风力涡轮机制造商0tt公司在生产带有特殊内齿轮的2500mm空心齿轮时,不仅要依靠专业人员还要依靠Kapp Niles的大型、坚固耐用和高精度的成形磨齿机。位于德国图宾根博德尔豪森的Zahnradfertigung Ott GmbH&Co.KG成立于1957年,现有员...风力涡轮机制造商0tt公司在生产带有特殊内齿轮的2500mm空心齿轮时,不仅要依靠专业人员还要依靠Kapp Niles的大型、坚固耐用和高精度的成形磨齿机。位于德国图宾根博德尔豪森的Zahnradfertigung Ott GmbH&Co.KG成立于1957年,现有员工156人,厂房面积达1万m^(2),生产范围包括工业、运输、物流、石油和天然气开采领域的各种齿轮和传动装置。展开更多
Emerging infectious diseases are a major threat to biodiversity and an important public health issue.Flaviviruses are the cause of several emerging vector-borne zoonotic arboviruses whose distribution is currently inc...Emerging infectious diseases are a major threat to biodiversity and an important public health issue.Flaviviruses are the cause of several emerging vector-borne zoonotic arboviruses whose distribution is currently increasing in Europe.The evidence that West Nile virus(WNV)circulates in resident and migratory species has implications for both animal and public health and should therefore be studied in depth.USUTU(USUV),Bagaza(BAGV)and tick-borne encephalitis virus(TBEV)are other viruses that are beginning to spread more widely.An integrated surveillance program,namely in birds,is essential for reducing the risk of infection in human populations within the One Health principles.In the present study,wild birds admitted to wildlife rehabilitation centers in Portugal were sampled.Two hundred eight blood samples were assayed serologically for antibodies to flaviviruses by using a commercial ELISA kit.An over-all seroprevalence of 19.6%(95%confidence interval[CI]:13.7-26.7%)was observed.Antibodies against flaviviruses were detected in 13(35.1%)different species of wild birds.Accipitriformes(26.7%;95%CI:18.5-36.2%)and Strigi-formes(26.7%;95%CI:14.6-42.0%)were the orders with the highest seroprevalence rates recorded.There were no statistically significant differences(p=0.725)between the geographical regions(NUTSⅡ)studied,but a statistically significant difference(p=0.017)was found between sex(male:34.4%;female:4.8%).A higher seroprevalence was detected in adults(32.1%)than in juvenile birds(9.3%)(p=0.014),and age was considered a risk factor for flavivirus infection in wild birds(odds ratio 1.4;95%CI:0.5-4.0).More epidemiological studies are needed in Portugal since the actual spread of the genus Flavivirus throughout the country is unknown.展开更多
From the Yangtze to the Nile,a shared vision for world heritage protection is charting a new course in global cultural cooperation Thousands of kilometres apart,two ancient hydrological relics-the White Crane Ridge(Ba...From the Yangtze to the Nile,a shared vision for world heritage protection is charting a new course in global cultural cooperation Thousands of kilometres apart,two ancient hydrological relics-the White Crane Ridge(Baiheliang)in the middle of the Yangtze River in Chongqing and the Nilometers on Rhoda Island in Cairo-stand as silent witnesses to humanity’s interaction with nature across centuries.展开更多
Microplastics(MPs)have been widely detected in marine environments,yet the pollution in terrestrial fresh waters in economically underdeveloped and remote areas is poorly understood.We investigated the abundance and d...Microplastics(MPs)have been widely detected in marine environments,yet the pollution in terrestrial fresh waters in economically underdeveloped and remote areas is poorly understood.We investigated the abundance and distribution of MPs in inland waters(including open waters in river,lake,reservoir,stream,and tap water and bottled water)in Guizhou,SW China,detected by Nile Red staining.Results show that MPs were detected in all samples,with the mean abundance of 3.5±1.9 items/mL in 34river water samples,3.9±1.9 items/mL in 14 lake and reservoir water samples,3.4±2.4 items/mL in 87 stream water samples,3.8±3.8 items/mL in 164 tap water samples,and 1.3±3.2 items/mL in 12 bottled water samples from 4 different brands.The MP abundance in open field waters(3.6±3.0 items/mL)was significantly higher than that in bottled water(1.3±3.2 items/mL)(P<0.05).The microplastics with particle sizes of 10-20μm accounted for more than 50%of all samples.The composition ratio of smalland medium-sized microplastics in open waters was higher than in tap and bottled water(P<0.05).The MPs abundance tended to increase with the decrease in particle size.Therefore,microplastic pollution varied in different degrees in open waters in economically underdeveloped and remote areas of the southwestern China,which is consistent with microplastic pollution in other similar water environments.This study provided a reference for understanding the microplastic content and pollution control in the inland waters in western and remote areas of China.展开更多
