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Urban green space, as an important component of an urban ecosystem, plays an important role in improving the urban living environment, maintaining ecological balance and reducing carbon dioxide concentration. Few studies are focused on carbon dioxide emissions in urban green spaces of cold regions. To thoroughly understand the temporal and spatial variation laws of carbon dioxide concentration and its influencing factors in urban green spaces in cold regions, a LI-COR LI-840 non-dispersive infrared gas analyser was used to explore the variations in the carbon dioxide concentrations of different plant community green spaces at the syringa Park in Qunli New District of Harbin and their influencing factors. Diurnal variation, seasonal variation, annual dynamics, and temporal and spatial distributions of carbon dioxide concentration in the growing season of four types of park green spaces, namely, larix, birch, syringa, and grassland communities, were observed through experiments. Air temperature, surface temperature, air humidity, and atmospheric pressure in the four types of green spaces were measured to further analyse the correlation among the diurnal variation of carbon dioxide concentration, seasonal variation of carbon dioxide concentration, and the corresponding factors of different vegetation types in parks. Moreover, the annual regression equation of carbon dioxide concentration was established. Results show that the carbon dioxide concentration in different community green spaces exhibits an obvious diurnal variation and a tendency of decreasing first and then increasing over time. The seasonal dynamics of carbon dioxide concentration in different types of park green spaces are different. The carbon dioxide concentration of the larix green space is the lowest (dynamics), whereas that of the grassland space is the highest (357.17±30.18 μmol/mol). The larix seasonal dynamics demonstrates the change with the seasons, from highest to lowest as autumn>spring>summer. Temperature is the main controlling factor that affects the variation in carbon dioxide concentration in the growing season. The carbon dioxide concentrations of larix, birch, syringa and grassland show a highly significant positive correlation with surface and air temperatures. A significantly positive correlation is also observed between atmospheric pressure and variation in carbon dioxide concentration in larix and birch. This study provides data reference and support for spatial ecological planning and layout and the selection of plants in urban park green spaces. [ABSTRACT FROM AUTHOR]

Aim: To study the efficacy of antiviral treatment with PNA for the duck model of HBV (DHBV)-infected ducks. PNA is a 2-amine-9-(2,3-dideoxy-2,3-dihydro-β-D-arabinofuranosyl)-6-methoxy-9 H-purine. Methods: The Sichuan Mallard ducklings in the hepatitis B virus model were treated with PNA, a new antiviral agent. DHBV DNA from the blood serum and liver tissues were measured at 0, 5, and 10 d during the treatment and at 3 d withdrawal by real-time PCR. The duck hepatitis B surface antigen (DHBsAg) in the liver cells was observed by Immunohistochemistry (IHC). Pathological changes in the liver tissues were also observed. Control group I was administered with distilled water and control group II was administered with 3-thiacytidine. Treatment group I was administered with PNA at a dose of 40 mg/kg and treatment group II was administered perorally ( po) with PNA at a dose of 80 mg/kg. Treatment group III was administered with PNA at a dose of 20 mg/kg and treatment group IV was intravenously administered with PNA at a dose of 40 mg/kg. Each group contained 15 ducklings. Results: PNA can significantly lower the DHBV replication levels in serum and liver. Compared with control group II, there were no significant differences in inhibiting efficacy in treatment groups I and III ( P>0.05) and there were significant differences in inhibiting efficacy in treatment groups II and IV ( P<0.05). Interestingly, significant differences were observed at 3 d withdrawal. The DHBV replication levels in each group slightly increased at 3 d withdrawal, but rebounded slightly in the PNA treatment groups than in control group II ( P<0.05). The DHBV replication levels in the treatment groups were lower than in control group I. The DHBV replication levels in sera had a positive relationship with that in the liver, but the DHBV replication levels in the liver was lower than that in sera. Pathological changes in the treatment groups were obviously improved and the changes were associated with liver viral DNA levels. Conclusion: The results demonstrate that PNA is a strong inhibitor of DHBV replication in the DHBV-infected duck model. [ABSTRACT FROM AUTHOR]