Objective To evaluate the change of elasticity of rabbit liver following portal inflow vessels occlusion using acoustic radiation force impulse (ARFI). Methods Twelve Japanese white big ear rabbits were used to establish total hepatic vascular exclusion animal models by occluding the portal inflow vessels. The elasticity of rabbits' right liver was detected during the stages of baseline(T0), 5 min(T1),20min(T2) ,30min (T3)after occluding the portal inflow vessels using ARFI respectively. The elasticity of rabbit liver, levels of serum's aspartate aminotransferase (AST), alanine aminotransferase (ALT) and historical results of hepatic tissue during different stage were compared. Results Shear wave velocity(Vs)of rabbits' right livers in T2 was significantly higher than that in T0 ( P ＜0.05) and Vs of rabbits' right livers in T3 was significantly higher than that in T2 ( P ＜0.05). No significant differences of serum's AST,ALT levels between T2 and T0 were found,while the Vs of rabbit live in T2 was slightly higher than that in T0 (P＞0.05), serum's AST, ALT levels in T3 were significantly higher than that in T2 ( P ＜0.05).Historical changes of liver ischemia and injury were observed in T2 and T3 with light microscopy. Conclusions The liver ischemia and injury severity can be accurately and objectively evaluated using ARFI.

Objective:To monitor and analyze the activity concentrations of 7Be and 210Pb in atmospheric aerosol in Beijing from 2017 to 2020. Methods:Totally 1 074 atmospheric aerosol samples were collected by high flow air sampler (SnowWhite) including 275 in spring, 266 in summer, 262 in autumn and 271 in winter and subjected to analysis by low background high-purity germanium gamma-ray spectrometery (ORTEC) to determine the activity concentrations of 7Be and 210Pb. Results:The activity concentrations of 7Be in atmospheric aerosol were from 0.56 to 14.84 mBq/m 3, with an avearage of 6.84 mBq/m 3, and from 0.01 to 9.37 mBq/m 3 for 210Pb, with an avearage 3.19 mBq/m 3. The differences in activity concentrations of 7Be and 210Pb in atmospheric aerosol among differernt seasons were statistically significant ( F=32.66, 93.93, P<0.05). Activity concentration of 7Be was highest in spring, followed by autumn, and lowest in summer and winter. Activity concentration of 210Pb ranged from winter, autumn, spring to summer in descending order. Conclusions:The activity concentrations of 7Be and 210Pb in atmospheric aerosol in Beijing from 2017 to 2020 fluctated within the range of normal level.