R的子集的紧致性与星紧致性

给出了R的紧致子集的一个新刻画,证明了R的子集E是紧致子集当且仅当E是星紧致子集.

R的紧致子集的一个刻画

借助离散子集和相对离散子集的概念,可给出R的紧致子集的一个刻画.证明了R的子集E是紧致子集当且仅当E的每一相对离散子集是有限子集.

The Dynamical Mechanisms of the Cell Cycle Size Checkpoint

Cell division must be tightly coupled to cell growth in order to maintain cell size,whereas the mechanisms of how initialization of mitosis is regulated by cell size remain to be elucidated.We develop a mathematical model of the cell cycle,which incorporates cell growth to investigate the dynamical properties of the size checkpoint in embryos of Xenopus laevis.We show that the size checkpoint is naturally raised from a saddle-node bifurcation,and in a mutant case,the cell loses its size control ability due to the loss of this saddle-node point.

水库网箱繁育加州鲈

用三种网箱（亲鱼培育箱、产卵孵化箱、育苗箱）对加州鲈进行人工繁殖及夏花鱼种培育。从１９９６年４月下旬至５月下旬初，共催产三批次（１１０组亲鱼），获受精卵２１万粒，孵化出苗１５万尾（孵化出苗率７１．４％），育成体长３ｃｍ以上夏花鱼种４万尾。网箱培育肉食性鱼类的鱼种，主要存在着自相残杀的现象，故必须及时分筛分稀，并提供足够的适口饵料。