Hepatitis E virus(HEV)is hyperendemic in South Asia and Africa accounting for half of total Global HEV burden.There are eight genotypes of HEV.Among them,the four common ones known to infect humans,genotypes 1 and 2 a...Hepatitis E virus(HEV)is hyperendemic in South Asia and Africa accounting for half of total Global HEV burden.There are eight genotypes of HEV.Among them,the four common ones known to infect humans,genotypes 1 and 2 are prevalent in the developing world and genotypes 3 and 4 are causing challenge in the industrialized world.Asymptomatic HEV viremia in the general population,especially among blood donors,has been reported in the literature worldwide.The clinical implications related to this asymptomatic viremia are unclear and need further exploration.Detection of viremia due to HEV genotype 1 infection,apparently among healthy blood donors is also reported without much knowledge about its infection rate.Similarly,while HEV genotype 3 is known to be transmitted via blood transfusion in humans and has been subjected to screening in many European nations,instances of transmission have also been documented albeit without significant clinical consequences.Epidemiology of HEV genotype 1 in endemic areas often show waxing and waning pattern.Occasional sporadic occurrence of HEV infection interrupted by outbreaks have been frequently seen.In absence of known animal reservoir,where HEV exists in between outbreak is a mystery that needs further exploration.However,occurrence of asymptomatic HEV viremia due to HEV genotype 1 during epidemiologically quiescent period may explain that this phenomenon may act as a dynamic reservoir.Since HEV genotype 1 infection cannot cause chronicity,subclinical transient infection and transmission of virus might be the reason it sustains in interepidemic period.This might be the similar phenomenon with SARS COVID-19 corona virus infection which is circulating worldwide in distinct phases with peaks and plateaus despite vaccination against it.In view of existing evidence,we propose the concept of“Dynamic Human Reservoir.”Quiescent subclinical infection of HEV without any clinical consequences and subsequent transmission may contribute to the existence of the virus in a community.The potential for transmitting HEV infection by asymptomatic HEV infected individuals by fecal shedding of virus has not been reported in literature.This missing link may be a key to Pandora's box in understanding epidemiology of HEV infection in genotype 1 predominant region.展开更多
Reservoirs,as artificial lakes,suffer from silting inevitably since being constructed,the sediments from surrounding environment can provide a continuous record of environmental change.Shilianghe Reservoir,the largest...Reservoirs,as artificial lakes,suffer from silting inevitably since being constructed,the sediments from surrounding environment can provide a continuous record of environmental change.Shilianghe Reservoir,the largest artificial lake in Jiangsu Province,was constructed in 1959,and plays an important role in flood control,irrigation,water supply,and so on.Nevertheless,the silting situation of the reservoir is also quite serious.In this paper,the grain-size distribution of core from Shilianghe Reservoir and its response to environmental changes were studied.It is due to two driving factors:climate variability and human activities.Based on the analysis of the grain size distribution data,the sediments were mainly composed of clayey silt and silty clay with a clear tendency of upward fining.But a grain-size peak appeared at 86 cm,and the sand proportion was also very big,indicating that hydrodynamic force was stronger.There was a consistent trend of change between sediment record in Shilianghe Reservoir and historical precipitation in the basin.According to the dating mark of137 Cs,it can be determined primarily that the abnormal grain-size at 86 cm reflected possibly the rainstorm and flood event occurring in 1970.Human activities reduced the hydrodynamics of depositional environment.Hydraulic projects are direct human activities,and land use/cover changes are indirect human activities.It turned out that sediment yield and sediment load were more and more less,and sedimentation rate showed a decreasing trend.Furthermore,sediments tended to become smaller and had better sorting property.展开更多
