102 research outputs found
Species profiles and normalized reactivity of volatile organic compounds from gasoline evaporation in China
No full textIn China, fast increase in passenger cars and gasoline consumption with yet quite limited vapor recovery during gasoline distribution has procured growing concern about gasoline evaporation as an important emission source of volatile organic compounds (VOCs), particularly in megacities hard-hit by air quality problems. This study presents VOC species profiles related to major pathways of gasoline evaporative loss in China, including headspace displacement, refueling operations and spillage/leakage. Apart from liquid gasoline and headspace vapors, gasoline vapors emitted when refueling cars in service stations or tank trucks in oil marketing depots were also sampled in situ with vapor recovery units (VRUs) turning on/off. Alkanes, alkenes and aromatic hydrocarbons accounted for 55-66, 21-35 and 4-8% in refueling vapors, 59-72, 18-28 and 4-10% in headspace vapors and 33-51, 8-15 and 38-48% in liquid gasoline samples, respectively. During refueling with VRUs turning on, total VOCs in vapors were less than one fifth of that with VRUs turning off, and aromatic hydrocarbons had higher weight percentages of about 8% in contrast with that of about 4% during refueling with VRUs turning off. Refueling vapors, especially for that with VRUs turning off, showed a larger fraction of light hydrocarbons including C-3-O-5 light alkenes when compared to headspace vapors, probably due to splashing and disturbance during filling operation. In refueling or headspace vapors the ratios of i-pentane/benzene, i-pentane/toluene, and MTBE (methyl tert-butyl ether)/benzene ranged 8.7-57, 2.7-4.8, and 1.9-6.6, respectively; and they are distinctively much higher than those previously reported in vehicle exhausts. Calculated normalized reactivity or ozone formation potential of the gasoline vapors in China ranged 3.3-4.4 g O-3 g(-1) VOC, about twice that of gasoline headspace vapors reported in USA as a result of larger fractions of alkenes in China's gasoline vapors. The results suggested that reducing VOC emission from gasoline distribution sector would particularly benefit ground-level ozone control in China. (C) 2013 Elsevier Ltd. All rights reserved.Environmental SciencesMeteorology & Atmospheric SciencesSCI(E)EI5ARTICLE110-1187
Delayed Reduction of Hepatitis B Viral Load and Dynamics of Adefovir-Resistant Variants during Adefovir plus Entecavir Combination Rescue Therapy
No full text© 2015 Ivyspring International Publisher. Reproduction is permitted for personal, noncommercial use, provided that the article is in whole, unmodified, and properly cited
A safe and efficient approach to fabricate black carbon-doped rutile titania by substitution of oxygen at carbon sites in titanium carbide film
No full textReview on the Photocatalyst Coatings of TiO2: Fabrication by Mechanical Coating Technique and Its Application
No full textThis review presents the latest results of studies directed at photocatalyst coatings of titanium dioxide (TiO2) prepared by mechanical coating technique (MCT) and its application. Compared with traditional coating techniques, MCT is a simple, low cost and useful coating formation process, which is proposed and developed based on mechanical frictional wear and impacts between substrate materials and metal powder particles in the bowl of planetary ball mill. The formation process of the metal coatings in MCT includes four stages: The nucleation by adhesion, the formation and coalescence of discrete islands, formation and thickening of continuous coatings, exfoliation of continuous coatings. Further, two-step MCT was developed based on the MCT concept for preparing composite coatings on alumina (Al2O3) balls. This review also discusses the influence on the fabrication of photocatalyst coatings after MCT and improvement of its photocatalytic activity: oxidation conditions, coating materials, melt salt treatment. In this review, the oxidation conditions had been studied on the oxidation temperature of 573 K, 673 K, 773 K, 873 K, 973 K, 1173 K and 1273 K, the oxidation time of 0.5 h, 1 h, 3 h, 10 h, 15 h, 20 h, 30 h, 40 h, and 50 h. The photocatalyst coatings showed the highest photocatalytic activity with the oxidation condition of 1073 K for 15 h. The metal powder of Ti, Ni and Cr had been used as the coating materials. The composite metal powder could affect the surface structure and photocatalytic activity. On the other hand, the melt salt treatment with KNO3 is an effective method to form the nano-size structure and enhance photocatalytic activity, especially under visible light
