Kerala, India
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Sheeba M.,NSS College | Ranjith A.P.,University of Calicut | Narendran T.C.,Western Ghat Regional Center
Zootaxa | Year: 2017

The Braconinae is a generically diverse subfamily of Braconidae. The Old World genus Testudobracon Quicke is reviewed and four new species viz., T. athashi Ranjith sp. nov., T. malabaricus Sheeba sp. nov., T. shameeri Ranjith sp. nov. and T. travencorensis Sheeba sp. nov., are described from south India. A check list and key to the world species are provided. © 2017 Magnolia Press.


Wilson R.,Mahatma Gandhi University | George S.M.,Mahatma Gandhi University | Maria H.J.,Mahatma Gandhi University | Plivelic T.S.,Lund University | And 3 more authors.
Journal of Physical Chemistry C | Year: 2012

Nanocomposite membranes based on poly(ethylene-co-vinyl acetate) copolymer (18% vinyl acetate content) and two different organomodified clays have been prepared by mechanical mixing using two roll mill method. The morphology of the nanocomposites was investigated using small angle X-ray scattering, scanning electron microscopy, and transmission electron microscopy. The mechanical and thermal studies were also performed using universal testing machine and differential scanning calorimeter, respectively. Samples with low filler content showed excellent dispersion of layered silicates resulting in a partially exfoliated structure. The diffusion and transport of organic solvents through the membranes have been investigated in detail as a function of clay content, nature of solvent and clay, and temperature in the temperature range of 28-70 °C. The influence of free volume on the transport properties of the membranes was studied using positron annihilation lifetime spectroscopy. The solvent uptake was minimum for composites with 3 wt % of filler, and it get increased with increasing filler content, which is presumably due to aggregation of clay filler at higher loading. The transport phenomenon was found to follow an anomalous mode. Activation parameters were estimated, and the molar mass between cross-links was calculated. Finally, the experimental transport data were compared with theoretical predictions. © 2012 American Chemical Society.


Marega C.,University of Padua | Causin V.,University of Padua | Saini R.,University of Padua | Marigo A.,University of Padua | And 3 more authors.
Journal of Physical Chemistry B | Year: 2012

The interfacial area between the matrix and the filler is a key parameter which shapes the performance of polymer-based composites and nanocomposites, even though it is difficult to quantify. A very easy SAXS method, based on the Porod equation, is proposed for measuring the specific surface area of nanofillers embedded in a polymer matrix. In order to assess its reliability, this approach was applied to natural rubber- or styrene butadiene-based samples containing different types of montmorillonite clay. A wide range of specific surfaces was detected. SAXS data were compared to complementary X-ray diffraction and TEM information, obtaining a good agreement. Interpretation of the tensile properties by theoretical models and comparison with the literature corroborated the validity of the specific surface area measurement. The possibility to quantify this feature of composites allows the rational design of such materials to be improved. © 2012 American Chemical Society.


Dhanya V.S.,Mg College | Sudarsanakumar M.R.,Mg College | Suma S.,Sn College | Prasanna S.,Nss College For Women | And 3 more authors.
Journal of Crystal Growth | Year: 2011

Single crystals of a new polymorph of lead succinate Pb(C4H 4O4) with nonlinear optical (NLO) properties have been successfully grown by gel diffusion technique. The crystallinity of the grown crystals has been analyzed by powder X-ray diffraction studies. Single crystal X-ray diffraction analysis shows that the compound belongs to monoclinic system and is having a compact three-dimensional polymeric structure. Fourier transform infrared (FT-IR) and Fourier transform Raman (FT-Raman) spectral studies have been performed to identify the functional groups. Thermo gravimetric analysis (TGA) and differential thermal analysis (DTA) were used to study its thermal properties. The optical transmittance window and the lower cut off wavelength of the crystal have been identified by UVvisible transmittance studies. Dielectric constant and dielectric loss of the grown crystals were evaluated for the frequency range 300 Hz3 MHz. The second harmonic output intensity was tested using the Kurtz and Perry powder method and was found to be 3.5 times as large as potassium dihydrogen phosphate (KDP). © 2011 Elsevier B.V.


