Bidhannagar College

Salt Lake, India

Bidhannagar College

Salt Lake, India
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Saha A.,Visva Bharati University | Talukdar B.,Visva Bharati University | Chatterjee S.,Bidhannagar College
Physica A: Statistical Mechanics and its Applications | Year: 2017

We make use of a Hylleraas-type wave function to derive an exact analytical model to quantify correlation in two-electron atomic/ionic systems and subsequently employ it to examine the role of inter-electronic repulsion in affecting (i) the bare (uncorrelated) single-particle position- and momentum-space charge distributions and (ii) corresponding Shannon's information entropies. The results presented for the first five members in the helium iso-electronic sequence, on the one hand, correctly demonstrate the effect of correlation on bare charge distributions and, on the other hand, lead us to some important results for the correlated and uncorrelated values of the entropies. These include the limiting behavior of the correlated entropy sum (sum of position- and momentum-space entropies) and geometrical realization for the variation of information entropies as a function of Z. We suggest that, rather than the entropy sum, individual entropies should be regarded as better candidates for the measure of correlation. © 2017

Sengupta S.,Bidhannagar College | Ganguli S.,AIIST | Singh P.K.,The Biome | Singh P.K.,Bose Institute of India
Genomics Data | Year: 2017

This study reports the root endophytic microbial community profile in rice (Oryza sativa L.), the largest food crop of Asia, using 16S rRNA gene amplicon sequencing. Metagenome of OS01 and OS04 consisted of 11,17,900 sequences with 300 Mbp size and average 55.6% G + C content. Data of this study are available at NCBI Bioproject (PRJNA360379). The taxonomic analysis of 843 OTU's showed that the sequences belonged to four major phyla revealing dominance of Proteobacteria, Firmicutes, Cyanobacteria and Actinobacteria. Results reveal the dominance of Bacillus as major endophytic genera in rice roots, probably playing a key role in Nitrogen fixation. © 2017

Saha A.,Visva Bharati University | Talukdar B.,Visva Bharati University | Chatterjee S.,Bidhannagar College
European Journal of Physics | Year: 2017

With special attention to the role of information theory in physical sciences we present analytical results for the coordinate- and momentum-space Fisher information of some important one-dimensional quantum systems which differ in spacing of their energy levels. The studies envisaged allow us to relate the coordinate-space information (Ir) with the familiar energy levels of the quantum system. The corresponding momentum-space information (Ig) does not obey such a simple relationship with the energy spectrum. Our results for the product (Ir Ig) depend quadratically on the principal quantum number n and satisfy an appropriate uncertainty relation derived by Dehesa et al. © 2017 European Physical Society Printed in the UK.

We propose a variant of the multiconfiguration time-dependent Hartree (MCTDH) method within the framework of Hermite-distributed approximating functional (HDAF) method. The discretized Hamiltonian is a highly banded Toeplitz matrix which significantly reduces computational cost in terms of both storage and number of operations. The method proposed is employed to carry out the study of tunnelling dynamics of two coupled double well oscillators. We have calculated the orthogonality time τ, which is a measure of the time interval for an initial state to evolve into its orthogonal state. It is observed that the coupling has a significant effect on τ. © Indian Academy of Sciences.

Saha J.,Presidency University of India | Mukherjee S.,Bidhannagar College | Gupta K.,Presidency University of India | Gupta B.,Presidency University of India
Journal of Pharmacy Research | Year: 2013

Objective: Gallic acid, ellagic acid and quercetin are the important antioxidant compounds of Saraca asoca (Roxb.) de Wilde (Caesalpiniaceae). This report describes the determination of free radical scavenging activity in different plant parts (of S. asoca) by DPPH assay with correlation, and quantification of gallic acid, ellagic acid and quercetin in different plant parts by a simple, sensitive and validated HPTLC method. Methodology: Methanolic extracts of bark, leaf and flowers of S. asoca were investigated for their antioxidant potential with the aid of DPPH assay followed by HPTLC analysis for quantitative evaluation of antioxidants (gallic acid, ellagic acid, and quercetin) in different plant parts. Results: HPTLC analysis exhibited high amount of gallic acid and quercetin in flower (0.320% and 0.11% w/w respectively) and high amount of ellagic acid in bark (0.4805% w/w) which corresponds to low IC50 values of 6.83±0.07μg/ml and 6.6±0.10μg/ml respectively, indicating the remarkable antioxidant activity of these two plant parts whereas moderate amount of gallic acid (0.164 %w/w) and very low amount of quercetin (0.0445% w/w) and ellagic acid (0.04% w/w) correlate high IC50 value of 28.6±0.62μg/ml representing its poor antioxidant potential. Conclusion: Consumption of bark and flower of S. asoca could be beneficial by virtue of its high antioxidant activity. The flower and bark may be considered as a source of gallic acid and ellagic acid respectively. The presence of moderate amount of gallic acid in leaf can be an alternative source. © 2013 JPR Solutions.

