St Berchmans College

Changanācheri, India

St Berchmans College

Changanācheri, India
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Paulose T.,St Berchmans College | Abraham K.E.,St Berchmans College
Journal of Optoelectronics and Advanced Materials | Year: 2017

We report dielectric and electron transport properties of hydrothermally synthesized ecofriendly Fe2O3 hexagonal nanomorphotype. The space charge polarization and orientational polarizations are the main mechanisms behind the dielectric property of Fe2O3 nanostructure. The frequency and temperature dependent impedance analysis was carried out in the frequency range 100Hz-1MHz. By theoretical fitting methods, the dielectric relaxation formalism has been identified as the Cole-Cole like relaxation. The AC conductivity in the nanomorphotype obeys the universal power law and also the frequency exponent parameter "s" decreases with increase in temperature. Correlating the nature of "s" with various theoretical models and observing that the conduction mechanism is mostly due to the thermally activated charge carriers, both overlapped polaron hopping transport (OLPT) and correlated barrier hopping (CBH) theoretical models are found to be valid in the present case. The dielectric study of Fe2O3 hexagonal nanomorphotype opens up the way for developing charge storage devices with least environmental hazard.

George G.,St Berchmans College | George G.,Kalasalingam University | Tomlal Jose E.,St Berchmans College | Jayanarayanan K.,Amrita University | And 3 more authors.
Composites Part A: Applied Science and Manufacturing | Year: 2012

This paper mainly investigates the fabrication process of jute yarn reinforced, bidirectional thermoplastic commingled composites (both untreated and treated). Commingling method was used to prepare the composites wherein the Polypropylene yarn (PP yarn) and jute yarn were wound together onto a metal plate in a particular configuration and then compression moulded. The mechanical properties of the composites prepared from chemically treated jute yarn were found to increase substantially compared to those of untreated ones. The surface morphologies of the fracture surfaces of the composites were recorded using scanning electron microscope (SEM). The SEM micrographs reveal that interfacial bonding between the treated jute yarn and the matrix has improved significantly by chemical treatments. The various chemical treatment mechanisms have been supported by FT-IR spectra. Theoretical modelling was used to predict the tensile properties and was found to be in accordance with the experimental results. © 2011 Elsevier Ltd. All rights reserved.

Farooqui A.,University of Lucknow | Ray J.G.,St Berchmans College | Farooqui S.A.,Directorate of Geology and Mining | Tiwari R.K.,Geological Survey of India | Khan Z.A.,Directorate of Geology and Mining
Quaternary International | Year: 2010

The southwestern Ghats region of the Indian Peninsula is unique for its extant endemic rainforest flora supported by high rainfall throughout the year. The record of tropical rainforest corresponding to the dynamic series of Pleistocene interglacial/glacial cycles is poorly known from peninsular India. This communication discusses the palynological study of organic matter (OM) deposits (>40 ka BP) in two well sections (Chaganachery, Kerala) from the Indian Peninsula (west coast). A rich archive of tropical rainforest pollen/spores and marine dinoflagellate cysts indicates anoxic fluvio-marine/estuarine depositional environments during warmer climates with an intensified Asian monsoon. The geochemical fingerprinting of glass shards indicates the presence of Youngest Toba ash of ∼74 ka from northern Sumatra, and therefore establishes a time-controlled stratigraphy. Thus, the depositional time period of the OM is related to the sea level highstand of Marine Isotopic Stage 5.1 (∼80 ka) which was the host to the YTT shards. The Late Quaternary pollen/spores diversity suggests that the modern climatic conditions in the southwestern Ghats have facilitated the conservation of moist evergreen rainforest and dry/moist deciduous forest. The pollen grains show its lineage with the extant flora and some of the fossil pollen recorded during the mesic Tertiary period from the Indian peninsula. Thus, it appears that the tropical rainforest survived here as 'Plant Refugia' in xeric (glacial) Quaternary periods, perhaps as riparian vegetation, and was rejuvenated during the Holocene as modern extant flora. © 2009 Elsevier Ltd and INQUA.

