Modeling accident occurrence at signalized tee intersections with special emphasis on excess zeros

In implementing effective remedial treatments at hazardous intersections, it often is necessary to identify the geometric and traffic factors that lead to accident occurrence. However, one particular problem frequently encountered in accident studies is how to distinguish virtually safe intersections with little likelihood of accident occurrence from those that have happened to have no accident due to the random process. To deal with this problem, the "excess" records of zero accident, the zero-inflated negative binomial was used to assign the probability to the accident outcome. Accident data at 104 signalized tee intersections in Singapore over a period of 9 years were employed for model development. The model indicates that uncontrolled left-turn slip road, permissive right-turn phase, existence of a horizontal curve, short sight distances, large number of signal phases, total approach volume, and left-turn volume may increase accident occurrence. On the other hand, right-turn channelization, acceleration section on the left-turn lane, median railings, and more than 5% approach gradient may reduce accident occurrence. Moreover, there is a trend of reducing accidents over the years.     

The life table and competing risks

The concept of the life table originated in longevity studies of man, where it was always presented as a subject peculiar to public health, demography, and actuarial science. As a result, its development has not received sufficient attention in the field of statistics. Actually, the problems of mortality studies are similar to those of reliability theory and life testing, and they may be described in terms familiar to the statistically oriented mind. From a statistical point of view, human life is a random experiment and its outcome, survival or death, ss subject to chance. The life table systematically records the outcomes of many such experiments for a large number of individuals over a period of time. Thus, the quantities in the table are random variables subject to established statistical analysis. The purpose of this presentation is to discuss the life table from a statistical viewpoint.     

Environmental management in Singapore

From modest beginnings, Singapore rapidly developed its industrial base which today comprises high technology and high value added industries. Economic growth was accompanied by a comprehensive housing and urban development programme.The formation of the Ministry of the Environment and the Anti-Pollution Unit in the early seventies marked Singapore's commitment to protect the environment in the face of rapid developments.Together with the rapid industrialisation, housing and urban development programme, Singapore also implemented a programme to prevent pollution as well as to control pollution from those sources which cannot be prevented.The success of these programmes is evident today and we have an environment that compares well with that of any nation in the world.Plenary speaker.     

Feedbacks in Human–Landscape Systems

This article identifies key questions and challenges for geomorphologists in investigating coupled feedbacks in human–landscape systems. While feedbacks occur in the absence of human influences, they are also altered by human activity. Feedbacks are a key element to understanding human-influenced geomorphic systems in ways that extend our traditional approach of considering humans as unidirectional drivers of change. Feedbacks have been increasingly identified in Earth-environmental systems, with studies of coupled human–natural systems emphasizing ecological phenomena in producing emerging concepts for social–ecological systems. Enormous gaps or uncertainties in knowledge remain with respect to understanding impact-feedback loops within geomorphic systems with significant human alterations, where the impacted geomorphic systems in turn affect humans. Geomorphology should play an important role in public policy by identifying the many diffuse and subtle feedbacks of both local- and global-scale processes. This role is urgent, while time may still be available to mitigate the impacts that limit the sustainability of human societies. Challenges for geomorphology include identification of the often weak feedbacks that occur over varied time and space scales ranging from geologic time to single isolated events and very short time periods, the lack of available data linking impact with response, the identification of multiple thresholds that trigger feedback mechanisms, the varied tools and metrics needed to represent both physical and human processes, and the need to collaborate with social scientists with expertise in the human causes of geomorphic change, as well as the human responses to such change.     

Sonographic features of ileal duplication cyst at 12 weeks

Enteric duplication cyst is a congenital abnormality that is believed to arise from abnormal recanalization of the bowel during embryogenesis. Previous reports suggest that the condition may be suspected prenatally by sonographic demonstration of an intra-abdominal cystic mass in the second and third trimesters. We present the sonographic features of a fetus with ileal duplication cyst at 12 weeks of gestation, which show that the condition may present in the first trimester of pregnancy. Copyright © 2002 John Wiley & Sons, Ltd.     

Morphologically plastic responses to shading in the zoanthids Zoanthus sansibaricus and Palythoa tuberculosa

Zoanthids of the order Zoantharia (Anthozoa: Hexacorallia) exhibit high intraspecific morphological variability, but whether this is due to polymorphism, phenotypic plasticity or a combination of both remains unknown. To address this knowledge gap, in November 2010, eight colonies each of Zoanthus sansibaricus and Palythoa tuberculosa were sampled from three reefs off the south of mainland Singapore and transplanted to a shallow experimental site. The colonies were then distributed under two types of treatment frames: control and shaded. After 87 days, morphometric characters were extracted from macro-images. Reaction norms, principal components analysis, analysis of variance and canonical discriminant analysis all demonstrated light-induced changes in morphology. Patterns of plastic changes were similar for both species: shaded colonies had larger polyps as compared to control colonies. The presence of plastic responses in zoanthids may facilitate their colonization of a broad range of habitats as well as help them to withstand temporal changes in their environment.