Biomedical subjects

J P Ring

Publications and source records attributed to J P Ring.

4 recordsLinked to original sources

PubMed1999

Benchmarking radiation protection programs.

Results are presented of a modest benchmarking project with eight institutions as part of a program review. Four of the institutions had programs with both research and clinical components. Metrics were derived from the data acquired. They included Registered Users per total Technical Staff (mean 284, SD 42%); Principal Investigators per Senior IP staff (mean 68.7, SD 49.6%); and Principal Investigators per HP staff (mean 44.7, SD 34.4%). Reasons for the differences among institutions were identified. The benchmarking exercise was an effective tool in providing guidance in setting staffing levels.

Benchmarking↗

PubMed1997

Carbon cartridge standards for 125I and suggested applications.

Carbon cartridge standards were prepared to assess the activity of 125I incident on, and adsorbed in, cartridge samples during air sampling. Each cartridge standard consisted of an 125I-spiked filter paper at a known depth, ranging from 0 to 19 mm, embedded in approximately 34 g of 20-30 mesh activated carbon contained within a 6.35 cm diameter by 2.22 cm deep metal cartridge with screened openings. The total counting efficiency values range from 17.8 to 20.8% for cartridges counted at 3.2 mm from a thin-crystal NaI(Tl) detector. The standards were analyzed using a front/back counting technique, and fitting functions were developed relating the front/back net counts ratio and counting efficiency to the 125I depth of burial. A method for determining sample activity that accounts for exponential radioiodine loading in cartridge samples is compared to a less complicated technique that assumes all the radioiodine is located at an equivalent depth of burial that is based on the sample front/back net counts ratio. In addition, methods are presented for determining airborne 125I activity for constant and variable concentrations. Variable concentrations are assumed to occur in a fume hood duct by one or more bulk releases as a result of iodinations that are performed during a given sampling interval. The two methods are shown to have maximum relative deviations ranging from -16 to +16%.

Air Pollutants, Radioactive↗

PubMed1996

Environmental monitoring for a low-level radioactive waste management facility: incinerator operations.

An environmental monitoring program has been developed for Harvard University, Southborough campus, to assess the local environmental concentrations of radionuclides released in incinerator effluents. The campus is host to the University's low-level radioactive waste management facility, which consists of 6,000 drum capacity decay-storage buildings; a 250 drum capacity decay-storage freezer; and a controlled-air incinerator. Developmental considerations were based on the characteristics and use of the incinerator, which has a capacity of 8 tons per day and is operated 5% of the time for the volume reduction of Type 0 and Type 4 wastes contaminated with a variety of radionuclides used in biomedical research-some in microsphere form. Monitoring was established for air, leafy vegetation, leaf-litter, and surface soil media. Field sampling was optimized regarding location and time based on the action of atmospheric, terrestrial, and biotic transport mechanisms. Preliminary results indicate transient concentrations of 3H and 125I in vegetation directly exposed to the dispersing plume. Measurable particulate depositions have not been observed.

Environmental Monitoring↗

PubMed1986

Plasma oxytocin and oxytocin neurone activity during delivery in rabbits.

The extracellular electrical activity of magnocellular neurones was recorded from unanaesthetized, unrestrained rabbits in birth and the post partum suckling period. The activity of oxytocin neurones was differentiated from that of vasopressin cells on the basis of their stereotyped activity in suckling. Oxytocin neurones showed five to fourteen discrete bursts of accelerated discharge in parturition. Each burst lasted 2-22 s and represented a 3-100-fold increase in the rate of firing, compared with pre-partum values, and was followed 10-34 s later by delivery. After parturition, the spontaneous activity of these neurones returned to pre-partum rates of firing. Vasopressin neurones did not show any bursts of discharge in delivery. There was a significant fall in the discharge frequency compared with pre-partum levels (P less than 0.05: Student's t test) and a significant (P less than 0.01) lengthening of the modal interspike interval. Serial blood samples were obtained during parturition in ten rabbits. Simultaneous recordings of magnocellular neurones activity and plasma oxytocin measurements were made in four of these experiments. Plasma oxytocin profiles were related to the observed events of parturition. Frequent blood samples (0.2-0.3 ml every 10-15 s) were taken throughout delivery and plasma oxytocin measured by sensitive radioimmunoassay in unextracted plasma (lower limit sensitivity of assay 5 pg ml-1). Before birth, plasma oxytocin was 53 +/- 12 pg ml-1 (mean +/- S.E. of mean) and rose to 2846 +/- 326 pg ml-1 within 40-120 s of the onset of the expulsive phase of delivery. Peak concentrations of oxytocin were coincident with delivery of the first or second fetus. No sign of pulsatile release of oxytocin was demonstrated in the profiles but significantly (P less than 0.001) greater variance in oxytocin titres was found during birth compared with pre-partum values which is suggestive of pulsatile release. There was a straight line relationship between peak oxytocin concentrations in the plasma and the speed of delivery, implying that oxytocin facilitates as well as maintains labour in the rabbit.

Action Potentials↗