Particle motion in the field of a five-dimensional charged black hole     

Sarbari Guha  Pinaki Bhattacharya  Subenoy Chakraborty 《Astrophysics and Space Science》2012,341(2):445-455

In this paper, we have investigated the geodesics of neutral particles near a five-dimensional charged black hole using a comparative approach. The effective potential method is used to determine the location of the horizons and to study radial and circular trajectories. This also helps us to analyze the stability of radial and circular orbits. The radius of the innermost stable circular orbits have also been determined. Contrary to the case of massive particles for which, the circular orbits may have up to eight possible values of specific radius, we find that the photons will only have two distinct values for the specific radii of circular trajectories. Finally we have used the dynamical systems analysis to determine the critical points and the nature of the trajectories for the timelike and null geodesics.  相似文献   

Bloom of Hemidiscus hardmannianus (Bacillariophyceae) and Its Impact on Water Quality and Plankton Community Structure in a Mangrove Wetland     

Sejuti Naha Biswas  Nallamuthu Godhantaraman  Ranjit K. Sarangi  Bhaskar D. Bhattacharya  Santosh K. Sarkar  Kamala K. Satpathy 《洁净——土壤、空气、水》2013,41(4):333-339

An intense monospecies bloom of the centric diatom Hemidiscus hardmannianus (Greville) Mann. (Bacillariophyceae) occurred in the coastal waters of Sundarban mangrove wetland, India on 22 July, 2010. The species was abruptly flourished (mean density 8.86 × 10⁶ cells/L) resulting intense green coloration of water. The greatest impoverishment of diversity and density of phytoplankton, micro‐ and mesozooplankton community was observed during the bloom. The phytoplankton community showed an extreme reduction in diversity (12 species to one) and sharp decrease in standing stock (12.84 × 10³ to 8.86 × 10⁶ cells/L) during this period. The late bloom condition coincided with sudden and huge arrival of a clupoid fish Hilsa ilisha which forms the most potential fisheries in Sundarban deltaic region. An attempt has been made to correlate the satellite remote sensing‐derived information to the bloom conditions. The MODIS‐Aqua derived chlorophyll and TMI satellite derived sea surface temperature and wind speed maps have been interpreted.  相似文献   

Tectonostratigraphic and geochronologic reappraisal constraining the growth and evolution of Singhbhum Archaean craton, eastern India     

A. B. Roy  H. N. Bhattacharya 《Journal of the Geological Society of India》2012,80(4):455-469

Reappraisal of field relationships between the different lithological ensembles supported by available geochronological data, and taking due note of the tectono-metamorphic, magmatic and sedimentation history helped to build up a coherent crustal evolutionary history of the Singhbhum Archaean craton, eastern India. The evolution of the earliest sialic crust, as the isotope ages suggest, was around 3700 Ma or even earlier. Deposition of the oldest, dominantly metasedimentary supracrustals, the Older Metamorphic Group (OMG), was initiated at around 3380 Ma, i.e. after a gap of about 320 million years. The closing of OMG basins synchronously with the emplacement of a granitoid phase was at ca.3285 Ma. No other fabric-forming ductile deformation and metamorphism associated with the development of foliation and mineral lineation is known in the rocks of the Singhbhum Archaean craton subsequent to this event. Formation of the succeeding geological ensembles including the deposition of BIF-bearing Iron Ore Group (IOG) and the emplacement of the post-IOG granitoids at ca.3100 Ma can be described as ??lsnon-orogenic?? event taking place during the phase of tectonic quiescence. Supracrustals like the Dhanjori and Simlipal mafic volcanics with intercalated beds of arenite evolved later during the phase of Plume outburst at around 2800 Ma. The end-Archaean intrusion of Newer Dolerite dykes in conjugate sets and the deposition of Kolhan Group in an N-S oriented basin during an E-W stress system mark the culmination of the Archaean crust-building activity in the Singhbhum Archaean craton.  相似文献   

Early Permian xiphosurid trackways from india     

Abhijit Chakraborty  H. N. Bhattacharya 《Journal of the Geological Society of India》2012,80(1):129-135

