Showing papers by "Jadavpur University published in 1988"

Miscible blends from rigid poly(vinyl chloride) and epoxidized natural rubber

Abstract: Mechanical properties and fracture of melt-blended poly(vinyl chloride) (PVC) and epoxidized natural rubber (ENR) having 50 mol % epoxidation level are studied at different compositions. The effect of blend ratio on tensile strength, tear strength, elongation at break, tension set after failure, and hardness are determined. The stress-strain behaviour of low ENR blends exhibits yielding and necking, whereas that of high ENR blends exhibits soft elastomeric deformation. At higher compositions of ENR, plots of tensile strength, tear strength, and hardness against blend composition are concave in nature; and plots of the elongation at break deviate markedly from the additive value with a pronounced maximum occurring at the 70wt% composition of ENR. The scanning electron microscopic examination of fracture surfaces of blends does not show any features of phase separation of ENR or PVC. The tensile fracture surface of rigid PVC exhibits partially fused particle structures of PVC and that of blends exhibits features of shearing and horizontal discontinuous striations. The torn surface of rigid PVC shows evidence of intrinsic crazing and that of blends shows features of shear fibrils, vertically changed discontinuous striations, steps, and unstable and stable tear fronts.

Linearizing transducer characteristics

Abstract: Most of the practical transducers fall into two categories regarding their input-output characteristics: type I, with a characteristic that is exponentially rising, and type II, with a characteristic that is exponentially decaying. While type I is easily linearized using a logarithmic converter, type II needs additional inversion means for the purpose of linearization. A technique for linearizing type-II transducer characteristic using a log-converter and a FET is presented, and its performance is compared with that of a simple single-stroke digital technique. Examples and experimental results are presented and discussed. >

Counterion binding behaviour of micelles of sodium dodecyl sulphate and bile salts in the pure state, in mutually mixed states and mixed with a nonionic surfactant

Abstract: The counterion binding behaviour of micelles of sodium dodecyl sulphate (SDS) and several bile salts in the pure state have been studied, as well as in mutually mixed states, and in a mixed state with polyoxyethylene sorbitan monolaurate (PSML) as a nonionic surfactant. Electrochemical measurements have shown no counterion binding by the pure bile salt micelles and their mixtures with PSML; they can bind counterions when mixed with SDS, whereas the surfactant anions of SDS micelles bind counterions in the pure state and/or in mixed states with PSML. In the SDS-PSML and SDS-bile salts combinations, the counterion association is decreased by the increased proportions of the second component. The extent of counterion binding by the different systems is presented.

Irrotational Bianchi V viscous fluid cosmology with heat flux

Abstract: The irrotational Bianchi V cosmological model under the influence of both shear and bulk viscosity, together with heat flux, has been studied. Exact solutions for the model are obtained with three assumptions of which the first two relate the matter density, shear scalar, and expansion scalar and the third is a barotropic equation of state, connecting the matter density and thermodynamic pressure. The properties of the solutions are studied and the temperature distribution is also given explicitly. It has been observed that along with the viscosity, heat flux further adds to the rate of entropy increase.

Antimicrobial properties of methdilazine and its synergism with antibiotics and some chemotherapeutic agents.

Abstract: The antihistamine methdilazine (Md) was found to possess a significantly high antibacterial action when tested against 367 strains of bacteria belonging to both Gram-positive and Gram-negative genera. Different groups of bacteria could be arranged in order of their decreasing sensitivity towards Md as follows: S. aureus, V. cholerae, E. coli and Shigella. The range of minimum inhibitory concentration (micrograms/ml) varied between 25 and 200 in most cases, although few strains were sensitive even at 10 micrograms/ml level of Md. 10 different bacteria sensitive to Md and a number of antibiotics when tested for their interaction with Md on one hand and any of the antibiotics of chemotherapeutic agents on the other, it was found that Md in combination with aminoglycosides and several chemotherapeutics showed enhancement of antibacterial effects resulting in synergism. The chemotherapeutic agents bromodiphenhydramine (Bn), diphenhydramine and methyldopa showed distinct synergism when tested in combination with Md. Determination of the area of inhibition zones for the degree of synergism with Md and streptomycin (Sm) produced statistically significant result (p less than 0.01) in comparison with their individual effect. This could also be corroborated by the fractional inhibitory concentration (FIC) index which was 0.49 for Sm-Md and 0.5 for Bn-Md combinations. The synergism of Sm-Md combination was confirmed by in vivo studies.

