Showing papers by "Jadavpur University published in 1968"

A Deformable Shell Model for the Alkali Halides

Abstract: The simple shell model which takes account of the polarizability of the ions is improved by including the effect of deformations of the electron shell during the vibrations of the ions. The deformability is introduced in a phenomenological way and it is shown that this ultimately leads to three body interactions between like particles. Because of the inclusion of many body effects the elastic constants do not satisfy in general the Cauchy relation C12 = C44. The theory is applied to the calculation of the dispersion curves for NaI and the result is compared with the simple shell model curves and with the curves obtained by neutron diffraction experiments. Definite improvement of the agreement for the deformable shell model is noticed. Das einfache Schalenmodell, das die Polarisierbarkeit der Ionen berucksichtigt, wird durch Einbeziehung der Verformungen der Elektronenschalen wahrend der Schwingungen der Ionen verbessert. Die Deformierbarkeit wird phanomenologisch eingefuhrt und es wird gezeigt, das dies zu einer Dreikorperwechselwirkung zwischen gleichen Teilchen fuhrt. Wegen der Einbeziehung der Vielkorpereffekte erfullen die elastischen Konstanten im allgemeinen nicht die Cauchy-Relation C12 = C44. Die Theorie wird angewendet zur Berechnung der Dispersionskurven fur NaJ und das Ergebnis wird mit Kurven nach dem einfachen Schalenmodell und mit Kurven, die durch Neutronenbeugungsexperimente erhalten werden, verglichen. Das Modell mit deformierbaren Schalen zeigt deutlich bessere Ubereinstimmung.

Stationary distributions of dust and electromagnetic fields in general relativity

Abstract: In the present paper we give a number of solutions corresponding to a stationary distribution of rotating charged dust with vanishing Lorentz force. It is found that in all but one case there are closed time-like lines. Further, the paper shows the existence of some homogeneous stationary universes other than that of Godel and Einstein when, besides the matter field, there is an electromagnetic field as well.

Helical log-periodic array

Abstract: A helical log-periodic array is designed considering the same parameters as those used in an existing log-periodic dipole array. The impedance and radiation characteristics are measured for both arrays. It is observed that the arrays have similar characteristics. Moreover, the advantage of the helical array is that its transverse dimension becomes much smaller.

Mineralogy and genesis of the metamorphosed manganese silicate rocks (gondite) of Gowari Wadhona, Madhya Pradesh, India

Abstract: Manganese silicate rocks, interbanded with manganese oxide orebodies, constitute an important stratigraphic horizon in the Mansar formation of the Sausar Group of Precambrian age in India. The manganese silicate rocks of Gowari Wadhona occupy the westernmost flank of the manganese belt of the Sausar Group. These rocks are constituted of spessartite, calcium-rich rhodonite, quartz, manganoan diopside, blanfordite (manganese bearing member of diopside-acmite series), brown manganese pyroxene (manganese bearing aegirine-augite), winchite (manganese bearing richterite-tremolite), juddite (manganese bearing amphibole with richterite, tremolite, magnesioriebeckite and glaucophane molecules), tirodite (manganese bearing amphibole with richterite, cummingtonite and glaucophane molecules), manganophyllite, alurgite, piedmontite, braunite, hollandite (and other lower oxides of manganese) with minor apatite, plagioclase, calcite, dolomite and microcline. A complete mineralogical account of the manganese-bearing phases has been given in the text. It has been shown that the juxtaposition of manganese silicate rocks with dolomitic marble, regional metamorphism to almandine-amphibolite facies and assimilation of pegmatite veins cutting across the manganese formation, were responsible for the development of these manganese silicate rocks and the unusual chemical composition of some of the constituent minerals. It has been concluded that the manganese silicate rocks of Gowari Wadhona were originally laid down as sediments comprising manganese oxides admixed with clay, silica etc. and were later regionally metamorphosed to almandine-amphibolite facies. All evidences indicate that rhodochrosite was not present in the original sediment and the bulk composition of the sediments was rich in manganese. These rocks agree entirely to the detailed nomenclature of the gondites enunciated by Fermor (1909) and amplified by Roy and Mitra (1964) and Roy (1966).

A method for the correction of quantum yields of fluorescence in solutions

Abstract: — The correction factors due to the overlap of absorption and emission spectra have been calculated for various concentrations of fluorescein dye at pH 12 by using the experimentally obtained value of apparent molar absorptivity, e2, for the fluorescence radiation. The observed fluorescence intensities for the same-surface detection for a given geometry have been corrected for the secondary emission effect thus calculated, and also for refraction and dilution effects, to give corrected relative quantum yields for the solutions. These have been converted to the absolute values by comparison of the integrated fluorescence quantum spectrum of a dilute solution of fluorescein with that for quinine sulphate in 0.1 N H2SO4. The corrected quantum yields compare well with values given in the literature.

