Reactive nitrogen(Nr)emission from soils,e.g.,nitrous acid(HONO)and nitric oxide(NO),is a key process of the global nitrogen(N)cycle and has significant implications for atmospheric chemistry.To understand the underly...Reactive nitrogen(Nr)emission from soils,e.g.,nitrous acid(HONO)and nitric oxide(NO),is a key process of the global nitrogen(N)cycle and has significant implications for atmospheric chemistry.To understand the underlying mechanisms of soil Nr emissions,air-dried or oven-dried soils are commonly used in the laboratory.To date,few studies have compared the effects of different drying methods on soil Nr gas fluxes and N fractions.Here,the authors studied soil water content,pH,(in)organic N content,and Nr gas fluxes of air-dried,freeze-dried,oven-dried,and fresh soils from different land-use types.The results showed that the soil pH of air-dried and oven-dried samples was significantly lower compared with fresh soil from farmland and grassland,but higher compared with forest soil.The difference in soil pH between freeze-dried and fresh soil(mean±standard deviation:0.52±0.31)was the lowest.In general,all drying methods increased the soil NH4+-N,NO3−-N,and dissolved organic N contents compared with fresh soil(P<0.05).The maximum HONO and NO flux and total emissions during a full wetting–drying cycle of fresh soil were also increased by air-drying and oven-drying(P<0.001),but comparable with freeze-dried soil(P>0.2).In conclusion,all drying methods should be considered for use in studies on the land–atmosphere interface and biogeochemical N cycling,whereas the freeze-drying method might be better for studies involving the measurement of soil Nr gas fluxes.展开更多
Objective:The aim of our study was to observe the different effects including diameter of cryosurgery region and incidence of pneumothorax and pleural effusion when cryosurgery upon the pulmonary parenchyma with singl...Objective:The aim of our study was to observe the different effects including diameter of cryosurgery region and incidence of pneumothorax and pleural effusion when cryosurgery upon the pulmonary parenchyma with single or double freeze-thaw cycles in rabbits.Methods:Fifty rabbits were divided into two groups and they were all subjected to cryosurgery.The group one was single freeze-thaw cycle cryosurgery and the other group was double cycles.Pneumothorax and pleural effusion were observed after cryosurgery immediately with computer tomograph.The surviving animals were killed at 3 days after cryosurgery and histology observe were obtained.Results:There was no animal dead in the test.Histologically,a hemorrhagic infarct developed in the region of cryosurgery.The incidence of pneumothorax was 28% in group one and 12% in group two.The diameter of cryosurgery region was(4.3 ± 0.8) cm in rabbits who received double cycles cryosurgery and 3.1 ± 0.8 cm in single cycle.Conclusion:It is safety to cryosurgery upon pulmonary parenchyma with one or two cycles and the histological changes are similar.The diameter of cryosurgery region with two cycles was bigger than one.展开更多
The structure of concrete generally serves in multi-media environments; various environments act differently on concrete. The compound action of some severe environments will threaten the duration of concrete and decr...The structure of concrete generally serves in multi-media environments; various environments act differently on concrete. The compound action of some severe environments will threaten the duration of concrete and decrease the service life of a concrete structure if improperly handled. In this paper the microstructure of concrete is observed by using Scanned Electric Microscope (SEM) through contrasting experiments in media of acid, alkali and salt with that of freezing-thawing in the same medium environment. This study is to supply a certain basis for changing traditional thinking of mechanical design and to combine construction reliability design with durability of concrete design.展开更多
基金This work was sponsored by the National Natural Science Foundation of China[grant numbers 41807449,41761144062,and 41730646]the Shanghai Pujiang Program[grant number 18PJ1403500]the Fundamental Research Funds for the Central Universities.
文摘Reactive nitrogen(Nr)emission from soils,e.g.,nitrous acid(HONO)and nitric oxide(NO),is a key process of the global nitrogen(N)cycle and has significant implications for atmospheric chemistry.To understand the underlying mechanisms of soil Nr emissions,air-dried or oven-dried soils are commonly used in the laboratory.To date,few studies have compared the effects of different drying methods on soil Nr gas fluxes and N fractions.Here,the authors studied soil water content,pH,(in)organic N content,and Nr gas fluxes of air-dried,freeze-dried,oven-dried,and fresh soils from different land-use types.The results showed that the soil pH of air-dried and oven-dried samples was significantly lower compared with fresh soil from farmland and grassland,but higher compared with forest soil.The difference in soil pH between freeze-dried and fresh soil(mean±standard deviation:0.52±0.31)was the lowest.In general,all drying methods increased the soil NH4+-N,NO3−-N,and dissolved organic N contents compared with fresh soil(P<0.05).The maximum HONO and NO flux and total emissions during a full wetting–drying cycle of fresh soil were also increased by air-drying and oven-drying(P<0.001),but comparable with freeze-dried soil(P>0.2).In conclusion,all drying methods should be considered for use in studies on the land–atmosphere interface and biogeochemical N cycling,whereas the freeze-drying method might be better for studies involving the measurement of soil Nr gas fluxes.
文摘Objective:The aim of our study was to observe the different effects including diameter of cryosurgery region and incidence of pneumothorax and pleural effusion when cryosurgery upon the pulmonary parenchyma with single or double freeze-thaw cycles in rabbits.Methods:Fifty rabbits were divided into two groups and they were all subjected to cryosurgery.The group one was single freeze-thaw cycle cryosurgery and the other group was double cycles.Pneumothorax and pleural effusion were observed after cryosurgery immediately with computer tomograph.The surviving animals were killed at 3 days after cryosurgery and histology observe were obtained.Results:There was no animal dead in the test.Histologically,a hemorrhagic infarct developed in the region of cryosurgery.The incidence of pneumothorax was 28% in group one and 12% in group two.The diameter of cryosurgery region was(4.3 ± 0.8) cm in rabbits who received double cycles cryosurgery and 3.1 ± 0.8 cm in single cycle.Conclusion:It is safety to cryosurgery upon pulmonary parenchyma with one or two cycles and the histological changes are similar.The diameter of cryosurgery region with two cycles was bigger than one.
文摘The structure of concrete generally serves in multi-media environments; various environments act differently on concrete. The compound action of some severe environments will threaten the duration of concrete and decrease the service life of a concrete structure if improperly handled. In this paper the microstructure of concrete is observed by using Scanned Electric Microscope (SEM) through contrasting experiments in media of acid, alkali and salt with that of freezing-thawing in the same medium environment. This study is to supply a certain basis for changing traditional thinking of mechanical design and to combine construction reliability design with durability of concrete design.
