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排序方式: 共有327条查询结果,搜索用时 31 毫秒
51.
José Antonio Cayuela Mirela Rada María del Carmen Pérez‐Camino Mohamed Benaissa Elamrani Abdelaziz Ángeles Guinda 《European Journal of Lipid Science and Technology》2008,110(12):1159-1166
The present study was conducted to know the possible influence of the seed treatment, method of extraction and geographical origin on the quality and chemical composition of argan oil. Artisanally and semiautomatically extracted argan oils, from roasted and unroasted seeds, from interior and coast areas, were studied. The quality parameters analyzed were acid value, peroxide value, K232 and K270, triacylglycerols and fatty acid composition, polar compounds, total phenols, tocopherol content and oil stability index (OSI). Seed treatment and extraction method showed a higher influence on quality parameters than geographical area; the quality parameters of the different oils were discussed. The total phenolic content in all analyzed samples was lower than 10 ppm. γ‐Tocopherol was the major tocopherol (84.4–86.4%) with a high contribution to the total tocopherol content (383–485 ppm). The OSI of the argan oil samples were well correlated (R = 0.97) with the tocopherol contents. The argan oil samples obtained from roasted seeds presented higher stability (26–38 h) than the oils from unroasted seeds (16–32 h). 相似文献
52.
Matić M Jurić S Denegri B Kronja O 《International journal of molecular sciences》2012,13(2):2012-2024
Fine effects that influence the variations of the reaction constants s(f) in LFER log k = s(f)(N(f) + E(f)) have been summarized here. Increasing solvent polarity in the series of binary mixtures increases the solvolysis rates for the same factor for all benzhydryl derivatives in which the solvation of the leaving group moiety in the transition state is substantial, i.e., log k vs. E(f) correlation lines are parallel (same s(f)). For the substrates in which the demand for solvation of the leaving groups moiety is reduced, (e.g., carbonates) s(f) parameters decrease as the fraction of the water in a given solvent/water mixture increases (log k vs. E(f) plots converge), due to decreasing solvation of the electrofuge moiety toward bigger electrofugality. The abscissa of the intersection of the converging plots might indicate the critical electrofugality above which the solvolysis rates should not depend of the water fraction. Larger reaction constant s(f) indicate later transition state for structurally related substrates only, while s(f) parameters for structurally different substrates cannot be compared likely due to different intrinsic barriers. Inversion in relative abilities of leaving groups is possible if they have similar reactivities and are characterized with different reaction constants. 相似文献
53.
Eladio J. Rivera Richa Sethi Feifei Qu Ramkumar Krishnamurthy Raja Muthupillai Michael Alford Michael A. Swanson Sandra S. Eaton Gareth R. Eaton Lon J. Wilson 《Advanced functional materials》2012,22(17):3691-3698
The encapsulation of nitroxide radicals within ultrashort (ca. 50 nm) single‐walled carbon nanotubes (US‐tubes) is achieved. Tempo‐ and Iodo‐Tempo@US‐tubes are characterized by thermogravimetric analysis (TGA), X‐ray photoelectron spectroscopy (XPS), and Raman spectroscopy. Electron paramagnetic resonance (EPR) spectra display characteristic signals due to the detection of the spin probes within the US‐tubes. Longitudinal proton relaxivities (r1) of both nitroxide@US‐tubes samples are 7 to 13 times greater than the free nitroxide radicals in solution, giving relaxivities comparable to the clinical contrast agent (CA) Magnevist. In addition, transverse proton relaxivities (r2) show unprecedented proton relaxation enhancement in comparison to any other reported nitroxide radical‐based system or the clinically approved T2 CA, Resovist, under the same conditions. T2‐weighted magnetic resonance imaging (MRI) phantom images show that the encapsulation of nitroxide radicals within the US‐tubes produces good contrast enhancement due to their high r2 relaxivities. The nitroxide radicals@US‐tube agents are a new promising class of spin probes for MRI and electronic paramagnetic resonance imaging (EPRI) labeling, tracking, and diagnosis. 相似文献
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This study describes the effects of the addition of inorganic nanosized UV absorbers on physico-mechanical and thermal properties of an exterior commercial acrylic-based waterborne stain for wood. Electronic microscopy and water vapor (WV) permeability measurements were performed to characterize the free films of the acrylic stain and resulting nanocomposite coatings. An accelerated weathering method was used to evaluate aging behavior of the coatings on wood through appearance, Tg, abrasion resistance, adhesion strength, hardness and Young's modulus changes. In addition to improving the protection against UV, the doped TiO2 and silica-coated ZnO nanoparticles in powder form have improved the abrasion resistance and barrier effect against water vapor diffusion of the acrylic stain. For most of nanocomposite coatings, the addition of ZnO hydrophilic nanoparticles in predispersed form has resulted in a decrease in WV permeability, while the adhesion strength and abrasion resistance of those coatings were negatively affected. The addition of ZnO nanoparticles has decreased the Tg of the acrylic stain. Finally, the accelerated weathering has induced an increase in Tg, hardness, Young's modulus (stiffness) and an increase in apparent adhesion strength and abrasion resistance of the coatings. The Tg values of the aged nanocomposite coatings were lower than that of unmodified acrylic stain. 相似文献
57.
