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Articles by Lu Li
Total Records ( 2 ) for Lu Li
  Lu Li , Xuan Wang and XiaoLong Wang
  Conditional maximum entropy models provide a unified framework to integrate arbitrary features from different knowledge sources and have been successfully applied to many natural language processing tasks. Feature selection methods are often used to distinguish good features from bad ones to improve model performance. The selection of features in traditional methods is often performed based on different strategies before or along with feature weight estimation, however, weights themselves should be the only factor to measure the importance of features. This study proposes a new selection method based on divide-and-conquer strategies and well-trained feature spaces of small sizes. Features are divided into small subsets, on each of which a sub-model is built and its features are judged according to their weights. The final model is constructed based on merged feature space from all sub-models. Experiments on part of speech tagging show that this method is feasible and efficient.
  Lu Li , Dong Zhang , Junhai Lian and Huanmin Zhou
  This study aimed to measure the concentration of intracytoplasmic free-Ca2+ in the in vitro matured bovine oocytes at MII stage and in the in vitro fertilized embryos at early different developmental stages 0 h (fertilization), 2 and 15 h (pronucleus stage) and 48 h (2-cell stage) after fertilization using Fura-2/AM as a Ca2+ fluorescent probe and to investigate Ca2+ spatial distribution in the intracytoplasm of bovine eggs at MII stage and 0, 2, 15 and 48 h after fertilization using Ca2+ fluorescent probe Fluo-3/AM. Meanwhile, the fertilized eggs were cultured in Ca2+-free culture medium to examine the effects of extracellular Ca2+ on the early embryo development. The results indicated that the intracellular Ca2+ concentrations of the bovine oocytes at MII stage and 0, 2, 15 and 48 h after fertilization were 84.99 nmol L-1 and 120.05, 229.09, 108.73 and 111.17 nmol L-1, respectively. No pronuleus or cleft eggs were found when cultured in Ca2+-free culture medium. These results suggested that the fertilization induced intracytoplasmic free-Ca2+ increase that pronucleus formation and egg cleavage were Ca2+ dependent that extracellular Ca2+ performed a specific function for the initiation of zygote development and that comparatively, a high level of Ca2+ concentrations was still maintained after pronucleus formation. Moreover, the spatial profile of fluorescence expression illustrated that a low density free-Ca2+ were homogenously distributed in the cytoplasm of oocytes at MII stage, the Ca2+ were concentrated at the cortex zone under the egg plasma membrane at fertilization, the Ca2+ intensity enhanced and spread towards the center of egg from edge at 2 h after fertilization and the Ca2+ were distributed in whole cytoplasm at pronucleus and first cleavage stage. These results demonstrated that extracellular Ca2+ is essential for normal embryonic development and also, confirm that Ca2+ increase is required for bovine oocyte activation at fertilization.
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