In order to understand the transmission mechanism of West Nile virus(WNv)in birds(especially crows)and mosquitoes populations,this paper extends the traditional ordinary differential model of WNv to a reaction-diffusi...In order to understand the transmission mechanism of West Nile virus(WNv)in birds(especially crows)and mosquitoes populations,this paper extends the traditional ordinary differential model of WNv to a reaction-diffusion system with more complex cross-diffusion.We explore the relationship between the basic reproduction number and cross-diffusion coefficients involving various parameters,and investigate the effect of vertical transmission of the virus on the transmission mechanism.We use the method of upper and lower solutions to investigate the existence of the coexistence solutions.The theoretical analysis and numerical simulation show that the WNv carried by birds and mosquitoes will coexist when the low-risk threshold R0*≥1,which is a disadvantage to the prevention and control of this virus,and disappear when the high-risk threshold R*0≤1,which is an advantage to that.展开更多
Organic luminophores with superior solid-state luminescence are urgently required in various fields,such as lighting,display,sensing,and solar energy conversion.However,to achieve their highly efficient luminescence s...Organic luminophores with superior solid-state luminescence are urgently required in various fields,such as lighting,display,sensing,and solar energy conversion.However,to achieve their highly efficient luminescence still remains a challenge.Herein,a newly designed Nile red derivative,Nile-DPA-VB,is successfully obtained to exhibit aggregation-induced emission characteristics with the photoluminescent quantum yield(PLQY)of 11.45%.Such PLQY could be further promoted to 53.45%when Nile-DPA-VB is polymerized undergoing precipitation polymerization process,where the confined aggregation microenvironment severely restricts the intramolecular motions of Nile-DPA-VB.Remarkably,Nile-DPA-VB is ultrasensitive to the polarity and steric effect,enabling the real-time monitoring of aggregation microenvironment evolution for precipitation polymerization.The microphase separation and dynamic hardening for the nucleation and growth processes are visually demonstrated,which contribute dominantly to the high-efficiency luminescence.Finally,by doping the as-prepared fluorescent polymeric particles into polymethyl methacrylate,functional films with high luminescence and high haze are achieved to show the potential in lighting.These findings clearly demonstrate the significant role of polymerization in constructing high-efficiency solid-state luminescent materials for practice.展开更多
The NEW GIFT Nile tilapia （Oreochromis niloticus niloticus L.） is a nationally certificated new strain selected over 14 years and 9 generations from the base strain of GIFT Nile tilapia, introduced in 1994. This new...The NEW GIFT Nile tilapia （Oreochromis niloticus niloticus L.） is a nationally certificated new strain selected over 14 years and 9 generations from the base strain of GIFT Nile tilapia, introduced in 1994. This new variety has been extended in most of areas of China. The management of genetically improved strains, including the genetic markers for identification is needed urgently. RAPD analysis was conducted and their conversion to SCAR markers was developed. From NEW GIFT Nile tilapia, two strain-specific RAPD bands, S304624 bp and S36568 bp were identified. The strain-specific RAPD bands were gel-purified, cloned, and sequenced. Locus-specific primers were then designed to amplify the strain-specific bands. PCR amplification was conducted to test the variations in allele frequencies of two converted SCAR markers among the NEW GIFT Nile tilapia and its base strains, as well as 7 additional farmed strains worldwide. The frequency of SCAR marker Ⅰ （553 bp） was 85.7% in NEW GIFT Nile tilapia, but 16.7% in the base strain. The frequency of SCAR marker Ⅱ （558 bp） was 91.4% in NEW GIFT Nile tilapia, but 0% 70% in the 7 other strains. In order to confirm the utility of these two markers, an examination was conducted for a wild population from Egypt, resulted the frequency of SCAR Ⅰ and Ⅱ was 10% and 70%, respectively, much lower than that of New GIFT strain. The increase in allele frequency of these two SCAR markers suggests that these markers might be genetically linked to the quantitative trait loci （QTL） underlining the performance traits by long term selection, and indicate the bright potential of SCAR marker technology for tracking generations during selection progress and for distinguishing among genetically improved strain and other strains.展开更多