由于受人类活动及气候变化影响,黄河上游干流水沙特征发生显著变化。为探究黄河上游水沙变化情况,基于黄河上游5个水文站19642019年水沙、遥感影像等数据,利用Mann-Kendall检验法、滑动t检验法、累积距平曲线和双累积曲线等突变检验方...由于受人类活动及气候变化影响,黄河上游干流水沙特征发生显著变化。为探究黄河上游水沙变化情况,基于黄河上游5个水文站19642019年水沙、遥感影像等数据,利用Mann-Kendall检验法、滑动t检验法、累积距平曲线和双累积曲线等突变检验方法和小波分析法,对黄河上游水沙变化特征进行研究。利用水沙关系曲线及线性回归法等方法估算人类活动和气候对水沙变化的贡献率,并着重讨论梯级水库建设及土地利用变化对水沙的影响。结果表明:1)黄河上游玛曲-小川段流域内降雨量和径流量变化幅度不明显,贵德站、循化站、小川站19862019年年均输沙量分别减至19641985年的9.8%、24.6%、38.8%,输沙量大大减少。黄河上游玛曲-小川段径流量突变多在1986年,输沙量突变多在1969、1986、2004年,径流量存在8、16、22 a周期,输沙量存在4~8、18~21、27 a周期。2)1969年后,河流输沙能力增强,水沙关系显著改变。在不同时段内,人类活动对径流量变化在19872019年贡献率为66.3%,对输沙量变化在19701986、19872004、20052019年的贡献率为72.96%、70.73%、69.7%。人类活动对黄河上游干流水沙影响占据主导因素。3)刘家峡水库淤积最为严重,单库运行期水库淤积量为2.39亿t,排沙比变化范围为1.39%~10.7%。梯级水库联调使得径流量在19642004年间减少47.8%,19642019年间梯级水库减沙94.8%,梯级水库对输沙量影响远大于对径流量的影响。4)19802020年间,草地面积增加了1880.03 km 2,增幅3.1%,有利于减少输沙量,草地拦沙效益大于截流效益。展开更多
为准确揭示密云水库流域径流变化的物理成因,基于降水、径流非平稳特征诊断结果,采用SWAT(soil and water assessment tool)水文模型,基于Budyko理论的弹性系数法和水量平衡法揭示该流域径流变化原因;对比验证各模型归因结果差异,进一...为准确揭示密云水库流域径流变化的物理成因,基于降水、径流非平稳特征诊断结果,采用SWAT(soil and water assessment tool)水文模型,基于Budyko理论的弹性系数法和水量平衡法揭示该流域径流变化原因;对比验证各模型归因结果差异,进一步探究归因方法和基准期选择对流域径流变化归因结果的影响。结果表明:基于Budyko理论的水量平衡方法更适用于水利工程众多、跨流域调水活动频繁的密云水库流域径流变化归因计算;利用该方法进行分析,当基准期长度达到16年及以上时,流域径流变化归因分析结果逐渐趋于稳定,而基准期选取过短会高估人类活动对径流的减水效应;此外,基准期选取靠近研究初始时段时,计算得到人类活动的减水效应相对较大。综合考虑上述各因素的影响,认为人类活动是密云水库流域径流变化的主导因素;在变化期Ⅰ,其减水效应在-128.32%~-119.56%波动,在变化期Ⅱ,其对径流的削减作用为-75.58%~-70.70%。研究结果有助于提升对密云水库流域径流复杂演变规律和物理成因的科学认识。展开更多
Analysis of volatile organic compounds (VOCs) and polyaromatic hydrocarbons (PAHs) in the Barker Reservoir in Houston, Texas, United States is reported. Samples were collected within one week after the August 2017 Hur...Analysis of volatile organic compounds (VOCs) and polyaromatic hydrocarbons (PAHs) in the Barker Reservoir in Houston, Texas, United States is reported. Samples were collected within one week after the August 2017 Hurricane Harvey. Using a gas chromatograph equipped with a mass spectrometer, 4 VOCs and 13 PAHs were found in the Barker Reservoir. Concentrations of acetone, benzene, chloroform, and toluene were 1500, 380, 830, and 290 parts per million (ppm), respectively. Benzene and chloroform are classified as probable human carcinogens by the U.S. Environmental Protection Agency (EPA). Six PAHs including benzo[a]anthracene, benzo[a]pyrene, benzo[b]fluoranthene, benzo[k]fluoranthene, chrysene, and dibenz[a,h]anthracene are probable human carcinogens. The most concentrated PAH was acenaphthylene at 0.068 ppm, while the least one was fluoranthene at 0.00046 ppm. Results revealed water contaminants in Houston and its vicinities during the flooding season and served as references for water monitoring purposes in the future.展开更多
While human immunodeficiency virus 1(HIV-1) infectionis controlled through continuous, life-long use of a combination of drugs targeting different steps of the virus cycle, HIV-1 is never completely eradicated from th...While human immunodeficiency virus 1(HIV-1) infectionis controlled through continuous, life-long use of a combination of drugs targeting different steps of the virus cycle, HIV-1 is never completely eradicated from the body. Despite decades of research there is still no effective vaccine to prevent HIV-1 infection. Therefore, the possibility of an RNA interference(RNAi)-based cure has become an increasingly explored approach. Endogenous gene expression is controlled at both, transcriptional and post-transcriptional levels by