Background: The Bar-headed Goose(Anser indicus) is a species that relies heavily on the plateau wetlands of Asia and whose population was thought to be declining. Over the past decade, south-central Tibet, one of the ...Background: The Bar-headed Goose(Anser indicus) is a species that relies heavily on the plateau wetlands of Asia and whose population was thought to be declining. Over the past decade, south-central Tibet, one of the most important wintering grounds, supported large numbers of Bar-headed Geese, but the population had not been regularly monitored in this area.Methods: We surveyed wintering Bar-headed Geese along the Yarlung Zangbo, Lhasa and Nyang Qu rivers, the three major river valleys and their tributaries in south-central Tibet in January 2014 and recorded their location, flock size and habitat utilization. Based on these data and the latest wintering counts elsewhere, we revised the population estimate for this species.Results: We recorded more than 67,000 Bar-headed Geese in south-central Tibet during January 2014. By geographic area, the geese were most abundant in the Lhasa River valley(38.5%) and the Nyang Qu River valley(31.0%), and by administrative division in Lhunzhub(27.2%) and Shigatse(26.7%). Bar-headed Geese were most often observed feeding in winter wheat fields and ploughed fields, resting on pastureland and marshes. The approximate number of 67,000 geese recorded in Tibet is more than four times the estimate of 1993 for the same region and exceeds the most recent world population estimate of 52,000–60,000. Based on our work in Tibet and the latest wintering counts available from other areas, we revised the estimated population size of this species to 97,000–118,000.Conclusions: Our result reveals a remarkable increase in the number of Bar-headed Geese wintering in south-central Tibet. This population increase most likely stems from a proliferation of cropland and especially winter wheat fields in south-central Tibet. This habitat improvement may also cause short-stopping of the Bar-headed Goose and thus reduce mortality of the geese that would otherwise undertake a somewhat daunting trans-Himalayan migration.展开更多
Microbial molecular ecology approaches were used to the effects of Bar-transgenic rice on Intestinal Micro-flora of the Mice (Mus musculus). Kunming mice (Mus musculus) of 100 SPF-grade (20 g ± 2 g), half of whic...Microbial molecular ecology approaches were used to the effects of Bar-transgenic rice on Intestinal Micro-flora of the Mice (Mus musculus). Kunming mice (Mus musculus) of 100 SPF-grade (20 g ± 2 g), half of which were male and the other half female, were randomly divided into five groups with four replications per group and five mice per replication to assess the safety of Bar-transgenic rice. Five diets meetinging or exceeding the minimum nutrient requirement were fed for 180 days. After 90 days, parental generation (P) was bred to produce the first filial generation (F1). Each generation was fed for 180 days. On the 180th day, five mice from each group were randomly sampled, and their intestinal contents were collected for DNA isolation. The V3 region of the 16S rDNA was amplified by polymerase chain reaction (PCR) and analyzed via denaturing gradient gel electrophoresis (DGGE). The resulting PCR-DGGE band number (bacterial species) was counted, and the banding patterns were analyzed by calculating the Sorenson’s pairwise similarity coefficients (Cs), an index used to measure bacterial species found among all samples. The sequence analysis of bands was performed to identify the intestinal predominant microflora of the mice. The intergroup Cs values of the samples across all groups did not differ (P > 0.05) from each other. The effect of Bar-transgenic rice on the intestinal microflora of the mice was considered insignificant.展开更多
There are two kinds of piezoelectric pumps:check valve pumps and valve-less pumps.Whether to use a check valve or not depends upon the application occasion.To achieve large backpressure for higher flow rates,the pump ...There are two kinds of piezoelectric pumps:check valve pumps and valve-less pumps.Whether to use a check valve or not depends upon the application occasion.To achieve large backpressure for higher flow rates,the pump with check valve is desirable.However,adding check valves implies more complex structure and higher probability of valve blocking,etc.In order to solve the problem,effective driving and transport mechanics with compact construction and reliable service are being sought.In this paper,using the second-order longitudinal vibration mode of a bar-shaped piezoelectric vibrator for driving fluid,a piezoelectric pump is successfully made.The proposed piezoelectric pump consists of coaxial cylindrical shells and a bar-shaped piezoelectric vibrator,which has a disk part and a cone part.The lead zirconium titanate ceramic rings fixed in the vibrator are polarized along the thickness direction.When the second-order longitudinal vibration of the vibrator along its axis is excited,the disk part of the vibrator changes periodically the volume of the chamber and the cone part acts as a pin valve,driving the fluid from the inlet port to the outlet port.Finite elements analysis on the proposed pump model is carried out to verify its operation principle and design by the commercial FEM software ANSYS.Components of the piezoelectric pump were manufactured,assembled,and tested for flow rate and backpressure to validate the concepts of the proposed pump and confirm the simulation results of modal and harmonic analyses.The test results show that the performance of the proposed piezoelectric pump is about 910 mL/min in flow rate with a highest pressure level of 1.5 kPa under 400 V peak-to-peak voltage and 51.7 kHz operating frequency.It is confirmed that this bar-shaped piezoelectric transducer can be effectively applied in fluid transferring mechanism of pump through this research.展开更多
Based on the character of the internal force distribution of the statically indeterminate truss, the elements stresses were changed by adjusting the length of bars to increase load capacity of structure. The efficienc...Based on the character of the internal force distribution of the statically indeterminate truss, the elements stresses were changed by adjusting the length of bars to increase load capacity of structure. The efficiency of the method is illustrated by several examples.展开更多
