Nss Hindu College

Changanācheri, India

Nss Hindu College

Changanācheri, India
SEARCH FILTERS
Time filter
Source Type

Menachery S.P.M.,Mahatma Gandhi University | Laprevote O.,University of Paris Descartes | Nguyen T.P.,Pohang University of Science and Technology | Aravind U.K.,Mahatma Gandhi University | And 2 more authors.
Journal of Mass Spectrometry | Year: 2015

This study reports an energy-resolved mass spectrometric (ERMS) strategy for the characterization of position isomers derived from the reaction of hydroxyl radicals (-OH) with diphenhydramine (DPH) that are usually hard to differentiate by other methods. The isomer analogues formed by •OH attack on the side chain of DPH are identified with the help of a specific fragment ion peak (m/z 88) in the collision-induced dissociation (CID) spectrum of the protonated molecule. In the negative ion mode, the breakdown curves of the deprotonated molecules show an order of stability (supported by density functional theory (DFT) calculations) ortho > meta > para of the positional isomers formed by the hydroxylation of the aromatic ring. The gas phase stability of the deprotonated molecules [M - H]- towards the benzylic cleavage depends mainly on the formation of intramolecular hydrogen bonds and of the mesomeric effect of the phenol hydroxyl. The [M - H]- molecules of ortho and meta isomers result a peak at m/z 183 with notably different intensities because of the presence/absence of an intramolecular hydrogen bonding between the OH group and C9 protons. The ERMS approach discussed in this report might be an effective replacement for the conventional methods that requires very costly and time-consuming separation/purification methods along with the use of multi-spectroscopic methods. Copyright © 2015 John Wiley & Sons, Ltd.


Sunil Paul M.M.,Mahatma Gandhi University | Aravind U.K.,Mahatma Gandhi University | Aravind U.K.,Center for Environment Education and Technology | Pramod G.,Nss Hindu College | Aravindakumar C.T.,Mahatma Gandhi University
Chemosphere | Year: 2013

Oxidative degradation of fensulfothion, a model organophosphorus compound, has been investigated by pulse radiolysis and H2O2/UV photolysis. A nearly complete transformation of fensulfothion was observed within 4min of irradiation. Very little Total Organic Carbon (TOC) reduction was obtained at this time scale. When the product studies at this stage were conducted using LC-MS/MS analyses, nearly 20 transformation products were obtained. The entire products were identified as from the reaction of OH with fensulfothion or with some of its initially transformed products. Nearly 80% reduction in TOC was observed when photolysis was conducted using higher concentrations of H2O2 at longer time scale. A reaction rate constant (bimolecular) of 1.10×1010dm3mol-1s-1 was obtained for the reaction of OH with fensulfothion using pulse radiolysis technique. The transient absorption spectrum obtained from the reaction of OH has a maximum at 280nm and a weak, broad maximum around 500nm along with a small shoulder around 340nm. The intermediate spectrum is assigned to the radical cation of fensulfothion (3) and the hydroxyl radical adducts (1 and 2). This assignment is supported by the intermediate spectrum (λmax at 280nm) from the reaction of sulfate radical anion (SO4-) (k2=3.20×109dm3mol-1s-1) which is a one electron oxidant. It is thus demonstrated that the combination of both pulse radiolysis and the product estimation using LC-MS/MS is ideal in probing the complete mechanism which is very important in the mineralization reactions using Advanced Oxidation Processes. © 2012 Elsevier Ltd.


Subhadra Devi P.K.,Mahatma Gandhi University | Subhadra Devi P.K.,P.A. College | Unnikrishnan K.,Mahatma Gandhi University | Unnikrishnan K.,Nss Hindu College | Venugopal C.,Mahatma Gandhi University
Journal of Atmospheric and Solar-Terrestrial Physics | Year: 2011

