Cams1基因在烟草上的同源克隆及生物信息学分析

为拓宽烟草不育基因的来源,依据辣椒雄性不育基因Cams1序列,在烟草品种K326中同源克隆获得基因Ntms1,采用生物信息学方法对辣椒Cams1基因和烟草Ntms1基因的核苷酸序列、蛋白质结构、亲疏水性及结构域等进行分析,并利用CRISPR/Cas9技术对Ntms1基因功能进行了验证。结果表明,Cams1基因和Ntms1基因的蛋白质序列相似度为85.25%,基因编码产物具有相同的PHD功能结构域,都具有磷酸化识别位点,有相似的二级和三级蛋白质结构,且两个基因都没有信号肽和跨膜区的结构,推测烟草Ntms1基因与辣椒不育基因Cams1具有相似的控制育性功能。遗传转化结果表明,突变株的Ntms1基因表达量和有活力花粉量极显著低于野生型植株,证明了烟草Ntms1基因具有控制烟草花粉育性功能。     

基于免疫谱聚类的图像分割

提出了一种基于免疫谱聚类的图像分割方法.利用谱聚类的维数缩减特性获得数据在映射空间的分布,在此基础上构造一种新的免疫克隆聚类,用于在映射空间中对样本进行聚类.该方法通过谱映射为后续的免疫克隆聚类提供低维而紧致的输入.而免疫克隆聚类算法具有快速收敛到全局最优并且对初始化不敏感的特性,从而可以获得良好的聚类结果.在将其用于图像分割时,采用了Nystr?m逼近策略来降低算法复杂度.合成纹理图像和SAR图像的分割结果验证了免疫谱聚类算法用于图像分割的有效性.     

基于有序FP-tree的最大长度频繁项集挖掘算法

频繁项集的挖掘受到大量候选频繁项集和较高计算花费的限制,只挖掘最大长度频繁项集已满足很多应用。提出一种基于有序FP-tree结构挖掘最大长度频繁项集的算法。即对有序FP-tree的头表进行改造,增加一个max-level域,记录该项在有序FP-tree中的最大高度。挖掘时仅对max-level 大于等于已有最大长度频繁项集长度的项进行遍历,不产生条件模式基,无需递归构造条件FP-tree,且计算出最大长度频繁项集的支持度。实验结果表明该算法挖掘效率高、速度快。     

FP-Growth算法的改进

基于FP树的FP-Growth算法在挖掘频繁模式过程中需要两次扫描事务集来建立FP树,这不仅降低了算法的效率,而且给数据库服务器带来负担.在原有经典FP-Growth算法的基础上,提出一种基于二维表的方法对原算法进行改进,改进算法通过使用二维向量记录频繁度仅需遍历一次事务集,从而省略FP-Growth算法在生成新条件FP树时对条件模式基的第一次遍历,大大缩短了建立FP树的时间.实验结果表明,该算法的改进优于经典算法.     

一种嵌入铁电晶体管内容寻址存储器的高能效浮点运算结构

随着数据密集型应用的日益增多,内存墙问题已成为制约计算效率的瓶颈。该文提出一种新型的浮点数(FP)运算结构,该结构嵌入了基于铁电场效应晶体管(FeFET)的三元内容寻址存储器(TCAM)以实现高效的计算。通过特定规则设计的超高密度TCAM结构,可以用能效更高的TCAM搜索操作代替部分传统浮点运算,从而节约整体能耗。仿真实验证明,该文所提结构和运算执行流程,与常规浮点运算单元(FPU)相比,可以降低多达33%的能耗。     

简缩极化SAR数据信息提取与应用

全极化(FP)成像模式丰富了合成孔径雷达(SAR)数据的信息量,在地物分类、环境监测、目标探测等领域取得了广泛应用,但是全极化系统受设计和维护复杂度、功率消耗、覆盖范围和数据下传等因素影响,制约了全极化SAR的应用.简缩极化(CP)SAR系统不仅降低了全极化SAR系统的复杂度,还能在一定程度上保持全极化信息,在森林参数反演、地物分类、目标检测等领域已取得了初步的成果.本文简要介绍了简缩极化SAR系统的基本原理,阐述了简缩极化SAR的全极化信息重建及分解的主要方法,并总结其近十年的主要研究成果,最后给出了其发展趋势.     

