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1.  Low Dose Radiation Exposure and Atherosclerosis in ApoE−/− Mice 
Radiation research  2011;175(5):665-676.
The hypothesis that single low dose exposures (0.025–0.5 Gy) to low LET radiation, given at either high (about 150 mGy/min) or low (1 mGy/min) dose rate, would promote aortic atherosclerosis was tested in female C57BL/6J mice genetically predisposed to this disease (ApoE−/− ). Mice were exposed either at early stage disease (2 months of age) and examined 3 or 6 months later, or at late stage disease (8 months of age) and examined 2 or 4 months later. Changes in aortic lesion frequency, size and severity, as well as total serum cholesterol levels and the uptake of lesion lipids by lesion associated macrophages were assessed. Statistically significant changes in each of these measures were observed, depending on dose, dose rate and disease stage. In all cases, the results were distinctly non-linear with dose, with maximum effects tending to occur at 25 or 50 mGy. In general, low doses given at low dose rate at either early or late stage disease were protective, slowing the progression of the disease by one or more of these measures. Most effects appeared and persisted for months after the single exposures, but some were ultimately transitory. In contrast to exposure at low dose rate, high dose rate exposure at early stage disease produced both protective and detrimental effects, suggesting that low doses may influence this disease by more than one mechanism, and dose rate is an important parameter. These results contrast with the known, generally detrimental effects of high doses on the progression of this disease in the same mice, and in humans, suggesting that a linear extrapolation of the known increased risk from high doses to low doses is not appropriate.
PMCID: PMC3998759  PMID: 21375359
Radiation; low doses; heart disease; atherosclerosis; mice; apolipoprotein E
2.  A Novel Size-Selective Airborne Particle Size Fractionating Instrument for Health Risk Evaluation 
Annals of Occupational Hygiene  2009;53(3):225-237.
Health risks associated with the inhalation of airborne particles are known to be influenced by particle size. Studies have shown that certain nanoparticles, with diameters <100 nm, have increased toxicity relative to larger particles of the same substance. A reliable, size-resolving sampler able to collect a wide range of particle sizes, including particles with sizes in the nanometre range, would be beneficial in investigating health risks associated with the inhalation of airborne particles. A review of current aerosol samplers used for size-resolved collection of airborne particles highlighted a number of limitations. These could be overcome by combining an inertial deposition impactor with a diffusion collector in a single device. Verified theories of diffusion and inertial deposition suggested an optimal design and operational regime. The instrument was designed for analysing mass distribution functions. Calibration was carried out using a number of recognized techniques. The sampler was tested in the field by collecting size-resolved samples of lead containing aerosols present at workplaces in factories producing crystal glass. The mass deposited on each screen proved sufficient to be detected and measured by an appropriate analytical technique. Mass concentration distribution functions of lead were produced. The nanofraction of lead in air varied from 10 to 70% by weight of total lead.
PMCID: PMC2662094  PMID: 19279163
Brownian diffusion; humidity; inertial deposition; nanoparticles; size-resolved chemical composition; PM10

Results 1-3 (3)