Modelling and assessment of South African elephant Loxodonta africana population persistence

The use of a quantitative population growth model to investigate the persistence of South African elephant populations is explored. The model provides quantitative assessments of population persistence and confidence intervals for estimated parameters based purely on population size estimates. The analysis supports the view that most of the larger populations in the region are secure. This view is further supported by a lack of density dependent effects in most of the recovering populations and the high population rates of increase observed. This predominantly positive prognosis is in contrast with that emerging from most of the rest of the African continent where the populations are under greater threat because of habitat restriction and direct human conflict. This preliminary assessment of elephant population persistence suggests that “viable” populations may lie between 400 and 6000 individuals. Although not inconsistent with information-greedy genetic and demographic models, the relationship between population growth versus genetic and demographic models should be further investigated. The implementation of a metapopulation management strategy towards these smaller populations is advocated. In addition, as all of the populations included in this analysis have been afforded some degree of protection since the 1920s, continued protection would be a prerequisite for their continued survival.     

Global sensitivity analysis of a process-based model for ammonia emissions from manure storage and treatment structures

The development of process-based models to estimate ammonia emissions from animal feeding operations (AFOSs) is sought to replace costly and time-consuming direct measurements. Critical to process-based model development is conducting sensitivity analysis to determine the input parameters and their interactions that contribute most to the variance of the model output. Global and relative sensitivity analyses were applied to a process-based model for predicting ammonia emissions from the surface of anaerobic lagoons for treating and storing manure. The objectives were to compare global sensitivity analysis (GSA) to relative (local) sensitivity analysis (RSA) on a process-based model for ammonia emissions. Based on the first-order coefficient, both GSA and RSA showed the model input parameters in order of importance in process model for ammonia emissions from lagoon surfaces were: (i) pH, (ii) lagoon liquid temperature, (iii) wind speed above the lagoon surface, and (iv) the concentration of ammoniacal nitrogen in the lagoon. The GSA revealed that interactions between model parameters accounted for over two-thirds of the model variance, a result that cannot be achieved using traditional RSA. Also, the GSA showed that parameter interactions involving liquid pH had more impact on the model output variance than the single parameters: (i) temperature, (ii) wind speed, or (iii) total ammoniacal nitrogen. This study demonstrates that GSA provides a more complete analysis of model input parameters and their interactions on the model output compared to RSA. A comprehensive tutorial regarding the application of GSA to a process model is presented.     

Mode choice model for vulnerable motorcyclists in Malaysia

OBJECTIVE: In developing countries, motorcycle use has grown in popularity in the past decades. Commensurate with this growth is the increase in death and casualties among motorcyclists in these countries. One of the strategic programs to minimize this problem is to reduce motorcyclists exposure by shifting them into safer modes of transport. This study aims to explore the differences in the characteristics of bus and motorcycle users. It identifies the factors contributing to their choice of transport mode and estimates the probability that motorcyclists might change their travel mode to a safer alternative; namely, bus travel. METHODS: In this article, a survey of 535 motorcycle and bus users was conducted in seven districts of Selangor state, Malaysia. A binary logit model was developed for the two alternative modes, bus and motorcycle. RESULTS: It was found that travel time, travel cost, gender, age, and income level are significant in influencing motorcyclists' mode choice behavior. The probability of motorcycle riders shifting to public transport was also examined based on a scenario of a reduction in bus travel time and travel cost. CONCLUSIONS: Reduction of total travel time for the bus mode emerges as the most important element in a program aimed at attracting motorcyclists towards public transport and away from the motorcycle mode.     

Longitudinal examination of underage drinking and subsequent drinking and risky driving

INTRODUCTION: Alcohol use, alcohol misuse, and risky driving from adolescence into young adulthood were compared by drinking onset age. METHODS: Surveys were administered in Grades 5/6, 6/7, 7/8, 10, 12, and at approximately age 23. Participants were placed into Drinking Onset groups based on self-reported alcohol use frequency on the adolescent surveys. Driving records were examined in three age periods: under 21, 21-25, and 26+. RESULTS: The earliest drinking initiators reported higher alcohol use and misuse on each survey, and were more likely to have risky driving offenses before age 21 and to have alcohol driving offenses in all three age periods. DISCUSSION: The earliest drinking initiators engaged in risky drinking behavior and risky driving behavior that was consistently higher than those with later drinking initiation, beginning in adolescence and persisting well into young adulthood.     

SAFEST TO TRAVEL BY BICYCLE,CAR, OR BIG TRUCK?

This study compares highway crash incidence, injuries, and costs by vehicle type. Annual crash and injury incidence were estimated using Crashworthiness Data System (1988-1991), National Automotive Sampling System (1982-1986), General Estimates System (1992-1993), and Fatal Analysis Reporting System (1993) data. Costs were computed based on restraint use, body region, and threat-to-life severity of the injury. Costs were then allocated between vehicle types using three different methods in order to answer comparative safety questions. Motor vehicle and bicycle crash costs total $389 billion annually; 75% resulting from passenger vehicles. Motorcycles and bicycles have the highest costs per 1000 vehicle and passenger miles; costs per victim are highest for pedestrians, bicyclists, and motorcyclists. Costs per vehicle mile for heavy trucks and passenger cars are comparable but exceed costs for light trucks. Passenger vehicle occupants are safest if a crash occurs. Light truck, other single truck, and bus occupants have the lowest cost per passenger mile, but higher costs than air and rail travelers. Motorcyclists face the greatest risks. Combination trucks may not impose an excess risk to other drivers, but their drivers face large risks.     

Review: The Dynamics of Near Vertex Head Impact and its Role in Injury Prevention and the Complex Clinical Presentation of Basicranial and Cervical Spine Injury

The clinical presentation of cervical and basilar skull fractures following bead impact is often complex, particularly when multiple noncontiguous fractures are present. Based on the results of 22 human cadaver head-neck impact experiments, a biomechanical framework of spinal injury is developed in which these complex cases may be better understood. This includes the significance of head rebound, head and neck decoupling, cervical spine buckling, cervical injury mechanisms, basilar skull fractures, and cervical spine tolerance. These data also demonstrate that compliant pads significantly increase the risk for spinal injury though they also significantly reduce peak head force and the head injury criteria (p < 0.04). On the basis of these observations, we hypothesize that impact injury should be modeled as the dynamic response of two large masses, coupled by a segmented curved beam-column composed of seven small masses with interposed nonlinear viscoelastic flexibility elements.     

Investigation of Blended Fibre Filtering Materials

Five variants of mixtures of different synthetic fibres at different area ratios were manufactured into needled nonwovens intended to be used as a filtering material for respiratory protection. Two variants were produced according to an earlier patent, and the contents of the other three was completely new. Samples of the nonwovens were tested for sodium chloride particles penetration and for breathing resistance. The results showed that one variant of a nonwoven, designated PP/PPFM, had very valuable filtering properties and that those properties were stable in time.