Showing papers by "Cochin University of Science and Technology published in 1998"
TL;DR: In this paper, a series of heterocyclic base adducts of copper(II) complexes have been synthesised by the reaction of copper (II) acetate with salicylaldehyde N(4)-phenylthiosemicarbazone in presence of pyridine (py), piperidine (pip), β/γ-picoline (β/γ)-pic), 1,10-phenanthroline (phen) and 2,2′-bipyridine(bipy).
219 citations
TL;DR: The results show that serotonin can act as a potent hepatocyte comitogen and induce DNA synthesis in primary cultures of rat hepatocytes, which is suggested to be mediated through the serotonin S2 receptors of hepatocytes.
114 citations
TL;DR: In this paper, it was shown that zinc occupies octahedral sites, contrary to the earlier belief that zinc occupied only the tetrahedral sites in a normal spinel, and the amount of zinc on the B site increases with decrease in particle size.
108 citations
TL;DR: Molecular electrostatic potential maps of some fluoroquinolones having varying degrees of activity against the bacterium Staphylococcus Aureus have been studied using the optimized hybridization displacement charges (HDC) combined with Löwdin charges obtained by the AM1 method.
Abstract: Molecular electrostatic potential (MEP) maps of some fluoroquinolones having varying degrees of activity against the bacterium Staphylococcus Aureus have been studied using the optimized hybridization displacement charges (HDC) combined with Lowdin charges obtained by the AM1 method. The roles of different substitutions at the N1-position in the parent quinolone ring have been studied. The conformation of the carboxylic group attached to the quinolone ring was shown to be such that there is an intramolecular hydrogen bonding between the hydrogen atom of this group and the oxygen atom of the carbonyl group of the quinolone moiety. The carbonyl oxygen atom of the quinolone moiety, hydroxyl oxygen atom of the carboxylic group and the terminal nitrogen atom of the piperazin ring attached to the quinolone ring appear to be involved in the action of the drugs through electrostatic interactions while the N1-alkyl substituents seem to be involved in the same through hydrophobic interactions.
107 citations
TL;DR: In this article, thermal diffusivity measurements are carried out in certain organic liquids using the pulsed dual-beam thermal lens technique using the 532 nm pulses from a frequency doubled Q-switched Nd:YAG laser are used as the heating source and an intensity stabilized He-Ne laser serves as the probe beam.
Abstract: Thermal diffusivity measurements are carried out in certain organic liquids using the pulsed dual beam thermal lens technique. The 532 nm pulses from a frequency doubled Q-switched Nd:YAG laser are used as the heating source and an intensity stabilized He-Ne laser serves as the probe beam. Experimental determination of the character- istic time constant of the transient thermal lens signal is verified theoreti- cally. Measured thermal diffusivity values are in excellent agreement with literature values. © 1998 Society of Photo-Optical Instrumentation Engineers. (S0091-3286(98)00510-8)
82 citations
TL;DR: In this article, the authors used prawn waste as a substrate for chitinase production by the marine fungus Beauveria bassiana BTMF S10, in a solid state fermentation (SSF) culture.
Abstract: Prawn waste, a chitinous solid waste of the shellfish processing industry, was used as a substrate for chitinase production by the marine fungus Beauveria bassiana BTMF S10, in a solid state fermentation (SSF) culture. The␣process parameters influencing SSF were optimized. A maximum chitinase yield of 248.0 units/g initial dry substrate (U/gIDS) was obtained in a medium containing a 5:1 ratio (w/v) of prawn waste/sea water, 1% (w/w) NaCl,␣2.5% (w/w) KH2PO4, 425–600μm substrate particle size at 27°C, initial pH 9.5, and after 5 days of incubation. The presence of yeast extract reduced chitinase yield. The results indicate scope for the utilization of shellfish processing (prawn) waste for the industrial production of chitinase by using solid state fermentation.
75 citations
TL;DR: Analytical results for the number of busy servers and waiting customers at pre-arrival and arbitrary epochs and a recursive relation for the partial binomial moments and explicit expressions for the marginal binomial Moments both in transient and steady states are obtained.