noncoding RNAs, which act through diverse molecular mechanisms including RNAi. RNAi has the potential to control the turning on/off of specific genes through transcriptional gene silencing(TGS), as well as finetuning their expression through post-transcriptional gene silencing(PTGS). In this review we will describe in detail the canonical RNAi pathways for PTGS and TGS, the relationship of TGS with other silencing mechanisms and will discuss a variety of approaches developed to suppress HIV-1 via manipulation of RNAi. We will briefly compare RNAi strategies against other approaches developed to target the virus, highlighting their potential to overcome the major obstacle to finding a cure, which is the specific targeting of the HIV-1 reservoir within latently infected cells.展开更多
近年来,全球气候变化和人为活动日益剧烈,研究陆地水储量动态变化的影响因素,有助于深入了解陆地水储量的时空分布规律,为区域水资源管理和保护提供依据。基于(Gravity Recovery And Climate Experiment)GRACE数据及8种气候要素,采用趋...近年来,全球气候变化和人为活动日益剧烈,研究陆地水储量动态变化的影响因素,有助于深入了解陆地水储量的时空分布规律,为区域水资源管理和保护提供依据。基于(Gravity Recovery And Climate Experiment)GRACE数据及8种气候要素,采用趋势分析、互相关分析和偏最小二乘回归(Partial least squares regression,PLSR)等,从网格尺度(1o×1o)上分析我国云南、贵州、四川、广西、湖南、湖北以及重庆7省市陆地水储量距平(Terrestrial Water Storage Anomaly,TWSA)变化趋势及其不同时间尺度下的主要影响因素。结果表明:2002-2017年期间,我国南方7省市除西部区域外TWSA总体上呈现明显增长的趋势,在重庆、贵州、湖北和湖南省交界处上升幅度最大,平均增幅最大可达每年0.9 cm,该区域TWSA动态变化由长期趋势主导。云南、四川中南部、广西南部以及湖南湖北二省的东部区域中,TWSA随时间变化由季节周期性变化所主导。月尺度下,TWSA与空气比湿的动态变化最为相似,85%网格TWSA的变化受气候波动控制,仅研究区中北部TWSA明显受到大型水库消峰填谷调控的影响,其季节波动弱于其他地区,但水库对该区域TWSA年尺度的变化影响明显减弱。年尺度下,全区域TWSA的变化仍主要受气候因素的影响,陆地水储量60%以上的变化可由气候变化解释,降雨为七成以上研究区域TWSA年尺度变化的主控要素,仅三峡水库附近TWSA受到人为活动和气候变化的共同影响。展开更多
文摘Hepatitis E virus(HEV)is hyperendemic in South Asia and Africa accounting for half of total Global HEV burden.There are eight genotypes of HEV.Among them,the four common ones known to infect humans,genotypes 1 and 2 are prevalent in the developing world and genotypes 3 and 4 are causing challenge in the industrialized world.Asymptomatic HEV viremia in the general population,especially among blood donors,has been reported in the literature worldwide.The clinical implications related to this asymptomatic viremia are unclear and need further exploration.Detection of viremia due to HEV genotype 1 infection,apparently among healthy blood donors is also reported without much knowledge about its infection rate.Similarly,while HEV genotype 3 is known to be transmitted via blood transfusion in humans and has been subjected to screening in many European nations,instances of transmission have also been documented albeit without significant clinical consequences.Epidemiology of HEV genotype 1 in endemic areas often show waxing and waning pattern.Occasional sporadic occurrence of HEV infection interrupted by outbreaks have been frequently seen.In absence of known animal reservoir,where HEV exists in between outbreak is a mystery that needs further exploration.However,occurrence of asymptomatic HEV viremia due to HEV genotype 1 during epidemiologically quiescent period may explain that this phenomenon may act as a dynamic reservoir.Since HEV genotype 1 infection cannot cause chronicity,subclinical transient infection and transmission of virus might be the reason it sustains in interepidemic period.This might be the similar phenomenon with SARS COVID-19 corona virus infection which is circulating worldwide in distinct phases with peaks and plateaus despite vaccination against it.In view of existing evidence,we propose the concept of“Dynamic Human Reservoir.”Quiescent subclinical infection of HEV without any clinical consequences and subsequent transmission may contribute to the existence of the virus in a community.The potential for transmitting HEV infection by asymptomatic HEV infected individuals by fecal shedding of virus has not been reported in literature.This missing link may be a key to Pandora's box in understanding epidemiology of HEV infection in genotype 1 predominant region.
