Showing papers by "Cochin University of Science and Technology published in 2002"
TL;DR: Flocculation of three freshwater algae, Spirulina, Oscillatoria and Chlorella, and onebrackish alga, Synechocystis, using chitosan reduced the algal content effectively by flocculation and settling by depended on the concentration of alga.
Abstract: Flocculation of three freshwater algae, Spirulina,Oscillatoria and Chlorella, and onebrackish alga, Synechocystis, using chitosan was studiedinthe pH range 4 to 9, and chlorophyll-a concentrations inthe range 80 to 800 mg m−3, which produces aturbidity of 10 to 100 nephelometric turbidity units (NTU) in water. Chitosanreduced the algal content effectively by flocculation and settling. Theflocculation efficiency is very sensitive to pH, and reached a maximum at pH7.0for the freshwater species, but lower for the marine species. The optimalchitosan concentration that is required to effect maximum flocculation dependedon the concentration of alga. Flocculation and settling were faster whenconcentrations of chitosan higher than optimal are used. The settled algalcellsare intact and live, but will not be redispersed by mechanical agitation. Thede-algated water may be reused to produce fresh cultures of algae.
305 citations
TL;DR: Flocculation of silt in river water using chitosan was studied in the pH range 4-9, and suspended solid concentrations in the range 20-80 mg/L and the amount required for restabilisation increases with increasing concentration of suspended solids.
173 citations
TL;DR: In this article, the structural changes of polyaniline upon doping and the reduction of optical bandgap are explained on the basis of the results obtained from FTIR spectroscopic and UV-VIS absorption studies.
Abstract: Pure and iodine-doped polyaniline thin films are prepared by ac plasma polymerization technique. Doping of iodine is carried out in situ as well as by employing iodine chamber methods. The structural analyses of pure and iodine-doped polyaniline thin films are carried out by FTIR spectroscopic studies. Optical bandgaps of these films are evaluated from UV-VIS absorption studies. Direct and indirect transition energy gaps are determined from Tauc plots. The structural changes of polyaniline upon doping and the reduction of optical bandgap are explained on the basis of the results obtained from FTIR spectroscopic and UV-VIS absorption studies.
122 citations
TL;DR: In this paper, single-phase polycrystalline ceramics in the MO-La2O3-TiO2 (M = Ca, Sr, Ba) system were prepared through the solid-state ceramic route.
Abstract: Single-phase polycrystalline ceramics in the MO–La2O3–TiO2 (M = Ca, Sr, Ba) system, such as cation-deficient hexagonal perovskites CaLa4Ti4O15, SrLa4Ti4O15, BaLa4Ti4O15, and Ca2La4Ti5O18 and the orthorhombic phases CaLa4Ti5O17 and CaLa8Ti9O31, were prepared through the solid-state ceramic route. The phases and structure of the ceramics were analyzed through x-ray diffraction and scanning electron microscopy. The microwave dielectric properties of the ceramics were studied using a network analyzer. The investigated ceramics show high er in the range 42 to 54, high quality factors with Q ×f in the range 16,222 to 50,215 GHz, and low Tf in the range –25 to +6 ppm / °C. These high dielectric constant materials with high Q × f up to 50,215 GHz are suitable for applications where narrow bandwidth and extremely low insertion loss is necessary, especially at frequencies around 1.9 GHz.
118 citations
TL;DR: In this article, high conducting and transparent ZnO(n) thin films were grown by off-axis rf magnetron sputtering on amorphous silica substrates without any post-deposition annealing.
Abstract: Highly conducting and transparent ZnO : Al thin films were grown by off-axis rf magnetron sputtering on amorphous silica substrates without any post-deposition annealing. The electrical and optical properties of the films deposited at various substrate temperatures and target to substrate distances were investigated in detail. Optimized ZnO : Al films have conductivity of 2200 S cm-1 and average transmission in the visible range is higher than 85%. The conductivity and mobility show very little temperature dependence.
100 citations
TL;DR: In this article, the authors investigated the ac conductivity of polyaniline thin films in the frequency range from 100 Hz to 1 MHz and in the temperature range from 300 to 373 K.
