Phylogeography of the pelagic fish Seriola lalandi at different scales: confirmation of inter-ocean population structure and evaluation of southern African genetic diversity

The study investigated the global and regional phylogeography of the yellowtail kingfish Seriola lalandi by examining genetic diversity and population genetic structure of this species at inter-and intra-ocean level and on a regional scale. DNA fragments of two mitochondrial genes, cytochrome b (Cytb) and cytochrome c oxidase subunit I (COI) and one nuclear gene, recombination activating gene 1 (RAG1), were sequenced to investigate the global-scale phylogeography of this species. The population genetic structure within the South Pacific, as well as along the South African coastline, was examined further using six microsatellite markers. Three distinct clades were identified for S. lalandi, which correspond with previously described subspecies of the North-East Pacific, North-West Pacific and the Southern Hemisphere. Within the latter, additional divergence was observed between the South Pacific and the South-East Atlantic regions. Divergence estimates were indicative of a Pacific origin for S. lalandi populations, because of Pleistocene vicariant events. Microsatellite analyses revealed overall significant genetic differentiation between South African and South Pacific samples. This corroborates recent findings on the global phylogeography of the species. No population differentiation was observed within South Africa, indicating high levels of gene flow.     

Review of Lagrangian stochastic models for trajectories in the turbulent atmosphere

We review the theoretical basis for, and the advantages of, random flight models for the trajectories of tracer particles in turbulence. We then survey their application to calculate dispersion in the principal types of atmospheric turbulence (stratified, vertically-inhomogeneous, Gaussian or non-Gaussian turbulence in the surface layer and above), and show that they are especially suitable for some problems (e.g., quantifying ground emissions).     

Rotation Of Trajectories In Lagrangian Stochastic Models Of Turbulent Dispersion

We present a new measure for the rotation of Lagrangian trajectories in turbulence that simplifies and generalises that suggested by Wilson and Flesch ( Boundary-Layer Meteorol. 84, 411–426). The new measure is the cross product of the velocity and acceleration and is directly related to the area, rather than the angle, swept out by the velocity vector. It makes it possible to derive a simple but exact kinematic expression for the mean rotation of the velocity vector and to partition this expression into terms that are closed in terms of Eulerian velocity moments up to second order and unclosed terms. The unclosed terms arise from the interaction of the fluctuating part of the velocity and the rate of change of the fluctuating velocity.We examine the mean rotation of a class of Lagrangian stochastic models that are quadratic in velocity for Gaussian inhomogeneous turbulence. For some of these models, including that of Thomson ( J. Fluid Mech. 180, 113–153), the unclosed part of the mean rotation vanishes identically, while for other models it is non-zero. Thus the mean rotation criterion clearly separates the class of models into two sets, but still does not provide a criterion for choosing a single model.We also show that models for which = 0 are independent of whether the model is derived on the assumption that total Lagrangian velocity is Markovian or whether the fluctuating part is Markovian.     

Probability Density Function Integrals And Small-Scale Mixing In Turbulent Plumes

We analyse cross-wind-integrated statistics of theconcentration field of a conserved scalar for pointand line sources in grid turbulence. In particular,using wind-tunnel measurements we calculate thecross-wind integrated probability density function(pdf) for the scalar concentration. We then use thatquantity in the exact evolution equation for the pdfto calculate the cross-wind integrated mean of therate of dissipation of scalar variance, conditional onthe scalar concentration. Much of the variation ofthese statistics with distance downstream is accountedfor by scaling with concentration, length and timescales based on the development of the mean plume.This scaling thus suggests some simple practicalparameterisations of these statistics in terms ofmean-field quantities. One of the motivations for thiswork is to find a simple parameterisation for thescalar dissipation that can be used for modellingchemical reactions in plumes.We also consider the cross-wind integral of the firstfew moments of the concentration field and show thatthe integration greatly simplifies the budgets forthese moments. Thus the first moment is just thedownstream flux of the scalar, which is constant. Thesecond moment budget provides a check on the meandissipation estimated directly from the pdf evolutionequation.     

大兴安岭中南段中生代成矿物质的深部来源与背景

大兴安岭是我国北方一个重要的多金属成矿带。本文从成矿的物质来源和构造作用两方面讨论大兴安岭的成矿系统。Sr、Nd、O、Pb同位素的研究显示大兴安岭成矿物质的深部来源,大兴安岭晚中生代壳幔混熔花岗质岩石组成及其构造环境的研究,表明它们是在板内非造山的伸展环境下形成的A型花岗岩。与南岭花岗岩及其成矿作用的对比研究,将加深对大兴安岭中生代成矿特征的认识。深部构造特征也进一步印证了大兴安岭的成岩-成矿的背景。     

