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排序方式: 共有749条查询结果,搜索用时 15 毫秒
31.
Marília Brykalski Fernando Machado Machado Rubens Camaratta Alice Gonçalves Osório Leandro Lemos Silveira Carlos Perez Bergmann Matthew Ayorinde Adebayo 《International Journal of Applied Ceramic Technology》2023,20(6):3576-3583
A glass foam (GF) of high specific compressive strength (12.17±1.91 MPa g−1 cm−3) and low thermal conductivity (.121±.001 Wm−1 K−1) was produced from waste glass of photovoltaic module, eggshells, and bentonite clay. The influences of the amount of clay and heat-treatment temperature on the GFs final properties were assessed. X-ray diffraction results and the data of microscopic analyses demonstrated that addition of clay affected the structure and porosity of the GFs, and consequently their mechanical properties. On the basis of the mechanical property (density), the GF that composed of 80% waste glass, 10% clay, and 10% eggshell at the sintering temperature of 900°C was the best. The GFs reported in this study could serve as promising insulators in situations where high load support is required. 相似文献
32.
Vera Samburova Mark S. Lemos Sage Hiibel S. Kent Hoekman John C. Cushman Barbara Zielinska 《Journal of the American Oil Chemists' Society》2013,90(1):53-64
To assess the suitability of microalgal strains for biodiesel production the lipid content and composition, especially individual triacylglycerols (TAG) and free fatty acids (FFA) must be determined. In this study, the compositions and concentrations of TAG and FFA were analysed in four halophytic algal species, Dunaliella salina, D. tertiolecta, D. bardawil, and D. granulata. These species were selected as part of a larger screen to identify species suitable for biofuel feedstocks. An accelerated solvent extraction instrument was used for lipids and fatty acid extraction using a dichloromethane–hexane solvent system. Ultra-performance liquid chromatography coupled with mass spectrometry (MS) detection was optimized and applied to the quantitative analysis of TAG and FFA in the different algal extracts. Individual TAG were characterized structurally using direct electrospray ionization (ESI) MS and MS/MS techniques. Cationic adducts (NH4 +) of TAG were detected and quantified in the positive ESI MS and MS/MS modes, while the negative ESI mode was used for FFA analysis. Over 20 TAG were identified and quantified in the four Dunaliella strains. Analysis of FFA compositions demonstrated that the most abundant FFA in these four algal species were palmitic, linolenic, linoleic, and oleic acids. 相似文献
33.
Isabelle Sioen Krishna Vyncke Mieke De Maeyer Monique Gerichhausen Stefaan De Henauw 《Lipids》2013,48(7):729-738
Advances in our knowledge of the physiological functions of dietary polyunsaturated fatty acids (PUFAs) have led to an increased interest in food sources and the level of dietary intake of these nutrients. Up to now, no representative data was available for the Belgian adult population. This study aimed to describe data on the intake and food sources of total and individual omega-6 and omega-3 PUFA for the Belgian population over 15 years old. PUFA intakes were assessed for 3,043 Belgian adults, based on two non-consecutive 24 h recalls. Usual intakes were calculated using the multiple source method. The results showed that the intake of linoleic acid (LA) is in accordance with the recommendation for almost all Belgian adults. However, the intake of omega-3 PUFA is suboptimal for a large part of the studied population and also the intake of total PUFA should be increased for a part of the population. The main food source of LA and α-linolenic acid (ALA) was the group of fats and oils (60.6 % for LA and 53.1 % for ALA). Fish and fish products were the most important sources of long chain omega-3 PUFA. Age influenced fatty acids intake, with higher intake of omega-3 PUFA in the older age groups. To fill the gap between the intake and recommendation of total PUFA, and in particular omega-3 PUFA, sustainable strategies and efficient consumer communication strategies will be needed. 相似文献
34.