Abstract: Polyaniline thin films were prepared by ac plasma polymerization technique. Capacitance, dielectric loss, dielectric constant and ac conductivity of these films were investigated in the frequency range from 100 Hz to 1 MHz and in the temperature range from 300 to 373 K. Capacitance and dielectric loss decreased with frequency and increased with temperature. This type of behaviour was found to be in good agreement with an existing model. The ac conductivity σ(ω) was found to vary as ωs with the index s≤1. Annealing of polyaniline thin films in high vacuum at 373 K for 1 h was found to reduce the dielectric loss. FTIR studies reveal that the aromatic ring is retained in the polyaniline thin films, which enhances the thermal stability of the polymer films.
94 citations
TL;DR: In this paper, the effect of frequency, composition and temperature on the a.c. electrical conductivity of rubber ferrite composites has been investigated and it has been shown that the conductivity increases with increase of frequency and the change is the same for both ceramic Ni1−xZnxFe2O4 and RFCs.
Abstract: The effect of frequency, composition and temperature on the a.c. electrical conductivity were studied for the ceramic, Ni1−xZnxFe2O4, as well as the filler (Ni1−xZnxFe2O4) incorporated rubber ferrite composites (RFCs). Ni1−xZnxFe2O4 (where) (bix)varies from 0 to 1 in steps of 0.2 were prepared by usual ceramic techniques. They were then incorporated into a butyl rubber matrix according to a specific recipe. The a.c. electrical conductivity (σa.c) calculations were carried out by using the data available from dielectric measurements and by employing a simple relationship. The a.c. conductivity values were found to be of the order of 10−3 S/m. Analysis of the results shows that σa.c. increases with increase of frequency and the change is same for both ceramic Ni1−xZnxFe2O4 and RFCs. σa.c increases initially with the increase of zinc content and then decreases with increase of zinc. Same behaviour is observed for RFCs too. The dependence of σa.c on the volume fraction of the magnetic filler was also studied and it was found that the a.c. conductivity of RFCs increases with increase of volume fraction of the magnetic filler. Temperature dependence of conductivity was studied for both ceramic and rubber ferrite composites. Conductivity shows a linear dependence with temperature in the case of ceramic samples.
83 citations
TL;DR: In this article, the alkylation of phenol with methanol is conducted over Ni 1− x Co x Fe 2 O 4 (x = 0, 0.2, 0., 0.5, 1.8, and 1.0) type systems prepared via low temperature route.
Abstract: The alkylation of phenol with methanol is conducted over Ni 1− x Co x Fe 2 O 4 ( x =0, 0.2, 0.5, 0.8 and 1.0) type systems prepared via low temperature route. Alkylation leads to predominantly ortho methylation of phenol, yielding o -cresol and 2,6-xylenol as the products. Under optimized conditions, the total ortho selectivity was ≥94%, regardless of the catalyst composition. Only traces of anisole is formed and hardly any other xylenol or cresol isomers are detected. Phenol conversion and the individual selectivities for o -cresol and 2,6-xylenol depend strongly on the catalyst composition. Selectivity for o -cresol was maximum for NiFe 2 O 4 (i.e., when x =0), whereas upon progressive substitution of Co 2+ ions for Ni 2+ ions, the 2,6-xylenol selectivity increases with a concomitant decrease in the o -cresol selectivity. Maximum phenol conversion and 2,6-xylenol selectivity (also total ortho selectivity) were observed over CoFe 2 O 4 ( x =1). The activity and selectivity were shown to be strongly dependent on the surface acid–base properties of the system. The influences of surface acidity, cation distribution in the spinel lattice and various reaction parameters are discussed.
74 citations
TL;DR: In this paper, the authors used x-ray diffraction and scanning electron microscopy (SEM) techniques to characterize microwave dielectric ceramics based on RETiTaO6 (RE = La, Cc, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Y, Er, Yb, Al, and In).
