University of Calcutta

About: University of Calcutta is a education organization based out in Kolkata, India. It is known for research contribution in the topics: Population & Catalysis. The organization has 8900 authors who have published 19712 publications receiving 259067 citations. The organization is also known as: Calcutta University & CU.

Low-density polyethylene degradation by Pseudomonas sp. AKS2 biofilm

Abstract: Polyethylene materials are a serious environmental concern as their nondegradable nature allows them to persist in the environment. Recent studies have shown that polyethylene can be degraded by microbes at a very slow rate, whereby detectable changes are evident after several years. In the present study, we report the degradation of low-density polyethylene by Pseudomonas sp. AKS2. Unlike the previous reports, degradation by Pseudomonas sp. AKS2 is relatively fast as it can degrade 5 ± 1 % of the starting material in 45 days without prior oxidation. This degradation can be altered by agents that modulate hydrophobic interaction between polythene and the microbe. As mineral oil promotes hydrophobic interactions, it enhances bacterial attachment to the polymer surface. This enhanced attachment results in increased biofilm formation and enhanced polymer degradation. In contrast, Tween 80 reduces bacterial attachment to the polymer surface by lowering hydrophobic interactions and thereby reduces polymer degradation. Thus, this study establishes a correlation between hydrophobic interaction and polymer degradation and also relates the biofilm formation ability of bacteria to polymer degrading potential.

A theoretical review on electronic, magnetic and optical properties of silicene.

Abstract: Inspired by the success of graphene, various two dimensional (2D) structures in free standing (FS) (hypothetical) form and on different substrates have been proposed recently. Silicene, a silicon counterpart of graphene, is predicted to possess massless Dirac fermions and to exhibit an experimentally accessible quantum spin Hall effect. Since the effective spin-orbit interaction is quite significant compared to graphene, buckling in silicene opens a gap of 1.55 meV at the Dirac point. This band gap can be further tailored by applying in plane stress, an external electric field, chemical functionalization and defects. In this topical theoretical review, we would like to explore the electronic, magnetic and optical properties, including Raman spectroscopy of various important derivatives of monolayer and bilayer silicene (BLS) with different adatoms (doping). The magnetic properties can be tailored by chemical functionalization, such as hydrogenation and introducing vacancy into the pristine planar silicene. Apart from some universal features of optical absorption present in all these 2D materials, the study on reflectivity modulation with doping (Al and P) concentration in silicene has indicated the emergence of some strong peaks having the robust characteristic of a doped reflective surface for both polarizations of the electromagnetic (EM) field. Besides this, attempts will be made to understand the electronic properties of silicene from some simple tight-binding Hamiltonian. We also point out the importance of shape dependence and optical anisotropy properties in silicene nanodisks and establish that a zigzag trigonal possesses the maximum magnetic moment. We also suggest future directions to be explored to make the synthesis of silicene and its various derivatives viable for verification of theoretical predictions. Although this is a fairly new route, the results obtained so far from experimental and theoretical studies in understanding silicene have shown enough significant promising features to open a new direction in the silicon industry, silicon based nano-structures in spintronics and in opto-electronic devices.

Chronic arsenic toxicity: Studies in West Bengal, India

Abstract: Chronic arsenic toxicity (arsenicosis) as a result of drinking arsenic-contaminated groundwater is a major environmental health hazard throughout the world, including India. A lot of research on health effects, including genotoxic effect of chronic arsenic toxicity in humans, have been carried out in West Bengal during the last 2 decades. A review of literature including information available from West Bengal has been made to characterize the problem. Scientific journals, monographs, and proceedings of conferences with regard to human health effects, including genotoxicity, of chronic arsenic toxicity have been reviewed. Pigmentation and keratosis are the specific skin diseases characteristic of chronic arsenic toxicity. However, in West Bengal, it was found to produce various systemic manifestations, such as chronic lung disease, characterized by chronic bronchitis, chronic obstructive and/or restrictive pulmonary disease, and bronchiectasis; liver diseases, such as non cirrhotic portal fibrosis; polyneuropathy; peripheral vascular disease; hypertension; nonpitting edema of feet/hands; conjunctival congestion; weakness; and anemia. High concentrations of arsenic, greater than or equal to 200 μg/L, during pregnancy were found to be associated with a sixfold increased risk for stillbirth. Cancers of skin, lung, and urinary bladder are the important cancers associated with this toxicity. Of the various genotoxic effects of arsenic in humans, chromosomal aberration and increased frequency of micronuclei in different cell types have been found to be significant. Various probable mechanisms have been incriminated to cause DNA damage because of chronic arsenic toxicity. The results of the study in West Bengal suggest that deficiency in DNA repair capacity, perturbation of methylation of promoter region of p53 and p16 genes, and genomic methylation alteration may be involved in arsenic-induced disease manifestation in humans. P53 polymorphism has been found to be associated with increased occurrence of arsenic-induced keratosis. Of the various genes involved in the regulation of arsenic metabolism, single-nucleotide polymorphisms of purine nucleoside phosphorylase, in one study, showed increased occurrence of arsenicosis.

