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W J Cooper

Publications and source records attributed to W J Cooper.

12 recordsLinked to original sources
PubMed1996

Headspace analysis of some typical organic pollutants in drinking water using differential detectors: effects of columns and operational parameters.

Environmental analytical procedures in the United States are largely based on Environmental Protection Agency (EPA) methods. Different procedures have been adopted by the European Union (EU). In the United States, the determination of volatile organic compounds in drinking water employs purge and trap sampling followed by gas chromatography with photoionization and electrolytic conductivity detection. European analysts perform an "equivalent" priority pollutant analysis using static headspace injections and electron-capture detection. Some of the compounds included on the EPA list (1) do not appear on the EU lists (2) and vice versa. A distinctive difference is the use of megabore (greater than 0.45-mm i.d.) capillary columns in the EPA methods. European analysts are reluctant to adopt these columns in their methodologies. In this work, several open-tubular column dimensions are investigated and optimized with particular attention given to problems encountered when columns are interfaced to purge and trap or static headspace analyzers. Also, EPA and EU priority pollutant methods are contrasted according to the method of detection.

Chromatography, Gas↗
PubMed1986

Denitrification in marl and peat sediments in the Florida everglades.

The potential for denitrification in marl and peat sediments in the Shark River Slough in the Everglades National Park was determined by the acetylene blockage assay. The influence of nitrate concentration on denitrification rate and N(2)O yield from added nitrate was examined. The effects of added glucose and phosphate and of temperature on the denitrification potential were determined. The sediments readily denitrified added nitrate. N(2)O was released from the sediments both with and without added acetylene. The marl sediments had higher rates than the peat on every date sampled. Denitrification was nitrate limited; however, the yields of N(2)O amounted to only 10 to 34% of the added nitrate when 100 muM nitrate was added. On the basis of measured increases in ammonium concentration, it appears that the balance of added nitrate may be converted to ammonium in the marl sediment. The sediment temperature at the time of sampling greatly influenced the denitrification potential (15-fold rate change) at the marl site, indicating that either the number or the specific activity of the denitrifiers changed in response to temperature fluctuations (9 to 25 degrees C) in the sediment. It is apparent from this study that denitrification in Everglades sediments is not an effective means of removing excess nitrogen which may be introduced as nitrate into the ecosystem with supply water from the South Florida watershed and that sporadic addition of nitrate-rich water may lead to nitrous oxide release from these wetlands.

Journal Article↗
PubMed1983

Kaiser-Permanente's Medicare Plus Project: a successful Medicare prospective payment demonstration.

The Medicare Plus project of the Oregon Region Kaiser-Permanente Medical Care Program was designed as a model for prospective payment to increase Health Maintenance Organization (HMO) participation in the Medicare program. The project demonstrated that it is possible to design a prospective payment system that costs the Medicare program less than services purchased in the community from fee-for-service providers; would provide appropriate payment to the HMO; and in addition, creates a "savings" to return to beneficiaries in the form of comprehensive benefits to motivate them to enroll in the HMO. Medicare Plus was highly successful in recruiting 5,500 new and 1,800 conversion members into the demonstration, through use of a media campaign, a recruitment brochure, and a telephone information center. Members recruited were a representative age and geographic cross section of the senior citizen population in the Portland, Oregon metropolitan area. Utilization of inpatient services by Medicare Plus members in the first full year (1981) was 1679 days per thousand members and decreased to 1607 in the second full year (1982). New members made an average of eight visits per year to ambulatory care facilities.

Aged↗