The population of the intertidal gastropod Littorina saxcailis from Laxey estuary in the Isle of Man is exposed to mine-related contamination of Zn （and is tolerant to Zn and Pb） compared to those of Castletown, Der...The population of the intertidal gastropod Littorina saxcailis from Laxey estuary in the Isle of Man is exposed to mine-related contamination of Zn （and is tolerant to Zn and Pb） compared to those of Castletown, Derbyhaven, Peel and Ramsey. Tolerances to salinity and desiccation stress were assayed to test how metal tolerance could affect tolerance to general stress. The winkles were experimentally exposed to salinities of 0, 17 and 60 practical salinity units （psu） with 34 psu as control. Desiccation stress was determined by aerial exposure of the winkles at 24℃. No control mortalities were recorded and mortalities in 17 psu were less than 50% for all populations over a 24-day exposure period. LT50 values （mean±SD, n=5） at 0 psu ranged from 6.6 ± 0.6 to 7.5 ± 1.3 d for winkles from Ramsey and Laxey respectively. The values for 60 psu ranged from 7.0±0.7 to 8.4±0.9 d. No significant differences in LT50 values were obtained for the salinity exposurcs（ANOVA,P〉0.05） but there was a significant difference in tolerance to desiccation （P〈0.01）. The winkles from Laxey showed very high susceptibility to desiccation stress probably indicating a physiological trade-off to metal tolerance.展开更多
Using surface and NCEP reanalysis data along with radar and satellite images, diagnosis has been carried out to probe the reasons for the very heavy rainfall that occurred in Islāmābad-Rāwal...Using surface and NCEP reanalysis data along with radar and satellite images, diagnosis has been carried out to probe the reasons for the very heavy rainfall that occurred in Islāmābad-Rāwalpindi on 23 July 2001. It has been revealed that the sudden evolution of this meso-scale severe weather system was the direct result of strong surface convection in moist and unstable lower layers of the atmosphere. The subsequent rapid development was the combined effect of the presence of the mid latitude westerly’s trough in the north and moisture feeding through monsoon flow along the Himalayas and also the direct south-westerly current from the Arabian Sea. After the westward shifting of the Sub-Tropical High (STH) from the north of India, the strong divergence zone on its eastern edge contributed positively to the development of upward motion. Initially the convective systems moved towards the south and then southeastward following the steering current in the middle troposphere. Based on these analyses, the physical model of the sudden record heavy rainfall has been proposed and a comparison between the heavy rainfall in this case and one in China has been conducted.展开更多
Polyploidy is pervasive in angiosperm evolution and plays important roles in adaptation and speciation.However,polyploid groups are understudied due to complex sequence homology,challenging genome assembly,and taxonom...Polyploidy is pervasive in angiosperm evolution and plays important roles in adaptation and speciation.However,polyploid groups are understudied due to complex sequence homology,challenging genome assembly,and taxonomic complexity.Here,we study adaptive divergence in taxonomically complex eyebrights(Euphrasia),where recent divergence,phenotypic plasticity,and hybridization blur species boundaries.We focus on three closely related tetraploid species with contrasting ecological preferences that are sympatric on Fair Isle,a small isolated island in the British Isles.Using a common garden experiment,we show a genetic component to the morphological differences present between these species.Using wholegenome sequencing and a novel k-mer approach we call“Tetmer”,we demonstrate that the species are of allopolyploid origin,with a sub-genome divergence of approximately 5%.Using2 million SNPs,we show sub-genome homology across species,with a very low sequence divergence characteristic of recent speciation.This genetic variation is broadly structured by species,with clear divergence of Fair Isle heathland Euphrasia micrantha,while grassland Euphrasia arctica and coastal Euphrasia foulaensis are more closely related.Overall,we show that tetraploid Euphrasia is a system of allopolyploids of postglacial species divergence,where adaptation to novel environments may be conferred by old variants rearranged into new genetic lineages.展开更多
The Explosive Reactive Armors(ERA)are really efficient at reducing Shaped Charge Jet(SCJ)performance.The main destabilizing mechanism is the transverse movement of the front and rear moving plates(MP)on the SCJ.Theref...The Explosive Reactive Armors(ERA)are really efficient at reducing Shaped Charge Jet(SCJ)performance.The main destabilizing mechanism is the transverse movement of the front and rear moving plates(MP)on the SCJ.Therefore,a good understanding of the interaction SCJ/MP is essential for improving both weapon and armor systems.In a previous article,we have shown that interaction regimes are mainly influenced by the local collision geometry.Thus,in the collision point frame,the angle of collision be-tween the continuous SCJ and the MP is a key parameter.This flow angle is acute for the Backward Moving plate(BMP)moving against the SCJ and obtuse for the Forward Moving Plate(FMP)moving