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991.
The effect of gas-liquid contacting conditions in a static mixer on ozone transfer efficiency and reduction of Bacillus subtilis spores was studied in an experimental ozone contactor. An empirical mathematical model was developed that related the transfer efficiency in the experimental system to the superficial liquid velocity in the mixer, the gas-liquid flow rate ratio and the height of the down-stream bubble column. Spore reduction was determined primarily by the dissolved ozone concentration-time (Cavgtm) product in the reactive flow segment and was independent of the gas-liquid contacting conditions in the static mixer. In an integrated ozone contacting system, the static mixer should be designed to maximize ozone mass transfer while the reactive flow segment should be designed for efficient microorganism reduction. 相似文献
992.
Summary
The copolymerization of allyl chloroacetate (ACAc) and N-propyl maleimide (PMI), catalyzed by Cu(I)Br or ferric(III) acetylacetonate
(Fe(acac)3) at 110°C, respectively, was studied through electron-impact mass spectrometry. Both Cu(I)Br and Fe(acac)3 catalyzed the copolymerization by an atom transfer process. However, the copolymerization of ACAc and PMI was not in an alternative
way, because propyl maleimide has high tendency to form homogeneous polymeric segments under the conditions of this work.
Received: 7 March 2002 /Revised: 20 June 2002/ Accepted: 1 July 2002 相似文献
993.
The active sites of ultra-dispersed Pt/-Al2O3 catalysts are studied using high-resolution electron microscopy, Z-contrast and dark field. In addition we have calculated using a method based in density functional theory the electrostatic potential and charge distribution of the active sites. It is conclude that the most likely Pt clusters that are formed correspond to Pt13 and Pt with icosahedral and decahedral structure. It is shown that this is consistent with the electron microscopy data. 相似文献
994.
Frédéric Destaillats Jean B. Jean-Denis Joseph Arul Robert L. Wolff Paul Angers 《Journal of the American Oil Chemists' Society》2002,79(11):1091-1094
GC analysis was performed to determine regiospecific distribution and FA composition in seed oils of the Aceraceae species,
Acer saccharum and A. saccharinum. The oil content in the seeds was low at 5.0% in A. saccharum and 5.8% in A. saccharinum, and the main FA were linoleic (30.8 and 29.4%), oleic (21.3 and 27.6%), palmitic (10.1 and 10.5%), and cis-vaccenic (9.4 and 7.9%) acids, respectively. In addition, both oils contained long-chain monoenes of the n−9 and n−7 groups,
including 11-eicosenoic, 13-docosenoic, 15-tetracosenoic, 13-eicosenoic, and 15-docosenoic acids, whereas γ-linolenic acid
accounted for 0.8% of total FA in A. saccharum, and 0.5% in A. saccharinum. Regiospecific analysis, performed using the methodology of dibutyroyl derivatives of MAG, indicated that linoleic, oleic,
and linolenic acids were mainly esterified at the internal position of TAG in both seed oils, whereas long-chain monoenes
of the n−7 group were almost exclusively esterified on the external positions. 相似文献
995.
