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The high-speed metal jet generated by the high explosive antitank method to damage the armor vehicles and tanks. The penetration capacity of the high-speed metal jet is proportional to the effective length of the metal jet. In order to improve the effective length of the metal jet, an electromagnetic enhancing system is put forward, and its principle is introduced. The time sequence of the high-speed metal jet and the pulsed magnetic field is analyzed, and the determination method of the time sequence is obtained. Furthermore, the simulation model of the electromagnetic enhancing system is established based on finite element method, and the distribution characteristics of the discharge current, magnetic field, and the electromagnetic force are obtained. Finally, an experiment system of the electromagnetic enhancing system is built and some verification experiments are carried out. With the analysis and the experiments, the conclusions as follows can be drawn: the high-speed metal jet will be reshaped with the effect of the axial pulsed magnetic field, and the effective length will be improved. Furthermore, the optimal time sequence is that when the central sections of the metal jet and magnetic field coil coincide, the discharge current of the magnetic field coil just reaches its peak point.

To assess the genetic background of the germplasm resource of rainbow clam Moerella iridescens along China coasts, population genetic structure and genetic diversity of rainbow clam from five geographical populations in the Yellow Sea and the East China Sea (Lianyungang, Chongming, Cixi, Zhoushan, and Ningde) were analyzed based on rDNA (ITS1-5.8S-ITS2) sequences. Forty-Seven rDNA haplotypes were identified among 109 rainbow clam individuals of the five populations. Gen4 and Gen21 were the dominant haplotypes, accounting for 49.5% of rDNA whole gene sequences, and shared by the five populations. Six to eight exclusive haplotypes were found in each population. The average haplotype diversity index (HD) of the five populations was 0.8733. The genetic distance among populations ranged from 0.002 to 0.004, and haplotypes from the same population were not clustered in a single clade. Molecular variance analysis (AMOVA) demonstrated that the main genetic differentiation mainly occurred within population, and the genetic differentiation coefficient (FST) among five populations was between -0.02836 and 0.01896, which meant that no genetic differentiation among populations occurred. Overall, the five geographical populations showed a high genetic diversity, but no evident genetic structure or genetic differentiation.

Background To avoid destructive sampling for conservation and genetic assessment, we isolated the DNA of clam Cyclina sinensis from their feces. DNA electrophoresis and PCR amplification were used to determine the quality of fecal DNA. And we analyzed the effects of different conditions on the degradation of feces and fecal DNA. Results The clear fecal DNA bands were detected by electrophoresis, and PCR amplification using clam fecal DNA as template was effective and reliable, suggesting that clam feces can be used as an ideal material for noninvasive DNA isolation. In addition, by analyzing the effects of different environmental temperatures and soaking times on the degradation of feces and fecal DNA, we found that the optimum temperature was 4 °C. In 15 days, the feces maintained good texture, and the quality of fecal DNA was good. At 28 °C, the feces degraded in 5 days, and the quality of fecal DNA was poor. Conclusions The clam feces can be used as an ideal material for noninvasive DNA isolation. Moreover, the quality of fecal DNA is negatively correlated with environmental temperature and soaking time.

Additional file 2: Figure S2. Agarose gel electrophoresis of PCR amplification products Lane M, DNA marker; lane N, negative control; lane F, PCR amplification products of foot DNA; lanes 1–20, PCR amplification products of fecal DNA (N = 20).

In statistics mean absolute deviation plays an important role in measuring spread of a data. In this paper, we focus on using the jackknife, the adjusted and the extended jackknife empirical likelihood methods to construct confidence intervals for the mean absolute deviation of a random variable. The empirical log-likelihood ratio statistic is derived whose asymptotic distribution is a standard chi-square distribution. The results of simulation study show the comparison of the average length and coverage probability by using jackknife empirical likelihood methods and normal approximation method. The proposed adjusted and extended jackknife empirical likelihood methods perform better than other methods, in particular for skewed distributions. We use real data sets to illustrate the proposed jackknife empirical likelihood methods.