Exact solutions to Einstein field equations

Abstract: In a recent paper Reboucas and d'Olival obtain an ordinary differential equation for a Bianchi type II metric with a rotating timelike congruence of geodesics, and obtain a particular solution of the differential equation. This paper completely integrates the differential equation.

Studies on process variables for natural fiber composites: effect of polyesteramide polyol as interfacial agent

Abstract: A systematic study of the process variables for polyester composites based on different natural fibers like jute, sisal, ramie, and pineapple has been made with a view to determine the most suitable processing conditions for such composites. Effect of polyesteramide polyol (PEAP) as interfacial agent in such composites has also been discussed. Fracture modes of jute/polyester (JP) composite sample having different fiber volume fractions have been examined by scanning electron microscope (SEM). Fracture surfaces of untreated and PEAP-treated JP composite samples have been examined in SEM, both before and after 72 h immersion in boiling water, to study the nature of interfacial bonding on fiber treatment with PEAP. A qualitative improvement in bonding in case of PEAP-treated JP composites is evident from SEM photomicrographs. This is also supported by physicomechanical properties of the composite samples.

Effects of heat treatment on the optical and structural properties of InSe thin films

Abstract: Thin films of indium selenide of different thicknesses are deposited on glass substrate by vacuum evaporation. The optical gaps (E) are determined from the absorption spectra of as-deposited InSe films. The value of E of a-InSe films is found to increase with the thickness of the films. The InSe films are heat treated at different elevated temperatures from 423 to 573 K. The values of optical gaps E of InSe films are also found to increase with temperature of heat treatment. The effect of thickness and temperature of heat treatment on the optical gap (E) of the film is interpreted in terms of the density of state model of Mott and Davis. The valence band density of states of a-InSe films is calculated from the optical absorption data. The variation of valence band density of states with temperature of heat treatment is observed in the case of a-InSe films. X-ray diffraction spectra are taken for both, as-deposited and heat treated InSe films. A radial distribution function (RDF) analysis of X-ray diffraction (XRD) spectra is made to get an insight into the structural information of the specimens. From the results related to RDFs of the specimens it is shown that in case of InSe a transition from the amorphous to the crystalline state takes place at 573 K. Mittels Vakuumaufdampfung werden dunne Schichten von Indiumselenid verschiedener Dicke auf Glassubstraten aufgebracht. Die optischen Bandlucken (E) werden aus dem Absorptionsspektrum der InSe-Schichten unmittelbar nach der Abscheidung bestimmt. Der Wert E der a-InSe-Schicht nimmt mit der Dicke der Schichten zu. Die InSe-Schichten werden bei verschiedenen erhohten Temperaturen zwischen 423 und 573 K getempert. Die Werte der optischen Bandlucken E der InSe-Schichten nehmen mit der Temperatur der Warmebehandlung ebenfalls zu. Der Einflus der Dicke und der Temperatur der Warmebehandlung auf die optische Bandlucke (E) der Schicht wird mit dem Modell der Zustandsdichte von Mott und Davis erklart. Die Zustandsdichte des Valenzbandes der a-InSe-Schichten wird aus den optischen Absorptionswerten berechnet. Eine Anderung der Valenzbandzustandsdichte mit der Temperatur der Warmebehandlung wird im Falle der a-InSe-Schichten beobachtet. Rontgenbeugungsspektren werden sowohl fur InSe-Schichten unmittelbar nach dem Abscheiden als auch fur getemperte Proben aufgenommen. Eine Analyse der radialen Verteilungsfunktin (RDF) der Rontgenbeugungsspektren (XRD) wird durchgefuhrt, um strukturelle Informationen uber die Proben zu erhalten. Aus den mit RDF verbundenen Ergebnissen wird gefunden, das im Falle des InSe ein Ubergang vom amorphen zum kristallinen Zustand bei 573 K eintritt.

