A reverse transcription PCR (RT-PCR) method was used to detect the Hepatitis A virus in clam tissues The RNA template for PCR was prepared by a modified described previously (Yang and Xu, 1993).Its recovery wes determined by DNA hybridization.The sensitivity of RT-PCR and the quantitation of HAV were determined by quantitative competitive PCR.
This paper proposes two simple models, look-up table (LUT) model and empirical model, to directly retrieve significant wave height (Hs) using synthetic aperture radar (SAR) azimuth cutoff (λc). Both models aim at C-band VV, HH, VH, and HV single-polarization SAR images. The LUT model relates Hs to λc, while the empirical model relates Hs to both λc and SAR range-to-velocity (β). The LUT model coefficients are derived by simulation under different sea states and observation conditions, which depend on incidence angle (θ), wave direction (dw), and β but are independent of polarization. The empirical model coefficients are obtained by fitting the collocated data, which only depend on polarization. To fit empirical model coefficients and validate the two models, C-band RADARSAT-2 fine quad-polarization (VV+HH+VH+HV) single-look complex (SLC) SAR images and collocated buoy data are collected. Retrieved Hs, using Yang model and the two models proposed in this paper from four kinds of polarization SAR data, are compared with buoy Hs. Results show that both LUT and empirical models have the capacity of retrieving Hs from C-band RADARSAT-2 co-polarization SAR data, while Yang model is not suitable for these kinds of SAR data. Moreover, the empirical model is also valid for cross-polarization SAR data showing clear ocean wave stripes.
The presented method for numerical typhoon wave prediction is composed of a scheme for real time pressure forecasts, a marine wind numerical model and a typhoon wave numerical model.In the Northwest Pacific Ocean and China seas where water depth is over 20 m, a hybrid wave model[Wen Shengchang, Zhang Dacuo, Chen Bohai and Guo Peifang.1989, Acta Oceannlogica Sinica, 8 (1), 1-14; Zhang Dacuo, Wu Zengmao, Jiang Decai, Rang Wei, Chen Bohai, Tai R'eitao, R'en Shengchang, Xu Qichun and Guo Peifang.1992, Acta Oceanologica Sinica, 11 (2), 157-178] is employed with 10°×10° grids, while in the South China Sea and East China Sea where typhoon frequently appears, the WAM model (WAMDI Group.1988, Journal of Physical Oceanography, 18, 1755-1810) of shallow water version is embedded with (1/4)°× (1/4)° grids.The boundary condition at the open boundary of the WAM model is provided by the hybrid model.After 3 a of testing forecasts (Yang Chuncheng, Dai Mingrui and Zhang Dacuo.1992, International Symposium on Tropical Cyclone Dusaaters, October 12-16, Beijing, 404-409)and improvement, this system was put into operational use on the forecasting computer network of National Marine Environment Forecast Center of China in June, 1993.The wave predictions of 22 typhoon events show that the system is stable and prompt, and the forecast results are satisfactory.This system provides reliable numerical products for the disaster-prevention forecasts.The product is broadcasted in CCTV News at every noon.
On the basis of the EOF analysis of global geopotential height anomaly (GHA) field at 10 hPa level, the arctic oscillation (AO) and the means antarctic oscillation (AAO) can be detected more obviously at the upper level of atmosphere than the AO or the AAO in surface layer. Unlike the hemisphere pattern of the AO and the AAO in the surface lager given by previous authors, the AO or the AAO in the stratosphere has its global features. The zonal oscillations-the Southern Oscillation (SO) and the north oscillation (NO) in atmospheric surface layer become less clear in the upper air. The first mode (AO mode, abbreviated to AOM hereafter) and the second mode (AAO mode, abbreviated to AAOM hereafter) respectively have 41.47% and 27.04% of the total variance contribution. The cumulative variance contribution of the first two modes reaches 68.51%. These two modes are the main components for the interdecadal or decadal oscillation in the stratosphere. In addition, there still exist two kinds of oscillation patterns with less probability,namely, the symmetric pattern at mid-high latitudes in the Southern Hemisphere and the asymmetric pattern. Spectral analysis shows that the AOM and the AAOM all have a spectral peak for 22 a period, being consistent with the periodic variations of the solar magnetic field, and a peak for 11 a period, being consistent with the period of the numbers of sunspots. Step filter analysis shows that the influencing factor for the upper atmospheric oscillation is the solar activity. The fluctuation of the solar magnetic field is the more influencing factor than the variation of the sunspot number.