Abstract: Microwave dielectric ceramics based on RETiTaO6 (RE = La, Cc, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Y, Er, Yb, Al, and In) were prepared using a conventional solid-state ceramic route. The structure and microstructure of the samples were analyzed using x-ray diffraction and scanning electron microscopy techniques. The sintered samples were characterized in the microwave frequency region. The ceramics based on Ce, Pr, Nd, Sm, Eu, Gd, Tb, and Dy, which crystallize in orthorhombic aeschynite structure, had a relatively high dielectric constant and positive τf while those based on Ho, Er, and Yb, with orthorhombic euxenite structure, had a low dielectric constant and negative τf. The RETiTaO6 ceramics had a high-quality factor. The dielectric constant and unit cell volume of the ceramics increased with an increase in ionic radius of the rare-earth ions, but density decreased with it. The value of τf increased with an increase in RE ionic radii, and a change in the sign of τf occurred when the ionic radius was between 0.90 and 0.92 A. The results indicated that the boundary of the aeschynite to euxenite morphotropic phase change lay between DyTiTaO6 and HoTiTaO6. Low-loss ceramics like ErTiTaO6 (er = 20.6, Quxf = 85,500), EuTiTaO6 (r = 41.3, Quxf = 59,500), and YtiTaO6 (er = 22.1, Quxf = 51,400) are potential candidates for dielectric resonator applications.
71 citations
TL;DR: An interesting series of eight neutral ternary Co(III) complexes of 2-hydroxyacetophenone N(4)-substituted thiosemicarbazones (H2L), bidentate heterocyclic bases 2,2′-bipyridine (bipy)/1,10-phenanthroline (phen) and azide with a general formula [MLB(N3)] were prepared by means of spectroscopic methods as mentioned in this paper.
70 citations
TL;DR: In this paper, the two-dimensional light distribution of a galaxy is reconstructed using Fourier series fits to azimuthal profiles computed in concentric elliptical annuli centered on the galaxy.
Abstract: We use automated surface photometry and pattern classification techniques to morphologically classify galaxies. The two-dimensional light distribution of a galaxy is reconstructed using Fourier series fits to azimuthal profiles computed in concentric elliptical annuli centered on the galaxy. Both the phase and amplitude of each Fourier component have been studied as a function of radial bin number for a large collection of galaxy images using principal-component analysis. We find that up to 90% of the variance in many of these Fourier profiles may be characterized in as few as three principal components and that their use substantially reduces the dimensionality of the classification problem. We use supervised learning methods in the form of artificial neural networks to train galaxy classifiers that detect morphological bars at the 85%-90% confidence level and can identify the Hubble type with a 1 σ scatter of 1.5 steps on the 16 step stage axis of the revised Hubble system. Finally, we systematically characterize the adverse effects of decreasing resolution and signal-to-noise ratio on the quality of morphological information predicted by these classifiers.
TL;DR: In this paper, the first six terms of the stress field were obtained for both opening mode and shear mode loading, and it was observed that the structure of the terms other than r?1/2 and r0 are influenced by nonhomogeneity.
Abstract: Stress field for stationary cracks, aligned along the gradient, in functionally graded materials is obtained through an asymptotic analysis coupled with Westergaard's stress function approach. The first six terms of the stress field are obtained for both opening mode and shear mode loading. It is observed that the structure of the terms other than r?1/2 and r0 are influenced by the nonhomogeneity. Using this stress field, contours of constant maximum shear stress are generated and the effect of nonhomogeneity on these contours is discussed. ©2002 ASME
TL;DR: In this article, an off-line fiber optic sensor based on evanescent field absorption in a test solution formed by the reaction of nitrite compounds in water with suitable chemical reagents is described.
Abstract: A fibre optic technique for detecting trace amounts of nitrite compounds in water is described. The off-line fibre optic sensor outlined here is based on evanescent field absorption in a test solution formed by the reaction of nitrite compounds in water with suitable chemical reagents. A short unclad portion of a plastic clad silica fibre acts as the sensing region. The experimental results clearly establish the usefulness of the present technique for detecting very low concentrations of the order of 1 ppb (parts per billion) of nitrite compounds with a large dynamic range of 1–1000 ppb. Such a high sensitivity enables the present device to be used for measuring the nitrite content in drinking water.
TL;DR: In this paper, four uniformly spaced regional gravity traverses and the available seismic data across the western continental margin of India, starting from the western Indian shield extending into the deep oceanic areas of the eastern Arabian Sea, have been utilized to delineate the lithospheric structure.
