Abundance of moderate-redshift clusters in the Cold + Hot dark matter model

Using a set of \pppm simulation which accurately treats the density evolution of two components of dark matter, we study the evolution of clusters in the Cold + Hot dark matter (CHDM) model. The mass function, the velocity dispersion function and the temperature function of clusters are calculated for four different epochs of $z\le 0.5$. We also use the simulation data to test the Press-Schechter expression of the halo abundance as a function of the velocity dispersion $\sigma_v$. The model predictions are in good agreement with the observational data of local cluster abundances ($z=0$). We also tentatively compare the model with the Gunn and his collaborators' observation of rich clusters at $z\approx 0.8$ and with the x-ray luminous clusters at $z\approx 0.5$ of the {\it Einstein} Extended Medium Sensitivity Survey. The important feature of the model is the rapid formation of clusters in the near past: the abundances of clusters of \sigma_v\ge 700\kms and of \sigma_v\ge 1200 \kms at $z=0.5$ are only 1/4 and 1/10 respectively of the present values ($z=0$). Ongoing ROSAT and AXAF surveys of distant clusters will provide sensitive tests to the model. The abundance of clusters at $z\approx 0.5$ would also be a good discriminator between the CHDM model and a low-density flat CDM model both of which show very similar clustering properties at $z=0$.Comment: 21 pages + 6 figures (uuencoded version of the PS files), Steward Preprints No. 118

Heat conduction in 2D strongly-coupled dusty plasmas

We perform non-equilibrium simulations to study heat conduction in two-dimensional strongly coupled dusty plasmas. Temperature gradients are established by heating one part of the otherwise equilibrium system to a higher temperature. Heat conductivity is measured directly from the stationary temperature profile and heat flux. Particular attention is paid to the influence of damping effect on the heat conduction. It is found that the heat conductivity increases with the decrease of the damping rate, while its magnitude agrees with previous experimental measurement.Comment: 4 pages, 2 figures, presented in SCCS2008 conferenc

Summer Upwelling in the Northern Continental Shelf of the South China Sea

Summer upwelling system in the northern continental shelf of the South China Sea (NCSCS) is investigated with the Pathfinder, Advanced Very High Resolution Radiometer (AVHRR) Sea Surface Temperature (SST), and a three-dimensional, baroclinic, non-linear, numerical model forced by QuikSCAT winds. The AVHRR observation and modelling results have shown the upwelling is a regular phenomenon during summer in the NCSCS. Continental shelf upwelling characteristics are clearly found in the surface and subsurface water, such as low temperature, high salinity and high potential density. They respectively locate in the east of the Hainan Island, the east of the Leizhou Peninsula and the southeast of the Zhanjiang Bay (Qiongdong Upwelling), and the inshore areas from the Shantou Coast to the Nanri Islands of Fujian Coast (Yuedong Upwelling). The centra of the upwelling are mostly located in 111°10′E、19°45′N between the Qinglan Bay and the Qizhou Archipelagoes of eastern Hainan Island, 110°15′E、18°25′N near the Lingshui Bay, 116°45′E、22°50′N of the Shantou Coast and 118°E、23°40′N near the Taiwan Shoal. It is also found that the upwelling areas and centra from modelling results are in agreement with the AVHRR SST

Taxonomic status of the black porgy, Acanthopagrus schlegelii (Perciformes: Sparidae) inferred from mitochondrial genes

The black porgy Acanthopagrus schlegelii (Bleeker, 1854) is a commercially important fish distributed in estuarine and coastal waters of the west Pacific Ocean. Based on body color pattern, two subspecies A. schlegelii schlegelii (dark-unicolored specimens) and A. schlegelii czerskii (striped specimens) were suggested by some taxonomists. However, due to the morphology similarity, the phylogenetic relationship between the two subspecies has been long-lasting confused. The purpose of this study was to evaluate the taxonomic status of the two subspecies by two mitochondrial genes, cytochrome oxidase subunit І (COI) and control region (CR). Eight A. schlegelii schlegelii and eight A. schlegelii czerskii were collected from the coastal waters of the Yellow Sea, the East China Sea and the South China Sea. The genetic diversity, genetic distance and phylogenetic relationship of the two subspecies were analyzed and compared. The genetic diversity indices were close to each other in COI, but more different in CR. The mean genetic distances between the two subspecies was 0.0015 in COI and 0.0051 in CR, respectively. These values are much lower than those found for interspecific COI and CR comparisons among some species of Acanthopagrus (0.0667 to 0.0954 in COI and 0.2267 to 0.2480 in CR). Moreover, haplotypes of the two subspecies did not form reciprocal monophyletic clades in the phylogenetic trees based on the two mitochondrial genes. These results indicate that the genetic distance between the two subspecies, A. schlegelii schlegelii and A. schlegelii czerskii, was at the intraspecies level; they should be classified into the same species: A. schlegelii. It is suggested that A. schlegelii schlegelii and A. schlegelii czerskii should be regarded as the junior synonyms of A. schlegelii.Key words: Acanthopagrus schlegelii schlegelii, A. schlegelii czerskii, mitochondrial DNA, molecular phylogeny, taxonomic status

Dynamical interaction between information and disease spreading in populations of moving agents

Copyright © 2018 Tech Science Press. Considering dynamical disease spreading network consisting of moving individuals, a new double-layer network is constructed, one where the information dissemination process takes place and the other where the dynamics of disease spreading evolves. On the basis of Markov chains theory, a new model characterizing the coupled dynamics between information dissemination and disease spreading in populations of moving agents is established and corresponding state probability equations are formulated to describe the probability in each state of every node at each moment. Monte Carlo simulations are performed to characterize the interaction process between information and disease spreading and investigate factors that influence spreading dynamics. Simulation results show that the increasing of information transmission rate can reduce the scale of disease spreading in some degree. Shortening infection period and strengthening consciousness for self-protection by decreasing individual’s scope of activity both can effectively reduce the final refractory density for the disease but have less effect on the information dissemination. In addition, the increasing of vaccination rate or decreasing of long-range travel can also reduce the scale of disease spreading