Objective To assess the efficiency of algae extermination by the combined copper electrolysis technology. Methods The combined copper electrolysis technology and copper sulphate were used to treat the Synechocystissp strain PCC6803 in the steady stage of culture in different time and the efficiency of algae extermination was assessed. Results No alga in the water sample was detected after 0.5 and 1 hour of treatment with copper electrolysis technology and copper sulphate respectivly as the concentration of Cu2+ was at 0.3 mg/L. The extermination rate of algae was 80.75% after 12 days of treatment of combined copper electrolysis. This technology could effectively decrease the turbidity, smell, COD, ammonia nitrogen and increase the dissolved oxygen in the treated water. Conclusion The Cu2+ released by copper electrolyzing has a stronger efficiency of algae extermination compared with copper sulfate. The combined copper electrolysis technology will be a satisfactory method for algae extermination in the landscape water.

BACKGROUND: Peak bone mass and standard deviation (SD) in different regions are varied, which have great influence on diagnosis of osteoporosis. To establish a complete database can provide accurate evidence for osteoporosis diagnosis. OBJECTIVE: To investigate the influence of bone mineral densities (BMD) and their SD of young people on the detective rate of osteoporosis in general population. DESIGN, TIME AND SETTING: Investigation analysis was performed at Beijing, Shanghai, Guangzhou, Nanjing, Jiaxing and Chengdu between January 1997 and December 1999. PARTICIPANTS: 11418 subjects from related 6 centers of BMD reference database in China were investigated and analyzed using prospective and retrospective methods, including 3 666 males, and 7 752 females aged 20-90 years. Of them, 2385 were from Beijing, 1178 from Guangzhou, 1404 from Shanghai, 2938 from Nanjing, 1425 from Chengdu, and 2088 from Jiaxing. The subjects were selected from community investigation, physical examination volunteers. METHODS: BMD of the lumbar spine (L2-4) and the hip in 11, 418 subjects from the related 6 centers in China was measured with GE-Lunar dual energy X-ray absorptiometry (DXA) and the BMD reference database was established. The accuracy rate of the inner machine was 0.3%-0.7%, and the accuracy of different machines averaged 1.1%. MAIN OUTCOME MEASURES: Lumbar BMD distribution of different age groups from 6 centers; influence of young people's BMD and its SD on detective rate of osteoporosis. RESULTS: Different BMD and SD were found in the individual subject from 6 centers, and the maximum differences were 0.098 g/cm2 and 0.027 g/cm2. With mean BMD and SD of the individuals from 6 centers as references, different T-scores and the detective rates of osteoporosis derived from the T-scores were found in the same group. The detective rate increased by 1.6% when BMD of the young people increased by 0.01 g/cm2 (positive correlation), but the detective rate decreased by 4% when SD increased by 0.01g/cm2 (negative correlation). CONCLUSION: Changes in BMD and SD of the young people can influence the detective rate of osteoporosis. To achieve comparability for the detective rate of osteoporosis in different centers, the specific reference database should be established for the same race, the same area, and the same bone densitometry machine. The T-score should be determined with the normal BMD and SD of the young, people as the reference database.