Biomedical subjects

NN Das

Publications and source records attributed to NN Das.

5 recordsLinked to original sources

PubMed1998

Studies on Indian Ocean Manganese Nodules

The oxidation of thiols to corresponding disulfides by Indian Ocean ferromanganese nodules has been studied under varying experimental conditions. More than 90% conversion of thiols (2.5 x 10(-3) mol) was achieved at 35°C using 0.1 g nodules. The oxides of Mn, Fe, Ca, Mg, and Al and surface oxygen in the nodules are most likely responsible for the oxidation of thiols. Under identical conditions the oxidative conversion of thiols decreases in the order 1-dodecanethiol < 1-hexanethiol < 1,4-butanedithiol < alpha-toluenethiol. Copyright 1998 Academic Press. Copyright 1998Academic Press

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PubMed1997

Studies on Indian Ocean Manganese Nodules

A series of strontium-lanthanum oxide mixed manganese nodules were prepared and characterized by X-ray diffraction, nitrogen adsorption-desorption, electrical conductivity, and surface excess oxygen. X-ray diffraction patterns confirm the formation of perovskite-type oxides at low strontium content (x </= 0.5, in La1-xSrxMO3, where M denotes the transition metal present in nodules), whereas at 0.6 </= x </= 0.8, La2O3 and SrO are detected in addition to the perovskite-type oxides. The catalytic activities for hydrogen peroxide decomposition and carbon monoxide oxidation increase with an increase in Sr substitution for La, attain a maximum at x = 0.4, and then decrease with further increase in Sr. The activities have been correlated with various physicochemical properties.

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PubMed1997

Studies on Indian Ocean Manganese Nodules

Adsorption of aqueous selenite (SeO32-) on Indian Ocean manganese nodules was studied as a function of time, temperature, pH, and concentrations of adsorbate and adsorbent in acetic acid-sodium acetate buffer medium. Analysis of adsorption data supports a heterogeneous nature for the surface of manganese nodules. The adsorption capacity of various manganese nodules for selenite was correlated with their chemical composition and surface properties.

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PubMed1997

Studies on Ferric Oxide Hydroxides

Adsorption of selenite (SeO2-3) on different polymorphic forms of iron oxyhydroxides and amorphous ferrihydrite was studied as a function of time, temperature, pH, and concentration of adsorbate(s) and adsorbent(s). Analysis of adsorption data indicates that the surfaces of all the forms of oxyhydroxides and ferrihydrite are heterogeneous in nature and that adsorption fits into a heterogeneous site binding model. The adsorption capacity of oxyhydroxides for SeO2-3 follows the order beta-FeOOH < alpha-FeOOH < gamma-FeOOH < delta-FeOOH < ferrihydrite.

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PubMed1996

Studies on Indian Ocean Manganese Nodules

A series of rare earth oxide mixed manganese nodules (perovskite type mixed oxides) have been prepared by coprecipitation method followed by calcination at 900°C and characterized by different techniques. The effect of rare earth ions on the surface, textural and catalytic activity for the oxidation of CO, and decomposition of H2O2 have been discussed. The activity for CO oxidation followed an order: Pr >/= La > Nd > Yb > Dy > Tb > Sm > Tm > Gd > Eu > Ce.

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