扇蜗同心环组合式相控阵列的超声场优化

以扇蜗同心环组合式相控阵列为研究对象,推导出超声场的计算公式,以及伪逆矩阵算法的超声合成方法。结合遗传算法,以强度增益作为适应度函数,通过改变声压的相角搜索其空间最优解,采用MATLAB编程仿真分析声场优化。结果显示:聚焦效果理想,焦平面位于几何焦点处;峰值尖锐,声强较大;焦点尺寸和旁瓣小。

Development of 101 Novel EST-Derived Single Nucleotide Polymorphism Markers for Zhikong Scallop (Chlamys farreri)

Zhikong scallop(Chlamys farreri) is an important maricultured species in China.Many researches on this species,such as population genetics and QTL fine-mapping,need a large number of molecular markers.In this study,based on the expressed sequence tags(EST),a total of 300 putative single nucleotide polymorphisms(SNPs) were selected and validated using high resolution melting(HRM) technology with unlabeled probe.Of them,101(33.7%) were found to be polymorphic in 48 individuals from 4 populations.Further evaluation with 48 individuals from Qingdao population showed that all the polymorphic loci had two alleles with the minor allele frequency ranged from 0.046 to 0.500.The observed and expected heterozygosities ranged from 0.000 to 0.925 and from 0.089 to 0.505,respectively.Fifteen loci deviated significantly from Hardy-Weinberg equilibrium and significant linkage disequilibrate was detected in one pair of markers.BLASTx gave significant hits for 72 of the 101 polymorphic SNP-containing ESTs.Thirty four polymorphic SNP loci were predicted to be non-synonymous substitutions as they caused either the change of codons(33 SNPs) or pretermination of translation(1 SNP).The markers developed can be used for the population studies and genetic improvement on Zhikong scallop.

Molecular cloning and characterization of SoxB2 gene from Zhikong scallop Chlamys farreri

The Sox proteins play critical roles during the development of animals, including sex determination and central nervous system development. In this study, the SoxB2 gene was cloned from a mollusk, the Zhikong scallop （Chlamysfarreri）, and characterized with respect to phylogeny and tissue distribution. The full-length cDNA and genomic DNA sequences of C. farreri SoxB2 （CflSoxB2） were obtained by rapid amplification of cDNA ends and genome walking, respectively, using a partial cDNA fragment from the highly conserved DNA-binding domain, i.e., the High Mobility Group （HMG） box. The full-length cDNA sequence of CJSoxB2 was 2 048 bp and encoded 268 amino acids protein. The genomic sequence was 5 551 bp in length with only one exon. Several conserved elements, such as the TATA-box, GC-box, CAAT-box, GATA-box, and Sox/sry-sex/testis-determining and related HMG box factors, were found in the promoter region. Furthermore, real-time quantitative reverse transcription PCR assays were carried out to assess the mRNA expression of CJSoxB2 in different tissues. SoxB2 was highly expressed in the mantle, moderately in the digestive gland and gill, and weakly expressed in the gonad, kidney and adductor muscle. In male and female gonads at different developmental stages of reproduction, the expression levels of CfS;oxB2 were similar. Considering the specific expression and roles of SoxB2 in other animals, in particular vertebrates, and the fact that there are many pallial nerves in the mantle, cerebral ganglia in the digestive gland and gill nerves in gill, we propose a possible essential role in nervous tissue function for SoxB2 in C.farreri.

The phylogeny of native and exotic scallops cultured in China based on 16S rDNA sequences

Scallops of the Family Pectinidae are a valuable resource in marine industry of the world. Understanding the phylogeny of the family is important for the development of the industry. In this study, partial 16S mitochondrial rDNA genes were obtained from 8 scallop species that are commonly cultured indigenous and transplanted species in China. Phylogenetic relationships of Pectinidae were analyzed based on the 8 sequences and other 5 published ones in GenBank, representing 9 genera of the family. The molecular phylogeny trees were constructed using 3 methods with software PHYLIP. The results showe that total 13 species of scallops clustered in 4 clades. Pecten maximus joins P. jacobaeus then Amusium pleuronectes in cluster, indicating close relationship of genus Amusium with Pecten in evolution. P. yes- soensis is close to Chlamys farreri and C. islandica. No enough material was available to single out genus Patinopecten as an independent monophyletic subfamily. The position of Adamussium colbecki indicates that it is far from genus Pecten but near to genus Chlamys in evolution.

An improved SVPWM control algorithm for three-level inverter

In the traditional three-level space vector pulse width modulation(SVPWM)algorithm,the sector judgment is computationallycomplex since the sector is divided into triangles and hexagons.In addition,the switching frequency is high becausethe seven-segment switching sequence is adopted.For this reason,a new SVPWM control algorithm for three-level inverteris proposed,in which the sector judgment is simplified by dividing the sector into quasi hexagons?and the new four-segmentswitching sequence is adopted to reduce the switching frequency.Simulation results show that the total harmonic distortiongrows down with the switching frequency decreasing,moreover,the algorithm runtime is also decreased.

Yield trait improvement of bay scallops following complete diallel crosses between different scallop stocks

This study describes the complete diaUel hybridization between newly introduced bay scallop stock （W） from Canada and local commercial stock （D） grown under laboratory conditions, in China. Larval survival and growth during all life stages （larvae, spat, and adult） were compared among hybrid （DW, WD） and purebred （DD, WW） populations. Significant heterosis was detected for survival during the larval stage （〉 1% of the mid-parent values）. The mean heterosis （Hm） varied in growth throughout the life span. More than 50% of the Hm values were positive and negative in the DW and WD groups, respectively. The influence of maternal effects and mating types （intrapopulation vs. interpopulation crosses） on growth for all life stages was not consistent. Larval survival did not differ significantly （P〉0.05） with maternal effect or mating type. In the harvest stage, shell length （SL）, shell height （SH）, shell width （SW）, and total weight （TW） were larger in the hybrid compared with the inbred groups. Positive Hm values were observed in SL （1.5%）, SW （5.8%）, and TW （12.3%）, and were more significant in the DW groups （6.1%, 4.5%, 6.8%, and 27.2%）. These results suggest that hybridization between two geographic populations is a good tool for improving bay scallop growth. However, unstable heterosis between the two populations requires further study.

云冈石窟雕刻中的屋顶“檐角”做法及其特点

云冈石窟雕刻中的楼阁式佛塔与殿宇(屋形龛),从表现形式与结构特征看,北魏时期檐椽有两种不同的排列方式,即平列式与扇列式,代表了当时庑殿顶檐角不同的结构法;从屋顶檐角的排列方式上看,应该与北魏木构架建筑的通行做法一样的,可用来标证北魏时代的建筑式样和技艺特点,为研究南北朝时期的木结构建筑提供了宝贵的资料。