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111.
María del Pilar Godoy‐Caballero Teresa Galeano‐Díaz María Isabel Acedo‐Valenzuela 《Journal of separation science》2012,35(24):3529-3539
In this article, we proposed very simple procedures to analyze important phenolic compounds in olive oil samples from different olive varieties. A nonaqueous CE method has been employed. The main phenolic alcohols in virgin olive oil (tyrosol and hydroxytyrosol) and some among the most abundant secoiridoid aglycone derivatives (dialdehydic form of decarboxymethyl elenoic acid linked to hydroxytyrosol, an isomer of oleuropein aglycone and the dialdehydic form of decarboxymethyl elenoic acid linked to tyrosol) were determined by a direct injection into the capillary of the olive oil dissolved in 1‐propanol 1:1 v/v. For the determination of compounds present at lower concentrations, a very simple liquid–liquid extraction method with ethanol has been proposed. The extraction was performed using a relationship 5:1 w/v olive oil/ethanol to achieve the necessary preconcentration of the analytes and the ethanolic extracts were directly injected into the capillary to obtain a very important time reduction. Good recoveries were obtained with both the procedures, using an internal standard. Finally, these procedures were applied to the analysis of these compounds in extra virgin olive oil samples from different varieties of olive. 相似文献
112.
Xavier Companyó Guillem Valero Luis Crovetto Dr. Albert Moyano Prof. Dr. Ramon Rios Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(27):6564-6568
Panacea for aldol desymmetrizations : We describe an easy entry for the desymmetrization of 4‐substituted‐cyclohexanones catalyzed by proline, using as cocatalysts different hydrogen‐bonding donors (see scheme), which dramatically improves the catalytic efficiency of proline in desymmetrization reactions.
113.
Diego Sierra Andres Muñoz Fernando Godoy A. Hugo Klahn Andres Ibañez M. Teresa Garland Mauricio Fuentealba 《Polyhedron》2009
Diphenylphosphinecyrhetrene ligand (η5-C5H4PPh2)Re(CO)3 (1) reacts with 1 equiv. of PdCl2(NCPh)2 to form, after workup, the square-planar trans-[(η5-C5H4PPh2)Re(CO)3]PdCl2(NCMe) (2). Similarly, reaction of 1 with (tetrahydrothiophene)AuCl produces, in excellent yield, the bimetallic complex [(η5-C5H4PPh2)Re(CO)3]AuCl (3) with a linear P–Au–Cl moiety. From the reaction of 2 equiv. of 1 with CuBr(SMe2) the planar-trigonal complex [(η5-C5H4PPh2)Re(CO)3]2CuBr (4) was obtained. 31P NMR and X-ray crystallography demonstrate, for the three cases, that (η5-C5H4PPh2)Re(CO)3 acts as a monodentate ligand. The structural parameters of the bimetallic complexes are compared with related diphenylphosphinoferrocene metal complexes, described in the literature. 相似文献
114.
An Efficient Semi-Analytical Method to Compute Displacements and Stresses in an Elastic Half-Space with a Hemispherical Pit 下载免费PDF全文
Valeria Boccardo Eduardo Godoy & Mario Durá n 《advances in applied mathematics and mechanics.》2015,7(3):295-322
This paper presents an efficient method to calculate the displacement and
stress fields in an isotropic elastic half-space having a hemispherical pit and being subject
to gravity. The method is semi-analytical and takes advantage of the axisymmetry
of the problem. The Boussinesq potentials are used to obtain an analytical solution
in series form, which satisfies the equilibrium equations of elastostatics, traction-free
boundary conditions on the infinite plane surface and decaying conditions at infinity.
The boundary conditions on the free surface of the pit are then imposed numerically,
by minimising a quadratic functional of surface elastic energy. The minimisation
yields a symmetric and positive definite linear system of equations for the coefficients
of the series, whose particular block structure allows its solution in an efficient and
robust way. The convergence of the series is verified and the obtained semi-analytical
solution is then evaluated, providing numerical results. The method is validated by
comparing the semi-analytical solution with the numerical results obtained using a
commercial finite element software. 相似文献
115.