辽宁盖县梁屯—矿洞沟碱性正长岩杂岩体的U—Pb和Sm—Nd年龄及其地质意义

辽宁梁屯 -矿洞沟杂岩体主要由辉石正长岩、霓辉正长岩和霓辉角闪正长岩等碱性岩石组成 ,具有全岩 Rb- Sr等时线年龄 186 6± 115 Ma和 ISr=0 .70 4 9的同位素特征 ,是我国目前报道的最古老的碱性正长岩类。本文报道了该岩体的锆石U- Pb和全岩 Sm- Nd同位素测试资料 ,获得了锆石 U- Pb同位素年龄为 185 7± 2 0 Ma、Sm- Nd等时年龄为 1787± 180 Ma、εNd(t) =- 4 .8～ - 5 .0的数据。它们反映出该杂岩体形成年龄的上限为 185 7± 2 0 Ma、下限不小于 1787± 180 Ma,来源于富集地幔物质。基于这些数据并结合区域地质资料分析 ,作者提出了华北地台北缘古元古宙存在有富集地幔储库 ,以及辽河群主体形成于 190 0 Ma以前的认识     

Atmospheric boundary-layer measurements of concentration statistics from isolated and multiple sources

Atmospheric tracer dispersion experiments have been carried out to measure the statistical characteristics (variance, frequency distribution, spectrum) of the concentration downwind of a pair of partly overlapping plumes. By releasing different tracer substances from each source, it was possible to identify the contributions of the two sources at a given measurement point, both separately and jointly, and thus to compare and interpret the joint statistics in terms of those from the individual sources.Statistics for the individual sources agree well with, and support, existing wind tunnel and theoretical results. Nondimensionalization of the data using the mean concentration and the lateral width of the plume as concentration and length scales successfully removes much of the variation due to changes in atmospheric and surface conditions.Measurements of the correlation between the concentration contributions from separated sources are consistent with recent wind tunnel measurements. Entirely new measurements of the frequency distribution of the combined concentration from a pair of sources show that in many situations, high concentrations relative to the mean occur much less frequently than for an isolated source. Generally the extent of the reduction in frequency of occurrence is inversely related to the degree of correlation between concentrations from the two sources.     

Lagrangian statistical simulation of the turbulent motion of heavy particles

A Lagrangian stochastic model for the motion of heavy particles has been developed by coupling a stochastic model for the motion of fluid elements to the Stokes equations of motion of a particle in a turbulent flow. The effects of crossing trajectories and continuity are incorporated by generalising Csanady's (1963) ideas developed for stationary homogeneous turbulence; effects of turbulence inhomogeneity and nonstationarity are embodied in the stochastic model for the fluid motion.The model has been used particularly to examine the effects of turbulence nonstationarity through simulations of the dispersion of heavy particles in the decaying homogeneous turbulence which is obtained by Taylor-transforming grid turbulence. Significant differences from the stationary case occur, mainly as a result of the growth of the turbulent time scale with time.The importance of the source location in influencing both passive scalar and particle dispersion in grid turbulence is highlighted by the model and can be simply accounted for by nondimensionalisation using the r.m.s. turbulence velocity at the source and the mean travel time from the grid to the source as velocity and time scales, respectively. Reconciliation of the three different experiments of Snyder and Lumley (1971), Wells and Stock (1983) and Ferguson (1986) reporting heavy particle flow and dispersion statistics in wind tunnel grid turbulence has been attempted using this nondimensionalisation. A good correspondence between the various data sets was not obtained because the source in the Wells and Stock, and Ferguson experiments was located at the grid where the self-similar development of the turbulence which underlies the scaling is not appropriate.The model matches the data for the heaviest particles used by Snyder and Lumley reasonably well. For very light particles, it correctly reverts to the passive scalar limit, while the experimental data in general do not properly approach this limit.     

Design criteria for water tank models of dispersion in the planetary convective boundary layer

Design criteria for laboratory water-analogs of clear-air penetrative convection in the atmosphere are described. Consideration is given to the range of factors relevant to modelling both turbulent penetrative convection and the dispersion of buoyant point-source plumes within the convective boundary layer. Scaling arguments based on mixed-layer and plume scaling show that at typical laboratory scales, saline convection can satisfy the requirements for modelling buoyant plume dispersion under strongly convective (light wind) conditions better than heated water tanks or wind tunnels.     

A saline laboratory model of the planetary convective boundary layer

A laboratory water-analog of clear-air penetrative convection in the atmosphere has been constructed to continue studies of the turbulent dispersion of buoyant plumes in the convective boundary layer (CBL). A unique feature is the utilization of saline rather than thermal convection, which has been made possible by the development of a reliable method for delivering a controllable buoyancy flux through a porous membrane. It has been shown in an earlier paper that at typical laboratory scales, a saline convection tank is well suited to modelling buoyant plume dipersion under strongly convective (light wind) conditions.A range of experiments has clearly demonstrated the validity of the model. Results for density and velocity variances show much less scatter than most comparable measurements because of the greatly improved sampling that is possible in the tank. The results are generally in good agreement with field data and other laboratory simulations but the improved accuracy of the data has highlighted the anomalously low values for the horizontal velocity variances produced by large-eddy simulations of the CBL. The cause of this apparent underprediction remains unresolved.