Hong Kong Baptist University

About: Hong Kong Baptist University is a education organization based out in Hong Kong, China. It is known for research contribution in the topics: Population & China. The organization has 7811 authors who have published 18919 publications receiving 555274 citations. The organization is also known as: Hong Kong Baptist College & HKBU.

Extensible Lattice Sequences for Quasi-Monte Carlo Quadrature

Abstract: Integration lattices are one of the main types of low discrepancy sets used in quasi-Monte Carlo methods. However, they have the disadvantage of being of fixed size. This article describes the construction of an infinite sequence of points, the first bm of which forms a lattice for any nonnegative integer m. Thus, if the quadrature error using an initial lattice is too large, the lattice can be extended without discarding the original points. Generating vectors for extensible lattices are found by minimizing a loss function based on some measure of discrepancy or nonuniformity of the lattice. The spectral test used for finding pseudorandom number generators is one important example of such a discrepancy. The performance of the extensible lattices proposed here is compared to that of other methods for some practical quadrature problems.

ZnBr2-Ph4PI as highly efficient catalyst for cyclic carbonates synthesis from terminal epoxides and carbon dioxide

Abstract: The catalyst systems composed of ZnBr 2 and different phosphonium salts were examined for solvent-free synthesis of cyclic carbonates from CO 2 and terminal epoxides under mild conditions Among the catalysts investigated, ZnBr 2 –Ph 4 PI was found to be the best while those of ZnBr 2 –phosphine oxide (Bu 3 PO or Ph 3 PO) show no catalytic effect It is apparent that the halide ions of phosphonium salts have an essential role to play in the reaction The catalytic activity of ZnBr 2 –Ph 4 PI increases with a rise of Ph 4 PI to ZnBr 2 molar ratio up to 6, above which there is little change in catalytic activity We observed that with a rise in ZnBr 2 to Ph 4 PI molar ratio, there is increase in epoxide conversion but decline in TOF PO (estimated based on the site number of Zn 2+ ) The effect of water on the reaction was investigated for the first time We found that the presence of even a trace amount of water would result in a marked decline in reactivity, and the observation provides a valid explanation for why reproducibility of results is poor among researchers so far The influences of other parameters such as reaction temperature and CO 2 pressure on the catalytic performance of ZnBr 2 –PPh 4 I were also studied It is shown that the catalyst is sensitive to reaction temperature, and a rise of reaction temperature up to 130 °C favors the formation of cyclic carbonates We observed that activity increases with rise in CO 2 pressure and reaches a maximum at an initial CO 2 pressure of 25 MPa Moreover, a plausible reaction mechanism has been proposed

Astragalus saponins induce growth inhibition and apoptosis in human colon cancer cells and tumor xenograft

Abstract: Astragalus memebranaceus is used as immunomodulating agent in treating immunodeficiency diseases and to alleviate the adverse effects of chemotherapeutic drugs. In recent years, it has been proposed that Astragalus may possess anti-tumorigenic potential in certain cancer cell types. In this study, the anti-carcinogenic effects of Astragalus saponin extract were investigated in HT-29 human colon cancer cells and tumor xenograft. Our findings have shown that Astragalus saponins (AST) inhibit cell proliferation through accumulation in S phase and G2/M arrest, with concomitant suppression of p21 expression and inhibition of cyclin-dependent kinase activity. Besides, AST promotes apoptosis in HT-29 cells through caspase 3 activation and poly(ADP-ribose) polymerase cleavage, which is indicated by DNA fragmentation and nuclear chromatin condensation. Nevertheless, we also demonstrate the anti-tumorigenic effects of AST in vivo, of which the reduction of tumor volume as well as pro-apoptotic and anti-proliferative effects in HT-29 nude mice xenograft are comparable with that produced by the conventional chemotherapeutic drug 5-fluorouracil (5-FU). In addition, the side effects (body weight drop and mortality) associated with the drug combo 5-FU and oxaliplatin are not induced by AST. These results indicate that AST could be an effective chemotherapeutic agent in colon cancer treatment, which might also be used as an adjuvant in combination with other orthodox chemotherapeutic drugs to reduce the side effects of the latter compounds.

Involvement of cytokinins in the grain filling of rice under alternate wetting and drying irrigation

Abstract: Cytokinins may reflect soil water status and regulate rice (Oryza sativa L.) grain filling. This study investigated the changes in cytokinin levels in rice plants and their relations with grain filling under alternate wetting and drying irrigation. Two 'super' rice cultivars were field grown. Three irrigation regimes, alternate wetting and moderate soil drying (WMD), alternate wetting and severe soil drying (WSD), and conventional irrigation (CI, continuously flooded), were imposed after flowering. No significant differences in grain-filling rate, grain weight, and cytokinin content were observed for the earlier-flowering superior spikelets among the three irrigation regimes. For the later-flowering inferior spikelets, however, their grain-filling rate and grain weight were significantly increased in the WMD and significantly reduced in the WSD when compared with those in the CI. Cytokinin contents in shoots (inferior spikelets and the flag leaves) in the WMD at the soil drying time were comparable with those in the CI, but they were significantly increased when plants were rewatered. The WSD significantly reduced cytokinin contents in the shoot either during soil drying or during the rewatering period. Cytokinin contents in roots showed no significant difference between the WMD and CI regimes. The WSD increased trans-zeatin-type cytokinins, whereas it reduced isopentenyladenine-type cytokinins, in roots. Grain-filling rate and grain weight of inferior spikelets were very significantly correlated with cytokinin contents in these spikelets. The results suggest that a post-anthesis WMD holds great promise to improve grain filling of inferior spikelets through elevating cytokinin levels in the rice shoot.