Well behaved class of charge analogue of Heintzmann’s relativistic exact solution

We present a well behaved class of Charge Analogue of Heintzmann (Z. Phys. 228:489, 1969) solution. This solution describes charge fluid balls with positively finite central pressure and positively finite central density ; their ratio is less than one and causality condition is obeyed at the centre. The outmarch of pressure, density, pressure-density ratio and the adiabatic speed of sound is monotonically decreasing, however, the electric intensity is monotonically increasing in nature. The solution gives us wide range of constant K (1.25≤K≤15) for which the solution is well behaved and therefore, suitable for modeling of super dense star. For this solution the mass of a star is maximized with all degrees of suitability and by assuming the surface density ρ _b =2×10¹⁴ g/cm³. Corresponding to K=1.25 and X=0.42, the maximum mass of the star comes out to be 3.64M _Θ with linear dimension 24.31 km and central redshift 1.5316.     

Variety of Well behaved parametric classes of relativistic charged fluid spheres in general relativity

The paper presents a variety of classes of interior solutions of Einstein–Maxwell field equations of general relativity for a static, spherically symmetric distribution of the charged fluid with well behaved nature. These classes of solutions describe perfect fluid balls with positively finite central pressure, positively finite central density; their ratio is less than one and causality condition is obeyed at the center. The outmarch of pressure, density, pressure–density ratio and the adiabatic speed of sound is monotonically decreasing for these solutions. Keeping in view of well behaved nature of these solutions, two new classes of solutions are being studied extensively. Moreover, these classes of solutions give us wide range of constant K for which the solutions are well behaved hence, suitable for modeling of super dense star. For solution (I₁) the mass of a star is maximized with all degree of suitability and by assuming the surface density ρ _b =2×10¹⁴ g/cm³ corresponding to K=1.19 and X=0.20, the maximum mass of the star comes out to be 2.5M _Θ with linear dimension 25.29 Km and central redshift 0.2802. It has been observed that with the increase of charge parameter K, the mass of the star also increases. For n=4,5,6,7, the charged solutions are well behaved with their neutral counterparts however, for n=1,2,3, the charged solution are well behaved but their neutral counterparts are not well behaved.     

Well-behaved relativistic charged super-dense star models

A new class of charged super-dense star models is obtained by using an electric intensity, which involves a parameter, K. The metric describing the model shares its metric potential g ₄₄ with that of Durgapal’s fourth solution (J. Phys. A, Math. Gen. 15:2637, 1982). The pressure-free surface is kept at the density ρ _b =2×10¹⁴ g/cm³ and joins smoothly with the Reissner-Nordstrom solution. The charge analogues are well-behaved for a wide range, 0≤K≤59, with the optimum value of X=0.264 i.e. the pressure, density, pressure–density ratio and velocity of sound are monotonically decreasing and the electric intensity is monotonically increasing in nature for the given range of the parameter K. The maximum mass and the corresponding radius occupied by the neutral solution are 4.22M _Θ and 20 km, respectively for X=0.264. For the charged solution, the maximum mass and radius are defined by the expressions M≈(0.0059K+4.22)M _Θ and r _b ≈−0.021464K+20 km respectively.     

Simulated Heat Content Variability in the Upper Layers of the Tropical Indian Ocean

Ocean General Circulation Model (OGCM) simulations from 1970–2007 are used to study the upper ocean heat content variability in the Tropical Indian Ocean (TIO). Model computed heat contents up to 50 m (denoted by HC50 m hereafter) representing upper ocean heat content and 300 m (HC300 m) representing heat content up to thermocline depth are first compared with heat contents computed from observations of two buoys in the TIO. It is found that there is good agreement between the model and observations. Fourier analysis of heat content is carried out in different regions of TIO. The amplitudes of semi-annual variability for HC50 m and HC300 m are observed to be greater than those for the annual variability in the Bay of Bengal, while in the Arabian Sea there is a mixed result. Heat content tendency is known to be governed by net surface heat flux and horizontal as well as vertical heat transports. For understanding the relative importance of these processes, a detailed analysis of these terms in the tendency equation is carried out. Rossby wave is observed in the annual mode of heat transport while equatorial jet and Kelvin waves are observed in the semi-annual mode of heart transport. Finally, the correlation between heat content and sea surface temperature (SST) and sea level anomaly (SLA), taken one at a time, is computed. It is found that the correlation improves significantly when both these quantities are together taken into account.     

Effects of site–city interaction and polarization of the incident S-wave on the transfer function and fundamental frequency of structures

Natural Hazards - The variation of 2D fundamental frequency of stand-alone structure on rock $$ ({F}_{{02{\text{D}}}}^{\text{S}} ) $$ and in a basin $$ ({F}_{{02{\text{D}}}}^{\text{BS}} ) $$ with...     

