A Bayesian approach to model dispersal for decision support

In agricultural and environmental sciences dispersal models are often used for risk assessment to predict the risk associated with a given configuration and also to test scenarios that are likely to minimise those risks. Like any biological process, dispersal is subject to biological, climatic and environmental variability and its prediction relies on models and parameter values which can only approximate the real processes. In this paper, we present a Bayesian method to model dispersal using spatial configuration and climatic data (distances between emitters and receptors; main wind direction) while accounting for uncertainty, with an application to the prediction of adventitious presence rate of genetically modified maize (GM) in a non-GM field. This method includes the design of candidate models, their calibration, selection and evaluation on an independent dataset. A group of models was identified that is sufficiently robust to be used for prediction purpose. The group of models allows to include local information and it reflects reliably enough the observed variability in the data so that probabilistic model predictions can be performed and used to quantify risk under different scenarios or derive optimal sampling schemes.     

Effects of larval crowding and nutrient limitation on male phenotype,reproductive investment and strategy in Ephestia kuehniella Zeller (Insecta: Lepidoptera)

Food shortage experienced by juvenile insects affects adult morphology and life-history traits. Developmental plasticity and trade-off between ecological and sexual traits helps maximise individual fitness. Ephestia kuehniella were reared at different larval densities to investigate phenotypic shifts in adult males. Variation in ecological traits (sizes of forewing, head and thorax and adult longevity) and sexual traits (valva and aedeagus, sperm number, mating frequency) were compared. Males that emerged from highest density population (800) had lower body mass and small forewings, head and thorax, suggesting that they could not completely compensate for food shortage. The allometric relationship between body mass and forewing length also changed, and these males had relatively longer wings. This arrangement may enhance dispersal and assist in mate-searching at higher densities. Males from all larval densities achieved similar mating frequency but those from higher density produced fewer eupyrene sperm and had shorter adult lifespan. By mating more frequently and maintaining apyrene sperm production, males increase their reproductive success at sperm competition observed at higher densities. Food stress associated with high density populations did not affect valva and aedeagus size indicating that these traits may be insensitive to external environmental changes because they incur fitness costs to males.     

Grasshoppers (Orthoptera,Saltatoria) on alpine and dealpine riverbanks and their use as indicators for natural floodplain dynamics

Gravel banks with sparse vegetation are typical habitats of braided alpine and dealpine floodplains. They are not only habitats for semiaquatic or hygrophilous organisms, but include also xerophilous elements: 17 species of grasshoppers were recorded in the floodplain of the Upper Isar (Bavaria, FRG). In the alpine region, two species (Bryodema tuberculata, Chorthippus pullus) occur only in floodplains, colonizing young gravel banks with sparse vegetation. Population dynamics and habitat selection of Bryodema tuberculata, studied on the Upper Isar for several years, are characterized by small scale movements of marked individuals between neighbouring gravel banks and fluctuations of the abundance on different sections of the gravel banks. Furthermore, the periodic desiccation of small watercourses is important for the dispersal of the females by walking. Historically widespread, today its distribution corresponds to the few remaining inundation areas. The main causes of decrease and extinction in most localities are man-made changes in floodplain dynamics. The building of retention reservoirs and the diverting of streams for hydropower influenced succession in the downstream floodplains. Most of the gravel banks with sparse vegetation changed into willow thickets or pine forests. All remaining inundation areas should be protected. Bryodema tuberculata is a good indicator for the balance between progressing succession and the reorganization of gravel banks by floods.     

Forced Relocation vs. Voluntary Mobility: The Effects of Dispersal Programmes on Households

The deconcentration of poverty in the US has involved both voluntary mobility programmes for low-income households and involuntary relocation of families through government action. This paper examines the effects on families of these two different strategies. Using data on over 600 families in the Twin Cities region of Minneapolis/Saint Paul, the study reveals only sporadic support for the hypothesis that voluntary or involuntary participants in the deconcentration effort will report improvements in their living conditions, or report better conditions than a control group of public housing and Section 8 residents. Several possible explanations for the lack of programme effects are offered.     

