Diffuse X-ray background measurements in the energy range 2–18 keV     

A. S. Prakasarao  D. P. Sharma  U. B. Jayanthi  U. R. Rao 《Astrophysics and Space Science》1971,10(1):150-155

Rocket measurements, of the diffuse X-ray background in the energy range 2–18 keV, conducted from Thumba Equatorial Rocket Launching Station (TERLS), India, are presented. The estimates of the cosmic background are derived by the method which employs the Earth and its atmosphere as a shutter to intercept the celestial X-rays. The results are shown to be consistent with a power law photon spectrum.13.6 _–3.3 ^+4.3 E ^{–1.73±0.15} photons/cm²-sec-keV-ster the spectrum being much flatter than that observed at higher energies.  相似文献   

Major Element, REE, and Other Trace Element Behavior in Amphibolite Weathering under Semiarid Conditions in Southern India     

Sharma A  Rajamani V 《The Journal of geology》2000,108(4):487-496

A body of komatiitic amphibolite, an enclave within the Archean high-grade orthogneisses in southern India, shows mild chemical weathering under semiarid conditions. Along fractures, chemical weathering has advanced (Chemical Index of Alteration &sqbl0;CIA&sqbr0;=53; CIA of fresh rock approximately 26) to the extent that secondary Mg-Fe-Al clay minerals have formed and the rock has turned brownish red, soft, and fine grained. The weathering process has resulted in the mobilization and redistribution of the so-called immobile elements Fe, Al, Ti, and REE effected by the nature of secondary mineral formation (talc vs. aluminous clay minerals) and also possibly by soil microbes. In the initial stages of secondary mineral formation, there is a small loss of Fe, Al, and REE (noticeably Eu). However, in the fracture zone as well as in the incipiently altered zone, there is significant REE enrichment, probably affected by a different precipitation mechanism. Mobilized REE may have come from a minor alteration of clinopyroxene.  相似文献   

Mapping of fault rupture of the 28 may 2004 iran earthquake (mw= 6.2) using satellite image     

M. Sharifikia  C. S. Dubey  B. K. Sharma  M. Chaudhry  P. K. Champati Ray 《Journal of the Indian Society of Remote Sensing》2006,34(4):423-430

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The behavior of natural and anthropogenic osmium in the Hudson River-Long Island Sound estuarine system     

Karl K. Turekian  Mukul Sharma 《Geochimica et cosmochimica acta》2007,71(17):4135-4140

The extent to which riverine Os is trapped in a temperate estuary was the aim of this study. The behavior of Os through the Hudson River, East River and the Long Island Sound (LIS) system is addressed using both natural Os and anthropogenically mobilized Os. The Os concentration ([Os]) and isotopic composition (¹⁸⁷Os/¹⁸⁸Os) of the Mid-Atlantic Bight as inferred from the analysis of a water sample of 31‰ salinity (S) at Vineyard Sound, MA are 46 fM and 1.070, respectively. In comparison, the Hudson River at Newburgh, NY has [Os] = 68 fM and ¹⁸⁷Os/¹⁸⁸Os = 1.265. The Os concentration of the East River at the Whitestone Bridge is 51 fM and remains essentially constant proceeding eastward in the LIS despite the increase of salinity from 20‰ towards the higher value of the Mid-Atlantic Bight. The ¹⁸⁷Os/¹⁸⁸Os ratio of water at Whitestone Bridge is 0.945 and increases eastward through the Sound to 0.979 at 7 km and then to 1.019 at 39.6 km. The behavior of Os through LIS appears to be conservative at S > 20‰. On the basis of Os concentration and isotopic composition we infer that anthropogenic Os is being added to the East River through sewers with the likely isotopic ratio of ∼0.13 and that about 24% of riverine Os must be removed at S ? 20‰. There is a net transport of about 0.4-1 mole of anthropogenic Os per year from the East River into the LIS. The residence time of Os in the ocean at present must be about 39,000 years, unless an independent source of supply of Os can be identified.  相似文献   

The shift of ravi river and the geomorphological features along its course in amritsar and gurdaspur districts of punjab     

Abraham Thomas  PK Sharma 《Journal of the Indian Society of Remote Sensing》1998,26(1-2):57-68

Satellite remote sensing technique can be effectively utilised in mapping and monitoring the river course changes and associated geomorphological features. Ravi river, flowing along the Indo-Pakistan border, has been in the limelight for its repeated flood havoc during monsoon and abrupt encroachment at some places in the Indian territory, where it was not flowing earlier. This river, meandering in zig-zag fashion along the International boundary in Amritsar and Gurdaspur districts of Punjab, poses perennial threats to the nations’s economy due to extensive destruction happening every year. An attempt has been made to map the shift of this river and the associated geomorphological features along its course using the Indian Remote Sensing Satellite data (IRS-IA and IB LISS-IIFCC) of the period 1991–1993 and the Survey of India topographic sheets of the period 1972–1973. The study shows that there has been drastic changes in the course of Ravi during a span of 20 years due to human activities along its course. The river has shifted its course considerably towards India since its topography is against it. River training structures/bundhs, built by the neighbouring country, across and very near to the earlier river course has been the main reason for this drastic shifting. It is estimated that such massive structures could turn the river course towards India by atleast 1 to 5 km in the border districts of Punjab. This shifting of Ravi along international border poses a serious threat to the Nation’s defence system.  相似文献   

Geologic and tectonic evolution of the Himalaya before and after the India-Asia collision     

