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排序方式: 共有170条查询结果,搜索用时 15 毫秒
1.
Fereidoon Moghadas Nejad Hossein Nazari Fariba Karimiyan Khosroshahi Mostafa Hatefi Oskuei 《Petroleum Science and Technology》2017,35(7):641-646
There is a paucity of knowledge regarding the effect of nanoparticles on the performance of asphalt binder against fatigue and low-temperature cracking. In this research, asphalt binders were modified using SiO2, TiO2, and CaCO3 nanoparticles, and rheological and thermal properties of the modified binders were investigated. Differential scanning calorimetry was used to determine glass transition temperature, and rheological properties at low and intermediate temperatures were determined using bending beam and dynamic shear rheometers, respectively. The results suggested that the addition of these nanoparticles increases glass transition temperature and the low-temperature stiffness of asphalt binder. Furthermore, increase in complex shear modulus and decrease in phase angle values were observed at intermediate temperatures. It can be concluded that inferior performance at low and intermediate temperature is expected by the addition of nanoparticles to asphalt binder. 相似文献
2.
Neel Chandrasekara Fereidoon Shahidi 《Journal of the American Oil Chemists' Society》2011,88(8):1197-1202
Cashew nut oils, extracted from raw and roasted whole cashew nuts, were examined for their fatty acid composition, color change
and oxidative stability. Fatty acids were analyzed using gas chromatography, and a spectrophotometric method was used to determine
the color changes of the resultant oils. Oxidative stability was determined under accelerated oxidation conditions by employing
conjugated diene (CD) and thiobarbituric acid reactive substances (TBARS) assays. The contents of monounsaturated (MUFA),
polyunsaturated (PUFA) and saturated (SAFA) fatty acids were 61, 17 and 21%, respectively. Oleic acid was the major MUFA whereas
linoleic acid was the main PUFA present in cashew nut oils. Oxidative stability of the oil as determined by CD values after
72 h of storage under Schall oven condition at 60 °C was 1.08 and 0.65 for the raw and high temperature roasted cashew nut,
respectively. The TBARS values, expressed as malondialdehyde equivalents decreased with increasing roasting temperature. Thus
roasting of whole cashew nuts improved the oxidative stability of the resultant nut oils. 相似文献
3.
Edward Durnoford Fereidoon Shahidi 《Journal of the American Oil Chemists' Society》2002,79(11):1095-1102
The FA composition of selected tissues of all six species of eastern Canadian phocid seals: bearded seal (Erignathus barbatus), gray seal (Halichoerus grypus), harbor seal (Phoca vitulina), harp seal (P. groenlandica), hooded seal (Cystophora cristata), and ringed seal (P. hispida) was determined to detect possible differences among different tissues and species. A univariate approach was used to examine
differences among different tissues and species separately, and a multivariate approach was taken in examining differences
among different species and tissues simultaneously. Findings indicated that FA composition depended on both tissue and species
of seal. However, differences were most apparent among tissues. Several unique features of the FA compositions were identified.
Blubber was found to be high in the monounsaturated FA, but low in arachidonic acid and dimethyl acetals. Brain tissue lipids,
on the other hand, were high in dimethyl acetals and DHA. Lung tissue lipids were very high in palmitic acid, and heart tissue
lipids had a higher content of linoleic acid than did lipids of other tissues examined. Thus, the proportions of FA constituents
in different tissues were different, most probably due to their varying functional requirements. 相似文献
4.
Stereospecific analysis was carried out to establish positional distribution of FA in the TAG of DHA, EPA, and (EPA+DHA)-enriched
oils. In this study, TAG of enzymatically modified oils were purified using a silicic acid column. The TAG were then subjected
to positional distribution analysis using a modified procedure involving reductive cleavage with Grignard reagent. The results
showed that in DHA-enriched borage oil (BO), DHA was randomly distributed over the three positions of TAG, whereas γ-linolenic
acid (GLA) was mainly esterified at the sn-2 and-3 positions. In DHA-enriched evening primrose oil (EPO), however, DHA and GLA were concentrated in the sn-2 position. In EPA-enriched BO, EPA was randomly distributed over the three positions of TAG, similar to that observed for
DHA. In EPA-enriched EPO, however, this FA was mainly located at the primary positions (sn-1 and sn-3) of TAG. In both oils, GLA was preferentially esterified at the sn-2 position. In (EPA+DHA)-enriched BO, EPA and DHA were mainly esterified at the sn-1 and -3 positions of TAG, whereas GLA was mainly located at the sn-2 position. In (EPA+DHA)-enriched EPO, GLA was mainly located at the sn-2 and-3 positions; EPA was preferentially esterified at the sn-1 and-3 positions, and DHA was found mainly at the sn-3 position. 相似文献
5.
S.?P.?J.?Namal Senanayake Fereidoon?ShahidiEmail author 《Journal of the American Oil Chemists' Society》2002,79(10):1003-1013
This study utilized γ-linolenic acid (18∶3n−6; GLA)-rich borage oil (BO) and evening primrose oil (EPO) for the synthesis
of structured lipids (SL) and compared the oxidative stability of the products with those of unmodified BO and EPO as controls.
Immobilized Novozym 435 lipase from Candida antarctica was used as the biocatalyst for SL production. BO or EPO eas enzymatically modified with docosahexaenoic acid (22∶6n−3; DHA),
as the acyl donor, to produce SI. The SI were characterized and their oxidative stabilities evaluated. Among the oils examined,
SL gave rise to higher quantities (P≤0.05) of conjugated dienes, TBARS, and headspace volatiles as compared to their unmodified counterparts. Results indicated
that modified oils were less stable than their unmodified counterparts. The double bond index (DBI) and methylene bridge index
(MBI) of oils decreased (P<0.05) during oxidation in the more unsaturated oils. An attempt was made to correlate various parameters of oxidation with
DBI and MBI of oils; correlation coefficients (−r) were within the range of 0.574–0.973. This suggests that indicators such as DBI and MBI can reflect oxidative stability
of oils. 相似文献
6.