Abstract: This paper considers an infinite server queue in discrete time in which arrivals are in batches of variable size X and service is provided in batches of fixed size R. We obtain analytical results for the number of busy servers and waiting customers at pre-arrival and arbitrary epochs. For the number of busy servers we obtain a recursive relation for the partial binomial moments and explicit expressions for the marginal binomial moments both in transient and steady states. Special cases are also considered
67 citations
TL;DR: Marine yeasts (33 strains) were isolated from the coastal and offshore waters off Cochin and SCP (single cell protein) generation was noted in terms of the increase in protein content of the final product.
58 citations
TL;DR: The electrical conductivity of silicone rubber vulcanizates containing carbon blacks (e.g., acetylene black, lamp black, and ISAF (N-234) black) was investigated in this paper.
Abstract: The electrical conductivity of silicone rubber vulcanizates containing carbon blacks [e.g., acetylene black, lamp black, and ISAF (N-234) black] were investigated. The change in electrical conductivity with varying amounts of carbon blacks and the temperature dependence was measured. The mechanical properties like tensile strength, tear strength, elongation at break, hardness, etc., of the vulcanizates were determined. A comparative study of the electrical conductivity of the composites revealed that the electrical conductivity of the composites made with acetylene black was higher than that of the composites made of other blacks. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1043–1050, 1998
39 citations
TL;DR: Results suggest that pyridoxine and insulin together serve a better control for diabetes.
36 citations
TL;DR: In this paper, a cavity perturbation technique suitable for measuring magnetic parameters of ferrite materials is discussed, where rod-shaped samples or a ferrite-powder-filled capillary tube are placed at the position of maximum magnetic field in a rectangular waveguide cavity.
Abstract: A cavity perturbation technique suitable for measuring magnetic parameters of ferrite materials is discussed. Rod-shaped samples or a ferrite-powder-filled capillary tube are placed at the position of maximum magnetic field in a rectangular waveguide cavity. From the shift in the resonant frequency and the Q-value, the complex permeability of the material can be evaluated. © 1998 John Wiley & Sons, Inc. Microwave Opt Technol Lett 18: 241–243, 1998.
TL;DR: In this article, a new compact microstrip antenna element is analyzed and the analysis can accurately predict the resonant frequency, input impedance, and radiation patterns, which is more suitable in applications where limited antenna real estate is available.
Abstract: A new compact microstrip antenna element is analyzed. The analysis can accurately predict the resonant frequency, input impedance, and radiation patterns. The predicted results are compared with experimental results and excellent agreement is observed. These antenna elements are more suitable in applications where limited antenna real estate is available.
TL;DR: In this paper, a target kept under partial vacuum con- ditions was irradiated with focused nanosecond pulses at 1:06 mm from a Nd:YAG laser.
Abstract: A silver target kept under partial vacuum con- ditions was irradiated with focused nanosecond pulses at 1:06 mm from a Nd:YAG laser. The electron emission mon- itored with a Langmuir probe shows a clear twin-peak distri- bution. The first peak which is very sharp has only a small de- lay and it indicates prompt electron emission with energy as much as 60 5e V. Also the prompt electron emission shows a temporal profile with a width that is same as that for the laser pulse whereas the second peak is broader, covers sev- eral microseconds, and represents the low-energy electrons (2 0: 5e V) associated with the laser-induced silver plasma as revealed by time-of-flight measurements. It has been found that prompt electrons ejected from the target collisionally excite and ionize ambient gas molecules. Clearly resolved rotational structure is observed in the emission spectra of ambient nitrogen molecules. Combined with time-resolved spectroscopy, the prompt electrons can be used as excitation sources for various collisional excitation-relaxation experi- ments. The electron density corresponding to the first peak is estimated to be of the order of 10 17 cm 3 and it is found that the density increases as a function of distance away from the target. Dependence of probe current on laser intensity shows plasma shielding at high laser intensities.
TL;DR: There may be an important regulatory role of the glutamate pathway in brain neural network disturbances and neuronal degeneration in diabetes as a function of age.