George G.,St Berchmans College | George G.,Kalasalingam University | Joseph K.,Indian Institute of Space Science and Technology | Nagarajan E.R.,Kalasalingam University | And 2 more authors.
Composites Part A: Applied Science and Manufacturing | Year: 2013

Polypropylene and jute yarns were used to prepare commingled composites using commingling technique where the natural fibres are subjected to minimal shear forces. The dielectric constant, loss factor and conductivity increased with fibre content where as volume resistivity decreased due to the better net orientational polarisation in jute yarn reinforced polypropylene (PP) commingled composites. However due to a reduction in the hydrophilic nature of jute yarns brought about by chemical treatments the dielectric constants and conductivities of treated composites was less than that of the untreated ones as a result of reduction in orientational polarisation and moisture absorbance. As temperature increased the dielectric constant, loss factor and conductivity first increased up to a particular temperature and then decreased due to a reduction in orientational polarisation brought about by the increased molecular vibrations with increasing temperature. Wet samples showed much higher dielectric constant and conductivity values compared to their dry counterparts. © 2012 Elsevier Ltd. All rights reserved.

Job J.,St Berchmans College | Sukumaran R.K.,CSIR - Central Electrochemical Research Institute | Jayachandran K.,Mahatma Gandhi University
World Journal of Microbiology and Biotechnology | Year: 2010

β-Glucosidases (β-D-glucoside glucohydrolase, are a group of enzymes mainly involved in the hydrolysis of β-glycosidic bonds connecting carbohydrate residues in different classes of β-D glycosides. During cellulose degradation they convert cellobiose and cellooligosaccharides produced by the endo and exoglucanases to glucose. Most of the microbial β-glucosidases are inhibited by glucose. This limits their application in commercial scale cellulose degradation ventures. Solid state fermentation production of a highly glucose tolerant β-glucosidase by a novel isolate of Paecilomyces was optimized using a two step statistical experiment design. In the first step which employed a Plackett-Burman design, the effects of parameters such as moisture, temperature, pH, inoculum concentration, incubation time and different concentrations of (NH4)2SO4, KH2PO4, NaCl, peptone and cellobiose were evaluated. The parameters with significant influence on the process were selected and fine tuned in the second step using a Box-Behnken design. The model obtained was validated and a peptone concentration of 2 g/l, inoculum concentration of 1.2 × 106 spores/ml and an incubation period of 96 h were found to be optimum for the maximum production of the enzyme. The optimization resulted in a doubling of the enzyme production by the fungus. © 2010 Springer Science+Business Media B.V.

Mani T.,Rajiv Gandhi Center for Biotechnology | Mani T.,St Berchmans College | Sivakumar K.C.,Rajiv Gandhi Center for Biotechnology | Manjula S.,Rajiv Gandhi Center for Biotechnology
Molecular Biotechnology | Year: 2012

Osmotin, a pathogenesis-related antifungal protein, is relevant in induced plant immunity and belongs to the thaumatin-like group of proteins (TLPs). This article describes comparative structural and functional analysis of the two osmotin isoforms cloned from Phytophthoraresistant wild Piper colubrinum. The two isoforms differ mainly by an internal deletion of 50 amino acid residues which separates them into two size categories (16.4 kDa- PcOSM1 and 21.5 kDa-PcOSM2) with pI values 5.6 and 8.3, respectively. Recombinant proteins were expressed in E. coli and antifungal activity assays of the purified proteins demonstrated significant inhibitory activity of the larger osmotin isoform (PcOSM2) on Phytophthora capsici and Fusarium oxysporum, and a markedly reduced antifungal potential of the smaller isoform (PcOSM1). Homology modelling of the proteins indicated structural alterations in their threEdimensional architecture. Tertiary structure of PcOSM2 conformed to the known structure of osmotin, with domain I comprising of 12 β-sheets, an a-helical domain II and a domain III composed of 2 β-sheets. PcOSM1 (smaller isoform) exhibited a distorted, indistinguishable domain III and loss of 4 β-sheets in domain I. Interestingly, an interdomain acidic cleft between domains I and II, containing an optimally placed endoglucanase catalytic pair composed of Glu-Asp residues, which is characteristic of antifungal PR5 proteins, was present in both isoforms. It is well accepted that the presence of an acidic cleft correlates with antifungal activity due to the presence of endoglucanase catalytic property, and hence the present observation of significantly reduced antifungal capacity of PcOSM1 despite the presence of a strong acidic cleft, is suggestive of the possible roles played by other structural features like domain I or/and III, in deciding the antifungal potential of osmotin. © Springer Science+Business Media, LLC 2012.

