Showing papers by "Jadavpur University published in 1984"

Wettability and Contact Angles

Abstract: In everyday life one encounters many different systems where it is apparent that various processes take place at the line of contact between a liquid phase and a solid phase. The molecules in the liquid phase can move larger distances than those in the solid phase. Therefore, since the molecules in a solid phase are well fixed, this gives rise to the fact that it is in general not possible to study the surface forces of the solid phase in the same way we have described for the liquid phase elsewhere in this book. In spite of this, there exist many examples where we have to attribute a definite value of surface tension to the solid surface, in order to be able to describe the different reactions taking place at the solid surface in contact with liquid phase.

Discrimination of isomeric structures using information theoretic topological indices

Abstract: Three newly defined information theoretic topological indices, namely “degree complexity (Id),” “graph vertex complexity (HV),” and “graph distance complexity (HD)” along with three other information indices have been used to study their discriminating power of 45 trees and 19 monocyclic graphs. It is found that the newly defined indices have satisfactory discriminating power while HD has been found to be the only index to discriminate all the graphs studied.

Spatially homogeneous cosmological models.

Abstract: We study nonviscous and viscous fluids in Bianchi types II, VIII, and IX space-times under the restriction that the ratio of shear to expansion be constant.

Pretreatment of indian cane molasses for increased production of citric acid.

Abstract: Surface culture citric acid fermentation was carried out by Aspergillus niger T55, a strain isolated from its natural source, using cane molasses, either untreated or treated by various methods. Citric acid biosynthesis is seriously impaired by both organic and inorganic inhibitors. A combined treatment of molasses with tricalcium phosphate, hydrochloric acid, and Sephadex fractionation minimizes the level of inorganic and organic inhibitors in molasses and increases the production of citric acid (65% weight yield based on total reducing sugar). The optimum level of individual metal ions for citric acid production depends on the concentration of other metals in the medium.

Synthesis of a Class of Deadlock-Free Petri Nets

Abstract: Description d'une nouvelle classe de Reseau de Petri appeles reseaux reguliers Discussion de quelques proprietes graphiques des variants et invariants Le concept d'etiquetage de reseau est introduit et une methode systematique de synthetisation de reseaux reguliers est presentee

Geological features and origin of the chromite deposits of sukinda valley, Orissa, India

Abstract: The chromiferous ultramafic rocks of Sukinda Valley (21°0'–21°5'N:85°43'–86°0'E) of Orissa are intrusive into the Iron-Ore Supergroup (2,950–3,200 Ma) at the eastern periphery of the Indian Precambrian shield. Both laterally and vertically, chromite occurs as persistent layers, lenses or pockets in the serpentinized and silicified dunite-peridotite extending over a strike length of 25 km. The ultramafic rocks and the chromitite layers are cofolded with the Iron-Ore Supergroup into a plunging syncline. Primary layering, ball and pillow structures, cross laminations, graded bedding etc. can also be detected. The different varieties of chromite ore present in the area are massive, banded and spotted, laminated and friable. The grain size of chromite varies between 0.25 and 4 mm, and the fineness of the grain increases from the bottom to the top layers. The cell dimension of chromite (8.23–8.32 A) decreases with the increase of Al2O3.

Single current conveyor tunable sinewave RC oscillator

Abstract: A novel sinewave RC oscillator configuration using a single second generation current conveyor (CC II) is presented. The circuit has all its capacitors grounded and the frequency of oscillation ω0 is tunable by a grounded resistor. The active ω0-sensitivity has been shown to be extremely small.

Integrators and differentiators with current conveyors

Abstract: Ideal integrators and differentiators with second generation current conveyors (CC's) as active devices have been proposed. Single-CC realization schemes are derived from a generalized approach and are shown to have marginal improvement over the conventional types, whereas, the two-CC realizations are canonical with respect to the passive components, amenable for producing independently controllable large time constants and practically insensitive to active prarmeter variation.

