该研究旨在评估1990-2016年间中国和日本因高钠摄入量导致的脑卒中死亡率的长期趋势。研究人员从全球疾病负担(global burden of disease,GBD)2016中获得死亡率数据,并采用年龄段队列方法进行分析。年龄标准化死亡率数据显示,与高钠摄...该研究旨在评估1990-2016年间中国和日本因高钠摄入量导致的脑卒中死亡率的长期趋势。研究人员从全球疾病负担(global burden of disease,GBD)2016中获得死亡率数据,并采用年龄段队列方法进行分析。年龄标准化死亡率数据显示,与高钠摄入相关的脑卒中死亡率呈下降趋势。中国男性和中国女性每年的净降低率分别为-3.1%和-5.0%;而日本男性和日本女性分别为-4.6%和-5.7%。展开更多
Objective: The remodeling of uterine connective tissue during labor can lead to the reorganization of the extracellular matrix that, in turn, may influence the biomechanical properties of the myometrial wall. We hypot...Objective: The remodeling of uterine connective tissue during labor can lead to the reorganization of the extracellular matrix that, in turn, may influence the biomechanical properties of the myometrial wall. We hypothesized that the stretching of the lower uterine segment in laboring women with dystocia changes the viscoelastic properties of the uterine wall. Study design: We tested the tensile strength of lower uterine segment myometrium in 68 pregnant women at term. The biomechanical, structural, and biochemical properties were compared among 3 groups: (1) 39 laboring women who underwent primary low- transverse cesarean delivery for labor dystocia, (2) 12 nonlaboring women who underwent primary elective low- transverse cesarean delivery and (3) 17 women who underwent an elective repeat low- transverse cesarean delivery at term. The tensile properties were quantitated with a stretching regimen that was designed to mimic the conditions of labor. Parameters such as slope, yield point, and break point were recorded, analyzed, and interpreted. Biochemical properties were determined by the measurement of the sulfated glycosaminoglycans, hydroxyproline, and pyridinoline- deoxypyridinoline. Histologic properties of the connective tissue were assessed by collagen birefringence. Lastly, the association between these properties and biomechanical responses were compared among groups. Results: Lower uterine segment myometrium specimens obtained from laboring women were stiffer compared with specimens from women who were not in labor (P = .013) or had scarred myometrium (P < .001). The force that was required to reach the yield point was similar between labor and nonlabor groups (P = .216). Likewise, a previous lower uterine segment scar did not alter the yield point. The break point was similar among all groups (P = .317). Sulfated glycosaminoglycan levels were unaffected by labor or scarring (P = .354). Scarred lower uterine segment myometrium had a higher collagen content compared with unscarred myometrium specimens that were obtained during labor (P = .025). Although there were similar degrees of collagen cross- linking among groups (P = .212), there was lower collagen birefringence in myometrium from laboring women compared with nonlaboring women (P < .001). Conclusion: Labor alters the viscoelastic properties of myometrium. Lower uterine segment myometriumis stiffest in women with dysfunctional labor compared with nonlabor control subjects. Labor and scarring also alter the pattern of collagen birefringence. Similar collagen cross- linking among the study groups may explain the reason that the breaking strength of the tissue is not altered by the state of labor and the reason that the rupture of the uterine scar is a rare event.展开更多
