Crosslinking treatments for a commercially available aromatic polyamide reverse osmosis membrane were carried out to improve its chlorine resistance.The crosslinking agents including 1,6-hexanediol diglycidyl ether,ad...Crosslinking treatments for a commercially available aromatic polyamide reverse osmosis membrane were carried out to improve its chlorine resistance.The crosslinking agents including 1,6-hexanediol diglycidyl ether,adipoyl dichloride and hexamethylene diisocyanate ester with long flexible aliphatic chains and high reactivity with N-H groups were used in the experiments.Attenuated total reflective Fourier transform infrared spectra verified the successful preparation of highly crosslinked membranes by crosslinking treatments.It was suggested that the crosslinking agents were connected to membrane surface through the reactions with amine and amide Ⅱ groups,which is confirmed by surface charge measurements.Based on contact angle measurements,crosslinking treatments decreased membrane hydrophilicity by introducing methylene groups to membrane surface.With increasing amount of crosslinking agent molecules connected to membrane surface,the hydrolysis of unconnected functional groups of crosslinking agent produced polar groups and increased membrane hydrophilicity.The highly crosslinked membranes showed higher salt rejections and lower water fluxes as compared with the raw membrane.Since the active sites(N-H groups) vulnerable to free chlorine on membrane surface were eliminated by crosslinking treatments,the chlorine resistances of the highly crosslinked membranes were significantly improved by slighter changes in both water fluxes and salt rejections after chlorination.展开更多
Objectives: To describe and analyze risk factors associatedwith disuse of condoms during commercial sexual intercourseamong clients attending sauna and massage centers. Methods: Selected female sex workers from saunas...Objectives: To describe and analyze risk factors associatedwith disuse of condoms during commercial sexual intercourseamong clients attending sauna and massage centers. Methods: Selected female sex workers from saunas andbeauty parlors were trained as interviewers. They surveyedclients during provision of sexual services. Informationcollected included customers' demographics, knowledge ofSTDs, rationale for and history of condom use. Risk factorsfor condom usage were assessed though logistical modeling.Results: A total of 50 clients were interviewed. The rates ofcondom usage for last sexual intercourse with commercial andnon-commercial partners were 57% and 53% for clients ofsauna centers and 30% and 40% for clients of beauty parlors,respectively. The choice to use a condom was influenced byclients 60.8% of the time, sex workers 30.4%, and otherfactors 8.8%. The choice against using a condom was decidedupon by clients 69.7% of the time, sex workers 9.1%, andother factors 21.2%. Multivariate analysis showed thateducational level and perception of risk of infection werefactors for condom use. Clients with a high school educationhad a higher condom use rate than those with a middle schooleducation or less. Furthermore, clients who perceived risk ofdisease used condoms more frequently than those who did not.Conclusions: Clients played a significant role in decidingwhether or not to use a condom during commercial sex. Lackof perception of risk is a major factor for not using condoms.A program for promotion of prophylactics targeting bothcommercial sex workers and their clients is recommended.展开更多
基金Supported by the National Natural Science Foundation of China （20676095）the Program of Introducing Talents of Discipline to Universities （B06006）
文摘Crosslinking treatments for a commercially available aromatic polyamide reverse osmosis membrane were carried out to improve its chlorine resistance.The crosslinking agents including 1,6-hexanediol diglycidyl ether,adipoyl dichloride and hexamethylene diisocyanate ester with long flexible aliphatic chains and high reactivity with N-H groups were used in the experiments.Attenuated total reflective Fourier transform infrared spectra verified the successful preparation of highly crosslinked membranes by crosslinking treatments.It was suggested that the crosslinking agents were connected to membrane surface through the reactions with amine and amide Ⅱ groups,which is confirmed by surface charge measurements.Based on contact angle measurements,crosslinking treatments decreased membrane hydrophilicity by introducing methylene groups to membrane surface.With increasing amount of crosslinking agent molecules connected to membrane surface,the hydrolysis of unconnected functional groups of crosslinking agent produced polar groups and increased membrane hydrophilicity.The highly crosslinked membranes showed higher salt rejections and lower water fluxes as compared with the raw membrane.Since the active sites(N-H groups) vulnerable to free chlorine on membrane surface were eliminated by crosslinking treatments,the chlorine resistances of the highly crosslinked membranes were significantly improved by slighter changes in both water fluxes and salt rejections after chlorination.
基金This study was supported by China National Center for AIDS Prevention and Control and Peking Union School of Public Health.
文摘Objectives: To describe and analyze risk factors associatedwith disuse of condoms during commercial sexual intercourseamong clients attending sauna and massage centers. Methods: Selected female sex workers from saunas andbeauty parlors were trained as interviewers. They surveyedclients during provision of sexual services. Informationcollected included customers' demographics, knowledge ofSTDs, rationale for and history of condom use. Risk factorsfor condom usage were assessed though logistical modeling.Results: A total of 50 clients were interviewed. The rates ofcondom usage for last sexual intercourse with commercial andnon-commercial partners were 57% and 53% for clients ofsauna centers and 30% and 40% for clients of beauty parlors,respectively. The choice to use a condom was influenced byclients 60.8% of the time, sex workers 30.4%, and otherfactors 8.8%. The choice against using a condom was decidedupon by clients 69.7% of the time, sex workers 9.1%, andother factors 21.2%. Multivariate analysis showed thateducational level and perception of risk of infection werefactors for condom use. Clients with a high school educationhad a higher condom use rate than those with a middle schooleducation or less. Furthermore, clients who perceived risk ofdisease used condoms more frequently than those who did not.Conclusions: Clients played a significant role in decidingwhether or not to use a condom during commercial sex. Lackof perception of risk is a major factor for not using condoms.A program for promotion of prophylactics targeting bothcommercial sex workers and their clients is recommended.
基金荷兰国家科学研究委员会(Nederlandse Organisatie voor Wetenschappeljk Onderzoek,NWO)Vici项目Melody in Speech(VLC.181.040)教育部人文社会科学研究规划基金项目“吴语浊音声母的类型及实验研究”(18YJA740045)的资助。