基金Supported by the National Natural Science Foundation of China(41501003,41807403)Open Foundation of Research Institute of Jiangsu Coastal Development(RIJCD11008)+1 种基金Teaching Reform Foundation of Yancheng Teachers University(12YCTCJY050,2018YCTUJGY021)Provincial Undergraduate Training Program for Innovation and Entrepreneurship of Jiangsu(201810324010Y)
文摘Reservoirs,as artificial lakes,suffer from silting inevitably since being constructed,the sediments from surrounding environment can provide a continuous record of environmental change.Shilianghe Reservoir,the largest artificial lake in Jiangsu Province,was constructed in 1959,and plays an important role in flood control,irrigation,water supply,and so on.Nevertheless,the silting situation of the reservoir is also quite serious.In this paper,the grain-size distribution of core from Shilianghe Reservoir and its response to environmental changes were studied.It is due to two driving factors:climate variability and human activities.Based on the analysis of the grain size distribution data,the sediments were mainly composed of clayey silt and silty clay with a clear tendency of upward fining.But a grain-size peak appeared at 86 cm,and the sand proportion was also very big,indicating that hydrodynamic force was stronger.There was a consistent trend of change between sediment record in Shilianghe Reservoir and historical precipitation in the basin.According to the dating mark of137 Cs,it can be determined primarily that the abnormal grain-size at 86 cm reflected possibly the rainstorm and flood event occurring in 1970.Human activities reduced the hydrodynamics of depositional environment.Hydraulic projects are direct human activities,and land use/cover changes are indirect human activities.It turned out that sediment yield and sediment load were more and more less,and sedimentation rate showed a decreasing trend.Furthermore,sediments tended to become smaller and had better sorting property.
文摘由于受人类活动及气候变化影响,黄河上游干流水沙特征发生显著变化。为探究黄河上游水沙变化情况,基于黄河上游5个水文站19642019年水沙、遥感影像等数据,利用Mann-Kendall检验法、滑动t检验法、累积距平曲线和双累积曲线等突变检验方法和小波分析法,对黄河上游水沙变化特征进行研究。利用水沙关系曲线及线性回归法等方法估算人类活动和气候对水沙变化的贡献率,并着重讨论梯级水库建设及土地利用变化对水沙的影响。结果表明:1)黄河上游玛曲-小川段流域内降雨量和径流量变化幅度不明显,贵德站、循化站、小川站19862019年年均输沙量分别减至19641985年的9.8%、24.6%、38.8%,输沙量大大减少。黄河上游玛曲-小川段径流量突变多在1986年,输沙量突变多在1969、1986、2004年,径流量存在8、16、22 a周期,输沙量存在4~8、18~21、27 a周期。2)1969年后,河流输沙能力增强,水沙关系显著改变。在不同时段内,人类活动对径流量变化在19872019年贡献率为66.3%,对输沙量变化在19701986、19872004、20052019年的贡献率为72.96%、70.73%、69.7%。人类活动对黄河上游干流水沙影响占据主导因素。3)刘家峡水库淤积最为严重,单库运行期水库淤积量为2.39亿t,排沙比变化范围为1.39%~10.7%。梯级水库联调使得径流量在19642004年间减少47.8%,19642019年间梯级水库减沙94.8%,梯级水库对输沙量影响远大于对径流量的影响。4)19802020年间,草地面积增加了1880.03 km 2,增幅3.1%,有利于减少输沙量,草地拦沙效益大于截流效益。
文摘为准确揭示密云水库流域径流变化的物理成因,基于降水、径流非平稳特征诊断结果,采用SWAT(soil and water assessment tool)水文模型,基于Budyko理论的弹性系数法和水量平衡法揭示该流域径流变化原因;对比验证各模型归因结果差异,进一步探究归因方法和基准期选择对流域径流变化归因结果的影响。结果表明:基于Budyko理论的水量平衡方法更适用于水利工程众多、跨流域调水活动频繁的密云水库流域径流变化归因计算;利用该方法进行分析,当基准期长度达到16年及以上时,流域径流变化归因分析结果逐渐趋于稳定,而基准期选取过短会高估人类活动对径流的减水效应;此外,基准期选取靠近研究初始时段时,计算得到人类活动的减水效应相对较大。综合考虑上述各因素的影响,认为人类活动是密云水库流域径流变化的主导因素;在变化期Ⅰ,其减水效应在-128.32%~-119.56%波动,在变化期Ⅱ,其对径流的削减作用为-75.58%~-70.70%。研究结果有助于提升对密云水库流域径流复杂演变规律和物理成因的科学认识。