Vijayan P.P.,St Berchmans College | Thomas M.,Bcm College | George K.C.,St Berchmans College
Journal of Applied Physics | Year: 2012

Nanotubes of TiO2 synthesized by hydrothermal method are treated at three different temperatures (400, 600, and 800°C). Calcinations cause phase change as evidenced from x-ray diffraction patterns. AC conductivity studies done on as prepared TiO2 and calcined samples in the frequency range 100Hz-1MHz and at various temperatures between 303 and 423 K. AC conductivity increases with the calcination followed by a decrease which can be attributed to rutile formation. Surface defects are responsible for the ac conductivity change. PL spectrum shows the presence of surface oxygen vacancies and self trapped excitons in TiO2 nanotubes and annealed samples. The variable range hopping dominates the mode of electrical transport at low temperature and thermally activated process at high temperature. Conductivity is at its maximum for the sample calcined at 400°C. There is a transition temperature in between the variable range hopping and thermally activated process, which differs with calcinations. © 2012 American Institute of Physics.

Thomas P.,St Berchmans College | Abraham K.E.,St Berchmans College
Journal of Luminescence | Year: 2015

We report the red-shifted photoluminescence (PL) band edge emission behavior as a function of subsequent increment in excitation wavelength on cadmium oxide (CdO) nanoflakes and nanoparallelepiped morphotypes prepared through the hydrothermal method. The unusual band edge PL emission lines in crystalline nanomaterials are explained as strong quantum size effect due to the size selective band gap widening in nanomaterials. This kind of excitation wavelength dependent PL emission behavior appears to be in violation of Kasha's rule of excitation wavelength independence of the emission spectrum. The surface morphology, particle size, molecular structure, chemical composition and chemical bonding of the samples are analyzed by SEM, TEM, XRD, EDS and FTIR spectroscopy. Direct optical band gap is calculated and found to be of 2.75 eV for nanoflakes and 2.52 eV for parallelepiped nanostructures. ©2014 Elsevier B.V. All rights reserved.

Mahalakshmi V.,St Berchmans College | Lincy A.,St Berchmans College | Thomas J.,St Berchmans College | Saban K.V.,St Berchmans College
Journal of Physics and Chemistry of Solids | Year: 2012

Crystals of barium tetrakis(maleate) dihydrate [Ba 4(C 4H 2O 4) 4] *2H 2O are grown in gelated hydrosilica matrix. Single crystal X-ray diffraction studies show that the crystal system is monoclinic with space group P2 1/c. The unit cell dimensions are a=9.3721(2) Å, b=20.5880(7) Å, c=14.0744(4) Å, α=γ=90°, β=90.289(2)°. Powder XRD studies confirmed the single phase nature of the grown crystals. The FTIR data is in conformity with the XRD results. The TGDTA curves of the material indicate a three-step thermal decomposition. The response of the dielectric properties in the temperature range 30 °C to 500 °C is correlated with the TGDTA results. © 2011 Elsevier Ltd. All rights reserved.

Thomas P.,St Berchmans College | Sreekanth P.,Raman Research Institute | Abraham K.E.,St Berchmans College
Journal of Applied Physics | Year: 2015

Nonlinear optical absorption and optical power limiting properties of Fe2O3 hexagonal nanomorphotype are investigated using open aperture Z-scan technique with the 5ns and 100 fs laser pulses, at 532nm and 800nm excitation domains. At relatively low pulse energies (below 5 μJ), sample shows saturable absorption (SA), but on going to the higher energies an interesting switchover from saturable absorption to effective two photon absorption is observed in both excitation domains. The magnitude of effective two photon absorption coefficients is calculated to be in the range of 10-10 m/W for nanosecond and 10-15 m/W for femtosecond laser pulse energies, respectively. XRD and TEM study reveals the polycrystalline nature, hexagonal morphology, and size of the nanostructure. The luminescence emission property is examined by photoluminescence spectroscopy (PL). It is found that some strange features exist in the luminescence spectra that are consistent with the nanoparticles size distribution. The PL emission lines are explained as originated from various optical band edges due to the size induced quantum confinement and band gap resonant PL absorption/emission behavior of semiconductor nanostructures. © 2015 AIP Publishing LLC.

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