Interaction of coeval felsic and mafic magmas from the Kanker granite,Pithora region,Bastar Craton,Central India

Field and petrographic studies are carried out to characterize the interactions of mafic and felsic magmas from Pithora region of the northeastern part of the Bastar Craton. The MMEs, syn-plutonic mafic dykes, cuspate contacts, magmatic flow textures, mingling and hybridization suggest the coeval emplacement of end member magmas. Petrographic evidences such as disequilibrium assemblages, resorption textures, quartz ocelli, rapakivi and poikilitic textures suggest magma mingling and mixing phenomena. Such features of mingling and mixing of the felsic and mafic magma manifest the magma chamber processes. Introduction of mafic magmas into the felsic magmas before initiation of crystallization of the latter, results in hybrid magmas under the influence of thermal and chemical exchange. The mechanical exchange occurs between the coexisting magmas due to viscosity contrast, if the mafic magma enters slightly later into the magma chamber, then the felsic magma starts to crystallize. Blobs of mafic magma form as MMEs in the felsic magma and they scatter throughout the pluton due to convection. At a later stage, if mafic magma enters the system after partial crystallization of felsic phase, mechanical interaction between the magmas leads to the formation of fragmented dyke or syn-plutonic mafic dyke. All these features are well-documented in the study area. Field and petrographic evidences suggest that the textural variations from Pithora region of Bastar Craton are the outcome of magma mingling, mixing and hybridization processes.     

Using SPIRAL (Single Pollen Isotope Ratio AnaLysis) to estimate C3- and C4-grass abundance in the paleorecord

C₃ and C₄ grasses differ greatly in their responses to environmental controls and influences on biogeochemical processes (e.g. water, carbon, and nutrient cycling). Difficulties in distinguishing between these two functional groups of grasses have hindered paleoecological studies of grass-dominated ecosystems. Stable carbon isotopic analysis of individual grains of grass pollen using a spooling-wire microcombustion device interfaced with an isotope-ratio mass spectrometer holds promise for improving C₃ and C₄ grass reconstructions. This technique, SPIRAL (Single Pollen Isotope Ratio AnaLysis), has only been evaluated using pollen of known C₃ and C₄ grasses. To test the ability of SPIRAL to reproduce the abundance of C₃ and C₄ grasses on the landscape, we measured δ¹³C values of > 1500 individual grains of grass pollen isolated from the surface sediments of ten lakes in areas that span a large gradient of C₃- and C₄-grass abundance, as determined from vegetation surveys. Results indicate a strong positive correlation between the δ¹³C-based estimates of % C₄-grass pollen and the abundance of C₄ grasses on the landscape. The % C₄-grass pollen slightly underestimates the actual abundance of C₄ grasses at sites with high proportions of C₄ grasses, which can be corrected using regression analysis. Comparison of the % C₄-grass pollen with C/N and δ¹³C measurements of bulk organic matter illustrates the distinct advantages of grass-pollen δ¹³C as a proxy for distinguishing C₃ and C₄ shifts within the grass family. Thus SPIRAL promises to advance our understanding of grassland ecology and evolution.     

Stabilization of a Clayey Soil with Fly Ash and Lime: A Micro Level Investigation

Pavement structures on poor soil sub grades show early distresses causing the premature failure of the pavement. Clayey soils usually have the potential to demonstrate undesirable engineering behavior, such as low bearing capacity, high shrinkage and swell characteristics and high moisture susceptibility. Stabilization of these soils is a usual practice for improving the strength. This study reports the improvement in the strength of a locally available cohesive soil by addition of both fly ash and lime. Analysis using X-ray diffraction, scanning electron microscopy, coupled with energy dispersive spectroscopy, thermal gravimetric analysis, zeta potential and pH value test was carried out in order to elucidate the stabilization mechanism. The micro level analysis confirmed the breaking of montmorrillonite structure present in the untreated clay after stabilization. In the analysis, it was also confirmed that in the stabilization process, pozzolanic reaction dominated over the cation exchange capacity.     

Horizon-free gravitational collapse of radiating fluid sphere

In this paper we present a detailed study of BCT Ist solution Tewari (Astrophys. Space Sci. 149:233, 1988) representing time dependent balls of perfect fluid with matter-radiation in general relativity. Assuming the life time of quasar 10⁷ years our model has initial mass≈10⁸ M _Θ with an initial linear dimension≈10¹⁵ cm. Our model is radiating the energy at a constant rate i.e. L _∞=10⁴⁷ ergs/sec with the gravitational red shift, z=0.44637. In this model we have 2GM(u)/c ² R _S (u))=0.3191 i.e. the model is horizon free.     

New class of Well behaved exact solutions of relativistic charged <Emphasis Type="Italic">white-dwarf</Emphasis> star with perfect fluid

The paper presents a class of interior solutions of Einstein-Maxwell field equations of general relativity for a static, spherically symmetric distribution of the charged fluid. This class of solutions describes well behaved charged fluid balls. The class of solutions gives us wide range of parameter K (0.3277≤K≤0.49), for which the solution is well behaved hence, suitable for modeling of super dense star. For this solution the mass of a star is maximized with all degree of suitability and by assuming the surface density ρ _b =2×10¹⁴ g/cm³. Corresponding to K=0.3277 with X=−0.15, the maximum mass of the star comes out to be M=0.92M _Θ with radius r _b ≈17.15 km and the surface red shift Z _b ≈0.087187. It has been observed that under well behaved conditions this class of solutions gives us the mass of super dense object within the range of white-dwarf.