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31.
The two new diterpenes, vierol (1) [(?)kaurane-16α,18-diol] and powerol (3) [(?)kaurane-7β,16α-diol] have been isolated from Sideritis canariensis Ait. 1 was obtained by partial synthesis from epicandicandiol (7), and 3 was related with (?)kauranol (6) and (?)kauren-7β-ol acetate (11). Reduction of the acetoxy-aldehyde 14 by the method of Huang-Minlon and posterior acetylation gave 11, (?)isokauren-7β-ol acetate (17) and (?)kauran-7β-ol acetate (18). 相似文献
32.
Ernesto R. González 《Journal of Electroanalytical Chemistry》1978,90(3):431-438
The adsorption of azide ions on mercury from aqueous solutions of NaN3+NaF at constant ionic strength has been studied by measurements of the double layer capacity. Taking into account changes in the structure of the diffuse layer, it was possible to show that the properties of the inner layer are similar to those observed previously in solutions of pure NaN3, and that the same adsorption isotherm applies to both systems. 相似文献
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Julio Belmar Claudio Jimnez C. Ruiz‐Prez F. S. Delgado Ricardo Baggio 《Acta Crystallographica. Section C, Structural Chemistry》2006,62(10):o599-o601
In the title compound, C15H20N2O, the bond distances and angles are consistent with the presence of the hydroxy tautomer. This tautomer was unambiguously determined by the clear presence of a H atom bonded to oxygen, as well as the total absence of any residual electron density around the N atom in the heterocycle, thus precluding any possibility of desmotropism. 相似文献
35.
Preparation and sedimentation behavior in magnetic fields of magnetite-covered clay particles 总被引:4,自引:0,他引:4
Galindo-González C de Vicente J Ramos-Tejada MM López-López MT González-Caballero F Durán JD 《Langmuir : the ACS journal of surfaces and colloids》2005,21(10):4410-4419
This work is devoted to the preparation of magnetite-covered clay particles in aqueous medium. For this purpose, magnetite nanoparticles were synthesized by a coprecipitation method. These magnetic particles are adhered to sodium montmorillonite (NaMt) particles in aqueous suspensions of both materials, by appropriate control of the electrolyte concentrations. The best condition to produce such heteroaggregation corresponds to acid pH and approximately 1 mol/L ionic strength, when the electrokinetic potentials (zeta-potential) of both NaMt and Fe3O4 particles have high enough and opposite sign, as demonstrated from electrophoresis measurements. When a layer of magnetite re-covers the clay particles, the application of an external magnetic field induces a magnetic moment in clay-magnetite particles parallel to the external magnetic flux density. The sedimentation behavior of such magnetic particles is studied in the absence or presence of an external magnetic field in a vertical direction. The whole sedimentation behavior is also strongly affected by the formation of big flocculi in the suspensions under the action of internal colloidal interactions. van der Waals and dipole-dipole magnetic attractions between magnetite-covered clay particles dominate the flocculation processes. The different relative orientation of the clay-magnetite particles (edge-to-edge, face-to-edge, and face-to-face) are discussed in order to predict the most favored flocculi configuration. 相似文献
36.
López-Hernández J González-Castro MJ Pereda-González M 《Journal of chromatographic science》2000,38(9):383-385
A high-performance liquid chromatographic method using refractive index detection for the determination of glycogen in sea urchin (Paracentrotus lividus) gonads is developed. After alkaline digestion with sodium carbonate, samples are adjusted to pH 4.6 with citric acid and incubated with amyloglucosidase to hydrolyze the glycogen. The resulting glucose is determined using a Spherisorb NH2 column as the stationary phase and an acetonitrile-water mixture (80:20, v/v) as the mobile phase. The relative standard deviation (%) was 3.57, the limit of detection was 40.1 microg/mL, and the recovery percentage was 97.2%. 相似文献
37.
Gómez-Carrasco S González-Snchez L Aguado A Roncero O Alvariño JM Hernández ML Paniagua M 《The Journal of chemical physics》2004,121(10):4605-4618
A theoretical study of the F(2P) + OH(2Pi) --> HF(1Sigma+) + O(3P) reactive collisions is carried out on a new global potential energy surface (PES) of the ground 3A" adiabatic electronic state. The ab initio calculations are based on multireference configuration interaction calculations, using the aug-cc-pVTZ extended basis sets of Dunning et al. A functional representation of the PES shows no nominal barrier to reaction, contrary to previous results by others. Wave packet and quasiclassical trajectory calculations have been performed for this PES to study the F + OH(v = 0,j) reactive collision. The comparison was performed at fixed and constant values of the total angular momentum from 0 to 110 and relative translational energy up to 0.8 eV. The reaction presents a dynamical barrier, essentially due to the zero-point energy for the bending vibration near the saddle point. This determines two different reaction mechanisms. At energies higher than approximately 0.125 eV the reaction is direct, while below that value it is indirect and mediated by heavy-light-heavy resonances. Such resonances, also found in the simulations of the photodetachment spectrum of the triatomic anion, manifest themselves in the quasiclassical simulations, too, where they are associated to periodic orbits. 相似文献
38.
An extraction--spectrophotometric method is described for the determination of oxalate, based on the formation of a mixed ligand vanadium (V)--mandelohydroxamic acid--oxalate complex. The complex was extracted into a solution of trioctylmethylammonium chloride (Adogen 446) in toluene and the absorbance measured at 535 nm. The experimental variables and interferences in this determination were studied. The detection limit is 0.5 microgram ml-1 and the range of application is between 2 and 8 micrograms ml-1. The method was applied to the determination of oxalate in urine and blood serum. 相似文献
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