R.B. Cantarutti R. Tarré R. Macedo G. Cadisch C. P. de Rezende J.M. Pereira J.M. Braga J.A. Gomide E. Ferreira B.J.R. Alves S. Urquiaga R.M. Boddey 《Nutrient Cycling in Agroecosystems》2002,64(3):257-271
It has been shown that with careful grazing management and addition of Pand K, but not N, fertilisers Brachiaria pastures are ableto maintain sustainable live weight gains over many years. However, standardon-farm practice, which generally involves high stocking rates, leads after afew years to pasture decline due mainly to N deficiency for grass regrowth. Togenerate an understanding of the mechanism of pasture decline and possiblemanagement options to mitigate this process, a study was performed in theAtlantic forest region of the south of Bahia state to study the N dynamics inpastures of Brachiaria humidicola subject to threedifferent stocking rates of beef cattle, with and without the presence of theforage legume Desmodium ovalifolium. Despite the fact thatthe C:N ratio of the deposited litter was high (60 to 70) the rate ofdecomposition was very rapid (k –0.07 gg–1 day–1) and annual rates of Nturnover through the litter pathway were between 105 and 170 kg Nha–1 year–1. In the grass-onlypasturesas stocking rate increased from 2 to 3 head ha–1, N recycledinthe litter decreased by 11%, but a further increase to 4 headha–1 decreased N recycling by 30% suggesting thatbeyonda certain critical level higher grazing stocking rates would lead to pasturedecline if there was no N addition. High stocking rates decreased theproportionof the legume in the sward, but at all rates the concentration of N in both thegreen and dead grass in the forage on offer and in the litter was higher in themixed sward. The presence of the legume caused a decrease in the C:N ratio ofthe microbial biomass while both soil N mineralisation and nitrificationincreased. This increased rate of turnover of the microbial biomass and thecontribution of N2 fixation to the legume resulted in largeincreasesin the N recycled via litter deposition ranging from 42 to 155 kg Nha–1 year–1. 相似文献
996.
Rana M. Tubaileh Antonio Garrido-Fernández M. Victoria Ruiz-Méndez Manuel León-Camacho Enrique Graciani-Constante 《Journal of the American Oil Chemists' Society》2002,79(1):101-104
Changes in the contents of waxes and fatty alcohols during deodorization/physical refining of bleached olive oil were studied.
Experiments were carried out with 1.85% acidity oil, which was physically refined in a discontinuous deodorizer of 250-kg
maximum capacity using nitrogen as stripping gas instead of steam. The variables studied were load and temperature of oil
in the deodorizer as well as N2 flow. Analyses of waxes and alcohols were carried out at different operation times. The maximum content of wax was always
observed when the oil reached the deodorization temperature. The variation in the wax content depended on temperature and
N2 flow. Wax decomposition started and continued during the operating time, and a progressive decrease, which was pronounced
between 3 and 4 h, was observed. Small changes in waxes were observed between 4 and 5 h. Total content of fatty alcohols diminished
throughout the operating time, and changes did not depend on the variables studied. 相似文献
997.
Wolff RL Lavialle O Pédrono F Pasquier E Destaillats F Marpeau AM Angers P Aitzetmüller K 《Lipids》2002,37(1):17-26
The seed fatty acid (FA) compositions of Abietoids (Abies, Cedrus, Hesperopeuce, Keteleeria, Pseudolarix, and Tsuga) are reviewed in the present study in conclusion to our survey of Pinaceae seed FA compositions. Many unpublished data are
given. Abietoids and Pinoids (Pinus, Larix, Ficea, and Pseudotsuga)—constituting the family Pinaceae—are united by the presence of several Δ5-olefinic acids, taxoleic (5,9–18∶2), pinolenic
(5,9,12–18∶3) coniferonic (5,9,12,15–18∶4), keteleeronic (5,11–20∶2), and sciadonic (5,11,14–20∶3) acids, and of 14-methyl
hexadecanoic (anteiso-17∶0) acid. These acids seldom occur in angiosperm seeds. The proportions of individual Δ5-olefinic
acids, however, differ between Pinoids and Abietoids. In the first group, pinolenic acid is much greater than taxoleic acid,
whereas in the second group, pinolenic acid is greater than or equal to taxoleic acid. Moreover, taxoleic acid in Abietoids
is much greater than taxoleic acid in Pinoids, an apparent limit between the two subfamilies being about 4.5% of that acid
relative to total FA. Tsuga spp. appear to be a major exception, as their seed FA compositions are much like those of species from the Pinoid group.
In this respect, Hesperopeuce mertensiana, also known as Tsuga mertensiana, has little in common with Abietoids and fits the general FA pattern of Pinoids well. Tsuga spp. and H. mertensiana, from their seed FA compositions, should perhaps be separated from the Abietoid group and their taxonomic position revised.
