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Rapid losses and degradation of natural habitats in the tropics are driving catastrophic declines and extinctions of native biotas, including angiosperms. Determining the ecological and life-history correlates of extinction proneness in tropical plant species may help reveal the mechanisms underlying their responses to habitat disturbance, and assist in the pre-emptive identification of species at risk from extinction. We determined the predictors of extinction proneness in 1884 locally extinct (n = 454) and extant (n = 1430) terrestrial angiosperms (belonging to 43 orders, 133 families, and 689 genera) in the tropical island nation of Singapore (699.4 km2), which has lost 99.6% of its primary lowland evergreen rainforest since 1819. A wide variety of traits such as geographical distribution, pollination system, sexual system, habit, habitat, height, fruit/seed dispersal mechanism, and capacity for vegetative re-sprouting were used in the analysis. Despite controlling for phylogeny (as approximated by family level classification), we found that only a small percentage of the variation in the extinction probability could be explained by these factors. Epiphytic, monoecious, and hermaphroditic species and those restricted to inland forests have higher probabilities of extinction. Species dependent on mammal pollinators also probably have higher extinction probabilities. More comparative studies that use species traits to identify extinction-prone plant species are needed to guide the enormous, but essential task of identifying species most in need of conservation action.

Gas-mixing rates are inferred at interior locations of a minimally cluttered 5-cubic meters chamber from temperature measurements during pressurization from 1 to 2 atmospheres (101.3 to 202.6 kPa) with an inert pressurant gas, a proposed method of fire suppression. Analysis for this inference is presented and experimental data are reduced accordingly. In addition, the data support a scale modeling theory already reported. These findings show that, for injection times of 10 to 30 seconds, good mixing is experienced in 1.5 injection times in this minimally cluttered space. (Author)

Further smoke production measurements are reported. Smoke production per unit mass is deduced on the basis of exhaust stream CO2 concentration data. A matrix of fire suppression tests with water spray and CO2 has been carried out in the 6x6x6 ft fire enclosure and in a 2x2x2 ft scale model enclosure. A simple correlation indicative of a concise scaling rule was not expected and, in fact, did not result. But the data do constitute a basis for evolution of an empirically adjusted rational model whose intended application is extension of small scale or otherwise inexpensive test data to larger scale or relatively expensive situations.

Means for analytical prediction of the dispersion field of toxic or combustible vapor vented from a tanker are critically evaluated. Particular emphasis is given the conservative delineation of the flammable surface separating spatial domains outside of which dangerous combustion is unlikely and inside of which it is (and an analogous toxic surface) in the light of normal available data and the uncertainties therein. Approximate analyses covering buoyancy and jet momentum effects are included. The problem of assignment of appropriate flammability limits in a turbulent and inhomogeneous mixture is reviewed. Experimental and analytical means of dealing with flow past obstacles and other geometrically complex phenomena are evaluated. The effects of helicopter downwash on vapor dispersion is also briefly analyzed. Finally, the procedure for analysis of vapor dispersion within tanks is outlined.

An approximate method for scale-modeling inert pressurant distribution in geometrically similar enclosures is applied with length scale factors of 3.84, 6, and 23 (prototype to model) for turbulent flow conditions. Modeling correlations are best in spaces with minimal clutter (no obstructions to flow). With considerable clutter, however, correlations were considered acceptable and indicated good mixing within less than an additional injection time.

This report describes a two-year investigation of smoke and toxic gas production in enclosed fires, particularly as applied to shipboard conditions. Quantification of smoke and toxic gas production, as a function of enclosure parameters such as fuelbed length scale and ventilation magnitude and geometry, are emphasized. A correlation of obscuration, as indicated by smoke opacity, with the instantaneous exhaust stream equivalence ratio was attempted. The results suggest a significant smoke production dependence on enclosure parameters. An analogous carbon monoxide production dependence is observed. Other observations involve smoke particle size and enclosure mass throughput. Upon ignition mass throughput usually decreases relative to non-burning conditions; however, in some cases of restricted ventilation settings, increases are observed. (Modified author abstract)

The large fires which follow nuclear detonations over a city present an important civil defense problem. The high temperature, high winds, high thermal radiation flux, and high noxious gas concentrations at street level present an adverse environment for the escape of people, for fighting fire, and for the operation of shelters. It is essential that civil defense planning be based on as reliable a knowledge of this environment as possible. Since the local conditions will be influenced by the entire mass fire, it is necessary to determine the characteristics of mass fires. The purpose of this research was to find out if the air velocities and temperatures that exist in the gross flow field above a mass fire could be determined from measurements made on a small scale laboratory-sized model of the mass fire, using electrical heating elements to provide the heat input. (Author)