With the development of bionics, the bionic non-smooth surfaces are introduced to the field of tribology. Although non-smooth surface has been studied widely, the studies of non-smooth surface under the natural seawat...With the development of bionics, the bionic non-smooth surfaces are introduced to the field of tribology. Although non-smooth surface has been studied widely, the studies of non-smooth surface under the natural seawater lubrication are still very fewer, especially experimental research. The influences of smooth and non-smooth surface on the frictional properties of the glass fiber-epoxy resin composite（GF/EPR） coupled with stainless steel 316 L are investigated under natural seawater lubrication in this paper. The tested non-smooth surfaces include the surfaces with semi-spherical pits, the conical pits, the cone-cylinder combined pits, the cylindrical pits and through holes. The friction and wear tests are performed using a ring-on-disc test rig under 60 N load and 1000 r/min rotational speed. The tests results show that GF/EPR with bionic non-smooth surface has quite lower friction coefficient and better wear resistance than GF/EPR with smooth surface without pits. The average friction coefficient of GF/EPR with semi-spherical pits is 0.088, which shows the largest reduction is approximately 63.18% of GF/EPR with smooth surface. In addition, the wear debris on the worn surfaces of GF/EPR are observed by a confocal scanning laser microscope. It is shown that the primary wear mechanism is the abrasive wear. The research results provide some design parameters for non-smooth surface, and the experiment results can serve as a beneficial supplement to non-smooth surface study.展开更多
PCR-DGGE approach was used to analyze bacterial diversity in the bottomsection of seven arctic sea ice samples colleted from the Canada Basin.Thirty-two 16S rDNAsequences were obtained from prominent DGGE bands.The cl...PCR-DGGE approach was used to analyze bacterial diversity in the bottomsection of seven arctic sea ice samples colleted from the Canada Basin.Thirty-two 16S rDNAsequences were obtained from prominent DGGE bands.The closest relatives of these sequences arefound to be those of cultivated or uncultured bacteria from antarctic or arctic sea ice.Phylogenetic analysis clustered these sequences or phylotypes withinα-proteobacteria,γ-proteobacteria and CFB(cytophaga-flexibacter-bacteroides)group.Sequences belonging toγ-proteobacteria were dominant and members of the CFB group were highly abundant.It was suggestedthat the CFB group was the representative of the bottom section of sea ice samples.展开更多
Objective To investigate in vitro cytotoxicity and oxidative stress response induced by multiwalled carbon nanotubes （MWCNTs）. Methods Cultured macrophages （murine RAW264.7 cells） and alveolar epithelium cells typ...Objective To investigate in vitro cytotoxicity and oxidative stress response induced by multiwalled carbon nanotubes （MWCNTs）. Methods Cultured macrophages （murine RAW264.7 cells） and alveolar epithelium cells type II （human A549 lung cells） were exposed to the blank control, DNA salt control, and the MWCNTs suspensions at 2.5, 10, 25, and 100 ug/mL for 24 h. Each treatment was evaluated by cell viability, cytotoxicity and oxidative stress. Results Overall, both cell lines had similar patterns in response to the cytotoxicity and oxidative stress of MWCNTs. DNA salt treatment showed no change compared to the blank control. In both cell lines, significant changes at the doses of 25 and 100 ug/mL treatments were found in cell viabilities, cytotoxicity, and oxidative stress indexes. The reactive oxygen species （ROS） generation was also found to be significantly higher at the dose of 10 ug/mL treatment, whereas no change was seen in most of the indexes. The ROS generation in both cell lines went up in minutes, reached the climax within an hour and faded down after several hours. Conclusion Exposure to MWCNTs resulted in a dose-dependent cytotoxicity in cultured RAW264.7 cells and A549 cells, that was closely correlated to the increased oxidative stress.展开更多
Conodonts and fusulinids are the two most widely used biotic groups for subdividing and correlating Bashkirian and Moscovian strata. The definition of the base of the Global Moscovian Stage is undecided because there ...Conodonts and fusulinids are the two most widely used biotic groups for subdividing and correlating Bashkirian and Moscovian strata. The definition of the base of the Global Moscovian Stage is undecided because there are many disagreements among existing boundary definition proposals,each of which has disadvantages. Declinognathodus donetzianus is easily recognized but somewhat limited in its paleogeographic distribution. Idiognathoides postsulcatus is slightly more widespread, but it is less easily identified and its occurrences may be diachronous from region to region. Diplognathodus ellesmerensis is easily recognized and even more widespread, but it is usually rare and its ancestry is not adequately known. The Naqing Section of South Guizhou, South China contains diverse conodont evolutionary lineages among different taxa, including Idiognathoides, Idiognathodus, Diplognathodus,Neognathodus, Gondolella and Mesogondolella. There are numerous transitional forms in almost every lineage of the Naqing section, which shows that the prospects for South China to play a critical role in determining the basal Moscovian Stage definition are good.展开更多
