Search

Conventional AVO inversion employs Zoeppritz equations and various approximations to them to obtain the reflection coefficients of plane-waves, which are confined to a certain (small) angle range (mostly below $$40^{\circ }$$). However, near the critical angles (wide-angle), reflections at the post-critical angles provide much more potential for velocity and density inversion because of the large amplitudes and phases-shifted waveforms, while the Zoeppritz equations are not applicable anymore. Hence, there is a strong demand for the research into wide-angle AVO. With reflection coefficients at wide-angle corresponding to the features of rational function, we try to approximate the seismic data with vector fitting which is used to obtain the rational zero-pole and residual properties of wide-angle AVO. We apply this technique to classify AVO type and recognize the lithology. Our experiment shows that extending our research into wide-angle AVO is very promising in gathering richer data for a more accurate seismic analysis.

Okra is widely used as vegetable, food ingredient, and traditional medicine in China for various applications. The main healthy properties are accepted to originate from the high polysaccharide content of okra. In this study, a homogenous pectic polysaccharide WOP-2 was extracted, isolated, and purified from okra by DEAE-cellulose and Sepharose CL-6B column, and its molecular weight was estimated to be 580 kDa. Monosaccharide composition was analyzed to be Rha (21.4%), GalA (34.9%), Gal (29.6%), GlcA (4.5%), Glc (5.9%), and Ara (3.7%) by HPLC with PMP derivatization. Combined with NMR analysis, WOP-2 was elucidated to be a rhamnogalacturonan I backbone with type-II arabinogalactan side-chains substituted partly at O-4 of Rhap. WOP-2 exhibits significant anti-hyperglycemic activity on STZ-induced diabetic mice by inhibiting the lipid peroxidation chain reaction probably. Overall, these results provide new insight into structure–activity relationships of polysaccharide from okra and provide impetus towards the development of polysaccharide-based therapeutics on diabetes.