With global warming and declining Arctic sea ice area in autumn observed by satellites since 1979, anomalous cold snaps in recent winters have affected large parts of North America, Europe, and East Asia. In January 2...With global warming and declining Arctic sea ice area in autumn observed by satellites since 1979, anomalous cold snaps in recent winters have affected large parts of North America, Europe, and East Asia. In January 2015, North America suffered extremely cold and heavy snowfall events. As revealed in this paper, the NCEP reanalysis data show that the temperature decreased significantly in January 2015 in North America, including the air temperature in the troposphere and the surface air temperature. Moreover, snow cover increased obviously in January 2015 in North America, while there was a significant negative anomaly of geopotential height. The wind formed the anomalous pattern, which favored cold currents blowing to the North American continent from the polar region, and bringing plenty of water vapor. Our results suggest that the anomalous north wind and decreasing westerly jet stream, which allowed cold and moist air to easily penetrate the North American continent from the Arctic, was one of the main reasons for the extremely cold and heavysnow winter of 2015 in North America.展开更多
Ammopiptanthus mongolicus, the only freezing tolerant evergreen broad-leaved shrub, local species of the Alashan desert, northwest sand area of China, can survive -30℃ or even lower temperature in winter. In the pres...Ammopiptanthus mongolicus, the only freezing tolerant evergreen broad-leaved shrub, local species of the Alashan desert, northwest sand area of China, can survive -30℃ or even lower temperature in winter. In the present study, the secondary products phenolics in A. mongolicus cotyledons were determined to study the effects of phenolics on cold tolerance. Cytochemical localization of phenolics in cotyledon cells was observed by electron microscopy and the content of phenolic compounds was assayed by spectrophotometric measurement. The results showed that the freezing tolerance ofA. mongolicus seedlings increased after acclimation at 2℃ for 14 days, which accompanied the increase of the content of phenolic compounds in cotyledons. Cytochemical observation showed that phenolic deposits were mainly localized in vacuoles and in close proximity to tonoplast, and also in the cytoplasm. The amount and the size of phenolics droplets increased obviously in cytoplasm and vacuoles after cold acclimation, predominantly aggregated along membranes of vacuoles and tonoplast. No phenolic deposits were found in cell walls. As hydrogen- or elec- tron-donating agents, phenolics may protect plant cells against reactive oxygen species formed during chilling or freezing stress and improve the freezing tolerance of cold-acclimated A. mongolicus seedlings.展开更多
This article take cold regions of nlral residential building envelope as the research object, suitability technical theory as the theoretical basis, we evaluation of rural residential energy envelope because China＇s ...This article take cold regions of nlral residential building envelope as the research object, suitability technical theory as the theoretical basis, we evaluation of rural residential energy envelope because China＇s rural areas is chmacterized by large regional differences and to find a solution for the envelope. It could be considered as the useful reference for retrofit design of similar projects.展开更多
Osteochondral allografting has been proved to be a useful method to treat diseased or damaged areas of joint surfaces. Operational long-term stocks of grafts which supply a buffer between procurement and utilization w...Osteochondral allografting has been proved to be a useful method to treat diseased or damaged areas of joint surfaces. Operational long-term stocks of grafts which supply a buffer between procurement and utilization would contribute to the commercialization or industrialization of this technology. Vitrification has been thought to be a promising method for successful preservation of articular cartilage （AC）, but high concentration cryoprotectants （CPAs） are used which may cause high cellular toxicity. An effective way to reduce CPA toxioity is to increase CPA concen- tration gradually while the temperature is lowered. Understanding the mechanism of （31~A permeation at subzero temperatures is important for designing the cryopreservation protocol. In this research, the permeation of dimethyl sulfoxide （MezSO） in ovine AC at subzero temperatures was studied experimentally. Pretreated AC discs were ex- posed in Me2SO solutions for different time （0, 5, 15, 30, 50, 80, and 120 min） at three temperature levels （-10, -20, and -30℃）. The Me2SO concentration within the tissue was determined by ultraviolet （UV） spectrophotometry. The diffusion coefficients were estimated to be 0.85×10-6, 0.48×10-8, and 0.27×10-6 cm2/s at -10, -20, and -,30℃, respectively, and the corresponding activation energy was 29.23 kJ/mol. Numerical simulation was performed to com- pare two Me2SO addition protocols, and the results demonstrated that the total loading duration could be effectively reduced with the knowledge of permeation kinetics.展开更多
基金supported by the project of comprehensive evaluation of polar areas on global and regional climate changes(CHINARE2015-04-04)the National Natural Science Foundation of China[grant number 41406027]
文摘With global warming and declining Arctic sea ice area in autumn observed by satellites since 1979, anomalous cold snaps in recent winters have affected large parts of North America, Europe, and East Asia. In January 2015, North America suffered extremely cold and heavy snowfall events. As revealed in this paper, the NCEP reanalysis data show that the temperature decreased significantly in January 2015 in North America, including the air temperature in the troposphere and the surface air temperature. Moreover, snow cover increased obviously in January 2015 in North America, while there was a significant negative anomaly of geopotential height. The wind formed the anomalous pattern, which favored cold currents blowing to the North American continent from the polar region, and bringing plenty of water vapor. Our results suggest that the anomalous north wind and decreasing westerly jet stream, which allowed cold and moist air to easily penetrate the North American continent from the Arctic, was one of the main reasons for the extremely cold and heavysnow winter of 2015 in North America.
