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101.
Gilles Barnathan Joseph Mirallès Emile M. Gaydou Nicole Boury-Esnault Jean-Michel Kornprobst 《Lipids》1992,27(10):779-784
The fatty acid composition of phospholipids from the Senegalese spongeCinachyrella alloclada was examined. Two new fatty acids not hitherto found in nature, namely 10,13-octadecadienoic acid and 16-tricosenoic acid,
were identified. 8-Hexadecenoic, 13-nonadecenoic and 5,9,13-trimethyltretradecanoic fatty acids were also found for the first
time in sponges. The latter compound (1.4% of the total fatty acid mixture), an isoprenoid fatty acid, accompanies the major
fatty acid 4,8,12-trimethyltridecanoic acid (19.7%). The monomethyl branched fatty acids (22%) identified include 23-methylpentacosanoic
acid (anteiso-26∶0), not previously observed in sponged. The major long-chain fatty acids encountered were the known 17-tetracosenoic
19-heptacosadienoic and 5,9,23-tricontatrienoic acid. Some sixty fatty acids were identified as methyl esters andN-acyl pyrrolidides by gas chromatography and gas chromatography/mass spectrometry. 相似文献
102.
The ever-increasing amount of solid waste generated by wastewater treatment plants highlights emerging economic and environmental issues. In order to develop new processes producing less sludge, the use of ozone combined with anaerobic digestion was investigated for waste activated sludge treatment. This paper was aimed at evaluating the impact of ozone pretreatment on anaerobic digestion and particularly the enhancement of biogas production. Sludge solubilization was estimated in terms of modification of chemical oxygen demand, solids and nitrogen. Batch anaerobic digestion highlighted the enhancement of ozonated sludge biodegradability. Ozonation led to an increase in biogas production. The ozone dose of 0.15 g O3/g total solids resulted in a considerable increase in the soluble COD ratio from 4% to 37%. This ozone dose achieved the highest increase in biogas production: 2.4 times greater than without chemical pretreatment. 相似文献
103.
Poly(p-tert-butoxycarbonyloxystyrene): a convenient precursor to p-hydroxystyrene resins 总被引:1,自引:0,他引:1
An efficient synthetic route to pure, high molecular weight poly(p-hydroxystyrene) is reported. The route involves synthesis of a new monomer, p-tert-butoxycarbonyloxystyrene, polymerization by radical initiation or by cationic initiation in liquid SO2, followed by thermolysis or acidolysis of the tert-butoxycarbonyl protecting group. Porous, crosslinked resin beads containing the nucleophilic, phenol pendant group have been prepared in a similar fashion from the precursor terpolymer of p-tert-butoxycarbonyloxystyrene, styrene and divinylbenzene. The utility of this resin for solid-phase synthesis has been demonstrated. 相似文献
104.
Joseph Eng Jr. Bernd Frühberger Jingguang G. Chen Brian E. Bent 《Catalysis Letters》1998,54(3):133-140
The thermal decomposition pathways of isobutene and 1-butene on both Mo(110) and 4 × 4-C/Mo(110) surfaces have been studied using high-resolution electron energy loss spectroscopy (HREELS) in order to highlight the substantially different activities of these two surfaces towards the cleavage of C–H and C–C bonds. On clean Mo(110), the CH2 group of isobutene decomposes upon heating to 150 K, producing either a /-bonded isobutenylidene [(CH3)2CCH] species or a 1,1-di-/-bonded isobutenyl [(CH3)2CC] species. Upon further heating, extensive C–H bond scission occurs to form hydrocarbon fragments which do not contain CH3 or CH2 groups, but appear to have largely intact carbon skeletons. By contrast, isobutene is molecularly adsorbed on the carbide-modified surface at 150 K. Further heating produces isobutylidyne [(CH3)2HCC] by 300 K, which subsequently decomposes via C–C bond scission to generate surface methyl groups. The different activation sequence of the C–H and C–C bonds of isobutene on clean and carbide-modified Mo(110) surfaces is also qualitatively confirmed by comparative studies of 1-butene on the two surfaces. 相似文献
105.
Tatjana Rades Chanho Pak Michèle Polisset-Thfoin Ryong Ryoo Jacques Fraissard 《Catalysis Letters》1994,29(1-2):91-103
NaY-supported bimetallic Pt-Pd catalysts have been studied by TEM, TPR and EXAFS. Small, randomly mixed particles are formed in the zeolite cages. When the Pt content is increased, a Pt core structure appears and the dispersion increases. Particle diameters are about 1–2 nm for bimetallic samples. 相似文献
106.
