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101.
A method for the detection and quantification of the microcystins (MCs)-MC-LR, MC-RR and MC-YR-in biological samples by matrix solid-phase dispersion (MSPD) has been developed. The optimum extraction conditions were 500 mg of liver or kidney, C18 bonded silica as dispersant, and a mixture methanol-water (70:30) as eluent. The MCs were determined by liquid chromatography electrospray mass spectrometry (LC/ES/MS). Recoveries of biological extracts at three different spiked levels (1-10 mg kg(-1)) ranged from 40.5 to 87.0% in liver, and from 52.5 to 74.5 in kidney. R.S.D.s were < 15.6% and < 10.6%, respectively. The detection and quantification limits were 0.05 and 0.5 mg kg(-1), for all MCs. The method was applied to MCs detection in liver and kidney of rat previously injected i.p. with MC-LR. Results showed the presence of MC-LR in the liver of the animals injected with the highest dose. 相似文献
102.
Yolanda Pérez Isabel del Hierro Isabel Sierra Magda Monari Antonio Otero 《Journal of organometallic chemistry》2004,689(22):3492-3500
A variety of monocyclopentadienyl alkoxo titanium dichloride and bisalkoxo titanium dichloride complexes have been prepared and characterized by spectroscopic techniques. The titanium derivatives containing both cyclopentadienyl and various alkoxo ligands [Ti(η5-C5H5)(OR)Cl2] (1-5) have been synthesized from the reaction of [Ti(η5-C5H5)Cl3] with 1 equivalent of the corresponding alcohol in THF in the presence of triethylamine (ROH = Adamantanol, 1R,2S,5R-(−)-menthol, 1S-endo-(−)-borneol, cis-1,3-(−)-benzylideneglycerol, 1,2:3,4-di-O-isopropylidene-α-d-galactopyranose). The bisalkoxo titanium dichloride derivatives [TiCl2(OR)2] (6-10) have been prepared by a redistribution reaction between Ti(OR)4 and TiCl4 compounds 6-8 (OR = Adamantanoxy, (1R,2S,5R)-(−)menthoxy, (1S-endo)-(−)-borneoxy) and by reaction of [Ti(OR)2(OPri)2]2 with CH3COCl compounds 9 and 10 (OR = 1,2:3,4-di-O-isopropylidene-α-d-galactopyranoxy, and 1,2:5,6-di-O-isopropylidene-α-d-glucofuranoxy). The molecular structures of 2 and 3 have been determined by single crystal X-ray diffraction studies. 相似文献
103.
Comparative Study of Polymeric Supports as the Base of Immobilisation of Chemically Modified Enzymes
One of the difficulties in using optical biosensors based on enzymatic reactions is the immobilisation of the enzyme involved
in the determination. A detailed study has been carried out of the various polymeric supports which could provide a potential
alternative for the immobilisation of chemically modified enzymes. Before immobilisation, the enzyme is attached by means
of a covalent bond to a fluorescent probe, which is optically active in the visible region. The main advantage of this covalent
bond is that it is possible to follow the enzymatic reaction by fluorescence without the need for immobilising any further
reagent (reagentless biosensors). The results indicate that the most stable and reproducible polymeric supports are derived
from polyacrylamide obtained by UV photopolymerisation. The experiments have been carried out using chemically modified glucose
oxidase as the model enzyme. The films thus obtained have a lifetime of at least two months, an RSD of 9.2%, and a linear
range of 300 to 2000 mg L−1 of glucose. They are completely reversible by regeneration in an appropriate buffer solution. 相似文献
104.
We give a characterization of exact sequences of Banach or quasi-Banach spaces having strictly singular quotient map or strictly
cosingular embedding. We present two balance principles showing that such sequences can only exist when the sizes of the subspace and the quotient space are not too different.
Received: 7 November 2005
The research was supported in part by the project MTM2004-02635. 相似文献
105.
Simone Cristoni Laura Molin Antonella Lai Luigi Rossi Bernardi Salvatore Pucciarelli Marco Agostini Chiara Bedin Donato Nitti Roberta Seraglia Ombretta Repetto Vincenza Flora Dibari Rosaria Orlandi Pablo Martínez‐Lozano Sinues Pietro Traldi 《Rapid communications in mass spectrometry : RCM》2009,23(17):2839-2845
106.
Yolanda Gonz lez M. Blanca Ros Jose Luis Serrano Miguel Angel Perez-jubindo 《Liquid crystals》1995,18(5):751-760
A comparative study of the liquid crystal and ferroelectric properties of several achiral, racemic and non-racemic 2,6-naphthyl benzoates and their 1,4-phenyl benzoate analogues is reported. In terms of pure compounds, both central core structures give rise to similar mesophase sequences; however, the naphthalene derivatives exhibit broader and more thermally stable liquid crystalline states. On the other hand, both central core units give rise to equivalent electric and optoelectronic properties when the compounds are used as chiral dopants in ferroelectric liquid crystal mixtures. 相似文献
107.
[reaction: see text] Two separate strategies have been developed for the preparation of highly substituted pyridines from 1,2,4-triazines via the inverse-electron-demand Diels-Alder reaction: a microwave-promoted, solvent-free procedure and a tethered imine-enamine (TIE) approach. Both routes avoid the need for a discrete aromatization step and offer significant advantages over the classical methods, giving a wide variety of tri-, tetra-, and penta-substituted pyridines in high, optimized yields. 相似文献
108.
We report an experimental approach to separate temperature dependent reversible and irreversible contributions to the perpendicular magnetic anisotropy of Fe films grown at low temperatures on Cu(001) substrates. The surface anisotropy K(S)(T) is found to decrease linearly with temperature, causing a thermally induced spin reorientation into the plane. The irreversible shift of the spin reorientation transition and the coercivity of the iron films are directly correlated to the increasing Fe island size during annealing. The increased coercivity is discussed in terms of domain wall energy inhomogeneities provided by the islands. 相似文献
109.
Elena?FernándezEmail author Yolanda?Hinojosa Justo?Puerto 《Annals of Operations Research》2005,136(1):259-283
In this paper we deal with two stationary loss queuing network location models. We analyze the influence of filtering policies
on the locational aspect of the problems. We assume that requests for service are placed at nodes of a transportation network
and they arrive in time as independent homogeneous Poisson processes with different input rates. The considered policies only
cover a given proportion of requests even if there are idle service units. This proportion is stationary and fixed in advance
and only depends on the node where the request is originated. The objective is to find the location of the facilities together
with the filtering policy to be applied that minimize the expected total cost per unit time with respect to a given cost structure.
Properties and computational results are presented enabling the resolution of these problems efficiently and showing the good
performance of filtering policies in terms of both the overall operating costs, and the demand that is served. 相似文献
110.
John Snyder Koji Nakanishi Gloria Chaverria Yolanda Leal Celso C. Ochoa Xorge A. Dominguez 《Tetrahedron letters》1981,22(50):5015-5018
The fruit extract of the Mexican shrub Sarg. has afforded castanaguyone ; it is the first biisocoumarin encountered in nature. 相似文献