Showing papers by "Indian Institute of Science published in 1985"
TL;DR: The period of discovery of new lipids in the nervous system appears to be over and all the major lipid components have been discovered and a great deal is now known about their structure and metabolism.
694 citations
TL;DR: In this article, the authors present a survey of recent experimental results in such situations and recent results and models are discussed, as well as several new results in various stages of publication.
311 citations
TL;DR: This paper first builds a Petri net model (PNM) of the given FMS in a bottom-up fashion and then analyzes important qualitative aspects of FMS behaviour such as existence/absence of deadlocks and buffer overflows.
Abstract: In this paper we present an approach for modelling and analyzing flexible manufacturing systems (FMSs) using Petri nets. In this approach, we first build a Petri net model (PNM) of the given FMS in a bottom-up fashion and then analyze important qualitative aspects of FMS behaviour such as existence/absence of deadlocks and buffer overflows. The basis for our approach is a theorem we state and prove for computing the invariants of the union of a finite number of Petri nets when the invariants of the individual nets are known. We illustrate our approach using two typical manufacturing systems: an automated transfer line and a simple FMS.
237 citations
TL;DR: In this article, the role of packing in the crystal of substituted coumarins has been investigated and the results pertaining to subtler aspects of topochemical postulates have been obtained.
Abstract: Solid-state photochemical behavior of 28 substituted coumarins has been investigated. Of these twelve underwent photodimerization and this is remarkable in light of the inertness of coumarin itself in the solid state. X-ray crystallographic investigation of eight coumarins was undertaken with the view of understanding the role of packing in the crystal on their solid-state reactivity. Important findings include the identification of acetoxy and chloro substituents as useful “crystal engineering” groups and the results pertaining to subtler aspects of topochemical postulates. X-ray crystal structure analyses of 7-chlorocoumarin and 7-methoxycoumarin reveal packing modes which are not commonly met. The former is arranged in a \beta type packing, the center-center distance between the reactive double bonds being 4.454 \AA, which lies beyond the so far accepted limit of 3.5-4.2 \AA. The reactive double bonds of 7-methoxycoumarin, on the other hand, are rotated by $65^O$ with respect to each other with the center-center distance between the double bonds being 3.83 \AA. Inspite of these unfavorable arrangements photodimerization of the above two coumarins in the solid state occurs through a topochemical process with large dimer yields. A careful analysis of the X-ray crystallographic resulta obtained from our investigations reveals that the two double bonds in the reactive crystals may be displaced with respect to each other both along the molecular plane as well as along the double bond axis. Thus the normally accepted dictums that in the photoreactive crystals the doube bonds should be within a distance of 4.2 \AA, and that they be parallel are no longer operational.
209 citations
TL;DR: It is shown that every strongly stabilizable plant can be reliably stabilized; moreover, one of the two controllers can be specified arbitrarily, subject only to the constraint that it should be stable.
186 citations
01 Jan 1985
TL;DR: The generality of this method of designing learning schemes is pointed out, and it is shown that a very minor modification will enable the algorithm to learn in a multiteacher environment as well.
Abstract: A new class of reinforcement schemes for learning automata that makes use of estimates of the random characteristics of the environment is introduced. Both a single automaton and a hierarchy of learning automata are considered. It is shown that under small values for the parameters, these algorithms converge in probability to the optimal choice of actions. By simulation it is observed that, for both cases, these algorithms converge quite rapidly. Finally, the generality of this method of designing learning schemes is pointed out, and it is shown that a very minor modification will enable the algorithm to learn in a multiteacher environment as well.
171 citations
TL;DR: It is shown that the large anomalous Hall constants of mixed-valence and Kondo-lattice systems can be understood in terms of a simple resonant-level Fermi-liquid model.
Abstract: We show that the large anomalous Hall constants of mixed-valence and Kondo-lattice systems can be understood in terms of a simple resonant-level Fermi-liquid model. Splitting of a narrow, orbitally unquenched, spin-orbit split, f resonance in a magnetic field leads to strong skew scattering of band electrons. We interpret both the anomalous signs and the strong temperature dependence of Hall mobilities in CeCu2Si2, SmB6, and CePd3 in terms of this theory.
164 citations
TL;DR: Interesting limiting cases forming coherent and quasihomogeneous fields are analyzed and another geometrical picture in a (2+1)-dimensional Minkowski space suitable for the description of the action of axially symmetric FOS’s on AGSM fields is developed.