The preparation of 2,4,6,8-tetramethylcyclotetrasiloxane () miniemulsions stabilized by commercial surfactants, i.e. sodium dodecylbenzenesulfonate (NaDBSA) and sodium laurate/lauric acid mixture, was studied and is first reported. Then, the pH was tuned in order to process polymerization through interfacial protonic initiation. With lauric acid, no polymerization was observed, even at high temperature or large acid contents. Such effect is ascribed to the poor dissociation and reactivity of high pKa's carboxylic acids. With NaDBSA, acidification by HCl was enough to initiate the polymerization, but the pH of the continuous phase was shown to have a strong effect on the polymerization process. Optimal conditions (at pH 5) gave chains with average number molar masses around 16,000 g mol−1 and polydispersity index close to 1.6, for a total conversion in polymer of about 60% after 2 h reaction. Lower pH (4.2) quickly led to a cross-linked network whereas at higher pH (6.1), conversions were too slow (around 10% after 350 min). 相似文献
35.
Single-wall carbon nanotubes (SWNTs) prepared by the arc discharge method were oxidized using nitric acid. The samples were analyzed by using Raman scattering and Fourier transformed infrared spectroscopy (FTIR). The FTIR results indicate the presence of -COOH acid groups in the treated samples. The up shifts observed in the radial breathing mode frequencies suggest that SWNTs behave as donors after the acid treatment, with charge transfer occurring from the nanotubes to the -COOH groups. Ab initio calculations of SWNTs interacting with -COOH acid groups support the charge transfer process from the nanotubes to the carboxyl groups. 相似文献
36.
Patrícia Neves Sandra Gago Cláudia C. L. Pereira Sónia Figueiredo Américo Lemos André D. Lopes Isabel S. Gonçalves Martyn Pillinger Carlos M. Silva Anabela A. Valente 《Catalysis Letters》2009,132(1-2):94-103
A dioxomolybdenum(vi) complex bearing a tetradentate anionic N,O oxazoline ligand with four stereocenters has been studied as a catalyst in the liquid-phase epoxidation of 17 different aliphatic and aromatic olefins (including prochiral, racemate or pure enantiomers) using tert-butyl hydroperoxide as the oxidant. Epoxide selectivities of up to 100% and variable epoxide yields (3–100% within 24 h) were obtained. Although the complex generally exhibited low or no chiral induction ability, diastereoselectivity was significant in some cases (in the reaction of limonene, for example). Kinetic studies and recycling tests with the substrates cis-cyclooctene and trans-β-methylstyrene showed that the catalyst is stable and reusable, and recycling is facilitated by immobilization of the complex in a room temperature ionic liquid. Preliminary results show that the complex may have a broad substrate scope, not only for olefin epoxidation, but also for the dehydrogenation of alcohols to carbonyl compounds and the sulfoxidation of sulfides to sulfoxides. 相似文献
37.
Monique van Scherpenzeel Ed E. Moret Dr. Lluis Ballell Dr. Rob M. J. Liskamp Prof. Dr. Ulf J. Nilsson Dr. Hakon Leffler Dr. Roland J. Pieters Dr. 《Chembiochem : a European journal of chemical biology》2009,10(10):1724-1733
Light up galectin: Photoprobes based on thiodigalactoside were prepared for galectin‐3, a lectin linked to cancer. The probes contained either benzophenone or acetophenone moieties as the photolabel for covalent attachment to the protein. One particular probe labeled galectin‐3 selectively, even in the presence of cell lysate.
38.