Significant population structure in Australian Cryptolestes ferrugineus and interpreting the potential spread of phosphine resistance

An analysis of the population genetics of Cryptolestes ferrugineus, across all major regions in Australia where grain is grown and stored in bulk, provides an initial step in investigating the movement of these insects and implications for the spread of phosphine resistance. Microsatellite data revealed two levels of genetic structure. Across Australia, two clusters were detected, one in eastern Australia (Queensland, New South Wales, Victoria and Tasmania) and Western Australia (Cluster 1) and one in South Australia (Cluster 2). Intermediate between them, in eastern South Australia, are a couple of populations that are equally admixed for the two clusters. Populations in Western Australia and western SA belong to different clusters suggesting that the extensive and arid Nullarbor Plain restricts the natural dispersal of these beetles. Isolation-by-distance and the detection of clustering among local populations suggests there is considerable gene flow at a local scale in C. ferrugineus, and we infer this is by flight. Limited natural gene flow between eastern and western Australia might, in part, explain why extremely high resistance has not been detected in Western Australia.     

基于RS纠删码的信息分散算法

利用基于RS纠删码的信息分散算法可构建高顽存的分布式存储系统。RS纠删码的编/译码速率是衡量其可用性的一个重要指标。对RS纠删码的纠删原理进行了理论分析,讨论了编/译码运算所在的伽罗瓦域,基于伽罗瓦域算术运算的特征设计了双表法以提高编/译码速率。最后对该信息分散算法的效率进行了理论分析和实验测试。测试结果表明,该信息分散算法可提供18Mbps的编/译码速率,基于该测试结果分析了基于RS纠删码的信息分散算法的适用环境,指出信息分散算法未来的研究方向。     

中板矫直机变辊距技术的研究

通过对某钢厂的9辊中板矫直机进行变辊距技术的优化研究,总矫直力和各辊矫直力的分布较原定辊距方式有较大幅度改善.这种研究方法对一般矫直机的设计和改造也有一定的指导意义.     

中国当代体育场建筑设计研究

本文通过对体育场功能分区及其特性、赛场模式的选择、看台区的设计原则与特点、观众席的视线设计、体育场的疏散设计、比赛设施的多功能与灵活性等六个方面的研究和分析，对中国现有体育场建筑的设计模式进行初步探索与总结，力求为我国体育场设计的专项领域提供一个可供参照的坐标系。     

固体碳源在水溶液中的分散实验研究

在SiC陶瓷固相烧结过程中,碳源的分散性非常重要。其对陶瓷的微观组织结构和力学性能有较大的影响。本文重点通过沉降实验,研究对于同一分散介质,三种分散剂（无分散剂;Darven．C;焦磷酸钠）作用下,三种碳源（石油焦、炭黑、石墨）的不同分散结果,优选出分散最好的碳源以及分散性最佳的分散剂。实验结果表明：分散剂的加入对SiC浆料分散效果有很大影响;不同的碳源pH值有微小差别;三种碳源中碳黑分散最好;分散剂中焦磷酸钠分散性最佳。     

Distribution of aquatic macrophytes in contrasting river systems: a critique of compositional-based assessment of water quality

A brief summary of the historical developments relating to plant distribution and aquatic macrophyte-nutrient indices provided a means of assessing the general context and validity of previous assumptions. This has particular current relevance because of the prominent use of bioindicators for defining nutrient enrichment. A survey of 161 sites distributed across two broadly contrasting groups of rivers (circum-neutral versus alkaline) recorded 110 species of aquatic macrophytes and these have been statistically analyzed to (i) rank and separate the individual effects of local environmental conditions and spatial isolation on species distribution in the two contrasting groups of sites; (ii) calculate a macrophyte index based on plant cover and species indicator values (Mean Trophic Rank, MTR); and finally (iii) investigate the implications for biomonitoring. Chemical, physical and hydrological site attributes together with spatial isolation, each explained a significant and at least partially independent influence over plant species distribution. It was extremely difficult, however, to separate the single effects of different site attributes on plant distribution. While some plant species are more restricted to certain environmental conditions, many appeared indifferent to the range of those being tested. The role played by nutrients (nitrogen (N) and phosphorus (P)) were either mostly indistinguishable from other site attributes (e.g., nitrate from conductivity) or subordinate (e.g., soluble reactive phosphorus, ammonium). It is therefore very unlikely that macrophyte species composition could provide a reliable bioindicator of the surrounding nutrient (N, P) status. The calculation of the plant index illustrated this unreliability by showing that strong correlations existed with many environmental variables, not just inorganic N and P.