Communal suckling in the cavy Galea musteloides

We quantified the extent of communal suckling in the cavy Galea musteloides. Six groups of animals were held in large indoor enclosures and suckling behavior was recorded over 113 h of observation. The groups contained 2–6 lactating females and 3–14 sucking pups. Due to the relative synchronization of births, 73% of the pups present in each group during lactation were non-offspring. Each of the 22 lactating females in the six groups suckled non-offspring in addition to her own offspring. On average, females suckled 86% of non-offspring present in their groups. Thus, 98% of all pups (n = 47) received milk from non-mothers. Although suckling frequencies were significantly higher for mothers with their own individual offspring than with non-offspring individuals, females invested more total time suckling all non-offspring than did suckling just their own; this was possible because for each mother many more non-offspring than offspring pups were present during lactation. Suckling bouts were significantly longer for mothers with their own individual offspring than with non-offspring individuals. The proportion of non-offspring suckling of mothers correlated negatively with the proportion of own young among the pups of a group. Non-offspring suckling did not affect future reproduction of females. Our observations demonstrate extensive practice of communal suckling in G. musteloides under laboratory conditions. Probably because all mothers of a group participated more or less equally in communal suckling behavior, the obvious cost of giving energetically expensive milk to non-offspring did not result in reduced (future) reproductive success. Potential benefits directly involved with communal suckling are unclear. More indirectly, communal suckling as well as birth synchrony might contribute to the formation of advantageous multi-litter kindergardens.     

An application of the theory of kinematics of mixing to the study of tropospheric dispersion

The most common technique used for numerical simulations of tracer mixing is that of the numerical solution of the advection–diffusion equation with the unresolved fluxes parameterized using the similarity theory. Despite correct predictions of the overall directions of transport, models based on a numerical solution of the advection–diffusion equation lack sufficient accuracy to correctly reproduce the coupling of mixing with small scale processes which are sensitive to the microstructure of the tracer distribution. The objective of this paper is to revisit the basic formalism employed in numerical models used to investigate atmospheric tracers. The main mathematical method proposed here is the theory of kinematics of mixing which could be applied effectively for simulations of atmospheric transport processes. At the beginning of the paper, we introduce simple mathematical transformations in order to demonstrate how complex topological structures are created by mixing processes. These idealistic flow systems are essential to explain transport properties of much more complex three-dimensional geophysical flows. An example of the application of the kinematics of mixing to the analysis of tracer transport on a planetary scale is presented in the following sections. The complex filamentary structures simulated in the numerical experiment are evaluated using some commonly applied statistical measures in order to compare the results with the data published in the literature. The results of the experiment are also analysed with the help of simple conceptual models of fluid filaments. The microstructure of the tracer distribution introduced in the paper is essential to increase our understanding of atmospheric transport and to develop more realistic parameterizations of small-scale mixing. The presented results could also be used to improve calculations of the coupling between microphysical processes and tracer mixing.     

贵州连续性碳酸盐岩上覆景观特征的定量研究

利用GIS软件,探讨了贵州以连续性碳酸盐岩为基底地区的上覆景观单元、破碎化及斑块分形的特征及其形成原因。研究区域中,受岩性控制景现在整体上体现出一致性的基础上,又存在着明显的内部差异性。一致性表现为以灌木林地为优势景观,森林和草地中以次生景观为主,偏小的斑块占大多数,斑块大小分布全为正偏, 其分布曲线多为尖峭峰,斑块研究不存在面积上尺度域,斑块形状在人为强烈干扰下趋于规则而导致类型分维数的值偏小,人为干扰大的景观中斑块的破碎化更加明显。相比连续性白云岩地区,连续性石灰岩地区的水资源利用率低下,抗干扰能力弱,景观多样性不均衡,退化更严重,分割程度更破碎,空间异质性更强,稳定性差,易向逆向演替的方向发展。     

湘江霞湾段汞环境容量模型研究

根据湘江霞湾段水力学特征及向家塘断面水质要求 ,在综合分析多年水文参数和相应环境监测数据的基础上 ,建立了一套适合该江段的汞环境容量模型。经检验 ,模型预测值与实测值吻合良好 ,该模型可用于预测预报该江段在不同水文条件下汞的环境容量及水体中汞的浓度分布变化规律 ,以利调控汞污染源的排放强度和总量     

