The genetic variation and differentiation of the razor clam Sinonovacula constricta distributed along the coast of China were studied through amplified fragment length polymorphism(AFLP) analysis.Six primer combinatio...The genetic variation and differentiation of the razor clam Sinonovacula constricta distributed along the coast of China were studied through amplified fragment length polymorphism(AFLP) analysis.Six primer combinations generated 193 fragments.The He values varied from 0.322 to 0.463 and the percentage of polymorphic loci ranged from 74.1% to 98.4%,which indicates a high level of genetic diversity.Cluster analysis by Nei's pairwise distance grouped all specimens by geographical origins.AMOVA consistently showed that genetic variation among populations was 8.71%,and most of the variation came from the genetic variation within populations(91.29%).Genetic differentiation among the six populations was moderate;pairwise FST ranged from 0.0282 to 0.1480,which indicated that S.constricta populations along the coast of China are genetically connected.Among all the six populations,the Beihai population is the mostly differentiated from the others,suggesting that Hainan Island and Leizhou Peninsula act as barriers to gene flow.All populations abide isolation by distance model as indicated by Mantel test,except for ZS(Zhoushan) and YQ(Yueqing) populations.Information obtained in this study will provide guidelines for conservation and fishery management of this species in the future.展开更多
In this research,a comparative analysis was conducted on the performance and efficiency of the dual-anchor soft robot(DASR)and the extension-contraction soft robot(ECSR).These robots were constructed by imitating the ...In this research,a comparative analysis was conducted on the performance and efficiency of the dual-anchor soft robot(DASR)and the extension-contraction soft robot(ECSR).These robots were constructed by imitating the locomotion of razor clams.The penetration force for extension actuators and the anchorage force for expansion actuators in dry sand with distinct relative densities were tested by differentiating input air pressure and length-to-diameter ratios(λ).On the basis of the findings,a DASR and an ECSR were developed.DASR comprised two expansion actuators as the head and the tail segments at two ends,and one extension actuator as the middle segment.ECSR was composed of an extension actuator.A method based on the force equilibrium was introduced to ascertain and adjust the geometric parameters(length of each segment)of DASR.The burrowing-out performance and efficiency of DASR and ECSR in sands with distinct relative densities were explored.The results revealed that DASR exhibited high efficiency in dense sand in terms of lower time of burrowing-out,slip-to-advancement ratio,and cost of transport.ECSR might perform better in looser sand in terms of higher average burrowing-out velocity,higher advancement in each cycle,and lower energy consumption.However,it had larger slips than DASR.DASR could realize steady advancement and net displacement in each cycle and effectively decrease slips.These findings demonstrate the benefits and usability of the dual-anchor motion and offer new insights into the application of the dual-anchor mechanism in the burrowing of robots.展开更多
The U.S. economy faces deeper problems, though immediate danger subsided As if watching a replay of the fight over the U.S. national debt ceiling in 2011, the crisis billed as the "fiscal cliff" ended up wi...The U.S. economy faces deeper problems, though immediate danger subsided As if watching a replay of the fight over the U.S. national debt ceiling in 2011, the crisis billed as the "fiscal cliff" ended up with a last-minute compromise between thetwo major political parties of the United States.展开更多
A 30-year-old woman presented to the emergency department complaining of abdominal discomfort.An abdominal radiograph was done,revealing ten rectangular razor blades measuring 52 cm.The patient was taken to the opera...A 30-year-old woman presented to the emergency department complaining of abdominal discomfort.An abdominal radiograph was done,revealing ten rectangular razor blades measuring 52 cm.The patient was taken to the operating room and a flexible esophago-gastroduodenoscopy was performed.Attempts at retrieval,using both a gastric overtube and an inverted hood,were unsuccessful due to the shape and size of the blades.She was transferred to a regular medical floor and managed conservatively with serial abdominal radiographs.Over the next week,she passed the razor blades transanally without further event—all were still wrapped in paper and chewing gum—and was cleared to be discharged home.展开更多
基金supported by the grants from National High Technology Research and Development Program (2007AA09Z433)the Major State Basic Research Development Program of China (973 Program, 2010CB-126406)Chinese Ministry of Education (707041)
文摘The genetic variation and differentiation of the razor clam Sinonovacula constricta distributed along the coast of China were studied through amplified fragment length polymorphism(AFLP) analysis.Six primer combinations generated 193 fragments.The He values varied from 0.322 to 0.463 and the percentage of polymorphic loci ranged from 74.1% to 98.4%,which indicates a high level of genetic diversity.Cluster analysis by Nei's pairwise distance grouped all specimens by geographical origins.AMOVA consistently showed that genetic variation among populations was 8.71%,and most of the variation came from the genetic variation within populations(91.29%).Genetic differentiation among the six populations was moderate;pairwise FST ranged from 0.0282 to 0.1480,which indicated that S.constricta populations along the coast of China are genetically connected.Among all the six populations,the Beihai population is the mostly differentiated from the others,suggesting that Hainan Island and Leizhou Peninsula act as barriers to gene flow.All populations abide isolation by distance model as indicated by Mantel test,except for ZS(Zhoushan) and YQ(Yueqing) populations.Information obtained in this study will provide guidelines for conservation and fishery management of this species in the future.
基金financially supported by the Natural Science Foundation of Jiangsu Province,China(No.BK 20221502)the National Natural Science Foundation of China(No.42477147)。
文摘In this research,a comparative analysis was conducted on the performance and efficiency of the dual-anchor soft robot(DASR)and the extension-contraction soft robot(ECSR).These robots were constructed by imitating the locomotion of razor clams.The penetration force for extension actuators and the anchorage force for expansion actuators in dry sand with distinct relative densities were tested by differentiating input air pressure and length-to-diameter ratios(λ).On the basis of the findings,a DASR and an ECSR were developed.DASR comprised two expansion actuators as the head and the tail segments at two ends,and one extension actuator as the middle segment.ECSR was composed of an extension actuator.A method based on the force equilibrium was introduced to ascertain and adjust the geometric parameters(length of each segment)of DASR.The burrowing-out performance and efficiency of DASR and ECSR in sands with distinct relative densities were explored.The results revealed that DASR exhibited high efficiency in dense sand in terms of lower time of burrowing-out,slip-to-advancement ratio,and cost of transport.ECSR might perform better in looser sand in terms of higher average burrowing-out velocity,higher advancement in each cycle,and lower energy consumption.However,it had larger slips than DASR.DASR could realize steady advancement and net displacement in each cycle and effectively decrease slips.These findings demonstrate the benefits and usability of the dual-anchor motion and offer new insights into the application of the dual-anchor mechanism in the burrowing of robots.
文摘The U.S. economy faces deeper problems, though immediate danger subsided As if watching a replay of the fight over the U.S. national debt ceiling in 2011, the crisis billed as the "fiscal cliff" ended up with a last-minute compromise between thetwo major political parties of the United States.
文摘A 30-year-old woman presented to the emergency department complaining of abdominal discomfort.An abdominal radiograph was done,revealing ten rectangular razor blades measuring 52 cm.The patient was taken to the operating room and a flexible esophago-gastroduodenoscopy was performed.Attempts at retrieval,using both a gastric overtube and an inverted hood,were unsuccessful due to the shape and size of the blades.She was transferred to a regular medical floor and managed conservatively with serial abdominal radiographs.Over the next week,she passed the razor blades transanally without further event—all were still wrapped in paper and chewing gum—and was cleared to be discharged home.