Abstract: Anisotropic Gaussian Schell-model (AGSM) fields and their transformation by first-order optical systems (FOS’s) forming Sp(4,R) are studied using the generalized pencils of rays. The fact that Sp(4,R), rather than the larger group SL(4,R), is the relevant group is emphasized. A convenient geometrical picture wherein AGSM fields and FOS’s are represented, respectively, by antisymmetric second-rank tensors and de Sitter transformations in a (3+2)-dimensional space is developed. These fields are shown to separate into two qualitatively different families of orbits and the invariants over each orbit, two in number, are worked out. We also develop another geometrical picture in a (2+1)-dimensional Minkowski space suitable for the description of the action of axially symmetric FOS’s on AGSM fields, and the invariants, now seven in number, are derived. Interesting limiting cases forming coherent and quasihomogeneous fields are analyzed.
125 citations
TL;DR: In this article, a new phase in rapidly solidified Al-14at% Mn alloys is reported and diffraction patterns from this phase correspond to an icosahedral point group symmetry which is inconsistent with lattice translation.
113 citations
TL;DR: In this article, a structural model has been proposed for these glasses in which the basic feature is the presence of an extensive network of corner shared [ MoO 6 2 ] octahedra and [ POO 3 2 ] tetrahedra.
Abstract: Glasses in the system MoO3P2O5K2O have been studied over a wide range of compositions. Molar volumes, microhardnesses, glass-transition temperatures, heat capacities and infrared spectra of selected compositions have been measured and reported. A structural model has been proposed for these glasses in which the basic feature is the presence of an extensive network of corner shared [ MoO 6 2 ] octahedra and [ POO 3 2 ] tetrahedra. The effect of added K2O which degrades such a network and creates unshared corners has been considered in detail. The nature and concentration of various defects which depend upon glass composition and relative energies of the covalent linkages have also been considered in detail. The defects are consolidated into a structural-phase diagram which has been used to interpret the observed properties. The loss of oxygen during the preparation of glasses and its consequence upon the structure have also been discussed.
104 citations
TL;DR: In this paper, a modified method has been developed for the deposition of transparent semiconducting thin films of tin oxide, involving the chemical vapour phase oxidation of tin iodide, showing sheet resistances greater than 100 Ω/□ and an average optical transmission in the visible range exceeding 80%.
TL;DR: In this article, a fully computerized method for structural synthesis of geared kinematic chains is presented, which can be used to derive epicyclic gear drives, and the results obtained there are presented and discussed.
TL;DR: A comparison is made of the performance of a weather Doppler radar with a staggered pulse repetition time and a Radar with a random (but known) phase.
Abstract: A comparison is made of the performance of a weather Doppler radar with a staggered pulse repetition time and a radar with a random (but known) phase. As a standard for this comparison, the specifications of the forthcoming next generation weather radar (NEXRAD) are used. A statistical analysis of the spectral moment estimates for the staggered scheme is developed, and a theoretical expression for the signal-to-noise ratio due to recohering-filtering-recohering for the random phase radar is obtained. Algorithms for assignment of correct ranges to pertinent spectral moments for both techniques are presented.
TL;DR: A method is proposed to estimate the fuzzy membership function for pattern recognition purposes using a rational function approximation to the probability density function obtained from the histogram of a finite number of samples.
01 Dec 1985
TL;DR: It is entirely possible that the inability to devise natural enough assays for recognition prevents us from understanding the full potential of the kin recognition abilities of many animal species and much effort is now going into assessing the abilities of animals to discriminate between kin and non kin.
Abstract: Kin selection is a widely invoked mechanism to explain the origin and evolution of social behaviour in animals. Proponents of the theory of kin selection place great emphasis on the correlation between asymmetries in genetic relatedness created by haplodiploidy and the multiple origins of eusociality in the order Hymenoptera. The fact that a female is more closely related genetically to her full sister than to her daughters makes it more profitable for a Hymenopteran female, in terms of inclusive fitness, to raise full sisters rather than daughters or full siblings with a female biased sex ratio rather than offspring. This is sometimes referred to as the haplodiploidy hypothesis. In reality however, genetic relatedness between workers in social insect colonies and the reproductive brood they rear is far below 0·75, the value expected for full sisters, often below 0·5 the value expected between mother and daughter and, not uncommonly, approaching zero. Such values are on account of queen turnover, multiple mating by queens or polygyny. This situation raises doubts regarding the haplodiploidy hypothesis unless workers can discriminate between full and half sisters and preferentially direct their altruism towards their full sisters only. This would still mean an effective coefficient of genetic relatedness of 0·75 between altruist and recipient. For this to be possible however, workers should be able to recognise their full sisters inspite of growing up with and being habituated to an assortment of full sisters, half sisters and perhaps other even less related individuals. Even outside the Hymenoptera, social animals may find themselves growing up together in the company of individuals of varying degrees of relatedness. An ability to tell apart the more and less related individuals under such circumstances should favour kin selection. Much effort is now going into assessing the abilities of animals to discriminate between kin and non kin. In every case studied carefully so far, animals appear to be capable of recognising their kin. Ants, wasps, sweat bees, honey bees, frogs, toads, mice, rats, voles, squirrels, monkeys and even humans appear to be able to recognise their kin in one circumstance or another. An ability to recognize true genetic relatedness requires genetically specified recognition labels and these must therefore be present. Recent findings of the role of the histocompatibility system provides some clues to the possible nature of recognition labels. An ability to recognise full sisters for example, inspite of being habituated to full and half sisters requires not merely genetically specified labels but also recognition templates which are based on the characteristics of the individual animals making the recognition and not templates based on all animals one grows up with. Some animals such as honey bees, tadpoles and ground squirrels appear to have such templates but others such as sweat bees and some mice appear not to. It is entirely possible that our inability to devise natural enough assays for recognition prevents us from understanding the full potential of the kin recognition abilities of many animal species. In any case, genetically specified labels and self based templates should greatly facilitate the evolution of social behaviour by kin selection.
