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151.
Swarniv Chandra Sailendra Nath Paul Basudev Ghosh 《Astrophysics and Space Science》2013,343(1):213-219
Using the Quantum hydrodynamic (QHD) model Korteweg-de Vries (KdV) type solitary excitations of electron-acoustic waves (EAWs) have been examined in a two-electron-populated relativistically degenerate super dense plasma. It is shown that relativistic degeneracy parameter significantly influences the conditions of formation and properties of solitary structures. 相似文献
152.
N. Chandra Wickramasinghe 《Astrophysics and Space Science》2013,343(1):1-5
The theory of cometary panspermia, developed by the late Sir Fred Hoyle and the present author argues that life originated cosmically as a unique event in one of a great multitude of comets or planetary bodies in the Universe. Life on Earth did not originate here but was introduced by impacting comets, and its further evolution was driven by the subsequent acquisition of cosmically derived genes. Explicit predictions of this theory published in 1979–1981, stating how the acquisition of new genes drives evolution, are compared with recent developments in relation to horizontal gene transfer, and the role of retroviruses in evolution. Precisely-stated predictions of the theory of cometary panspermia are shown to have been verified. 相似文献
153.
N. Chandra Wickramasinghe Jamie Wallis Daryl H. Wallis Rudolph E. Schild Carl H. Gibson 《Astrophysics and Space Science》2012,341(2):295-299
The space density of life-bearing primordial planets in the solar vicinity may amount to ~8.1×104?pc?3 giving total of ~1014 throughout the entire galactic disk. Initially dominated by H2 these planets are stripped of their hydrogen mantles when the ambient radiation temperature exceeds 3?K as they fall from the galactic halo to the mid-plane of the galaxy. The zodiacal cloud in our solar system encounters a primordial planet once every 26 My (on our estimate) thus intercepting an average mass of 103 tonnes of interplanetary dust on each occasion. If the dust included microbial material that originated on Earth and was scattered via impacts or cometary sublimation into the zodiacal cloud, this process offers a way by which evolved genes from Earth life could become dispersed through the galaxy. 相似文献
154.
This study provides an assessment of changes in the terrain topography due to opencast coal mining in the Patratu region of Jharkhand state during the period of 1962–2007. It demonstrated the potential of digital elevation model (DEM) differencing technique using Cartosat-I satellite (2007) derived DEM with reference to DEM derived from contours obtained from Survey of India topographical map (1962). The topographical changes through DEM differencing revealed positive relief changes (up to 49 m) due to coal-mining overburden dumps. The dumping of overburden near the banks of perennial Damodar River also caused positive topographic changes (up to 20 m) indicating adverse effects on its hydrological regime. Negative relief changes are represents by deep depressions (up to 66 m) created within coal mines due to the extraction of coal. These depression areas within the abundant mines generally become the zones of water accumulation causing wastage of surface and ground water resources. 相似文献
155.
Anthropogenic arsenic menace in Delhi Yamuna Flood Plains 总被引:2,自引:1,他引:1
Chandra S. Dubey Bhupendra K. Mishra Dericks P. Shukla Ravindra P. Singh M. Tajbakhsh Purushottam Sakhare 《Environmental Earth Sciences》2012,65(1):131-139
Arsenic, one of the most poisonous chemical elements, was analyzed in the waters of the host of the 2010 Commonwealth Games,
i.e., New Delhi. The study revealed shocking outcomes with arsenic concentrations well beyond the safe limits set by WHO,
and a maximum concentration up to 180 ppb was found in the groundwater. Analysis of around 120 water samples collected extensively
along the Yamuna Flood Plain showed that more than 55% had arsenic contamination beyond the WHO limit of 10 ppb. The maximum
value of arsenic in coal and fly ash from Rajghat coal-based thermal power plant contained 200 and 3,200 ppb, respectively.
Moreover, the ore petrography of coal samples shows the presence of arsenopyrite mineral. Maximum concentration of arsenic
contamination is found within a 5-km radius from power plants. In the perspective of Delhi, arsenic contamination is purely
anthropogenic due to coal-based thermal power plants, which had already shown toxic arsenic, fluorine and China-type coal
effects. The presence of such power plants in coal field locations, e.g., West Bengal and Bangladesh, could release the arsenic
due to combustion in superthermal power plants, thus accentuating the arsenic concentration besides the natural arsenic coming
from the foreland basins of the Himalaya in Indian sub-continent. 相似文献
156.
The quantitative relationships between lithological variables of Early Permian Barakar coal measures of western Singrauli Gondwana sub-basin are investigated using principal component analysis in an attempt to reveal simple relationships undetected by conventional quantitative methods. The results not only confirm and amplify those of the simple regression analysis described in Casshyap et.al. (1988), but are also interpreted in terms of evolution of coal swamps. If the total thickness of strata, total thickness of clastic sediments, total thickness of coal seams, number of sandstone beds, number of shale beds, number of coal seams and clastic ratio are considered, the first three components accounts for 80% of the total variance and the lithological variables generally fall into two groups. One group contains the first four variables, namely, total thickness of strata, total thickness of sandstone, total thickness of shale and total thickness of coal seams, all of which have basin-like regional patterns of sedimentation linked to net subsidence. The other group of variables, which are somewhat less closely related to net subsidence such as number of sandstone beds, number of shale beds and number of coal seam. The sand/shale ratio and clastic ratio are dependent on the other variables and seem to be unrelated to net subsidence. The principal component results, at best in geological term, may be explained by the to and fro lateral migration of a river channel across its flood plain coupled with a gradual isostatic adjustment of the basin floor in response to the weight of the sediments and differential subsidence through space and time. 相似文献
157.
