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71.
We describe all isometric immersions f:S
n
s
S
s
n
+2/S
s
n
n–s4, whenever the set of totally geodesic points does not disconnect S
s
n
, where S
n
s
denotes the complete n-dimensional indefinite Riemannian space form of constant positive curvature 1 and signature s. 相似文献
72.
Patricia M. G. Paiva Luana C. B. B. Coelho 《Applied biochemistry and biotechnology》1992,36(2):113-118
Two additional electrophoretically distinct molecular forms, isoforms (iso) 2 and 3, with lectin properties were isolated
fromCratylia mollis Mart, seeds (FABACEAE), by extraction with 0.15M NaCl and ammonium sulfate fractionation, followed by chromatography on Sephadex
G-75 and Bio-Gel P-200 (iso 2), as well as CM-Cellulose and Sephadex G-75 (iso 3). Both isoforms were human group nonspecific
and showed distinct specificity. Polyacrylamide gel electrophoresis resolved iso 2 and 3 in polypeptides of apparent mol wts
60 and 31 kDa, respectively; a distinct isoelectric focusing pattern was obtained for iso 2 and 3, under denaturing and reducing
conditions. 相似文献
73.
A rapid, selective, sensitive and simple fluorescence method was developed for the direct determination of celecoxib in capsules. The capsules were emptied, pulverized and dissolved in either ethanol or acetonitrile, sonicated and filtered. Direct fluorescence emission was measured at 355±5 nm (exciting at 272 nm). The method was fully validated and the recoveries were excellent, even in presence of excipients. 相似文献
74.
The preferred conformations of the tripeptide glutathione have been investigated by performing quantum mechanical calculations using the PCILO method. A series of model compounds representing fragments of the tripeptide has been studied as well as the complete molecule. The results are compared with the available experimental data. 相似文献
75.
Anna Rizzolo Patrizia Lombardi Maristella Vanoli Stefano Polesello 《Journal of separation science》1995,18(5):309-314
Capillary GC/sensory analysis was used to judge if dynamic headspace on sliced pulp and on intact fruit, and solvent extraction could collect the “character impact” and the “contributory” aroma compounds in peaches. Capillary GC/sensory data showed that the headspace techniques selectively recovered the “contributory” volatile compounds, which are strictly related to the characteristic odor of the various peach cultivars, whereas solvent extraction better quantified the “character impact” compounds (lactones). 相似文献
76.
77.
Asymmetry and magnetism in bis(oximato)-bridged heterobimetallic compounds: a computational approach
Cano J Rodríguez-Fortea A Alemany P Alvarez S Ruiz E 《Chemistry (Weinheim an der Bergstrasse, Germany)》2000,6(2):327-333
A density functional study of exchange coupling was carried out for a series of heterobinuclear oximato-bridged transition metal complexes. Model calculations were used to examine the influence of the electronic configuration of the metal atoms on the coupling constants. This analysis was complemented by a study of the variation of the coupling constant with the most usual structural distortions within this family of compounds. The influence of the nature of the terminal ligands as well as that of the symmetry on the bridge were also investigated. 相似文献
78.
JPC – Journal of Planar Chromatography – Modern TLC - The thin-layer chromatographic behavior of three of the newest oral antidiabetic agents, pioglitazone, rosiglitazone, and... 相似文献
79.
De Salvo G Gattuso G Notti A Parisi MF Pappalardo S 《The Journal of organic chemistry》2002,67(3):684-692
A series of tri-O-substituted 1,3-bridged calix[5]arene crown-6 ethers bearing alkyl, arylalkyl, alkoxyalkyl, and alkoxycarbonylmethyl residues at the lower rim and either (t)()Bu or H substituents at the upper rim have been synthesized. (1)H NMR studies have shown that p-tert-butylcalix[5]crowns, irrespective of the size and nature of their lower rim pendant groups, adopt preorganized conelike conformations, whereas p-H-calix[5]crowns with bulky substituents preferentially exist in solution as partial cone conformers (C(1) symmetry). Calix[5]crown derivatives behave as mono- or ditopic receptors for isomeric butylammonium ions, forming endo-cavity (inside the calixarene cup) and/or exo-cavity (at the crown ether moiety) 1:1 complexes according to the shape of the guest. These two binding modes can be clearly distinguished and monitored by (1)H NMR titration experiments. 相似文献
80.
Patricia Cava-Montesinos Agustin Pastor Miguel de la Guardia 《Analytica chimica acta》2003,481(2):291-300
A sensitive procedure has been developed for selenium and tellurium determination in milk by hydride generation atomic fluorescence spectrometry (HG-AFS) after microwave-assisted sample digestion. The method provides sensitivity values of 1591 and 997 fluorescence units ng−1 ml−1 with detection limits of 0.005 and 0.015 ng ml−1 for Se and Te, respectively. The application of the developed methodology to the analysis of cow milk samples of the Spanish market evidenced the presence of concentration ranges from 11.1 to 26.0 ng ml−1 for Se, and from 1.04 to 9.7 ng ml−1 for Te having found a good comparability with data obtained after dry-ashing of samples. 相似文献