Sandip Saha

Influence of Zn- and Ga-doping on the conversion of ethanol to hydrocarbons over ZSM-5

The influence of incorporating Zn and Ga in ZSM-5 on the catalytic transformation of ethanol into hydrocarbons has been investigated. Under the conditions of this study, considerable amount of hydrocarbons boiling above 423 K are produced over the catalysts. The incorporation of Zn and Ga in ZSM-5 increases its life considerably apart from increasing the yield of the liquid products. Further, the Zn- and Ga-catalysts produce more aromatics and less olefins.

Chromotropism of Cr(salen) moiety in zeolite matrix: synthesis, characterization and catalytic activity study of Cr(salen)-NaY hybrid catalyst

Abstract The [Cr(salen)] + [salenH 2 = N , N ′-bis(salicylaldehyde)-ethylenediimine] complex moiety is immobilized in NaY matrix to obtain a new hybrid catalytic system. The resulting yellow colored zeolite immobilized Cr(salen) catalyst on washing with CH 3 OH and H 2 O turns to light grey. The spectroscopic measurements showed that the interaction between axially coordinated H 2 O and Cr(III) in [Cr(salen)(H 2 O) 2 ] + moiety becomes weaker on the entrapment of the complex moiety in Y zeolite supercage. A good catalytic performance of the newly prepared hybrid catalyst was observed in epoxidation reaction of norbornene and styrene.

The oldest turritelline gastropods: from the Oxfordian (Upper Jurassic) of Kutch, India

Abstract. Turritellid gastropods are important components of many Cretaceous—Recent fossil marine faunas worldwide. Their shell is morphologically simple, making homoplasy widespread and phylogenetic analysis difficult, but fossil and living species can be recognized based on shell characters. For many decades, it has been the consensus that the oldest definite representatives of Turritellidae are from the Lower Cretaceous, and that pre-Cretaceous forms are homeomorphs. Some morphological characters of the present turritelline species resemble those of mathildoids, but many diagnostic characters clearly separate these two groups. We here describe and/or redescribe—based on examination of more than 2600 near complete specimens—four species from the Upper Jurassic Dhosa Oolite Member of the Chari Formation in Kutch, western India, and demonstrate that they are members of Turritellidae, subfamily Turritellinae, on the basis of diagnostic characters including apical sculptural ontogeny (obtained from SEM study), spiral sculpture, and growth line patterns. The four species are in order of abundance, Turritella jadavpuriensis Mitra and Ghosh, 1979; Turritella amitava new species; Turritella jhuraensis Mitra and Ghosh, 1979, and Turritella dhosaensis new species. The turritelline assemblages occur only on the northeastern flank of the Jhura dome (23°24′47.57″N, 69°36′09.26″E). Age of the Dhosa Oolite has recently been confirmed based on multiple ammonite species. All these points indicate that these fossils are the oldest record of the family Turritellidae—by almost 30 million years—in the world.

Predation on Recent Terebrid Gastropods from the Indian Subcontinent and a Spatiotemporal Reappraisal Based on a Revised Global Database

ABSTRACT Predator-prey interaction, especially drilling and shell-breaking predation pressure, caused significant evolutionary changes within these predator-prey communities. Although temporal trends are well understood in prey assemblages, studies to trace such changes within taxonspecific clades up to Recent times have been rare. Here, we studied both the drilling and shell-breaking predation on Recent terebrid gastropods from the Indian subcontinent and compared the results with a newly updated, global database. The major part of our data came from a large collection reposited in the archive of the Zoological Survey of India in Kolkata for more than 100 years. Detailed analyses of this study based on a newly raised, global database revealed the following findings: (1) Drilling frequency (DF) of Indian terebrids was low, but consistent with the DF of only available but limited data provided by Vermeij et al. (1980). In comparison, peeling frequency (PF) in Indian terebrids appeared to be highest in the world; (2) DF showed latitudinal variation, that is, higher incidence of drilling occurred in higher latitudes; no such pattern emerged from the PF data; (3) drillholes were site-stereotyped, which suggested that Recent naticid drillers were escalated; (4) shell ornaments failed to protect against durophagy; (5) shell shape and thickness had different impact against different modes of predation. While slender and thicker shells were almost immune to drilling predation, no such relation existed for peeling predation; (6) on the other hand, body size appears to have evolved as anti-predatory traits in Recent terebrids. Larger species had low DF and high PF values; (7) temporally, DF showed fluctuating pattern, with modern values showing declining trend. This was perhaps due to increase in body size and behavioural change of the terebrid gastropods. Unfortunately, no peeling frequency data for this clade was available from the fossil record.