Information diffusion in large-scale networks has been studied to identify the users influence. The influence has been targeted as a key feature either to reach large populations or influencing public opinion. Through the use of micro-blogs, such as Twitter, global influencers have been identified and ranked based on message propagation (retweets). In this paper, a new application is presented, which allows to find first and classify then the local influence on Twitter: who have influenced you and who have been influenced by you. Until now, social structures of tweets’ original authors that have been either retweeted or marked as favourites are unobservable. Throughout this application, these structures can be discovered and they reveal the existence of communities formed by users of similar profile (that are connected among them) interrelated with other similar profile users’ communities. 相似文献
107.
Frédérique Rémy Thomas Flament Aurélie Michel Jacques Verron 《International journal of remote sensing》2014,35(14):5497-5512
From September 2002 to October 2010, the Envisat radar altimeter surveyed Greenland and Antarctica ice sheets on a 35 day repeat orbit, providing a unique data set for ice sheet mass balance studies. Up to 85 repeat cycles are available and the whole Envisat data set may be along-track processed in order to provide height variability and trend with a good spatial resolution for the objectives of ice sheet survey.Soon, a joint Centre National d’Etudes Spatiales/Indian Space Research Organisation mission, SARAL (Satellite with Argos and AltiKa), with the AltiKa payload on board, will be launched on exactly the same orbit (less than 1 km of the nomimal orbit in the across-track direction). This will allow an extension of previous European Remote Sensing (ERS) satellite, ERS-1 and ERS-2, and Envisat missions of the European Space Agency (ESA), in particular from the point of view of ice altimetry. However, AltiKa operates in the Ka band (36.8 GHz), a higher frequency than the classical Ku band (13.6 GHz), leading to important modifications and potential improvements in the interactions between radar wave and snow-pack.In this paper, a synthesis is presented of all available information relevant to ice altimetry scientific purposes as derived from the Envisat mission: mean and temporal derivatives of the height ? but also of the backscatter and of the two waveform parameters ? snow-pack change corrections, across-track surface slope at 1 km scale, etc. The spatial and temporal variability of ice sheet surface elevation is investigated with the help of the high-resolution Envisat along-track observations. We show that at least 50 repeat cycles are needed to reach the required accuracy for the elevation trend. It is thus advocated as potentially highly beneficial for SARAL/AltiKa as a follow-on mission. Moreover, the novel characteristics of SARAL/AltiKa are promising in improving our understanding of snow penetration impact. 相似文献
108.
Romain Fillières Bouchra Benjelloun-Mlayah Michel Delmas 《Journal of the American Oil Chemists' Society》1995,72(4):427-432
High-performance size-exclusion chromatography (HPSEC) was used to evaluate the influence of different variables affecting
the transesterification of rapeseed oil (RSO) with anhydrous ethanol and sodium ethoxide as catalyst. The effect of temperature,
ethanol/RSO molar ratio, catalyst concentration, and time can be interpreted by observing the variations of the reaction medium
composition. HPSEC has made the quantitation of ethyl esters, mono-, di-, and triglycerides and glycerol possible. The best
results for laboratory-scale reactions were obtained at 80°C with a 6:1 molar ratio of EtOH/RSO and 1% of NaOEt by weight
of RSO. 相似文献
109.
The diastereoselective hydrogenation catalyzed by heterogeneous metallic catalysts uses a covalently bound chiral auxiliary to induce the chirality. It remains an active synthetic methodology in the asymmetric synthesis of chiral products and may proceed with high diastereoselectivity. This review describes recent examples using this method, such as hydrogenation of C=C, C=O, and C=N bonds. The use of a chiral auxiliary group has also been successfully applied to the hydrogenation of aromatic and heteroaromatic rings. The choice of the chiral auxiliary was found to play a key role in the asymmetric hydrogenation. The results could be explained in terms of steric effect, with a preferred conformation of the adduct substrate and the addition occurring from the less bulky side. The catalytic metal, the support and the presence of additives were also found to have a significant influence. 相似文献
110.
Cecilia R. Lederhos Pablo C. L’Argentière Fernando Coloma-Pascual Nora S. Fígoli 《Catalysis Letters》2006,110(1-2):23-28
The 1-heptyne selective hydrogenation carried out at 150 kPa, and at 283 and 303 K using Ru/Al2O3 and Ru/C as catalysts, was studied. Catalysts were prepared by the incipient wetness impregnation technique using RuCl3 as precursor. Ru/Al2O3 was treated in hydrogen at 373 or 573 K and Ru/C only at the last temperature. Catalysts were characterized by hydrogen chemisorption,
TPR and XPS. Ru dispersion after treatment in hydrogen at the highest temperature is similar for both catalysts. Ru is present
as Ru0 in Ru/C, while Ru0 and Ru electron-deficient species are present on the catalysts surface after hydrogen treatment at the two temperatures using
Al2O3 as support. The best catalytic behavior was observed for the highest temperature of hydrogen treatment and for 303 K reaction
temperature. As a consequence of a shape selectivity effect of the C support, the best conversion is obtained with the alumina
supported catalyst. 相似文献