借助扫描电镜和透射电镜对尼罗罗非鱼（Oreochromis niloticus）、奥利亚罗非鱼（O.aureus）、奥尼罗非鱼（O.niloticus×O.aureus）和吉富罗非鱼（GIFT Strain in Nile Tilapia,O.niloticus）成熟精子的超微结构进行了比较研究。...借助扫描电镜和透射电镜对尼罗罗非鱼（Oreochromis niloticus）、奥利亚罗非鱼（O.aureus）、奥尼罗非鱼（O.niloticus×O.aureus）和吉富罗非鱼（GIFT Strain in Nile Tilapia,O.niloticus）成熟精子的超微结构进行了比较研究。结果显示,4种罗非鱼精子均为有鞭毛精子,无顶体,尾部轴丝9±2型。尼罗罗非鱼精子植入窝陷入核深度最浅,线粒体个数和平均直径分别为5-9个、（0.36±0.10）μm,鞭毛侧鳍平均翼长为（0.29±0.11）μm;奥利亚罗非鱼精子核内染色质着色程度最深,植入窝陷入核深度约1/3,线粒体个数和平均直径分别为3-10个、（0.40±0.17）μm,鞭毛侧鳍平均翼长为（0.32±0.12）μm;奥尼罗非鱼精子核内染色质着色程度较浅,植入窝陷入核深度约1/3,线粒体个数和平均直径分别为5-7个、（0.32±0.09）μm,鞭毛侧鳍平均翼长（0.26±0.09）μm;吉富罗非鱼精子核内染色质着色最浅,植入窝陷入核最深,约占2/3,线粒体个数和平均直径分别为5-10个、（0.37±0.08）μm,中段存在大量中空囊泡,鞭毛侧鳍平均翼长为（0.15±0.03）μm,与其它三种罗非鱼精子鞭毛平均侧鳍翼长比较具显著性差异（P〈0.05）。展开更多
The International Association of Hydrological Sciences （IAHS） recognized the lack of hydro- logical data as a world-wide problem in 2002 and adopted the Prediction of Ungauged Basins （PUB） as a decadal research ag...The International Association of Hydrological Sciences （IAHS） recognized the lack of hydro- logical data as a world-wide problem in 2002 and adopted the Prediction of Ungauged Basins （PUB） as a decadal research agenda during the period of 2003 to 2012. One of the objectives is to further develop methodologies for prediction in ungauged basins and to reduce uncertainties in model prediction. Estimation of stream flows is required for flood control, water quality control, valley habitat assessment and water budget of a country. However, the majority of water catchments, streams and valleys are ungauged in most developing countries. The main objective of this paper is to introduce the IHACRES （Identification of Hy- drographs and Components from Rainfall, Evaporation and Stream） model into African hydrological plan- ning as a methodology for water resources assessment, which in turn can be used to resolve water conflicts between communities and countries and to study the climate change issues. This is because the IHACRES model is applied for the estimation of flows in ungauged catchments whose physical catchments descriptors （PCDs） can be determined by driving variables （i.e. rainfall and temperature）; and also in gauged streams but whose gauging stations are no longer operational but historical data are available for model calibration. The model provides a valuable insight into the hydrologic behaviour of the upper water sources for valleys as well as provides a useful methodology for water resources assessment in situations of scarce financial resources in developing countries. In addition, it requires relatively few parameters in its calibration and has been successful applied in previous regionalization studies. It will also make possible the equitable distri- bution of water resources in international basins and rivers＇ catchments. This paper does not apply the model anywhere, but recommends it as a methodology for water resources assessment in order to cure water conflicts on the African continent.展开更多
Water quality of the river Nile and trace elements of the water, sediments and fish tissues were investigated in the current work. Eighteen different sampling points were selected along the whole course of the River N...Water quality of the river Nile and trace elements of the water, sediments and fish tissues were investigated in the current work. Eighteen different sampling points were selected along the whole course of the River Nile from its spring at Aswan to its estuaries at Rosetta and Damietta. Higher mean value of conductivity, alkalinity, chemical oxygen demand (COD), total organic carbon (TOC), ammonia (NH3), nitrate (NO3), total solid (TS), sulphate (SO4), chloride (Cl), orthophosphate were recorded in the water of Damietta and Rosetta branches comparing to other sites. Also trace metals in the water, sediments and tissues of Clarias gariepinus increased significantly (P Fe > Cu > Pb > Mn > Cr> Cd > Hg. In the gill tissues theses metals were accumulated in the following order Fe > Zn > Mn > Pb > Cr > Cu > Cd> Hg. The low accumulation of metals in muscle may be due to lack of binding affinity of these metals with the proteins of muscle. This is particularly important because muscles contribute the greatest mass of the flesh that is consumed as food.展开更多
River Nile is one of the longest transboundery rivers and it is shared and used by Burundi,Democratic Republic of Congo,Egypt,Ethiopia,Eritrea,Kenya,Rwanda,Sudan,Tanzania and Uganda.As of today,the Nile is a crucial r...River Nile is one of the longest transboundery rivers and it is shared and used by Burundi,Democratic Republic of Congo,Egypt,Ethiopia,Eritrea,Kenya,Rwanda,Sudan,Tanzania and Uganda.As of today,the Nile is a crucial resource for the economic development of the Nile Basin countries and a vital source of livelihood for 160 million inhabitants as well as 300 million people living in the 10 riparian countries.The Nile Basin Initiative(NBI) is one of the international cooperative river basin management program and regional partnership where all the Nile Basin countries except Eritrea unite to pursue long-term sustainable development,improved land use practices and management.This review therefore focused on the