Objective To examine the association between habitual sleep duration and obesity among Chinese adults. Methods The association of sleep duration and obesity was investigated among 7,094 community-dwelling Chinese adul...Objective To examine the association between habitual sleep duration and obesity among Chinese adults. Methods The association of sleep duration and obesity was investigated among 7,094 community-dwelling Chinese adults. Sleep duration was self-reported. In this study, obesity was defined as follows： body mass index （BMI） ≥ 28 kg/m^2, waist circumference （WC） ≥ 85 cm in men and ≥ 80 cm in women, and percent body fat （%BF） ≥ 25 in men and ≥ 35 in women. Logistic and quantile regressions were employed to examine relationships of interest. Results Overall, 6.42% of the participants reported short sleep durations （〈 6 h/d） while 14.71% reported long （≥ 9 h/d） sleep durations. Long sleepers （≥ 9 h/d） represented a greater frequency of women with obesity [odds ratio （OR）： 1.30; 95% confidence interval （CI）, 1.02-1.67] and high body fat （1.43, 1.04-1.96） than those who slept 7-8 h/d. An association between long sleep times and higher BMI estimations was found across the 10th-75th percentile of the BMI distribution. Among men, long sleepers （≥ 9 h/d） presented lower risks of developing abdominal obesity compared with individuals who slept 7-8 h/d （OR = 0.79, 95% CI： 0.44-0.99）. Conclusion Our study suggests that long sleep durations are associated with general obesity in Chinese women but reduced waist circumferences in men. Confirmatory studies are needed to determine the heterogeneous association of sleep time and obesity by gender.展开更多
基金Supported by National Natural Science Foundation of China(Grant No.51375421)Hebei Provincial Key Project of Science and Technology Research of(ZD20131027)
文摘With the development of bionics, the bionic non-smooth surfaces are introduced to the field of tribology. Although non-smooth surface has been studied widely, the studies of non-smooth surface under the natural seawater lubrication are still very fewer, especially experimental research. The influences of smooth and non-smooth surface on the frictional properties of the glass fiber-epoxy resin composite（GF/EPR） coupled with stainless steel 316 L are investigated under natural seawater lubrication in this paper. The tested non-smooth surfaces include the surfaces with semi-spherical pits, the conical pits, the cone-cylinder combined pits, the cylindrical pits and through holes. The friction and wear tests are performed using a ring-on-disc test rig under 60 N load and 1000 r/min rotational speed. The tests results show that GF/EPR with bionic non-smooth surface has quite lower friction coefficient and better wear resistance than GF/EPR with smooth surface without pits. The average friction coefficient of GF/EPR with semi-spherical pits is 0.088, which shows the largest reduction is approximately 63.18% of GF/EPR with smooth surface. In addition, the wear debris on the worn surfaces of GF/EPR are observed by a confocal scanning laser microscope. It is shown that the primary wear mechanism is the abrasive wear. The research results provide some design parameters for non-smooth surface, and the experiment results can serve as a beneficial supplement to non-smooth surface study.
基金supported by the National Basic Research Program of China under coutract No.2004CB719601the Science and Technology Basic Work Program of China under coutract No.2003DEB5J057+1 种基金the National Natural Science Foundation of China under contract No.40376001This work is also a part of the Project"Second Chinese National Arctic Research Expedition"or CHINARE-2003 supported by the Ministry of Finance of China and organized by the Chinese Arctic and Antarctic Administration(CAA).
文摘PCR-DGGE approach was used to analyze bacterial diversity in the bottomsection of seven arctic sea ice samples colleted from the Canada Basin.Thirty-two 16S rDNAsequences were obtained from prominent DGGE bands.The closest relatives of these sequences arefound to be those of cultivated or uncultured bacteria from antarctic or arctic sea ice.Phylogenetic analysis clustered these sequences or phylotypes withinα-proteobacteria,γ-proteobacteria and CFB(cytophaga-flexibacter-bacteroides)group.Sequences belonging toγ-proteobacteria were dominant and members of the CFB group were highly abundant.It was suggestedthat the CFB group was the representative of the bottom section of sea ice samples.
