656 research outputs found

    The effect of density dependent emigration on spread of infectious diseases: a modelling study

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    In this study, we proposed and analyzed an SIS mathematicalmodel by considering population densitydependent emigration. It is assumed that the diseaseis transmitted by direct contact of infective and susceptiblepopulations. We also assumed that the rate ofcontact is emigration dependent i.e. contact rate is variablewhich depends on the current population of habitatas well as on non-emigrating population density of habitat.The equilibria and their stability are studied by usingthe stability theory of differential equations and simulation.The model analysis shows that the spread of infectiousdisease in habitat decreases if the rate of emigrationincreases but it increases as the population density of nonemigratingpopulation increases. The simulation study ofthe model confirms these analytical results

    Fixed Points of α-Admissible Mappings in Cone Metric Spaces with Banach Algebra

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    In this paper, we introduce the α\alpha-admissible mappings in the setting of cone metric spaces equipped with Banach algebra and solid cones. Our results generalize and extend several known results of metric and cone metric spaces. An example is presented which illustrates and shows the significance of results proved herein

    Alternative Technique for "Complex" Spectra Analysis

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    . The choice of a suitable random matrix model of a complex system is very sensitive to the nature of its complexity. The statistical spectral analysis of various complex systems requires, therefore, a thorough probing of a wide range of random matrix ensembles which is not an easy task. It is highly desirable, if possible, to identify a common mathematcal structure among all the ensembles and analyze it to gain information about the ensemble- properties. Our successful search in this direction leads to Calogero Hamiltonian, a one-dimensional quantum hamiltonian with inverse-square interaction, as the common base. This is because both, the eigenvalues of the ensembles, and, a general state of Calogero Hamiltonian, evolve in an analogous way for arbitrary initial conditions. The varying nature of the complexity is reflected in the different form of the evolution parameter in each case. A complete investigation of Calogero Hamiltonian can then help us in the spectral analysis of complex systems.Comment: 20 pages, No figures, Revised Version (Minor Changes

    Optical absorption in boron clusters B6_{6} and B6+_{6}^{+} : A first principles configuration interaction approach

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    The linear optical absorption spectra in neutral boron cluster B6_{6} and cationic B6+_{6}^{+} are calculated using a first principles correlated electron approach. The geometries of several low-lying isomers of these clusters were optimized at the coupled-cluster singles doubles (CCSD) level of theory. With these optimized ground-state geometries, excited states of different isomers were computed using the singles configuration-interaction (SCI) approach. The many body wavefunctions of various excited states have been analysed and the nature of optical excitation involved are found to be of collective, plasmonic type.Comment: 22 pages, 38 figures. An invited article submitted to European Physical Journal D. This work was presented in the International Symposium on Small Particles and Inorganic Clusters - XVI, held in Leuven, Belgiu

    The Glauber model and the heavy ion reaction cross section

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    We reexamine the Glauber model and calculate the total reaction cross section as a function of energy in the low and intermediate energy range, where many of the corrections in the model, are effective. The most significant effect in this energy range is by the modification of the trajectory due to the Coulomb field. The modification in the trajectory due to nuclear field is also taken into account in a self consistent way. The energy ranges in which particular corrections are effective, are quantified and it is found that when the center of mass energy of the system becomes 30 times the Coulomb barrier, none of the trajectory modification to the Glauber model is really required. The reaction cross sections for light and heavy systems, right from near coulomb barrier to intermediate energies have been calculated. The exact nuclear densities and free nucleon-nucleon (NN) cross sections have been used in the calculations. The center of mass correction which is important for light systems, has also been taken into account. There is an excellent agreement between the calculations with the modified Glauber model and the experimental data. This suggests that the heavy ion reactions in this energy range can be explained by the Glauber model in terms of free NN cross sections without incorporating any medium modification.Comment: RevTeX, 21 pages including 9 Postscript figures, submitted to Phys. Rev.

    Tight-binding parameters for charge transfer along DNA

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    We systematically examine all the tight-binding parameters pertinent to charge transfer along DNA. The π\pi molecular structure of the four DNA bases (adenine, thymine, cytosine, and guanine) is investigated by using the linear combination of atomic orbitals method with a recently introduced parametrization. The HOMO and LUMO wavefunctions and energies of DNA bases are discussed and then used for calculating the corresponding wavefunctions of the two B-DNA base-pairs (adenine-thymine and guanine-cytosine). The obtained HOMO and LUMO energies of the bases are in good agreement with available experimental values. Our results are then used for estimating the complete set of charge transfer parameters between neighboring bases and also between successive base-pairs, considering all possible combinations between them, for both electrons and holes. The calculated microscopic quantities can be used in mesoscopic theoretical models of electron or hole transfer along the DNA double helix, as they provide the necessary parameters for a tight-binding phenomenological description based on the π\pi molecular overlap. We find that usually the hopping parameters for holes are higher in magnitude compared to the ones for electrons, which probably indicates that hole transport along DNA is more favorable than electron transport. Our findings are also compared with existing calculations from first principles.Comment: 15 pages, 3 figures, 7 table

    A Case of Problematic Diffusion

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    Sex determination techniques have diffused rapidly in India, and are being used to detect female fetuses and subsequently to abort them. This technology has spread rapidly because it imparts knowledge that is of great value within the Indian context, and because it fits in neatly with the modernization dynamic within India, which itself has enmeshed with traditional patriarchal institutions to oppress Indian women. More research needs to be done on ways to stem the adoption of problematic innovations.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68396/2/10.1177_107554709401500301.pd

    Measurement of Mass and Width of the W Boson at LEP

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    We report on measurements of the mass and total decay width of the W boson with the L3 detector at LEP. W-pair events produced in e+e\mathrm{e^+e^-} interactions between 161 GeV and 183 GeV centre-of-mass energy are selected in a data sample corresponding to a total luminosity of 76.7 pb1^{-1}. Combining all final states in W-pair production, the mass and total decay width of the W boson are determined to be MW=80.61±0.15\mathrm{M_W}=80.61\pm0.15 GeV and ΓW=1.97±0.38\Gamma_{\mathrm{W}}=1.97\pm0.38 GeV, respectively
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