Liquid-liquid extraction of arsenic(III), antimony(III) and bismuth(III) with potassium ethyl xanthate

Abstract: Methods are described for quantitative extraction of arsenic(III), antimony(III) and bismuth(III) with potassium ethyl xanthate-carbon tetrachloride. The optimum acidity conditions are 0.1–0.2 M hydrochloric acid for arsenic, 1.8–2.5 M hydrochloric acid for antimony and pH 1.5–4.0 for bismuth. From the organic extracts arsenic and antimony are estimated by conventional iodometric methods while bismuth is determined spectrophotometrically at 400 nm. The effect of acidity, reagent concentration, period of extraction and diverse ions are discussed. The infra-red spectra are also described.

On the determination of torque and thrust during drilling of ductile materials

Abstract: SUMMARY In the present paper, the authors describe a theoretical model for calculating torque and thrust during drilling of ductile materials. Due cognizance has been taken on the effect of chisel edge extrusion. By applying the theory of wedge indentation, the indenting component of the thrust force at the chisel edge zone has been calculated. The torque has been estimated by considering the actual variation of the chip thickness along the cutting edge of the drill and applying suitable angle relationship. The results have been extended to double-point drills. Comparison of theoretical values with experimental results indicate good agreement.

An active dual-input RC notch filter

Abstract: The theory and experimental performance of an active RC dual-input notch filter are presented. The frequency of maximum attenuation of the network can be shifted by varying the ratio of the amplitudes of the two input signals without changing the element values of the synthesized network. Comparatively high selectivity around quite low notch frequencies is shown to be realizable.

Hydroxy Sulfonated Fatty Acid Esters as Surface Active Agents II: Surfactants from Individual Saturated and Unsaturated Fatty Acids

Abstract: Hydroxy sulfonated fatty acid ester surfactants, having the general formula RCOOCH2CHOHCH2SO3M (where M is alkali or other metal) have been synthesized from four saturated (C12 to C18) and four unsaturated (C18−, C182−, C183− and ricinoleic) fatty acids. Comparative evaluation of their surface active properties as well as some analytical methods for determining their composition and their identification and separation have been described. An der Hydroxylgruppe sulfonierte Fettsaureester mit oberflachenaktiven Eigenschaften II: Oberflachenaktive Stoffe aus gesattigten Fettsauren Die an der Hydroxylgruppe sulfonierten Fettsaureester der allgemeinen Formel RCOOCH2CHOHCH2SO3M (M = Alkalimetall oder ein anderes Metall) wurden aus vier gesattigten (C12 bis C18) und vier ungesattigten Fettsauren (C18−, C182−, C183− und Ricinolsaure) dargestellt. Die oberflachenaktiven Eigenschaften dieser Stoffe werden verglichen und einige Analysenmethoden zur Identifizierung und Ermittlung ihrer Zusammensetzung behandelt.

A variable frequency square wave generator with single time constant circuit

Abstract: A linear amplifier, a clipping circuit and a differentiating network, connected in regenerative mode, produce discontinuous oscillations. Such a circuit can be successfully used for generation of square waves of frequency varying over a fairly wide range. The paper presents an analysis and design features of a square wave generator using the above technique. Practical circuits using both C—R and R—L differentiating networks have been given and test results have been discussed.

Thermal Metamorphism of the Banded Iron Formation of Orissa, India

Abstract: Effect of thermal metamorphism on the sedimentary iron formation of Orissa by basic igneous intrusives is described. Two mineral assemblages, quartz-cummingtonite-grunerite-magnetite with amosite and quartz-actinolite-zoisite-magnetite have been developed at the contact of the banded iron formation and the gabbro. The contact rocks show typical hornfelsic texture. The mineralogical assemblages indicate albite-epidote hornfels to hornblende hornfels facies of thermal metamorphism. The metamorphism took place under high water vapor pressure at a temperature of about 800° ± 50° C, which was confirmed by the decomposition temperature of amosite and also by the temperature of formation of cummingtonite. The banded iron formation consists of alternate bands of fine-grained iron oxide and cherty or cryptocrystalline silica. The basic igneous complex has been differentiated into pyroxenites, olivine gabbro, normal gabbro without olivine, anorthositic gabbro, norite, granodiorite and leucogranite. From the chemical analyses of the contact rocks and their mineralogical and textural studies, it has been established that the metamorphism of the iron-formation was accompanied by the introduction of Ca and Mg from gabbro to the iron formation. Cummingtonite was formed by the reaction of quartz and magnetite. Chemical analysis and X-ray powder photograph data of the mineral amosite are also given.