中国的粮食安全、水资源和水环境近60年来发生了深刻变迁.长期以来人们对这三者的演化关系缺乏定量化理解.文章在回顾国内外研究进展的基础上,结合1955~2014年全国粮食作物模拟、灌溉发展和氮素平衡等最新研究,归纳得到如下认识:(1)灌...中国的粮食安全、水资源和水环境近60年来发生了深刻变迁.长期以来人们对这三者的演化关系缺乏定量化理解.文章在回顾国内外研究进展的基础上,结合1955~2014年全国粮食作物模拟、灌溉发展和氮素平衡等最新研究,归纳得到如下认识:(1)灌溉对减小中国农业旱灾风险贡献了(31±2)%.在过去60年中对粮食产量年际波动影响最大的不是气候,而是社会经济因素.(2)自1955年来,化肥氮对当前粮食产量贡献了(45±3)%,灌溉发展和化肥氮的耦合贡献为(47±3)%.(3)灌溉和农业生产水平的提高加强了中国粮食系统的稳定性.在保障粮食种植面积的情况下,即使遭受到百年一遇的旱灾,全国自产粮食的人均占有量也可达到约3200k Cal d^-1的高水平供给.(4)丰水与平水年景杜绝北方地下水超采不会影响中国的粮食安全水平.1999~2014年地下水超采对粮食平均贡献仅为3%左右.但北方地下水枯竭将产生灾难性后果.(5)未来气候变化可导致极端农业旱灾风险增加.(6)根据氮流失模拟结果和水体氮浓度观测数据,全国淡水环境的氮容量安全阈值为(520±70)万t a^-1,但目前氮排放量达到(1450±310)万t a^-1.其中有14个省的农田氮流失超过了自身阈值,主要分布在缺水的北方.(7)提高农田管理水平可减小220~240万吨的农田氮流失,仅占全国水体氮总超排量的24~26%.(8)当前污水处理体系也无法解决中国的氮污染问题.2014年全国城市生活污水处理厂的除氮量仅为70万吨左右.(9)解决当前氮污染问题的唯一有效途径是重构城乡养分循环体系;若要将氮流失限制在安全阈值内,需要在提高农田氮肥利用效率基础上,把全国有机废物还田率从当前的40%以下提高到86%以上,其中9个省份需要达到95%以上.中国如果要实现农业、水资源和水环境的可持续发展,应在统一的科学框架下制定部门间相互协调的长远规划和行动方案.在改进农村土地流转制的基础上建立新型规模化农业经营制度,制定弃耕地的复耕政策、明确省级粮食生产责任制,扭转粮食重心持续北移的格局,恢复北方地下水储量,增强水体自净功能.重构城乡养分循环体系的经济成本远低于污水处理和环境退化成本.以2010年价格计,基础设施建设约需7000亿元,年运行成本约1200~1900亿元.这可以通过重新统筹分散在农业、环保、水利、城乡建设等行业的环保和污染治理资金予以解决,让农民成为这一体系的主要参与者和受益者.针对人类共同面临的水-氮管理难题,中国完全有可能在保障粮食安全的条件下探索出独特的可持续发展之路.展开更多
文摘该研究旨在评估1990-2016年间中国和日本因高钠摄入量导致的脑卒中死亡率的长期趋势。研究人员从全球疾病负担(global burden of disease,GBD)2016中获得死亡率数据,并采用年龄段队列方法进行分析。年龄标准化死亡率数据显示,与高钠摄入相关的脑卒中死亡率呈下降趋势。中国男性和中国女性每年的净降低率分别为-3.1%和-5.0%;而日本男性和日本女性分别为-4.6%和-5.7%。
文摘Objective: The remodeling of uterine connective tissue during labor can lead to the reorganization of the extracellular matrix that, in turn, may influence the biomechanical properties of the myometrial wall. We hypothesized that the stretching of the lower uterine segment in laboring women with dystocia changes the viscoelastic properties of the uterine wall. Study design: We tested the tensile strength of lower uterine segment myometrium in 68 pregnant women at term. The biomechanical, structural, and biochemical properties were compared among 3 groups: (1) 39 laboring women who underwent primary low- transverse cesarean delivery for labor dystocia, (2) 12 nonlaboring women who underwent primary elective low- transverse cesarean delivery and (3) 17 women who underwent an elective repeat low- transverse cesarean delivery at term. The tensile properties were quantitated with a stretching regimen that was designed to mimic the conditions of labor. Parameters such as slope, yield point, and break point were recorded, analyzed, and interpreted. Biochemical properties were determined by the measurement of the sulfated glycosaminoglycans, hydroxyproline, and pyridinoline- deoxypyridinoline. Histologic properties of the connective tissue were assessed by collagen birefringence. Lastly, the association between these properties and biomechanical responses were compared among groups. Results: Lower uterine segment myometrium specimens obtained from laboring women were stiffer compared with specimens from women who were not in labor (P = .013) or had scarred myometrium (P < .001). The force that was required to reach the yield point was similar between labor and nonlabor groups (P = .216). Likewise, a previous lower uterine segment scar did not alter the yield point. The break point was similar among all groups (P = .317). Sulfated glycosaminoglycan levels were unaffected by labor or scarring (P = .354). Scarred lower uterine segment myometrium had a higher collagen content compared with unscarred myometrium specimens that were obtained during labor (P = .025). Although there were similar degrees of collagen cross- linking among groups (P = .212), there was lower collagen birefringence in myometrium from laboring women compared with nonlaboring women (P < .001). Conclusion: Labor alters the viscoelastic properties of myometrium. Lower uterine segment myometriumis stiffest in women with dysfunctional labor compared with nonlabor control subjects. Labor and scarring also alter the pattern of collagen birefringence. Similar collagen cross- linking among the study groups may explain the reason that the breaking strength of the tissue is not altered by the state of labor and the reason that the rupture of the uterine scar is a rare event.
