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Dive into the research topics where B. Chandar Shekar is active.

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Featured researches published by B. Chandar Shekar.


Thin Solid Films | 1999

Growth, structure, dielectric and AC conduction properties of solution grown PVA films

B. Chandar Shekar; V. Veeravazhuthi; S. Sakthivel; D. Mangalaraj; Sa. K. Narayandass

Abstract Polyvinyl alcohol (PVA) films were deposited on pre-cleaned glass substrates using an isothermal immersion technique. Sandwich structures of the type Al-PVA-Al were formed to study the dielectric and conduction properties of PVA films. Aluminium electrodes were deposited by vacuum evaporation method. Thicknesses ( d ) of the dielectric films were measured by an electronic linear thickness measuring instrument (Tesatronic TTD20 model) and a gravimetric method and cross checked by a capacitance method. The dependence of the thickness of the PVA films on the immersion time, concentration and temperature of the solution had been studied. From the X-ray diffraction studies the structure of the deposited film was found to be amorphous. The dielectric properties were studied in the frequency range 1–30 kHz at various temperatures in the range 303–423 K. The capacitance, though dependent on frequency and temperature, was found to be almost invariant at room temperature for all frequencies. The dielectric constant e ′ of the films was found to be increasing with increase in thickness of the film. The loss factor e ″ was found to be increasing with increase in temperature up to the glass transition temperature ( T g ) and decreasing above that ( T g ). From AC conduction studies it was confirmed that the mechanism responsible for conduction is mostly due to ionic hopping. The films showed very high transmittance in the visible to near IR region.


European Polymer Journal | 1997

Structure, dielectric, ac and dc conduction properties of acid doped polyaniline films

S. Sakthivel; B. Chandar Shekar; D. Mangalaraj; Sa. K. Narayandass; S. Venkatachalam; P.V. Prabhakaran

Abstract Capacitors with Al-pani (CH3SO3H)-Al sandwich film structure were fabricated. The top and bottom aluminium electrodes were deposited by vacuum evaporation and the pani (CH3SO3H) film deposited by a solution casting method. An X-ray diffractogram indicates the amorphous nature of the polymer films. The thicknesses of the films were measured by capacitance, weighing and Rutherford back scattering (RBS) methods. Annealing, dielectric and AC conduction properties were studied in the frequency range 10 kHz–10 MHz for various temperatures (303–423 K). DC conduction studies were made for these films in the temperature range 303–443 K. The capacitance of the film decreases with increasing frequency. AC conduction studies suggest that hopping of polarons are responsible for conduction. DC conduction studies reveal that the Poole-Frenkel type of conduction is predominant at high fields.


Journal of Radiation Research and Applied Sciences | 2014

Evaluation of radionuclides in the terrestrial environment of Western Ghats

P. K. Manigandan; B. Chandar Shekar

Abstract The activity concentration of naturally occurring radionuclides in soil samples of an elevated radiation background area of Western Ghats were determined using gamma-ray spectrometry with the aim of evaluating the environmental radioactivity. The annual effective dose equivalent and the radiation hazard indices from the soil activity were estimated to reduce the harmful effects of gamma radiation to the population dwelling in the area. The activity concentrations of 232Th and average outdoor terrestrial gamma dose rate were found to be higher than the world average, this may affect Western Ghats environment in general. Therefore, the radiological risks to the general population from ionizing radiation from the naturally occurring radionuclides in the soil are considered to be significant. However, other radiological hazard indices were found to be within permissible limits.


Journal of Environmental Radioactivity | 2014

Uptake of some radionuclides by woody plants growing in the rainforest of Western Ghats in India

P. K. Manigandan; B. Chandar Shekar

Transfer of the naturally occurring radionuclides (238)U, (232)Th, and (40)K, and the fallout radionuclide (210)Po to different wild plant species in the rainforest of Western Ghats was analyzed. A number of physiologically different plants from the top storey and understorey, such as shrubs and epiphytes, were compared. The concentrations of these radionuclides in the plants and soil were measured using a gamma ray spectrometer and an alpha counter, and were found to vary widely within plants and between species. The soil-plant ratios also varied between species while Elaeocarpus oblongus and epiphytic plants exhibited preferential uptake of these radionuclides. As a result, the dust particles trapped in the root systems of epiphytes could be used as bioindicators of fallout radionuclides in the Western Ghats.


Journal of Radioanalytical and Nuclear Chemistry | 2015

Leaves of woody plants as bio-indicators of radionuclides in forest ecosystems

P. K. Manigandan; B. Chandar Shekar

Leaves of Evodia roxburghiana and Elaeocarpus oblongus, and their associated soil samples, were collected from Western Ghats, India, and analysed as bio-indicators of radionuclides. Concentrations of 40K and 210Po in leaves and soils were measured using a gamma ray spectrometer and an alpha counter. The transfer factor (TF) of these radionuclides to the plants from the underlying soil was calculated. From a careful analysis of the results, leaves of E. roxburghiana and E. oblongus are identified as bioindicators to monitor fallout radionuclides. From the seasonal study, it was found that mean values of TF were significantly higher in their earlier days of life than when they were getting mature.