Spectral and photophysical studies of thiazine dyes in triton X-100

Abstract: The absorption spectra of several thiazine dyes such as thionine, azure A, azure B, azure C and methylene blue in aqueous solution of Triton X-100 show that dyes as electron acceptors form 1∶1 charge-transfer (CT) or electron-donor-acceptor (EDA) complexes with Triton X-100, which acts as an electron donor. From the thermodynamic and spectrophotometric properties of these complexes, the abilities of dyes to accept an electron are in the order: azure C > thionine > azure A > azure B > methylene blue. The photogalvanic effect in the aqueous solution dye-surfactant has been studied. Generation of photovoltage supports a CT or EDA interaction between thiazine dyes and Triton X-100. There is a good correlation among the photophysical (photovoltage), spectral and thermodynamic properties of these complexes.

Optical and structural properties of amorphous and heat treated In0.4Se0.6 film of different thicknesses

Abstract: The optical gap (E g opt ) of as-deposited In0.4Se0.6 film is found to increase with the thickness of the film. The optical gap attains a steady value after several heat treatments of the films at elevated temperatures. The values of optical gaps of In0.4Se0.6 films are found to depend on the temperature of the heat treatment. The effect of thickness and temperature of heat treatment on the optical gap of the film is interpreted in terms of creation or elimination of defects in the amorphous structure of In0.4Se0.6 film. X-ray diffraction spectra are taken for both as deposited and heat treated In0.4Se0.6 films. From the results related to the radial distribution functions of the specimens it is noted that in the case of In0.4Se0.6 a transition from amorphous to crystalline states takes place at 523 K and above. The results also show that both the optical gap and the coordination number decrease with increasing temperature of heat treatment. Therefore it is evident that the heat treatment improves the long range order of In0.4Se0.6 but reduces the coordination in the short range.

On unsteady hydromagnetic flows of a dusty fluid between two oscillating plates

Abstract: An initial value investigation is made of the motion of an incompressible viscous conducting fluid with embedded small spherical particles bounded by two infinite rigid non-conducting plates. The flow is generated in the fluid-particle system due to rectilinear oscillations of given frequencies superimposed on the plates in presence of an external transverse magnetic field. The operational method is used to derive exact solutions for the fluid and the particle velocities and the wall shear stress. It is shown that the effect of the dust particles on the fluid velocity depends on the time periods of the oscillating plates. When the time-periods are small, i.e., when the plates oscillate with high frequency, the fluid motion is found to be retarded by the particles. However, when the plates oscillate with larger time periods (smaller frequencies), the fluid velocity is increased by the presence of the particles at the early stage of the motion, and this effect persists until the equilibrium is reached when the particles exert their influence to resist the flow.

Simulation of Physiological pH - Time Profile in In Vitro Dissolution Study: Relationship Between Dissolution Rate and Bioavailability of Controlled Release Dosage Form

Abstract: An in vitro batch dissolution method, simulating the in vivo pH-time profile was developed, using the USP XX dissolution apparatus. Significant correlation between in vitro dissolution data and bioavailability of the drug from the controlled release dosage form was obtained.

Kinetics and mechanism of the oxidation of thiosulphate by hexachloroplatinate(IV)

Abstract: Rate constants for the oxidation of thiosulphate by hexachloroplatinate(IV) have been measured. The kinetics of the oxidation of thiosulphate follow a second-order rate law, first order with respect to thiosulphate and first order with respect to platinum(IV). The influence of pH is small. The rates are found to depend on the nature and concentration of the cations and follow the order: Cs+>Rb+>K+>Na+>Li+. The activation parameters calculated from the temperature studies are: ΔH‡=42.9 k J mol−1 and ΔS‡=−102 JK−1 mol−1. A mechanism of the reaction in terms of intermediate formation of free radicals followed by the formation of tetrathionate is postulated to explain the kinetic behaviour.

