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排序方式: 共有246条查询结果,搜索用时 11 毫秒
241.
Leandro M. de Carvalho Carine Viana Ana Paula L. Moreira Paulo C. do Nascimento Denise Bohrer Monique J. Motta Géssica D. da Silveira 《Journal of Solid State Electrochemistry》2013,17(6):1601-1608
Herein, we present a new method based on separation by ion-pair chromatography with pulsed amperometric detection for evaluating various diuretics, including hydrochlorothiazide, chlorthalidone, furosemide, and amiloride, which are adulterants in herbal-based pharmaceutical formulations. The amperometric detection cycle (time?=?2 s) was performed at a gold electrode by applying a detection potential (E1) of +800 mV for 0.4 s and an oxidation potential (E2) of +1,000 mV for 0.40 s, followed by a reduction potential (E3) of ?200 mV for 1.20 s. The mobile phase for separating the diuretics was composed of 5 mmol L?1 phosphate buffer and 0.3 mmol L?1 sodium dodecyl sulfate in 50 % (v/v) methanol (pH 4.5). This method enabled the quantification of the drugs at low concentrations (i.e., 0.08 mg/capsule for hydrochlorothiazide, 0.01 mg/capsule for chlorthalidone, and 0.007 mg/capsule for furosemide). Twenty-six herbal formulations were analyzed, and eight samples (30.8 %) were found to contain diuretics that were added to the final composition (declared or not). 相似文献
242.
Cristiane Y. KawasokoCarlos E.D. Nazario Amanda S. SantanaLuiz H. Viana Gabriela R. HurtadoFrancisco A. Marques Gustavo FrenschPaulo R. de Oliveira Palimécio G. Guerrero Jr.Diego B. Carvalho Adriano C.M. Baroni 《Tetrahedron letters》2011,52(46):6067-6071
The hydroalumination of silylacetylenes with DIBAL-H followed by the addition of n-butyllithium generated in situ the (Z)-β-vinylorganosilane alanates intermediates, which were trapped with butyltellurenyl bromide (C4H9TeBr), furnishing exclusively the (E)-1-butyltelluro-1-tri(organyl)silyl-2-organyl-1-alkenes in 45-70% yields. These telluro(silyl)ketene acetals were utilized as substrates in Sonogashira cross-coupling Pd-catalyzed reactions, furnishing the (Z)-1,4-diorganyl-2-tri(organyl)silyl-1-buten-3-ynes with total control of regio- and stereochemistry in 62-80% yield. 相似文献
243.
Bartolomeu C. Viana Odair P. Ferreira Antonio G. Souza Filho Angel A. Hidalgo Josue Mendes Filho Oswaldo L. Alves 《Journal of nanoparticle research》2011,13(8):3259-3265
Titanate nanorods, nanoribbons, and nanofibers synthesized by hydrothermal treatment are being investigated by several groups.
Similar to titanate nanotubes, with average diameter of 9 nm, there is a strong controversy regarding the composition and
microscopic formation mechanism of these non-hollow nanostructures (nanoribbons). In this article, we report the synthesis
and characterization of the titanate nanostructures by exploiting some aspects that were not exploited so far. By using X-ray
diffraction, FT-infrared and Raman spectroscopies and electron microscopy, we have studied the intermediate structure and
morphology between nanotubes and the non-hollow nanostructures. Our findings give further evidence that the transformation
of nanotubes into non-hollow nanostructures is induced by a sequence of both oriented attachment and Ostwald rippening cooperative
mechanisms. 相似文献
244.
A. Lecointre A. Bessière B. Viana R. A?t Benhamou D. Gourier 《Radiation measurements》2010,45(3-6):273-276
The series of whitlockite compounds Ca3(PO4)2 and Ca9Ln(PO4)7 (Ln = Pr, Eu, Tb, Dy, Ho, Er, Lu) was studied in radioluminescence (RL) and thermally stimulated luminescence (TSL) excited by X-rays. f-f emission lines of Ln3+ were observed in RL for Ca9Ln(PO4)7 (Ln = Pr, Eu, Tb, Dy, Ho, Er) whereas d-d emission band of the impurity Mn2+ was observed in Mn:Ca3(PO4)2 and Mn:Ca9Lu(PO4)7 at 655 nm. In TSL, the Eu, Ho and Er compounds did not show any signal. As Eu3+, Ho3+ and Er3+ present the highest Ln3+/Ln4+ ionization potential (IP) of the series, this was interpreted as the inability of these lanthanides to trap a hole. On the contrary Pr3+ in Ca9Pr(PO4)7, Tb3+ in Ca9Tb(PO4)7, Dy3+ in Ca9Dy(PO4)7, Mn2+ in Mn:Ca3(PO4)2 and Mn:Ca9Lu(PO4)7 were identified as hole traps and radiative recombination centers in the TSL mechanism. Ca9Tb(PO4)7 was found to be a high intensity green persistent phosphor whereas Mn:Ca9Lu(PO4)7 is a red persistent phosphor suitable for in vivo imaging application. 相似文献
245.
Rajia Ait Benhamou Gilles Wallez Pascal Loiseau Bruno Viana Mohamed Elaatmani Mohamed Daoud Abdelwahed Zegzouti 《ChemInform》2010,41(52):no-no
RbMgPO4 is synthesized by solid state reaction of stoichiometric mixtures of Rb2CO3, 4MgCO3·Mg(OH)2·5H2O, and (NH4)2HPO4 (900 °C, 12 h). 相似文献
246.
Dr. Ram Kumar Dr. Yang Song Anissa Ghoridi Dr. Philippe Boullay Prof. Gwenaelle Rousse Prof. Christel Gervais Dr. Cristina Coelho Diogo Dr. Houria Kabbour Dr. Capucine Sassoye Patricia Beaunier Dr. Victor Castaing Dr. Bruno Viana Dr. Maria Luisa Ruiz Gonzalez Prof. José Gonzalez Calbet Prof. Christel Laberty-Robert Dr. David Portehault 《Angewandte Chemie (International ed. in English)》2023,62(26):e202303487
Mixed-anion compounds widen the chemical space of attainable materials compared to single anionic compounds, but the exploration of their structural diversity is limited by common synthetic paths. Especially, oxychlorides rely mainly on layered structures, which suffer from low stability during photo(electro)catalytic processes. Herein we report a strategy to design a new polar 3D tetrahedral framework with composition Zn4Si2O7Cl2. We use a molten salt medium to enable low temperature crystallization of nanowires of this new compound, by relying on tetrahedral building units present in the melt to build the connectivity of the oxychloride. These units are combined with silicon-based connectors from a non-oxidic Zintl phase to enable precise tuning of the oxygen content. This structure brings high chemical and thermal stability, as well as strongly anisotropic hole mobility along the polar axis. These features, associated with the ability to adjust the transport properties by doping, enable to tune water splitting properties for photoelectrocatalytic H2 evolution and water oxidation. This work then paves the way to a new family of mixed-anion solids 相似文献