Disturbance and temporal partitioning of the activated sludge metacommunity.

The resilience of microbial communities to press disturbances and whether ecosystem function is governed by microbial composition or by the environment have not been empirically tested. To address these issues, a whole-ecosystem manipulation was performed in a full-scale activated sludge wastewater treatment plant. The parameter solids retention time (SRT) was used to manipulate microbial composition, which started at 30 days, then decreased to 12 and 3 days, before operation was restored to starting conditions (30-day SRT).

On the correlation between single-frequency impedance measurements and human skin permeability to water.

The objective of this study was to quantitatively compare measurements of tritiated water permeability with impedance determined at either 100 or 1000 Hz using an LCR databridge on the same pieces of skin. A previously published expression based on a simple circuit of a parallel resistor and constant phase element (CPE) was used to relate (RPARA) measured at different frequencies to the DC resistance (RskinA) and the steady-state skin permeability of tritiated water (kp). Using this analysis, kp and (RPARA) data from three laboratories were shown to be consistent with each other, and kp and (RskinA) estimated from (RPARA) were linearly correlated.

Community woodstove changeout and impact on ambient concentrations of polycyclic aromatic hydrocarbons and phenolics.

A large woodstove changeout program was carried out in Libby, Montana, with the goal of reducing ambient levels of PM2.5. This provided researchers the opportunity to measure ambient concentrations of phenolic and polycyclic aromatic hydrocarbons (PAHs) before, during, and after the changeout of nearly 1200 stoves to evaluate the effectiveness of the intervention.

Improved bioequivalence assessment of topical dermatological drug products using dermatopharmacokinetics.

Purpose: A dermatopharmacokinetic (DPK) approach, in which drug levels in the stratum corneum (SC) are measured as a function of time post-application and post-removal of the product using tape-strip sampling in vivo in humans, has been considered for the comparative assessment of topical bioavailability. Its application to-date has been limited by contradictory results and concerns that variability in the method necessitates large numbers of treatment sites and volunteers. The objective of this study was to test whether a revised protocol could better assess bioequivalence.

Optimizing metrics for the assessment of bioequivalence between topical drug products.

Purpose: Stratum corneum tape stripping post-application of a drug product followed by analysis of the active agent in this tissue layer is an approach being seriously considered for the comparative assessment of topical bioavailability. Key issues revolve around how best to perform this experiment and interpret the data.

Methods: Using previously published results from a comparative study of three 0.

Lung cancer and internal lung doses among plutonium workers at the Rocky Flats Plant: a case-control study.

The authors conducted a nested case-control study of the association between lung cancer mortality and cumulative internal lung doses among a cohort of workers employed at the Rocky Flats Plant in Colorado from 1951 to 1989. Cases (n = 180) were individually matched with controls (n = 720) on age, sex, and birth year. Annual doses to the lung from plutonium, americium, and uranium isotopes were calculated for each worker with an internal dosimetry model.

Uncertainty in measurements of dermal absorption of pesticides.

Dermal absorption experiments form an important component in the assessment of risk from exposure to pesticides and other substances. Much dermal absorption data is gathered in rat experiments carried out using a certain standard protocol. Uncertainties in these data arise from many sources and can be quite large.