基金funded by the Wildlife Rescue Project from the Department of Wildlife Protection and Nature Reserve Management, State Forestry Administration (SFA) of Chinathe Project of Surveillance of H7N9 in Wild Birds (No. 201404404) from the Department of Science and Technology, SFAco-funded by the International Crane Foundation
文摘Background: The Bar-headed Goose(Anser indicus) is a species that relies heavily on the plateau wetlands of Asia and whose population was thought to be declining. Over the past decade, south-central Tibet, one of the most important wintering grounds, supported large numbers of Bar-headed Geese, but the population had not been regularly monitored in this area.Methods: We surveyed wintering Bar-headed Geese along the Yarlung Zangbo, Lhasa and Nyang Qu rivers, the three major river valleys and their tributaries in south-central Tibet in January 2014 and recorded their location, flock size and habitat utilization. Based on these data and the latest wintering counts elsewhere, we revised the population estimate for this species.Results: We recorded more than 67,000 Bar-headed Geese in south-central Tibet during January 2014. By geographic area, the geese were most abundant in the Lhasa River valley(38.5%) and the Nyang Qu River valley(31.0%), and by administrative division in Lhunzhub(27.2%) and Shigatse(26.7%). Bar-headed Geese were most often observed feeding in winter wheat fields and ploughed fields, resting on pastureland and marshes. The approximate number of 67,000 geese recorded in Tibet is more than four times the estimate of 1993 for the same region and exceeds the most recent world population estimate of 52,000–60,000. Based on our work in Tibet and the latest wintering counts available from other areas, we revised the estimated population size of this species to 97,000–118,000.Conclusions: Our result reveals a remarkable increase in the number of Bar-headed Geese wintering in south-central Tibet. This population increase most likely stems from a proliferation of cropland and especially winter wheat fields in south-central Tibet. This habitat improvement may also cause short-stopping of the Bar-headed Goose and thus reduce mortality of the geese that would otherwise undertake a somewhat daunting trans-Himalayan migration.
文摘Microbial molecular ecology approaches were used to the effects of Bar-transgenic rice on Intestinal Micro-flora of the Mice (Mus musculus). Kunming mice (Mus musculus) of 100 SPF-grade (20 g ± 2 g), half of which were male and the other half female, were randomly divided into five groups with four replications per group and five mice per replication to assess the safety of Bar-transgenic rice. Five diets meetinging or exceeding the minimum nutrient requirement were fed for 180 days. After 90 days, parental generation (P) was bred to produce the first filial generation (F1). Each generation was fed for 180 days. On the 180th day, five mice from each group were randomly sampled, and their intestinal contents were collected for DNA isolation. The V3 region of the 16S rDNA was amplified by polymerase chain reaction (PCR) and analyzed via denaturing gradient gel electrophoresis (DGGE). The resulting PCR-DGGE band number (bacterial species) was counted, and the banding patterns were analyzed by calculating the Sorenson’s pairwise similarity coefficients (Cs), an index used to measure bacterial species found among all samples. The sequence analysis of bands was performed to identify the intestinal predominant microflora of the mice. The intergroup Cs values of the samples across all groups did not differ (P > 0.05) from each other. The effect of Bar-transgenic rice on the intestinal microflora of the mice was considered insignificant.
基金supported by National Basic Research Program (973 Program, Grant No. 2011CB707602)National Natural Science Foundation of China (Grant No. 10874090, Grant No. 91023020)National Natural Science Foundation of China Guangdong Joint Fund (Grant No. U0934004)
文摘There are two kinds of piezoelectric pumps:check valve pumps and valve-less pumps.Whether to use a check valve or not depends upon the application occasion.To achieve large backpressure for higher flow rates,the pump with check valve is desirable.However,adding check valves implies more complex structure and higher probability of valve blocking,etc.In order to solve the problem,effective driving and transport mechanics with compact construction and reliable service are being sought.In this paper,using the second-order longitudinal vibration mode of a bar-shaped piezoelectric vibrator for driving fluid,a piezoelectric pump is successfully made.The proposed piezoelectric pump consists of coaxial cylindrical shells and a bar-shaped piezoelectric vibrator,which has a disk part and a cone part.The lead zirconium titanate ceramic rings fixed in the vibrator are polarized along the thickness direction.When the second-order longitudinal vibration of the vibrator along its axis is excited,the disk part of the vibrator changes periodically the volume of the chamber and the cone part acts as a pin valve,driving the fluid from the inlet port to the outlet port.Finite elements analysis on the proposed pump model is carried out to verify its operation principle and design by the commercial FEM software ANSYS.Components of the piezoelectric pump were manufactured,assembled,and tested for flow rate and backpressure to validate the concepts of the proposed pump and confirm the simulation results of modal and harmonic analyses.The test results show that the performance of the proposed piezoelectric pump is about 910 mL/min in flow rate with a highest pressure level of 1.5 kPa under 400 V peak-to-peak voltage and 51.7 kHz operating frequency.It is confirmed that this bar-shaped piezoelectric transducer can be effectively applied in fluid transferring mechanism of pump through this research.
文摘Based on the character of the internal force distribution of the statically indeterminate truss, the elements stresses were changed by adjusting the length of bars to increase load capacity of structure. The efficiency of the method is illustrated by several examples.