Kewal K. Sharma 《Journal of Earth System Science》1998,107(4):265-282

The geology and tectonics of the Himalaya has been reviewed in the light of new data and recent studies by the author. The data suggest that the Lesser Himalayan Gneissic Basement (LHGB) represents the northern extension of the Bundelkhand craton, Northern Indian shield and the large scale granite magmatism in the LHGB towards the end of the Palæoproterozoic Wangtu Orogeny, stabilized the early crust in this region between 2-1.9 Ga. The region witnessed rapid uplift and development of the Lesser Himalayan rift basin, wherein the cyclic sedimentation continued during the Palæoproterozoic and Mesoproterozoic. The Tethys basin with the Vaikrita rocks at its base is suggested to have developed as a younger rift basin (～ 900 Ma ago) to the north of the Lesser Himalayan basin, floored by the LHGB. The southward shifting of the Lesser Himalayan basin marked by the deposition of Jaunsar-Simla and Blaini-Krol-Tal cycles in a confined basin, the changes in the sedimentation pattern in the Tethys basin during late Precambrian-Cambrian, deformation and the large scale granite activity (～ 500 ± 50 Ma), suggests a strong possibility of late Precambrian-Cambrian Kinnar Kailas Orogeny in the Himalaya. From the records of the oceanic crust of the Neo-Tethys basin, subduction, arc growth and collision, well documented from the Indus-Tsangpo suture zone north of the Tethys basin, it is evident that the Himalayan region has been growing gradually since Proterozoic, with a northward shift of the depocentre induced by N-S directed alternating compression and extension. During the Himalayan collision scenario, the 10–12km thick unconsolidated sedimentary pile of the Tethys basin (TSS), trapped between the subducting continental crust of the Indian plate and the southward thrusting of the oceanic crust of the Neo-Tethys and the arc components of the Indus-Tangpo collision zone, got considerably thickened through large scale folding and intra-formational thrusting, and moved southward as the Kashmir Thrust Sheet along the Panjal Thrust. This brought about early phase (M1) Barrovian type metamorphism of underlying Vaikrita rocks. With the continued northward push of the Indian Plate, the Vaikrita rocks suffered maximum compression, deformation and remobilization, and exhumed rapidly as the Higher Himalayan Crystallines (HHC) during Oligo-Miocene, inducing gravity gliding of its Tethyan sedimentary cover. Further, it is the continental crust of the LHGB that is suggested to have underthrust the Himalaya and southern Tibet, its cover rocks stacked as thrust slices formed the Himalayan mountain and its decollement surface reflected as the Main Himalayan Thrust (MHT), in the INDEPTH profile.  相似文献   

An analytical source function for a coupled hybrid wave model     

M. Mohan  Abhijit Sarkar  Raj Kumar 《Journal of Earth System Science》1998,107(3):213-216

An analytical form for the source function is formulated by comparing the fetch-limited approximation of the Ocean Wave Transport equation and the empirical equation for the fetch-dependent wave forecast nomograms. The source function thus generated has been utilised in the numerical model based on Toba’s formulation of wave transport equation and tested for the seas around the Indian subcontinent (5°S to 25°N latitude; 45°E to 100°E longitude). The grid averaged hindcast wave heights are found to be moderately matching with the GEOSAT altimeter measured significant wave heights of the 1987–1989 period, particularly for waves higher than 1 meter.  相似文献   

Magnetized Stiff Fluid Tilted Universe for Perfect Fluid Distribution in General Relativity     

Raj Bali  B.L. Meena 《Astrophysics and Space Science》1998,262(1):89-96

We have investigated magnetized stiff fluid Bianchi Type I anisotropic tilted cosmological model for perfect fluid distribution in General Relativity. It has been assumed that the expansion in the model is only in two directions i.e. one of the Hubble parameter (H₁ = A₄/A); is zero. It has been shown that tilted nature of the model is preserved due to magnetic field. The various physical and geometrical aspects of the model is also discussed.  相似文献   

Incursion of the Pacific Ocean Water into the Indian Ocean     

G S Sharma  A D Gouveia  Shubha Satyendranath 《Journal of Earth System Science》1978,87(3):29-45

Using the data collected during the International Indian Ocean Expedition, maps showing the distribution of depth, acceleration potential, salinity and oxyty were prepared for the northeast monsoon for the four potential thermosteric anomaly surfaces: 160, 120, 80 and 60 cl/t. Zonal components of current along 84°E were computed from the geopotential dynamic heights. From such an analysis, it became clear that low-salinity water from the Pacific intrudes into the western Indian Ocean through the Banda and Timor seas in the upper layers above 100 cl/t surface, while the North Indian Ocean Water penetrates towards the Eastern Archipelago below 100 cl/t surface. The South Equatorial Countercurrent and the Tropical Countercurrent are well depicted on the vertical section of zonal components as well as on the distribution of acceleration potential.  相似文献   

Origin of the pyrophyllite-diaspore deposits of the Bundelkhand Complex,Central India   总被引：1，自引：0，他引：1  

R. P. Sharma 《Mineralium Deposita》1979,14(3):343-352

Twenty three samples from the pyrophyllite-diaspore deposits have been investigated by x-ray diffraction and geochemical methods. The mineral assemblages belong to the K₂O-Al₂O₃-SiO₂-H₂O system. Higher concentrations of Ti, Cr and Zr in the deposits as compared with the associated granites and gneisses suggest their laterite type parentage. Existing mineral assemblages are a result of low grade metamorphism (up to about 350°C) of the primary residual deposits containing a kaolinite - diaspore - quartz assemblage.  相似文献