Bearing of plate geometry and rheology on shallow-focus mega-thrust seismicity with special reference to 26 December 2004 Sumatra event

We propose a model pertaining to the generation of 26th December 2004 off Sumatra mega-event in the backdrop of other similar type earthquakes along subduction zones around the world. Reconstructions of Benioff trajectories through the hypocenters of historical earthquakes including six mega-earthquakes indicate (i) confinement of hypocenters right within the descending lithosphere, and (ii) natural coincidence of foci of the mega-events around the zones of plate flexing. These observations are discussed in detail with special emphasis on the Sumatra margin considering the role of rheological anomaly across the cross-section of the descending lithosphere; yield strength envelope and residual stress accumulation through time. The intraplate origin of shallow mega-thrust earthquakes allowed us to advocate the ‘zone of flexing’ along the profiles of the subducting plates as nodal area for stress concentration. We propose here that at elevated confining pressure and temperature, loading of unidirectional cyclic stress on time-average bending stress enhanced the material yield strength (i.e., strain-hardening), and leads the semi-brittle portion of the lithosphere into near-brittle condition through rheological transformation. Under subsequent rise in neutral surface and increase in compressive stress field, non-coaxial deformation triggered shear failure on 26th December 2004 preferably at the rheological interface between strain-hardened near-brittle layer and deformed ductile layer within the sub-oceanic mantle.A two-stage fracture mechanism viz. a slow (～1.1 km/s) bilateral initiation in an essentially strain-hardened near-brittle domain and a follow-up very rapid progression (3.3 km/s) in the brittle, crustal domain was mainly involved in the generation of 2004 off Sumatra mega-event. Estimation shows an amount of 3.38 × 10²² to 4.50 × 10²² N m seismic moment (M_o) and 8.95–9.03 moment magnitude (M_w) for the southern part of the 1300 km extended rupture i.e. between the North Andaman to the north and the Sumatra at its south. The study necessitates the reassessment of other shallow-focus mega-thrust earthquakes along the subduction margins around the globe.     

Revisiting the classical electron model in general relativity

Motivated by earlier studies (Tiwari et al. in Astrophys. Space Sci. 182:105, 1984; Herrera and Varela in Phys. Lett. 189:11, 1994), we model electron as a spherically symmetric charged perfect fluid distribution of matter. The existing model is extended assuming a matter source that is characterized by quadratic equation of state in the context of general theory of relativity. For the suitable choices of the parameters, our charged fluid models almost satisfy the physical properties of electron.     

Study on sheath formation in astroplasmas under Coriolis force and behavior of levitated dust grains forming nebulon around Moon

Pseudopotential analysis has been employed to derive a modified Sagdeev potential-like wave equation for studying the sheath formation in astroplasma problems. Complexity in process urges to derive the new findings numerically by using fourth-order Runge-Kutta method. Main emphasis has been given to investigate the role of Coriolis force on the formation and changes on coherent structures of sheath suitably thought for the configuration of astroplasma. Study determines the sheath thickness and potential variation with the interaction of Coriolis force and thereby finds dynamical behavior of levitated dust grains into the evaluated sheath region. This leads to find the dust size, and corresponding forces generated on dust grain with a view to relate theoretical observations to real astrophysical phenomena and could be of interest to explain formation of dust clouds in spaces. To support the observations, we some thoughtful numeric plasma parameters for the case of Earth’s Moon, have taken for graphical presentations. Overall observations expect the study could be of interest as an advanced knowledge in rotating astroplasmas, and expecting many salient features which are yet to be known.     

Some general relativistic effects on the dynamics of fluid disks rotating around a Schwarzschild black hole

In this paper we present various classes of solutions for perfect fluid disks rotating around Schwarzschild black holes. We study the profiles of pressure, density and specific angular momentum and the formation of cusp-like structures at the inner edge of the disks. Using the trial function method, we calculate the frequency of the global axi-symmetric oscillations. We compare the results with those of the corresponding Newtonian calculations to find the general relativistic effects.     

