The level and pattern of contamination by polychlorinated biphenyls (PCBs) were investigated in tilapia, Oreochromis mossambicus (Peters), sediment, and water from the Shing Mun River. The range of total PCBs was 12.9...The level and pattern of contamination by polychlorinated biphenyls (PCBs) were investigated in tilapia, Oreochromis mossambicus (Peters), sediment, and water from the Shing Mun River. The range of total PCBs was 12.9 ng/g to 181.6 ng/g wet weight in tilapia, 12.7 ng/g to 46.0 ng/g freeze-dried weight in sediment, and 3.8 ng/L to 13.6 ng/L in water. The effect of biomagnification was also observed, PCB concentrations increased from water to sediment to tilapia. PCB congeners occurred in such a way that lower chlorinated PCBs comprised a higher fraction of the total PCBs in water, sediment, and tilapia muscle, whereas higher chlorinated PCBs were more commonly found only in tilapia.展开更多
Based on a systemic survey, the pyrolysis characteristics and apparent kinetics of the municipal solid waste （ MSW） under different conditions were researched using a special pyrolysis reactor, which could overcome ...Based on a systemic survey, the pyrolysis characteristics and apparent kinetics of the municipal solid waste （ MSW） under different conditions were researched using a special pyrolysis reactor, which could overcome the disadvantage of thermo-gravimetric analyzer. The thermal decomposition behaviour of MSW was investigated using thermo-gravimetric （ TG ） analysis at rates of 4.8,6.6,8.4, 12.0 and 13. 2 K/min. The pyrolysis characteristics of MSW were also studied in different function districts. The pyrolysis of MSW is a complex reaction process and three main stages are found according to the results. The first stage represents the degradation of cellulose and hemicellulose, with the maximum degradation rate occuring at 150℃ -200 ℃： the second stage represents dehydrochlorination and depolymerization of intermediate products and the differential thermogravimetric （ DTG ） curves have shoulder peaks at about 300℃： the third stage is the decomposition of the residual big molecular organic substance and lignin at 400 ℃- 600 ℃. Within the range of given experimental conditions, the results of non-linear fitting algorithm and experiment are in agreement with each other and the correlation coefficients are over0. 99. The kinetic characteristics are concerned with the material component and heating rate. The activation energy of reaction decreases with the increase of heating rate.展开更多
Daisy spent one month of her summer this year at St. John＇s, Newfoundland for a summer program, Shad Valley. Shad Valley is a Canadian based summer enrichment program. Students from grade 10 to 12 are eligible to app...Daisy spent one month of her summer this year at St. John＇s, Newfoundland for a summer program, Shad Valley. Shad Valley is a Canadian based summer enrichment program. Students from grade 10 to 12 are eligible to apply to spend four weeks at one of the twelve Shad＇s university campuses across Canada. The program has been succeeding for over 30 years at enhancing students＇ knowledge on sciences, engineering, technology,展开更多
With the deepening of globalization,cultivating college students’critical thinking ability has become the core goal of foreign language education in China.On the basis of clarifying the theoretical connotation of cri...With the deepening of globalization,cultivating college students’critical thinking ability has become the core goal of foreign language education in China.On the basis of clarifying the theoretical connotation of critical thinking ability,this paper attempts to construct the evaluation criteria of its core elements and expounds the internal relationship between Model United Nations(MUN)activities and its cultivation in line with this evaluation criteria.Then,through questionnaire and individual interview,this paper conducts an empirical research on the effect of MUN on the cultivation of students’critical thinking ability.The results show that MUN activities have a positive effect on the cultivation of students’critical thinking ability.展开更多
文摘The level and pattern of contamination by polychlorinated biphenyls (PCBs) were investigated in tilapia, Oreochromis mossambicus (Peters), sediment, and water from the Shing Mun River. The range of total PCBs was 12.9 ng/g to 181.6 ng/g wet weight in tilapia, 12.7 ng/g to 46.0 ng/g freeze-dried weight in sediment, and 3.8 ng/L to 13.6 ng/L in water. The effect of biomagnification was also observed, PCB concentrations increased from water to sediment to tilapia. PCB congeners occurred in such a way that lower chlorinated PCBs comprised a higher fraction of the total PCBs in water, sediment, and tilapia muscle, whereas higher chlorinated PCBs were more commonly found only in tilapia.
基金Supported by National Natural Science Foundation of China( No. 50378061).
文摘Based on a systemic survey, the pyrolysis characteristics and apparent kinetics of the municipal solid waste （ MSW） under different conditions were researched using a special pyrolysis reactor, which could overcome the disadvantage of thermo-gravimetric analyzer. The thermal decomposition behaviour of MSW was investigated using thermo-gravimetric （ TG ） analysis at rates of 4.8,6.6,8.4, 12.0 and 13. 2 K/min. The pyrolysis characteristics of MSW were also studied in different function districts. The pyrolysis of MSW is a complex reaction process and three main stages are found according to the results. The first stage represents the degradation of cellulose and hemicellulose, with the maximum degradation rate occuring at 150℃ -200 ℃： the second stage represents dehydrochlorination and depolymerization of intermediate products and the differential thermogravimetric （ DTG ） curves have shoulder peaks at about 300℃： the third stage is the decomposition of the residual big molecular organic substance and lignin at 400 ℃- 600 ℃. Within the range of given experimental conditions, the results of non-linear fitting algorithm and experiment are in agreement with each other and the correlation coefficients are over0. 99. The kinetic characteristics are concerned with the material component and heating rate. The activation energy of reaction decreases with the increase of heating rate.
文摘Daisy spent one month of her summer this year at St. John＇s, Newfoundland for a summer program, Shad Valley. Shad Valley is a Canadian based summer enrichment program. Students from grade 10 to 12 are eligible to apply to spend four weeks at one of the twelve Shad＇s university campuses across Canada. The program has been succeeding for over 30 years at enhancing students＇ knowledge on sciences, engineering, technology,
文摘With the deepening of globalization,cultivating college students’critical thinking ability has become the core goal of foreign language education in China.On the basis of clarifying the theoretical connotation of critical thinking ability,this paper attempts to construct the evaluation criteria of its core elements and expounds the internal relationship between Model United Nations(MUN)activities and its cultivation in line with this evaluation criteria.Then,through questionnaire and individual interview,this paper conducts an empirical research on the effect of MUN on the cultivation of students’critical thinking ability.The results show that MUN activities have a positive effect on the cultivation of students’critical thinking ability.
