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991.
Chemoenzymatic production of (+)-coriolic acid from trilinolein: Coupled synthesis and extraction 总被引:1,自引:0,他引:1
Mohamed Gargouri Marie Dominique Legoy 《Journal of the American Oil Chemists' Society》1997,74(6):641-645
Chemoenzymatic conversion of trilinolein to (+)-coriolic acid was investigated in this work. Lipase-catalyzed hydrolysis of
trilinolein and lipoxygenation of liberated linoleic acid were coupled in a two-phase medium that consisted of a pH 9 borate
buffer and a water-immiscible organic solvent (octane). High concentrations of trilinolein could be dissolved in the organic
phase (up to 340 mM). Linoleic acid, liberated after hydrolysis, transferred to the aqueous phase and was enzymatically converted
to the preferred 13(S)-hydroperoxy-9Z,11E-octadecadienoic acid with soybean lipoxygenase-1. This product, which remained in the aqueous phase, could be recovered by
centrifugation and then chemically reduced to (+)-coriolic acid (purity >95%). Recovery of this compound by liquid-liquid
extraction was easy. The structure of (+)-coriolic acid has been confirmed by 1H nuclear magnetic resonance spectroscopy, mass spectrometry, and infrared spectroscopy. High yields were obtained with pure
trilinolein or sunflower oil as initial substrates. 相似文献
992.
993.
This paper proposes to study the thermodynamics performances of a new absorption heat-transformer cycle, where the separation step is obtained by the cooling and settling of a partially miscible mixture at low temperature. This new cycle has been called an absorption-demixing heat transformer (ADHT) cycle. A numerical simulation code has been written, and has allowed us to evaluate the temperature lift and thermal yield of 2 working pairs. Both high qualitative and quantitative performances have been obtained, so demonstrating the feasibility and industrial interest for such a cycle. Moreover a comparison of the simulation results with performances really obtained on an experimental ADHT has confirmed the pertinence of the simulation code. 相似文献
994.
We present a programming language for robots which we have implemented based on the Ada language. It is an interpreted language which permits dynamic configuration of software. It manipulates Ada tasks and subroutines. One of the Ada tasks is an inference engine of a logic programming language adapted to real-time constraints. We show how the conjunction of Ada tasks, to perform perception and action functions on the robot, to logic programs, for the control of these tasks, both manipulated by the IAda language, gives a powerful environment for robot programming. 相似文献
995.
996.
997.
In this paper the authors present the main problem of operating video tape recorders for television production, viz. picture degradations through multiple generations, which could be cancelled by using digital machines. Efficient error protection is mandatory. Burst error statistics are given as collected on a laboratory digital recorder as well as a physical interpretation. Different protection methods are used for luminance and colour differences, which results in sharing the available redundancy between two distinct coding systems. Adequate codes are selected through the use of two bounds stated as theorems. The main parameters of a possible system are presented. They are likely to be improved when further information is available to make an operating system practical. 相似文献
998.
The economy of telecommunications is presently characterized by differentiation of services. This paper explores this differentiation in different institutionnal situations starting from very simple but realistic assumptions. It is established that the most efficient situation should associate a technical monopoly of the network with a competitive supply of services. 相似文献
999.
Jean-Louis Besson Dominique Billieres Tanguy Rouxel Paul Goursat Robert Flynn Stuart Hampshire 《Journal of the American Ceramic Society》1993,76(8):2103-2105
Glasses have been prepared in the Si -Y-Al O-N system by melting mixtures of silica, alumina, yttria, and silicon nitride. One particular glass containing 17 equiv% N has been investigated to Observe the crystallization at temperatures in the range 1050o -1300o C. The major crystalline phase observed is Y2 Si2 O7 , existing as the α form below 1200o C and the β form above this temperature. Properties of the glass-ceramic, including thermal expansion coefficient, hardness, electrical resistivity, and creep have been assessed. 相似文献
1000.
Stephane Marais Yuichi Hirata Dominique Langevin Corinne Chappey Trong Q. Nguyen Michel Metayer 《Materials Research Innovations》2002,6(2):79-88
The transport of water and gases (pure oxygen and carbon dioxide) through poly(ethylene-co-vinyl acetate) (EVA) films of different
VA contents and through a low density polyethylene LDPE (used as reference with 0 wt.% VA), was analysed by permeation and
sorption measurements.
In the case of water, for EVA of 70 wt.% VA, a plasticization effect on the material was observed. For EVA of 19 wt.% VA,
there was no plasticization, while for EVA of 4.5 wt.% VA and for LDPE, the water diffusion coefficient decreases with increasing
water. An empirical law was then found to account for the reduction of the water diffusivity. A negative plasticization effect
was attributed to the formation of water clusters in these rather non polar polymers. This latter result was confirmed by
sorption measurements and infra-red spectroscopy. The increase in water sorption extent with the VA content leads to a steady
increase in the water permeability in the EVA copolymers.
In the case of gas permeation, both for O2 and CO2 and whatever the VA content of the copolymer used, the experimental curves are characterized by a constant diffusion coefficient.
This is confirmed by sorption experiments. In terms of gas permeability, EVA copolymers are characterized by low coefficients
especially for oxygen. In the EVA rubbery copolymers, The O2 solubility coefficient does not increase with the VA content due to the lack of polar interactions, while the CO2 one increases due to the overall interactions between CO2 induced dipoles and the polar the VA carbonyl groups. For these copolymers, the H2O/CO2 and H2O/O2 selectivities are very high. The experimental values of the selectivities indicate that these EVA copolymers appear as good
candidates for applications using high perm-selectivity properties.
Electronic Publication 相似文献