A. de Pablos‐Martín D. Ristic S. Bhattacharyya Th. Höche G.C. Mather M. O Ramírez S. Soria M. Ferrari G.C. Righini L.E. Bausá A. Durán M.J. Pascual 《Journal of the American Ceramic Society》2013,96(2):447-457
The influence of the addition of 1 mol% Tm2O3 on the nanocrystallization of LaF3 in a glass of composition 55SiO2–20Al2O3–15Na2O–10LaF3 (mol%) has been studied. Tm2O3 affects the phase separation in the glass and delays the onset of crystallization with respect to the undoped glass. Additionally, the maximum LaF3 crystal size is slightly greater than that in the undoped glass–ceramics. The microstructural and compositional changes in the glass matrix have been studied using several techniques, including viscosity, dilatometry, X‐ray and neutron diffraction (XRD, ND), quantitative Rietveld refinement, transmission electron microscopy (TEM), differential scanning calorimetry (DSC), and Raman spectroscopy. Photoluminescence measurements indicate that the Tm3+ ions are distributed between the glassy matrix and LaF3 crystals. Eu2O3 has been used as structure probe and part of the Eu3+ ions are reduced to Eu2+ when incorporated in the LaF3 nano‐crystals. Up‐conversion spectra under IR‐excitation show a higher intensity of the blue emission in the Tm‐doped glass–ceramic compared with that in the glass. 相似文献
58.
提出了气动乳化液自动配比仪的构想,该配比仪以井下压风为动力,利用综合控制器(PLC)作为控制单元,实现乳化液浓度的自动配比。其配液方式可分为自动调节和人工调节两种。该装置不仅能够更好地实现乳化液的全封闭式管理,保持乳化液系统的清洁,降低液压支架液压元件的损坏,也大大减少了乳化油的浪费。 相似文献
59.
Rodica Balasa Smaranda Maier Adina Hutanu Septimiu Voidazan Sebastian Andone Mirela Oiaga Doina Manu 《International journal of molecular sciences》2022,23(18)
Cladribine (CLD) treats multiple sclerosis (MS) by selectively and transiently depleting B and T cells with a secondary long-term reconstruction of the immune system. This study provides evidence of CLD’s immunomodulatory role in peripheral blood mononuclear cells (PBMCs) harvested from 40 patients with untreated relapsing-remitting MS (RRMS) exposed to CLD. We quantified cytokine secretion from PBMCs isolated by density gradient centrifugation with Ficoll–Paque using xMAP technology on a FlexMap 3D analyzer with a highly sensitive multiplex immunoassay kit. The PBMC secretory profile was evaluated with and without CLD exposure. PBMCs isolated from patients with RRMS for ≤12 months had significantly higher IL-4 but significantly lower IFN-γ and TNF-α secretion after CLD exposure. PBMCs isolated from patients with RRMS for >12 months had altered inflammatory ratios toward an anti-inflammatory profile and increased IL-4 but decreased TNF-α secretion after CLD exposure. CLD induced nonsignificant changes in IL-17 secretion in both RRMS groups. Our findings reaffirm CLD’s immunomodulatory effect that induces an anti-inflammatory phenotype. 相似文献
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