Field-based evaluation of semipermeable membrane devices (SPMDs) as passive air samplers of polyaromatic hydrocarbons (PAHs)

Semipermeable membrane devices (SPMDs) have been used as passive air samplers of semivolatile organic compounds in a range of studies. However, due to a lack of calibration data for polyaromatic hydrocarbons (PAHs), SPMD data have not been used to estimate air concentrations of target PAHs. In this study, SPMDs were deployed for 32 days at two sites in a major metropolitan area in Australia. High-volume active sampling systems (HiVol) were co-deployed at both sites. Using the HiVol air concentration data from one site, SPMD sampling rates were measured for 12 US EPA Priority Pollutant PAHs and then these values were used to determine air concentrations at the second site from SPMD concentrations. Air concentrations were also measured at the second site with co-deployed HiVols to validate the SPMD results. PAHs mostly associated with the vapour phase (Fluorene to Pyrene) dominated both the HiVol and passive air samples. Reproducibility between replicate passive samplers was satisfactory (CV < 20%) for the majority of compounds. Sampling rates ranged between 0.6 and 6.1 m(3) d(-1). SPMD-based air concentrations were calculated at the second site for each compound using these sampling rates and the differences between SPMD-derived air concentrations and those measured using a HiVol were, on average, within a factor of 1.5. The dominant processes for the uptake of PAHs by SPMDs were also assessed. Using the SPMD method described herein, estimates of particulate sorbed airborne PAHs with five rings or greater were within 1.8-fold of HiVol measured values. (C) 2004 Elsevier Ltd. All rights reserved.

ATC-lab: An air traffic control simulator for the laboratory

Air Traffic Control Laboratory Simulator (ATC-lab) is a new low- and medium-fidelity task environment that simulates air traffic control. ATC-lab allows the researcher to study human performance of tasks under tightly controlled experimental conditions in a dynamic, spatial environment. The researcher can create standardized air traffic scenarios by manipulating a wide variety of parameters. These include temporal and spatial variables. There are two main versions of ATC-lab. The medium-fidelity simulator provides a simplified version of en route air traffic control, requiring participants to visually search a screen and both recognize and resolve conflicts so that adequate separation is maintained between all aircraft. The low-fidelity simulator presents pairs of aircraft in isolation, controlling the participant's focus of attention, which provides a more systematic measurement of conflict recognition and resolution performance. Preliminary studies have demonstrated that ATC-lab is a flexible tool for applied cognition research.

Phase equilibria in the system Fe-Zn-O at intermediate conditions between metallic-iron saturation and air

The phase equilibria in the FeO-Fe2O3-ZnO system have been experimentally investigated at oxygen partial pressures between metallic iron saturation and air using a specially developed quenching technique, followed by electron probe X-ray microanalysis (EPMA) and then wet chemistry for determination of ferrous and ferric iron concentrations. Gas mixtures of H-2, N-2, and CO2 or CO and CO2 controlled the atmosphere in the furnace. The determined metal cation ratios in phases at equilibrium were used for the construction of the 1200 degrees C isothermal section of the Fe-Zn-O system. The univariant equilibria between the gas phase, spinel, wustite, and zincite was found to be close to pO(2) = 1 center dot 10(-8) atm at 1200 degrees C. The ferric and ferrous iron concentrations in zincite and spinel at equilibrium were also determined at temperatures from 1200 degrees C to 1400 degrees C at pO(2) = 1 center dot 10(-6) atm and at 1200 degrees C at pO(2) values ranging from 1 center dot 10(-4) to 1 center dot 10(-8) atm. Implications of the phase equilibria in the Fe-Zn-O system for the formation of the platelike zincite, especially important for the Imperial Smelting Process (ISP), are discussed.

The effect of the atmosphere and the role of pore filling on the sintering of aluminium

Alloys of Al-3.8Cu-1Mg-0.7Si, Al-4Cu-0.6Si-0.1Mg, Al-4Cu-1.2Mg and Al-1.9Mg-1.9Si were made using air atomised powder and conventional press-and-sinter powder metallurgy techniques. These were sintered under nitrogen with a controlled water content which varied from 3 to 630 ppm (a dew point of -69 to -25 degrees C), nitrogen-5%hydrogen, argon and argon-5% hydrogen, all at atmospheric pressure, or a vacuum of

An examination of the dynamic relationship between self-efficacy and performance across levels of analysis and levels of specificity

This research used resource allocation theory to generate predictions regarding dynamic relationships between self-efficacy and task performance from 2 levels of analysis and specificity. Participants were given multiple trials of practice on an air traffic control task. Measures of task-specific self-efficacy and performance were taken at repeated intervals. The authors used multilevel analysis to demonstrate differential and dynamic effects. As predicted, task-specific self-efficacy was negatively associated with task performance at the within-person level. On the other hand, average levels of task-specific self-efficacy were positively related to performance at the between-persons level and mediated the effect of general self-efficacy. The key findings from this research relate to dynamic effects - these results show that self-efficacy effects can change over time, but it depends on the level of analysis and specificity at which self-efficacy is conceptualized. These novel findings emphasize the importance of conceptualizing self-efficacy within a multilevel and multispecificity framework and make a significant contribution to understanding the way this construct relates to task performance.