Search

Northern snakehead, Channa argus (C. argus), is an important economic and ecological fish species. The wild population of the species was sharply declined in the last decade. A high-quality reference genome could lay a solid foundation for the genetic and conservation studies for C. argus. In this work, we report a chromosomal genome assembly with PacBio and Hi-C technology using the albino northern snakehead, a color variety of C. argus. A 644.1-Mb genome with 24 chromosomes was obtained with a contig and scaffold N50 of 11.78 and 27.8 Mb, respectively. We inferred that C. argus diverged from A. testudineus around 85.6 million years ago. 514 expanded gene families and 214 positively selected genes were identified in the C. argus genome. The chromosome-level genome provides a valuable high-quality genomic resource for population, as well as genetic and evolutionary studies for C. argus and other species in Channidae.

Ocean tides in polar regions play an important role in the study of sea ice dynamics and floating ice shelves. The accuracy of existing ocean tide models in shallow waters and polar seas is much lower than that in open deep oceans. This study summarized the advances of state-of-the-art global tide models in the Antarctic Ocean, the construction of tide models around Circum-Antarctica, and five typical regions: Antarctic Peninsula, Ross Sea, Filchner–Ronne Ice Shelf (FRIS), Weddell Sea, and Amery Ice Shelf (AIS). The accuracy of FES 2014, TPXO9, EOT20, CATS 2008, and regional tide models in the Antarctic Ocean and typical areas was evaluated using tidal records and satellite altimetry data. EOT20 and ANTPEN04.01 models have higher accuracy in the Antarctic Peninsula, and the root sum square (RSS) values are 8.29 and 7.46 cm, respectively. TPXO9 has the highest accuracy in the Weddell Sea and FRIS and AIS and RSS values are 18.33 and 12.77 cm, respectively. TPXO9 and RIS_Optimal models have higher accuracy in the Ross Sea and Ross Ice Shelf (RIS), RSS values are 5.62 and 6.21 cm, respectively. The accuracy of FES 2014, TPXO9, CATS 2008, and the regional tide model in the Drake Passage, Kerguelen Islands, and Adelie–Mertz was evaluated using satellite altimetry data. The RSS values are less than 4 cm. By using the altimetry data at Sentinel-3A single-satellite crossovers in terms of the STD of the SLA, the comparison of the STDs show that FES2014 is the best.

This project aims to design a novel passive quasi-zero stiffness vibration isolator (QZS-VI) and analyze the static and dynamic mechanical properties of the QZS-VI. First, a novel combination of V-shaped lever, plate spring and cross-shaped structure (VL-PS-CS) vibration isolation platform is designed, and a nonlinear QZS-VI is built by parallel connecting VL-PS-CS and coil spring. Second, the static and dynamic modeling of QZS-VI are derived considering the geometrical nonlinearity of V-shaped lever and the large deflection of plate spring, and the average method is applied to obtain the displacement transmissibility. Third, the effects of different structural parameters (e.g., the lengths of long arm and short arm of V-shaped lever, the assembly angle between two arms, the thickness of plate spring) on the static mechanical and equivalent nonlinear friction properties of QZS-VI are thoroughly investigated. Finally, the vibration isolation performance of the designed QZS-VI is compared with another QZS-VI of buckled beam mechanism and traditional linear vibration isolator. The QZS-VI with VL-PS-CS fully explores the nonlinear advantages of plate spring and V-shaped lever and can achieve excellent high static and low dynamic stiffness and nonlinear friction properties. The superior static mechanical properties and nonlinear friction of QZS-VI can be tuned with different structural parameters. The designed QZS-VI exhibits much smaller resonant frequency, lower peak value and more stability property at the peak frequency than other isolators due to its special nonlinear friction and stiffness properties. The designed QZS-VI is practical, novel and suitable for low-frequency vibration isolation. The innovative structure provides novel insights into the design of passive vibration isolators and has great potential for application in engineering practice.

The situation of current research on power losses allocation in bilateral electricity markets is presented. Based on cooperative game theory, a novel nucleolus theory-based method for power losses allocation under the bilateral-transactions model is put forward and compared in detail with the Shapley-value-based allocation method. The impacts of different market players on network power losses are taken into account. With the new method, network power losses can be allocated to each transaction reasonably. The allocation results would not be affected by the sequence that each transaction is formed and be active. The method answers for the open, equal, and impartial principles of electricity market and can be easily understood and accepted by market players. Numerical tests validated the equity and validity of the method.

The technique of precise point positioning (PPP) is gradually becoming a popular method in GPS data-processing. In GPS observation equation, the unknown parameters can be separated into two parts: global parameters and local parameters. The global parameters include orbit, satellite clock and geodynamic parameters. The local parameters are site-occupation-spectific, such as position, tropospheric delay, etc. The formulas of local parameters are firstly derived under the network-solution and the PPP-solution conditions respectively. If the weight matrix of global parameters in PPP-solution is small enough, the cofactor matrices of local parameters are the same as that in network-solution. Then, 16 daily solutions are obtained in both PPP mode and network mode. Three sites are selected to compare the solutions. The experimental results demonstrated that the difference between two solutions in coordinates and tropospheric delays are only few millimeters. This level of difference can be neglected so that the ...

The multibeam sonars can provide hydrographic quality depth data as well as hold the potential to provide calibrated measurements of the seafloor acoustic backscattering strength. There has been much interest in utilizing backscatters and images from multibeam sonar for seabed type identification and most results are obtained. This paper has presented a focused review of several main methods and recent developments of seafloor classification utilizing multibeam sonar data or/and images. These are including the power spectral analysis methods, the texture analysis, traditional Bayesian classification theory and the most active neural network approaches.

