Regional source identification using Lagrangian stochastic particle dispersion and HYSPLIT backward-trajectory models.

The main objective of this study was to investigate the capabilities of the receptor-oriented inverse mode Lagrangian Stochastic Particle Dispersion Model (LSPDM) with the 12-km resolution Mesoscale Model 5 (MM5) wind field input for the assessment of source identification from seven regions impacting two receptors located in the eastern United States. The LSPDM analysis was compared with a standard version of the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) single-particle backward-trajectory analysis using inputs from MM5 and the Eta Data Assimilation System (EDAS) with horizontal grid resolutions of 12 and 80 km, respectively. The analysis included four 7-day summertime events in 2002; residence times in the modeling domain were computed from the inverse LSPDM runs and HYPSLIT-simulated backward trajectories started from receptor-source heights of 100, 500, 1000, 1500, and 3000 m.

Toward effective source apportionment using positive matrix factorization: experiments with simulated PM2.5 data.

To elucidate the relationship between factors resolved by the positive matrix factorization (PMF) receptor model and actual emission sources and to refine the PMF modeling strategy, speciated PM2.5 (particulate matter with aerodynamic diameter < 2.5 microm) data generated from a state-of-the-art chemical transport model for two rural sites in the eastern United States are subjected to PMF analysis.

Evaluation of regional-scale receptor modeling.

The ability of receptor models to estimate regional contributions to fine particulate matter (PM2.5) was assessed with synthetic, speciated datasets at Brigantine National Wildlife Refuge (BRIG) in New Jersey and Great Smoky Mountains National Park (GRSM) in Tennessee. Synthetic PM2.

Toward Effective Source Apportionment Using Positive Matrix Factorization: Experiments with Simulated PM Data.

To elucidate the relationship between factors resolved by the positive matrix factorization (PMF) receptor model and actual emission sources and to refine the PMF modeling strategy, speciated PM (particulate matter with aerodynamic diameter <2.5 μm) data generated from a state-of-the-art chemical transport model for two rural sites in the eastern United States are subjected to PMF analysis. In addition to χ- and R used to infer the quality of fitting, the interpretability of PMF factors with respect to known primary and secondary sources is evaluated using a root mean square difference analysis.

Evaluation of Regional-Scale Receptor Modeling.

The ability of receptor models to estimate regional contributions to fine particulate matter (PM) was assessed with synthetic, speciated datasets at Brigantine National Wildlife Refuge (BRIG) in New Jersey and Great Smoky Mountains National Park (GRSM) in Tennessee. Synthetic PM chemical concentrations were generated for the summer of 2002 using the Community Multiscale Air Quality (CMAQ) model and chemically speciated PM source profiles from the U.S.

Transport and dispersion during wintertime particulate matter episodes in the San Joaquin Valley, California.

Data analysis and modeling were performed to characterize the spatial and temporal variability of wintertime transport and dispersion processes and the impact of these processes on particulate matter (PM) concentrations in the California San Joaquin Valley (SJV). Radar wind profiler (RWP) and radio acoustic sounding system (RASS) data collected from 18 sites throughout Central California were used to estimate hourly mixing heights for a 3-month period and to create case studies of high-resolution diagnostic wind fields, which were used for trajectory and dispersion analyses. Data analyses show that PM episodes were characterized by an upper-level ridge of high pressure that generally produced light winds through the entire depth of the atmospheric boundary layer and low mixing heights compared with nonepisode days.

The effect of reducing the fine-particle mass of salmeterol from metered-dose inhalers on bronchodilatation and bronchoprotection against methacholine challenge: a randomized, placebo-controlled, double-blind, crossover study.

Objective: This study examined the clinical relevance of fine-particle mass (FPM) delivered from metered dose inhalers (MDIs) to bronchodilatation and bronchoprotection against methacholine challenge by comparing a marketed chlorofluorocarbon (CFC) formulation of salmeterol with an investigational hydrofluoroalkane (HFA)formulation.

Methods: This was a randomized, double-blind, placebo-controlled, 3-way crossover study in patients with mild to moderate asthma who had a forced expiratory volume in 1 second (FEV (1)) of > or =60% predicted and a base-line provocation dose of inhaled methacholine required to produce a 20% decrease in FEV(1) (PD (20) [methacholine]) of < or =3.2 mg.

Success of non-traditional students in an undergraduate occupational therapy programme.

An exit survey designed to examine the experiences of occupational therapy undergraduates was administered to 365 students in a four-year honours programme. The survey had a response rate of 51% (186). The survey was informed and supplemented by focus groups with international students and computer-mediated conferencing with community leaders from relevant ethnic minorities.