A Study of the Removal of Pesticides From Water

The purpose of this study was to investigate some of the properties of pesticides as they exist in water, and to determine the effectiveness of several water treatment processes in the removal of pesticides from water. Among the pesticides investigated were malathion, DDT, aldrin, dieldrin, captan, benzene hexachloride (BHC), 2,4-D, and 2,4,5-T. The water treatment processes included aeration, chemical coagulation, adsorption on activated carbons and clays, and foam separation. The removal of pesticides from water by aeration was found to be significant. Dieldrin was removed almost 100 percent, while aldrin, DDT, and BHC were removed to a lesser extent. 2, 4, 5-T and cap tan showed no loss through aeration. Chemical coagulation alone was found to be ineffective in the removal of pesticides from water. Several coagulant aids were investigated but all proved ineffective with the possible exception of one which increased the apparent removal slightly. Of the processes investigated adsorption with activated carbon was determined to be the most effective in removing pesticides from water. The removals obtained were -- malathion near 100 percent; 2 ,4-D, 90 percent; DDT, 95 percent; aldrin, near 100 percent; dieldrin, 90 percent. Studies on the removal of aldrin and dieldrin from water by the use of surface active agents to produce a foam demonstrated that this process might be of value as a treatment method, with removals greater than 90 percent being achieved in some cases

Least squares approximations of measures via geometric condition numbers

For a probability measure on a real separable Hilbert space, we are interested in "volume-based" approximations of the d-dimensional least squares error of it, i.e., least squares error with respect to a best fit d-dimensional affine subspace. Such approximations are given by averaging real-valued multivariate functions which are typically scalings of squared (d+1)-volumes of (d+1)-simplices. Specifically, we show that such averages are comparable to the square of the d-dimensional least squares error of that measure, where the comparison depends on a simple quantitative geometric property of it. This result is a higher dimensional generalization of the elementary fact that the double integral of the squared distances between points is proportional to the variance of measure. We relate our work to two recent algorithms, one for clustering affine subspaces and the other for Monte-Carlo SVD based on volume sampling

Averages of central L-values of Hilbert modular forms with an application to subconvexity

We use the relative trace formula to obtain exact formulas for central values of certain twisted quadratic base change L-functions averaged over Hilbert modular forms of a fixed weight and level. We apply these formulas to the subconvexity problem for these L-functions. We also establish an equidistribution result for the Hecke eigenvalues weighted by these L-values.Comment: 57 pages, minor changes made to version 1. The final version of this article will be published in the Duke Mathematical Journal, Vol. 149, No. 2, published by Duke University Pres

Cross-infection in cystic fibrosis: The knowledge and behaviour of adult patients

AbstractIntroductionThe knowledge and behaviour of adult patients with cystic fibrosis (CF) regarding cross-infection are ill understood.MethodsA questionnaire was designed to investigate this at the West Midlands Adult CF Centre.Results94 patients completed the questionnaire. 54%, 36% and 46% had “no idea” of the lifetime risk of contracting Burkholderia cepacia complex, epidemic strains of Pseudomonas aeruginosa, and MRSA, respectively. 25–33% did not know the consequences of infection with these bacteria. 35% mixed with other people with CF, 6.5% during physiotherapy or nebulizer use. Most respondents did not think quality of life was significantly linked with segregation from other patients with CF.ConclusionsAdults with CF, at least in the West Midlands, have poor knowledge of the risk and consequences of cross-infection. A significant proportion ignored advice not to mix with other patients, although segregation was not thought to impact upon quality of life. This suggests that more education about the risks of cross-infection would be beneficial

Exact averages of central values of triple product L-functions

We obtain exact formulas for central values of triple product L-functions averaged over newforms of weight 2 and prime level. We apply these formulas to non-vanishing problems. This paper uses a period formula for the triple product L-function proved by Gross and Kudla