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Bali R.,University of Rajasthan | Yadav M.K.,Dr. Harisingh Gour Vishwavidyalaya | Gupta L.K.,University of Rajasthan
Canadian Journal of Physics

In the present study, a locally rotationally symmetric Bianchi type II string dust cosmological model with varying bulk viscosity in the framework of Lyra geometry is investigated. To get the deterministic solution, we have assumed that shear (σ) is proportional to the expansion (θ) and ζθ = constant, where ζ is the coefficient of bulk viscosity. The ansatz ζθ = constant, was found to coincide with the occurrence of Little Rip (LR) cosmology using Friedmann-Robertson-Walker metric (Breviket al. Phys. Rev. D, 84, 103508-1-6 (2011)). The model describes the pre-inflationary stage of the universe. The presence of viscosity leads to inflationary-like solutions. Anisotropy is maintained because of the presence of strings. The presence of bulk viscosity prevents the matter density from vanishing. In a special case, the model represents the isotropy of the universe. The universe passes through a decelerating stage to an accelerating phase, which is in agreement with Ries et al.s (Astrophys. J. 607, 665 (2004). doi:10.1086/383612) type Ia supernovae astronomical observations. The displacement vector (β) of Lyra geometry is a decreasing function of time analogous to the cosmological constant (λ) of general relativity. We have attempted to explore the possibility of constructing a string dust viscous fluid cosmological model in Bianchi type II space-time with displacement vector (β) in Lyra geometry using the geometric condition that shear is proportional to expansion. © 2014 Published by NRC Research Press. Source

Jatav K.S.,Dr. Harisingh Gour Vishwavidyalaya | Dhar J.,ABV Indian Institute of Information Technology and Management
Nonlinear Analysis: Hybrid Systems

The agricultural pests can be controlled effectively by simultaneous use (i.e., hybrid approach) of biological and chemical control methods. Also, many insect natural enemies have two major life stages, immature and mature. According to this biological background, in this paper, we propose a three tropic level plant-pest-natural enemy food chain model with stage structure in natural enemy. Moreover, impulsive releasing of natural enemies and harvesting of pests are also considered. We obtain that the system has two types of periodic solutions: plant-pest-extinction and pest-extinction using stroboscopic maps. The local stability for both periodic solutions is studied using the Floquet theory of the impulsive equation and small amplitude perturbation techniques. The sufficient conditions for the global attractivity of a pest-extinction periodic solution are determined by the comparison technique of impulsive differential equations. We analyze that the global attractivity of a pest-extinction periodic solution and permanence of the system are evidenced by a threshold limit of an impulsive period depending on pulse releasing and harvesting amounts. Finally, numerical simulations are given in support of validation of the theoretical findings. © 2013 Elsevier Ltd. Source

Saxena A.,Dr. Harisingh Gour Vishwavidyalaya | Upadhyay R.,Dr. Harisingh Gour Vishwavidyalaya | Kango N.,Dr. Harisingh Gour Vishwavidyalaya
Indian Journal of Experimental Biology

Over the recent years glutaminase free L-asparaginase has gained more importance due to better therapeutic properties for treatment of acute lymphoblastic leukemia. Actinomycetes are known for L-asparaginase activity. In the current study, 80 actinomycetes were isolated from various soil habitats by serial dilution technique. Presence of L-asparaginase was investigated in a total of 240 actinomycetes by tubed agar method using modified M-9 medium. A total of 165 actinomycetes were found positive for L-asparaginase activity. Among these, 57 actinomycetes producing larger zones of L-asparagine hydrolysis were further screened for their capacity to produce glutaminase-free L-asparaginase. Four L-glutaminase-free actinomycetes were found to be potential L-asparaginase producers. These actinomycetes were identified as Streptomyces cyaneus (SAP 1287, CFS 1560), S. exfoliates (CFS 1557) and S. phaeochromogenes (GS 1573) on the basis of morphological and biochemical identification studies. Maximum L-asparaginase activity (19.2 Uml-1) was observed in culture filtrate of S. phaeochromogenes under submerged fermentation. Results indicate that S. phaeochromogenes could be a potential source of glutaminase free L-asparaginase for commercial purpose. To the best of our knowledge, this is the first report on production of glutaminase free L-asparaginase from S. cyaneus, S. exfoliatus and S. phaeochromogenes. © 2015, National Institute of Science Communication. All rights reserved. Source

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