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.