The enhancement and depletions of the total electron content (TEC) on storm days from the quiet day values are analysed for different seasons and solar activity conditions at Palehua, a low latitude station, during the period 1980-1991.Considering the dependence of enhancement in storm time TEC for positive storms with solar radio flux F10.7, a positive correlation is observed in winter and equinox. For negative storms, the correlation of depletion in storm time TEC with solar radio flux F10.7 is positive in equinox, but no such dependency is observed in summer. The intensity of storm (Ap) is found to be negatively correlated with enhancement in storm time TEC, in equinox, for positive storms. But no such dependency is shown in winter. For negative storms, the depletion in storm time TEC shows no dependency with Ap in equinox, but shows positive correlation in summer. Considering the dependence of enhancement of TEC on Dst max, a positive correlation is observed in winter and equinox for positive storms. For negative storms, the correlation between depletion in storm time TEC and Dst max is found to be positive for summer and equinox. A similar correlation study is carried out for time delay (τ) of occurrence of maximum enhancement and depletion of TEC. The maximum and minimum percentage probability range of ΔTEC and τ are also analysed by considering the data seasonally. © 2011 Elsevier Ltd.


Unnikrishnan K.,NSS Hindu College | Unnikrishnan K.,Mahatma Gandhi University
Journal of Atmospheric and Solar-Terrestrial Physics | Year: 2012

Nonlinear dynamical models of the magnetosphere derived from observational time series data using phase space reconstruction techniques have yielded new advances in the understanding of its dynamics. Considering the solar wind-magnetosphere interaction to be a natural input-output system its dynamical features can be reconstructed on the storm time scale by using the method of time delay embedding. Here, fourteen magnetic storm intervals belonging to low/moderate and high solar activity periods are considered and a suitable state space model has designed by performing training and validation tests, for which dawn to dusk electric field (VBz) is chosen as the input, and the AL time series as the output. The percentage of the output variations that is reproduced by the model is termed as fit_model and a higher number of fit_model means a better model. The number of components m used in the state space model is varied from 1-9 and the best prediction is obtained when m=4. The fit_model values of time series used for validation are 67.96, 67.2, 72.44, and 70.89, with m=4. In the present study most of the storms considered are having D stmax in between -100 and -300nT, and they can be predicted well with this procedure. To reveal the prediction capability of the proposed state space model the 30 steps ahead outputs for the storm events are generated, which reasonably reproduce the observed values. © 2011 Elsevier Ltd.


Sunil Paul M.M.,Mahatma Gandhi University | Aravind U.K.,Mahatma Gandhi University | Pramod G.,Nss Hindu College | Saha A.,UGC-DAE Consortium for Scientific Research | Aravindakumar C.T.,Mahatma Gandhi University
Organic and Biomolecular Chemistry | Year: 2014

Oxidative destruction and mineralization of emerging organic pollutants by hydroxyl radicals (OH) is a well established area of research. The possibility of generating hazardous by-products in the case of OH reaction demands extensive investigations on the degradation mechanism. A combination of pulse radiolysis and steady state photolysis (H2O2/UV photolysis) followed by high resolution mass spectrometric (HRMS) analysis have been employed to explicate the kinetic and mechanistic features of the destruction of theophylline, a model pharmaceutical compound and an identified pollutant, by OH in the present study. The oxidative destruction of this molecule, for intermediate product studies, was initially achieved by H2O 2/UV photolysis. The transient absorption spectrum corresponding to the reaction of OH with theophylline at pH 6, primarily caused by the generation of (T8-OH), was characterised by an absorption band at 330 nm (k2 = (8.22 ± 0.03) × 109 dm3 mol-1 s-1). A significantly different spectrum (λmax: 340 nm) was observed at highly alkaline pH (10.2) due to the deprotonation of this radical (pKa ∼ 10.0). Specific one electron oxidants such as sulphate radical anions (SO4 -) and azide radicals (N 3) produce the deprotonated form (T(-H)) of the radical cation (T+) of theophylline (pKa 3.1) with k2 values of (7.51 ± 0.04) × 109 dm3 mol-1 s-1 and (7.61 ± 0.02) × 109 dm3 mol-1 s-1 respectively. Conversely, oxide radicals (O -) react with theophylline via a hydrogen abstraction protocol with a rather slow k2 value of (1.95 ± 0.02) × 109 dm3 mol-1 s-1. The transient spectral studies were complemented by the end product profile acquired by HRMS analysis. Various transformation products of theophylline induced by OH were identified by this technique which include derivatives of uric acids (i, iv & v) and xanthines (ii, iii & vi). Further breakdown of the early formed product due to OH attack leads to ring opened compounds (ix-xiv). The kinetic and mechanistic data furnished in the present study serve as a basic frame work for the construction of OH induced water treatment systems as well as to understand the biological implications of compounds of this kind. © the Partner Organisations 2014.