It is suggested that a “Tsugoid” subfamily be created, with seed FA in compliance with the Pinoid pattern and other botanical
and immunological criteria of the Abietoid type. All Pinaceae genera, with the exception of Pinus, are quite homogeneous when considering their overall seed FA compositions, including Δ5-olefinic acids. In all cases but
one (Pinus), variations from one species to another inside a given genus are of small amplitude. Pinus spp., on the other hand, have highly variable levels of Δ5-olefinic acids in their FA compositions, particularly when sections
(e.g., Cembroides vs. Pinus sections) or subsections (e.g., Flexiles and Cembrae subsections from the section Strobus) are compared, although they show qualitatively the same FA patterns characteristic of Pinoids. Multicomponent analysis of
Abietoid seed FA allowed grouping of individual species into genera that coincide with the same genera otherwise characterized
by more classical botanical criteria. Our studies exemplify how seed FA compositions, particularly owing to the presence of
Δ5-olefinic acids, may be useful in sustaining and adding some precision to existing taxonomy of the major family of gymnosperms,
Pinaceae. 相似文献
998.
Effect of Water on the Partial Oxidation of Propane to Acrylic and Acetic Acids on Mo-V-Sb-Nb Mixed Oxides 总被引:1,自引:0,他引:1
It is shown that the major effect of water in the oxidation of propane to acrylic and acetic acids on Mo1V0.3Sb0.25Nb0.08O
n
catalysts is to stabilise the active sites and increase the rates of formation of both acids. The usual effect of favoring desorption of the products is considered to be secondary. 相似文献
999.
Many lizards are capable of identifying food using only chemical cues from food surfaces, but almost nothing is known about the types of compounds that are effective stimuli. We experimentally studied lingual and biting responses by a lacertid lizard, Podarcis lilfordi, to single representatives of three major categories of food chemicals, sucrose as a carbohydrate, pure pork fat as a mixture of lipids, and bovine gamma globulin as a protein. In 60-sec trials in which stimuli were presented on cotton swabs, the lizards detected all three stimuli, exhibiting more tongue-flicks, licks, or bites, or a greater tongue-flick attack score (TFAS; overall measure of response strength to prey stimuli) than to deionized water. The initial response to all stimuli was tongue-flicking, but the lizards discriminated among the types of chemical stimuli. After preliminary tongue-flicks, the lizards responded to sucrose solutions by licking at high rates, to pure pork fat by biting, and to protein by a combination of additional tongue-flicks and biting. Biting is a feeding response to prey or solid plant material. Licking is a feeding response to sugars in nectar or ripe fruit. Its frequency increased with sucrose concentration. Our data suggest that lizards can identify several types of chemicals associated with food and direct feeding attempts to sources of such chemicals in the absence of visual cues. 相似文献
1000.
Exercise training-induced changes in sensitivity to endothelin-1 and aortic and cerebellum lipid profile in rats 总被引:2,自引:0,他引:2
Latorre E Morán M Aragonés MD Saborido A Fernández I Delgado J Catalán RE Megías A 《Lipids》2002,37(1):43-52
The purpose of this work was to study whether exercise training induces changes in the lipid profile of rat aorta and nervous
system and in the in vitro intrinsic responsiveness of these tissues to endothelin-1 (ET-1) treatment. The exercise program performed successfully produced
the characteristic metabolic alterations of the trained state. Exercise training induced a large and significant increase
in the levels of both aortic ethanolamine plasmalogens (PlasEtn) and glucosylceramides. In contrast, a decrease of aortic
ceramide and cholesterol levels was evoked by exercise training. ET-1 increased PlasEtn content only in sedentary animals.
An exercise-induced increase in cerebellum levels of ceramides and ceramide monohexosides was found. The cerebellum ceramide
content was increased by FT-1 more noticeably in sedentary rats than in trained animals. In contrast, cerebral cortex was
observed to be largely insensitive to both exercise training and ET-1 treatment. It was concluded that exercise training (i)
induces changes in both vascular and cerebellar lipid profiles, the former being much more pronounced than the latter, and
(ii) diminishes the aortic and cerebellar sensitivity to ET-1 action. 相似文献