Search PubMed⌕ Search

Biomedical subjects

J Tibbetts

Publications and source records attributed to J Tibbetts.

16 recordsLinked to original sources
PubMed2000

Water world 2000.

Today, at least one-fifth of all people worldwide lack access to safe drinking water, a problem that will almost certainly worsen as the earth's population grows. Although the vast majority of industrial discharges into waterways are regulated and treated, and most cities and towns effectively monitor and treat their sewage for chemical contaminants, problems such as arsenic contamination and dangerous microorganisms still trouble public water supplies in wealthy nations. In developing countries, most cities discharge 80-90% of their untreated sewage directly into rivers and streams, which are used for drinking, bathing, and washing. This lack of sewage treatment has allowed dangerous microorganisms to spread, posing one of the greatest threats to human health in the developing world: waterborne diseases caused by deadly microbes in water. Contamination isn't the only problem: in many areas of the world, drinkable water is a scarce resource available to many only at high cost, when it is available at all.

Developed Countries↗
PubMed2000

Making amends: ecological restoration in the United States.

Restoring an ecosystem to its preindustrial state can be very difficult or impossible. The great majority of restoration projects put a high priority on the biological requirements of endangered species, often drawing ecologists into volatile political controversies over the rights of humans versus those of wildlife. Meanwhile, resource managers struggle to gain enough information about historical ecosystems to reconstruct them successfully. There are often difficult judgment calls when scientists try to redesign a system that has been degraded over many generations, and it's often confusing to decide which period of history to restore an ecosystem to. In addition, modern industrialized society continues to place extensive demands upon already-stressed, degraded ecosystems. Restoration projects in the Florida Everglades, Pacific Northwest riverine systems, and forests in the Southeast illustrate the challenges associated with ecological restoration.

Conservation of Natural Resources↗
PubMed1998

Time series forecasts of ambulance run volume.

To test the hypothesis that time series analysis can provide accurate predictions of future ambulance service run volume, a prospective stochastic time series modeling study was conducted at a community-based regional ambulance service. For all requests for ambulance transport during two sequential years, the time and date, total run time, and acuity code of the run were recorded in a computer database. Time series variables were formed for ambulance service runs per hour, total run time, and acuity. Prediction models were developed from one complete year's data (1994) and included four model types: raw observations, moving average, means with moving average smoothing, and autoregressive integrated moving average. Forecasts from each model were tested against observations from the first 24 weeks of the subsequent year (1995). Each model's adequacy was tested on residuals by autocorrelation functions, integrated periodograms, linear regression, and differences among the variances. A total of 68,433 patients were seen in 1994 and 32,783 in the first 24 weeks of 1995. Large periodic variations in run volume with time of day were found (P < .001). A model based on arithmetic means of each hour of the week with 3-point moving average smoothing yielded the most accurate forecasts and explained 54.3% of the variation observed in the 1995 test series (P < .001). Time series analysis can provide powerful, accurate short-range forecasts of future ambulance service run volume. Simpler, less expensive models performed best in this study.

Ambulances↗
PubMed1998

Toxic tides.

Explore the source record for details and available documents.

Animals↗
PubMed1997

Exotic invasion.

Explore the source record for details and available documents.

Animals↗
PubMed1996

Green houses.

Explore the source record for details and available documents.

Air Pollution, Indoor↗
PubMed1996

Ocean commotion.

Explore the source record for details and available documents.

Animals↗
PubMed1992

Effect of x-ray angulation on radiographic periodontal ligament space width.

The aim of this study was to set up a model for quantitating a change in radiographic PDL width on variation of x-ray angulation within anticipated clinical limits. Four incisor and 4 molar sites of 6 human skulls were radiographed at varying angulation. Horizontal angulation changes were made over a 12 degrees range, in 3 degrees increments. Vertical angulation change was in one 10 degrees increment. Baseline radiographs were taken with the x-ray beam perpendicular to a buccal tooth surface in a horizontal direction and perpendicular or 10 degrees off the perpendicular in a vertical direction. The radiographs were converted to digitized images and PDL width measurements made utilizing a mouse-driven computer program. The mean PDL width differences between all possible horizontal and vertical combinations (n = 45) were compared with the mean of those obtained from differences observed in PDL width measurements on replicate baseline radiographs. Mean PDL width differences for incisor locations were statistically different from the mean baseline PDL width difference; posterior PDL width difference showed no statistical variation from the mean baseline PDL width difference. For radiographs taken within the range expected under clinical conditions, a significant change in PDL width may be observed in incisor locations. Posterior sites may not exhibit this significant change due to the anatomy of the region which may reduce the clarity of the radiographic image.

Humans↗