To improve the defense capability of passive electromagnetic armor against shaped-charge jet (SCJ), according to the superposition principle and the linear perturbation theory, the SCJ disturbance control equations are constructed and the 3-D equation is reduced to 1-D equation, consequently, the instability growth rates of the pinch and kink of SCJ and the varying law of instability growth rates with time and yield stress are obtained under the axial pulse current, which indicate that the instabilities must occur as long as the perturbations exit. Meanwhile, the SCJ deformation can be calculated through numerical method. The pinching experiments with a 39.2-mm diameter armor-piercing projectile proceeded when the charging voltage is 5370 V and the peak current is 140 kA. The kinking experiments with a 1.75-mm diameter copper wire proceeded when the charging voltage is 5140 V and the peak current is 43 kA. The experimental results demonstrate that axial pulse current can destroy the SCJ because of necking or kinking perturbation and confirm the validity of the theoretical analysis.

Coelomactra antiquata is a famous delicacy and a promising new candidate for aquaculture, which belongs to the family Mactridae (Mollusca: Veneroida). The complete mitochondrial genome of C. antiquata (Liao Ning province, in China, LN) was finished, which is the first representative from this province. The results showed that the total length of LN-mtDNA sequence is 16,797 bp and the content of A + T is 65.01%. It encodes 35 genes, including 12 protein-coding genes, 21 transfer RNA genes and two ribosomal RNA genes. All coding genes are encoded on the heavy strand. Compared with the typical gene content of animal mitochondrial genomes, atp8 and trnSer(UCN) genes are missing in the mitochondrial genome. The complete mitochondrial genome contains 26 non-coding regions (1598 bp), one major non-coding region consists of 1046 bp in which 4.9 tandem repeat sequences (99bp per sequence) was observed. The phylogenetic tree showed that Liaoning population was clustered into one clade with Shandong (Rizhao, Jiaonan and Jimo) and Guangxi (Beihai) populations, meanwhile all of them are far from the Fujian populations (Pingtan, Zhangzhou and Changle). So, Liaoning, Shandong and Guangxi populations have a close relationship. Actually, Fujian is located between Liaoning, Shandong and Guangxi. So, the result challenges the previously assumed relevance between geographic distance and genetic distance. The genetic distance of Liaoning C. antiquata and Fujian (Changle, Zhangzhou and Pingtan) C. antiquata (0.176–0.177) is greater than the genetic distance between Mytilus galloprovincialis and Mytilus trossulus (0.160). The genetic difference of Liaoning population and Fujian populations has reached species level.

Complete mitochondrial genome plays an important role in the accurate revelation of phylogenetic relationships among metazoans. Here we present the complete mitochondrial genome sequence from a sea cucumber Apostichopus japonicus (Echinodermata: Holothuroidea), which is the first representative from the subclass Aspidochirotacea. The mitochondrial genome of A. japonicus is 16,096 bp in length. The heavy strand consists of 31.8% A, 20.2% C, 17.9% G, and 30.1% T bases (AT skew = 0.027: GC skew = 0.062). It contains thirteen protein-coding genes (PCGs), twenty-two transfer RNA genes, and two ribosomal RNA genes. There are a total of 3793 codons in all thirteen mitochondrial PCGs, excluding incomplete termination codons. The most frequently used amino acid is Leu (15.77%), followed by Set (9.73%), Met (8.62%), Phe (7.94%), and Ala (7.28%). Intergenetic regions in the mitochondrial genome of A. japonicus are 839 bp in total, with three relatively large regions of Unassigned Sequences (UAS) greater than 100 bp. The gene order of A. japonicus is identical to that observed in the five studied sea urchins, which confirms that the gene order shared by the two classes (Holothuroidea and Echinoidea) is a ground pattern of echinoderm mitochondrial genomes. Bayesian tree based on the cob gene supports the following relationship: (outgroup, (Crinoids, (Asteroids, Ophiuroids, (Echinoids, Holothuroids)))). (C) 2009 Elsevier B.V. All rights reserved.

Interest in meshfree (or meshless) methods has grown rapidly in recent years in solving boundary value problems (BVPs) arising in mechanics, especially in dealing with difficult problems involving large deformation, moving discontinuities, etc. In this paper, we provide a theoretical analysis of the reproducing kernel particle method (RKPM), which belongs to the family of meshfree methods. One goal of the paper is to set up a framework for error estimates of RKPM. We introduce the concept of a regular family of particle distributions and derive optimal order error estimates for RKP interpolants on a regular family of particle distributions. The interpolation error estimates can be used to yield error estimates for RKP solutions of BVPs.