alongside it.In the former,the jet is simply deflected,which is the regime 1 of deflection.In the latter,the interaction turns on an alternative creation of fragment and ligament,which is the regime 2.Fragments are parts of the jet that are only slightly deflected while ligaments are the curved material bridges that connect two consecutive fragments.When stretching,the jet is systematically subject to instabilities that disturb its surface,creating necks along it.Their growth finally leads to the jet fragmentation.In this article,we focus on this jet distur-bance and its consequences on the SCJ/MP interaction.An experimental set-up was built to implement the interaction between a SCJ and a moving plate for different collision points,at different stand-off distances.The plate can interact with a smooth SCJ or a disturbed SCJ at a close and a far stand-off distance,respectively.One of the main results is the visualization of a regime change in SCJ/BMP interaction.A regime 1(deflection)interaction changes into a ligament regime interaction(similar to a FMP regime 2)when the collision point stand-off is increased.It is proposed that this change can be attributed as the increase of the amplitude of the jet surface disturbances.This phenomenon is well captured by the gSPH simula-tions.Finally,using both experimental and numerical approaches,we propose a new detailed analysis of the different phenomena occurring during the interaction between a disturbed-surface jet and a moving plate.Interaction regime changes are linked to jet local geometry changes.The interactions of a BMP with a smooth SCJ or with a disturbed surface SCJ are geometrically not the same and,thus,generate different local flows and interaction mechanisms.However,some other simulations have been carried out with constant velocity jet whose surface has been previously disturbed.These simulations underline the influence of both disturbance wavelength l and amplitude A on the interaction regimes.Surface disturbances of the SCJ,linked to its stretching,have a major influence on its interaction with a moving plate.展开更多
An analysis of the interaction mechanisms between a Shaped Charge Jet(SCJ) and a single Moving Plate(MP) is proposed in this article using both experimental and numerical approaches. First, an experimental set-up is p...An analysis of the interaction mechanisms between a Shaped Charge Jet(SCJ) and a single Moving Plate(MP) is proposed in this article using both experimental and numerical approaches. First, an experimental set-up is presented. Four collision tests have been performed: two tests in Backward Moving Plate(BMP) configuration, where the plate moves in opposition to jet, and two tests in Forward Moving Plate(FMP) configuration, where the plate moves alongside the jet. Based on the virtual origin approximation,a methodology(the Virtual Origin Method, VOM) is developed to extract quantities from the X-ray images, which serve as comparative data. γSPH simulations are carried out to complete the analysis, as they well capture the disturbance dynamics observed in the experiments. Based on these complementary experimental and numerical results, a new physical description is proposed through a detailed analysis of the interaction. It is shown that the SCJ/MP interaction is driven at first order by the contact geometry. Thus, BMP and FMP configurations do not generate the same disturbances because their local flow geometries are different. In the collision point frame of reference, the BMP flows in the same direction as the jet, causing its overall deflection. On the contrary, the FMP flow opposes that of the jet leading to an alternative creation of fragments and ligaments. An in-depth study, using the VOM shows that deflection angles, fragment-ligament creation frequencies, and deflection velocities evolve as the interaction progresses through slower jet elements.展开更多
The first author proposed the concept of the cemented material dam （CMD） in 2009. This concept was aimed at building an environmentally friendly dam in a safer and more economical way for both the dam and the area d...The first author proposed the concept of the cemented material dam （CMD） in 2009. This concept was aimed at building an environmentally friendly dam in a safer and more economical way for both the dam and the area downstream. The concept covers the cemented sand, gravel, and rock dam （CSGRD）, the rockfill concrete （RFC） dam （or the cemented rockfill dam, CRD）, and the cemented soil dam （CSD）. This paper summarizes the concept and principles of the CMD based on studies and practices in projects around the world. It also introduces new developments in the CSGRD, CRD, and CSD.展开更多
Over the past few decades,one of the most significant advances in dam construction has been the inven-tion of the rock-filled concrete(RFC)dam,which is constructed by pouring high-performance self-compacting concrete(...Over the past few decades,one of the most significant advances in dam construction has been the inven-tion of the rock-filled concrete(RFC)dam,which is constructed by pouring high-performance self-compacting concrete(HSCC)to fill the voids in preplaced large rocks.The innovative use of large rocks in dam construction provides engineers with a material that requires less cement consumption and hydration heat while enhancing construction efficiency and environmental friendliness.However,two fundamental scientific issues related to RFC need to be addressed:namely,the pouring compactness and the effect of large rocks on the mechanical and physical properties of RFC.This article provides a timely review of fundamental research and innovations in the design,construction,and quality control of RFCdams.Prospects for next-generation concrete dams are discussed from the perspectives of envi-ronmental friendliness,intrinsic safety,and labor savings.展开更多