Edison?Alberto?Fernández-CulmaEmail author Yamile?Godoy 《Mathematical Physics, Analysis and Geometry》2018,21(1):8
Let G be a Lie group of even dimension and let (g, J) be a left invariant anti-Kähler structure on G. In this article we study anti-Kähler structures considering the distinguished cases where the complex structure J is abelian or bi-invariant. We find that if G admits a left invariant anti-Kähler structure (g, J) where J is abelian then the Lie algebra of G is unimodular and (G, g) is a flat pseudo-Riemannian manifold. For the second case, we see that for any left invariant metric g for which J is an anti-isometry we obtain that the triple (G, g, J) is an anti-Kähler manifold. Besides, given a left invariant anti-Hermitian structure on G we associate a covariant 3-tensor ?? on its Lie algebra and prove that such structure is anti-Kähler if and only if ?? is a skew-symmetric and pure tensor. From this tensor we classify the real 4-dimensional Lie algebras for which the corresponding Lie group has a left invariant anti-Kähler structure and study the moduli spaces of such structures (up to group isomorphisms that preserve the anti-Kähler structures). 相似文献
116.
An ion-pair liquid chromatographic assay was developed and validated for the determination of ceftriaxone in cerebrospinal fluid. Chromatographic separation was achieved on a C18 column (125 x 4 mm, 5 microm) with detection at 270 nm, a 1 mL/min flow rate and a 50 microL loop. The mobile phase consisted of 300 mL acetonitrile, 50 mL 0.1M phosphate buffer (pH 7.4), 3.2 g tetrabutylammonium bromide as the ion-pairing agent, and dilution with distilled deionized water to 1 L. Cephradine was used as the internal standard. The assay was linear for ceftriaxone concentrations of 0.5-50 microg/mL. The coefficients of variation for precision were <4.61%. The accuracy ranged from 96.07 to 102.42%. The detection and quantitation limits were 0.019 and 0.065 microg/mL, respectively. This method was used to quantify ceftriaxone in the cerebrospinal fluid of children with meningitis. The results showed that the method described here is useful for the determination of ceftriaxone in cerebrospinal fluid. 相似文献
117.
The symmetric derivatives of pyridoxal with thiocarbohydrazide and carbohydrazide, and the asymmetric derivatives of pyridoxal and salicylaldehyde with the same hydrazides have been synthesized and their analytical potential for spectrophotometric and kinetic fluorimetric determination of metal ions was studied. Gallium(III) and PyMAU(1,3-bis{[4-(2-methyl-3-hydroxy-5-hydroxymethyl)pyridyl]methyleneaminourea at pH = 4.2 form a complex with a single absorption maximum at 425 nm, which can be extracted into cyclohexanone in the presence of a controlled amount of sodium perchlorate. The extract has maximum absorbance at 435 nm. Both systems can be used for determining gallium. The optimal range of gallium concentration for measurement in a 1-cm cell is 0.5-1.25 gmg/ml for the procedure in homogeneous medium ((425) = 3.76 x 10(4).mole(-1).cm(-1)) and 0.25-1.25 mug/ml for the extraction procedure ((435) = 5.30 x 10(4) 1.mole(-1).cm(-1). The latter procedure has been applied to the determination of gallium in alloys and fly-ash. 相似文献
118.
L. A. Schuch D. J. R. Nordemann A. Zago D. L. Dallpai J. M. Godoy B. Pecequilo 《Journal of Radioanalytical and Nuclear Chemistry》1994,177(1):101-106
Various types of soil samples were collected in the southern part of Brazil, with depth intervals of 5 cm, down to 50 cm, using a specially designed sampler. Pedological analysis of these soils were performed. Nuclear activities of137Cs (expressed in Bq m–2) and radioactive natural element (226Ra,228Ra and40K) concentrations were determined by low background gamma-ray spectrometry.137Cs concentrations were correlated with radioactive natural element concentrations and pedological, climatological and geographic parameters related to the soil samples collected. 相似文献
119.