challenges not faced on NBI in terms of integrated use of the river and conducted analysis of strengths,weaknesses,opportunities and threats(SWOT) based on secondary data.The result of the review revealed that for decades,the Nile Basin people have been facing many complex environmental,social,economic and political challenges that have made it difficult for the proper management and sustainability of Nile water.The initiative provides training to develop skills in government ministries,non-governmental organizations and local communities in each country.It is also working to raise awareness of critical environmental issues by strengthening networks of environmental education practitioners;developing curriculum in the education sector.The challenges of NBI include the involvement and funding of World Bank,lack of sufficient staff,procedural and policies conflicts,lack of coordination and linkage with other regional institutions and lack of recognition as river basin organization.Considering the complex nature of the project,it is recommended that the NBI should come up with a strong multi-disciplinary monitoring and evaluation team to follow up all implemented projects.The NBI should carry out participatory land use planning in communities along the river basin.Moreover,livelihood analysis should be carried out especially in communities along the Nile to come up with poverty eradication projects which are socially acceptable,applicable,economically viable and affordable.展开更多
Objectives The main objective of the present article is to assess and evaluate the characteristics of the Nile water system , and identify the major sources of pollution and its environmental and health consequences. ...Objectives The main objective of the present article is to assess and evaluate the characteristics of the Nile water system , and identify the major sources of pollution and its environmental and health consequences. The article is also aimed to highlight the importance of water management via re-use and recycle of treated effluents for industrial purpose and for cultivation of desert land. Method An intensive effort was made by the authors to collect, assess and compile the available data about the River Nile. Physico-chemical analyses were conducted to check the validity of the collected data. For the determination of micro-pollutants, Gas Chromatography (GC) and High Performance Liquid Chromatography (HPLC) were used. Heavy metals were also determined to investigate the level of industrial pollution in the river system. Results The available data revealed that the river receives a large quantity of industrial, agriculture and domestic wastewater. It is worth mentioning that the river is still able to recover in virtually all the locations, with very little exception. This is due to the high dilution ratio. The collected data confirmed the presence of high concentrations of chromium and manganese in all sediment samples. The residues of organo-chlorine insecticides were detected in virtually all locations. However, the levels of such residues are usually below the limit set by the WHO for use as drinking water. The most polluted lakes are Lake Maryut and Lake Manzala. Groundwater pollution is closely related to adjacent (polluted) surface waters. High concentrations of nutrients, E.coli, sulfur, heavy metals, etc. have been observed in the shallow groundwater, largely surpassing WHO standards for drinking water use. Conclusion A regular and continuous monitoring scheme shall be developed for the River Nile system. The environmental law shall be enforced to prohibit the discharge of wastewater (agricultural, domestic or industrial) to River Nile system.展开更多
Urban sprawl is threatening the limited highly fertile land in the Nile delta of Egypt. Landsat TM satellite images of 1984, 1992 and ETM+ of 2006 have been used to study the impact of urban sprawl on agricultural lan...Urban sprawl is threatening the limited highly fertile land in the Nile delta of Egypt. Landsat TM satellite images of 1984, 1992 and ETM+ of 2006 have been used to study the impact of urban sprawl on agricultural land of the Northern Nile delta, Egypt. Visual interpretation using on screen digitizing and change detection techniques were applied for monitoring the urban sprawl. Combining the land capability map and the urban thematic layer using GIS made it possible to point out the risk of urban expansion on the expense of the highly capable soil class. The results show that a total expansion of urban area amounted to 689.20 km2(6.3% of total area) during the study period 1984–2006. The urban expansion during the 1984–2006 was on the expense of the most fertile soils where, the high capable soils(Class I) lost 247.14 km2(2.26 % of total area) and the moderate capable soils lost 32.73 km2(0.3% of total area), while the low capable soils lost only 57.39 km2(0.53% of total area). The urban encroachment over the non capable soils was very limited during the study period 1984–1992, where 7.33 km2 only was lost. The pattern of urban sprawl has been changed during the 1992 to 2006 whereas much larger area(50.64 km2) of the non capable soils was converted to urban. It can be concluded that the urban sprawl is one of the dominant degradation process on the land of Nile Delta.展开更多
