Showing papers by "Cochin University of Science and Technology published in 2012"

UV-visible photoluminescence of TiO2 nanoparticles prepared by hydrothermal method.

Abstract: TiO2 colloidal nanoparticles and nanocrystals are prepared by hydrolysis of titanium isopropoxide employing a surfactant-free synthetic hydrothermal method. The synthesized samples are characterized by X-ray diffraction (XRD), HRTEM and FTIR. The XRD study confirms that the size of the colloidal nanoparticle is around 4 nm which the HRTEM analysis indicates the sizes of the colloidal nanoparticles are in the range of 2.5 nm. The fluorescence property of the TiO2 colloidal nanoparticles studied by the emission spectrum confirms the presence of defect levels caused by the oxygen vacancies. We have observed new emission bands at 387 nm,421 nm, 485 nm, 530 nm and 574 nm wavelengths, first one (387 nm) being emission due to annihilation of excitons while remaining four could be arising from surface states. The emission spectrum of annealed nanocrystallites is also having these four band emissions. It is observed that the surface state emission basically consists of two categories of emission.

Hydrogeochemical study of shallow carbonate aquifers, Rameswaram Island, India.

Abstract: Groundwater quality assessment has been carried out based on physicochemical parameters (pH, EC, TDS, CO3, HCO3, Cl, SO4, PO4, NO2, Ca+2, Mg+2, Na+ and K+) and metal concentration in the Rameswaram Island from 25 bore wells. The Langelier Saturation Index of the groundwater shows positive values (63% samples) with a tendency to deposit the CaCO3 in the majority of water samples. Scatter plot (Ca + Mg/HCO3) suggests carbonate weathering process, which is the main contributor of Ca2+, Mg2+ and HCO3 ions to the water. Gibbs diagram suggests rock–water interaction dominance and evaporation dominance which are responsible for the change in the quality of water in the study area. NaCl and mixed CaNaHCO3 facies are two main hydrogeochemical facies of groundwater. Mathematical calculations and graphical plots of geochemical data reveal that the groundwater of Rameswaram Island is influenced by natural weathering of rocks, anthropogenic activities and seawater intrusion due to over exploitation. Weathering and dissolution of carbonate and gypsum minerals also control the concentration of major ions (Ca+2, Mg+2, Na+ and K+) in the groundwater. The nutrient concentration of groundwater is controlled to a large extent by the fertilizers used in agricultural lands and aquaforms. Comparison of geochemical data shows that majority of the groundwater samples are suitable for drinking water and irrigation purposes.

Optical Power Limiting in Fluorinated Graphene Oxide: An Insight into the Nonlinear Optical Properties

Abstract: Fluorination of carbon nanomaterials has many advantages due to the unique nature of the carbon–fluorine (C–F) bond. In this work, we report the optical power limiting properties of fluorinated graphene oxide (F–GO) using the optical z-scan technique. In addition, we used the photoacoustic technique to gain insight into the nonlinear processes involved in the optical limiting of samples. The photoacoustic technique enabled us to confirm that optical limiting observed in F–GO at low fluence arises from nonlinear absorption, while that at higher fluence is due to nonlinear scattering. Moreover, we found that F–GO has high nonlinear absorption and nonlinear scattering and its optical limiting threshold is about an order of magnitude better than that of graphene oxide (GO).

Luteolin Inhibits Human Prostate Tumor Growth by Suppressing Vascular Endothelial Growth Factor Receptor 2-Mediated Angiogenesis