Abstract: Four uniformly spaced regional gravity traverses and the available seismic data across the western continental margin of India, starting from the western Indian shield extending into the deep oceanic areas of the eastern Arabian Sea, have been utilized to delineate the lithospheric structure. The seismically constrained gravity models along these four traverses suggest that the crustal structure below the northern part of the margin within the Deccan Volcanic Province (DVP) is significantly different from the margin outside the DVP. The lithosphere thickness, in general, varies from 110–120 km in the central and southern part of the margin to as much as 85–90 km below the Deccan Plateau and Cambay rift basin in the north. The Eastern basin is characterised by thinned rift stage continental crust which extends as far as Laxmi basin in the north and the Laccadive ridge in the south. At the ocean–continent transition (OCT), crustal density differences between the Laxmi ridge and the Laxmi basin are not sufficient to distinguish continental as against an oceanic crust through gravity modeling. However, 5-6 km thick oceanic crust below the Laxmi basin is a consistent gravity option. Significantly, the models indicate the presence of a high density layer of 3.0 g/cm3 in the lower crust in almost whole of the northern part of the region between the Laxmi ridge and the pericontinental northwest shield region in the DVP, and also below Laccadive ridge in the southern part. The Laxmi ridge is underlain by continental crust upto a depth of 11 km and a thick high density material (3.0 g/cm3) between 11–26 km. The Pratap ridge is indicated as a shallow basement high in the upper part of the crust formed during rifting. The 15 –17 km thick oceanic crust below Laccadive ridge is seen further thickened by high density underplated material down to Moho depths of 24–25 km which indicate formation of the ridge along Reunion hotspot trace.
TL;DR: In this paper, a program based on G programming was developed with the aid of LabVIEW package to automate the dielectric measurements of mixed ferrites belonging to the series Mn(1−x)ZnxFe2O4 (MZF) were synthesized for different ‘x' values in steps of 0.2.
TL;DR: The role of excited state absorption in deciding the nonlinear properties of a bis-naphthalocyanine material is discussed in this article, where effective nonlinear absorption coefficient, beff and imaginary part of nonlinear susceptibility, Imðv ð3Þ Þ were obtained using open aperture Z-scan technique at the same wavelength.
TL;DR: In this article, a compact multihand planar octagonal-shaped microstrip antenna for mobile communication and blue tooth application is presented. The antenna provides sufficient isolation benveen the two operating bands and an area reduction of -29 % with respect to a circular patch operating in the same band.
Abstract: A compact multihand planar octagonal-shaped microstrip antenna simultaneously suitable for mobile communication and blue tooth application is presented The antenna provides sufficient isolation benveen the two operating bands and an area reduction of -29 % with respect to a circular patch operating in the same band © 2002 Wiley Periodicals, Inc Microwave Opt Technol Lett 33: 285-286, 2002; Pub-
TL;DR: In this paper, a good correlation was obtained between the dehydration activities of the simple ferrites and their weak plus medium strength acidities (usually of the Brnsted type) determined independently by the n-butylamine adsorption and ammonia-TPD methods.
Abstract: Preparation of simple and mixed ferrospinels of nickel, cobalt and copper and their sulphated analogues by the room temperature coprecipitation method yielded fine particles with high surface areas. Study of the vapour phase decomposition of cyclohexanol at 300 ◦ C over all the ferrospinel systems showed very good conversions yielding cyclohexene by dehydration and/or cyclohexanone by dehydrogenation, as the major products. Sulphation very much enhanced the dehydration activity over all the samples. A good correlation was obtained between the dehydration activities of the simple ferrites and their weak plus medium strength acidities (usually of the Brnsted type) determined independently by the n-butylamine adsorption and ammonia-TPD methods. Mixed ferrites containing copper showed a general decrease in acidities and a drastic decrease in dehydration activities. There was no general correlation between the basicity parameters obtained by electron donor studies and the ratio of dehydrogenation to dehydration activities. There was a leap in the dehydrogenation activities in the case of all the ferrospinel samples containing copper. Along with the basic properties, the redox properties of copper ion have been invoked to account for this added activity. © 2002 Elsevier Science B.V. All rights reserved.