文摘风力涡轮机制造商0tt公司在生产带有特殊内齿轮的2500mm空心齿轮时,不仅要依靠专业人员还要依靠Kapp Niles的大型、坚固耐用和高精度的成形磨齿机。位于德国图宾根博德尔豪森的Zahnradfertigung Ott GmbH&Co.KG成立于1957年,现有员工156人,厂房面积达1万m^(2),生产范围包括工业、运输、物流、石油和天然气开采领域的各种齿轮和传动装置。
基金funded by the Portuguese Foundation for Science and Technology(FCT)sup-ported by the projects UIDB/00772/2020(https://doi.org/10.54499/UIDB/00772/2020)。
文摘Emerging infectious diseases are a major threat to biodiversity and an important public health issue.Flaviviruses are the cause of several emerging vector-borne zoonotic arboviruses whose distribution is currently increasing in Europe.The evidence that West Nile virus(WNV)circulates in resident and migratory species has implications for both animal and public health and should therefore be studied in depth.USUTU(USUV),Bagaza(BAGV)and tick-borne encephalitis virus(TBEV)are other viruses that are beginning to spread more widely.An integrated surveillance program,namely in birds,is essential for reducing the risk of infection in human populations within the One Health principles.In the present study,wild birds admitted to wildlife rehabilitation centers in Portugal were sampled.Two hundred eight blood samples were assayed serologically for antibodies to flaviviruses by using a commercial ELISA kit.An over-all seroprevalence of 19.6%(95%confidence interval[CI]:13.7-26.7%)was observed.Antibodies against flaviviruses were detected in 13(35.1%)different species of wild birds.Accipitriformes(26.7%;95%CI:18.5-36.2%)and Strigi-formes(26.7%;95%CI:14.6-42.0%)were the orders with the highest seroprevalence rates recorded.There were no statistically significant differences(p=0.725)between the geographical regions(NUTSⅡ)studied,but a statistically significant difference(p=0.017)was found between sex(male:34.4%;female:4.8%).A higher seroprevalence was detected in adults(32.1%)than in juvenile birds(9.3%)(p=0.014),and age was considered a risk factor for flavivirus infection in wild birds(odds ratio 1.4;95%CI:0.5-4.0).More epidemiological studies are needed in Portugal since the actual spread of the genus Flavivirus throughout the country is unknown.
文摘From the Yangtze to the Nile,a shared vision for world heritage protection is charting a new course in global cultural cooperation Thousands of kilometres apart,two ancient hydrological relics-the White Crane Ridge(Baiheliang)in the middle of the Yangtze River in Chongqing and the Nilometers on Rhoda Island in Cairo-stand as silent witnesses to humanity’s interaction with nature across centuries.
基金Supported by the National Key Research and Development Program of China(Nos.2018YFC1004300,2018YFC1004302)the Science&Technology Program of Guizhou Province(Nos.QKHHBZ[2020]3002,QKHPTRC-GCC[2022]039-1,QKH-J[2022]YB614)+1 种基金the Science&Technology Program of Zunyi City(No.ZHZ[2021]294)the National Innovation Program for College Students in China(No.201910661012)。
文摘Microplastics(MPs)have been widely detected in marine environments,yet the pollution in terrestrial fresh waters in economically underdeveloped and remote areas is poorly understood.We investigated the abundance and distribution of MPs in inland waters(including open waters in river,lake,reservoir,stream,and tap water and bottled water)in Guizhou,SW China,detected by Nile Red staining.Results show that MPs were detected in all samples,with the mean abundance of 3.5±1.9 items/mL in 34river water samples,3.9±1.9 items/mL in 14 lake and reservoir water samples,3.4±2.4 items/mL in 87 stream water samples,3.8±3.8 items/mL in 164 tap water samples,and 1.3±3.2 items/mL in 12 bottled water samples from 4 different brands.The MP abundance in open field waters(3.6±3.0 items/mL)was significantly higher than that in bottled water(1.3±3.2 items/mL)(P<0.05).The microplastics with particle sizes of 10-20μm accounted for more than 50%of all samples.The composition ratio of smalland medium-sized microplastics in open waters was higher than in tap and bottled water(P<0.05).The MPs abundance tended to increase with the decrease in particle size.Therefore,microplastic pollution varied in different degrees in open waters in economically underdeveloped and remote areas of the southwestern China,which is consistent with microplastic pollution in other similar water environments.This study provided a reference for understanding the microplastic content and pollution control in the inland waters in western and remote areas of China.
