Limitations on the uses of multimedia exposure measurements for multipathway exposure assessment--Part II: Effects of missing data and imprecision.

Multimedia data from two probability-based exposure studies were investigated in terms of how missing data and measurement-error imprecision affected estimation of population parameters and associations. Missing data resulted mainly from individuals'refusing to participate in certain measurement activities, rather than from field or laboratory problems; it suggests that future studies should focus on methods for maximizing participation rates. Measurement error variances computed from duplicate-sample data were small relative to the inherent variation in the populations; consequently, adjustments in nonparametric percentile estimates to account for measurement imprecision were small. Methods of adjustment based on lognormality assumptions, however, appeared to perform poorly.     

The experimental determination of the neutron cross section for selected solvents

An experiment was conducted in order to determine the macroscopic neutron cross section of various solvents useful in neutron radiographic inspection. These solvents are used to dissolve the salts of high cross-section elements in order to formulate a fluid of maximal neutron cross section. The resulting fluid could then be used as a contrast enhancing agent in neutron radiographic inspection. This experiment was planned using statistical experimental design techniques. The results of this experiment provided a quantitative measure of the mean and standard deviation of the macroscopic neutron cross section for the nine fluids investigated. A control fluid was found to be in close agreement with published values.     

Evaluating Ozone as a Remedial Treatment for Removing RDX from Unsaturated Soils

Years of wastewater discharge at the Department of Energy’s Pantex Plant have contaminated the vadose zone and underlying perched aquifer with hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX). Because the vadose zone is acting as a continual source of groundwater contamination, removing RDX from the unsaturated zone is paramount to prevent further contamination. We determined the efficacy of ozone to degrade and mineralize RDX. Solution experiments showed that ozone (27?mg?L?1; 150?mL?min?1) was effective in mineralizing 80% of the RDX (30?mg?RDX?L?1) provided that some Pantex soil was present to buffer the solution pH. Soil columns treated with ozone produced 50% RDX mineralization within 1 day and >80% within 7 day. Experiments designed to evaluate aerobic biodegradation following partial ozonation of a RDX solution showed that ozone-generated RDX products were much more biodegradable than untreated controls in aerobic microcosms (35 versus <0.3% cumulative mineralization). These results support the use of ozone as a remedial treatment for the contaminated vadose zone at the Pantex facility.     

The integrated academic information management system at Columbia-Presbyterian Medical Center.

Over the past seven years, Columbia-Presbyterian Medical Center has been planning and implementing an integrated academic information management system. Accomplishments to date include establishing an institutional information architecture, installing a campus-wide network of workstations, recruiting the staff needed to develop and implement the system, and developing various applications. This paper presents the rationale and steps involved in these accomplishments, as well as data on use of the system so far.     

Spectral characterisation and frame synchronisation of optical fibre digital PPM

The discrete time decoding of data in pulse position modulation calls for accurate timing synchronisation, particularly at the frame rate. The spectral properties of optical fibre digital PPM are considered. An original expression is presented for predicting the spectrum and it is shown that, unlike satellite PPM, a component exists at the frame rate which may be used for timing extraction purposes. Further, it is illustrated that the modulation index can be used to enhance this component by up to 19 dB. This has been verified practically, with the results agreeing to within 1 dB of those predicted from the original expression presented.<>     

The perception of natural contour.

The observation that natural curves and surfaces are often fractal suggests that people may be sensitive to their statistical properties. The perceptual protocols that underlie discrimination between fractals and between other types of random contour and fractals are examined. Discrimination algorithms that have precisely the same sensitivities as human observers are constructed. These algorithms do not recognize the integrated scale hierarchy intrinsic to fractal form and operate by imposing a metatheory of structure that is based on a signal–noise distinction. The success of the algorithms implies that (1) self-affinity in random fractals is not perceptually recovered and (2) people have a natural disposition to view contour in terms of signal and noise. The authors propose that this disposition be understood as a principle of perceptual organization. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

MAGNESIUM HYDROXIDE FILLED EVA: THE EFFECTS OF FILLER SURFACE MODIFICATION ON THE STRENGTH OF FILLER/MATRIX ADHESION AND THE CONSEQUENCES FOR COMPOSITE STRUCTURE AND PROPERTIES

The interaction of ammonium stearate (AS) and γ-aminopropyltriethoxysilane (APS) treatments with a magnesium hydroxide flame retardant filler and their effects on its use in an ethylene vinyl acetate copolymer compound have been investigated. The work has shown clear evidence of changes in the structure of the surface layers formed on the filler as the amount of additive is increased and the levels at which these occur can be correlated with theoretical monolayer quantities. Infrared (IR) spectroscopy data suggest that the stearate coating changes from a half salt to a full salt as the coating level is increased and that the APS coating on the filler initially has a significant bicarbonate content, presumably due to reaction with atmospheric carbon dioxide. The effect of coating level on the melt flow rate, insoluble matrix content, crystallisation behaviour, tensile properties, limiting oxygen index, and ageing of the filled compound has been studied. Distinct trends have been observed, many of which can be correlated with the structure of the filler surface layers. Of particular importance is the observation that, unlike APS, excess stearate appears to promote detrimental ageing effects.     

RETARDATION AND REPAIR OF FATIGUE CRACKS BY ADHESIVE INFILTRATION

Abstract— This paper presents results which demonstrate that polymeric filler materials, such as low-viscosity epoxies, can be vacuum-infiltrated into fatigue cracks in 7050 aluminium alloy to produce significant levels of fatigue crack retardation. It was found that the main test variable affecting the degree of retardation was the stress level at which the adhesive was introduced and cured. Two infiltrated adhesives were tested.
Infiltration at 0% (of the original) peak fatigue stress level produced negligible retardation, while infiltration at the 80% stress level produced about 300% increase in fatigue life for one adhesive and 3000% for the other adhesive. For the highest infiltration stress level both crack-face wedging and adhesion contributed initially to the retardation, but the adhesive component ceased after a crack grew through the adhesive to the original crack tip position. The results are discussed in terms of the applicability of the technique to highly-stressed aircraft components.     

Compartmentation of phosphoglycerate kinase in Trypanosoma brucei plays a critical role in parasite energy metabolism

African trypanosomes compartmentalize glycolysis in a microbody, the glycosome. When growing in the mammalian bloodstream, trypanosomes contain only a rudimentary mitochondrion, and the first seven glycolytic enzymes, including phosphoglycerate kinase, are located in the glycosome. Procyclic trypanosomes, growing in the gut of tsetse flies, possess a fully developed mitochondrion that is active in oxidative phosphorylation. The first six glycolytic enzymes are still glycosomal, but phosphoglycerate kinase is now found in the cytosol. We demonstrate here that bloodstream trypanosomes are killed by expression of cytosolic phosphoglycerate kinase. The toxicity depends on both enzyme activity and cytosolic location. One possible explanation is that cytosolic phosphoglycerate kinase creates an ATP-generating shunt in the cytosol, thus preventing full ATP regeneration in the glycosome and ultimately inhibiting the first, ATP-consuming, steps of glycolysis.