针对障碍期权的定价问题,给出了一种高效的蒙特卡罗(Monte Carlo,MC)模拟方法——基于布朗桥构造路径的随机化拟蒙特卡罗(Brownian bridge path randomization quasi Monte Carlo,BBPR-QMC)方法.首先,用Faure序列代替MC方法中的随机序列...针对障碍期权的定价问题,给出了一种高效的蒙特卡罗(Monte Carlo,MC)模拟方法——基于布朗桥构造路径的随机化拟蒙特卡罗(Brownian bridge path randomization quasi Monte Carlo,BBPR-QMC)方法.首先,用Faure序列代替MC方法中的随机序列,得到了Faure序列的拟蒙特卡罗(quasi Monte Carlo,QMC)模拟方法;其次,应用Moro算法得到了随机化拟蒙特卡罗(randomization quasi Monte Carlo,R-QMC)模拟方法;最后,将QMC方法和R-QMC方法结合,利用布朗桥技术来降低有效维,得到障碍期权定价的BBPR-QMC方法.数值试验表明,与MC方法和R-QMC方法相比较,BBPR-QMC方法模拟的价格与真实价格更接近、收敛速度更快.数值试验证实,BBPR-QMC方法是一种高效求解障碍期权定价的数值方法.展开更多
AIM： To evaluate the effects of different types of dietary fats on the hepatic lipid content and oxidative stress parameters in rat liver with experimental non-alcoholic fatty liver disease （NAFLD）. METHODS： A tot...AIM： To evaluate the effects of different types of dietary fats on the hepatic lipid content and oxidative stress parameters in rat liver with experimental non-alcoholic fatty liver disease （NAFLD）. METHODS： A total of 32 Sprague-Dawley rats were randomly divided into five groups. The rats in the control group （n = 8） were on chow diet （Group 1）, rats （n = 6） on methionine choline-deficient diet （MCDD） （Group 2）, rats （n = 6） on MCDD enriched with olive oil （Group 3）, rats （n = 6） on MCDD with fish oil （Group 4） and rats （n = 6） on MCDD with butter fat （Group 5）. After 2 mo, blood and liver sections were examined for lipids composition and oxidative stress parameters. RESULTS： The liver weight/rat weight ratio increased in all treatment groups as compared with the control group. Severe fatty liver was seen in MCDD ＋ fish oil and in MCDD ＋ butter fat groups, but not in MCDD and MCDD ＋ olive oil groups. The increase in hepatic triglycerides （TG） levels was blunted by 30% in MCDD ＋ olive oil group （0.59 ±0.09） compared with MCDD group （0.85 ±0.04, P 〈 0.004）, by 37% compared with MCDD ＋ fish oil group （0.95 ±0.07, P 〈 0.001）, and by 33% compared with MCDD ＋ butter group （0.09 ±0.1, P 〈 0.01）. The increase in serum TG was lowered by 10% in MCDD ＋ olive oil group （0.9 ±0.07） compared with MCDD group （1.05 ±0.06）. Hepatic cholesterol increased by 15-fold in MCDD group [（0.08 ±0.02, this increment was blunted by 21% in MCDD ＋ fish oil group （0.09 ±0.02）]. In comparison with the control group, ratio of long-chain polyunsaturated fatty acids omega-6/omega-3 increased in MCDD ＋ olive oil, MCDD ＋ fish oil and MCDD ＋ butter fat groups by 345-, 30- and 397-fold, respectively. In comparison to MCDD group （1.58 ±0.08）, hepatic MDA contents in MCDD ＋ olive oil （3.3 ±0.6）, MCDD ＋ fish oil （3.0 ±0.4）, and MCDD ＋ butter group （2.9 ±0.36） were increased by 108%, 91% and 87%, respectively （P 〈 0.004）. Hepatic paraoxonase activity decreased significantly in all treatment groups, mostly with MCDD ＋ olive oil group （-68%）.CONCLUSION： Olive oil decreases the accumulation of triglyceride in the liver of rats with NAFLD, but does not provide the greatest antioxidant activity.展开更多
Objective To investigate whether repeated morphine exposure or prolonged withdrawal could influence operant and spatial learning differentially. Methods Animals were chronically treated with morphine or subjected to m...Objective To investigate whether repeated morphine exposure or prolonged withdrawal could influence operant and spatial learning differentially. Methods Animals were chronically treated with morphine or subjected to morphine withdrawal. Then, they were subjected to two kinds of learning: operant conditioning and spatial learning. Results The acquisition of both simple appetitive and cued operant learning was impaired after repeated morphine treatment. Withdrawal for 5 weeks alleviated the impairments. Single morphine exposure disrupted the retrieval of operant memory but had no effect on rats after 5-week withdrawal. Contrarily, neither chronic morphine exposure nor 5-week withdrawal influenced spatial learning task of the Morris water maze. Nevertheless, the retrieval of spatial memory was impaired by repeated morphine exposure but not by 5-week withdrawal. Conclusion These observations suggest that repeated morphine exposure can influence different types of learning at different aspects, implicating that the formation of opiate addiction may usurp memory mechanisms differentially.展开更多
文摘针对障碍期权的定价问题,给出了一种高效的蒙特卡罗(Monte Carlo,MC)模拟方法——基于布朗桥构造路径的随机化拟蒙特卡罗(Brownian bridge path randomization quasi Monte Carlo,BBPR-QMC)方法.首先,用Faure序列代替MC方法中的随机序列,得到了Faure序列的拟蒙特卡罗(quasi Monte Carlo,QMC)模拟方法;其次,应用Moro算法得到了随机化拟蒙特卡罗(randomization quasi Monte Carlo,R-QMC)模拟方法;最后,将QMC方法和R-QMC方法结合,利用布朗桥技术来降低有效维,得到障碍期权定价的BBPR-QMC方法.数值试验表明,与MC方法和R-QMC方法相比较,BBPR-QMC方法模拟的价格与真实价格更接近、收敛速度更快.数值试验证实,BBPR-QMC方法是一种高效求解障碍期权定价的数值方法.