To provide a scientific and technological base for fishery administration, holding a moratorium on fishing, and combating habitat degradation, a shrimp stock survey was carried out in May, August, and November 1998 an...To provide a scientific and technological base for fishery administration, holding a moratorium on fishing, and combating habitat degradation, a shrimp stock survey was carried out in May, August, and November 1998 and in February 1999. The study was conducted in the area between 26°00＇ N and 33°00＇ N and to the west of 127°00＇ E in the East China Sea using a multi-sac trawl-net, with 115 stations being sampled. Up to 2001, we had found 121 species, which belong to 63 genera under 22 families, and 41 species are of high economic value and in great abundance. Nine shrimp species were of great economic importance, whose stock accounted for 76.8% of the demersal total. They were Parapenaeus fissuroides, Metapenaeopsis philippi, Palaemon gravieri, Metapenaeopsis barbata, Solenocera koelbeli, Solenocera crassicornis, Trachypenaeus curvirostris, Solenocera melantho and Parapenaeopsis hardwickii （listed in stock order）. The nine species belong to the eurythermal and eurysaline community and high thermal and high saline community, had different migration patterns and stocks, and their distribution patterns could be generally classified into three types： （1） dominating in the north or the south; （2） dominating to the north of and in the coast to the south of 30000＇ N; and （3） dominating to the east of 60 m isobath, which were related to six water masses in the ECS near two lines, i.e., the 60 m isobath and 30°00＇N latitudinal lines. Densely habited shrimps were found in all four seasons due to temperature and salinity frontiers and upwelling. The general stock density index was relatively higher in spring, summer, and autumn, when it surpassed 10 kg/h, while in winter, it was only 6.8 kg/h which might be caused by overfishing. According to the spawning areas of the nine species and their distribution patterns, to attain sustainable development of the shrimp fishery in the ECS, it is imperative to protect fishing areas and to hold a moratorium on catching to the west of 60 m isobath from April through October, and between 60 m and 100 m isobaths and to the south of 30°N from June through August and to limit fishing in winter.展开更多
基金TheCom m onwealthU niversitiesCom m issionintheU nitedK ingdom
文摘The population of the intertidal gastropod Littorina saxcailis from Laxey estuary in the Isle of Man is exposed to mine-related contamination of Zn （and is tolerant to Zn and Pb） compared to those of Castletown, Derbyhaven, Peel and Ramsey. Tolerances to salinity and desiccation stress were assayed to test how metal tolerance could affect tolerance to general stress. The winkles were experimentally exposed to salinities of 0, 17 and 60 practical salinity units （psu） with 34 psu as control. Desiccation stress was determined by aerial exposure of the winkles at 24℃. No control mortalities were recorded and mortalities in 17 psu were less than 50% for all populations over a 24-day exposure period. LT50 values （mean±SD, n=5） at 0 psu ranged from 6.6 ± 0.6 to 7.5 ± 1.3 d for winkles from Ramsey and Laxey respectively. The values for 60 psu ranged from 7.0±0.7 to 8.4±0.9 d. No significant differences in LT50 values were obtained for the salinity exposurcs（ANOVA,P〉0.05） but there was a significant difference in tolerance to desiccation （P〈0.01）. The winkles from Laxey showed very high susceptibility to desiccation stress probably indicating a physiological trade-off to metal tolerance.
文摘Using surface and NCEP reanalysis data along with radar and satellite images, diagnosis has been carried out to probe the reasons for the very heavy rainfall that occurred in Islāmābad-Rāwalpindi on 23 July 2001. It has been revealed that the sudden evolution of this meso-scale severe weather system was the direct result of strong surface convection in moist and unstable lower layers of the atmosphere. The subsequent rapid development was the combined effect of the presence of the mid latitude westerly’s trough in the north and moisture feeding through monsoon flow along the Himalayas and also the direct south-westerly current from the Arabian Sea. After the westward shifting of the Sub-Tropical High (STH) from the north of India, the strong divergence zone on its eastern edge contributed positively to the development of upward motion. Initially the convective systems moved towards the south and then southeastward following the steering current in the middle troposphere. Based on these analyses, the physical model of the sudden record heavy rainfall has been proposed and a comparison between the heavy rainfall in this case and one in China has been conducted.
