Rahul Nigam

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Laboratory culture experiments were carried out to understand the response of benthic foraminifer Rosalina leei to gradual as well as sudden addition of heavy metal mercury into the media. When mercury was added suddenly, specimens did not show any change in morphology during the initial 40 days. However, later on, out of all the specimens subjected to(More)
In order to develop a viable foraminiferal proxy for heavy metal pollutants, juvenile specimens of Rosalina leei were subjected to different mercury concentrations (0-180 ng/l). Initially considerable growth was observed in specimens kept in saline water having a mercury concentration up to 100 ng/l. But with the gradual increase in concentration of mercury(More)
In view of the extensive use of foraminifers for the pollution monitoring especially their unmatched utility in deciphering the temporal variation in the type and concentration of pollutants at a given location, the literature dealing with the application of foraminifers for pollution studies has been reviewed. The pollution monitoring through foraminifers(More)
We study general two-body decays of primitive and non-primitive 1 4-BPS dyons in four-dimensional type IIB string compactifications. We find a " master equation " for marginal stability that generalises the curve found by Sen for 1 2-BPS decay, and analyse this equation in a variety of cases including decays to 1 4-BPS products. For 1 2-BPS decays, an(More)
We obtain the complete set of constraints on the moduli of N = 4 su-perstring compactifications that permit " rare " marginal decays of 1 4-BPS dyons to take place. The constraints are analysed in some special cases. The analysis extends in a straightforward way to multi-particle decays. We discuss the possible relation between general multi-particle decays(More)
We examine the duality between type 0 noncritical strings and topological B-model strings, with special emphasis on the flux dependence. The former theory is known to exhibit holomorphic factorisation upto a subtle flux-dependent disc term. We give a precise definition of the B-model dual and propose that it includes both compact and noncompact B-branes.(More)
I dedicate this thesis to my parents. Acknowledgements It is a pleasure to thank the many people who made this thesis possible. It is difficult to overstate my gratitude to my Ph.D. supervisor, Sandip Trivedi. With his enthusiasm, his inspiration, and his great efforts to explain things clearly and simply, he helped to make physics fun for me. Throughout my(More)