Augustin M.,St Xaviers College Autonomous
Materials Today: Proceedings | Year: 2015
Zinc ferrite (ZnFe2O4) and Manganese ferrite (MnFe2O4) nanoparticles were prepared by the chemical co-precipitation method and calcinated at 8000C for 5hrs. The results of XRD and SEM show that sample product was crystalline with mixed type spinel with cubic structure. The FT-IR spectrum shows most intense absorption bands 464 cm-1 and 550 cm-1 due to the strong transition metal stretching. Uv-vis studies reveal the band gap energy variation between different metal substitutions in the synthesis. Coercivity of ZnFe2O4 and MnFe2O4 nanoparticles was calculated using VSM studies is in the range of 14.456 G and 50.495 G respectively. © 2015 Elsevier Ltd.
Gopal R.,Bose Institute of India |
Roychowdhury S.,St Xaviers College Autonomous
Journal of Cosmology and Astroparticle Physics | Year: 2010
In this work we study the contribution of magnetic fields to the Sunyaev Zeldovich (SZ) effect in the intracluster medium. In particular we calculate the SZ angular power spectrum and the central temperature decrement. The effect of magnetic fields is included in the hydrostatic equilibrium equation by splitting the Lorentz force into two terms - one being the force due to magnetic pressure which acts outwards and the other being magnetic tension which acts inwards. A perturbative approach is adopted to solve for the gas density profile for weak magnetic fields (≤ 4μG). This leads to an enhancement of the gas density in the central regions for nearly radial magnetic field configurations. Previous works had considered the force due to magnetic pressure alone which is the case only for a special set of field configurations. However, we see that there exists possible sets of configurations of ICM magnetic fields where the force due to magnetic tension will dominate. Subsequently, this effect is extrapolated for typical field strengths (∼ 10μG) and scaling arguments are used to estimate the angular power due to secondary anisotropies at cluster scales. In particular we find that it is possible to explain the excess power reported by CMB experiments like CBI, BIMA, ACBAR at ℓ > 2000 with σ8 ∼ 0.8 (WMAP 5 year data) for typical cluster magnetic fields. In addition we also see that the magnetic field effect on the SZ temperature decrement is more pronounced for low mass clusters (T ∼ 2 keV). Future SZ detections of low mass clusters at few arc second resolution will be able to probe this effect more precisely. Thus, it will be instructive to explore the implications of this model in greater detail in future works. © 2010 IOP Publishing Ltd and SISSA.
Guha S.,St Xaviers College Autonomous |
Chakraborty S.,Jadavpur University
General Relativity and Gravitation | Year: 2010
In the "braneworld scenario" ordinary standard model matter and non-gravitational fields are confined by some trapping mechanism to the 4-dimensional universe constituting the D3-branes which are embedded in a (4 + n)-dimensional manifold referred to as the 'bulk' (n being the number of extra dimensions). The notion of particle confinement is necessary for theories with non-compact extra dimensions, otherwise, the particles would escape from our 4-dimensional world along unseen directions. In this paper, we have considered a five-dimensional warped product space-time having an exponential warping function which depends both on time as well as on the extra coordinates and a non-compact fifth dimension. Assuming that the lapse function may either be a constant or a function of both time and of the extra coordinates, we have studied the nature of the geodesics of test particles and photons and have analyzed the conditions of stability in this geometrical framework. We have also discussed the possible cosmology of the corresponding (3 + 1)-dimensional hypersurfaces. © 2010 Springer Science+Business Media, LLC.