Abstract: Kinetic parameters of brain glutamate dehydrogenase (GDH) were compared in the brain stem, cerebellum and cerebral cortex of three weeks and one year old streptozotocin (STZ) induced four day diabetic rats with respective controls. A single intrafemoral dose of STZ (60 mg/Kg body weight) was administered to induce diabetes in both age groups. After four days the blood glucose levels showed a significant increase in the diabetic animals of both age groups compared with the respective controls. The increase in blood glucose was significant in one year old compared to the three weeks old diabetic rats. The Vmax of the enzyme was decreased in all the brain regions studied, of the three weeks old diabetic rats without any significant change in the Km. In the adult the Vmax of GDH was increased in cerebellum and brain stem but was unchanged in the cerebral cortex. The Km was unchanged in cerebellum and cerebral cortex but was increased in the brain stem. These results suggest there may be an important regulatory role of the glutamate pathway in brain neural network disturbances and neuronal degeneration in diabetes as a function of age.
TL;DR: In this article, the illuminated J−V characteristics of the devices prepared with different thicknesses of CdS and CuInSe2 were studied and the typical solar cell parameters obtained for the best cell are: Voc = 365 mV, Jsc = 12 mA/cm2, FF = 61%, and η = 31% under an illumination of 85 mW/cm 2 on a cell of active area 01 cm2.
TL;DR: In this article, a single-feed dual-frequency compact microstrip antenna with a shorting pin is described, which gives a large variation in frequency ratio of the two operating frequencies, without increasing the overall size of the antenna.
Abstract: A single-feed dual frequency compact microstrip antenna with a shorting pin is described. This new antenna configuration gives a large variation in frequency ratio of the two operating frequencies, without increasing the overall size of the antenna.
TL;DR: In this article, the Ba I emission line at 553.5 nm was monitored as a function of time elapsed after the incidence of a laser pulse on the target, and the time evolution of these important plasma parameters has been worked out.
Abstract: Cu3O7 target in vacuum and the plasma thus generated was studied using time-resolved spectroscopic techniques. Line broadening of the Ba I emission line at 553.5 nm was monitored as a function of time elapsed after the incidence of a laser pulse on the target. Measured line profiles of barium species were used to infer the electron density and temperature, and the time evolution of these important plasma parameters has been worked out.
TL;DR: In this article, the mechanical properties of the short polyester-fiber-reinforced polyurethane elastomer composite with and without different bonding agents were studied.
Abstract: Mechanical properties of the short-polyester-fiber-reinforced polyurethane elastomer composite with and without different bonding agents were studied. It was found that the properties depend on the orientation and concentration of fibers. Properties such as tensile strength, modulus, and tear strength increase with the increase of fiber loading, whereas the rate of increase of abrasion loss decreases with fiber loading. The bonding agent, MD resin, was found to increase the mechanical properties of the composite. Initial properties of a composite containing a bonding agent based on glycerol (GL) and 4,4′ diphenyl methane diisocyanate (MDI) were found to be better, whereas the retention of mechanical properties after aging was found to be good for the composite containing a bonding agent based on a 1:1 combination of polypropylene glycol (PPG) and polypropylene glycol-glycerol mixture with MDI.
TL;DR: In this paper, a squeezed state representation for quantized scalar fields in a classical spatially homogeneous anisotropic background cosmology is constructed for each mode of a quantised scalar field and the expectation values of stress energy tensor are calculated in squeezed vacuum states.
Abstract: A squeezed state representation is constructed for each mode of a quantized scalar field in a classical spatially homogeneous anisotropic background cosmology. The expectation values of stress–energy tensor are calculated in squeezed vacuum states. The results for the fluctuations in energy density and anisotropic pressure are also presented.
TL;DR: In this paper, a liquid phase benzylation of o -xylene to 3,4-dimethyl diphenylmethane with benzyl chloride (BC) has been investigated in the presence of various zeolite catalysts.