New synthesis procedures are described to tetranuclear manganese carboxylate complexes containing the [Mn(4)O(2)](8+) or [Mn(4)O(3)X](6+) (X(-) = MeCO(2)(-), F(-), Cl(-), Br(-), NO(3)(-)) core. These involve acidolysis reactions of [Mn(4)O(3)(O(2)CMe)(4)(dbm)(3)] (1; dbm is the anion of dibenzoylmethane) or [Mn(4)O(2)(O(2)CEt)(6)(dbm)(2)] (8) with HX (X(-) = F(-), Cl(-), Br(-), NO(3)(-)); high-yield routes to 1 and 8 are also described. The X(-) = NO(3)(-) complexes [Mn(4)O(3)(NO(3))(O(2)CR)(3)(R'(2)dbm)(3)] (R = Me, R' = H (6); R = Me, R' = Et (7); R = Et, R' = H (12)) represent the first synthesis of the [Mn(4)O(3)(NO(3))](6+) core, which contains an unusual eta(1):mu(3)-NO(3)(-) group. Treatment of known [Mn(4)O(2)(O(2)CEt)(7)(bpy)(2)](ClO(4)) with HNO(3) gives [Mn(4)O(2)(NO(3))(O(2)CEt)(6)(bpy)(2)](ClO(4)) (15) containing a eta(1):eta(1):mu-NO(3)(-) group bridging the two body Mn(III) ions of the [Mn(4)O(2)](8+) butterfly core. Complex 7 x 4CH(2)Cl(2) crystallizes in space group P2(1)2(1)2(1) with (at -168 degrees C) a = 21.110(3) A, b = 22.183(3) A, c = 15.958(2) A, Z = 4, and V = 7472.4(3) A(3). Complex 15 x (3)/(2)CH(2)Cl(2) crystallizes in space group P2(1)/c with (at -165 degrees C) a = 26.025(4) A, b = 13.488(2) A, c = 32.102(6) A, beta = 97.27(1) degrees, Z = 8, and V = 11178(5) A(3). Complex 7 contains a [Mn(4)(mu(3)-O)(3)(mu(3)-NO(3))](6+) core (3Mn(III), Mn(IV)) as seen for previous [Mn(4)O(3)X](6+) complexes. Complex 15 contains a butterfly [Mn(4)(mu(3)-O)(2)](8+) core. (1)H NMR spectra have been recorded for all complexes reported in this work and the various resonances assigned. All complexes retain their structural integrity on dissolution in chloroform and dichloromethane. Magnetic susceptibility (chi(M)) data were collected on 12 in the 5-300 K range in a 10.0 kG (1 T) field. Fitting of the data to the theoretical chi(M) vs T expression appropriate for a [Mn(4)O(3)X](6+) complex of C(3)(v)() symmetry gave J(34) = -23.9 cm(-)(1), J(33) = 4.9 cm(-)(1), and g = 1.98, where J(34) and J(33) refer to the Mn(III)Mn(IV) and Mn(III)Mn(III) pairwise exchange interactions, respectively. The ground state of the molecule is S = 9/2, as found previously for other [Mn(4)O(3)X](6+) complexes. This was confirmed by magnetization data collected at various fields and temperatures. Fitting of the data gave S = 9/2, D = -0.45 cm(-1), and g = 1.96, where D is the axial zero-field splitting parameter. 相似文献
120.
Godoy Netto Adelino V. Frem Regina C.G. Mauro Antonio E. Santos Regina H.A. Zoia Jussara R. 《Transition Metal Chemistry》2002,27(3):279-283
Mononuclear palladium(II) complexes containing both pyrazole-type ligands and thiocyanate, of general formula [Pd(SCN)2(L)2] {L = pyrazole (HPz) and 1-phenyl-3-methylpyrazole (phmPz)} have been prepared and characterized by elemental analysis, i.r. and n.m.r. spectroscopy and by single crystal X-ray diffraction methods. The Pd atom in these structures lies on the crystallographic inversion center; in a square-planar coordination geometry made by two sulfur and two nitrogen atoms of the ligands, both in trans positions. 相似文献