TL;DR: In this paper, the authors describe the use of a new articial neural network, called the dierence boosting neural network (DBNN), for automated classication problems in astronomical data analysis and illustrate the capabilities of the network by applying it to star galaxy classication using recently released, deep imaging data.
Abstract: In this paper we describe the use of a new articial neural network, called the dierence boosting neural network (DBNN), for automated classication problems in astronomical data analysis. We illustrate the capabilities of the network by applying it to star galaxy classication using recently released, deep imaging data. We have compared our results with classication made by the widely used Source Extractor (SExtractor) package. We show that while the performance of the DBNN in star-galaxy classication is comparable to that of SExtractor, it has the advantage of signicantly higher speed and flexibility during training as well as classication.
TL;DR: In this article, the structural, electrical and optical properties of silver selenide thin films prepared by reactive evaporation were studied, showing that the as-prepared films are polycrystalline in nature.
Abstract: We study the structural, electrical and optical properties of silver selenide thin films prepared by reactive evaporation. From the Hall effect study, at room temperature we find a mobility of 2000 cm2 V−1 s−1 and a carrier concentration of 1018 cm−3. The thermoelectric power is measured from room temperature up to 200 °C. X-ray diffraction indicates that the as-prepared films are polycrystalline in nature. The composition and morphology are determined using energy dispersive x-ray analysis and scanning electron microscopy (SEM). The optical bandgap, which is direct-allowed, is 1.58 eV.
TL;DR: In this article, a high permittivity dielectric resonator of suitable resonant frequency was loaded over the patch, and the % bandwidth of the antenna was increased by more than five times without much affecting its gain and radiation performance.
Abstract: A novel technique for the bandwidth enhancement of conventional rectangular microstrip antenna is proposed in this paper. When a high permittivity dielectric resonator of suitable resonant frequency was loaded over the patch, the % bandwidth of the antenna was increased by more than five times without much affecting its gain and radiation performance. A much more improved bandwidth was obtained when the dielectric resonator was placed on the feedline. Experimental study shows a 2:1 VSWR bandwidth of more than 10% and excellent cross polarization performance with increased pass band and radiation coverage almost the same as that of rectangular microstrip antenna. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 35: 327–330, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10597
TL;DR: In this paper, a permanently microbent portion of a plastic optic fiber is coated with a thin film of dye impregnated sol-gel material, and measurements are simultaneously carried out in two independent detection schemes.
TL;DR: In this article, the authors synthesized and characterized 3-formylsalicylic acid (Y zeolite) encapsulated Co(II), Ni(II) and Cu(II).
Abstract: Y zeolite encapsulated Co(II), Ni(II) and Cu(II) complexes of 3-formylsalicylic acid were synthesized and characterized by chemical analyses, SEM, XRD, surface area, pore volume and IR, reflectance and EPR spectroscopy with a view to confirm the encapsulation of complexes and to arrive at the composition, structure and geometry of encapsulated complexes. The analytical data indicate a composition corresponding to the binuclear complex of 3-formylsalicylic acid. The characterization data show the absence of extraneous complexes, retention of zeolite crystalline structure and encapsulation in the cavities. The shift of carbonyl-stretching frequencies of both the aldehyde and carboxylate groups of 3-formylsalicylic acid suggests binuclear coordination in the encapsulated complexes. Tetrahedral, octahedral and tetrahedrally distorted square planar symmetries are tentatively assigned to the encapsulated complexes of Co(II), Ni(II) and Cu(II) ions, respectively. Encapsulated Cu(II) complex is catalytically very efficient as compared to other complexes for the partial oxidation of benzyl alcohol and ethylbenzene and is stable to be recycled without much deterioration.
TL;DR: In this article, aniline and phenol methylation using methanol as the alkylating agent was investigated and an attempt was made to interpret the observed trends based on the variation of surface acid-base properties of the catalyst surface with changes in the spinel composition.
