Reynolds number dependence of scalar fluctuations in a high Schmidt number turbulent jet

The scalar rms fluctuations in a turbulent jet were investigated experimentally, using high-resolution, laser-induced fluorescence techniques. The experiments were conducted in a high Schmidt number fluid (water), on the jet centerline, over a jet Reynolds number range of 30003000 or 6500

Stochastic geometric properties of scalar interfaces in turbulent jets

Experiments were conducted in which the behavior of scalar interfaces in turbulent jets was examined, using laser-induced fluorescence (LIF) techniques. The experiments were carried out in a high Schmidt number fluid (water), on the jet centerline, over a jet Reynolds number range of 1000<=Re<=24 000. Both two-dimensional scalar data, c(r,t) at fixed x/d, and one-dimensional scalar data, c(t) at fixed x/d and r/x, were analyzed using standard one- and two-dimensional fractal box-counting algorithms. Careful treatment was given to the handling of noise. Both long and short records as well as off-centerline measurements were also investigated. The important effect of threshold upon the results is discussed. No evidence was found of a constant (power-law) fractal dimension over the range of Reynolds numbers studied. On the other hand, the results are consistent with the computed behavior of a simple stochastic model of interface geometry

Measurements of scalar power spectra in high Schmidt number turbulent jets

We report on an experimental investigation of temporal, scalar power spectra of round, high Schmidt number (Sc ≃ 1.9 × 10^3), momentum-dominated turbulent jets, for jet Reynolds numbers in the range of 1.25 × 10^4 ≤ Re ≤ 7.2 × 10^4. At intermediate scales, we find a spectrum with a slope (logarithmic derivative) that increases in absolute value with Reynolds number, but remains less than 5/3 at the highest Reynolds number in our experiments. At the smallest scales, our spectra exhibit no k^(−1) power-law behaviour, but, rather, seem to be approximated by a log-normal function, over a range of scales exceeding a factor of 40, in some cases

Some consequences of the boundedness of scalar fluctuations

Values of the scalar field c(x,t), if initially bounded, will always be bounded by the limits set by the initial conditions. This observation permits the maximum variance ∼(c′^2) to be computed as a function of the mean value c. It is argued that this maximum should be expected in the limit of infinite Schmidt numbers (zero scalar species diffusivity). This suggests that c′/c on the axis of turbulent jets, for example, may not tend to a constant, i.e., independent of x/d, in the limit of very large Schmidt numbers. It also underscores a difficulty with the k^(−1) scalar spectrum proposed by Batchelor [J. Fluid Mech. 5, 113 (1959)]

The Costs of Human Salmonellosis Attributable to Pork: A Stochastic Farm-to-Fork Analysis

Few farm-to-table analyses of the risk pathways for foodborne illnesses exist, and no such analysis exists for the case of salmonellosis and pork products. This paper presents a Monte Carlo simulation model of the US pork system and the transmission pathways of Salmonella. For the year 2000, we estimate the cost of illness attributable to porkborne Salmonella at $45.7 million, with an estimated 43,505 cases of salmonellosis attributable to pork occurring annually.Food Consumption/Nutrition/Food Safety,

DO ANTIBIOTICS REDUCE PRODUCTION RISK FOR U.S. PORK PRODUCERS?

Production risk from live weight variation of market pigs has become a more important concern in U.S. swine production. Packers are concerned about the variation in carcass size because of the demand for standardized cuts and the use of automation in the slaughter process. Swine producers care about standardized pigs because of revenue implications and possible links to animal health and productivity. Pig size variation can be due to various condition and inputs including antibiotics. However, discussions on risk reduction from antibiotic use have generally not been considered. Our work extends previous studies by systematically examining the aspects of production risk reduction and highlights the potential results of banning antibiotics from a risk perspective. Using data from National Animal Health Monitoring System 2000 survey data and PigCHAMP, we identify the relationship between antibiotic use and production risk by an econometric model. Applying production costs for feeder to market pigs and a price matrix, the uncertainty in profits is evaluated. The impacts of risk on the decision making of swine producers are examined under the framework of expected utility and stochastic dominance analysis. Our results show that production risk from weight variability of market hogs is important in determining profits and utility under a pricing system. Production risk (i.e. weight gain variability) is related to the use of sub-therapeutic antibiotics. Swine producers could decrease production risk and enhance utility by adjusting antibiotic use. These results offer some support for optimal use of sub-therapeutic antibiotics.production risk, antibiotics, swine, utility, stochastic dominance, Livestock Production/Industries, Risk and Uncertainty, Q10, Q12, Q14.,

Measurements of scalar power spectra in high Schmidt number turbulent jets

Single-point, jet-fluid concentration measurements obtained from high Schmidt number (Sc ≃ 1.9 x 10^3) turbulent jets permit an investigation of temporal scalar power spectra, for jet Reynolds numbers in the range of 1.25 ≤ Re x 10^(-4)≤ 7.2. At intermediate scales, we find a spectrum with a logarithmic derivative (slope) that is increasing with Reynolds number, in absolute value, but less than 5/3 at the highest Reynolds number in our experiments. At the smallest scales, our spectra exhibit no k^(-1) power-law behavior, possessing a log-normal region over a range of scales exceeding a factor of 40, in some cases

AN ECONOMETRIC ANALYSIS OF THE ECONOMIC CONTRIBUTION OF SUBTHERAPEUTIC ANTIBIOTIC USE IN PORK PRODUCTION

There is growing concern among public health experts regarding the diminishing efficacy of antimicrobial therapy in human and veterinary medicine, and some have called for a ban on subtherapeutic antibiotic use in pork production. This paper develops an econometric analysis to identify the economic contributions of subtherapeutic antibiotic use in swine production.Livestock Production/Industries,

HECS and HECS-HELP: equity Issues

There have been many changes to the Higher Education Contribution Scheme (HECS) since itsintroduction in 1989. The most significant of these is possibly the reforms announced in the 2003Federal Budget, which allow universities to increase the contributions required of students by up to25%. This paper considers the distribution of deferred HECS liabilities according to thesocioeconomic status of students. An algorithm is presented for converting area-level data to itsindividual-level equivalent. It is found that students of lower socioeconomic status defer a muchlarger proportion of their HECS than students of higher socioeconomic status. The adverse sideeffects of HECS identified in the literature will therefore be more acute for low socioeconomicstatus background students than for their wealthier counterparts