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61.
Two published procedures for glass capillary column production are applied to produce capillaries for chromatography of polar natural compounds. Soda lime glass capillaries, after leaching with aqueous HCL, are either treated with colloidal silicic acid or with barium carbonate and coated with either Silar 7CP or SE 52. A test mixture as well as polar carbohydrate and peptide mixtures are chromatographed on the different columns and their chromatographic properties are evaluated. Combined capillary gas chromatography-electron impact and chemical ionization mass spectrometry are used for identification of the peptide sequence. 相似文献
62.
Barontini F. Marsanich K. Cozzani V. 《Journal of Thermal Analysis and Calorimetry》2004,78(2):599-619
The TG-FTIR technique was used in the present study to investigate the thermal degradation behaviour of materials containing
brominated flame retardants under fire conditions. Time-temperature profiles and oxygen concentrations typical of selected
fire scenarios were reproduced in the thermogravimetric analyzer, while the characterization of the gaseous products generated
was performed by the simultaneous FTIR analysis. FTIR analysis combined with the use of specific calibration procedures allowed
the quantitative estimation of the gaseous products evolved as a function of experimental conditions. The results obtained
allowed the straightforward assessment and the comparison of the quantities of hydrogen bromide formed in the oxidation and
thermal degradation of pure brominated flame retardants and of flame retarded materials of industrial interest. Hydrogen bromide
yields resulted dependent on the experimental conditions used, such as oxygen concentration and heating rate. Although TG-FTIR
experiments only provide a representation of the actual heterogeneous combustion products in real fire conditions, the coupled
TG-FTIR technique proved to be a straightforward experimental methodology allowing one to obtain reference data on the nature
and quantities of the macropollutants generated in a fire.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
63.
海洋天然产物研究新进展 总被引:12,自引:0,他引:12
海洋天然产物化学是目前天然产物化学中最活跃的研究领域之一。近年来,从海洋生物中分离到非常多的化学结构和生理活性上令人注目的新化合物,引起了有机化学家和药物化学家的关注。本文按萜类、太环内酯、聚醚类、生物碱,环肽、含氰化合物、甾醇、聚丙酸酯类化合物等化学结构来概述海洋天然产物研究近年来的进展。 相似文献
64.
Patrizia Ciminiello Carmela Dell'Aversano Martino Forino Federico Umberto Santelia Emmanuel N. Pitsinos 《Tetrahedron》2006,62(33):7738-7743
The analysis of a batch of toxic mussels (Mytilus galloprovincialis) from the Northern Adriatic Sea led to the isolation of a novel oxazinin, oxazinin-4. Its structure including the relative stereochemistry has been elucidated through extensive NMR analysis. A synthetic route to oxazinins has been crucial in establishing the absolute stereochemistry of oxazinin-4 and for reassigning the absolute C-2 configuration of oxazinin-1 and -2 previously isolated from toxic shellfish and stereostructurally characterized. 相似文献
65.
Photoreduction of nitro compounds is accompanied by formation of various radical products that can react with the starting
nitro compound, thus causing deviation of the decomposition kinetics from the first-order kinetics with respect to the nitro
compound. The results of quantum chemical modeling of the reactions of nitro compounds with radicals and the pathways of further
transformations of radical adducts formed in the reactions are presented.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 202–206, February, 2006. 相似文献
66.
Summary A method has been developed for the determination of thirteen phenylurea herbicide residues in milk. It involves one-step solvent extraction of the milk with methanol by ultrasonication. The extract is cleaned up on an Amberchrom resin cartridge. Reversed-phase, gradient elution, high-performance liquid chromatography with UV detection at 242 nm is used to analyse the residues. The recovery of thirteen phenylurea pesticides is quantitative, ranging from 71.4% to 97.9% for the individual herbicides investigated at concentrations around 0.05 mg kg–1 and from 65.1% to 95.6% around 0.005 mg kg–1. The method is not associated with any of the emulsion problems common to conventional solvent extraction, which considerably reduce the sample clean-up process compared with existing methods. 相似文献
67.
本文按合成产物的结构类型,综述分子内 Diels-Alder 反应在有机合成方面的新进展。 相似文献
68.
Paul-Henri Ducrot Albert Kollmann Adil E. Bala Amel Majira Lucien Kerhoas Robert Delorme Jacques Einhorn 《Tetrahedron letters》1998,39(52):7282-9658
Two new antifungal resveratrol dimers, cyphostemmins A-B (1–2), have isolated from the roots of Cyphostemma crotalarioides planch (Vitaceae) together with resveratrol 3 and previously known reseveratrol dimers (4–7). Structures of these new compounds have been established on the basis of their MS and 1H and 13C NMR spectroscopic data. 相似文献
69.
《Indagationes Mathematicae》2022,33(3):598-624
We construct left invariant special Kähler structures on the cotangent bundle of a flat pseudo-Riemannian Lie group. We introduce the twisted cartesian product of two special Kähler Lie algebras according to two linear representations by infinitesimal Kähler transformations. We also exhibit a double extension process of a special Kähler Lie algebra which allows us to get all simply connected special Kähler Lie groups with bi-invariant symplectic connections. All Lie groups constructed by performing this double extension process can be identified with a subgroup of symplectic (or Kähler) affine transformations of its Lie algebra containing a nontrivial 1-parameter subgroup formed by central translations. We show a characterization of left invariant flat special Kähler structures using étale Kähler affine representations, exhibit some immediate consequences of the constructions mentioned above, and give several non-trivial examples. 相似文献
70.
J. A. Yan 《Applied Mathematics and Optimization》1995,31(2):137-153
Some sharp results about Weiner and Wick products of whitenoise functionals are obtained. Using the inequality of Wick products we show to what extent scaling transformations, translations, and Sobolev differentiations can be performed on white-noise functionals.This work was supported by the National Natural Science Foundation of China. This paper is an enlargement and revised version of the paper entitled Products and Transforms of White-Noise Functionals (preprint, 1990). 相似文献