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—We study the design of portfolios under a minimum risk criterion. The performance of the optimized portfolio relies on the accuracy to the estimated covariance matrix of portfolio asset returns. For large portfolios, the sample size is often of similar order to the number of assets, and the traditional sample covariance matrix performs poorly.(More)
Glabrous rice, which lacks trichomes on the rice epidermis, is regarded as an important germplasm resource in rice breeding. Trichomes are derived from aerial epidermal cells and used as a model to study the cell fate determination in plant. In Arabidopsis, the molecular mechanisms of trichome development have been well studied. However, little is known(More)
Programmed cell death (PCD) is of fundamental importance to development and defense in animals and plants. In plants, a well-recognized form of PCD is hypersensitive response (HR) triggered by pathogens, which involves the generation of reactive oxygen species (ROS) and other signaling molecules. While the mitochondrion is a master regulator of PCD in(More)
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