人类活动对北京东灵山地区景观格局影响分析

干扰改变景观格局,同时又受景观格局的影响,干扰是景观异质性的一个主要来源。应用ＩＬＷＩＳ地理信息系统,以１∶２００００植被图为基础,结合野外考察,分析了北京东灵山地区森林景观空间格局,采用缓冲区分析方法,研究了人类活动对该地区森林景观格局的影响。研究结果表明,在东灵山地区,人类活动的强弱与景观的破碎化表现出一定的相关性。人类作用强的地区斑块面积较小,作用弱的地区斑块面积较大,人类的活动对该地区的景观破碎化产生了明显的影响。随着距所选择的干扰区的远近,几个景观多样性指数没有表现出有规律的大小变化。虽然该地区人类活动有愈来愈强的趋势,但目前决定该地区景观空间格局的因子主要还是自然要素,人类活动虽然也对该区的景观格局产生了一定的影响,但还不是决定因素     

Buoyancy-Driven Two-Layer Exchange Flows Across a Slowly Submerging Barrier

Results are presented from a combined analytical and laboratory study of unsteady, two-layer, density-driven, sub-maximal exchange over a slowly-descending estuarine barrier located very close to the junction of the river mouth and the near-shore coastal zone. As in the precursor study (Cuthbertson et al. 2004, Environ. Fluid Mech. 4, 127–155) that the present investigation extends, the rate of descent of the barrier is assumed to be sufficiently slow for the unsteady exchange flow to adjust continuously to the appropriate quasi-steady conditions at every stage of the descent. The results demonstrate that the thickness of each layer at the barrier crest can be predicted satisfactorily by a hydraulic analysis that (i) assumes the existence of a single control point at the barrier crest and (ii) incorporates the hydraulic losses arising from the sudden expansion and contraction of the upper and lower layers, respectively, at the channel exit. Predictions of the normalised elevations of the interface at the barrier and exit for the “inviscid” maximal exchange case are shown to coincide with the maximal exchange predictions of Zhu and Lawrence (2000, J. Hydraul. Eng. ASCE 126(12), 921–928).     

A Modelling Study of Transient,Buoyancy-Driven Exchange Flow over a Descending Barrier

Results are presented from a series of model studies of the transient exchange flow resulting from the steady descent of an impermeable barrier separating initially-quiescent fresh and saline water bodies having density ₀ and ₀+()₀, respectively. A set of parametric laboratory experiments has been carried out (i) to determine the characteristic features of the time-dependent exchange flow over the barrier crest and (ii) to quantify the temporal increase in the thickness and spatial extent of the brackish water reservoir formed behind the barrier by the outflowing, partly-mixed saline water. The results of the laboratory experiments have been compared with the predictions of a theoretical model adapted from the steady, so-called maximal exchange flow case and good qualitative agreement between theory and experiment has been demonstrated. The comparisons indicate that head losses of between 7% and 3% are applicable to the flow over the ridge crest in the early and late stages, respectively, of the barrier descent phase, with these losses being attributed to mixing processes associated with the counterflowing layers of fresh and saline water in the vicinity of the ridge crest. The experimental data show (and the theoretical model predictions confirm) that (i) the dimensionless time of detection t _det(g/H _b)^1/2 of the brackish water pool fed by the dense outflow increases (at a given distance from the barrier) with increasing values of the descent rate parameter g'H _b/(dh _b/dt)² and (ii) the normalised thickness (x,t)/H _b of the pool at a given reference station increases monotonically with increasing values of the modified time (t–t _det)/(H _b/g)^1/2, with the rate of thickening decreasing with increasing values of the descent rate parameter g'H _b(dh _b/dt)². Here, g=(g/₀)()₀ is the modified gravitational acceleration, H _b is the mean depth of the water and dh _b/dt denotes the rate of descent of the barrier height h _b with elapsed time t after the two water bodies are first brought into contact.     

突变理论在环境预测中的应用

以某市七年来环境治理投资状况为序列建立多项式预测模型 ,尽管其拟合精度较高 ,但其预测结果偏离现实情况较大 ,通过突变理论分析知其原因在于有突变因素存在之故     

Volatile Organic Compounds in the Area of Madrid: A Chemometrical Approach

Multivariate techniques have been applied to the set of dataobtained after one year sampling of volatile organic compounds(VOCs), including volatile aldehydes in the area of Madrid inorder to evaluate the possible correspondence among groups ofanalysed compounds, as far as modelling of different emissionsources in relation to location and season. The measurements were carried out at four sites in Madrid, characteristic for urban and suburban areas. Additionally, as reference, a rural area 100 km far from the city was considered. Results of correlation analysis, factor and cluster analysis are presented.Higher correlations were found between variables related withtraffic emissions. Factor analysis results showed two mainsignificant variables related to anthropogenic and biogenicemissions respectively. In relation to cluster analysis, samples were grouped according to sampling site and seasonal variations.