Abstract: Angiogenesis, the formation of new blood vessels from pre-existing vascular beds, is essential for tumor growth, invasion, and metastasis. Luteolin is a common dietary flavonoid found in fruits and vegetables. We studied the antiangiogenic activity of luteolin using in vitro, ex vivo, and in vivo models. In vitro studies using rat aortic ring assay showed that luteolin at non-toxic concentrations significantly inhibited microvessel sprouting and proliferation, migration, invasion and tube formation of endothelial cells, which are key events in the process of angiogenesis. Luteolin also inhibited ex vivo angiogenesis as revealed by chicken egg chorioallantoic membrane assay (CAM) and matrigel plug assay. Gelatin zymographic analysis demonstrated the inhibitory effect of luteolin on the activation of matrix metalloproteinases MMP-2 and MMP-9. Western blot analysis showed that luteolin suppressed VEGF induced phosphorylation of VEGF receptor 2 and their downstream protein kinases AKT, ERK, mTOR, P70S6K, MMP-2, and MMP-9 in HUVECs. Proinflammatory cytokines such as IL-1β, IL-6, IL-8, and TNF-α level were significantly reduced by the treatment of luteolin in PC-3 cells. Luteolin (10 mg/kg/d) significantly reduced the volume and the weight of solid tumors in prostate xenograft mouse model, indicating that luteolin inhibited tumorigenesis by targeting angiogenesis. CD31 and CD34 immunohistochemical staining further revealed that the microvessel density could be remarkably suppressed by luteolin. Moreover, luteolin reduced cell viability and induced apoptosis in prostate cancer cells, which were correlated with the downregulation of AKT, ERK, mTOR, P70S6K, MMP-2, and MMP-9 expressions. Taken together, our findings demonstrate that luteolin inhibits human prostate tumor growth by suppressing vascular endothelial growth factor receptor 2-mediated angiogenesis.

Chipless RFID Tag Using Multiple Microstrip Open Stub Resonators

Abstract: A novel compact RFID tag employing open stubs in a microstrip transmission line is proposed. The prototype of the tag is fabricated on a substrate of dielectric constant 4.4 and loss tangent 0.0018. The tag consists of microstrip open stub resonators and cross polarized transmitting and receiving disc monopole antennas. A prototype of 8 bit data encoded tag is demonstrated in this communication. Method for enhancing the performance of the RFID tag is also proposed. Magnitude or group delay response can be used to decode the tag informations.

A Novel Slotless Halbach-Array Permanent-Magnet Brushless DC Motor for Spacecraft Applications

Abstract: This paper presents the design and analysis of a novel machine family-the enclosed-rotor Halbach-array permanent-magnet brushless dc motors for spacecraft applications. The initial design, selection of major parameters, and air-gap magnetic flux density are estimated using the analytical model of the machine. The proportion of the Halbach array in the machine is optimized using finite element analysis to obtain a near-trapezoidal flux pattern. The machine is found to provide uniform air-gap flux density along the radius, thus avoiding circulating currents in stator conductors and thereby reducing torque ripple. Furthermore, the design is validated with experimental results on a fabricated machine and is found to suit the design requirements of critical spacecraft applications.

Optimization of Lignin Peroxidase, Manganese Peroxidase, and Lac Production from Ganoderma lucidum Under Solid State Fermentation of Pineapple Leaf

Abstract: This study was undertaken to isolate ligninase-producing white-rot fungi for use in the extraction of fibre from pineapple leaf agriwaste. Fifteen fungal strains were isolated from dead tree trunks and leaf litter. Ligninolytic enzymes (lignin peroxidase (LiP), manganese peroxidase (MnP), and laccase (Lac)), were produced by solid-state fermentation (SSF) using pineapple leaves as the substrate. Of the isolated strains, the one showing maximum production of ligninolytic enzymes was identified to be Ganoderma lucidum by 18S ribotyping. Single parameter optimization and response surface methodology of different process variables were carried out for enzyme production. Incubation period, agitation, and Tween-80 were identified to be the most significant variables through Plackett-Burman design. These variables were further optimized by Box-Behnken design. The overall maximum yield of ligninolytic enzymes was achieved by experimental analysis under these optimal conditions. Quantitative lignin analysis of pineapple leaves by Klason lignin method showed significant degradation of lignin by Ganoderma lucidum under SSF.

Effect of vitamin D3 in reducing metabolic and oxidative stress in the liver of streptozotocin-induced diabetic rats.

