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Biomedical subjects

S Jayaraman

Publications and source records attributed to S Jayaraman.

At least 127 records · Page 7Linked to original sources
PubMed1976

An estimate of the 60Co gamma attenuation in the small phantom enployed in the definition of tissue air ratio.

Tissue air ratio definition employs a concept of dose at the centre of a small mass of tissues that is suspended in air and is just large enough to give electronic equilibrium at its own centre. When the dose at the centre of the said small mass of tissue is to be derived from a knowledge of exposure in free air at the same point, the attenuation in the small mass of tissue should be taken into account. This attenuation for 1250 keV photons has been evaluated through a theroretical model and the attenuation factor is estimated to be 0.975.

Air↗
PubMed1976

A semi-empirical formula for approximate estimation of the fall-off of intensity in the penumbra region of 60co teletherapy beam.

The nature of the observed fall-off of intensity across the teletherapy beams for two different 60Co therapy units has been studied. The fall-offs for various field sizes have been compared and an empirical function derived to represent the fall-off. This function is of trigonometric tan inverse form and makes use of only one parameter. The value of this parameter is directly related to the geometrical penumbra width, which can be calculated from the source diameter, the source-to-diaphragm distance and the source-to-skin distance.

Cobalt Radioisotopes↗
PubMed1975

The estimation of N-nitrosamines in tropical regions by reversed-phase paper and thin-layer chromatography.

A simple and convenient procedure based on reversed-phase paper and thin-layer chromatography is reported for the detection and estimation of N-nitrosamines in food products, particularly cured meat. The method can easily be applied in tropical regions when plenty of sunshine is available. It is particularly useful in food-testing laboratories where sophisticated analysical instruments such as the gas chromatograph, mass spectrometer, etc., are not available. By this procedure, it is possible to detect up to 10 mug and to estimated up to 75-mug (reversed phase) and 50-mug (thin layer) amounts of N-nitrosamines.

Chromatography, Paper↗
PubMed1975

Effect of prostaglandin F2 alpha and hypertonic saline on the placental function during midtrimester abortion.

Changes in placental function during the induction of midtrimester abortion by prostaglandin F2 alpha and hypertonic saline were investigated. Serial estimations of human placental lactogen (HPL) and cystine aminopeptidase (CAP) were carried out in 17 subjects. There was a significant (P smaller than 0.01) reduction in the plasma CAP and HPL levels 4 hours after PGF2 alpha administration. In the case of hypertonic saline abortions only HPL levels showed a reduction at 8 and 12 hours after induction.

Abortion, Induced↗
PubMed1975

Chloramphenicol metabolism in children with protein-calorie malnutrition.

The plasma levels and urinary excretion of chloramphenicol was studied in ten malnourished children and four normal children after oral administration of a single dose of 25 mg/kg body weight. Plasma peak levels were achieved 2-4 hours later and were 1.5 or 2 times higher in malnourished children compared to the normal. They also took much longer to clear the drug from the plasma, 30 hours or more in malnourished children compared with 12 hours in the normal. These observations point to a slower rate of biotransformation in the liver. The excretion pattern of the drug and its metabolite lends support to this hypothesis. 75-85% of the drug excreted was in the form of conjugated fraction in the normal while only 35-55% was conjugated in malnourished children. In two children the liver biopsy tissue was subjected to assay of bilirubin-UDP transferase and low levels were detected. This observation also points to an alteration in the rate of biosynthesis of chloramphenicol.

Bilirubin↗
PubMed1975

Skin dose with cones and diaphragms in 137Cs teletherapy - a study using lithium borate thermoluminescent dosimeters.

Beam definition in 137Cs teletherapy is done either by use of cones for specified SSDs or by means of adjustable diaphragms. Using lithium borate thermoluminescent dosimeters, the skin dose was studied for conditions of the bare cone without any electron filter, the cone with an affixed perspex cup for cutting off the electrons, the cone with an affixed copper plate filter at its face. It was observed that of the above three arrangements, the case employing the copper filter gave the minimum skin dose. Similar skin dose measurements made for a diaphragm type collimator are discussed in comparison with the values for cones.

Borates↗