中加合作农业生态学“双语+精品”课程建设的探索与实践

在国际教育合作背景下,福建农林大学引进的农业生态学(Agroecology)课程与福建省甚至全国高校双语课程相比具有独特的优势。本文回顾了中加合作《农业生态学》双语课程的引进和适应过程,以及其作为福建省"精品课程"的教学体系、风格、方式及其建设成效;最后作者提出从促进国际交流、加强教材建设和教学成果的推广应用等3方面努力把该课程建成国家级"双语示范课程"。     

Uncertainty and Risk in Financial Markets

This paper considers a general equilibrium model in which the distinction between uncertainty and risk is formalized by assuming agents have incomplete preferences over state‐contingent consumption bundles, as in Bewley (1986). Without completeness, individual decision making depends on a set of probability distributions over the state space. A bundle is preferred to another if and only if it has larger expected utility for all probabilities in this set. When preferences are complete this set is a singleton, and the model reduces to standard expected utility. In this setting, we characterize Pareto optima and equilibria, and show that the presence of uncertainty generates robust indeterminacies in equilibrium prices and allocations for any specification of initial endowments. We derive comparative statics results linking the degree of uncertainty with changes in equilibria. Despite the presence of robust indeterminacies, we show that equilibrium prices and allocations vary continuously with underlying fundamentals. Equilibria in a standard risk economy are thus robust to adding small degrees of uncertainty. Finally, we give conditions under which some assets are not traded due to uncertainty aversion.     

Why Has Safety Improved at Rail‐Highway Grade Crossings?

The number of collisions and fatalities at rail-highway intersections in the United States has declined significantly over the past 30 years, despite considerable increases in the volume of rail and highway traffic. This article disaggregates the improvement into its constituent causes. Negative binomial regressions are conducted on a pooled data set for 49 states from 1975 to 2001. The analysis concludes that about two-fifths of the decrease is due to factors such as reduced drunk driving and improved emergency medical response that have improved safety on all parts of the highway network. The installation of gates and/or flashing lights accounts for about a fifth of the reduction. The development in the 1970s and early 1980s of the Operation Lifesaver public education campaign, and the installation of additional lights on locomotives in the mid 1990s, each led to about a seventh of the reduction. Finally, about a tenth is due to closure of crossings resulting from line abandonments or consolidation of little-used crossings.     

The effect of female migration on infant and child survival in Uganda

This article uses data from the 1996 Uganda Demographic and Health Survey to examine whether migration of women improves the survival chances of their children to age five. We expand on prior research by testing not only the hypothesized positive effect of rural-urban migration, but also the effects of other migration stream behaviours on child survival. Results show that up to 10% of children die before age five and within-group differences in mortality exist among urban and rural children depending on their mother's migration status. Only urban-urban migration was significantly related to child survival, compared to rural non-migrants, after controlling for other factors, although other streams of migration (rural-urban, urban-rural, rural-rural) were positively related to child survival. Generally, migration explains a small component of the variance in child survival. Several other factors, including parents' education, household size, household headship, mother's age at birth, duration of breastfeeding, and place of delivery have a significant predictive power on child survival.     

Priority: Home! A true priority? An analysis of the Federal Plan to Break the Cycle of Homelessness

Homelessness pervades every fabric of American society: it has plagued individuals and families, young and old, males and females. This paper analyzes and discusses the feasibility of a current proposal, Priority: Home? The Federal Plan to Break the Cycle of Homelessness, and the intended effects of its policies pertaining to the homeless. Specifically, the plan outlines the need for a continuum of care, a concept which promotes three stages to attain self-sufficiency: emergency shelter, transitional housing, and permanent housing. Providing support services and follow-up care are contingent on the success of the continuum. The plan therefore describes a comprehensive solution to address homelessness and requires that all levels of government participate in the process.     

On the use and evaluation of prospective scan methods for health-related surveillance

Summary.  We review some prospective scan-based methods that are used in health-related applications to detect increased rates of mortality or morbidity and to detect bioterrorism or active clusters of disease. We relate these methods to the use of the moving average chart in industrial applications. Issues that are related to the performance evaluation of spatiotemporal scan-based methods are discussed. In particular we clarify the definition of a recurrence interval and demonstrate that this measure does not reflect some important aspects of the statistical performance of scan-based, and other, surveillance methods. Some research needs in this area are given.     

Minimum Sample Size Considerations for Two-Group Linear and Quadratic Discriminant Analysis with Rare Populations

Linear discriminant analysis and quadratic discriminant analysis are used to predict group membership. Rare populations present situations in which group sizes differ drastically. This article examined k = 2 and k = 4 predictor variables for groups with different levels of rarity and different levels of sensitivity and specificity. Sample size recommendations were generated for both minimum and maximum group overlap using the leave-one-out (L-O-O) method of estimation. Minimum sample size recommendations are provided in tables for immediate implementation by applied researchers.     

Patterns in macroinvertebrate taxonomic richness and community assembly among urban wetlands in Cape Town,South Africa: implications for wetland management

Urbanization has significantly increased globally during the last century and has far-reaching consequences for biodiversity and their associated habitats, particularly wetland ecosystems. Previous studies have focused primarily on wetlands in non-urban areas, and urban wetland biodiversity patterns are currently not well understood, particularly across Africa. Here, we investigate two highly transformed urban wetlands in Cape Town, South Africa, and determine the relative importance and influence of local environmental variables as drivers of macroinvertebrate richness and community structuring. We also determine the influence of local environmental variables for patterns of species turnover and nestedness within and among these wetlands, and provide management recommendations based on our findings. We found that few macroinvertebrate species were associated with these wetlands, yet community variation was driven by a combination of local environmental variables. Our results also indicate that the turnover component of beta diversity, rather than nestedness, was responsible for most of the variation in the overall macroinvertebrate community. We identified two major problems regarding the current ecological state of the investigated wetlands. Firstly, high nutrient loads originating from the surrounding land uses which reduced wetland biodiversity, and secondly, the transformation of these wetlands from seasonal to perennial water bodies. We recommend local and regional scale approaches to limit urban waste from entering these systems, and management of water levels simulating natural Mediterranean-type climate dynamics more closely are required to ensure that the maximum possible diversity can be supported in these wetlands.

     

Family Instability and Exposure to Violence in the Early Life Course

Family instability has been linked with a host of outcomes across the early life course. This study extends this literature by connecting instability with violence in the community by examining the associations among family structure, family structure change, and secondary exposure to violence during adolescence across diverse segments of the population. Using longitudinal data from the Project on Human Development in Chicago Neighborhoods study, we found that living with a single parent and experiencing family structure changes were associated with secondary exposure to violence. Multiple group models suggest that partner change translated into more exposure for boys than girls. Findings also suggest that family instability may lead to more secondary exposure to violence for African American youth.