Qualitative stability assessment of cut slopes along the National Highway-05 around Jhakri area,Himachal Pradesh,India

Several deformation phases in tectonically active Himalayas have rendered the rock masses very complex in terms of structure, lithology and degree of metamorphism. Again, anthropogenic activities such as roads, tunnels and other civil engineering constructions have led to a state of disequilibrium which in many cases, results in failure of rock masses. National Highway-05 around Jhakri area in India is a major connecting route to the China border in the hilly terrains of the state Himachal Pradesh. It cuts through the Himalayan rocks and has a hazardous history of landslides destroying human lives and interrupting communication very frequently. As a contribution towards the mitigation process, a study has been carried out along the highway to analyse kinematic stability and qualitative estimation of rock mass condition through rock mass classification systems. The kinematic analysis shows that the rock slopes are prone to planar and wedge failure. Rock mass rating for most of the locations lies between 7 and 34, representing a poor rock mass quality (Class IV), whereas slope mass rating is more disperse and ranges from 11 to 52 for most of the slopes (Class III, IV and V).     

Transient heating of the upper atmosphere by auroral electric field

Magnetohydrodynamic formulation has been used to deduce the velocity distribution of the upper atmospheric movement caused by the auroral electric field at the thermospheric height. The expressions for Joule heating and viscous heating are obtained. Numerical analysis has been made to estimate their magnitudes as well as the rate of their variations with time. The results are presented graphically.     

The appropriate dyadic applicable to the lower region of the ionospheric plasma

An expression for the susceptibility dyadic appropriate to the lower regions of the atmospheric plasma is derived using Maxwell's field equations and the equation of conservation of momentum. The contributions due to viscous effect and convection current density are incorporated in the physical processes within the stated medium. Utilizing the approximation of linearized equations, second order coupled wave equations have been derived through the dyadic.     

Spectrum of average flux of the S-component of solar radio emission

Spectrum of average flux of the S-component of solar radio emission observed during the peak phase of the present solar cycle has been determined statistically. Daily values of the mean solar flux at 606, 1415, 2695, 4995 and 8800 MHz observed at the Sagamore Hill Solar Radio Observatory have been examined. The superposed epoch method (Chree analysis) has been used for determining the true nature of the S-component at all these frequencies. Spectrum has been obtained after elimination of the basic components at the respective frequencies. The important results obtained from the present statistical investigation are: (1) the basic component increases with frequency, (2) the S-component shows a maximum at 4995 MHz (6 cm), (3) the spectrum is independent of the phase of the 27-day cycle and (4) S-components at all the frequencies have slopes which are both more uniform and higher in the ascending phase than those in the descending phase of the 27-day cycle. In the descending phase slopes increase with frequency.     

Growth rate and life span of Eocene/Oligocene Nummulites tests: inferences from Sr/Ca ratio

The problem of growth rate and life span of Nummulites foraminifers, attaining giant sizes during the Eocene, has been addressed by analysing their Sr/Ca ratio across the Eocene/Oligocene Boundary (EOB) of Kutch, western India. The Eocene ratio (˜ 1) rapidly decreases during the Oligocene (˜ 0.5) and is coincident with the extinction of most of the Eocene Nummulites species, a rapid enrichment of δ¹⁸O and decrease in both test size and species diversity across the boundary. The high Sr/Ca ratio in Eocene foraminifers can be explained by their rapid growth under a favourable climatic condition. The climatic deterioration (e.g. δ¹⁸O cooling) across the boundary and during the early Oligocene possibly forced the Nummulites to adopt a slower growth rate (and stunted growth). The rapid growth of the Eocene Nummulites indicates that the giant sizes of these protists need not necessarily involve a large life span.     

Non-linear r.f. heating of ionospheric plasma

The non-linear heating of electrons in the ionospheric plasma due to high-power radio wave propagation has been investigated through an integro-differential equation derived from Boltzmann velocity-moment equations. Various processes appropriate to the situation under study are taken into account. The numerical solution of the derived equation is presented graphically.Department of Applied Mathematics, University of Calcutta, India.     

Primary depositional and diagenetic features in the banded iron formation and associated iron-ore deposits of Noamundi,Singhbhum district,Bihar, India

The Banded Hematite Jasper (BHJ) Formation of Noamundi region in Bihar, belonging to the lower part of the Iron Ore Group of early Precambrian age (c. 2900–3200 Ma), exhibits numerous primary depositional and diagenetic features, both in BHJ as well as the associated iron ore deposits. Observed primary depositional features include banding and bedding of different geometric-types, surface-markings including interference ripple-marks, current crescents, linear markings, scour-and-fill structures, etc. and within-mass microstructures such as spherulites, granules, discs and maculose cylindrical bodies. Diagenetic features, such as fabric changes, micro-dessication structures, gravity-density features, etc. and motion-and-disruption features of various kinds are also seen. The significance of various features in terms of probable mode and environments of deposition of BHJ and the iron ore beds has been considered. In general, shallow water environment of deposition in a region proximal to the shoreline with a rather steep paleoslope of the shelf has been surmised.     

Tectonic Significance of Fissure Veins Associated with Pseudotachylites of the Kui-Chitraseni Shear Zone, Aravalli Mountain, NW India

Kui-Chitraseni Shear Zone of the Precambrian Aravalli Mountain, NW India is marked by a nearly 400 m-wide NE-SW trending belt of cataclasites developed on the granites and metasediments of the Delhi Supergroup. The cataclasites are criss crossed by pseudotachylite and fissure-veins. While the pseudotachylites are aphanitic to microlitic, the fissure veins are characterized by syntaxial-bitaxial as well as unitaxial growth of elongate quartz grains. Textural study of the fissure veins suggests crystallization of quartz grains in a dilational environment in hydrous condition. Contrarily the pseudotachylites bear the evidence of frictional melting of rocks under anhydrous conditions. Since in many instances it is observed that the fissure veins have replaced the pseudotachylites following the crack seal mechanism, the formation of fissure veins is considered to be latekinematic to pseudotachylites. Hence it is interpreted that the pseudotachylites and fissure veins were formed in two distinct tectonic events. While pseudotachylites were formed in a compressional setting resulted from thrusting along the shear zone, the fissure veins have been formed in an extensional setting during a late stage normal faulting. In light of this tectonic rejuvenation along the Kui-Chitraseni Shear Zone, various lineaments present within the Aravalli Mountains need further study for understanding the evolution of the region.     

Rapid assessment of cyclone damage using NPP-VIIRS DNB and ancillary data

Natural Hazards - Rapid damage assessment of natural disasters is essential for the fast recovery and strategic post-disaster reconstructions. In the present study, National Polar-Orbiting...