Sharon A. Spurvey S. P. J. Namal Senanayake Fereidoon Shahidi 《Journal of the American Oil Chemists' Society》2001,78(11):1105-1112
Oils containing both n−3 and n−6 fatty acids have important clinical and nutritional applications. Lipase-catalyzed acidolysis
of seal blubber (SBO) and menhaden oils (MO) with γ-linolenic acid (GLA) was carried out in hexane. The process variables
studied for lipase-catalyzed reaction were concentration of enzyme (100–700 units/g of oil), reaction temperature (30–60°C),
reaction time (0–48 h), and mole ratio of GLA to triacylglycerols (TAG) (1∶1 to 5∶1). Two lipases chosen for acidolysis reaction
were from Pseudomonas species (PS-30) and Mucor miehei. Lipase PS-30 was chosen over Mucor (also known as Rhizomucor) miehei to catalyze the acidolysis reaction owing to higher incorporation of GLA. For the acidolysis reaction, optimal conditions
were a 3∶1 mole ratio of GLA to TAG, reaction temperature of 40°C, reaction time of 24 h, and an enzyme concentration of 500
units/g of oil. Under these conditions, incorporation of GLA was 37.1% for SBO and 39.6% for MO. 相似文献
7.
Effect of nanoparticles on the morphology and thermal properties of self-healing poly(urea-formaldehyde) microcapsules 总被引:2,自引:0,他引:2
The preparation of microcapsules with adequate performance is required for the fabrication of self-healing composites. Self-healing microcapsules with improved morphology as well as thermal and water resistance were prepared by introducing either single-walled carbon nanotubes (SWCNTs) or aluminum oxide nanoparticles (nano-alumina) into a urea–formaldehyde resin (which acts as the wall material). The prepared microcapsules were studied using various characterization techniques, including Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), optical microscopy (OM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and contact-angle measurements. Based on comparisons with traditional poly(urea–formaldehyde) microcapsules, the modified microcapsules exhibited a smoother surface. Our results indicate that the presence of the nanoparticles did not affect the core content of the microcapsules, which was approximately 78 wt.%. The average size of the traditional microcapsules was reduced from 168 μm to 115 and 95 μm for the SWCNT- and nano-alumina-modified microcapsules, respectively. In addition, the thermal resistance of the microcapsules was improved after modifying the capsule walls. After the microcapsules had been modified with SWCNTs, the water resistance of the capsules improved, and the contact angle increased from 44° to 50°. 相似文献
8.
Fayez?Hamam Fereidoon?ShahidiEmail author 《Journal of the American Oil Chemists' Society》2005,82(10):731-736
The lipase-assisted acidolysis of high-laurate canola oil (HLCO; Laurical 25) with long-chain n−3 FA (DHA and EPA) was studied.
Response surface methodology was used to obtain a maximal incorporation of DHA or EPA into HLCO. The studied process variables
were the amount of enzyme (2–6%), reaction temperature (35–55°C), and incubation time (12–36 h). The amount of water added
and the mole ratio of substrates (oil to DHA or EPA) were kept at 2% and 1∶3, respectively. All experiments were conducted
according to a face-centered cube design. Under optimal conditions (4.79% of enzyme; 46.1°C; 30.1 h), the incorporation of
DHA into HLCO was 37.3%. The corresponding maximal incorporation of EPA (61.6%) into Laurical 25 was obtained using 4.6% enzyme,
a reaction temperature of 39.9°C, and a reaction period of 26.2 h. Examination of the positional distribution of FA on the
glycerol backbone of modified HLCO with DHA showed that the DHA was primarily located in the sn-1,3 positions of the TAG molecules. However, lauric acid also remained mainly in the sn-1,3 positions of the modified oil. For EPA-modified Laurical 25, lauric acid was present mainly in the sn-1,3 positions, whereas EPA was randomly distributed over the three positions. 相似文献
9.
Crude catechins extract from Chinese green tea were fractionated using Sephadex LH‐20 column chromatography. The fraction containing (–)‐epigallocatechin‐3‐gallate (EGCG) was then subjected to a semipreparative high‐performance liquid chromatography (HPLC). Using a mobile phase of water : dimethyl formamide : methanol : acetic acid (157 : 49 : 2 : 1 v/v/v/v( the mixture of two methylated catechins was separated and isolated. According to mass spectrometry (MS) and nuclear magnetic resonance (1H‐NMR) date, these compounds were identified as (–)‐epigallocatechin‐3‐(3‐O‐methylgallate) and (–)‐epigallocatechin‐3‐(4‐O‐methylgallate). 相似文献
10.
Udaya N. Wanasundara Ryszard Amarowicz Fereidoon Shahidi 《Food research international (Ottawa, Ont.)》1995,28(6):525-530
Defatted canola meal was extracted with 95% (v/v) ethanol at 80 °C. The extract was fractionated on a Sephadex LH-20 column using methanol as eluate. Seven major fractions were isolated according to UV absorption, content of phenolics and sugars. Antioxidant activity of these fractions was evaluated in a β-carotenelinoleate model system. Fraction IV showed the best antioxidant effect by exhibiting the highest preventive activity against the bleaching of β-carotene. Further separation of this fraction on TLC indicated that it contains several compounds including phenolic acids and trihydroxy phenolic compounds such as flavones and flavonols. 相似文献