TL;DR: In this paper, the Metropolis algorithm has been generalized to allow for the variation of shape and size of the MC cell and a restricted MC integration in the nine dimensional space of the cell components also leads to the stable structure for the Lennard-Jones potential.
Abstract: The Metropolis algorithm has been generalized to allow for the variation of shape and size of the MC cell. A calculation using different potentials illustrates how the generalized method can be used for the study of crystal structure transformations. A restricted MC integration in the nine dimensional space of the cell components also leads to the stable structure for the Lennard-Jones potential.
TL;DR: In this article, it was shown that the cyanide precursors of the general formula can be decomposed in the rare earth trihydroxide structure and can be used to yield complex metal oxides.
TL;DR: In this article, an EPR signal with g=1.997 which acquires high intensity above TC is indicative of activation of the corresponding defect centers, possibly V′Ba.
TL;DR: In this article, the effect of surface layer reinforcement with glass fibres of unidirectional jute-rein forced epoxy composite on the flexural properties has been investigated.
Abstract: The effect of surface layer reinforcement with glass fibres of unidirectional jute-rein forced epoxy composite on the flexural properties has been investigated. Substantial increase in flexural modulus and strength with small amounts of reinforcement (for reinforcement ratio (t/d) < 0.3, where "t" and "d" are the respective thicknesses of glass reinforced plastic (GRP) shell and JRP core) were achieved. In addition, studies on the effect of moisture absorption of flexural properties revealed a significant im provement in moisture resistance of jute reinforced epoxy with hybridization. Though density analyses of these hybrids indicate an increase in density with hybridization, the considerable improvement of the normalized properties of jute-glass hybrids make them candidate materials for cost-effective applications. The work has also shown that the reinforcement (t/d) is more useful a parameter in the case of sandwich-type hybrid fibre composites. Analysis of failure modes of these composites loaded in flexure is also presented
TL;DR: Proline, a solute which accumulates during water stress, enhanced the incorporation of radioactive precursors into proteins; caused an increase in translatability of finger millet messengers in vitro; and stabilized the polyribosomes isolated from normal seedlings.
TL;DR: In this paper, it was shown that the set of first order systems that can be realized using axially symmetric thin lenses exhausts the entire SL(2, R) group; at most three lenses are needed to realize any element of this group.
Abstract: A first order optical system is investigated in full generality within the context of wave optics. The problem is reduced to a study of the ray transfer matrices. The simplest such systems correspond to axially symmetric propagation. Realization of such systems by centrally located lenses separated by finite distances is studied. It is shown that, contrary to the commonly held view, the set
of first order systems that can be realized using axially symmetric thin lenses exhausts the entire SL(2, R) group; at most three lenses are needed to realize any element of this group. In particular, the inverse of free propagation can be so realized. Among anisotropic systems it is again shown that every element of the lens group Sp(4, R) can be realized using a finite number of thin lenses.
TL;DR: In this article, the relativistic symmetry of the electromagnetic field vectors in the paraxial approximation is used to obtain the transverse character of the fields and the transformation properties of the vectorial fields by the optical systems.
Abstract: Using the relativistic symmetry of Maxwell's equations, the general structure of the electromagnetic field vectors in the paraxial approximation is obtained. The transverse character of the fields is fully accounted for. Transformation properties of the vectorial fields by the optical systems are derived. The treatment of the fields in terms of vector potentials is also given. The reviewer finds the results very interesting.
TL;DR: In this paper, the preparation of glasses in the system PbO-PbCl2 is described and the behavior of the glass transition temperatures, heat capacities and microhardnesses as a function of glass composition has been investigated.
Abstract: The preparation of glasses in the system PbO-PbCl2 is described. The behaviour of the glass transition temperatures, heat capacities and microhardnesses as a function of glass composition has been investigated. The variations are discussed in terms of the structural features of the glasses.