Jeeva S.,Center for Biodiversity and Biotechnology |
Antonisamy J.M.,St Xaviers College Autonomous
Asian Pacific Journal of Tropical Biomedicine | Year: 2012
Objective: To investigate the antibacterial activity and phytochemical properties of Begonia floccifera Bedd. (B. floccifera) methanolic flower extracts against the selected pathogens. Methods: 20 g of fresh flowers were soaked in 100 mL methanol for 48 h at room temperature. After 48 h, the extracts were filtered using Whatman No. 41 filter paper. The filtrates were collected, made up to known volume and stored in refrigerator at 4 °C. The methanolic extracts were used for phytochemical and antibacterial studies. The preliminary phytochemical screening was performed according to the modified Harborne method. The methanolic flower extracts of B. floccifera Bedd. was tested against Escherichia coli, Klebsiella pneumonia, Pseudomonas aeruginosa, Staphylococcus aureus, Bacillus cereus, Salmonella typhi, Serratia marcescens, Proteus mirabilis, Enterococcus faecalis and Streptococcus pyogenes by the disc diffusion method. Results: The results of the phytochemical screening revealed that phenol, tannins, xanthoproteins, steroids, tannins, steroids, phytosterols, triterpenoids, sapogenins, coumarins and carbohydrates presence in the methanolic extracts of B. floccifera. The antibacterial activity has been observed in the methanolic extracts of B. floccifera against the tested bacteria with varied activity. The maximum zone of inhibition was 28 mm for Bacillus cereus, 25 mm for Staphylococcus aureus, 15 mm for Escherichia coli, 13 mm for Proteus mirabilis, 7 mm for Klebsiella pneumonia. Conclusions: The antimicrobial activity of B. floccifera methanolic flower extracts are comparable and their potential as alternative in the treatment of infectious by these microorganisms. © 2012 Asian Pacific Tropical Biomedical Magazine.
Basu S.,University of Arkansas |
Roychoudhury A.,St Xaviers College Autonomous
BioMed Research International | Year: 2014
The present study considered transcriptional profiles and protein expression analyses from shoot and/or root tissues under three abiotic stress conditions, namely, salinity, dehydration, and cold, as well as following exogenous abscisic acid treatment, at different time points of stress exposure in three indica rice varieties, IR-29 (salt sensitive), Pokkali, and Nonabokra (both salt tolerant). The candidate genes chosen for expression studies were HKT-1, SOS-3, NHX-1, SAPK5, SAPK7, NAC-1, Rab16A, OSBZ8, DREBP2, CRT/DREBP, WRKY24, and WRKY71, along with the candidate proteins OSBZ8, SAMDC, and GST. Gene expression profile revealed considerable differences between the salt-sensitive and salt-tolerant rice varieties, as the expression in the latter was higher even at the constitutive level, whereas it was inducible only by corresponding stress signals in IR-29. Whether in roots or shoots, the transcriptional responses to different stressors peaked following 24 h of stress/ABA exposure, and the transcript levels enhanced gradually with the period of exposure. The generality of stress responses at the transcriptional level was therefore time dependent. Heat map data also showed differential transcript abundance in the three varieties, correlating the observation with transcript profiling. In silico analysis of the upstream regions of all the genes represented the existence of conserved sequence motifs in single or multiple copies that are indispensable to abiotic stress response. Overall, the transcriptome and proteome analysis undertaken in the present study indicated that genes/proteins conferring tolerance, belonging to different functional classes, were overrepresented, thus providing novel insight into the functional basis of multiple stress tolerance in indica rice varieties. The present work will pave the way in future to select gene(s) for overexpression, so as to generate broad spectrum resistance to multiple stresses simultaneously. © 2014 Supratim Basu and Aryadeep Roychoudhury.
Ganguly S.,St Xaviers College Autonomous
Journal of the Indian Chemical Society | Year: 2012
The 'complex as a ligand' strategy is employed to synthesize hetero-binuclear complexes of RuIII-MI (M = Cu, Ag). The complexes were characterized by spectral methods in particular and the cell parameters of one of the representative complex were determined to predict the structure of the complexes.