优先级受限系统中可调度判定方法

在通信、雷达、导航以及各种消费类电子产品等民用和军事领域,嵌入式实时调度已逐渐成为电子电气系统的控制核心。针对同优先级任务使用FIFO调度的静态优先级系统,使用反例指出给定同优先级任务初始执行顺序的前提下,Katcher可调度判定条件的必要性不成立,提出并解析证明了FP可调度的充要条件。随机实验表明,对于高利用率下任务间执行时间差异较大的情况,约有15%的可调度任务集会被Katcher条件错判为不可调度。进一步的仿真和实例分析表明,Liu、Lehoczky、Bini等提出的条件不能判定相同优先级的情况,Katcher条件的必要性不成立,论文提到的条件能够正确判定任务集的可调度性。提出方法为实时系统调度的顶层设计提供了快速离线工具。     

Distribution and Antioxidant Activities of Free,Conjugated, and Insoluble-Bound Phenolics from Seven Species of the Genus Camellia

Free phenolic (FP), conjugated phenolic (CP), and insoluble-bound phenolic (IBP) acids were extracted from the seeds of seven species of oil-tea camellia and their antioxidant activities were evaluated. The results indicated that Camellia vietnamensis has the highest total phenolic content (TPC) (31.84 ± 0.11 g of gallic acid equivalent [GAE] kg⁻¹) and that Camellia polyodontia has the lowest TPC (12.34 ± 0.22 g GAE kg⁻¹) in the kernel. The average TPC among the species is similar in both the kernels and in the shells, and the content order of the three forms of phenolic compounds is FP > IBP > CP. HPLC-MS analysis showed the presence of 9–11 phenolic compounds in the FP, CP, or IBP extracts of the seven species of oil-tea camellia seed. Among the phenolics identified, ferulic acid, catechin, and epicatechin were the major contributors of antioxidant activity. Hierarchical cluster analysis conducted based on the phenolic properties showed that C. vietnamensis and Camellia semiserrata belong to the group characterized by high antioxidant capacities (FRAP, ferric-ion-reducing antioxidant power; ABTS assay), and Camellia chekiangoleosa and Camellia oleifera are arranged in a group with moderate phenolic properties. The other species constitute the third cluster with low phenolic content and antioxidant activity. The study demonstrated that oil-tea camellia seed contains significant amounts of phenolic acids. In addition, extracts from various parts of the seed could be interesting novel sources of natural antioxidants.     

基于FPGA的100MHz近红外单光子探测器

为克服InGaAs/InP雪崩二极管(APD)光电探测器的后脉冲现象,本文提出了基于FPGA的单光子探测器(SPD)测量系统,其门控频率最高可达100MHz,门控宽度最窄可到1ns,死区时间设定为109ns,并且这些参数都易于调节且有助于减少后脉冲概率。实验结果表明:在以上门控条件并且制冷温度为218K时,探测器的有效门宽为0.79ns;在死区时间超过109ns时,后脉冲现象可忽略;最大光子探测效率(PDE)约为14%;在光子探测效率为10%时,暗计数率(DCR)约为2×10-5/ns;并具有小型化、易调节的特点。     

Development of a simplified separation process of trivalent minor actinides from fission products using novel R-BTP/SiO2-P adsorbents

From a viewpoint of direct separation of trivalent minor actinides (MA: Am, Cm etc.) from fission products (FP) including rare earths (RE) in high level radioactive liquid waste, the authors have developed a simplified separation process using a single column packed with novel extraction adsorbents. Attention was paid to a new type of nitrogen-donor ligand, R-BTP (2,6-bis(5,6-dialkyl-1,2,4-triazin-3-yl)pyridine, R: alkyl group) as an extractant because it has higher extraction selectivity for Am(III) than RE(III). Since the R-BTP ligands show different properties such as adsorbability and stability when they have different alkyl groups, several R-BTP extraction adsorbents were prepared by impregnating the R-BTP ligands with different alkyl groups (isohexyl-, isoheptyl- and cyheptyl-BTP) into a porous silica/polymer composite support (SiO₂-P particles). This work investigated: (1) fundamental properties of the synthesized R-BTP/SiO₂-P adsorbents, (2) adsorption and desorption properties of Am and FP in nitric acid solution and water using the adsorbents in a batch experiment, (3) radiolytic and chemical stabilities of the adsorbents, and (4) the possibility for developing a simplified separation process of MA using the most promising adsorbent (isohexyl-BTP/SiO₂-P) under temperature control between 25 and 50°C.