Microcantilever sensors coated with doped polyaniline for the detection of water vapor.

In the present work, PANI (polyaniline) emeraldine salt (doped) and base (dedoped) were used as the sensitive layer of a silicon microcantilever, and the mechanical response (deflection) of the bimaterial (coated microcantilever) was investigated under the influence of humidity. PANI in the emeraldine base oxidation state was obtained by interfacial synthesis and was deposited on the microcantilever surface by spin-coating (dedoped). Next, the conducting polymer was doped with 1 M HCl (hydrochloric acid). A four-quadrant AFM head with an integrated laser and a position-sensitive detector (AFM Veeco Dimension V) was used to measure the optical deflection of the coated microcantilever. The deflection of the coated (doped and undoped PANI) and uncoated microcantilever was measured under different humidities (in triplicate) at room pressure and temperature in a closed chamber to evaluate the sensor's sensitivity. The relative humidity (RH) in the chamber was varied from 20% to 70% using dry nitrogen as a carrier gas, which was passed through a bubbler containing water to generate humidity. The results showed that microcantilevers coated with sensitive layers of doped and undoped PANI films were sensitive (12,717 ± 6% and 6,939 ± 8%, respectively) and provided good repeatability (98.6 ± 0.015% and 99 ± 0.01%, respectively) after several cycles of exposure to RH. The microcantilever sensor without a PANI coating (uncoated) was not sensitive to humidity. The strong effect of doping on the sensitivity of the sensor was attributed to an increased adsorption of water molecules dissociated at imine nitrogen centers, which improves the performance of the coated microcantilever sensor. Moreover, microcantilever sensors coated with a sensitive layer provided good results in several cycles of exposure to RH (%).

Influence of a statewide trauma system on pediatric hospitalization and outcome.

BACKGROUND: During the years 1987-1991, a statewide trauma system was implemented in Oregon (Ore) but not in Washington (Wash). Incidence of hospitalization, frequency of death and risk-adjusted odds of death for injured children (< 19 years) in the two adjacent states were compared for two time periods (1985-1987 and 1991-1993). METHODS: State populations of injured children (International Classification of Diseases, 9th Revision-Clinical Modification, code 800-959) were identified through a Hospital Discharge Index. Hospitals in counties with a population density < 50 persons/square mile were designated rural. Incidence rates are events/10,000 pediatric population per year. RESULTS: The pediatric population increased in both states (Ore: 687,000-758,000; Wash: 1,159,000-1,336,000). Incidence of hospitalization for all injured children in entire states declined (Ore: 66.5-38.5; Wash: 54-33); also in rural hospitals (Ore: 67.5-32; Wash: 48 to 31). Seriously injured children (score on the Injury Severity Scale > 15) had a lower incidence in 1991-1993 of admission to rural hospitals (Ore: 2.98; Wash: 2.82) compared with incidence for entire states (Ore: 4.61; Wash: 4.62); in 1985-1987 the incidence was not different. Furthermore risk adjusted odds of death for seriously injured children was significantly lower in Oregon than in Washington in the later time period. CONCLUSION: Both states show a similar temporal trend toward a declining frequency of death for children hospitalized with injuries. Injury prevention strategies appear to have reduced the number of serious injuries in both states. However, seriously injured children demonstrated a reduced risk of death in Oregon, consistent with benefit from a statewide trauma system.