Abstract: Depending on the variation of the Zn2+/Co2+ ratio in the Zn1−xCoxFe2O4 (x=0, 0.2, 0.5, 0.8 and 1.0)-type ferrospinels, the systems showed different activity trends for aniline and phenol methylation using methanol as the alkylating agent. An increase in Zn2+/Co2+ ratio increased the rate of N-monomethylation of aniline, whereas, a decrease in the ratio favored the rate of ortho methylation of phenol. An attempt has been made to interpret the observed trends based on the variation of surface acid–base properties of the catalyst surface with changes in the spinel composition. The efficiency of adsorption of aniline, phenol or methanol depends not only on the catalyst surface acid–base properties but also on the polarity of the adsorbing molecules. A controlled interplay of surface acid–base properties and polarity of the respective reacting molecules determines the efficiency of a particular reaction. In the case of aniline methylation, surface basicity plays a dominating role, whereas for phenol methylation surface acidity plays a dominating role.
TL;DR: In this article, annealing temperatures of indium selenide thin films were varied from 373 to 723 K in high vacuum and X-ray diffraction studies revealed that polycrystalline and amorphous γ-In2Se3 films were obtained depending on the annaling temperature.
TL;DR: In this article, a cost-effective, simple, sensitive and portable LED based fiber optic evanescent wave sensor for simultaneously detecting trace amounts of chromium and nitrite in water is presented.
TL;DR: To determine if inherited thrombophilia and immunological disorders represent risk factors for small for gestational age infants, and to assess their relationship with neonatal status.
TL;DR: The results show that GABA( B) receptor enhancement induce hepatic neoplasia and baclofen is seen to act as a potent co-mitogen, triggering DNA synthesis in primary cultures of rat hepatocytes, mediated through the G(i) protein coupled GABA(B) receptors.
Abstract: In the present study, the involvement of GABA(B) binding parameters were analyzed in partial hepatectomized (PH), lead nitrate (LN) induced hyperplastic and N-nitrosodiethylamine (NDEA) treated neoplastic rat livers at the peak DNA synthesis. The receptor up-regulated significantly in NDEA treated group compared with respective control. The affinity of the receptor decreased in PH while it increased in LN treated rats. In the other groups, the binding parameters remained unaltered. The displacement analysis using GABA(B) receptor agonist, [3H]baclofen, against baclofen showed a shift in affinity of the receptor towards high-affinity in PH rats and towards low-affinity in LN treated rats. Baclofen dose-dependently induced EGF mediated DNA synthesis in primary hepatocyte cultures. Also, it significantly reduced the TGFbeta1 suppression of EGF induced DNA synthesis. The effect of baclofen on hepatocyte DNA synthesis was abolished by the addition of G(i)-protein inhibitor, pertussis toxin, suggesting the involvement of GABA(B) receptor mechanisms in hepatocyte DNA synthesis. Baclofen alone could not elicit any significant change in DNA synthesis. Thus, our results show that GABA(B) receptor enhancement induce hepatic neoplasia. Also, baclofen is seen to act as a potent co-mitogen, triggering DNA synthesis in primary cultures of rat hepatocytes, mediated through the G(i) protein coupled GABA(B) receptors.
TL;DR: The microwave dielectric properties of (1− x )CaTiO 3 − x Sm(Mg 1/2 Ti 1/ 2 )O 3 (0.1≤ x ≤ 1.0) have been investigated in this paper.
TL;DR: In this article, the wavelength dependence of the nonlinear absorption of a bis-phthalocyanine, Nd(Pc)2, dissolved in dimethyl formamide, was studied in the rising part of the Q-band using the open aperture Z-scan technique, to determine the wavelength region over which the non-linear absorption changes from reverse saturable absorption to saturation absorption.
Abstract: The wavelength dependence of the nonlinear absorption of a bis-phthalocyanine, Nd(Pc)2, dissolved in dimethyl formamide was studied in the rising part of the Q-band using the open aperture Z-scan technique, to determine the wavelength region over which the nonlinear absorption changes from reverse saturable absorption to saturable absorption. It was found that the sample could be used as a reverse saturable absorber, and hence as an optical limiter, up to a wavelength of about 604 nm. The imaginary part of the third order susceptibility was also calculated for these wavelengths. Resonant enhancement of the imaginary part of the third order susceptibility was clearly observed.