Remanan R.,Mahatma Gandhi University | Unnikrishnan K.,Mahatma Gandhi University | Unnikrishnan K.,Nss Hindu College
Journal of Atmospheric and Solar-Terrestrial Physics | Year: 2013

The present study is an analysis of the effects of storm sudden commencements (SSC) on geomagnetic field components H, D and Z during 1995-2001 with the data of five low-latitude stations in India, namely Pondicherry (PND, 2.85°N, 79.92°E), Visakhapatnam (VSK, 8.34°N, 83.32°E), Alibag (ABG, 10.19°N, 72.87°E), Nagpur (NGP, 12.12°N, 79.08°E) and Ujjain (UJJ, 14.43°N, 75.78°E). The characteristics of geomagnetic H, D and Z field components are studied under various geophysical conditions. For both quiet and storm times, the maximum amplitude of H is obtained at PND and it decreases with increase in latitude for the period 1995-2001.The amplitude of D component is larger at VSK and smaller at UJJ for both quiet and storm periods during 1995-2001. It is clear that the storm time Hmin values show no variation with solar activity at 2.85°N (PND). However, all the other latitudes in the present study such as at 8.34°N, 10.19°N, 12.12°N and 14.43°N, storm time Hmin values decrease with increase of S10.7. The values of δHmin shows positive correlations with solar activity, for the stations PND, VSK, ABG, NGP and UJJ, considered in the present study. The value of correlation coefficient obtained between H and interplanetary magnetic field and H and interplanetary electric field increases with increase of solar activity. The values of δHmin (δHmin=Hstorm-Hquiet) increase with increase of solar activity and correlate well with Dstmax for the five low-latitudes studied here. © 2013 Elsevier Ltd.


Remya R.,Mahatma Gandhi University | Unnikrishnan K.,Mahatma Gandhi University | Unnikrishnan K.,Nss Hindu College
Journal of Atmospheric and Solar-Terrestrial Physics | Year: 2010

In the present study, the deterministic chaotic behaviour of interplanetary magnetic field (IMF) under various geomagnetic conditions of low and high solar active periods was analyzed, using the time series of IMF B and Bz, by employing chaotic quantifiers like, Lyapunov exponent, Tsallis entropy, correlation dimension, and non-linear prediction error. We have investigated whether the chaotic behaviour of interplanetary magnetic field would modify, when it produces major geomagnetic storms, and how it depends on the phase of solar activity. The yearly average values of Lyapunov exponent for the time series of IMF B and Bz, show solar flux dependence, whereas those values of entropy, correlation dimension and non-linear prediction error had no significant solar flux dependence. The yearly average values of entropy for quiet periods are higher compared to those values for major storm periods belonging to low/high solar active conditions, for both the time series B and Bz. © 2010 Elsevier Ltd.


Subhadra Devi P.K.,Mahatma Gandhi University | Subhadra Devi P.K.,P.A. College | Unnikrishnan K.,Mahatma Gandhi University | Unnikrishnan K.,Nss Hindu College
Advances in Space Research | Year: 2014