Abstract: Diabetes mellitus is a growing health problem worldwide and is associated with severe liver complications. The aim of the present study is to analyse the status of metabolic and free-radical-scavenging enzymes and second messengers in the liver of streptozotocin (STZ)-induced diabetic rats, and to determine the hepatoprotective role of vitamin D(3). All studies were performed using the liver of adult male Wistar rats. Gene expression studies were carried out using real-time PCR with specific probes. Second messenger levels were determined using (3)H-labelled Biotrak assay kits, and glucose uptake assay with D-[(14)C]glucose. The present results show that there was a decrease in hepatic glucose uptake, malate dehydrogenase activity, glycogen content, inositol triphosphate (IP(3)) and cyclic GMP levels, and superoxide dismutase, glutathione peroxidase, phospholipase C, cyclic AMP-responsive element-binding protein, vitamin D receptor (VDR) and insulin receptor (INSR) gene expression in the diabetic rats when compared with the controls (all P < 0·05), while cyclic AMP levels and GLUT2 expression were increased (P < 0·05). Treatment of the diabetic rats with vitamin D(3) and insulin reversed the altered parameters to near control values. In conclusion, the data suggest a novel role of vitamin D(3) in restoring impaired liver metabolism in STZ-induced diabetic rats by regulating glucose uptake, storage and metabolism. We demonstrated that the restoring effect of vitamin D(3) is mediated through VDR modulation, thereby improving signal transduction and controlling free radicals in the liver of diabetic rats. These data suggest a potential role for vitamin D(3) in the treatment of diabetes-associated hepatic complications.

Toxic Metals Enrichment in the Surficial Sediments of a Eutrophic Tropical Estuary (Cochin Backwaters, Southwest Coast of India)

Abstract: Concentrations and distributions of trace metals (Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, and Zn) in surficial sediments of the Cochin backwaters were studied during both monsoon and pre-monsoon periods. Spatial variations were in accordance with textural charaterstics and organic matter content. A principal component analysis distinguished three zones with different metal accumulation capacity: (i) highest levels in north estuary, (ii) moderate levels in central zone, and (iii) lowest levels in southern part. Trace metal enrichments are mainly due to anthropogenic contribution of industrial, domestic, and agricultural effluents, whose effect is enhanced by settling of metals due to organic flocculation and inorganic precipitation associated with salinity changes. Enrichments factors using Fe as a normalizer showed that metal contamination was the product of anthropogenic activities. An assessment of degree of pollution-categorized sediments as moderately polluted with Cu and Pb, moderately-to-heavily polluted with Zn, and heavily-to-extremely polluted with Cd. Concentrations at many sites largely exceed NOAA ERL (e.g., Cu, Cr, and Pb) or ERM (e.g., Cd, Ni, and Zn). This means that adverse effects for benthic organisms are possible or even highly probable.

Dynamic cumulative residual Renyi's entropy

Abstract: Recently, cumulative residual entropy (CRE) has been found to be a new measure of information that parallels Shannon's entropy (see Rao et al. [Cumulative residual entropy: A new measure of information, IEEE Trans. Inform. Theory. 50(6) (2004), pp. 1220–1228] and Asadi and Zohrevand [On the dynamic cumulative residual entropy, J. Stat. Plann. Inference 137 (2007), pp. 1931–1941]). Motivated by this finding, in this paper, we introduce a generalized measure of it, namely cumulative residual Renyi's entropy, and study its properties. We also examine it in relation to some applied problems such as weighted and equilibrium models. Finally, we extend this measure into the bivariate set-up and prove certain characterizing relationships to identify different bivariate lifetime models.

Is Occurrence of Harmful Algal Blooms in the Exclusive Economic Zone of India on the Rise

Abstract: Occurrence, increase in frequency, intensity and spatial coverage of harmful algal blooms during the past decade in the EEZ of India are documented here. Eighty algal blooms were recorded during the period 1998–2010. Of the eighty algal blooms, 31 blooms were formed by dinoflagellates, 27 by cyanobacteria, and 18 by diatoms. Three raphidophyte and one haptophyte blooms were also observed. Potentially toxic microalgae recorded from the Indian waters were Alexandrium spp., Gymnodinium spp. Dinophysis spp., Coolia monotis, Prorocentrum lima, and Pseudo-nitzschia spp. Examination of available data from the literature during the last hundred years and in situ observations during 1998–2010 indicates clear-cut increase in the occurrence of HABs in the Indian EEZ.