基金Supported by the Anhui Province Graduate Education Quality Engineering Project(2022jyjxggyj168)Anhui Province Higher Education Provincial-Level Quality Engineering Major Project(2022jcbs020)Anhui Province Higher Education Provincial-Level Quality Engineering General Project(2022jyxm527).
文摘In order to understand the transmission mechanism of West Nile virus(WNv)in birds(especially crows)and mosquitoes populations,this paper extends the traditional ordinary differential model of WNv to a reaction-diffusion system with more complex cross-diffusion.We explore the relationship between the basic reproduction number and cross-diffusion coefficients involving various parameters,and investigate the effect of vertical transmission of the virus on the transmission mechanism.We use the method of upper and lower solutions to investigate the existence of the coexistence solutions.The theoretical analysis and numerical simulation show that the WNv carried by birds and mosquitoes will coexist when the low-risk threshold R0*≥1,which is a disadvantage to the prevention and control of this virus,and disappear when the high-risk threshold R*0≤1,which is an advantage to that.
基金supported by the National Natural Science Foundation of China(52373171,52173154,52221006,22375014)the Beijing Natural Science Foundation Grant(JQ23006),and the Fundamental Research Funds for the Central Universities(ZY2404).
文摘Organic luminophores with superior solid-state luminescence are urgently required in various fields,such as lighting,display,sensing,and solar energy conversion.However,to achieve their highly efficient luminescence still remains a challenge.Herein,a newly designed Nile red derivative,Nile-DPA-VB,is successfully obtained to exhibit aggregation-induced emission characteristics with the photoluminescent quantum yield(PLQY)of 11.45%.Such PLQY could be further promoted to 53.45%when Nile-DPA-VB is polymerized undergoing precipitation polymerization process,where the confined aggregation microenvironment severely restricts the intramolecular motions of Nile-DPA-VB.Remarkably,Nile-DPA-VB is ultrasensitive to the polarity and steric effect,enabling the real-time monitoring of aggregation microenvironment evolution for precipitation polymerization.The microphase separation and dynamic hardening for the nucleation and growth processes are visually demonstrated,which contribute dominantly to the high-efficiency luminescence.Finally,by doping the as-prepared fluorescent polymeric particles into polymethyl methacrylate,functional films with high luminescence and high haze are achieved to show the potential in lighting.These findings clearly demonstrate the significant role of polymerization in constructing high-efficiency solid-state luminescent materials for practice.
基金National Tilapia Industry Technical System(nycytx-48-3)National Tilapia Seed Program(nyhyzx07-044-01)
文摘The NEW GIFT Nile tilapia （Oreochromis niloticus niloticus L.） is a nationally certificated new strain selected over 14 years and 9 generations from the base strain of GIFT Nile tilapia, introduced in 1994. This new variety has been extended in most of areas of China. The management of genetically improved strains, including the genetic markers for identification is needed urgently. RAPD analysis was conducted and their conversion to SCAR markers was developed. From NEW GIFT Nile tilapia, two strain-specific RAPD bands, S304624 bp and S36568 bp were identified. The strain-specific RAPD bands were gel-purified, cloned, and sequenced. Locus-specific primers were then designed to amplify the strain-specific bands. PCR amplification was conducted to test the variations in allele frequencies of two converted SCAR markers among the NEW GIFT Nile tilapia and its base strains, as well as 7 additional farmed strains worldwide. The frequency of SCAR marker Ⅰ （553 bp） was 85.7% in NEW GIFT Nile tilapia, but 16.7% in the base strain. The frequency of SCAR marker Ⅱ （558 bp） was 91.4% in NEW GIFT Nile tilapia, but 0% 70% in the 7 other strains. In order to confirm the utility of these two markers, an examination was conducted for a wild population from Egypt, resulted the frequency of SCAR Ⅰ and Ⅱ was 10% and 70%, respectively, much lower than that of New GIFT strain. The increase in allele frequency of these two SCAR markers suggests that these markers might be genetically linked to the quantitative trait loci （QTL） underlining the performance traits by long term selection, and indicate the bright potential of SCAR marker technology for tracking generations during selection progress and for distinguishing among genetically improved strain and other strains.
