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Biomedical subjects

D Mark

Publications and source records attributed to D Mark.

48 records · Page 3Linked to original sources
PubMed1985

A new static sampler for airborne total dust in workplaces.

This paper describes the development and laboratory testing of a new static dust sampler for airborne total dust in workplaces. Particular attention is paid to designing the sampling head and entry consistent with the concept of inspirability which in turn defines a biologically-relevant aspiration efficiency. The sampling head has a small cylindrical body and a transverse entry slot with thin protruding lips forming an integral part of a weighable capsule containing a 37 mm filter which collects all of the sampled dust (without introducing errors due to external particle blow-off or internal wall losses). A battery-powered sampling pump provides both air suction at 3 L/min and rigid mounting for the sampling head. The sampling head is rotated continuously through 360 degrees at approximately 1.5 rpm by a simple electric drive, connected to the stationary pump through a rotating seal. Wind tunnel testing of the instrument showed it to display an entry efficiency very close to the inspirability curve of Vincent and Armbruster (now recommended by the ACGIH Technical Committee on Air Sampling Procedures for defining inspirable particulate matter (IPM] for particles of aerodynamic diameter up to 90 micron and for windspeeds in the range of one to three m/sec.

Aerosols↗
PubMed1984

Shear flow characteristics of sodium hyaluronate. Relationship to performance in anterior segment surgery.

In this study, methods were developed for the in vitro evaluation of the surgical performance characteristics of viscoelastic fluids, such as sodium hyaluronate (Healon). Sodium hyaluronate exhibited superior surgical performance to chondroitin-6-sulfate. The superior performance of sodium hyaluronate resulted in part from its high viscosity, which is 20 times greater than that of chondroitin-6-sulfate at shear rates on the order of 10 s-1. The gel-like character of sodium hyaluronate as evidenced by the creep flow behavior, was greater than that of chondroitin-6-sulfate and was important for maintaining depth in the anterior chamber. It was shown that a threshold of 80 poise for the shear viscosity (at approximately 10 s-1 was needed for useful performance in surgery. It was also shown that 0.42 USP units of hyaluronidase per 1.0 mg sodium hyaluronate produces a 90% decrease in the shear viscosity (at approximately 10 s-1) within approximately 2 1/2 hours. Use of sodium hyaluronate in conjunction with hyaluronidase would allow sodium hyaluronate to remain highly viscous during surgery, but would gradually become less viscous to facilitate aqueous outflow after surgery.

Animals↗
PubMed1977

Sensory recording from the isolated cornea.

A technique of recording from single units of the isolated rat cornea is described. The corneal surface is stimulated by a jet of fluid, which allows continuously graded pressure and thermal or chemical stimuli to be applied at the same point. Some units respond to stimulation anywhere in a field of about one-third the corneal area, and others only to point stimulation.

Action Potentials↗
PubMedDate not supplied

Dietary supplement users: demographics, product use, and medical system interaction.

BACKGROUND: Dietary supplements-defined as vitamins and minerals, herbal products, tissue extracts, proteins and amino acids, and other products-are purchased to improve health and prevent disease. Little has been published, however, about the characteristics of either the products or the people who use them. METHODS: Consecutive customers visiting two health food stores during a 15-day period were interviewed by telephone. They were asked about their use of dietary supplements, demographics, and their use of the established health care system. RESULTS: Of the 194 customers contacted, 136 (70.1 percent) completed the survey. Respondents took a total of 805 supplements, most often to prevent a health problem (84.3 percent). Herbal products were most commonly used. Garlic, ginseng, and Ginkgo biloba were the herbs most frequently used. Fifty products were found to have previously reported toxicities, including vitamin A, which 9 customers were taking in megadoses. Most customers were white (94.1 percent), female (75.7 percent), had at least 1 year of college education (70.6 percent), had health insurance (95.6 percent), and had a regular physician (85.3 percent). CONCLUSION: Most of the dietary supplements consumed appear to be safe, but 50 of 805 had previously reported toxicities including megadoses of vitamin A. Garlic, ginseng, and Ginkgo biloba were the most commonly ingested herbs, and the medical literature supports their effectiveness for some conditions in humans. Customers of two health food stores had average to above-average education and took dietary supplements to stay healthy. They used the conventional health care system but did not typically consult their physician about dietary supplements. The pattern of use suggests that physicians might not be adequately addressing preventive and wellness issues in discussions with their patients. Furthermore, physicians might need to learn about dietary supplements so they can communicate with patients about them.

Adult↗