Stability of Accelerated Expansion in Nonlinear Electrodynamics

This paper is devoted to study the phase space analysis of isotropic and homogenous universe model by taking a noninteracting mixture of electromagnetic and viscous radiating fluids whose viscous pressure satisfies a nonlinear version of the Israel-Stewart transport equation. We establish an autonomous system of equations by introducing normalized dimensionless variables. In order to analyze stability of the system, we find corresponding critical points for different values of the parameters. We also evaluate power-law scale factor whose behavior indicates different phases of the universe model. It is concluded that bulk viscosity as well as electromagnetic field enhances the stability of accelerated expansion of the isotropic and homogeneous universe model.Comment: 17 pages, 5 figures, accepted for publication in EPJ

Ant Species Richness Around Amravati City Maharashtra, India

Ants deserve a special place in the study of ecology, including behavior, given their species richness, social habits, and high densities, contributing to much of the animal biomes on earth (Gadagkar et.at. 1993). As ants can be studied virtually everywhere from forest interiors below ground, right up to the kitchen, we attempted a study to assess the ant species richness in a variety of habitats in and around Amravati city. The prime objective of this study is to prepare a partial checklist of ants of Amravati and to compare species richness between selected study sites. Eight study sites with different levels and types of vegetation were selected for the study.
We employed an “all out search” method for collection in the months of June and July 2010. Ants were hand collected using a brush and forecep during the day time for 6 hrs at each study site. Collected samples were preserved in 70% alcohol in the Department of Zoology, Govt. Vidarbha Institute of Science & Humanities, Amravati.
We identified Ants up to the genus level by using a Stemi DV4 Stereo microscope based on taxonomic keys of (Holldobles & Wilson, 1990; Bolton, 1994; Mathew & R.N. Tiwari, 2000).
During the present study a total of 34 species of 20 genera have been recognized from Amravati city representing five subfamilies namely Myrmicinae, Formicinae, Ponerinae, Dolichoderinae and Pseudomyrmicinae. Out of this subfamily, Myrmicinae is the most abundant having 11 genera including the genus Rhoptromyrmex. It has been recorded for the first time in this region, followed by Formicinae with four genera for being recorded for the first time as genus Oecophylla. Subfamily Ponerinae and Dolichoderinae were recorded only with two genera each; while the subfamily Pseudomyrmicinae where recorded very poorly with only one genera from G.V.I.S.H. campus.
Few ant genera such as Crematogaster and Myrmicaria of subfamily Myrmicinae, Camponotus and Polyrhachis of subfamily Formicinae and Leptogenys of subfamily Ponerinae were mostly found in all the habitats and most localities. Few genera are confined to few localities or habitat types, such as Rhoptromyrmex and Oecophylla recorded only from Pohara forests. Genus Tetraponera of subfamily Pseudomyrmicinae were collected from the tree trunk of Azadirakhta indica in the G.V.I.S.H. campus. 
Comparison of ant species distribution between the different study sites revealed that ant species richness was highest in Pohara forest with 28 species & lowest with 9 species around urban areas. Relatively high ant species richness was recorded at all the study sites such as the Agriculture field, Tree plantation area, and the Wadali and Chhatri Garden. On the other hand, ant species richness was low around urban houses compared to rural houses due to little or no vegetation and high levels of disturbance. The tree plantation site, roads, and pavement showed higher numbers of ant species compared to around urban areas probably due to road side richness of tree plantation.
From this study we conclude that due to availability of food and shelter, richness of ant species increases in forest and tree plantation areas. The number of ant species declines in low vegetative areas including urban areas. It is possible to study the ecology and biodiversity of living faunas by the studying the habitats of ants. The environs of Amravati city are rich in Ant fauna which deserve further study