Geochemistry of braunite and associated phases in metamorphosed non-calcareous manganese ores of India

Abstract: In the metamorphosed manganese oxide ores of India, braunite is ubiquitous in all assemblages from chlorite to sillimanite grades. Chemical analyses of braunite from different prograde assemblages confirm the presence of a fixed R2+ (=Mn2++Mg+Ca) SiO3 molecule in the mineral. Element partitioning between coexisting braunite and bixbyite indicates a near-ideal mixing of Fe+3/ -Mn+3 in the phases. This also indicates that braunite became relatively ferrian while equilibrating with associated phases such as bixbyite, hollandite and jacobsite during prograde reactions. Petrogenetic studies show that as a general trend, prograde lower oxide phases appeared by deoxidation of higher oxide phases. But braunite, a more reduced phase than bixbyite, appeared early from deoxidation of pyrolusite in presence of quartz. Bixbyite could appear later from the reacting pyrolusite-braunite-quartz assemblage. Inferred mineral reaction paths and the general trend of pro-grade deoxidation reactions suggest that the composition of ambient fluid phase was internally buffered during metamorphism.

Adsorption at Solid-Liquid Interfaces

Abstract: In Chapters 3, 4, and 5, we have discussed extensively the detailed thermodynamic aspects of the adsorption of solute and solvent at the interface formed by the contact of either liquid-gas or liquid-liquid phases The surfaces in all these cases are regarded as homogeneous across the plane of contact, although perpendicular to the surface plane the surface phase is considered as inhomogeneous Surface free energy (or interfacial tension) in such systems involving liquid interface can be accurately measured in the presence of solute component in the bulk solution so that excess adsorption at the interface can be calculated using the Gibbs adsorption equation

An empirical result for the height gain in forest medium

Abstract: Radio path loss measurements were conducted in various tropical rain forests of India at frequencies from 50 to 800 MHz, antenna heights from 1.5 m to 16.5 m above ground with both horizontally and vertically polarized emissions, and at a large variety of path ranges. The results from a series of antenna height-gain measurements in the forest vegetation are presented. Based on the data thus collected, an empirical model is suggested to assess quantitatively the antenna height gain as a function of frequency and antenna heights.

Characteristics of yeast β-galactosidase immobilized on calcium alginate gels

Abstract: Saccharomyces anamensis having β-galactosidase activity, has been immobilized in calcium alginate gel matrix that retained 78.6% enzyme activity to that of native cells. Optimum pH(7.0) was negligibly affected by immobilization. Km values for immobilized and native cells were 119 mM and 102 mM respectively. Protective agents like dithioerythritol, bovine serum albumin, enhance the enzyme activity when added prior to immobilization. Immobilized cells can be stored in refrigeration(4°C) for 42 days without a significant loss of enzyme activity.

Petrochemistry of metamorphosed pillows, and the geochemical status of the amphibolites (Proterozoic) from the Sirohi district, Rajasthan, India

Abstract: Relic pillows in the middle Proterozoic amphibolites, occurring in the Sirohi Road–Abu Road tract of Rajasthan, India exhibit contrasted mineral assemblages from core to rim – mimetic after the crystalline core, the zone of incipient crystallization, and the rim of the original pillows. The major element distribution pattern across the pillows indicates exchange of Na–Al for Ca (Mg, Fe) in an inner reaction zone, surrounding the core and in the inner margin of the rim, and Fe–Al exchange for Ca–Si at the outer margin of the rim.Despite such exchanges around the rims, these pillows have retained their initial geochemical characteristics internally and thus have largely acted as closed systems during post-emplacement metamorphism. Mineral parageneses indicate that the contrasted mineral assemblages could evolve from domainal characters of the co-existing fluids, the compositions of which were only buffered by the reacting minerals during regional metamorphism.The major, minor and trace element contents of the pillows and of amphibolites of diverse petrographic character in the region further establish that the pillow interiors and the massive amphibolites were least modified during metamorphism(s), and represent oceanic tholeiites. Their average 2300 ppm K, 4.5 ppm Rb, 150 ppm Sr, along with the K/Rb and K/Sr ratios of 510 and 15 respectively resemble that of the low K-tholeiites, occurring nearest to the trenches in modern island arcs. On the other hand, the higher values of 17300 ppm K, 4.9 ppm Rb, and 210 ppm Sr of the banded and the schistose amphibolites indicate that they were contaminated in various magnitudes by oceanic sediments.

