Rakesh C. Saxena

Derivatizing L-histidine to develop a novel additive for a polyol-based biolubricant

Two novel histidine Schiff base esters, HSE-A and HSE-B, were synthesized using a two-step reaction. The synthesized compounds were characterized using carbon, hydrogen, nitrogen analysis, Fourier-transform infrared and nuclear magnetic resonance spectroscopy. The antioxidant and anticorrosion properties of these additives were assessed using the universal oxidation test (IP-306) and standard accelerated corrosion testing procedure, which revealed that both additives have good antioxidant and anticorrosion properties. Lubricity test carried out in a four-ball test machine indicated that both additives could reduce wear when compared with the pure polyol base oil. Overall, the HSE-A additive is more effective than the HSE-B additive as an antioxidant/antiwear/anticorrosion biolubricant additive.

An Introduction to Microalgae: Diversity and Significance

Abstract Algae, identified as a heterogeneous group of microorganisms, range from the microscopic blue-green algae (gram-negative bacteria) to large, complex seaweeds, measuring up to a few meters. Based on growth size, algae are classified into two different categories, namely micro- and macroalgae. Small aquatic photosynthetic plants that require the aid of a microscope to be seen are classified as microalgae. This chapter presents the diversity of microalgae with its biogeography and terrestrial details. Lipid, protein, and carbohydrate storage mechanisms of microalgae are discussed, along with possibilities of genetic engineering for enhancing these capabilities and photosynthesis. The potential for using microalgae for the production of pharmaceutical, food, and fuel products is also covered, including the scope and limitations of commercialization.

First evidence of denitrification vis-à-vis monsoon in the Arabian Sea since Late Miocene

In the Arabian Sea, South Asian monsoon (SAM)-induced high surface water productivity coupled with poor ventilation of intermediate water results in strong denitrification within the oxygen minimum zone (OMZ). Despite the significance of denitrification in the Arabian Sea, we have no long-term record of its evolution spanning the past several million years. Here, we present the first record of denitrification evolution since Late Miocene (~10.2 Ma) in the Eastern Arabian Sea, where the SAM generates moderate surface water productivity, based on the samples retrieved during the International Ocean Discovery Program (IODP) Expedition 355. We find that (i) the SAM was persistently weaker from ~10.2 to 3.1 Ma; it did not intensify at ~8 Ma in contrast to a few previous studies, (ii) on tectonic timescale, both the SAM and the East Asian Monsoon (EAM) varied synchronously, (iii) the first evidence of denitrification and productivity/SAM intensification was at ~3.2–2.8 Ma that coincided with Mid-Pliocene Warm Period (MPWP), and (iv) the modern strength of the OMZ where denitrification is a permanent feature was attained at ~1.0 Ma.