文摘Analysis of volatile organic compounds (VOCs) and polyaromatic hydrocarbons (PAHs) in the Barker Reservoir in Houston, Texas, United States is reported. Samples were collected within one week after the August 2017 Hurricane Harvey. Using a gas chromatograph equipped with a mass spectrometer, 4 VOCs and 13 PAHs were found in the Barker Reservoir. Concentrations of acetone, benzene, chloroform, and toluene were 1500, 380, 830, and 290 parts per million (ppm), respectively. Benzene and chloroform are classified as probable human carcinogens by the U.S. Environmental Protection Agency (EPA). Six PAHs including benzo[a]anthracene, benzo[a]pyrene, benzo[b]fluoranthene, benzo[k]fluoranthene, chrysene, and dibenz[a,h]anthracene are probable human carcinogens. The most concentrated PAH was acenaphthylene at 0.068 ppm, while the least one was fluoranthene at 0.00046 ppm. Results revealed water contaminants in Houston and its vicinities during the flooding season and served as references for water monitoring purposes in the future.
文摘While human immunodeficiency virus 1(HIV-1) infectionis controlled through continuous, life-long use of a combination of drugs targeting different steps of the virus cycle, HIV-1 is never completely eradicated from the body. Despite decades of research there is still no effective vaccine to prevent HIV-1 infection. Therefore, the possibility of an RNA interference(RNAi)-based cure has become an increasingly explored approach. Endogenous gene expression is controlled at both, transcriptional and post-transcriptional levels by noncoding RNAs, which act through diverse molecular mechanisms including RNAi. RNAi has the potential to control the turning on/off of specific genes through transcriptional gene silencing(TGS), as well as finetuning their expression through post-transcriptional gene silencing(PTGS). In this review we will describe in detail the canonical RNAi pathways for PTGS and TGS, the relationship of TGS with other silencing mechanisms and will discuss a variety of approaches developed to suppress HIV-1 via manipulation of RNAi. We will briefly compare RNAi strategies against other approaches developed to target the virus, highlighting their potential to overcome the major obstacle to finding a cure, which is the specific targeting of the HIV-1 reservoir within latently infected cells.
文摘近年来,全球气候变化和人为活动日益剧烈,研究陆地水储量动态变化的影响因素,有助于深入了解陆地水储量的时空分布规律,为区域水资源管理和保护提供依据。基于(Gravity Recovery And Climate Experiment)GRACE数据及8种气候要素,采用趋势分析、互相关分析和偏最小二乘回归(Partial least squares regression,PLSR)等,从网格尺度(1o×1o)上分析我国云南、贵州、四川、广西、湖南、湖北以及重庆7省市陆地水储量距平(Terrestrial Water Storage Anomaly,TWSA)变化趋势及其不同时间尺度下的主要影响因素。结果表明:2002-2017年期间,我国南方7省市除西部区域外TWSA总体上呈现明显增长的趋势,在重庆、贵州、湖北和湖南省交界处上升幅度最大,平均增幅最大可达每年0.9 cm,该区域TWSA动态变化由长期趋势主导。云南、四川中南部、广西南部以及湖南湖北二省的东部区域中,TWSA随时间变化由季节周期性变化所主导。月尺度下,TWSA与空气比湿的动态变化最为相似,85%网格TWSA的变化受气候波动控制,仅研究区中北部TWSA明显受到大型水库消峰填谷调控的影响,其季节波动弱于其他地区,但水库对该区域TWSA年尺度的变化影响明显减弱。年尺度下,全区域TWSA的变化仍主要受气候因素的影响,陆地水储量60%以上的变化可由气候变化解释,降雨为七成以上研究区域TWSA年尺度变化的主控要素,仅三峡水库附近TWSA受到人为活动和气候变化的共同影响。
