Vitamin D_(3)(VD_(3)) plays a vital role in various physiological processes in addition to its role in regulating the homeostasis of calcium and phosphorus.The present study was conducted to investigate the effects of...Vitamin D_(3)(VD_(3)) plays a vital role in various physiological processes in addition to its role in regulating the homeostasis of calcium and phosphorus.The present study was conducted to investigate the effects of dietary VD_(3) on growth performance,immune status and the metabolism of calcium and phosphorus in Litopenaeus vannamei under the optimal salinity(25)and high salinity(35)conditions.Shrimp(2.1 g±0.1 g)were fed with experimental diets containing 0,1500,6000 and 12000IUkg^(−1)VD_(3) for 30 days under two salinity conditions respectively.The results showed that the growth performance and intestinal health were reduced,while oxidative stress was induced in the shrimp cultured at salinity 35 compared to those in the shrimp cultured at salinity 25.Interestingly,dietary supplementation of 1500 IU kg^(−1)VD_(3) at salinity 35 promoted the growth performance,improved the intestinal health,and enhanced the antioxidant capacity and non-specific immunity in shrimp.In addition,the content of inorganic phosphorus in shrimp serum was affected by dietary VD_(3) independent of salinity.In contrast,the expressions of calcium transport-related genes,including calmodulin and Ca2+-ATPase,were regulated by salinity,instead of dietary VD_(3).In conclusion,an appropriate supplementation of dietary VD_(3) under high-salt condition can promote the growth,alleviate intestinal inflammation,enhance antioxidant capacity and immunity,and contribute to phosphorus metabolism in L.vannamei.展开更多
As the total pressure ratio of centrifugal compressors increases, the diffuser inlet flow becomes highly subsonic or even supersonic, which causes additional shock loss. The shock loss leads the stage performance to d...As the total pressure ratio of centrifugal compressors increases, the diffuser inlet flow becomes highly subsonic or even supersonic, which causes additional shock loss. The shock loss leads the stage performance to drop greatly. Pre-compression is an efficient method for reducing shock loss and improving the stage performance. To study the effect of wedge diffusers with pre-compression blades on centrifugal compressor performance, wedge diffusers with various pre-compression angles, divergence angles and numbers of blades were designed and investigated via a numerical method. As a result, it is found that the compressor stage achieves high peak efficiency when the pre-compression angle ranges from 2.5° to 5.5° and when the divergence angle ranges from 7° to 9°. As the number of blades increases, the total pressure ratio and adiabatic efficiency of the compressor stage increase slightly, whereas the surge margin of the stage decreases.展开更多
基金supported by the National Key R&D Program of China(No.2018YFD0900400)the National Natural Science Foundation of China(No.31972802)the Natural Science Foundation of Shandong Province(No.ZR2019MC041).
文摘Vitamin D_(3)(VD_(3)) plays a vital role in various physiological processes in addition to its role in regulating the homeostasis of calcium and phosphorus.The present study was conducted to investigate the effects of dietary VD_(3) on growth performance,immune status and the metabolism of calcium and phosphorus in Litopenaeus vannamei under the optimal salinity(25)and high salinity(35)conditions.Shrimp(2.1 g±0.1 g)were fed with experimental diets containing 0,1500,6000 and 12000IUkg^(−1)VD_(3) for 30 days under two salinity conditions respectively.The results showed that the growth performance and intestinal health were reduced,while oxidative stress was induced in the shrimp cultured at salinity 35 compared to those in the shrimp cultured at salinity 25.Interestingly,dietary supplementation of 1500 IU kg^(−1)VD_(3) at salinity 35 promoted the growth performance,improved the intestinal health,and enhanced the antioxidant capacity and non-specific immunity in shrimp.In addition,the content of inorganic phosphorus in shrimp serum was affected by dietary VD_(3) independent of salinity.In contrast,the expressions of calcium transport-related genes,including calmodulin and Ca2+-ATPase,were regulated by salinity,instead of dietary VD_(3).In conclusion,an appropriate supplementation of dietary VD_(3) under high-salt condition can promote the growth,alleviate intestinal inflammation,enhance antioxidant capacity and immunity,and contribute to phosphorus metabolism in L.vannamei.
文摘As the total pressure ratio of centrifugal compressors increases, the diffuser inlet flow becomes highly subsonic or even supersonic, which causes additional shock loss. The shock loss leads the stage performance to drop greatly. Pre-compression is an efficient method for reducing shock loss and improving the stage performance. To study the effect of wedge diffusers with pre-compression blades on centrifugal compressor performance, wedge diffusers with various pre-compression angles, divergence angles and numbers of blades were designed and investigated via a numerical method. As a result, it is found that the compressor stage achieves high peak efficiency when the pre-compression angle ranges from 2.5° to 5.5° and when the divergence angle ranges from 7° to 9°. As the number of blades increases, the total pressure ratio and adiabatic efficiency of the compressor stage increase slightly, whereas the surge margin of the stage decreases.
