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排序方式: 共有693条查询结果,搜索用时 11 毫秒
71.
LM O''Rourke R Tooze M Turner DM Sandoval RH Carter VL Tybulewicz DT Fearon 《Canadian Metallurgical Quarterly》1998,8(5):635-645
Germ cells are distinct from somatic cells in their immortality, totipotency, and ability to undergo meiosis. Candidates for components that guide the unique germline program are the distinctive granules observed in germ cells of many species. We show that a component of germ granules is essential for fertility in C. elegans and that its primary function is in germline proliferation. This role has been revealed by molecular and genetic analyses of pgl-1. PGL-1 is a predicted RNA-binding protein that is present on germ granules at all stages of development. Elimination of PGL-1 results in defective germ granules and sterility. Interestingly, PGL-1 function is required for fertility only at elevated temperatures, suggesting that germline development is inherently sensitive to temperature. 相似文献
72.
Mario Cueto Abel Farroni Silvio D. Rodríguez Regine Schoenlechner Gerhard Schleining María del Pilar Buera 《Food and Bioprocess Technology》2018,11(8):1586-1595
Spectral analysis employing multivariate techniques was employed to differentiate plain maize flours from formulations containing maize with added milled chia or quinoa seeds for producing cereal breakfast extrudates. The physicochemical changes of the enriched formulations due to processing stages and formulation were evaluated by using FTIR and chemometric analysis, which allowed a rapid and non-destructive discrimination between sample processing and compositional aspects. Specific IR frequencies were selected which provided highest sample discrimination. Selected IR absorbance relationships at those specific wavenumbers were useful to track changes promoted by extrusion for carbohydrates, proteins, and lipids. The complexes between amylose and lipids, that takes place during extrusion, underwent distinctive changes as confirmed by XRD. The crystallinity loss, after extrusion (with an average value of 50%), shows evidence of amylose-lipid complexes formation of type Eh and Vh. Correlations between the textural behavior, composition, and selected FTIR indices were obtained. 相似文献
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74.
This paper describes studies of surface modification of a natural Chilean zeolite with cetyl trimethylammonium bromide (CTAB), to investigate the adsorption efficiency for the removal from aqueous solution of an anionic surfactant, sodium dodecyl benzene sulfonate (SDBS), at bench scale. Modification of the zeolite with CTAB (named ZMS) was based on the external cation exchange capacity (ECEC) of 0.11 meq g?1. The medium pH influences the SDBS ions adsorption rate onto ZMS and the adsorption followed the pseudo-second-order kinetic model. Equilibrium data showed excellent correlation with the Langmuir isotherm model. The adsorption capacities depended on maximum uptakes followed the CTAB concentration or coverage ranging from 40% to 660% of the ECEC. The maximum adsorption capacity of 30.7 mg SDBS g?1 was obtained at 660% of ECEC value. These data contribute for the understanding of mechanisms involved in zeolite modification and provide same practical clues to improve the adsorption efficiency (uptake capacity) of anionic surfactants. Results were discussed in terms of interfacial and solution chemistry phenomena. 相似文献
75.
The preparation, characterization, and adsorption properties of Mn2+ by manganese oxide coated zeolite (MOCZ) and its ability in removing Mn2+ by adsorption were investigated. Characterization analyses were used to monitor the surface properties (and their changes) of the coated layer and metal adsorption sites on the surface of MOCZ. The adsorption experiments were carried out as a function of solution pH, adsorbent concentration and contact time. Binding of Mn2+ ions onto MOCZ was highly pH dependent with an increase in the extent of adsorption with the pH of the media investigated. After the Mn2+ adsorption by MOCZ, the medium pH decreased and enhanced with increasing adsorbent concentration. The pseudo-second-order model fitted better among all the kinetic models suggesting that the adsorption mechanism might be a chemisorption process. The equilibrium data showed excellent correlation for both Langmuir and Freundlich isotherm model and this implies both monolayer adsorption and a heterogeneous surface existence in MOCZ. At pH = 6, the Mn2+ uptake by MOCZ attained as high as 1.1 meq Mn2+ g?1 at equilibrium. The results suggested that MOCZ presents a fairly good potential as an adsorbent for an efficient removal of Mn2+ ions from aqueous solution. 相似文献
76.
AbstractThis review concerns three legume trees (family Fabaceae, subfamily Caesalpinioideae) from West Africa, namely Detarium microcarpum, Parkia biglobosa and Dialium guineense, and illustrates their nutritional value and therapeutic properties. These species are an important source of nutrition for West African populations, but their agricultural exploitation is still incomplete. The survey was conducted on Scopus, Web of Science, and Medline, using scientific and common English names of the species as keywords and then selecting papers related to nutritional and medicinal properties. Main food products are fruit pulp and seeds, though leaves can also be used. Most relevant dietary features are high protein, vitamin, and micronutrient contents. Various therapeutic and nutritional benefits of these plants have been documented by ethnobotanical and experimental studies, stimulating an interest for their possible use as functional food or drug sources. Most studied medicinal properties include antidiabetic and antimicrobial activities of D. microcarpum, cardiovascular protective and antidiabetic activities of P. biglobosa, and bilharzia-preventing molluscicidal activity of D. guineense. Phytochemical characterizations have revealed potential sources of active drugs, such as D. guineense saponins and D. microcarpum diterpenes. Scientific results support popular uses of these legume trees, indicating a prominent nutritional and health value. 相似文献
77.
78.
The fluxes of linear alkylbenzenesulphonates (LAS), nonylphenol (NP), nonylphenol monoethoxylate (NP1EO) and nonylphenol diethoxylate (NP2EO) through sewage and sludge treatment of 29 Swiss sewage treatment plants were investigated. Reversed-phase high-performance liquid chromatography (HPLC) was used to determine LAS. Normal-phase HPLC was employed to measure NP, NP1EO and NP2EO which are metabolites of the nonionic surfactants of the nonylphenol polyethoxylate type (NPnEO). Quantitative determinations were performed of raw sewage, primary and secondary effluents and of sewage sludge. Under normal conditions of sewage and sludge treatment, LAS were efficiently removed from the raw wastewater (> 99% w/w) and were partly transferred to the sewage sludge (15–20% w/w). About 50% (molar base) of NPnEO in the sewage were transformed to NP and accumulated in the digested sludge. Large variations existed among different sewage treatment plants. It was estimated that 1.0 g m−2 y−1 of LAS and 0.3 g m−2 y−1 of NP are applied with sewage sludge to Swiss soils. 相似文献
79.