Urbanization and the Environment in Southern Africa: Towards a Managed Framework for the Sustainability of Cities

In sub-Saharan Africa, Southern Africa is the most urbanized region. This dynamic is rapidly transforming the nature of Southern African human settlements which, in turn, has a chain reaction of consequences from negative environmental impact to the need to develop policy for the sustainability of the region's cities. This paper examines the relationship between urbanization trends and environmental change in Southern Africa, and then advocates and discusses priority areas of a managed policy framework for a more constructive approach to responding to the challenge of the sustainability of cities in the region. The paper concentrates on those countries that are members of the Southern African Development Community (SADC).     

Self-ignition of tetrafluoroethylene induced by rapid valve opening in small diameter pipes

This work investigates the ignition of tetrafluoroethylene induced by the adiabatic compression that can arise by activating a high speed valve separating two portions of a pipeline with a high pressure difference. In the tests performed the high pressure zone contained tetrafluoroethylene at pressures between 15 and 30 bar. For the low pressure zone, experiments with nitrogen, air and tetrafluoroethylene were carried out. The pressure range in the low pressure zone was comprised between 0.05 and 1 bar. The pipe diameters analyzed were 15 and 20 mm. For the analyzed geometries, special conditions were required in order to reach reproducible ignitions, namely air at temperatures of at least 105 °C had to be present in the compression pipe. Furthermore, a minimum length of the compression pipe had to be used. The current work describes the experimental setup employed for the tests and discusses the achieved results. Numerical simulations were performed in order to clarify unexpected findings.     

The use of state workers' compensation administrative data to identify injury scenarios and quantify costs of work-related traumatic brain injuries

PROBLEM: Traumatic brain injury (TBI) is a public health problem but little is known about the nature of that problem in the working population. METHOD: The author used a national definition to identify cases in Washington State from workers' compensation (WC) hospital billing data, quantified the cost of WC insurance benefits using actuarial cost estimates, and identified high risk industries using ANSI Z16.2 typology. RESULTS: There were 928 cases of TBI with a lifetime claim cost of $159 million from the Washington State Fund (1994-2001). Sixty percent of injuries resulted in death or disability. The highest risks of TBI are concentrated in 16 industrial insurance risk classes and the highest costs in 19 North American Industry Classification codes. Injury scenarios were identified for nine industrial insurance risk classes. CONCLUSIONS: TBI is a disabling and costly workplace injury in the state of Washington, affecting even teenagers and seniors who are not generally considered to be part of the workforce. Injury typology codes provide useful information for improving workplace safety. IMPACT ON INDUSTRY: This research provides industry with quantitative information regarding the cost of work-related traumatic brain injury and the usefulness of using workers' compensation claims data to reduce the burden of workplace injury.     

The distribution of lianas and their change in abundance in temperate forests over the past 45 years

Lianas (woody vines) are an important and dynamic component of many forests throughout the world, and increases in CO2, mean winter temperature, and forest fragmentation may promote their growth and proliferation in temperate forests. In this study, we used a 45-year data set to test the hypothesis that lianas have increased in abundance and basal area in the interiors of 14 deciduous temperate forests in Wisconsin (USA) since 1959. We also censused woody plants along a gradient from the forest edge to the interior in seven of these forests to test the hypothesis that the abundance of lianas declines significantly with increasing distance from the forest edge. We found that lianas did not increase in abundance within the interiors of temperate forests in Wisconsin over the last 45 years. However, relative and absolute liana abundance decreased sharply with increasing distance from forest edges. Our findings suggest that forest fragmentation, not climate change, may be increasing the abundance of lianas in northern deciduous temperate forests, and that lianas may further increase in abundance if the severity of forest fragmentation intensifies.     

Direct measurement of denitrification activity in a Gulf coast freshwater marsh receiving diverted Mississippi River water

Wetland loss along the Louisiana Gulf coast and excessive nitrate loading into the Gulf of Mexico are interrelated environmental problems. Nitrate removal by soil denitrification activity was studied in a ponded freshwater marsh receiving diverted Mississippi River water for the purpose of reversing or slowing wetland loss. Labeled ¹⁵N-nitrate was applied at 3.8 g N m⁻² into four replicate study plots after removing above ground vegetation. Nitrogen gas (N₂) and nitrous oxide (N₂O) emissions from the plots were determined by isotope ratio mass spectrometry (IRMS). Nitrous oxide emissions were also compared with the results determined by gas chromatograph (GC). Results showed that it took 2 weeks to remove the added nitrate with N₂O emission occurring over a period of 4 d. The apparent denitrification dynamics were assumed to follow the Michaelis–Menten equation. The maximum denitrification rate and K_m value were determined as 12.6 mg N m ⁻² h⁻¹, and 6.5 mg N l⁻¹, respectively. Therefore the maximum capacity for nitrate removal by the marsh soil would be equivalent to 110 g N m⁻² yr⁻¹, with more than 30% of nitrogen gas evolved as N₂O. For typical nitrate concentrations in Mississippi River water of about 1 mg N l⁻¹, nitrate would be removed at a rate of 14.7 g N m⁻² yr⁻¹ with N₂O emission about 1.5%. A denitrification dynamic model showed that the efficiency of nitrate removal would largely depend on the water discharge rate into the ponded wetland. Higher discharge rate will result in less retention time for the water in the marsh where nitrate is denitrified.     