Environmental Health Injustice: Exposure to Air Toxics and Children's Respiratory Hospital Admissions in El Paso,Texas

Although much environmental justice research tacitly assumes that unequal environmental exposures produce geographic disparities in adverse health outcomes, very few empirical environmental justice studies have tested that assumption. This article does so by using estimates of exposure to air toxics disaggregated by emission source (point and mobile) to predict children's hospitalization rates for both asthma and respiratory infections in El Paso, Texas. Air toxics emissions from most source categories were found to be significant predictors of children's respiratory infection hospitalization rates, but not asthma hospitalization rates, at the census tract level. Findings suggest that sociospatial disparities in respiratory infection rates might be linked to environmental inequalities.     

On role of pressure anisotropy for relativistic stars admitting conformal motion

We investigate the spacetime of anisotropic stars admitting conformal motion. The Einstein field equations are solved using different ansatz of the surface tension. In this investigation, we study two cases in details with the anisotropy as: (1) p _t =n p _r , (2) -p_r=(+c_2)p_{t}-p_{r}=\frac{1}{8\pi}(\frac{c_{1}}{r^{2}}+c_{2}) where, n, c ₁ and c ₂ are arbitrary constants. The solutions yield expressions of the physical quantities like pressure gradients and the mass.     

Copper and zinc uptake by rice and accumulation in soil amended with municipal solid waste compost

Effect of addition of municipal solid waste compost (MSWC) on two metals viz. copper (Cu) and zinc (Zn) contents of submerged rice paddies were studied. Experiments were conducted during the three consecutive wet seasons from 1997 to 1999 on rice grown under submergence, at the Experimental Farm of Calcutta University, India. A sequential extraction method was used to determine the metal (Cu and Zn) fractions in MSWC and cow dung manure (CDM). Both metals were significantly bound to the organic matter and Fe and Mn oxides in MSWC and CDM. Metal content in rice straw was higher than in rice grain. Metal bound with Fe and Mn oxides in MSWC and CDM best correlated with straw and grain metal followed by exchangeable and water soluble fractions. Carbonate, organic matter bound and residual fractions in MSWC and CDM did not significantly correlate with rice straw and grain metal. The MSWC would be a valuable resource for agriculture if it can be used safely, but long-term field experiments with MSWC are needed to assess by regular monitoring of the metal loads and accumulation in soil and plants.     

Numerical simulation of the North American monsoon system

Summary ¶This paper deals with the systematic evolution of the North American monsoon system by analyzing the evolution of tropospheric circulation, precipitation, moisture fluxes and the adjoining sea surface temperatures from observations and the Florida State University Nested Regional Spectral Model embedded within a coupled atmosphere–ocean coupled model. The atmospheric part is a global spectral model with triangular truncation T63 and a nested regional spectral model. The global atmospheric model is coupled with the Hamburgs Global Ocean Model. This model was integrated for six-months with 50km resolution in the North American monsoon domain. The NCEP/NCAR reanalysis were used as the observed state for comparison. The analyzed model results shows that the above model has the capability of capturing some of the features of the North American monsoon system. Besides the evolution of the monsoon system, the out-of-phase relationship between the Mexican monsoon with south-central United States precipitation and the largest moisture supply from the Gulf of Mexico are the principal findings of this study. It is also noted that during the mature phase of the monsoon, the Gulf of California and the Pacific Ocean dominates the Gulf of Mexico in order of moisture supply but immediately after the mature phase, the Gulf of Mexico dominates.Received January 18, 2002; accepted July 7, 2002 Published online: June 12, 2003     

Black holes in the Einstein–Gauss–Bonnet theory and the geometry of their thermodynamics—II

In the present work we study (i) the charged black hole in Einstein–Gauss–Bonnet (EGB) theory, known as the Einstein–Maxwell–Gauss–Bonnet (EMGB) black hole and (ii) the black hole in EGB gravity with a Yang–Mills field. The thermodynamic geometry of these two black hole solutions has been investigated, using the modified entropy in Gauss–Bonnet theory.     

Universe bounded by apparent horizon: an irreversible thermodynamic prescription

In this work, we study universe bounded by apparent horizon as an irreversible thermodynamical system. Using the non equilibrium thermodynamical technique, the modified entropy variation on the apparent horizon has been evaluated in general. Two dark energy models are presented and results are analyzed.