文摘AIM： To evaluate the effects of different types of dietary fats on the hepatic lipid content and oxidative stress parameters in rat liver with experimental non-alcoholic fatty liver disease （NAFLD）. METHODS： A total of 32 Sprague-Dawley rats were randomly divided into five groups. The rats in the control group （n = 8） were on chow diet （Group 1）, rats （n = 6） on methionine choline-deficient diet （MCDD） （Group 2）, rats （n = 6） on MCDD enriched with olive oil （Group 3）, rats （n = 6） on MCDD with fish oil （Group 4） and rats （n = 6） on MCDD with butter fat （Group 5）. After 2 mo, blood and liver sections were examined for lipids composition and oxidative stress parameters. RESULTS： The liver weight/rat weight ratio increased in all treatment groups as compared with the control group. Severe fatty liver was seen in MCDD ＋ fish oil and in MCDD ＋ butter fat groups, but not in MCDD and MCDD ＋ olive oil groups. The increase in hepatic triglycerides （TG） levels was blunted by 30% in MCDD ＋ olive oil group （0.59 ±0.09） compared with MCDD group （0.85 ±0.04, P 〈 0.004）, by 37% compared with MCDD ＋ fish oil group （0.95 ±0.07, P 〈 0.001）, and by 33% compared with MCDD ＋ butter group （0.09 ±0.1, P 〈 0.01）. The increase in serum TG was lowered by 10% in MCDD ＋ olive oil group （0.9 ±0.07） compared with MCDD group （1.05 ±0.06）. Hepatic cholesterol increased by 15-fold in MCDD group [（0.08 ±0.02, this increment was blunted by 21% in MCDD ＋ fish oil group （0.09 ±0.02）]. In comparison with the control group, ratio of long-chain polyunsaturated fatty acids omega-6/omega-3 increased in MCDD ＋ olive oil, MCDD ＋ fish oil and MCDD ＋ butter fat groups by 345-, 30- and 397-fold, respectively. In comparison to MCDD group （1.58 ±0.08）, hepatic MDA contents in MCDD ＋ olive oil （3.3 ±0.6）, MCDD ＋ fish oil （3.0 ±0.4）, and MCDD ＋ butter group （2.9 ±0.36） were increased by 108%, 91% and 87%, respectively （P 〈 0.004）. Hepatic paraoxonase activity decreased significantly in all treatment groups, mostly with MCDD ＋ olive oil group （-68%）.CONCLUSION： Olive oil decreases the accumulation of triglyceride in the liver of rats with NAFLD, but does not provide the greatest antioxidant activity.
基金This work was supported by grants from the National Natural Science Foundation of China （No. 30470549）the National Basic Research Priorities Programme （973） of China （No.2006CBS00800）
文摘Objective To investigate whether repeated morphine exposure or prolonged withdrawal could influence operant and spatial learning differentially. Methods Animals were chronically treated with morphine or subjected to morphine withdrawal. Then, they were subjected to two kinds of learning: operant conditioning and spatial learning. Results The acquisition of both simple appetitive and cued operant learning was impaired after repeated morphine treatment. Withdrawal for 5 weeks alleviated the impairments. Single morphine exposure disrupted the retrieval of operant memory but had no effect on rats after 5-week withdrawal. Contrarily, neither chronic morphine exposure nor 5-week withdrawal influenced spatial learning task of the Morris water maze. Nevertheless, the retrieval of spatial memory was impaired by repeated morphine exposure but not by 5-week withdrawal. Conclusion These observations suggest that repeated morphine exposure can influence different types of learning at different aspects, implicating that the formation of opiate addiction may usurp memory mechanisms differentially.