Triazene-N-oxides as new type of fluorimetric reagents. part i. trace determination of zirconium at the nanogram level

Abstract: Triazene-N-oxides are being reported for the first time as a new type of metallofluorescers. Among eleven triazene-N-oxides studied, 3-(2-hydroxyphenyl)-l-phenyl triazene-N-oxide(R11) gives fluorescence with Zr, Hf, Nb(V) and Ta(V). A method has been developed for trace determination of Zr with R11, excitation and emission maxima of the system being 435 nm and 570 nm respectively.

Adsorption at Liquid Interfaces and the Gibbs Equation

Abstract: In Section 1.12, it was pointed out that the molecules at the boundary region of a solid in contact with a liquid possess higher energy than those present in the interior bulk regions of the condensed phases. It is a common experience that a powdered solid material is able to adsorb many gases with which the former is kept in contact at high pressure. At the interface of the solid powder, the gas molecules accumulate in excess whereby the interfacial energy is decreased. The extent of such accumulation (or adsorption) is experimentally measurable and it is found to depend on temperature, pressure, and other experimental conditions.1 The amount of such adsorption of a gas by a solid material may be positive or zero but never negative.

Three-body interaction and fluorite structure: elastic properties of CaF2, SrF2, and BaF2

Abstract: In spite of the fact that second-order elastic constants of some ionic crystals with fluorite structure can be fitted quite well by the shell model using the two-body interaction only, the situation is still unsatisfactory. In our previous work, it was therefore attempted to provide a satisfactory picture by introducing the three-body interaction. The importance of this interaction was estimated from a study of second-order elastic constants by using mainly the results of a first-principles calculation. In this paper, this investigation is extended to third-order elastic constants. In order to obtain explicit expressions for elastic constants, the terms arising from the Coulomb interaction and shell structure are determined from the work of Srinivasan and those arising from non-Coulomb two- and three-body interactions by the homogeneous deformation theory developed in the preceding paper. The results confirm the importance of the three-body interaction in the study of the elastic properties of Ca${\mathrm{F}}_{2}$, Sr${\mathrm{F}}_{2}$, and Ba${\mathrm{F}}_{2}$.

Thermodynamics of binding water and solute to myosin

Abstract: From the isopiestic measurements of the extents of adsorption of water vapour by fish myosin at various values of water activities at three different temperatures, the changes in free energy, enthalpy and entropy of dehydration of the protein have been calculated. Extents of excess binding of solvent and solute to myosin have also been determined from isopiestic experiments in the presence of different inorganic salts, sucrose and urea respectively. Mols of water and solute respectively bound in absolute amounts to myosin have been evaluated from these data in limited range of solute concentrations. Free energy changes at different concentrations of these solutes have also been evaluated and their relations with ‘salting-in’ and ‘salting-out’ phenomena have been discussed. The order of the values of the standard free energy change for excess binding calculated with respect to an unified thermodynamic scale are found to be consistent with relative reactivity of binding water to myosin in the presence of inorganic salts, sucrose and urea.

Optimum conditions for fusion splicing of optical fiber

Abstract: A low-loss splicing method based on discharge fusion having average splice losses of 0.07 and 0.15 dB for single mode with core diameters of 10 and 7 µm, respectively, and 0.02 dB for 50-µm graded-index optical fibers are obtained. Mathematical expressions for the variation of fusion times and splice losses with effect of applied pressure between the fibers for different axis alignments showing optimum conditions are made. Theoretical curves agree with experimental results.