基金funded by NERC grants(NE/R010609/1,NE/L011336/1,NE/N006739/1)awarded to A.D.T.
文摘Polyploidy is pervasive in angiosperm evolution and plays important roles in adaptation and speciation.However,polyploid groups are understudied due to complex sequence homology,challenging genome assembly,and taxonomic complexity.Here,we study adaptive divergence in taxonomically complex eyebrights(Euphrasia),where recent divergence,phenotypic plasticity,and hybridization blur species boundaries.We focus on three closely related tetraploid species with contrasting ecological preferences that are sympatric on Fair Isle,a small isolated island in the British Isles.Using a common garden experiment,we show a genetic component to the morphological differences present between these species.Using wholegenome sequencing and a novel k-mer approach we call“Tetmer”,we demonstrate that the species are of allopolyploid origin,with a sub-genome divergence of approximately 5%.Using2 million SNPs,we show sub-genome homology across species,with a very low sequence divergence characteristic of recent speciation.This genetic variation is broadly structured by species,with clear divergence of Fair Isle heathland Euphrasia micrantha,while grassland Euphrasia arctica and coastal Euphrasia foulaensis are more closely related.Overall,we show that tetraploid Euphrasia is a system of allopolyploids of postglacial species divergence,where adaptation to novel environments may be conferred by old variants rearranged into new genetic lineages.
基金supported by the Ministère des Arméesthe Agence de l'Innovation de Défense (AID)
文摘The Explosive Reactive Armors(ERA)are really efficient at reducing Shaped Charge Jet(SCJ)performance.The main destabilizing mechanism is the transverse movement of the front and rear moving plates(MP)on the SCJ.Therefore,a good understanding of the interaction SCJ/MP is essential for improving both weapon and armor systems.In a previous article,we have shown that interaction regimes are mainly influenced by the local collision geometry.Thus,in the collision point frame,the angle of collision be-tween the continuous SCJ and the MP is a key parameter.This flow angle is acute for the Backward Moving plate(BMP)moving against the SCJ and obtuse for the Forward Moving Plate(FMP)moving alongside it.In the former,the jet is simply deflected,which is the regime 1 of deflection.In the latter,the interaction turns on an alternative creation of fragment and ligament,which is the regime 2.Fragments are parts of the jet that are only slightly deflected while ligaments are the curved material bridges that connect two consecutive fragments.When stretching,the jet is systematically subject to instabilities that disturb its surface,creating necks along it.Their growth finally leads to the jet fragmentation.In this article,we focus on this jet distur-bance and its consequences on the SCJ/MP interaction.An experimental set-up was built to implement the interaction between a SCJ and a moving plate for different collision points,at different stand-off distances.The plate can interact with a smooth SCJ or a disturbed SCJ at a close and a far stand-off distance,respectively.One of the main results is the visualization of a regime change in SCJ/BMP interaction.A regime 1(deflection)interaction changes into a ligament regime interaction(similar to a FMP regime 2)when the collision point stand-off is increased.It is proposed that this change can be attributed as the increase of the amplitude of the jet surface disturbances.This phenomenon is well captured by the gSPH simula-tions.Finally,using both experimental and numerical approaches,we propose a new detailed analysis of the different phenomena occurring during the interaction between a disturbed-surface jet and a moving plate.Interaction regime changes are linked to jet local geometry changes.The interactions of a BMP with a smooth SCJ or with a disturbed surface SCJ are geometrically not the same and,thus,generate different local flows and interaction mechanisms.However,some other simulations have been carried out with constant velocity jet whose surface has been previously disturbed.These simulations underline the influence of both disturbance wavelength l and amplitude A on the interaction regimes.Surface disturbances of the SCJ,linked to its stretching,have a major influence on its interaction with a moving plate.
基金supported by the Ministère des Armées,and the Agence de l'Innovation de Défense(AID).