TL;DR: NMR and model building studies clearly favour a Met-Acc6 beta-turn solution conformation in the Acc6 analog, suggesting that the neutrophil receptor is capable of recognizing a folded peptide structure.
TL;DR: In this paper, X-ray powder diffraction data was used to show that a certain fraction of the donor doped BaTiO3 is cubic even at room temperature and that the cubic fraction increases with the donor content.
TL;DR: The pollen of Parthenium hysterophorus, an alien weed growing wild in India was found to be a potential source of allergic rhinitis and there was 66% correlation between skin test and RAST.
Abstract: The pollen of Parthenium hysterophorus, an alien weed growing wild in India was found to be a potential source of allergic rhinitis. A clinical survey showed that 34% of the patients suffering from rhinitis and 12% suffering from bronchial asthma gave positive skin-prick test reactions to Parthenium pollen antigen extracts. Parthenium-specific IgE was detected in the sera of sixteen out of twenty-four patients suffering from seasonal rhinitis. There was 66% correlation between skin test and RAST.
TL;DR: The possible physical and chemical forces controlling the volume change behavior of kaolinite in various solvents under no external load condition and from conventional oedometer measurements of kaolininite in several pore fluids were ascertained from the sediment volume of the material as discussed by the authors.
Abstract: The possible physical and chemical forces controlling the volume change behavior of kaolinite [1318-74-7] were ascertained from the sediment volume of kaolinite in various solvents under no external load condition and from conventional oedometer measurements of kaolinite in several pore fluids. The minimum sediment volume of $14.5 cm^3/10 g$ clay occupied by kaolinite in water where repulsive (R) forces were dominant indicated that the R contribution was insignificant for kaolinite. The maximum sediment volume of $25.0 cm^3/10 g$ clay in $C_6H_6$, where coulombic attraction forces were significant, suggested that electrostatic attraction between silicate sheets and midplane cations and van der Waals forces were not appreciable for kaolinite. The positive edge-negative face bonding of kaolinite particles in $C_6H_6$ was unlikely. The $3688 cm^{-1}$ band in the IR spectrum of a kaolinite-dimethylamine sample decreased by $10 cm^{-1}$ on H-bond formation of the solvent molecule with the exposed structural hydroxyls of the octahedral sheet. The adsorbed solvent molecules likely H-bonded with an adjacent clay particle as indicated by the decrease in sediment volume with increase in dipole moment of the solvent molecule. In the oedometer tests with various pore fluids, a high void ratio of approximate 1.3 was obtained for kaolinite in n-heptane, and hexane (\mu \simeq 0) at an external pressure of $1 kg/cm^2$ probably because the weakly bonded kaolinite particles were randomly oriented. At the corresponding applied pressure, a lower void ratio of 0.88 resulted in water (\mu = 1.84) where the stronger H-bond between flat layer surfaces of adjacent particles favored a parallel orientation of clay particles. The volume change behavior was essentially controlled by frictional forces and clay fabric. In nonpolar solvents the random arrangement of kaolinite particles and the frictional forces mobilized a high shear resistance on the application of a consolidation pressure, resulting in a lower compressibility. In a solvent with high dipole moment the parallel array of clay particles mobilized less shear resistance and produced a greater compression.
TL;DR: In this article, the effect of different modes of aeration and of pyrrhotite addition on the ball wear using mild steel, high carbon low alloy steel and austenitic stainless steel balls was evaluated.
TL;DR: In this article, the effect of high pressures on the various properties of the chalcogenide glasses is reviewed. The properties discussed include the mechanical, electrical, optical and magnetic properties.
Abstract: The effect of high pressures on the various properties of the chalcogenide glasses is reviewed. The properties discussed include the mechanical, electrical, optical and magnetic properties. The phenomena of the crystallization of the chalcogenide glasses under high pressure is also discussed.
TL;DR: In this paper, a controlled generation of cavitation is reported by seeding artificial nuclei in the boundary layer of an axisymmetric body by electrolysis, where the number of nuclei is controlled by varying the electrolysis voltage, polarity and the geometry of the electrode.
Abstract: Cavitation-noise measurements from an axisymmetric body with ‘controlled’ generation of cavitation are reported. The control was achieved by seeding artificial nuclei in the boundary layer by electrolysis. It was possible to alter the number density of nuclei by varying the electrolysis voltage, polarity and the geometry of the electrode. From the observed trend of cavitation-noise data it is postulated that there exists an ‘interference effect’ which influences cavitation noise. When the nucleus-number density is high and cavitation numbers are low this effect is strong. Under these conditions the properties of cavitation noise are found to differ considerably from those expected based on theories concerning noise from single-spherical-bubble cavitation.