AbstractThe Shyok suture zone separates the Ladakh terrane to the SW from the Karakoram terrane to the NE. Six tectonic units have been distinguished. From south to north these are; 1. Saltoro formation; 2. Shyok volcanites; 3. Saltoro molasse; 4. Ophiolitic melange; 5. Tirit granitoids; 6. Karakoram terrane including the Karakoram batholith. Albian—Aptian Orbitolina-bearing lime-stones and turbidites of the Saltoro formation tectonically overlie high-Mg-tholeiites similar to the tectonically overlying Shyok volcanites. The high-Mg tholeiitic basalts and calcalkaline andesites of the Shyok volcanites show an active margin signature. The Saltoro molasse is an apron-like, moderately folded association of redgreen shales and sandstones that are interbedded with ~ 50 m porphyritic andesite. Desiccation cracks and rain-drop imprints indicate deposition in a subaerial fluvial environment. Rudist fragments from a polygenic conglomerate of the Saltoro molasse document a post-Middle Cretaceous age. The calcalkaline andesites of the Shyok volcanites are intruded by the Tirit granitoids, which are located immediately south of the Ophiolitic melange and belong to a weakly deformed trondhjemite-tonalite-granodiorite-granite suite. These granitoids are subalkaline, I-type and were emplaced in a volcanic arc setting. The subalkaline to calcalkaline granitoids of the Karakoram batholith are I-and S-type granitoid. The I-type granitoids represent a typical calcalkaline magmatism of a subduction zone environment whereas the S-type granitoids are crustderived, anatectic peraluminous granites. New data suggest that the volcano-plutonic and sedimentary successions of the Shyok suture zone exposed in northern Ladakh are equivalent to the successions exposed along the Northern suture in Kohistan. It is likely that the o istan and Ladakh blocks evolved as one single tectonic domain uring the Cretaceous-Palaeogene. Subsequently, collision, suturing and accretion of the Indian plate along the Indus suture (50–60 Ma) together with tectonic activity along the Nanga Parbataramosh divided Kohistan and Ladakh into two arealy distinct magmatic arc terranes. The activity and a dextral offset along the Karakoram fault (Holocene-Recent) disrupted the original tectonic relationships. © 1999 Éditions scientifiques et médicales Elsevier SAS 相似文献
158.
159.
Blesson Mathew Annapurni Subramaniam Bhuwan Chandra Bhatt 《Monthly notices of the Royal Astronomical Society》2008,388(4):1879-1888
Emission-line stars in young open clusters are identified to study their properties, as a function of age, spectral type and evolutionary state. 207 open star clusters were observed using the slitless spectroscopy method and 157 emission stars were identified in 42 clusters. We have found 54 new emission-line stars in 24 open clusters, out of which 19 clusters are found to house emission stars for the first time. About 20 per cent clusters harbour emission stars. The fraction of clusters housing emission stars is maximum in both the 0–10 and 20–30 Myr age bin (∼40 per cent each). Most of the emission stars in our survey belong to Classical Be class (∼92 per cent) while a few are Herbig Be stars (∼6 per cent) and Herbig Ae stars (∼2 per cent). The youngest clusters to have Classical Be stars are IC 1590, NGC 637 and 1624 (all 4 Myr old) while NGC 6756 (125–150 Myr) is the oldest cluster to have Classical Be stars. The Classical Be stars are located all along the main sequence (MS) in the optical colour–magnitude diagrams (CMDs) of clusters of all ages, which indicates that the Be phenomenon is unlikely due to core contraction near the turn-off. The distribution of Classical Be stars as a function of spectral type shows peaks at B1–B2 and B6–B7 spectral types. The Be star fraction [N(Be)/N(B+Be)] is found to be less than 10 per cent for most of the clusters and NGC 2345 is found to have the largest fraction (∼26 per cent). Our results indicate there could be two mechanisms responsible for the Classical Be phenomenon. Some are born Classical Be stars (fast rotators), as indicated by their presence in clusters younger than 10 Myr. Some stars evolve to Classical Be stars, within the MS lifetime, as indicated by the enhancement in the fraction of clusters with Classical Be stars in the 20–30 Myr age bin. 相似文献
160.
Arvind Chandra Pandey Swagata Ghosh M. S. Nathawat Reet Kamal Tiwari 《Journal of the Indian Society of Remote Sensing》2012,40(2):245-255
Accurate representations of the Earth’s surface in the form of digital elevation models (DEMs) are essential for a variety
of applications in glaciological and remote-sensing research. In the present study area change and thickness variation over
Pensilungpa glacier was attempted using remote sensing approach. It can be remarked that a net loss of 9.23 sq. km. which
is 38% of the glacier area mapped in 1962 indicate a drastic change over the glacier area during 1962–2007. Estimation of
glacier thickness change on Pensilungpa glacier based on ASTER DEM (2003) and Survey of India (SOI) contour based DEM (1962)
indicated increase in the glacier elevation in the accumulation zone mainly by 30 to 90 m and similar reduction by 30 to 90 m
in the ablation zone. 相似文献