Monte Carlo modeling of radiative transfer in a turbulent sooty flame

The calculation of radiative transfer within a sooty turbulent ethylene-air diffusion jet flame has been carried out by using a Monte Carlo method and an accurate CK model for the gases. The influence of the turbulence-radiation interaction (TRI) has been studied. In the TRI modeling, the radiative properties of the assumed homogeneous turbulent structures are randomly obtained from a multidimensional probability density function (PDF) of the reaction progress variable, of the mixture ratio and of the soot volume fraction. This joint PDF is obtained from an Eulerian-Lagrangian turbulent combustion model and the sizes of the turbulent structures are directly derived from a k-? model. In the considered flame, the TRI effect is an increase of the radiative heat loss by about 30%. The radiative heat loss becomes almost equal to one-third of the chemical heat release. Soot particles play the most important role in the global radiative heat loss but the influence of gaseous species like CO₂ and H₂O can be important in the local energy balance.     

Book reviews

HEALTH HAZARDS OF THE HUMAN ENVIRONMENT, World Health Organization, Geneva, 1972, 387 pp. (£4.40)

ENVIRONMENT AND CANCER: A collection of papers presented at the 24th Annual Symposium on Fundamental Cancer Research, 1971, Williams and Wilkins, 1972.

MANAGING THE ENVIRONMENT: AN ECONOMIC PRIMER, by W. Ramsay and C. Anderson, London, Macmillan, 1972. xvi + 302pp. £3.95.

ECONOMIC THINKING AND POLLUTION PROBLEMS, edited by D. L. Auld, University of Toronto Press, 1972, viii + 184 pp.

POLLUTANT REMOVAL HANDBOOK, by Marshall Sittig, Park Ridge, New Jersey and London, Noyes Data Corporation, 1973, 527 pp.

OUR ECOLOGICAL CRISIS: ITS BIOLOGICAL, ECONOMIC AND POLITICAL DIMENSIONS, by G. J. C. Smith, H. J. Steck and G. Surette, New York and London, Macmillan, 1974, 198 pp.

THE HUMAN CONSEQUENCES OF URBANISATION, Divergent Paths in the Urban Experience of the Twentieth Century, Brian J. L. Berry, Paperback, Macmillan, 1973.     

The work‐life experiences of office and site‐based employees in the Australian construction industry

A survey was conducted among employees of a large Australian construction firm. Comparisons were made between employees who differed by gender and work location. Male employees in site‐based roles reported significantly higher levels of work to family conflict and emotional exhaustion than male employees who worked in the regional or head office. Site‐based male employees were also less satisfied with their pay than male respondents who worked in the regional of head office. Few significant differences were found between women who worked in different locations. Neither were significant differences between men and women who worked in the same location reported. The results are explained in terms of women's tendency to work in administrative, secretarial or support services roles, which typically demand fewer hours. The paper concludes that the experiences of site‐based construction employees, particularly men, warrant further attention to explore the sources of work‐life imbalance and burnout.     

Valuing a price cap contract for material procurement as a real option

This paper uses real option methodology to compare the cost of a long‐term contract with a price cap to that of spot purchases in construction material procurement. In construction, material procurements are usually short‐term, project‐based and subject to high price volatility. These characteristics and the competitive nature of the industry lower the profit margin of contractors. We have observed that contractors purchase a stable amount of commodity materials such as concrete, structural steel and lumber year after year. For contractors, the price cap reduces the price volatility of materials without their being obliged to purchase a certain quantity; for suppliers, the price‐cap contracts give them steady demand and a bigger market share. We evaluate this price‐cap contract as a real option and find the contractor's optimal ordering policy. When materials are not frequently traded, we model price processes by using related market information and then evaluate the idiosyncratic uncertainties in a risk‐neutral setting. Our methodology does not require market completeness and incorporates some of the results of the latest research in finance such as correlation pricing, option pricing and zero level pricing, as well as Monte Carlo simulation.     

Effects of progressive anoxia on the solubility of technetium in sediments

Technetium is a significant radioactive contaminant from nuclear fuel cycle operations. It is highly mobile in its oxic form (as Tc(VII)O4-) but is scavenged to sediments in its reduced forms (predominantly Tc(IV)). Here we examine the behavior of Tc at low concentrations and as microbial anoxia develops in sediment microcosms. A cascade of stable-element terminal-electron-accepting processes developed in microcosms due to indigenous microbial activity. TcO4- removal from solution occurred during active microbial Fe(III) reduction, which generated Fe(II) in the sediments and was complete before sulfate reduction began. Microbial community analysis revealed a similar and complex microbial population at all three sample sites. At the intermediate salinity site, PauII, a broad range of NO3-, Mn(IV), Fe(III), and SO4(2-) reducers were present in sediments including microbes with the potential to reduce Fe(III) to Fe(II), although no differences in the microbial population were discerned as anoxia developed. When sterilized sediments were incubated with pure cultures of NO3(-)-, Fe(III)-, and sulfate-reducing bacteria, TcO4- removal occurred during active Fe(III) reduction. X-ray absorption spectroscopy confirmed that TcO4- removal was due to reduction to hydrous Tc(IV)O2 in Fe(III)- and sulfate-reducing estuarine sediments.     

Derivation by infrared spectroscopy with multivariate analysis of bimodal contaminant-induced dose-response effects in MCF-7 cells

Toxic responses to contaminants following exposure concentrations typically used in laboratory tests may not reflect how biological systems respond to lower environmental levels from which hormetic effect mechanisms have been suggested. We investigated the pattern of dose-response in mammalian cells to various environmental contaminants using a range of concentrations that span those that are environmentally relevant (10(-12)M to 10(-3)M). MCF-7 cell cultures were treated for 24 h with benzo[a]pyrene (B[a]P), lindane (γ-hexachlorocyclohexane), or polybrominated diphenyl ethers (PBDEs) congeners (47, 153, 183, and 209), then fixed in ethanol and interrogated using attenuated total reflection Fourier-transform infrared (ATR-FTIR) spectroscopy. Mode of action was further studied by examining if test agents stimulated cell growth or altered CYP1A1 expression. Bimodal dose response curves were observed when MCF-7 cells were treated with PBDEs or lindane. The first peak distribution was associated with lower doses (10(-12)M to 10(-9)M), while the second occurred only after MCF-7 cells were exposed to concentrations >10(-9)M. Cellular alterations associated with low-dose PBDEs were mainly due to lipid and secondary protein structural changes, whereas lindane induced DNA/RNA effects as well. In contrast, DNA-reactive B[a]P gave rise to a monotonic linear dose-response relationship and induced mainly DNA/RNA cellular changes. This study shows that environmentally realistic exposures to chemical contaminants can induce nonmonotonic dose-responses in cellular systems.