基金the National Natural Science Foundation of China （Grant No. 30671476 , 30271067）.
文摘Ammopiptanthus mongolicus, the only freezing tolerant evergreen broad-leaved shrub, local species of the Alashan desert, northwest sand area of China, can survive -30℃ or even lower temperature in winter. In the present study, the secondary products phenolics in A. mongolicus cotyledons were determined to study the effects of phenolics on cold tolerance. Cytochemical localization of phenolics in cotyledon cells was observed by electron microscopy and the content of phenolic compounds was assayed by spectrophotometric measurement. The results showed that the freezing tolerance ofA. mongolicus seedlings increased after acclimation at 2℃ for 14 days, which accompanied the increase of the content of phenolic compounds in cotyledons. Cytochemical observation showed that phenolic deposits were mainly localized in vacuoles and in close proximity to tonoplast, and also in the cytoplasm. The amount and the size of phenolics droplets increased obviously in cytoplasm and vacuoles after cold acclimation, predominantly aggregated along membranes of vacuoles and tonoplast. No phenolic deposits were found in cell walls. As hydrogen- or elec- tron-donating agents, phenolics may protect plant cells against reactive oxygen species formed during chilling or freezing stress and improve the freezing tolerance of cold-acclimated A. mongolicus seedlings.
文摘This article take cold regions of nlral residential building envelope as the research object, suitability technical theory as the theoretical basis, we evaluation of rural residential energy envelope because China＇s rural areas is chmacterized by large regional differences and to find a solution for the envelope. It could be considered as the useful reference for retrofit design of similar projects.
基金supported by the National Natural Science Foundation of China (No. 50606032)the Graduate Innovation Research Program of Zhejiang Province (No. YK2008020), China
文摘Osteochondral allografting has been proved to be a useful method to treat diseased or damaged areas of joint surfaces. Operational long-term stocks of grafts which supply a buffer between procurement and utilization would contribute to the commercialization or industrialization of this technology. Vitrification has been thought to be a promising method for successful preservation of articular cartilage （AC）, but high concentration cryoprotectants （CPAs） are used which may cause high cellular toxicity. An effective way to reduce CPA toxioity is to increase CPA concen- tration gradually while the temperature is lowered. Understanding the mechanism of （31~A permeation at subzero temperatures is important for designing the cryopreservation protocol. In this research, the permeation of dimethyl sulfoxide （MezSO） in ovine AC at subzero temperatures was studied experimentally. Pretreated AC discs were ex- posed in Me2SO solutions for different time （0, 5, 15, 30, 50, 80, and 120 min） at three temperature levels （-10, -20, and -30℃）. The Me2SO concentration within the tissue was determined by ultraviolet （UV） spectrophotometry. The diffusion coefficients were estimated to be 0.85×10-6, 0.48×10-8, and 0.27×10-6 cm2/s at -10, -20, and -,30℃, respectively, and the corresponding activation energy was 29.23 kJ/mol. Numerical simulation was performed to com- pare two Me2SO addition protocols, and the results demonstrated that the total loading duration could be effectively reduced with the knowledge of permeation kinetics.