Calcutta Pollutants: Part II. Polynuclear Aromatic Hydrocarbon and Some Metal Concentration on Air Particulates During Winter 1984

Abstract: The concentration of 25 polynuclear aromatic hydrocarbons (PAH) and 12 metals on air-particulate matter of Calcutta city were determined during January–February 1984. X-ray fluorescence (XRF) was applied for determination of metal concentration and gas chromatography–mass spectrometry (GC–MS) for PAH determination. Both PAH and metal concentrations found are present at higher concentration when compared with cities in Europe and USA.

Higher-order corrections to the ion-acoustic waves in a relativistic plasma (isothermal case)

Abstract: As a continuation of our earlier work, we have analysed the higher-order perturbative corrections to the formation of (ion-acoustic) solitary waves in a relativistic plasma. It is found that the relativistic considerations affect the amplitude and width variation - as conjectured in our previous paper. Our analysis employs a higher-order singular perturbation technique, with the elimination of secular terms in stages. In this way we arrive at an inhomogeneous KdV-type equation, which is then solved exactly. At this point a new phenomena arises at a critical value of the phase velocity at which the coefficient of the nonlinear term in the KdV equation vanishes. A new set of stretched co-ordinate is then used to derive a modified KdV equation. In both cases we have numerically computed the specific physical profile of the new solitary wave and its width.

History of Successive Deformations in Relation to Metamorphism-Migmatitic Events in the Schirmacher Hills, Queen Maud Land, East Antarctica

Abstract: The basement complex in the Schirmacher Hills of East Antarctica records the impress of multiple episodes of metamorphism, migmatization and deformation. In the earliest event there was a regional metamorphism under granulite facies conditions and synkinematic migmatization leading to the development of charnockitic rocks. An amphibolite facies metamorphism was superimposed on them. This late event was closely associated with widespread granitization leading to the development of the majority of the quartzofeldspathic gneisses. In the earliest deformation, a migmatitic banding and a crude foliation formed in the charnockitic rocks. This was followed by a period of strong deformation during which two broadly coaxial sets of isoclinal folds (F 2A and F 2B ) formed. The folding movement was also associated with widespread ductile shearing. The periods of amphibolite facies metamorphism, extensive granitization, F 2 folding and the major phase of ductile shearing were overlapping. Localized pegmatite bodies were also emplaced during the later and much weaker folding movements of F 3 and F 4 and along some discordant ductile shear zones cutting across the axial surfaces of F 2 folds.

The Chitradurga Greenstone succession in South India and evolution of the late Archaean basin

Abstract: The Chitradurga greenstone succession of south India comprises a thick pile (~ 10 km) of late Archaean volcanic flows and terrigenous clastic sediments, metamorphosed from greenschist to low-grade amphilobite facies. An older near-shore sedimentary sequence of cratonic affiliation and an off-shore bimodal volcanic sequence were deposited contemporaneously on a gneissic basement. The volcanics are metasomatically altered, and major, minor and trace element data fail to discriminate the metavolcanics in terms of modern plate settings. A younger turbidite sequence of coarser elastics covered the older deposits without any apparent tectonic or erosional break. All the rocks of the succession display evidence of similar deformation, prior to invasion by younger granites (~ 2.5 Ga)in a late syn-kinematic phase.This suggests that initially a simple flat-lying downwarp in a continental crust served as the passive receptacle of the platform-type sediments, and also witnessed volcanism along extensional faulting. This phase of the basin was not associated with any compressive deformation. Subsidence of the Chitradurga basin by the denser volcanics and uplift in the gneissic borderlands provided the infrastructure for subsequent development of the younger turbidite sequence covering the still virtually undeformed older deposits. A compressive orogeny, accompanied by granitic intrusion (~ 2.5Ga) in a late kinematic phase, ultimately deformed and uplifted the basin-fill during the declining phase of basinal activity.There is no evidence in the belt to suggest that the plate-tectonic (Wilson cycle) processes, pending a terminal orogeny, were operative during evaluation of the Chitradurga basin.