Research on practice and incentive mechanism of flipped classroom based on small private online course
No full textFabrication of Photocatalyst Composite Coatings of Cr-TiO2 by Mechanical Coating Technique and Oxidation Process
No full textThe photocatalyst composite coatings on alumina (Al2O3) balls had been prepared by mechanical coating technique (MCT) with titanium (Ti) powder, adding a certain content of chromium (Cr) powder and a subsequent oxidation process. The effect of oxidation conditions and adding Cr on the composite coatings of chromium-titanium dioxide (Cr-TiO2) was investigated. The results show Cr-TiO2 coatings are with mixed-phase of anatase and rutile under different oxidation conditions, and the mass fraction of the rutile phase (XR) has been obviously increased when under 973 K. The SEM images indicate that adding Cr could significantly accelerate the growth of surface structures, especially at 1073 K. The photocatalytic activity of Cr-TiO2 coatings firstly increases, then decreases, with the addition of Cr. Compared with that of two other oxidation conditions, the enhancement on photocatalytic activity by adding Cr under visible light is relatively higher, especially at 973 K for 10 h
A Contrastive Study of Hard Times and the Two Versions from the Perspective of Textual Cohesion
No full textCohesion is the semantic concept of discourse. And the key to coherence of discourse is to use various cohesive devices rationally. Due to the different ways of thinking between China and the West, English and Chinese have great difficulties in textual cohesion. In order to better carry out translation practice, it is necessary to understand the cohesive devices of the text. Both English and Chinese use cohesive devices, but they are different. The complicated work of English-Chinese translation is the treatment of cohesive devices and the quality of the translation depends on the proper handling of the cohesive devices. This paper is based on a book cohesion in English by Halliday and Hasan in 1976, whose research methods are comparative analysis and descriptions. Choosing the works hard times of Charles Dickens, a famous British critic of the 19th century as well as Foreign Language Teaching and Research Press Mu Run and China Books Publishing House Wu Sujun two versions as the research object. By analyzing the differences between English and Chinese texts, the author tries to find out the reasons for the differences and hopes to provide some help for English-Chinese translation
Anticancer activity of 2α, 3α, 19β, 23β-Tetrahydroxyurs-12-en-28-oic acid (THA), a novel triterpenoid isolated from Sinojackia sarcocarpa.
No full textBACKGROUND: Natural products represent an important source for agents of cancer prevention and cancer treatment. More than 60% of conventional anticancer drugs are derived from natural sources, particularly from plant-derived materials. In this study, 2α, 3α, 19β, 23β-tetrahydroxyurs-12-en-28-oic acid (THA), a novel triterpenoid from the leaves of Sinojackia sarcocarpa, was isolated, and its anticancer activity was investigated both in vitro and in vivo. PRINCIPAL FINDINGS: THA possessed potent tumor selected toxicity in vitro. It exhibited significantly higher cytotoxicity to the cancer cell lines A2780 and HepG2 than to IOSE144 and QSG7701, two noncancerous cell lines derived from ovary epithelium and liver, respectively. Moreover, THA showed a dose-dependent inhibitory effect on A2780 ovary tumor growth in vivo in nude mice. THA induced a dose-dependent apoptosis and G2/M cell cycle arrest in A2780 and HepG2 cells. The THA-induced cell cycle arrest was accompanied by a downregulation of Cdc2. The apoptosis induced by THA was evident by induction of DNA fragmentation, release of cytoplasmic Cytochrome c from mitochondria, activation of caspases, downregulation of Bcl-2 and upregulation of Bax. CONCLUSION: The primary data indicated that THA exhibit a high toxicity toward two cancer cells than their respective non-cancerous counterparts and has a significant anticancer activity both in vitro and in vivo. Thus, THA and/or its derivatives may have great potential in the prevention and treatment of human ovary tumors and other malignancies
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