文摘借助扫描电镜和透射电镜对尼罗罗非鱼（Oreochromis niloticus）、奥利亚罗非鱼（O.aureus）、奥尼罗非鱼（O.niloticus×O.aureus）和吉富罗非鱼（GIFT Strain in Nile Tilapia,O.niloticus）成熟精子的超微结构进行了比较研究。结果显示,4种罗非鱼精子均为有鞭毛精子,无顶体,尾部轴丝9±2型。尼罗罗非鱼精子植入窝陷入核深度最浅,线粒体个数和平均直径分别为5-9个、（0.36±0.10）μm,鞭毛侧鳍平均翼长为（0.29±0.11）μm;奥利亚罗非鱼精子核内染色质着色程度最深,植入窝陷入核深度约1/3,线粒体个数和平均直径分别为3-10个、（0.40±0.17）μm,鞭毛侧鳍平均翼长为（0.32±0.12）μm;奥尼罗非鱼精子核内染色质着色程度较浅,植入窝陷入核深度约1/3,线粒体个数和平均直径分别为5-7个、（0.32±0.09）μm,鞭毛侧鳍平均翼长（0.26±0.09）μm;吉富罗非鱼精子核内染色质着色最浅,植入窝陷入核最深,约占2/3,线粒体个数和平均直径分别为5-10个、（0.37±0.08）μm,中段存在大量中空囊泡,鞭毛侧鳍平均翼长为（0.15±0.03）μm,与其它三种罗非鱼精子鞭毛平均侧鳍翼长比较具显著性差异（P〈0.05）。
基金supported by the grants from the National Natural Science Foundation of China(No.30870810)the Program for New Century Excellent Talents in University
文摘The International Association of Hydrological Sciences （IAHS） recognized the lack of hydro- logical data as a world-wide problem in 2002 and adopted the Prediction of Ungauged Basins （PUB） as a decadal research agenda during the period of 2003 to 2012. One of the objectives is to further develop methodologies for prediction in ungauged basins and to reduce uncertainties in model prediction. Estimation of stream flows is required for flood control, water quality control, valley habitat assessment and water budget of a country. However, the majority of water catchments, streams and valleys are ungauged in most developing countries. The main objective of this paper is to introduce the IHACRES （Identification of Hy- drographs and Components from Rainfall, Evaporation and Stream） model into African hydrological plan- ning as a methodology for water resources assessment, which in turn can be used to resolve water conflicts between communities and countries and to study the climate change issues. This is because the IHACRES model is applied for the estimation of flows in ungauged catchments whose physical catchments descriptors （PCDs） can be determined by driving variables （i.e. rainfall and temperature）; and also in gauged streams but whose gauging stations are no longer operational but historical data are available for model calibration. The model provides a valuable insight into the hydrologic behaviour of the upper water sources for valleys as well as provides a useful methodology for water resources assessment in situations of scarce financial resources in developing countries. In addition, it requires relatively few parameters in its calibration and has been successful applied in previous regionalization studies. It will also make possible the equitable distri- bution of water resources in international basins and rivers＇ catchments. This paper does not apply the model anywhere, but recommends it as a methodology for water resources assessment in order to cure water conflicts on the African continent.
文摘Water quality of the river Nile and trace elements of the water, sediments and fish tissues were investigated in the current work. Eighteen different sampling points were selected along the whole course of the River Nile from its spring at Aswan to its estuaries at Rosetta and Damietta. Higher mean value of conductivity, alkalinity, chemical oxygen demand (COD), total organic carbon (TOC), ammonia (NH3), nitrate (NO3), total solid (TS), sulphate (SO4), chloride (Cl), orthophosphate were recorded in the water of Damietta and Rosetta branches comparing to other sites. Also trace metals in the water, sediments and tissues of Clarias gariepinus increased significantly (P Fe > Cu > Pb > Mn > Cr> Cd > Hg. In the gill tissues theses metals were accumulated in the following order Fe > Zn > Mn > Pb > Cr > Cu > Cd> Hg. The low accumulation of metals in muscle may be due to lack of binding affinity of these metals with the proteins of muscle. This is particularly important because muscles contribute the greatest mass of the flesh that is consumed as food.
