Air emissions from gas-fired combustion devices such as boilers, process heaters, gas turbines and stationary reciprocating engines contain hazardous air pollutants (HAPs) subjected to consideration under the federal clean air act (CAA). This work presents a recently completed major research project to develop an understanding of HAP emissions from gas-fired boilers and process heaters and new HAP emission factors based on field emission tests of gas-fired external combustion devices used in the petroleum industry. The effect of combustion system design and operating parameters on HAP emissions determined by both field and research tests are discussed. Data from field tests of gas-fired petroleum industry boilers and heaters generally show very low emission levels of organic HAPs. A comparison of the emission data for boilers and process heaters, including units with and without various forms of NOx emission controls, showed no significant difference in organic HAP emission characteristics due to process or burner design. This conclusion is also supported by the results of research tests with different burner designs. Based on field tests of units fired with natural gas and various petroleum industry process gases and research tests in which gas composition was intentionally varied, organic HAP emissions were not determined to be significantly affected by the gas composition. Research data indicate that elevated organic HAP emission levels are found only under extreme operating conditions (starved air or high excess air combustion) associated with poor combustion.

Journal Article↗

PubMedDate not supplied

Myenteric plexus in spastic motility disorders.

Previous studies have often revealed an absence or reduction of ganglia in Auerbach's plexus in many patients with achalasia, which has been postulated to be related to the elevated lower esophageal sphincter pressure in these patients. We undertook a prospective study to determine whether microscopic changes were present in the myenteric plexus of patients with hypertensive lower esophageal sphincter, nutcracker esophagus, and diffuse esophageal spasm and if there was a correlation with lower esophageal sphincter pressure. Nine patients (3 men and 6 women; ages 49 to 72 years, mean 58 years) underwent a laparoscopic esophagomyotomy with fundoplication for symptomatic spastic motility disorder. A 10 mm x 5 mm segment of esophageal muscle was removed from the border of the myotomy incision, fixed in formalin, and examined under light microscopy for the presence or absence of ganglia and inflammation. Correlation between the presence of ganglia and lower esophageal sphincter pressure was tested by Pearson's bivariant correlation. Manometry revealed three patients with hypertensive lower esophageal sphincter, four patients with nutcracker esophagus, and two patients with diffuse esophageal spasm. All three patients with a hypertensive lower esophageal sphincter revealed an absence of ganglia, whereas the six patients with nutcracker esophagus and diffuse esophageal spasm exhibited ganglia despite an elevated lower esophageal sphincter pressure in four. Hypertensive lower esophageal sphincter resembled achalasia in its absence of ganglia in Auerbach's plexus, whereas nutcracker esophagus and diffuse esophageal spasm exhibited ganglia. There was no significant correlation in our series between the presence of ganglia and an elevated lower esophageal sphincter pressure in spastic motility disorders.

Esophageal Motility Disorders↗

PubMedDate not supplied

False starts in translational control of gene expression.

Explore the source record for details and available documents.

Gene Expression Regulation↗

PubMedDate not supplied

Survey of health care coverage of high school football in southern California.

We surveyed 240 high schools about various aspects of the health care coverage of their football athletes. Approximately 70% of these schools had team physicians, and more than one third of these had more than 1 team physician. Seventy-two percent of high schools had physician coverage for scheduled games. Practices and scrimmages were not covered. Sixty-nine percent of the schools reported having an athletic trainer for home games. Basic equipment was often lacking. Recording and tracking of athletic injuries were inconsistent. An overall team approach for medical coverage was noted. Concern was raised about adequate physician or medical coverage with emphasis on greater input from the school administration, community hospitals, and physicians.

California↗

PubMedDate not supplied

A multistate outbreak of Salmonella enterica serotype Baildon associated with domestic raw tomatoes.

Salmonella enterica serotype Baildon, a rare serotype, was recovered from 86 persons in eight states; 87% of illnesses began during a 3-week period ending January 9, 1999. Raw restaurant-prepared tomatoes were implicated in multiple case-control studies. Contamination likely occurred on the farm or during packing; more effective disinfection and prevention strategies are needed.

Adolescent↗

PubMedDate not supplied

An unusual presentation of pigmented villonodular synovitis.

A case of multiple joint and tendon involvement by PVS seems not to have been preciously reported. In a 7-year-old girl there were other organ system problems usually not seen with PVS, and the entire complex may represent a more generalized disease process. The diffuse form of the disease was refractory to multiple attempts at surgical excision. The similarities between PVS and synovial hemangioma suggest that it is important to establish the diagnosis after the first operation.

Adolescent↗