Electrophoresis of absorbed RNA.

Abstract: The electrophoretic mobilities of adsorbed yeast ribonucleic acid have been measured as functions of pH, ionic strength, and biopolymer concentration and the results so obtained have been critically compared with those for adsorbed DNA. Like DNA, ribonucleic acid has also been found to reverse the positive charge of alumina owing to its adsorption on the solid-liquid interface. The mobilities of adsorbed RNA have been found to be less than those of adsorbed DNA under identical conditions. The observed mobilities of adsorbed heat- and alkali-denatured RNA are significantly less than those of adsorbed native RNA at a given pH and ionic strength of the medium. The electrophoretic mobilities as observed also show the evidence of RNA adsorption on the negatively charged surface of Dowex-50 resin, but practically no adsorption of RNA on the negatively charged glass surface has been predicted.

Juras-Cretaceous Stratigraphy and Sedimentation Around Jabalpur, M.P., and Their Paleogeographic Implications

Abstract: The Lameta and jabalpur Groups, which are redefined and described in their type area, are separated by an unconformity at Dalpatpur. The unconformity grades to a paraeonformity of much lesser magnitude in the vicinity of jabalpur town. Local paleocurrents in the type area, directions of truncations and relative rates of change of stratigraphic hiatus across the unconformities and configuration of pre-trappean surface appear to be mutually related to each other. All these features suggest the existence of a westerly slope corresponding to Krishnan's' Narmada Trough' since the Jurassic period. While the Jabalpurs are the products of a typical flood plain in an interior basin, the Lametas appear to represent shallow marine sediments on the stable shelf. The terrigenous constituents of the Jabalpur Group are mainly derived from the pelitic metasediments in the east. The terrigenous constituents of the Lametas, on the other hand, represent a mixed assemblage of detritus derived from the local jabalpurs and pelitic metasediments. Diagenesis of the ]abalpur sediments mainly involves endogenic reconstitution. Exogenic cements in the lametas are mainly derived from the overlying Deccan Trap.

A wide-range linear delay circuit†

Abstract: A wide-range linear delay circuit is described. Such circuits have wide applications. The present circuit, which has excellent temperature stability, employs a compensated bootstrap circuit for generation of a linear ramp waveform and a regenerative Schmitt triggor comparator. The circuit provides good performance and sharp waveforms which may be used for triggering other digital circuits directly.

Analysis of single reactor reversible output magnetic amplifier

Abstract: A single reactor in series with a symmetrical non-linear resistance and the load, oxcited by a.c. line voltage, gives bi-directional d.c. output across the load when polarized by a d.c. magnetizing force. Its simplicity, low drift and low quiescent power loss make the circuit interesting. The operating principle of the amplifier is somewhat different from that of the self-satnratiiig type. The main difference is the available flux re-setting time interval which is less than a half-cycle of the supply frequency. The transfer characteristic of such amplifiers depends mainly on the amount of flux re-set during the re-set interval. A new method of measurement of the flux re-setting characteristics of cores has been presented and with the characteristics thus obtained the analysis of the amplifier has been made with a non-idealized B—H loop. The normalized transfer characteristics for various available re-set intervals have been drawn, enabling one to determine the output voltage-input current relations of suc...

A linear voltage-controlled triangle/square wave generator†

Abstract: A new circuit for generation of triangle/square waveform is described. The circuit uses a linear pulse amplifier, a clipper and a differentiating network, consisting of a capacitance and a FET behaving as a voltage-controlled resistor. The circuit covers a wide frequency range and the variation of frequency with the control voltage is fairly linear.

Positronium formation in the reactions of positron with hydrogenlike atoms

Abstract: The cross-section for positronium formation in positron-hydrogen collisions has been calculated in the lowest-order approximation from the viewpoint of field theory for bound states in quantum electrodynamics. The result is then compared with that of Massey and Mohr and seems to be better as regards the position of the peak value.

Measurement of diffusion length and surface recombination velocity in semiconducting solids

Abstract: A two-dimensional diffusion theory taking surface recombination into account is utilized for measurement of the diffusion length L in semiconducting solids. Methods for simultaneous measurement of L and surface recombination velocity, and a scheme for further refinement in observation, are also indicated.

Propagation of one-dimensional unloading waves in materials exhibiting yielding delay phenomena

Abstract: The nature of possible unloading waves in materials exhibiting yielding delay phenom ena has been discussed in this paper. The differential equation governing the propagation of the waves, has been solved by this method of characteristics. In this case also as in materials not exhibiting yielding delay phenomena, the unloading wave propagates with the velocity of elastic waves, if it is a wave of discontinuity, and if the load is suddenly increased the unloading wave travels with plastic wave velocity.