Krishnan R.J.,Nss College
Biosciences Biotechnology Research Asia | Year: 2012

Periyar Lake, situated inside the Periyar Tiger Reserve (PTR) and Wildlife Sanctuary, a major international tourist centre in Kerala, was studied for a year (January to December 2005), in order to explore the nutrient status and associated phytoplankton growth. This oldest manmade freshwater reservoir/Lake in the Western Ghats of Kerala, is getting more attention now a days due to the dispute between Kerala State and Tamil Nadu (TN) State for the ownership of the Mullaperiyar Dam. More over it is situated inside India's prime Tiger reserve in its quantity, area and quality. Total Nitrogen and inorganic Phosphorus of the waters were studied every month and the data were grouped into three different seasons and analyzed the seasonal fluctuation if any, moreover, water samples from different parts of the entire Lake were also analyzed to account any spatial variation due the increasing anthropogenic influence in and around the Lake related with tourism. From the study it was revealed that Nitrogen and Phosphorus concentration of the Lake was at an alarming rate during premonsoon and northeast monsoon in stations-1 and 5 (2400 to 3000 μg/L), with maximum human influence and sewage entry. While the inlets zones (station-4) showed minimum N and P contents (1500 μg/L) . The density of Phytoplankton showed a positive correlation with the nutrients in almost ail seasons. The highest plankton density( 490 no./L) was recorded during premonsoon at station-5 and the lowest was at station-4 (253 no./L) during northeast monsoon. From this study it was clear that the nutrient and phytoplankton of the Lake is dependent on the seasonal fluctuations in the environment as well influenced by the increased anthropogenic activities in and around the Lake. Strict measures should be taken to monitor the water quality of this pristine water body within the sanctuary because this is the source of drinking water for 4 Districts of TN.


Viji Z.,NSS College | Paulsamy,Kongunadu Arts and Science College
Research Journal of Pharmaceutical, Biological and Chemical Sciences | Year: 2015

The aim of this study is to evaluate the total phenolics,flavonoids,and tannin content and determine antioxidant activity of different fractions of P. tuberosa extracts. Antioxidant potential of petroleumether, chloroform, acetone, methanol and hot water extracts by using FRAP, metal chelating, phosphomolybdenum and free radical scavenging by using DPPH• and ABTS•+ were determined by using standard protocols with slight modifications. Quantification assays were carried out for the determination of phenols by Folin-ciocalteu method, tannins by using polyvinylpyrrolidine (PVPP) and flavonoids by aluminum chloride colorimetric method. Higher amount of phenols were found in acetone extract that is why itshows higher antioxidant activity. In ABTS+ assay higher scavenging activity of the tuber was observed in methanolic extract(9328.44±1923.77μmoles TE/g extract). In the present study the chloroform fraction was found to be more potent hydroxyl radical scavenger, with an IC50 value of 119.59μg/ml compared to other extracts.Acetone extract showed good antioxidant potential using FRAP(1796.67±146.21mmolesFeII/mg, metal chelating (112.78 ± 3.7512.78mg EDTA/gmextract, phosphomolybdenum (15.52 g AA/100g extract).). The total phenolic and tannin content was found to be higher in acetone extracts of tuber (443.87mg GAE/g and290.41mgGAE/g. The present results suggests that acetone extracts of P. tuberosa has significant antioxidant activity that it is effective against free radical mediated diseases and may be considered as natural source of antioxidant.


Wilson R.,Mahatma Gandhi University | Plivelic T.S.,Lund University | Ramya P.,University of Mysore | Ranganathaiah C.,University of Mysore | And 3 more authors.
Industrial and Engineering Chemistry Research | Year: 2011

Poly(ethylene-co-vinyl acetate)/organically modified clay nanocomposites were prepared using different clay loadings and by varying the amount of organic modifier. The morphology of the nanocomposites was investigated using small-angle X-ray scattering (SAXS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). SAXS results displayed intercalation of polymeric chains between the silicate layers in all the cases. The interlayer distance varies slightly between the series. TEM images showed a better dispersion of the clay platelets at lower loading for both series of samples. The pervaporation performances of membranes were analyzed using a chloroform/acetone mixture. Membranes displayed high selectivity. The influence of feed composition on pervaporation was analyzed. The nanoclay content and the influence of free volume on pervaporation performance were also investigated in detail. A drop in selectivity and an increase in permeation rate were observed at higher clay loadings. © 2011 American Chemical Society.