Dey S.,St Xaviers College Autonomous
2012 2nd International Conference on Digital Information Processing and Communications, ICDIPC 2012 | Year: 2012
In this paper, the author propose a method, SD-AEI, for image encryption, which is an upgraded module for SD-EI combined image encryption technique and basically has three stages: 1) In first stage, each pixel of image is converted to its equivalent eight bit binary number and in that eight bit number, the number of bits, which are equal to the length of password are rotated and then reversed; 2) In second stage, extended hill cipher technique is applied by using involutory matrix, which is generated by same password used in second stage of encryption to make it more secure; 3) In third stage, the whole image file is randomized multiple number of times using Modified MSA Randomization encryption technique and the randomization is dependent on an unique number, which is generated from the password provided for encryption. This proposed technique, SD-AEI, is very effective in encrypting any type of images and the results were very satisfactory. SD-AEI method is also compared with various other image encryption techniques and it was found that SD-AEI cryptographic method takes optimal amount of time when compared to other encryption techniques, for encrypting and decrypting an image file. This method can be used to encrypt any type of image file, especially secret images, where steganography has been applied, so that the contents in the image file can be kept more secure. © 2012 IEEE.
Guha S.,St Xaviers College Autonomous |
Banerji R.,Saha Institute of Nuclear Physics
International Journal of Theoretical Physics | Year: 2014
We have studied the dynamics of a cylindrical column of anisotropic, charged fluid which is experiencing dissipation in the form of heat flow, free-streaming radiation, and shearing viscosity, undergoing gravitational collapse. We calculate the Einstein-Maxwell field equations and, using the Darmois junction conditions, match the interior non-static cylindrically symmetric space-time with the exterior anisotropic, charged, cylindrically symmetric space-time. The behavior of the density, pressure and luminosity of the collapsing matter has been analyzed. From the dynamical equations, the effect of charge and dissipative quantities over the cylindrical collapse are studied. Finally, we have derived the solutions for the collapsing matter which is valid during the later stages of collapse and have discussed the significance from a physical standpoint. © 2014, Springer Science+Business Media New York.
Guha S.,St Xaviers College Autonomous |
Bhattacharya P.,Gopal Nagar High School
Journal of Physics: Conference Series | Year: 2012
We have studied the geodesics of neutral particles near a non-rotating, charged five-dimensional Reissner-Nordström Anti-de Sitter black hole using the effective potential analysis and the dynamical systems analysis. The effective potential analysis is used to determine the location of the horizon and to study radial and circular trajectories. The dynamical systems method is used to determine the stability and the fixed points of the phase trajectories.
Roychoudhury A.,St Xaviers College Autonomous |
Paul S.,St Xaviers College Autonomous |
Basu S.,University of Arkansas
Plant Cell Reports | Year: 2013
Salinity, drought and low temperature are the common forms of abiotic stress encountered by land plants. To cope with these adverse environmental factors, plants execute several physiological and metabolic responses. Both osmotic stress (elicited by water deficit or high salt) and cold stress increase the endogenous level of the phytohormone abscisic acid (ABA). ABA-dependent stomatal closure to reduce water loss is associated with small signaling molecules like nitric oxide, reactive oxygen species and cytosolic free calcium, and mediated by rapidly altering ion fluxes in guard cells. ABA also triggers the expression of osmotic stress-responsive (OR) genes, which usually contain single/multiple copies of cis-acting sequence called abscisic acid-responsive element (ABRE) in their upstream regions, mostly recognized by the basic leucine zipper-transcription factors (TFs), namely, ABA-responsive element-binding protein/ABA-binding factor. Another conserved sequence called the dehydration-responsive element (DRE)/C-repeat, responding to cold or osmotic stress, but not to ABA, occurs in some OR promoters, to which the DRE-binding protein/C-repeat-binding factor binds. In contrast, there are genes or TFs containing both DRE/CRT and ABRE, which can integrate input stimuli from salinity, drought, cold and ABA signaling pathways, thereby enabling cross-tolerance to multiple stresses. A strong candidate that mediates such cross-talk is calcium, which serves as a common second messenger for abiotic stress conditions and ABA. The present review highlights the involvement of both ABA-dependent and ABA-independent signaling components and their interaction or convergence in activating the stress genes. We restrict our discussion to salinity, drought and cold stress. © 2013 Springer-Verlag Berlin Heidelberg.