Publications by authors named "K B Johnson"

Background: Infant antibiotic use is associated with increased risk of asthma. We examined the population impact of antibiotic exposure in the first year of life on the burden of pediatric asthma in British Columbia, Canada, using simulation modeling.

Methods: We performed a Bayesian meta-analysis of empirical studies to construct dose-response equations between antibiotic exposure in the first year of life and pediatric (<19 years of age) asthma.

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Objective: This study examined the effects of changes in patient positioning on radiation exposure for panoramic and cone beam computed tomography (CBCT) radiographic examinations by measuring effective dose (E) and equivalent doses.

Study Design: Simulated radiographic examinations with optimal and suboptimal positioning-anterior shift by 1 centimeter (cm), posterior shift by 1 cm, chin lowered by 10 degrees (°), chin elevated by 10°, rotation by 10°, and lateral shift by 1 cm-were conducted using a tissue-equivalent phantom and optically-stimulated luminescent dosimeters. Exposures were made with the RAYSCAN Alpha Plus 160 X-ray unit using the following exposure parameters: panoramic, 80 kVp, 14 mA, and 13.

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We assessed the real-world particulate emissions of a goods movement diesel vehicle, with an emphasis on total particle number and solid particle number emissions at different cutoff sizes. The vehicle was tested on routes in the South Coast Air Basin (SCAB) of California, representative of typical goods movement operation between the ports to warehouses and logistic centers with a mixture of urban and highway driving, as well as elevation change. We evaluated emissions during normal vehicle operation and diesel particulate filter (DPF) active regeneration events.

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