The purpose of this paper is to undertake a statistical analysis to specify empirical distributions and to estimate univariate parametric probability distributions for air exchange rates for residential structures in the United States. To achieve this goal, we used data compiled by the Brookhaven National Laboratory using a method known as the perfluorocarbon tracer (PFT) technique. While these data are not fully representative of all areas of the country or all housing types, they are judged to be by far the best available. The analysis is characterized by four key points: the use of data for 2,844 households; a four-region breakdown based on heating degree days, a best available measure of climatic factors affecting air exchange rates; estimation of lognormal distributions as well as provision of empirical (frequency) distributions; and provision of these distributions for all of the data, for the data segmented by the four regions, for the data segmented by the four seasons, and for the data segmented by a 16 region by season breakdown. Except in a few cases, primarily for small sample sizes, air exchange rates were found to be well fit by lognormal distributions (adjusted R2 > 0.95). The empirical or lognormal distributions may be used in indoor air models or as input variables for probabilistic human health risk assessments.

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Many intracellular membranes contain ion channels, although their physiological roles are often poorly understood. In this study we incorporated single anion channels colocalized with rat brain endoplasmic reticulum (ER) ryanodine-sensitive Ca(2+)-release channels into planar lipid bilayers. The channels opened in bursts, with more activity at negative (cytoplasm-ER lumen) membrane potentials, and they occupied four open conductance levels with frequencies well described by the binomial equation. The probability of a protomer being open decreased from approximately 0.7 at -40 mV to approximately 0.2 at +40 mV, and the channels selected between different anions in the order PSCN > PNO3 > PBr > PCl > PF. They were also permeant to cations, including the large cation Tris+ (PTris/PCl = 0.16). Their conductance saturated at 170 pS in choline Cl. The channels were inactivated by 15 microM 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS) and blocked with low affinity (KD of 1-100 microM) by anthracene-9-carboxylic acid, ethacrynic acid, frusemide (furosemide), HEPES, the indanyloxyacetic acid derivative IAA-94, 5-nitro-2-(3-phenylpropylamino)-benzoate (NPPB), and Zn2+. Unlike protein translocation pores, the channels were unaffected by high salt concentrations or puromycin. They may regulate ER Ca2+ release, or be channel components en route to their final cellular destinations. Alternatively, they may contribute to the fusion machinery involved in intracellular membrane trafficking.

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Using exploratory data analysis, probability plots, scatterplots, and computer animations to rotate and visualize the data, we fit a trivariate Normal distribution to data for the height, the natural logarithm of body weight, and the body fat for 646 men between the ages of 50 and 80 years as reported by the medical staff of the US Veterans Administration's "Normative Aging Study" in Boston, MA. Although these data do not include any children, women, or young men, the measurements represent the best data that we could find through a 4-year search. We believe that these data are well measured and reliable for men in the specified age range and that these data reveal an interesting statistical pattern for use in probabilistic PBPK models. Introduction and Data