排序方式: 共有28条查询结果,搜索用时 31 毫秒
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Ali Sarafraz-Yazdi Soroosh Sepehr Zarrin Es’haghi Hamed Piri Moghadam 《Chromatographia》2010,72(9-10):923-931
In this research, the sol–gel technology was applied for the preparation of solid-phase microextraction fibers for extracting of methyl tert-butyl ether (MTBE) from environmental water samples. For this purpose, two different polymers such as poly(ethylene glycol) (PEG) and combination of PEG and multiwall carbon nanotubes (MWCNTs) were prepared using sol–gel technology as coating procedure for the fibers. The pre-concentration process followed by GC–FID determination was used and the results evidenced that pre-concentration factor for PEG/CNTs fiber was approximately five times higher than PEG. Parameters affecting the extraction efficiency such as temperature, extraction time, stirring speed and salt effect for each fiber were investigated and optimized. On the optimal conditions, the linear range for MTBE with PEG and PEG/CNT fibers were 10–3,000 and 1–1,000 ng mL?1 and the detection limits (S/N = 3) were 1.0 and 0.3 ng mL?1, respectively. The sol–gel PEG/CNTs fiber has good performance and therefore relatively better figures of merit and experimental results such as thermal stability (up to 320 °C), average of life time (over 150 times) and repeatability (RSD < 4) in comparison to conventional PDMS/Carboxen fiber, which was already reported for determination of MTBE. 相似文献
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The convective instability of a horizontal liquid layer confined in an annular Hele–Shaw cell subject to a constant rotation and submitted to a centrifugal gradient of temperature is investigated. Using a linear stability analysis, we study the effects of both Coriolis forces and curvature aspect on the stationary convective threshold when the Prandtl number is of the order of unity or larger than unity. We show that the Coriolis forces have a stabilizing effect, and the wave number is independent of these forces. However, a multicellular regime in the radial direction is observed for small Ekman numbers. The results related to the influence of the curvature are also shown. To cite this article: S. Ramezani et al., C. R. Mecanique 330 (2002) 633–640. 相似文献
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Base‐Catalyzed Formation of Isoxazoles from Dialkyl Acetylenedicarboxylates and 2‐Nitroacetophenones
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The reaction of dialkyl acetylenedicarboxylates with 1‐aryl‐2‐nitroethanones in the presence of pyridine leads to dialkyl 5‐aryloyl‐isoxazole‐3,4‐dicarboxylates through a novel mechanism, which involves a [2+2] cycloaddition/ring opening/cyclization sequence. 相似文献
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Niloofar Parizadeh Eskandar Alipour Sepehr Soleymani Rezvan Zabihollahi Mohammad Reza Aghasadeghi 《Phosphorus, sulfur, and silicon and the related elements》2018,193(4):225-231
Novel quinolone derivatives featuring an 1,3,4-oxadiazole ring as a metal-chelating component and a benzyl group base on HIV-1 integrase inhibitors pharmacophore were designed and synthesized. An antiviral assay revealed that most analogues inhibited HIV-1 replication in the cell culture. Our results showed that compounds bearing small alkyl groups as R group were inactive in anti-HIV-1 assay, whereas compounds possessing benzyl or substituted benzyl at the same position showed good anti-HIV activity with the range of 20–57% at 100 μM concentration. Among them, 3-(5-((2-fluorobenzyl)thio)-1,3,4-oxadiazol-2-yl)-8-phenylquinolin-4-(1H)-one (compound 13) showed reasonable cell-based antiviral activity (EC50 = 50 μM) with no considerable cytotoxicity (CC50 > 100 μM) in the cell viability assay, suggesting that it may be amenable to further development for identifying new anti-HIV-1 agents. Docking studies using the later crystallographic data available for PFV integrase corroborate favorable binding to the active site of HIV integrase, providing a basis for the design of more potent analogues. 相似文献
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A novel model of Cw diode pumped Yb:YAG thin disk laser has been presented to simulate absorption pump power distribution by Monte-Carlo ray tracing. Comparing obtained results with the common distribution function indicate the offered model is quite trustful. So these findings help to evaluate temperature distribution due to the 3D finite element analyses (FEA) based on heat conduction equation. To improve our simulation the temperature dependent of crystal property such as the absorption coefficient, thermal conductivity, stimulated emission cross section and Boltzman population factors are considered by a numerical iterative approach. 相似文献
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Zare Davijani Neda Kia-Kojoori Reza Abdolmohammadi Shahrzad Sadegh-Samiei Sepehr 《Molecular diversity》2022,26(4):2121-2134
Molecular Diversity - In this research, we synthesized the Fe3O4/CuO/ZnO@MWCNT magnetic nanocomposites using water extract of Petasites hybridus rhizome, and the high performance of synthesized... 相似文献
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Ali Abbasi Ali Karimi Hamidreza Aghabozorg Sepehr Sadighi Maryam Alizadeh Aval 《国际化学动力学杂志》2020,52(3):159-166
MoS2 has been commonly used as a catalyst in hydrodesulfurization (HDS) of petroleum cuts in crude oil refineries. In this study, the synthesis of unsupported MoS2 and Co-promoted MoS2 nanosheets produced from molybdenum oxide and thiourea is reported. The synthesized samples were characterized by using x-ray fluorescence, x-ray diffraction, Brunauer–Emmett–Teller (BET), temperature-programmed reduction, thermal gravimetric analysis, and transmission electron microscopy methods, and then they were utilized for HDS of diesel through a fixed-bed catalytic reactor. Results indicated that a cobalt promoter affected both the number and the performance of active sites of the molybdenum sulfides, and the activity of the promoted MoS2 catalyst was consistently higher than that of the MoS2 catalyst. More significantly, the activity of the promoted catalyst was slightly declined during 48 h continuous HDS reaction, which indicated the stability of this catalyst. Additionally, during 12 h of test run, the HDS activity of the promoted catalyst was about 60% higher than MoS2 one. 相似文献