DNA序列中基于后继数组索引的LPR查找算法

DNA序列中的重复片段在人类基因研究中有着非常重要的生物意义,因此,查找给定DNA序列中的重复片段是生物序列分析领域中的一个重要课题.基于重复片段的模式提出了新的重复片段定义LPR(largest pattern repetition)和模式单元的概念.对于长度为n的DNA序列,其中的LPR的数量是O(n)数量级的,但提供了与个数可多达n2/4的tandem repeat相同的重复片段信息.基于模式单元设计了可用于重复片段查找的全新索引--后继数组.后继数组有效地降低了索引空间,很好地突破了重复片段查找中的索引空间瓶颈.在后继数组上,通过模式单元可发现构成LPR的全部原子模式,并通过判断相同模式是否在原序列中连续出现完成LPR的查找.理论分析和实验结果均表明,设计的LPR查找算法的时间和空间复杂度均为O(n).     

Preparation and characteristic research of anhydrous magnesium chloride with dehydrated ammonium carnallite

Taking the saline lake bischofite and NH4Cl that was removed with the ammonia method and continuously followed by filtration as raw materials with a molar ratio of 1 ： 1 of MgCl2 to NH4Cl, ammonium carnallite was synthesized. And then the ammonium carnallite was dehydrated to some extent at 160 ℃ for 4 h. Ammonium carnallite reacted with ammonia at 240 ℃ for 150 min and the ammonation ammonium carnallite was produced. Finally, the ammonation ammonium carnallite was calcined at 750 ℃ into anhydrous magnesium chloride containing only 0.1% （mass fraction） of MgO. On the other hand, dehydrated ammonium carnallite was mixed with the solid ammonium chloride at mass ratio 1 ： 4 at high temperature and with the differential pressure of NH3 above 30.5 kPa. The dehydrated ammonium carnallite of mixture was dehydrated at 410 ℃, and then calcined at 700 ℃ into anhydrous magnesium chloride with only 0. 087% （mass fraction） of MgO. X-ray diffraction and electron microscopy analysis results prove that anhydrous magnesium chloride obtained by both methods hasn＇t mixed phases,the particle is large and even has good dispersion, which is suitable for preparation of metal magnesium in the electrolysis.