Molecules (Basel, Switzerland)》2011,16(11):9439-9450
Miconia is one of the largest genus of the Melastomataceae, with approximately 1,000 species. Studies aiming to describe the diverse biological activities of the Miconia species have shown promising results, such as analgesic, antimicrobial and trypanocidal properties. M. albicans leaves were dried, powdered and extracted to afford chloroformic and methanolic extracts. Total phenolic contents in the methanolic extract were determined according to modified Folin-Ciocalteu method. The antioxidant activity was measured using AAPH and DPPH radical assays. Chemical analysis was performed with the n-butanol fraction of the methanolic extract and the chloroformic extract, using different chromatographic techniques (CC, HPLC). The structural elucidation of compounds was performed using 500 MHz NMR and HPLC methods. The methanolic extract showed a high level of total phenolic contents; the results with antioxidant assays showed that the methanolic extract, the n-butanolic fraction and the isolated flavonoids from M. albicans had a significant scavenging capacity against AAPH and DPPH. Quercetin, quercetin-3-O-glucoside, rutin, 3-(E)-p-coumaroyl-α-amyrin was isolated from the n-butanolic fraction and α-amyrin, epi-betulinic acid, ursolic acid, epi-ursolic acid from the chloroformic extract. The results presented in this study demonstrate that M. albicans is a promising species in the search for biologically active compounds. 相似文献
99.
Ferreira JG Reis AP Guimarães VM Falkoski DL Fialho Lda S de Rezende ST 《Applied biochemistry and biotechnology》2011,164(7):1111-1125
α-Galactosidases has the potential to hydrolyze α-1-6 linkages in raffinose family oligosaccharides (RFO). Aspergillus terreus cells cultivated on wheat bran produced three extracellular forms of α-galactosidases (E1, E2, and E3). E1 and E2 α-galactosidases
presented maximal activities at pH 5, while E3 α-galactosidase was more active at pH 5.5. The E1 and E2 enzymes showed stability
for 6 h at pH 4–7. Maximal activities were determined at 60, 55, and 50°C, for E1, E2, and E3 α-galactosidase, respectively.
E2 α-galactosidase retained 90% of its initial activity after 70 h at 50°C. The enzymes hydrolyzed ρNPGal, melibiose, raffinose
and stachyose, and E1 and E2 enzymes were able to hydrolyze guar gum and locust bean gum substrates. E1 and E3 α-galactosidases
were completely inhibited by Hg2+, Ag+, and Cu2+. The treatment of RFO present in soy milk with the enzymes showed that E1 α-galactosidase reduced the stachyose content to
zero after 12 h of reaction, while E2 promoted total hydrolysis of raffinose. The complete removal of the oligosaccharides
in soy milk could be reached by synergistic action of both enzymes 相似文献
100.
Long lasting phosphorescence in barium aluminates can be achieved by doping with rare earth ions in divalent charge states. The rare earth ions are initially in a trivalent charge state, but are reduced to a divalent charge state before being doped into the material. In this paper, the reduction of trivalent rare earth ions in the BaAl2O4 lattice is studied by computer simulation, with the energetics of the whole reduction and doping process being modelled by two methods, one based on single ion doping and one which allows dopant concentrations to be taken into account. A range of different reduction schemes are considered and the most energetically favourable schemes identified. 相似文献