Archive | 2015

Root Uptake/Foliar Uptake in a Natural Ecosystem

P. K. Manigandan; B. Chandar Shekar; D. Khanna

The leaves of native tree species (sylva) and their associated soil samples were collected from Western Ghats, India, and analyzed to comprehend the mechanism of radionuclide uptake. For comparison, prominent tree species of the region, Elaeocarpus oblongus and Michelia nilagirica (tall trees), Vaccinium neilgherrense and Viburnum hebanthum (short trees), Lasianthus coffeoiaes and Hedyotis stylosa (bushes), and Cymbidium aloifolium (an orchid), were sampled, and the concentration of radionuclides in the plant and soil was measured using a gamma-ray spectrometer and an alpha counter selected for analysis. The activity concentration ratio (CR) of radionuclides in the plants from the underlying soil was calculated and found to vary widely within plants and between plants. CR values indicate the variation of radionuclide accumulation in various species, while E. oblongus, Evodia roxburghiana, and C. aloifolium exhibited preferential uptake of radionuclides. The dust particles trapped in the root system of C. aloifolium could be used as a bioindicator to monitor fallout radionuclides in the Western Ghats.


Agroforestry Systems | 2018

Soil impact and radiation dose to native plants in forest ecosystem

P. K. Manigandan; B. Chandar Shekar

A radiation dose assessment model was applied to determine naturally occurring radionuclides 238U, 210Po and 232Th in trees like Elaeocarpus oblongus, Evodia roxburghiana (Juice of the leaves that are used to treat fever), Vaccinium neilgherrense, Viburnum hebanthum and Michelia nilagirica and shrubs like Lasianthus coffeoiaes and Hedyotis stylosa in the agroforests of the Western Ghats, India and these areas were used for different agroforestry models of land development systems. The concentration of radionuclides in the biota and corresponding soil was measured using a gamma ray spectrometer and an alpha counter. The concentration ratios of these radionuclides varied substantially between the species, and E. oblongus showed a preferential uptake of all the radionuclides and hence useful for bio-indication of radionuclides in such soils. ERICA assessment tool was employed to provide an assessment of the potential doses to biota’s growing in agro forest E. oblongus appears to be much prone to radiation absorption from the dose risk point of view. The annual effective dose (AED) due to ingestion of these radionuclides in E. roxburghiana was also estimated, and was found to be lower than the world average.


Radiochimica Acta | 2017

Soil depth profiles and radiological assessment of natural radionuclides in forest ecosystem

P. K. Manigandan; B. Chandar Shekar

Abstract We measured the distribution of three naturally occurring radionuclides, 238U, 232Th, and 40K, in soil samples collected from a rainforest in the Western Ghats of India. For each surface sample, we calculated average activity concentration, outdoor terrestrial γ dose rate, annual effective dose equivalent (AEDE), and radiation hazard index. The activity concentrations of surface samples were randomly distributed over space, but differed slightly with different soil depths. The concentration of 232Th and the average terrestrial γ dose rates were slightly higher than the world averages, so slightly high γ radiation appears to be a general characteristic of the Western Ghats. However, all radiological hazard indices were within the limits proposed by the International Commission on Radiological Protection. The results reported here indicate that, except for 232Th, the naturally occurring radionuclides in the forest soils of the Western Ghats were within the ranges specified by United Nations Scientific Committee on the Effects of Atomic Radiation for undisturbed virgin soils.


Archive | 2015

Assessment of Radioactivity in Forest and Grassland Ecosystems

P. K. Manigandan; B. Chandar Shekar; D. Khanna

Naturally occurring radionuclides were investigated in soil samples collected from a tropical rainforest in the Western Ghats, India. For comparison, a number of soil samples from nearby meadows (open grassland) were also studied using gamma-ray spectrometry. Average values of the activity concentration of radionuclides, outdoor gamma-ray dose rate, annual effective dose equivalent, and radiation hazard indices from soil activity were estimated. Significant differences were found between the soils from the forest and meadow sites: the meadow sites contained higher natural radionuclide concentrations than the forest sites. The activity concentration of 232Th and average outdoor gamma-ray dose rates were found to be higher than the global average in both ecosystems, so high gamma radiation appears to affect the Western Ghats’ environment in general. Therefore, the radiological risks to the general population from ionizing radiation from the naturally occurring radionuclides in the soil are considered to be significant. However, other radiological hazard indices that were calculated were within acceptable limits.


Radioprotection | 2015

Risk assessment of radioactivity in soils of forest and grassland ecosystems of the Western Ghats, India

P. K. Manigandan; B. Chandar Shekar

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