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Biomedical subjects

S Sengupta

Publications and source records attributed to S Sengupta.

At least 253 records · Page 14Linked to original sources
PubMed1977

Annealing characteristics and nature of traps in A12O3 thermoluminescent phosphor.

Thermal annealing characteristics of the glow peaks from 200 to 650 degrees c in Al2O3 thermoluminescent (TL) phosphor have been studied. All the glow peaks show exponential decay and follow first-order kinetics. The trap depths and frequency factors for the glow peaks have been determined from their isothermal decay and from their initial rise. The trap depths, E, obtained for different glow peaks (peak temperature Tm) can be approximated by the relation E(eV)=Tm (K)/325 and the corresponding frequency factor, s, varies from 10(14) to 10(16) s-1. The measured values of E, s and Tm for the glow peaks are shown to be consistent with the equation for glow peak temperature. The annealing characteristics and actual high temperature irradiations show that the 250, 475 and 635 degree c peaks can be used for elevated temperature dosimetry up to 150, 300 and 440 degrees C respectively. It is suggested that surface defects related to Si impurity in Al2O3, propagated into the lattice on high temperature treatment close to the melting point, are responsible for the TL traps. The trapped charges responsible for TL are shown to be electrons by photostimulated thermoluminescence studies under the F centre excitation in this phosphor.

Aluminum↗
PubMed1976

Gamma dosimetry with Al2O3 thermoluminescent phosphor.

Preparation of thermoluminscence (TL) dosimetric grade A12O3 powder and pellets five times more sensitive than TLD-100 is described. Glow peaks at 50, 125, 250, 325, 475 and 625 degrees C with emission in the blue region have been observed; Si and Ti have been identified as the impurities responsible for TL in this phosphor. Studies of the TL growth rate with exposure showed that the 250 degrees c peak grew linearly up to 400 R and then at a supralinear rate of (exposure). The growth of the 475 degrees c peak was almost linear at a rate of (exposure) 1-05, while that for the 625 degrees C peak was sublinear at (exposure) 0-85. The 250 and 475 degrees peaks together show a linear response up to 40 000 R. The phosphor had no light sensitivity and is very well suited for gamma dosimetry as pellets or powder. Studies of sensitization and supralinearity, with sensitizing exposure, sensitizing anneal temperature and test gamma and alpha exposures are reported. Initially filled 625 degrees C TL related traps were found to be essential for sensitizaiton. Supralinearity and sensitization in Al2O3 phosphor could be consistently explained by the deep trap model.

Aluminum↗
PubMed1976

Needle biopsy of bone: a simplified technique.

By means of a slight modification of a commonly available needle, adequate amounts of bone for histopathology examination have been obtained from deep-seated bones, including vertebral bodies. Forty-one correct diagnoses were made in 51 consecutive cases in which the technique was used.

Adolescent↗
PubMed1976

Gangrene following intra-arterial injection of procaine penicillin.

Irreversible ischaemic gangrene of the upper limb developed in a one-year-old child after an unintentional intra-arterial injection of procaine penicillin. The hand needed amputation. Arterial embolization phenomenon along with intense vasospasm appears to have been responsible for this rare complication. Unintentional intra-arterial injection of penicillin intended for intra-muscular use may lead to disastrous consequences. Regional tissue necrosis has been described previously but ischaemia leading to gangrene of an extremity has not been reported. The following is a case report of a child who developed such a gangrene in his hand which had to be amputated.

Adolescent↗
PubMed1973

Stereoconfiguration of amino acids in peptides from a mycobacillin-synthesizing cell-free system.

The stereoconfiguration of amino acids, as determined by treatment with L-amino acid oxidase, d-amino acid oxidase and l-glutamate decarboxylase (containing l-aspartate decarboxylase activity), in the peptides from a mycobacillin-synthesizing cell-free system is identical with that of the growing mycobacillin peptide chaid if its synthesis starts from l-proline and is interrupted at various points by amino acid deprivation.

Amino Acid Oxidoreductases↗