Alessandri JM Extier A Langelier B Perruchot MH Heberden C Guesnet P Lavialle M 《Lipids》2008,43(1):19-28
Whether neurosteroids regulate the synthesis of long chain polyunsaturated fatty acids in brain cells is unknown. We examined
the influence of 17-β-estradiol (E2) on the capacity of SH-SY5Y cells supplemented with α-linolenic acid (ALA), to produce
eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA) and docosahexaenoic acid (DHA). Cells were incubated for 24 or 72 h
with ALA added alone or in combination with E2 (ALA + E2). Fatty acids were analyzed by gas chromatography of ethanolamine
glycerophospholipids (EtnGpl) and phosphatidylcholine (PtdCho). Incubation for 24 h with ALA alone increased EPA and DPA in
EtnGpl, by 330 and 430% compared to controls (P < 0.001) and DHA by only 10% (P < 0.05). Although DHA increased by 30% (P < 0.001) in ALA + E2-treated cells, the difference between the ALA and ALA + E2 treatments were not significant after 24 h
(Anova-1, Fisher’s test). After 72 h, EPA, DPA and DHA further increased in EtnGpl and PtdCho of cells supplemented with ALA
or ALA + E2. Incubation for 72 h with ALA + E2 specifically increased EPA (+34% in EtnGpl, P < 0.001) and DPA (+15%, P < 0.001) compared to ALA alone. Thus, SH-SY5Y cells produced membrane EPA, DPA and DHA from supplemental ALA. The formation
of DHA was limited, even in the presence of E2. E2 significantly favored EPA and DPA production in cells grown for 72 h. Enhanced
synthesis of ALA-elongation products in neuroblastoma cells treated with E2 supports the hypothesis that neurosteroids could
modulate the metabolism of PUFA. 相似文献
39.
Luccas M. Barata Eloísa H. Andrade Alessandra R. Ramos Oriel F. de Lemos William N. Setzer Kendall G. Byler Jos Guilherme S. Maia Joyce Kelly R. da Silva 《International journal of molecular sciences》2021,22(2)
This study evaluated the chemical compositions of the leaves and fruits of eight black pepper cultivars cultivated in Pará State (Amazon, Brazil). Hydrodistillation and gas chromatography–mass spectrometry were employed to extract and analyze the volatile compounds, respectively. Sesquiterpene hydrocarbons were predominant (58.5–90.9%) in the cultivars “Cingapura”, “Equador”, “Guajarina”, “Iaçará”, and “Kottanadan”, and “Bragantina”, “Clonada”, and “Uthirankota” displayed oxygenated sesquiterpenoids (50.6–75.0%). The multivariate statistical analysis applied using volatile composition grouped the samples into four groups: γ-Elemene, curzerene, and δ-elemene (“Equador”/“Guajarina”, I); δ-elemene (“Iaçará”/“Kottanadan”/“Cingapura”, II); elemol (“Clonada”/“Uthirankota”, III) and α-muurolol, bicyclogermacrene, and cubebol (“Bragantina”, IV). The major compounds in all fruit samples were monoterpene hydrocarbons such as α-pinene, β-pinene, and limonene. Among the cultivar leaves, phenolics content (44.75–140.53 mg GAE·g−1 FW), the enzymatic activity of phenylalanine-ammonia lyase (20.19–57.22 µU·mL−1), and carotenoids (0.21–2.31 µg·mL−1) displayed significant variations. Due to black pepper’s susceptibility to Fusarium infection, a molecular docking analysis was carried out on Fusarium protein targets using each cultivar’s volatile components. F. oxysporum endoglucanase was identified as the preferential protein target of the compounds. These results can be used to identify chemical markers related to the susceptibility degree of black pepper cultivars to plant diseases prevalent in Pará State. 相似文献
40.
Ingrid R. Marques Camila Silveira Monique J. L. Leite Artur M. Piacentini Cristiano Binder Marta E. R. Dotto Alan Ambrosi Marco Di Luccio Cristiane da Costa 《应用聚合物科学杂志》2021,138(24):50558
The modification of the surface characteristics after treatment with plasma in polymeric materials, such as the aging phenomenon, calls the attention of research in the area of nonthermal plasma technology. In this work, a direct treatment with dielectric-barrier discharge plasma was used on the surfaces of ultrafiltration membranes. The measurements of the contact angle with water, attenuated total reflectance accessory, zeta potential, atomic force microscopy and scanning electron microscopy-MEV were performed on the surfaces to verify changes after plasma treatment and to understand the occurrence and timing of the plasma aging effect. In the analysis of the membrane performance, hydraulic permeation and protein retention tests were performed. The results showed an improvement in wettability and hydrophilic properties in the post-treated membranes. The study of reversibility/aging of the post-plasma surface is important for research that deals with the modification of polymeric membranes. Changes in surface morphology, topography and wettability of the membranes were observed up to seven days after treatment, with a tendency to return to the initial characteristics of the membranes. 相似文献