Petrochemical studies indicate that the Yanghou metamorphic ultramafic rocks are composed of metamorphosed harzburgite and ultramafic cumulate. Trace element geochemistry and mineral chemistry of the metamorphic harzburgite indicate that they are relicts of depleted mantle. Systematic petrochemical, mineral chemical and geochronological studies led to such a conclusion that the Yanghou metamorphic ultramafic rocks may be the components of Late Sinian-Early Paleozoic ophiolites in South China.

This experiment was conducted to study the effect of dietary lipid level on the body index,lipid deposition and lipid metabolic enzyme activities of juvenile Onychostoma sima.We randomly assigned fish(n=900)with average initial body weight of(0.78±0.05)g into 6 groups consisting of 3 replicates that each replicate was 50 fish.Six isonitrogenous and isoenergetic diets(40% CP and 16.30 MJ/kg GE)were formulated containing 0(control group),2%,4%,6%,8%or 10% soybean oil respectively,Those actual lipid level was 2.83%,4.52%,6.68%,9.14%,11.35% and 14.07%,respectively.The experiment lasted for 60 days.The results showed that the condition factor(CF)of Onychostoma sima initially increased with increasing lipid levels,but then decreased,the CF was highest(2.64%)when the dietary lipid level was 9.14%,but there was no significant differences when lipid level were 6.68%-14.07%,(P0.05).The hepatosomatic index(HSI)increased with increasing dietary lipid levels(P0.05),while viscerosomatic index(VSI)had no significant differences(P0.05).The crude lipid content of muscle and liver were easily affected by dietary lipid levels,and the crude lipid content of muscle and liver increased with increasing dietary lipid levels.There was no significant effect of dietary lipid level on nitrogen gain(P0.05),energy gain was highest when the dietary lipid level was 14.07%,at the same time,the nitrogen and energy retention initially increased with increasing lipid levels,but then decreased,those were highest when the dietary lipid level was 11.35% and 9.14% respectively.Lipid gain of Onychostoma sima increased with increasing dietary lipid levels,but the lipid retention decreased(P0.05).The activities of intestinal lipase initially increased with increasing lipid levels,but then decreased,and the activities of lipoprotein lipase,hepatic lipase and total lipase first increased,then decreased as the level of dietary lipid increased,those were all highest(296.03 U/g,30.59 U/g,34.28 U/g and 64.87 U/g respectively)when the dietary lipid level was 9.14%.At the same time,fatty acid synthetetase(FAS)decreased with the increase of contents.Results of above show that suitable dietary lipid level could improve the utilization rate of feed nutrients and reduce body lipid deposition,but when dietary lipid level reaches or exceeds 11.35%,the lipid deposition in liver would increase,which is bad for health and growth of Onychostoma sima.

This experiment was conducted to study the effect of replacement of fish meal by soybean meal protein on the growth,body composition and hematology indices of juvenile Schizothorax prenanti.Healthy S.prenanti [with the initial weight(14.67±0.51) g]were randomly divided into six groups with three replicates of 30 fish.Six isonitrogenous and isoenergetic diets were formulated to contain different levels of soybean meal based upon the basal diet to replace fish meal protein 0(A1),20%(A2),40%(A3),60%(A4),80%(A5) and 100%(A6).The experiment lasted for 45 days.The results showed that the weight gain ratio(WGR),the specific growth ratio(SGR) and protein efficiency ratio(PER) were highest(118.08%,1.95%/d,207.22%,respectively),the feed conversion ratio(FCR) was the lowest(1.27) when the replace-ment ratio of fish meal protein by soybean meal was 60%(P0.05).The WGR,SGR,PER were signifi-cantly lower when the replacement ratio of fish meal protein of 100%,while the FCR was significantly higher than that of the other groups(P0.05).Based on quadratic regression analysis,the best replacement ratio of fish meal protein by soybean meal was 34.25% 45.46%.There were no significant difference in whole body moisture,crude ash and the condition factor(CF) with the replacement ratio of fish meal pro-tein by soybean meal increased,the crude protein in whole body was highest(15.53%) when the replace-ment ratio of fish meal protein by soybean meal was 60%.The crude protein and lipid in whole body had no significant difference when the replacement ratio of fish meal protein by soybean meal was less than 80%(P0.05).while the hepatopancreas somatic index(HIS) increased as soybean meal protein ratio in-creased,but there were no significant differences when the replacement ratio of fish meal protein by soy-bean meal was 0 80%(P0.05).Superoxide dismutase(SOD) activities have a certain fluctuation as soy-bean meal protein ratio increased,at the same time,SOD activities were highest when the replacement ratio of fish meal protein by soybean meal was 40%.Lysozyme(LSZ) activities were gradually increased when the replacement ratio of fish meal protein by soybean meal was 20% 60%(P0.05).The aspartate ami-notransferase(AST)and alanine aminotransferase(ALT)activities increased as soybean meal protein ratio increased,but there were no significant differences when the replacement ratio of fish meal protein by soybean meal was less than 80%(P0.05).The AST and ALT activities were significantly higher than the control group and other experimental groups(P0.05).Results of above show that a certain percentage soybean meal protein ratio in diet could promote the growth,and improve feed protein metabolism and immunity of S.prenanti.In conclusion,the maximum replacement ratio of fish meal protein by soybean meal was 80% in the diets of S.prenanti,and the most suitable replacement ratio of fish meal protein by soybean meal was 34.25% 45.46%.