In this study, 30 storm sudden commencement (SSC) events during the period 2001-2007 for which daytime vertical E × B drift velocities from JULIA radar, Jicamarca (geographic latitude 11.91 S, geographic longitude 283.11 E, 0.81 N dip latitude), Peru and ΔH component of geomagnetic field measured as the difference between the magnitudes of the horizontal (H) components between two magnetometers deployed at two different locations Jicamarca (geographic latitude 11.91 S, geographic longitude 283.11 E, 0.81 N dip latitude) and Piura (geographic latitude 5.21 S, geographic longitude 279.41 E, 6.81 N dip latitude), in Peru, were considered. It is observed that a positive correlation exists between peak value of daytime vertical E × B drift velocity and peak value of ΔH for the three consecutive days of SSC. A qualitative analysis made after selecting the peak values of daytime vertical E × B drift velocity and ΔH showed that 57% of the events have daytime vertical E × B drift velocity peak in the magnitude range 20-30 m/s and 63% of the events have ΔH peak in the range 80-100 nT. The maximum probable (45%) range of time of occurrence of peak value for both vertical E × B drift velocity and ΔH during the daytime hours were found to be the same, i.e.; 10:00-12:00 LT. A strong positive correlation was also found to exist between the daytime vertical E × B drift velocity and ΔH for all the three consecutive days of SSC, for all the events considered. To establish a quantitative relationship between day time vertical E × B drift velocity and ΔH, linear and polynomial (order 2 and 3) regression analysis (Least Square Method (LSM)) were carried out, considering the fully disturbed day after the commencement of the storm as 'disturbed period' for the SSC events selected for analysis. The formulae indicating the relationship between daytime vertical E × B drift velocity and ΔH, for the 'disturbed periods', obtained through the regression analysis were verified using the JULIA radar observed E × B drift velocity for 3 selected events. Root Mean Square (RMS) error analysis carried out for each case suggest that polynomial regression (order 3) analysis provides a better agreement with the observations from among the linear, polynomial (order 2 and 3) analysis. © 2014 COSPAR. Published by Elsevier Ltd. All rights reserved.


Unnikrishnan K.,NSS Hindu College | Unnikrishnan K.,Mahatma Gandhi University
Journal of Atmospheric and Solar-Terrestrial Physics | Year: 2014

Present work is the first attempt to predict horizontal component of earth's magnetic field (. H) and range in H (δ. H) over Indian sector by considering the stations, namely, Trivandrum, Pondicherry, Visakhapatnam, and Nagpur, using the concept of neural network (NN). Through training procedure, solar flux (. F10.7), latitude, longitude, day of the year, local time, Ap index, IMF Bz, and ion number density are identified as the optimum choice of input parameters, whereas the inclusion of solar wind pressure and velocity has not significantly improved the performance of the model. Thus an appropriate neural network model, NSSHC has been developed with 12 hidden neurons and 500 iterations to predict H component and range in H (δ. H) during the period 1996-2001, to capture diurnal, seasonal, latitudinal, magnetic and solar activity effects. © 2014 Elsevier Ltd.


PubMed | Mahatma Gandhi University, University of Paris Descartes, Nss Hindu College and Korea Advanced Institute of Science and Technology
Type: Journal Article | Journal: Journal of mass spectrometry : JMS | Year: 2015

This study reports an energy-resolved mass spectrometric (ERMS) strategy for the characterization of position isomers derived from the reaction of hydroxyl radicals (()OH) with diphenhydramine (DPH) that are usually hard to differentiate by other methods. The isomer analogues formed by ()OH attack on the side chain of DPH are identified with the help of a specific fragment ion peak (m/z 88) in the collision-induced dissociation (CID) spectrum of the protonated molecule. In the negative ion mode, the breakdown curves of the deprotonated molecules show an order of stability (supported by density functional theory (DFT) calculations) ortho>meta>para of the positional isomers formed by the hydroxylation of the aromatic ring. The gas phase stability of the deprotonated molecules [M-H](-) towards the benzylic cleavage depends mainly on the formation of intramolecular hydrogen bonds and of the mesomeric effect of the phenol hydroxyl. The [M-H](-) molecules of ortho and meta isomers result a peak at m/z 183 with notably different intensities because of the presence/absence of an intramolecular hydrogen bonding between the OH group and C9 protons. The ERMS approach discussed in this report might be an effective replacement for the conventional methods that requires very costly and time-consuming separation/purification methods along with the use of multi-spectroscopic methods.

Loading Nss Hindu College collaborators
Loading Nss Hindu College collaborators