University of Calcutta (informally known as Calcutta University or CU) is a collegiate public state university located in Kolkata, West Bengal, India.&nbsp;Within India it is recognized as a &quot;Five-Star University&quot; and accredited &quot;A&quot; Grade by National Assessment and Accreditation Council.

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The University of Calcutta has secured the Fifth position among the Universities of India in the prestigious &quot;Indian University Ranking 2019&quot; list, released by the NIRF of the Ministry of Human Resource Development, Government of India.

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It was established on 24 January 1857, and was one of the first institutions in Asia to be established as a multidisciplinary and Western-style university. Its alumni and faculty include several heads of state, heads of government, social reformers, prominent artists, only academy award winner and Dirac medal winner in India, many Fellows of the Royal Society and five Nobel laureates as of 2019 which is highest in South Asia.

University Of Calcutta

Applied Mathematics

Abstract: A theoretical investigation into the effect of negative ion population on dust acoustic wave propagation is presented in a self-gravitating dusty plasma consisting of electrons, negative ions, positive ions, and charged dust grains. The kappa distributed suprathermal electrons and Maxwellian ions are assumed. The inertial dust grain is assumed to have a variable charge which is negative or positive in the equilibrium condition depending on the population density of negative ion. A general fluid dispersion relation is derived by using continuity, momentum, and Poissons equations for electrostatic potential as well as gravitational potential. The analysis shows that the higher negative ion and suprathermal electron population favored the reduction of the decay rate when the equilibrium dust charge is negative. On the other hand, when the negative ion population increases, the equilibrium dust charge becomes positive. In this case, the negative ion and suprathermal electron population enhance the decay rate. Graphical abstract: [Figure not available: see fulltext.]. © 2020, EDP Sciences / Società Italiana di Fisica / Springer-Verlag GmbH Germany, part of Springer Nature.

World University root node

European Physical Journal D

The effect of negative ion population on dust acoustic wave propagation in a self gravitating Lorentzian dusty plasma

The oscillatory model of star formation in giant and dwarf galaxies have been studied through a dynamical open system. In addition to various dynamical processes involving fractional masses of hot, warm, and cold gases, the system is subjected to dissipative processes e.g. outflow from the gaseous component caused by supernovae explosion and subsequent ram pressure stripping within the oscillation period. This is more realistic than a previous model whichwas considered conservative. The present episodicmodel has been found to be unimodal in general contrary to discrete episodes of star formation of decreasing amplitudes as found for closed systems. The duty cycles under various parametric conditions derived, vary in the range (2.0-40.0) × 107 yr for giant galaxies contrary to longer time, for example 9.0 × 107- 1.0 × 109 yr for dwarf galaxies. This might be due to the low production rate of supernova in dwarf galaxies which reduces the evaporation rate of cold gas into hot gas making cold gas available for continuing the cycle for a longer time. The duty cycles have increased in both cases compared to the previous model by an order of one for giant galaxies and order of two for dwarf galaxies depending on the degree of dissipation. This might be due to the unimodal pattern of star formation which prevails for longer time in the late phase of galaxy evolution. Under very special parametric conditions limit cycles may occur i.e. star formation in discrete episodes, may occur involving one or more stable attractors especially in early-type dwarf and giant galaxies. Tendency of formation of multiple attractors are more likely in early-type giant spiral galaxies when the rate of dissipation is very slow. © 2020 Oxford University Press. All rights reserved.

Monthly Notices of the Royal Astronomical Society

Three-dimensional episodic model of star formation in galaxies in the presence of dissipation

A stochastic model of fragmentation of molecular clouds has been developed for studying the resulting Initial Mass Function (IMF) where the number of fragments, inter-occurrence time of fragmentation, masses and velocities of the fragments are random variables. Here two turbulent patterns of the velocities of the fragments have been considered, namely, Gaussian and Gamma distributions. It is found that for Gaussian distribution of the turbulent velocity, the IMFs are shallower in general compared to Salpeter mass function. On the contrary, a skewed distribution for turbulent velocity leads to an IMF which is much closer to Salpeter mass function. The above result might be due to the fact that strong driving mechanisms e.g. shocks, arising out of a big explosion occurring at the centre of the galaxy or due to big number of supernova explosions occurring simultaneously in massive parent clouds during the evolution of star clusters embedded into them are responsible for stripping out most of the gas from the clouds. This inhibits formation of massive stars in large numbers making the mass function a steeper one. © 2020 Elsevier B.V.

Fulltext

New Astronomy

Random fragmentation of turbulent molecular clouds lying in the central region of giant galaxies

The aim of this paper is to investigate the dynamical behavior of a two-species predator-prey model with Holling type IV functional response and nonlinear predator harvesting. The positivity and boundedness of the solutions of the model have been established. The considered system contains three kinds of equilibrium points. Those are the trivial equilibrium point, axial equilibrium point and the interior equilibrium points. The trivial equilibrium point is always saddle and stability of the axial equilibrium point depends on critical value of the conversion efficiency. The interior equilibrium point changes its stability through various parametric conditions. The considered system experiences different types of bifurcations such as Saddle-node bifurcation, Hopf bifurcation, Transcritical bifurcation and Bogdanov-Taken bifurcation. It is clear from the numerical analysis that the predator harvesting rate and the conversion efficiency play an important role in stability of the system. © 2020 World Scientific Publishing Company.

