Phenomenological Constraints on the Transport Properties of QCD Matter with Data-Driven Model Averaging.

Using combined data from the Relativistic Heavy Ion and Large Hadron Colliders, we constrain the shear and bulk viscosities of quark-gluon plasma (QGP) at temperatures of ∼150-350 MeV. We use Bayesian inference to translate experimental and theoretical uncertainties into probabilistic constraints for the viscosities. With Bayesian model averaging we propagate an estimate of the model uncertainty generated by the transition from hydrodynamics to hadron transport in the plasma's final evolution stage, providing the most reliable phenomenological constraints to date on the QGP viscosities.

A head-only exposure system for controlled exposures of small rodents.

We have designed a low-cost, compact, head-only exposure system which is easy to use and allows exposure of up to 8 or 16 small rodents depending on the chamber used with the system. Animals are exposed without anesthesia or extreme restraint. Deflection tubes at the chamber inlet and outlet serve to provide turbulent flow within the chamber. Performance of the exposure system was evaluated by analyzing data which was collected during investigations of the kinetics of respirable nickel chloride (NiCl2) and cobalt chloride (CoCl2) aerosols in Sprague-Dawley rats. Acute 2 h exposure to NiCl2 at concentrations ranging from 129 to 1208 micrograms Ni/m3 (MMAD 0.7-0.9 micron, sigma g 1.2-1.5) had a mean run-to-run coefficient of variation (cv) in chamber concentration of 11.6%, and a mean within-run cv of 8.5%. A 26-day repeated exposure of 3 groups of rats to 18.4 micrograms Ni/m3 gave a mean run-to-run cv of 20.9%, mean within-run cv of 10.2%, and within-day cv of 14.5%. Acute exposure studies with CoCl2 at concentrations ranging from 298 to 1371 micrograms Co/m3 (MMAD 0.9, sigma g 1.4) produced a mean run-to-run cv of 8.4% and a mean within-run cv of 7.8%. The repeated exposure of 2 groups of rats for 5 days to CoCl2 at a concentration of 583 micrograms Co/m3 had a mean run-to-run cv of 10.1%, a within-run cv of 7.4% and a within-day cv of 6.8%. The distribution of aerosol within the chamber is shown to have been uniform, and chamber performance was linear over the range tested. This system provides an inexpensive and uniform means of conducting inhalation exposure studies with selected airborne contaminants that might represent a potential health hazard.

Pharmacokinetic modeling of the lung burden from repeated inhalation of nickel aerosols.

The saturable nature of the clearance of soluble nickel compounds from the lung was studied by repeated exposures of rats to respirable submicron-size nickel aerosols. Using Michaelis-Menten type kinetics for removal of nickel lung burdens and a constant rate of deposition, the lung nickel burdens were simulated by computer. The computer simulation was used to design a repeated exposure regimen to test further the hypothesis of saturable clearance. Male Sprague-Dawley rats were exposed for 2 h/day to nickel chloride aerosols at either 90 or 400 micrograms Ni/m3 for up to 14 days. During the 22 h between exposures and up to 3 days post-exposure rats were kept in clean air. The particle size of the aerosol ranged from 0.7 to 0.9 micron mass median aerodynamic diameter with a geometric standard deviation of 1.2-1.4. A steady-state nickel lung burden was observed at 90 micrograms/m3, as predicted from computer modeling, while lung burdens continued to increase with repeated exposure to 400 micrograms Ni/m3. The best fit for the experimental data was obtained with a maximum clearance velocity (Vmax) of 34.6 ng Ni/g X h and a Michaelis-Menten constant for transport (Kt) of 1380 ng Ni/g. The percentage of submicron nickel chloride aerosols retained in the lung was 6.9%. These data support the hypothesis of a saturable clearance mechanism for soluble nickel and provide physiological constants useful for estimating human health risks from nickel inhalation.

Eliciting and combining subjective judgments about uncertainty.

Frequently, health care decisions must be made before compelling and unequivocal evidence is available about the benefits, risks, and costs of a proposed new health technology. It is common for decision makers to seek the advice and opinions of experts to supplement the available evidence. This article reviews some of the methods used or recommended for eliciting the opinions of experts about uncertain events and for combining these opinions with those of others and with available empirical evidence.