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SK Ghosh

Publications and source records attributed to SK Ghosh.

At least 19 recordsLinked to original sources
PubMed2000

Can cosmic strangelets reach the earth?

The mechanism for the propagation of strangelets with low baryon number through the atmosphere of the Earth has been explored. It has been shown that, under suitable initial conditions, such strangelets may indeed reach depths near mountain altitudes with mass numbers and charges close to the observed values in cosmic ray experiments.

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PubMed2000

Synthesis and reactions of a stable o-quinoid 10-pi-electron system, Furo

Methyl 4,6-dichloro-3-(diethylamino)furo[3, 4-c]pyridine-1-carboxylate (6), an intermediate in the Hamaguchi-Ibata reaction involving the Rh(II)-catalyzed intramolecular reaction of a diazo group with the carbonyl of an adjacent amido group, has been isolated and characterized. PM3 calculations reveal the heat of formation (DeltaH(f)) of this remarkably stable molecule to be -77.7 kcal/mol. Compound 6 undergoes a facile Diels-Alder cycloaddition with a variety of dienophiles to give polysubstituted isoquinoline derivatives via ring opening of initially formed cycloadducts. In each case the cycloaddition proceeds with high regioselectivity, with the electron-withdrawing group located ortho to the amino group. The most favorable FMO interaction is between the HOMO of the azaisobenzofuran 6 and the LUMO of the dienophile. The atomic coefficient at the ester carbon of the azaisobenzofuran 6 is larger than the amino center, and this nicely accommodates the observed regioselectivity.

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PubMed2000

Cytogenetic toxicity of methotrexate in mouse bone marrow.

Methotrexate (MTX), a widely used anticancer drug, was tested for its cytogenetic toxicity in mouse bone marrow after a single intraperitoneal treatment with three different doses i.e. at the rate of 2, 10 and 20 mg/kg b.w. of mice. The end points selected were chromosomal aberrations and mitotic index study at 24-h post-treatment and micronucleus (MN) test at 30-h post-treatment. The induction of statistically significant number of chromosomal aberrations, percentage of aberrant metaphases and highly significant number of MN per thousand polychromatic erythrocytes by all the doses of MTX indicated it as highly clastogenic. MTX was found more clastogenic in male mice than the females and the intermediate dose tested (10 mg/kg) was found more effective than the other doses. In mitotic index study, none of the doses of MTX inhibited cell proliferation during the first post-treated cell cycle. The results were compared with the earlier reports on the clastogenicity and cell proliferation inhibition of MTX only after multiple treatments. The possible mechanism of the cytogenetic effects of MTX has been discussed.

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