Journal of Biological Systems

Bifurcation analysis of a two-dimensional predator-prey model with holling type iv functional response and nonlinear predator harvesting

This paper describes a co-infected two-strain Dengue model with bilinear infection rate. Three efforts, namely awareness efforts to protect human from mosquitoes bites, treatment efforts for infected human and mosquitoes killing efforts are considered to eradicate the infections. The treatment reproduction number R of the model is derived, which provides whether Dengue can persist or not. The existence and the stability analysis of different equilibrium points have been investigated. Sotomayor theorem is employed to prove the existence of transcritical bifurcation of the model. The sensitivity analysis has been performed to identify the most effective parameter for controlling the Dengue infection. The model is also used as an optimal control problem as all the three efforts are considered as time dependent functions. The Pontryagin’s maximum principle has been used to characterize the optimal control. Numerical results show the positive impacts for implementing three controls to reduce the Dengue infections. Finally efficiency analysis is carried out, which shows that awareness efforts to protect human from mosquitoes bites along with treatment is more effective than the mosquitoes killing efforts along with treatment. © 2020, Springer Nature India Private Limited.

International Journal of Applied and Computational Mathematics

Qualitative Analysis and Optimal Control of a Two-Strain Dengue Model with its Co-infections

The model of the equations of generalized thermoelasticity based on the Lord–Shulman's theory with nonlocal elasticity effect is used to study the photothermal waves in a semiconducting medium. The exact expressions for the displacement components, temperature, carrier density, and stress components are obtained by using normal mode analysis. Numerically simulated results are obtained and presented graphically for silicon. The comparisons are shown graphically to explore the effects of the time and the elastic nonlocal parameter on the different physical quantities. © 2020 Informa UK Limited, trading as Taylor & Francis Group.

Waves in Random and Complex Media

L–S theory for the propagation of the photo-thermal waves in a semiconducting nonlocal elastic medium

The effects of a new type of asynchronous updating on the dynamical behavior of coupled chaotic maps with nearest neighbor as well as global coupling are studied in this paper. In contrast to synchronous updating, the occurrence of the synchronized fixed point window is observed in the parameter space for nearest neighbor interactions as a consequence of asynchronous updating. Moreover, the effects of variation of the degree of asynchronocity have been investigated and it is observed that the size of the synchronized fixed point window strongly depends on the degree of asynchronocity. The value of coupling constant at the point of onset of synchronization is found analytically and the result is in good agreement with the numerics. Lattice size also has a significant impact on the synchronization behavior for some coupling function. On the other hand in a globally coupled network, synchronization is identified for a certain range of the degree of asynchronocity but surprisingly the width of synchronized fixed point window is independent of the value of the asynchronocity parameter. This study may be useful to explain the spatiotemporal order structure observed in spatially extended complex biological and social systems with the help of stochastic asynchronous updating. © 2020 IOP Publishing Ltd.

Physica Scripta

Complex dynamics of coupled map lattices under random asynchronous updating

The present study is concerned with the reflection and propagation of thermoelastic plane waves from the stress-free and thermally insulated surface of a homogeneous, isotropic thermally conducting elastic half-space in the frame of modified Green–Lindsay theory of generalized thermoelasticity with two-temperature (2TMGL). The thermoelastic coupling effect creates two types of coupled longitudinal waves which are dispersive as well as exhibit attenuation. Different from the thermoelastic coupling effect, there also exists one independent vertically shear-type (SV-type) wave. In contrast to the classical Green–Lindsay (GL) and Lord–Shulman (LS) theories of generalized thermoelasticity, the SV-type wave is not only dispersive in nature but also experiences attenuation. Analytical expressions for the amplitude ratios and their respective energy ratios for reflected thermoelastic waves are determined when a coupled longitudinal wave is made incident on the free surface. The paper concludes with the numerical results on the phase speeds, amplitude ratios and their respective energy ratios for specific parameter choices. Various graphs have been plotted to analyze the behavior of these quantities. The characteristics of employing the 2TMGL model are discussed by comparing the numerical results obtained for the present model with those obtained in case of the two-temperature Green–Lindsay (2TGL) and two-temperature Lord–Shulman (2TLS) models. © 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

ZAMM Zeitschrift fur Angewandte Mathematik und Mechanik

Thermoelastic plane waves under the modified Green–Lindsay model with two-temperature formulation

The main goal of this article is to find the approximate solution of the space-time fractional order KdV (STFKdV) equation and Coupled KdV (STFCKdV) equations by using Homotopy analysis method (HAM). A comparison of the exact solutions and approximate solutions has been shown from where we can say HAM is very effective and convenient for solving non linear fractional differential equation (NLFDE). © 2020 The Physical Society of Japan

Journal of the Physical Society of Japan

Approximate solution of space-time fractional KDV equation and coupled KDV equations

In this article, we have considered a continuous tritrophic food chain model subject to the Allee effect on the prey growth function with prey-dependent Holling type II functional response between the prey and intermediate predator; Crowley-Martin senses functional response between intermediate predator and top predator, and the top predator is of sexually reproductive type. We have established the positivity and boundedness of the system and the condition of existence of different equilibrium points. The local and global stability of the solutions about the various equilibrium points has been investigated. The center manifold theorem has been used to find the nature of the solution in the neighborhood of the nonhyperbolic equilibrium points and the direction of Hopf bifurcations. Numerical simulation has been carried out to establish the theoretical findings and finally some concluding remarks are given. © 2019 John Wiley &amp; Sons, Ltd.

Computational and Mathematical Methods

Global dynamics of a tritrophic food chain model subject to the Allee effects in the prey population with sexually reproductive generalized-type top predator