Abstract: Liquid-phase benzylation of o -xylene to 3,4-dimethyl diphenylmethane (3,4-DMDPM) with benzyl chloride (BC) has been investigated in the presence of various zeolite catalysts. Conventional homogeneous Lewis acid catalyst, AlCl 3 , is also included for comparison. Under identical reaction conditions, zeolite H-beta is considerably more selective than the other zeolite catalysts and AlCl 3 in the benzylation of o -xylene. The conversion of BC, rate of BC conversion and selectivity to 3,4-DMDPM over H-beta after 1 h of reaction time and at 363 K are ca. 33.5 wt.%, 12.6 mmol g −1 h −1 and 92.2 wt.%, respectively. For comparison, the conversion of BC, rate of BC conversion and selectivity to 3,4-DMDPM over AlCl 3 , under identical reaction conditions, are estimated to be 76.6 wt.%, 28.8 mmol g −1 h −1 and 65.5 wt.%, respectively. Higher amounts of consecutive products (32.9 wt.%) are achieved over non-shape-selective AlCl 3 as compared to the zeolite H-beta (6.9 wt.%). The conversion of BC to the products largely depends on the reaction conditions and acidity of the zeolite catalysts. Acidity of the zeolite catalysts is measured by temperature-programmed desorption (TPD) of ammonia. The effect of reaction time, SiO 2 /Al 2 O 3 ratio of H-beta, catalyst concentration, reaction temperature and o -xylene to BC molar ratio on the catalyst performance is examined in order to optimize the conversion of BC and selectivity to 3,4-DMDPM. The conversion of BC using H-beta is increased significantly with the increase in reaction time, catalyst concentration, reaction temperature and o -xylene to BC molar ratios, however, an increase in the SiO 2 /Al 2 O 3 molar ratio of H-beta lowered the BC conversion. The benzylation of m -xylene and p -xylene is also investigated over zeolite H-beta catalyst. H-beta is recycled four times and a decrease in BC conversion is observed after each cycle which is related to the minor dealumination of zeolite catalyst by HCl formed during the reaction. The formation of DMDPM is explained by an electrophilic attack of the benzyl cation (C 6 H 5 CH + 2 ) on the o -xylene ring whose formation is facilitated by acid sites of the zeolite catalysts.
TL;DR: In this article, the effect of chemical modification on viscous and elastic properties of LDPE and two blend systems (LDPE/LLDPE (80:20, 60:40) is reported.
TL;DR: In this article, the effect of the variation of chlorinated natural rubber (CNR) and phenolformaldehyde (PF) resin in the adhesive solutions on lap shear strength was determined.
Abstract: Rubber solutions were prepared and used for bonding wood pieces. The effect of the variation of chlorinated natural rubber (CNR) and phenolformaldehyde (PF) resin in the adhesive solutions on lap shear strength was determined. Natural rubber and neoprene-based adhesive solutions were compared for their lap shear strength. The storage stability of the adhesive prepared was determined. The change in lap shear strength before and after being placed in cold water, hot water, acid, and alkali was tested. The bonding character of these adhesives was compared with different commercially available solution adhesives. The room-temperature aging resistance of wood joints was also determined. In all the studies, the adhesive pre- pared in the laboratory was found to be superior compared to the commercial adhe- sives. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1185-1189, 1998
TL;DR: In this article, the thermal degradation of short polyester fiber reinforced polyurethane composites with and without different bonding agents has been studied by thermogravimetric analysis.
TL;DR: In this article, a new method for enhancing the 2.1 VSWR impedance bandwidth of microstrip antenna s is presented, which is achieved by loading the antenna by a ceramic microwave dielectric resonator (DR).
Abstract: A new method for enhancing the 2.1 VSWR impedance bandwidth of microstrip antenna s is presented. Bandwidth enhancement is achieved by loading the microstrip antenna by a ceramic microwave dielectric resonator (DR). The validity of this technique has been estab- lished using rectangular and circular radiating geometries. This method improves the bandwidth of a rectangular microstrip antenna to more than 10% (= 5 times that of a conventional rectangular microstrip antenna ) with an enhanced gain of I dB. © 1998 John Wiley & Sons, Inc. Microwave Opt Technol Lett 17: 205-207, 1998.