文摘River Nile is one of the longest transboundery rivers and it is shared and used by Burundi,Democratic Republic of Congo,Egypt,Ethiopia,Eritrea,Kenya,Rwanda,Sudan,Tanzania and Uganda.As of today,the Nile is a crucial resource for the economic development of the Nile Basin countries and a vital source of livelihood for 160 million inhabitants as well as 300 million people living in the 10 riparian countries.The Nile Basin Initiative(NBI) is one of the international cooperative river basin management program and regional partnership where all the Nile Basin countries except Eritrea unite to pursue long-term sustainable development,improved land use practices and management.This review therefore focused on the challenges not faced on NBI in terms of integrated use of the river and conducted analysis of strengths,weaknesses,opportunities and threats(SWOT) based on secondary data.The result of the review revealed that for decades,the Nile Basin people have been facing many complex environmental,social,economic and political challenges that have made it difficult for the proper management and sustainability of Nile water.The initiative provides training to develop skills in government ministries,non-governmental organizations and local communities in each country.It is also working to raise awareness of critical environmental issues by strengthening networks of environmental education practitioners;developing curriculum in the education sector.The challenges of NBI include the involvement and funding of World Bank,lack of sufficient staff,procedural and policies conflicts,lack of coordination and linkage with other regional institutions and lack of recognition as river basin organization.Considering the complex nature of the project,it is recommended that the NBI should come up with a strong multi-disciplinary monitoring and evaluation team to follow up all implemented projects.The NBI should carry out participatory land use planning in communities along the river basin.Moreover,livelihood analysis should be carried out especially in communities along the Nile to come up with poverty eradication projects which are socially acceptable,applicable,economically viable and affordable.
文摘Objectives The main objective of the present article is to assess and evaluate the characteristics of the Nile water system , and identify the major sources of pollution and its environmental and health consequences. The article is also aimed to highlight the importance of water management via re-use and recycle of treated effluents for industrial purpose and for cultivation of desert land. Method An intensive effort was made by the authors to collect, assess and compile the available data about the River Nile. Physico-chemical analyses were conducted to check the validity of the collected data. For the determination of micro-pollutants, Gas Chromatography (GC) and High Performance Liquid Chromatography (HPLC) were used. Heavy metals were also determined to investigate the level of industrial pollution in the river system. Results The available data revealed that the river receives a large quantity of industrial, agriculture and domestic wastewater. It is worth mentioning that the river is still able to recover in virtually all the locations, with very little exception. This is due to the high dilution ratio. The collected data confirmed the presence of high concentrations of chromium and manganese in all sediment samples. The residues of organo-chlorine insecticides were detected in virtually all locations. However, the levels of such residues are usually below the limit set by the WHO for use as drinking water. The most polluted lakes are Lake Maryut and Lake Manzala. Groundwater pollution is closely related to adjacent (polluted) surface waters. High concentrations of nutrients, E.coli, sulfur, heavy metals, etc. have been observed in the shallow groundwater, largely surpassing WHO standards for drinking water use. Conclusion A regular and continuous monitoring scheme shall be developed for the River Nile system. The environmental law shall be enforced to prohibit the discharge of wastewater (agricultural, domestic or industrial) to River Nile system.
文摘Urban sprawl is threatening the limited highly fertile land in the Nile delta of Egypt. Landsat TM satellite images of 1984, 1992 and ETM+ of 2006 have been used to study the impact of urban sprawl on agricultural land of the Northern Nile delta, Egypt. Visual interpretation using on screen digitizing and change detection techniques were applied for monitoring the urban sprawl. Combining the land capability map and the urban thematic layer using GIS made it possible to point out the risk of urban expansion on the expense of the highly capable soil class. The results show that a total expansion of urban area amounted to 689.20 km2(6.3% of total area) during the study period 1984–2006. The urban expansion during the 1984–2006 was on the expense of the most fertile soils where, the high capable soils(Class I) lost 247.14 km2(2.26 % of total area) and the moderate capable soils lost 32.73 km2(0.3% of total area), while the low capable soils lost only 57.39 km2(0.53% of total area). The urban encroachment over the non capable soils was very limited during the study period 1984–1992, where 7.33 km2 only was lost. The pattern of urban sprawl has been changed during the 1992 to 2006 whereas much larger area(50.64 km2) of the non capable soils was converted to urban. It can be concluded that the urban sprawl is one of the dominant degradation process on the land of Nile Delta.
