Gravitational Field of Domain Walls in Higher Dimension

In this paper, we study the gravitational field of domain wall in fivedimensional space-time. Exact solutions of Einstein's equations for a scalarfield with a potential V(Ø) are presented, describing thegravitational field of plane symmetric domain walls. The solution showsthat the energy density as well as pressure in the perpendicular directionon both sides of the walls to be reflection symmetric with respect to thewalls.PACS numbers: 98.80 cq, 0450     

Anisotropic cosmological models with bulk viscosity for variable <Emphasis Type="Italic">G</Emphasis> and Λ

In this paper we have considered axially symmetric Bianchi-I, Kantowski Sachs and Bianchi-III space-time models with bulk viscosity, where the gravitational constant G and the cosmological term Λ vary with time. In Einstein equations this variation in G and Λ are taken in such a way as to preserve the energy momentum tensor. Solutions are obtained with the cosmological term varying inversely with square of time.     

Effect of modified Chaplygin gas in anisotropic universe

In this work, we have studied the model of modified Chaplygin gas and its role in accelerating phase of the universe for anisotropic model. We have assumed that the equation of state of this modified model is valid from the radiation era to ΛCDM model. We have obtained the possible relation between the hessence and the modified Chaplygin gas. We have also use the statefinder parameters for characterize different phase of the universe diagrammatically.     

Thermodynamics of the universe filled with perfect fluid having variable equation of state

Recently, a field theoretic model for a UV complete theory of gravity has been proposed by Hor̃ava. This theory is a non-relativistic renormalizable gravity theory which coincides with Einstein’s general relativity at large distances. Subsequently Lü et al. have formulated the modified Friedmann equations and have presented a solution in vacuum. In the present work, we rewrite the modified FRW equations in the form of usual FRW equations in Einstein gravity and consequences have been analyzed. Also the thermodynamics of the FRW universe has been studied.     

Structure and stability of rotating fluid disks around massive objects. I. Newtonian formulation

In this paper we have presented a very general class of solutions for rotating fluid disks around massive objects (neglecting the self gravitation of the disk) with density as a function of the radial coordinate only and pressure being nonzero. Having considered a number of cases with different density and velocity distributions, we have analysed the stability of such disks under both radial and axisymmetric perturbations. For a perfect gas disk with γ= 5/3 the disk is stable with frequency (MG/r³)^1/2 for purely radial pulsation with expanding and contracting boundary. In the case of axisymmetric perturbation the critical γ_c for neutral stability is found to be much less than 4/3 indicating that such disks are mostly stable under such perturbations. On leave of absence from Government College, Jagdalpur 494005.     

Variability of cloud liquid water and ice over South Asia from TMI estimates

In this study, the Tropical Rainfall Measurement Mission based Microwave Imager estimates (2A12) have been used to compare and contrast the characteristics of cloud liquid water and ice over the Indian land region and the ocean surrounding it, during the premonsoon (May) and monsoon (June–September) seasons. Based on the spatial homogeneity of rainfall, we have selected five regions for our study (three over ocean, two over land). Comparison across three ocean regions suggests that the cloud liquid water (CLW) over the orographically influenced Arabian Sea (close to the Indian west coast) behaves differently from the CLW over a trapped ocean (Bay of Bengal) or an open ocean (equatorial Indian Ocean). Specifically, the Arabian Sea region shows higher liquid water for a lower range of rainfall, whereas the Bay of Bengal and the equatorial Indian Ocean show higher liquid water for a higher range of rainfall. Apart from geographic differences, we also documented seasonal differences by comparing CLW profiles between monsoon and premonsoon periods, as well as between early and peak phases of the monsoon. We find that the CLW during the lean periods of rainfall (May or June) is higher than during the peak and late monsoon season (July–September) for raining clouds. As active and break phases are important signatures of the monsoon progression, we also analysed the differences in CLW during various phases of the monsoon, namely, active, break, active-to-break and break-to-active transition phases. We find that the cloud liquid water content during the break-to-active transition phase is significantly higher than during the active-to-break transition phase over central India. We speculate that this could be attributed to higher amount of aerosol loading over this region during the break phase. We lend credence to this aerosol-CLW/rain association by comparing the central Indian CLW with that over southeast Asia (where the aerosol loading is significantly smaller) and find that in the latter region, there are no significant differences in CLW during the different phases of the monsoon. While our hypothesis needs to be further investigated with numerical models, the results presented in this study can potentially serve as a good benchmark in evaluating the performance of cloud resolving models over the Indian region.     

Utility of orbital surveillance system for snow monitoring in the Indian context

Since snow covered areas in the Himalayas contribute significantly to the discharge of the major rivers of North India, snow monitoring is essential for effective control and management of the available water resources, particularly in the lean period. As accumulation and melting of snow are dynamic processes the need arises for periodic monitoring. Conventional survey methods are time consuming and expensive due to adverse terrain conditions and weather. As such, updating information at reasonably frequent intervals calls for a strategy invoiving remote sensing techniques. Potentials of such techniques such as aerial and orbital photography and multispectral scanning systems as also microwave sensing systems are briefly discussed. Particular emphasis is laid on a Landsat type surveillance system, which is at the operational stage. As a case study demonstrating the system capability an area in the Sutlej catchment has been analysed on Landsat imagery acquired in October and December, 1972. The snow covered area is found to be considerably more in the December, 72 imagery. Such a map overlaid on a contoured 1:250,000 base updated every month can be useful input attempts at watershed modelling incorporating other dynamic features also.     

New technologies, old divides: linking internet access to social and locational characteristics of US farms

Access to new information and communication technologies is widely viewed as a prerequisite for participation in the global economy, so that inequalities in such access have become a significant policy concern. Rural areas are especially underserved in terms of internet providers, and this is true in both developed and less developed economies. This article focuses on access to the internet within farming operations in the US as an important aspect of understanding the digital divide within rural areas. Using county level data from the 2007 US Census of Agriculture and multivariate regression analysis, our study examines the statistical relationship between farm internet access and a set of explanatory factors which include demographic characteristics of operators, economic characteristics of farms, and geographic location (region and metropolitan status) of the farm. Further, it seeks to understand whether access to the internet can be socially and locationally differentiated from access to high speed internet. Our findings indicate that existing social divides are replicated in terms of the digital divide, so that social inequalities are potentially a more pressing problem than infrastructural gaps in terms of rural access to the internet in the US.     

On the vibrations of a composite orthotropic cylinder placed in a magnetic field

Summary The problems of radial vibration of a composite orthotropic cylinder subjected to a uniform axial magnetic field forms the chief interest of the paper.