文摘An analysis of the interaction mechanisms between a Shaped Charge Jet(SCJ) and a single Moving Plate(MP) is proposed in this article using both experimental and numerical approaches. First, an experimental set-up is presented. Four collision tests have been performed: two tests in Backward Moving Plate(BMP) configuration, where the plate moves in opposition to jet, and two tests in Forward Moving Plate(FMP) configuration, where the plate moves alongside the jet. Based on the virtual origin approximation,a methodology(the Virtual Origin Method, VOM) is developed to extract quantities from the X-ray images, which serve as comparative data. γSPH simulations are carried out to complete the analysis, as they well capture the disturbance dynamics observed in the experiments. Based on these complementary experimental and numerical results, a new physical description is proposed through a detailed analysis of the interaction. It is shown that the SCJ/MP interaction is driven at first order by the contact geometry. Thus, BMP and FMP configurations do not generate the same disturbances because their local flow geometries are different. In the collision point frame of reference, the BMP flows in the same direction as the jet, causing its overall deflection. On the contrary, the FMP flow opposes that of the jet leading to an alternative creation of fragments and ligaments. An in-depth study, using the VOM shows that deflection angles, fragment-ligament creation frequencies, and deflection velocities evolve as the interaction progresses through slower jet elements.
文摘The first author proposed the concept of the cemented material dam （CMD） in 2009. This concept was aimed at building an environmentally friendly dam in a safer and more economical way for both the dam and the area downstream. The concept covers the cemented sand, gravel, and rock dam （CSGRD）, the rockfill concrete （RFC） dam （or the cemented rockfill dam, CRD）, and the cemented soil dam （CSD）. This paper summarizes the concept and principles of the CMD based on studies and practices in projects around the world. It also introduces new developments in the CSGRD, CRD, and CSD.
基金the support from the Key Program Grant from National Natural Science Foundation of China (52039005)Grant from State Key Laboratory of Hydroscience and Engineering (2022-KY-01).
文摘Over the past few decades,one of the most significant advances in dam construction has been the inven-tion of the rock-filled concrete(RFC)dam,which is constructed by pouring high-performance self-compacting concrete(HSCC)to fill the voids in preplaced large rocks.The innovative use of large rocks in dam construction provides engineers with a material that requires less cement consumption and hydration heat while enhancing construction efficiency and environmental friendliness.However,two fundamental scientific issues related to RFC need to be addressed:namely,the pouring compactness and the effect of large rocks on the mechanical and physical properties of RFC.This article provides a timely review of fundamental research and innovations in the design,construction,and quality control of RFCdams.Prospects for next-generation concrete dams are discussed from the perspectives of envi-ronmental friendliness,intrinsic safety,and labor savings.
基金the Special Program of State Oceanic Administration of P. R. China.
文摘To provide a scientific and technological base for fishery administration, holding a moratorium on fishing, and combating habitat degradation, a shrimp stock survey was carried out in May, August, and November 1998 and in February 1999. The study was conducted in the area between 26°00＇ N and 33°00＇ N and to the west of 127°00＇ E in the East China Sea using a multi-sac trawl-net, with 115 stations being sampled. Up to 2001, we had found 121 species, which belong to 63 genera under 22 families, and 41 species are of high economic value and in great abundance. Nine shrimp species were of great economic importance, whose stock accounted for 76.8% of the demersal total. They were Parapenaeus fissuroides, Metapenaeopsis philippi, Palaemon gravieri, Metapenaeopsis barbata, Solenocera koelbeli, Solenocera crassicornis, Trachypenaeus curvirostris, Solenocera melantho and Parapenaeopsis hardwickii （listed in stock order）. The nine species belong to the eurythermal and eurysaline community and high thermal and high saline community, had different migration patterns and stocks, and their distribution patterns could be generally classified into three types： （1） dominating in the north or the south; （2） dominating to the north of and in the coast to the south of 30000＇ N; and （3） dominating to the east of 60 m isobath, which were related to six water masses in the ECS near two lines, i.e., the 60 m isobath and 30°00＇N latitudinal lines. Densely habited shrimps were found in all four seasons due to temperature and salinity frontiers and upwelling. The general stock density index was relatively higher in spring, summer, and autumn, when it surpassed 10 kg/h, while in winter, it was only 6.8 kg/h which might be caused by overfishing. According to the spawning areas of the nine species and their distribution patterns, to attain sustainable development of the shrimp fishery in the ECS, it is imperative to protect fishing areas and to hold a moratorium on catching to the west of 60 m isobath from April through October, and between 60 m and 100 m isobaths and to the south of 30°N from June through August and to limit fishing in winter.