Enzyme activities and microbial biomass in coastal soils of India

Abstract: Soil salinity is a serious problem for agriculture in coastal regions, wherein salinity is temporal in nature. We studied the effect of salinity, in summer, monsoon and winter seasons, on microbial biomass carbon (MBC) and enzyme activities (EAs) of the salt-affected soils of the coastal region of the Bay of Bengal, Sundarbans, India. The average pH of soils collected from different sites, during different seasons varied from 4.8 to 7.8. The average organic C (OC) and total N (TN) content of the soils ranged between 5.2–14.1 and 0.6–1.4 g kg −1 , respectively. The electrical conductivity of the saturation extract (ECe) of soils, averaged over season, varied from 2.2 to 16.3 dSm −1 . The ECe of the soils increased five fold during the summer season (13.8 dSm −1 ) than the monsoon season (2.7 dSm −1 ). The major cation and anion detected were Na + and Cl − , respectively. Seasonality exerted considerable effects on MBC and soil EAs, with the lowest values recorded during the summer season. The activities of β -glucosidase, urease, acid phosphatase and alkaline phosphatase were similar during the winter and monsoon season. The dehydrogenase activity of soils was higher in monsoon than in winter. Average MBC, dehydrogenase, β -glucosidase, urease, acid phosphatase and alkaline phosphatase activities of the saline soils ranged from 125 to 346 mg kg −1 oven dry soil, 6–9.9 mg triphenyl formazan (TPF) kg −1 oven dry soil h −1 , 18–53 mg p -nitro phenol (PNP) kg −1 oven dry soil h −1 , 38–86 mg urea hydrolyzed kg −1 oven dry soil h −1 , 213–584 mg PNP kg −1 oven dry soil h −1 and 176–362 mg PNP g −1 oven dry soil h −1 , respectively. The same for the non-saline soils were 274–446 mg kg −1 oven dry soil, 8.8–14.4 mg TPF kg −1 oven dry soil h −1 , 41–80 mg PNP kg −1 oven dry soil h −1 , 89–134 mg urea hydrolyzed kg −1 oven dry soil h −1 , 219–287 mg PNP kg −1 oven dry soil h −1 and 407–417 mg PNP kg −1 oven dry soil h −1 , respectively. About 48%, 82%, 48%, 63%, 40% and 48% variation in MBC, dehydrogenase activity, β -glucosidase activity, urease activity, acid phosphatase activity and alkaline phosphatase activity, respectively, could be explained by the variation in ECe of saline soils. Suppression of EAs of the coastal soils during summer due to salinity rise is of immense agronomic significance and needs suitable interventions for sustainable crop production.

High-Performance Supercapacitor Electrode Based on Cobalt Oxide-Manganese Dioxide-Nickel Oxide Ternary 1D Hybrid Nanotubes.

Abstract: We report a facile method to design Co3O4–MnO2–NiO ternary hybrid 1D nanotube arrays for their application as active material for high-performance supercapacitor electrodes. This as-prepared novel supercapacitor electrode can store charge as high as ∼2020 C/g (equivalent specific capacitance ∼2525 F/g) for a potential window of 0.8 V and has long cycle stability (nearly 80% specific capacitance retains after successive 5700 charge/discharge cycles), significantly high Coulombic efficiency, and fast response time (∼0.17s). The remarkable electrochemical performance of this unique electrode material is the outcome of its enormous reaction platform provided by its special nanostructure morphology and conglomeration of the electrochemical properties of three highly redox active materials in a single unit.