文摘中国的粮食安全、水资源和水环境近60年来发生了深刻变迁.长期以来人们对这三者的演化关系缺乏定量化理解.文章在回顾国内外研究进展的基础上,结合1955~2014年全国粮食作物模拟、灌溉发展和氮素平衡等最新研究,归纳得到如下认识:(1)灌溉对减小中国农业旱灾风险贡献了(31±2)%.在过去60年中对粮食产量年际波动影响最大的不是气候,而是社会经济因素.(2)自1955年来,化肥氮对当前粮食产量贡献了(45±3)%,灌溉发展和化肥氮的耦合贡献为(47±3)%.(3)灌溉和农业生产水平的提高加强了中国粮食系统的稳定性.在保障粮食种植面积的情况下,即使遭受到百年一遇的旱灾,全国自产粮食的人均占有量也可达到约3200k Cal d^-1的高水平供给.(4)丰水与平水年景杜绝北方地下水超采不会影响中国的粮食安全水平.1999~2014年地下水超采对粮食平均贡献仅为3%左右.但北方地下水枯竭将产生灾难性后果.(5)未来气候变化可导致极端农业旱灾风险增加.(6)根据氮流失模拟结果和水体氮浓度观测数据,全国淡水环境的氮容量安全阈值为(520±70)万t a^-1,但目前氮排放量达到(1450±310)万t a^-1.其中有14个省的农田氮流失超过了自身阈值,主要分布在缺水的北方.(7)提高农田管理水平可减小220~240万吨的农田氮流失,仅占全国水体氮总超排量的24~26%.(8)当前污水处理体系也无法解决中国的氮污染问题.2014年全国城市生活污水处理厂的除氮量仅为70万吨左右.(9)解决当前氮污染问题的唯一有效途径是重构城乡养分循环体系;若要将氮流失限制在安全阈值内,需要在提高农田氮肥利用效率基础上,把全国有机废物还田率从当前的40%以下提高到86%以上,其中9个省份需要达到95%以上.中国如果要实现农业、水资源和水环境的可持续发展,应在统一的科学框架下制定部门间相互协调的长远规划和行动方案.在改进农村土地流转制的基础上建立新型规模化农业经营制度,制定弃耕地的复耕政策、明确省级粮食生产责任制,扭转粮食重心持续北移的格局,恢复北方地下水储量,增强水体自净功能.重构城乡养分循环体系的经济成本远低于污水处理和环境退化成本.以2010年价格计,基础设施建设约需7000亿元,年运行成本约1200~1900亿元.这可以通过重新统筹分散在农业、环保、水利、城乡建设等行业的环保和污染治理资金予以解决,让农民成为这一体系的主要参与者和受益者.针对人类共同面临的水-氮管理难题,中国完全有可能在保障粮食安全的条件下探索出独特的可持续发展之路.