Saturable and reverse saturable absorption in aqueous silver nanoparticles at off-resonant wavelength

Abstract: Silver nano-colloid was prepared by chemical reduction method and its nonlinear absorption properties were investigated by using open aperture z-scan experiment with nanosecond laser pulses operating at 532 nm. Interestingly, a switch over from saturable absorption to reverse saturable absorption was observed when the input intensity is increased from 28.1 to 175.8 MW/cm2. The underlying mechanism responsible for the observed switching behaviour is the interplay between ground state plasmon band bleaching and excited state absorption. Theoretical fitting was done by using a model in which nonlinear absorption coefficient as well as saturation intensity are incorporated.

Hybrid Multiferroic Nanostructure with Magnetic−Dielectric Coupling

Abstract: The development of methods to economically synthesize single wire structured multiferroic systems with room temperature spin–charge coupling is expected to be important for building next-generation multifunctional devices with ultralow power consumption. We demonstrate the fabrication of a single nanowire multiferroic system, a new geometry, exhibiting room temperature magnetodielectric coupling. A coaxial nanotube/nanowire heterostructure of barium titanate (BaTiO3, BTO) and cobalt (Co) has been synthesized using a template-assisted method. Room temperature ferromagnetism and ferroelectricity were exhibited by this coaxial system, indicating the coexistence of more than one ferroic interaction in this composite system.

Indoleamines and calcium enhance somatic embryogenesis in Coffea canephora P ex Fr

Abstract: Melatonin (MEL) and serotonin (SER) are important indoleamines that are involved in neural transmission in mammalian cells. They are also known to be present in various genera of plants. The role (s) of these indoleamines in plants are not well known. In this study, the effects of SER, MEL, calcium, and calcium ionophore (A23187), a calcium channel activator, on somatic embryogenesis in Coffea canephora have been investigated. Adding 100 μM of either SER or MEL to ½ strength Murashige and Skoog (MS) medium and 0.93 μM kinetin (KN) has resulted in enhanced induction of somatic embryogenesis, 85 ± 3 and 62 ± 6 embryos/callus, respectively. In the presence of either 5 mM calcium or 100 μM calcium ionophore A23187, number of somatic embryos/callus is also increased, with 56 ± 4 and 118 ± 10 somatic embryos/callus, respectively, compared to 25 ± 3 embryos/callus for control. The presence of 5 mM calcium chloride along with either 100 μM SER or 100 μM MEL, respectively, have also promoted somatic embryogenesis with induction of 105 ± 6 and 78 ± 2 somatic embryos/callus. While, addition of calcium ionophore A23187 along with either 100 μM SER or 100 μM MEL have produced 155 ± 12 or 135 ± 8 embryos/callus, respectively. In contrast, addition of such indoleamine inhibitors as 40 μM p-chlorophenylalanine (p-CPA), 20 μM fluoexitine hydrochloride (prozac), 1 mM verapamil hydrochloride (calcium channel blocker), and 1 mM ethylene glycol-bis (β-amino ethylether)-N, N, N′, N′-tetra acetic acid (EGTA) (a calcium chelator) individually, has inhibited induction of somatic embryos while reducing levels of endogenous pools of SER, MEL and indole-3-acetic acid (IAA) levels. Calcium imaging by laser scanning confocal microscopy (LSCM) has revealed high fluorescence intensity in callus treated with calcium and calcium ionophore A23187. Immunolocalization of SER in different tissues of C. canephora has revealed that it is localized in vascular tissues of stems, roots, and somatic embryos, as well as in endocarps (husks) of immature fruits.