Pyne P.,Bose Institute of India | Alam M.,Bose Institute of India | Alam M.,Bidhannagar College | Ghosh W.,Bose Institute of India
Microbiological Research | Year: 2017

Molecular mechanisms of chemolithotrophic tetrathionate oxidation are not clearly understood. Here we used transposon(Tn5-mob)-insertion mutagenesis to search for novel tetrathionate oxidation genes in the facultatively chemolithoautotrophic betaproteobacterium Advenella kashmirensis that not only oxidizes tetrathionate, but also produces the same as an intermediate during thiosulfate oxidation. Genome-wide random insertion of Tn5-mob occurred at a frequency of one per 104 donor E. coli cells. A library of 8000 transconjugants yielded five tetrathionate-oxidation-impaired mutants, of which, the one named Ak_Tn_16 was studied here in detail. When grown chemolithoautotrophically on thiosulfate, Ak_Tn_16 converted the total thiosulfate supplied to equivalent amount of tetrathionate, exactly in the same way as the wild type. It could not, however, oxidize the intermediary tetrathionate to sulfate; Ak_Tn_16 could not also oxidize tetrathionate when it was supplied as the starting chemolithotrophic substrate. In the Ak_Tn_16 genome, Tn5-mob was found to have transposed in a novel soxO gene, located just-upstream of soxB, within the sox gene cluster. SoxO was predicted, via iterative threading assembly simulation, to be a glutathione-disulfide (GSSG) reductase. When Ak_Tn_16 was grown in tetrathionate-based chemolithoautotrophic medium supplemented with reduced glutathione (GSH) its tetrathionate-oxidation deficiency, remarkably, was ameliorated. Implications for a key role of GSH in tetrathionate oxidation are discussed in the light of other molecular evidences available for A. kashmirensis. © 2017 Elsevier GmbH

Chatterjee S.,Bidhannagar College | Saha A.,Visva Bharati University | Talukdar B.,Visva Bharati University
European Physical Journal D | Year: 2013

The Husimi distribution function is used to study the phase-space localization of Rydberg wave packets produced in a quasi one-dimensional hydrogen atom by the impact of half-cycle pulses (HCPs). The wave packet in a single-kicked atom exhibits transient phase-space localization. A weak second timedelayed HCP is found to extend the time of localization provided it is applied when the wave packet is near the inner turning point of the classical electron trajectory and momentum-transfer vectors of the first and the second kicks have the same sign. Alternatively, application of a similar second HCP increases the atomic ionization probability if the momentum-transfer vectors of the two kicks have opposite directions. © EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2013.

Mandal P.,Bidhannagar College | Molla A.R.,Taki Government College | Mandal D.K.,Bidhannagar College
Journal of Biochemistry | Year: 2013

Guanidine hydrochloride (GdnHCl)-induced unfolding of bovine spleen galectin-1 (Gal-1) exhibits three-state mechanism involving exclusive, structured tertiary monomer in 0.5M GdnHCl. Gal-1 has one tryptophan residue (Trp 68) per subunit. Phosphorescence spectra of both Gal-1 dimer and intermediate monomer at 77K show single (0,0) band at 405.6 nm, characteristics of free tryptophan environment as of N-acetyl-Ltryptophanamide. Unfolded Gal-1 in 4M GdnHCl gives (0,0) band at longer wavelength (408.6 nm) signifying that Trp 68 is less solvent exposed, being localized in an environment of residual structure. Trifluoroethanol (TFE)- and hexafluoroisopropanol (HFIP)-induced structural changes of Gal-1 dimer and monomer have been investigated by far-UV CD and FTIR. CD results show reversible nature of β-sheet to -helix transition, with 30% helix in 80% TFE or 40% HFIP for Gal-1 dimer. Temperaturedependent studies show that induced helix entails reduced thermal stability. FTIR results reveal partial b-sheet to a-helix conversion but with quantitative yield. At intermediate TFE concentration, both Gal-1 dimer and monomer aggregate as evidenced by FTIR band at ∼1617/cm, however, the onset of aggregation and stability of aggregates for monomer differ from those of dimer. The results may provide important insights into perturbed folding problem of Gal-1. © The Authors 2013. Published by Oxford University Press on behalf of the Japanese Biochemical Society. All rights reserved.

Chatterjee S.,Bidhannagar College
Physica Scripta | Year: 2012

For a one-dimensional atom, we derive an exact analytical expression for the uncertainty product of a Rydberg wave packet (WP) produced by the impact of two time-delayed half-cycle pulses (HCPs) and use the result to study the problems of its (WP's) phase-space localization. We also investigate how to effectively use the second HCP to increase the atomic ionization probability. The time delay (t 1) between the two HCPs plays a crucial role in both cases. The values of t 1 can be chosen for the second HCP to kick the WP when the latter is near the inner or outer turning point. We found that long-lived localized states are produced by the impact of the second HCP only when the WP is near the inner turning point. In the same situation, if the electron is kicked away from the nucleus, the atomic ionization probability tends to a maximum. © 2012 The Royal Swedish Academy of Sciences.

Talukdar D.,Saha Institute of Nuclear Physics | Chakraborty R.K.,Bidhannagar College | Bose S.,Saha Institute of Nuclear Physics | Bardhan K.K.,Saha Institute of Nuclear Physics
Review of Scientific Instruments | Year: 2011

A low noise constant current source used for measuring the 1f noise in disordered systems in ohmic as well as nonohmic regime is described. The source can supply low noise constant current starting from as low as 1 A to a few tens of milliampere with a high voltage compliance limit of around 20 V. The constant current source has several stages, which can work in a standalone manner or together to supply the desired value of load current. The noise contributed by the current source is very low in the entire current range. The fabrication of a low noise voltage preamplifier modified for bias dependent noise measurements and based on the existing design available in the MAT04 data sheet is also described. © 2011 American Institute of Physics.

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