TL;DR: In this article, the formation and growth of TiC precipitates in D-9 alloy is monitored by positron lifetime spectroscopy and it is found that dislocation controlled TiC precipitation is controlled by dislocations.
Journal Article•
TL;DR: In this paper, a time series of the monsoonal-upwelling indices suggests that between - 23 to 18 Ka BP minimum upwelling and weaker monsoon occurred.
Abstract: Planktic foraminifera and pteropods were analysed qualitatively and quantitatively from two gravity cores recovered from the shelf off northern Kerala representing the past - 23 Ka record. Based on the temporal variation in the composition of faunal assemblages, oceanographic and climatic changes during late Quaternary are interpreted. A time-series of the monsoonal-upwelling indices suggests that between - 23 to 18 Ka BP minimum upwelling and weaker monsoon occurred. This period was followed by a gradual increase in the intensity of upwelling and monsoonal strength during - 18 to 15 Ka BP. After a breif interval of weak monsoon, it intensified again from -12 to 10 Ka BP. The southwest monsoon was weaker from - 5 Ka BP with minor fluctuations in its strength. The study also reveals that pteropod shells made up of aragonite (highly solution susceptible) are found in different states of preservation in response to oceanographic changes during the Quaternary. Three kinds of shells subjected to different modes of preservation occur in the cores: (i) transparent shells (excellent preservation), (ii) opaque-white shells and (iii) molds with original shells (corrosion and dissolution). The preservation of aragonite shells was excellent between - 23 to 18 Ka BP. Aragonite dissolution is recorded with its maximum from - 17 to 15 Ka BP. The pteropod shells are well preserved during Holocene.
TL;DR: In this paper, a novel fiber optic sensor for the in situ measurement of the rate of deposition of thin polypyrrole thin films has been developed, based on the evanescent wave in the uncladded portion of a multimode fiber.
TL;DR: In this article, the integrability properties of a perturbed nonlinear Schrodinger equation were studied using Painleve analysis and Laxs method, and the solution of the perturbed equation, with the perturbing term depending only on time, was found by direct integration.
Abstract: The integrability properties of a perturbed nonlinear Schrodinger equation are studied using Painleve analysis and Laxs method. We distinguish between integrability in the Painleve sense and integrability in the Lax sense. The solution of the perturbed equation, with the perturbing term depending only on time, is found by direct integration. It is seen that the perturbing nonlinear inhomogeneity can split the fundamental soliton into pulses at high values of the perturbation strength.
TL;DR: In this paper, the properties of low-density polyethylene and its blend with linear low density polyethylenes (LDPE) with varying concentrations of dicumyl peroxide (DCP) were compared.
Abstract: The properties of low-density polyethylene (LDPE) and its blend with linear low-density polyethylene LDPE : LLDPE (75 : 25) modified with varying concentrations of dicumyl peroxide (DCP) were compared. Chemical modification was carried out in a Brabender plasticorder under set conditions of temperature, rotor speed, and time. The results are reported in terms of the type of polyethylene used, concentration of DCP, mixing torque, temperature and time on the processing, and mechanical and physical properties of the modified samples. Interpretation of the results is given in terms of gel contents which relate to the three-dimensional network structure of polyethylene. The modified blend forms a denser network structure and, hence, better product properties relative to that of modified LDPE, indicating the influence of LLDPE in increasing the rate and extent of crosslinking on blending with LDPE.
TL;DR: In this paper, dual beam transient thermal lens studies were carried out in rhodamine 6G methanol solutions using 532 nm pulses from a frequency doubled Nd:YAG laser.
Abstract: Dual beam transient thermal lens studies were carried out in rhodamine 6G methanol solutions using 532 nm pulses from a frequency doubled Nd:YAG laser. Analysis of thermal lens signal shows the existence of different nonlinear processes like two photon absorption and three photon absorption phenomena along with one photon absorption. Concentration of the dye in the solution has been found to influence the occurrence of the different processes in a significant way.