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Biomedical subjects

J C Posner

Publications and source records attributed to J C Posner.

11 recordsLinked to original sources

Exposure to traffic among urban children injured as pedestrians.

OBJECTIVES: To explore the immediate pre-crash activities and the routine traffic exposure (street crossing and play) in a sample of urban children struck by automobiles. In particular, the traffic exposure of children who were struck while playing was compared with that of those struck while crossing streets. DESIGN: Cross sectional survey. SETTING: Urban pediatric emergency department. PATIENTS: A total of 139 children ages 4-15 years evaluated for acute injuries resulting from pedestrian-motor vehicle collisions during a 14 month period. MAIN OUTCOME MEASURES: Sites of outdoor play, daily time in outdoor play, weekly number of street crossings, pre-crash circumstance (play v walking). RESULTS: Altogether 39% of the children routinely used the street and 64% routinely used the sidewalks as play areas. The median number of street crossings per week per child was 27. There were no differences in exposures for the 29% who were hit while playing compared with the 71% who were hit while walking. Although 84% of the children walked to or from school at least one day per week, only 15% of the children were struck while on the school walking trip. The remainder were injured either while playing outdoors or while walking to other places. CONCLUSIONS: Urban children who are victims of pedestrian crashes have a high level of traffic exposure from a variety of circumstances related to their routine outdoor playing and street crossing activities. The distributions of traffic exposures were similar across the sample, indicating that the sample as a whole had high traffic exposure, regardless of the children's activity preceding the crash. Future pedestrian injury programs should address the pervasive nature of children's exposure to traffic during their routine outdoor activities.

Accidents, Traffic↗

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Accidents, Traffic↗

A thermodynamic treatment of passive monitors.

Previous mathematical descriptions of sampling using passive monitors have used Fick's First Law of diffusion and the assumption that the concentration of adsorbate in the vapor phase above the sorbent is zero. This paper shows that by introducing a simplified expression for the equilibrium vapor pressure, behavior more nearly resembling that observed for passive monitors is predicted. The theory can also be applied to the case of loss of sample from a diffusive monitor. Experimental evidence is also provided which demonstrates that the theory adequately describes the observed results.

Air Pollutants↗

Comments on ''Phase Equilibrium Method for Determination of Desorption Efficiencies'' and some extensions for use in methods development.

Dommer and Melcher recently published a paper entitled, "Phase Equilibrium Method for Determination of Desortpion Efficiencies". The equilibrium expression which they assumed is shown to be a special case of the langmuir isotherm. The equation they derived relating the desorption efficiency, the equilibrium constant and the ratio of the weight of the solid to that of the liquid phase is discussed; the use of this relationship to demonstrate the invariance of the equilibrium constant, K, with changing ratios of liquid to solid phase is shown to lead to large uncertainties in K when the desorption efficiency is high. Use of their equation to derive expressions useful in methods development are presented and their potential utility discussed.

Adsorption↗

Recovery of acrylonitrile from charcoal tubes at low levels.

Data are presented for the recovery of acrylonitrile from charcoal tubes at levels lower than those tested in NIOSH Method S156. A 2% by volume acetone in CS2 solution is used as desorbing solvent. An injection volume of 2 muL and a 3-m long by 3.2-mm o.d. (10-ft x 1/8-in) stainless steel column filled with 20% SP-1000 on 80/100 Supelcoport gives adequate resolution of the acrylonitrile. Results indicate that recoveries are adequate for sample sizes which correspond to a 15-liter sample at 0.5 and 0.25 ppm, and that acrylonitrile collected on carbon in the absence of inhibitor is stable for at least a week.

Acetone↗