Sleep quality and nocturnal hypoxaemia and hypercapnia in children and young adults with cystic fibrosis

Abstract: Objectives The aim of the study was to evaluate sleep quality and nocturnal gas exchange in patients with cystic fibrosis (CF) and to assess if sleep quality and daytime lung function could predict nocturnal hypoxaemia or hypercapnia. Study design Daytime sleepiness and objective sleep quality were evaluated by the Pittsburgh Sleep Quality Index (PSQI) and actigraphy in 25 children and 55 young adults (mean age 24±10 years, forced expiratory volume in 1 s (FEV 1 ) 41±11% predicted). Nocturnal gas exchange was assessed by pulse oximetry (SpO 2 ) and transcutaneous carbon dioxide (PtcCO 2 ) recordings. Eleven patients underwent simultaneous polysomnography (PSG). Results PSQI was 6.3±3.4 with 51% of the patients having a score >5 corresponding to significant sleep complaints. On actigraphy, sleep efficiency was impaired at 79±11% with a fragmentation index at 41±18. Mean nocturnal SpO 2 was 93±3% with 18% of the patients exhibiting >10% of night time spent with a value below 90%. Mean PtcCO 2 was 44±6 mm Hg with 47% of the patients exhibiting >10% of night time with a value >45 mm Hg. Daytime arterial blood gases correlated with nocturnal gas exchange. FEV 1 was the only lung function parameter that correlated with nocturnal SpO 2 (p 2 and PtcCO 2 accurately identified rapid eye movement sleep hypoventilation. Conclusions Patients with CF exhibit poor sleep quality that does not predict nocturnal gas exchange. Nocturnal hypoxaemia and hypercapnia can be identified by simple tools.

Dynamically evolving Mg ii broad absorption line flow in SDSS J133356.02+001229.1

Abstract: We report a dynamically evolving low-ionization broad absorption line (BAL) flow in the QSO SDSS J133356.02+001229.1 (at z_(em)∼ 0.9197). These observations are part of our ongoing monitoring of low-ionization BAL QSOs with the 2-m telescope at IUCAA Girawali Observatory (IGO). The broad Mg ii absorption with an ejection velocity of 1.7 × 10^4 km s^(−1), found in the Sloan Digital Sky Survey (SDSS) spectra, has disappeared completely in our IGO spectra. We found an emerging new component at an ejection velocity of 2.8 × 10^4 km s^(−1). During our monitoring period this component has shown strong evolution both in its velocity width and optical depth and nearly disappeared in our latest observations. Acceleration of a low-velocity component seen in SDSS spectrum to a higher velocity is unlikely as the Mg ii column densities are always observed to be higher for the new component. We argue that the observed variations may not be related to ionization changes and are consistent with absorption produced by multistreaming flow transiting across our line of sight. We find a possible connection between flux variation of the QSO and N(Mg ii) of the newly emerged component. This could mean the ejection being triggered by changes in the accretion disc or dust reddening due to the outflowing gas.

The influence of Madden – Julian Oscillation in the genesis of North Indian Ocean tropical cyclones

Abstract: Cyclonic storms having maximum winds of 34 knots and above that had genesis in north Indian Ocean have been studied with respect to the eastward passage of Madden–Julian Oscillation (MJO). In the three decades (1979–2008), there were a total of 118 cyclones reported in which 96 formed in the region chosen (0–15oN, 60oE–100oE) for the study. Although the percentage of MJO days inducing cyclogenesis is small, it is found that tropical cyclone genesis preferentially occurred during the convective phase of MJO. This accounted for 44 cyclones of the total 54 cyclones (i.e., 81.5%) formed under MJO amplitude 1 and above. The study has shown that, when the enhanced convection of MJO is over the maritime continent and the adjoining eastern Indian Ocean, it creates the highest favorable environment for cyclogenesis in the Bay of Bengal. During this phase, westerlies at 850 hPa are strong in the equatorial region south of Bay of Bengal creating strong cyclonic vorticity in the lower troposphere along with the low vertical wind shear.