Phytotoxicity of nitroaromatic energetic compounds freshly amended or weathered and aged in sandy loam soil

The toxicities of 2,4,6-trinitrotoluene (TNT), 1,3,5-trinitrobenzene (TNB), 2,4-dinitrotoluene (2,4-DNT), and 2,6-dinitrotoluene (2,6-DNT) to terrestrial plants alfalfa (Medicago sativa L.), Japanese millet (Echinochloa crusgalli L.), and perennial ryegrass (Lolium perenne L.) were determined in Sassafras sandy loam soil using seedling emergence, fresh shoot, and dry mass measurement endpoints. A 13-week weathering and aging of energetic materials in soils, which included wetting and drying cycles, and exposure to sunlight of individual soil treatments, was incorporated into the study design to better reflect the soil exposure conditions in the field than toxicity determinations in freshly amended soils. Definitive toxicity tests showed that dinitrotoluenes were more phytotoxic for all plant species in freshly amended treatments based on EC20 values for dry shoot ranging from 3 to 24mgkg(-1) compared with values for TNB or TNT ranging from 43 to 62mgkg(-1). Weathering and aging of energetic materials (EMs) in soil significantly decreased the toxicity of TNT, TNB or 2,6-DNT to Japanese millet or ryegrass based on seedling emergence, but significantly increased the toxicity of all four EMs to all three plant species based on shoot growth. Exposure of the three plant species to relatively low concentrations of the four compounds initially stimulated plant growth before the onset of inhibition at greater concentrations (hormesis).     

Further validation of artificial neural network-based emissions simulation models for conventional and hybrid electric vehicles

With the advent of hybrid electric vehicles, computer-based vehicle simulation becomes more useful to the engineer and designer trying to optimize the complex combination of control strategy, power plant, drive train, vehicle, and driving conditions. With the desire to incorporate emissions as a design criterion, researchers at West Virginia University have developed artificial neural network (ANN) models for predicting emissions from heavy-duty vehicles. The ANN models were trained on engine and exhaust emissions data collected from transient dynamometer tests of heavy-duty diesel engines then used to predict emissions based on engine speed and torque data from simulated operation of a tractor truck and hybrid electric bus. Simulated vehicle operation was performed with the ADVISOR software package. Predicted emissions (carbon dioxide [CO2] and oxides of nitrogen [NO(x)]) were then compared with actual emissions data collected from chassis dynamometer tests of similar vehicles. This paper expands on previous research to include different driving cycles for the hybrid electric bus and varying weights of the conventional truck. Results showed that different hybrid control strategies had a significant effect on engine behavior (and, thus, emissions) and may affect emissions during different driving cycles. The ANN models underpredicted emissions of CO2 and NO(x) in the case of a class-8 truck but were more accurate as the truck weight increased.     

Determinants of paternity in the garden snail Helix aspersa

Despite the likely importance of post-copulatory sexual selection in simultaneous hermaphrodites, the factors influencing sperm competition in these organisms are generally unknown. We have investigated the effects of dart-shooting, mating order, and several other predictors on the proportion of offspring fathered by penultimate (P_n-1) and ultimate (P_n) sperm donors in multiply mated garden snails, Helix aspersa. While paternity ratios were biased towards the penultimate donor (mean P_n-1=0.61), the magnitude of this advantage was dependent upon which of the two donors successfully darted the recipient. Mean P_n-values increased from 0.17 when the recipient was hit by the penultimate donor to 0.39 when it was hit by the ultimate donor. Furthermore, the effect of the dart was more pronounced in the clutches of smaller recipients. From these results, and observations of live sperm in the storage organs, we propose a novel mechanism to explain the detected pattern of sperm utilization in helicid snails. Electronic supplementary material to this paper can be obtained by using the Springer LINK server located at http://dx.doi.org/10.1007/s00265-002-0519-6.