基金supported partly by a grant from Shanghai Science and Technology Committee International Collaboration Program (Project No. 055207078)
文摘Objective To investigate in vitro cytotoxicity and oxidative stress response induced by multiwalled carbon nanotubes （MWCNTs）. Methods Cultured macrophages （murine RAW264.7 cells） and alveolar epithelium cells type II （human A549 lung cells） were exposed to the blank control, DNA salt control, and the MWCNTs suspensions at 2.5, 10, 25, and 100 ug/mL for 24 h. Each treatment was evaluated by cell viability, cytotoxicity and oxidative stress. Results Overall, both cell lines had similar patterns in response to the cytotoxicity and oxidative stress of MWCNTs. DNA salt treatment showed no change compared to the blank control. In both cell lines, significant changes at the doses of 25 and 100 ug/mL treatments were found in cell viabilities, cytotoxicity, and oxidative stress indexes. The reactive oxygen species （ROS） generation was also found to be significantly higher at the dose of 10 ug/mL treatment, whereas no change was seen in most of the indexes. The ROS generation in both cell lines went up in minutes, reached the climax within an hour and faded down after several hours. Conclusion Exposure to MWCNTs resulted in a dose-dependent cytotoxicity in cultured RAW264.7 cells and A549 cells, that was closely correlated to the increased oxidative stress.
基金supported by the Ministry of Science and Technology of China (2006FY120300-8)the Chinese Academy of Sciences (KZCX2-YW-122, KZCX2-YW-Q050603)National Natural Science Foundation of China (NSFC), and the CAS/SAFEA International Partnership Program for Creative Research Teams
文摘Conodonts and fusulinids are the two most widely used biotic groups for subdividing and correlating Bashkirian and Moscovian strata. The definition of the base of the Global Moscovian Stage is undecided because there are many disagreements among existing boundary definition proposals,each of which has disadvantages. Declinognathodus donetzianus is easily recognized but somewhat limited in its paleogeographic distribution. Idiognathoides postsulcatus is slightly more widespread, but it is less easily identified and its occurrences may be diachronous from region to region. Diplognathodus ellesmerensis is easily recognized and even more widespread, but it is usually rare and its ancestry is not adequately known. The Naqing Section of South Guizhou, South China contains diverse conodont evolutionary lineages among different taxa, including Idiognathoides, Idiognathodus, Diplognathodus,Neognathodus, Gondolella and Mesogondolella. There are numerous transitional forms in almost every lineage of the Naqing section, which shows that the prospects for South China to play a critical role in determining the basal Moscovian Stage definition are good.
基金supported by China's Ministry of Science and Technology(No.2008BAI56B04)
文摘Objective To examine the association between habitual sleep duration and obesity among Chinese adults. Methods The association of sleep duration and obesity was investigated among 7,094 community-dwelling Chinese adults. Sleep duration was self-reported. In this study, obesity was defined as follows： body mass index （BMI） ≥ 28 kg/m^2, waist circumference （WC） ≥ 85 cm in men and ≥ 80 cm in women, and percent body fat （%BF） ≥ 25 in men and ≥ 35 in women. Logistic and quantile regressions were employed to examine relationships of interest. Results Overall, 6.42% of the participants reported short sleep durations （〈 6 h/d） while 14.71% reported long （≥ 9 h/d） sleep durations. Long sleepers （≥ 9 h/d） represented a greater frequency of women with obesity [odds ratio （OR）： 1.30; 95% confidence interval （CI）, 1.02-1.67] and high body fat （1.43, 1.04-1.96） than those who slept 7-8 h/d. An association between long sleep times and higher BMI estimations was found across the 10th-75th percentile of the BMI distribution. Among men, long sleepers （≥ 9 h/d） presented lower risks of developing abdominal obesity compared with individuals who slept 7-8 h/d （OR = 0.79, 95% CI： 0.44-0.99）. Conclusion Our study suggests that long sleep durations are associated with general obesity in Chinese women but reduced waist circumferences in men. Confirmatory studies are needed to determine the heterogeneous association of sleep time and obesity by gender.