Praveen V.N.,Nss College | Vijayan N.,National Physical Laboratory India | Mahadevan C.K.,Physics Research Center
Optik | Year: 2012

Pure and urea added zinc tris(thiourea)sulphate (ZTS) single crystals were grown by the solvent evaporation method from aqueous solutions. The grown crystals were characterized by X-ray powder diffraction, Fourier transform infrared, second harmonic generation and density measurements. The observed results show that the small amount of urea molecules were incorporated in the crystalline matrix of ZTS crystals. Dielectric measurements were carried out along a-, b- and c-directions of the grown crystals at various temperatures by the conventional parallel plate capacitor method with a fixed frequency of 1 kHz. The present study shows that the dielectric parameters (viz. dielectric constant, dielectric loss and a.c. conductivity) increases with the increase in temperature for all the grown crystals. Activation energies were also determined. © 2011 Elsevier GmbH.


Wilson R.,Mahatma Gandhi University | Plivelic T.S.,Lund University | Aprem A.S.,Hindustan Latex Ltd. | Ranganathaiagh C.,University of Mysore | And 2 more authors.
Journal of Applied Polymer Science | Year: 2012

Poly (ethylene-co-vinyl acetate) (EVA)/clay nanocomposites containing two different organoclays with different clay loadings were prepared. The transport of gases (oxygen and nitrogen) through the composite membranes was investigated and the results were compared. These studies revealed that the incorporation of nanoclays in the polymer increased the efficiency of the membranes toward barrier properties. It was also found that the barrier properties of the membranes decreased with clay loadings. This is mainly due to the aggregation of clay at higher loadings. The morphology of the nanocomposites was studied by scanning electron microscopy, transmission electron microscopy and X-ray scattering. Small angle X-ray scattering results showed significant intercalation of the polymer chains between the organo-modified silicate layers in all cases. Better dispersed silicate layer stacking and more homogeneous membranes were obtained for Cloisite® 25A based nanocomposites compared with Cloisite® 20A samples. Microscopic observations (SEM and TEM) were coherent with those results. The dispersion of clay platelets seemed to be maximized for 3 wt % of clay and agglomeration increased with higher clay loading. Wide angle X-ray scattering results showed no significant modifications in the crystalline structure of the EVA matrix because of the presence of the clays. The effect of free volume on the transport behavior was studied using positron annihilation spectroscopy. The permeability results have been correlated with various permeation models. © 2011 Wiley Periodicals, Inc.


Uma Maheswari A.,Amrita University | Saravana Kumar S.,NSS College | Sivakumar M.,Amrita University
Journal of Nanoscience and Nanotechnology | Year: 2013

In this work, the influence of different alkaline mineralizers on structural and optical properties of zirconia nanoparticles synthesized by chemical co-precipitation technique using zirconium oxychloride octahydrate (ZrOCl2 ·8H2O) as precursor is studied. The mineralizers used for the synthesis of nanoparticles are NaOH and NH 4OH. X-ray diffraction, Fourier Transform Infrared (FTIR) spectroscopy, UV-visible absorption spectroscopy and Photoluminescence (PL) spectroscopy were used for characterizing the nanoparticles. Structural analysis of the sample synthesized using NaOH shows monoclinic phase as predominant one, however when NH4OH is used the major phases are cubic and tetragonal. The difference is attributed to the number of hydroxyl ions produced and their rate of release during the reaction process. The presence of these phases in both samples is further confirmed by vibrational bands of FT-IR spectra. Also, the low energy bands due to the presence of defects in nanoparticles are also explicitly observed in the photoluminescence spectra. Further the defects lead to a red shift in the band gap of ZrO2 which is observed when the samples are subjected to UV-absorption spectroscopy analysis. It has been demonstrated that zirconia nanoparticles with desired structural properties can be synthesized by changing the type of mineralizer without the necessity of doping. Copyright © 2013 American Scientific Publishers All rights reserved.

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