Present work is the first report of Early Permian xiphosurid trackways from India. Surface trackways and undertracks, preserved within ice-marginal storm-affected, shoreface sediments of the Talchir Formation, Jayanti coalbasin closely resemble Kouphichnium Nopsca 1923. Trackways reveal distinct heteropody with foliate pusher impressions, paired series of semi-circular, oval, V- or Y-shaped chilate (walking) leg impressions. Varied ventral impressions also include telson drag marks and telson dents; spine drag marks, book -gills impression, genal gouges as well as symmetric, paired lateral genal furrows, partial cubichnial impressions of prosoma and spinose opisthosoma. A tentative early Permian age (Asselian/Sakmarian) and marginal marine facies association points towards a paleolimuloidae affinity for the trace makers, which is in conformity with their inferred widths of exoskeleton, sub-rounded prosoma and subtriangular spinose opisthosoma with predictable movable spines. Flexed pusher impressions and co-dominant pincer impressions as well as, other ventral impressions in abundance, confirm crawling as their dominant mode of locomotion. Inferred presence of juvenile crawlers in the community suggests a probable shoreline or marginal marine ecospace.  相似文献   

Characterization and Risk Evaluation of Tea Industry Coal Ash for Environmental Suitability          下载免费PDF全文

Linee Goswami  Prasanta Raul  Banashree Sahariah  Satya Sundar Bhattacharya 《洁净——土壤、空气、水》2014,42(10):1470-1476

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Formulation of Time Series Vegetation Index from Indian Geostationary Satellite and Comparison with Global Product     

Rahul Nigam  Bimal Kumar Bhattacharya  Keshav R. Gunjal  N. Padmanabhan  N. K. Patel 《Journal of the Indian Society of Remote Sensing》2012,40(1):1-9

To study impact of climate change on vegetation time series vegetation index has a vital role to know the behaviour of vegetation dynamics over a time period. INSAT 3A CCD (Charged Couple Device) is the only geostationary sensor to acquire regular coverage of Asia continent at 1 km × 1 km spatial resolution with high temporal frequency (half-an-hour). A formulation of surface reflectances in red, near infrared (NIR), short wave infrared (SWIR) and NDVI from INSAT 3A CCD has been defined and integrated in the operational chain. The atmospheric correction of at-sensor reflectances using SMAC (Simple Model for Atmospheric Correction) model improved the NDVI by 5–40% and also increased its dynamic range. The temporal dynamics of 16-day NDVI composite at 0500 GMT for a growing year (June 2008–March 2009) showed matching profiles with reference to global products (MODIS TERRA) over known land targets. The root mean square deviation (RMSD) between the two was 0.14 with correlation coefficient (r) 0.84 from 200 paired datasets. This inter-sensor cross-correlation would help in NDVI calibration to add continuity in long term NDVI database for climate change studies.  相似文献   

Cenozoic development of southwestern Malay Basin: new insights from subsidence analysis and thermal history     

Muhammad Hassaan  Swapan Kumar Bhattacharya  Manoj Joseph Mathew  Numair Ahmed Siddiqui 《Arabian Journal of Geosciences》2017,10(8):192

Subsidence and thermal history analysis are carried out in order to investigate the Cenozoic basin development of the southwestern (Tenggol Arch and basinal side) part of the Malay basin. Structurally, the southwestern part consists of normal faults and horst and graben geometry. Tectonic subsidence curves show that the basinal side is more active than the Tenggol Arch due to movement along normal faults. Cenozoic development initiated with the deposition of sedimentary Units M & L (Oligocene) and the activation of the Tenggol fault on the basinal side. Several periods of accelerated and slow subsidence are observed during the Oligocene to Middle Miocene that could be associated with changes in regional stresses caused by pulsating plate movement. The Malay Basin experienced inversion throughout the Middle to Late Miocene related to mantle induced slab avalanche effect, causing relatively higher tectonic subsidence rates on the Tenggol Arch compared to the basinal side, suggesting that the Tenggol Arch is less affected by inversion than the basinal side. After a period (Late Miocene) of non-deposition, the basin was reactivated (Pliocene to recent) due to thermal relaxation with thick sedimentation. Paleo heat flows estimated utilizing a novel technique introduced in this study and present day heat flow calibrated using BHT data further supports our results, in that increase in heat flow is related to rapid tectonic subsidence. An anomalously high heat pulse affected the basin during inversion and could be the cause of meta-sediment formation whereas present heat flows, although high compared to average basins, shows decreasing trend from the inversion period.  相似文献   

A critical review of methods for pile design in seismically liquefiable soils   总被引：1，自引：0，他引：1  

S. Bhattacharya  S. P. G. Madabhushi 《Bulletin of Earthquake Engineering》2008,6(3):407-446

Collapse and/or severe damage to pile-supported structures are still observed in liquefiable soils after most major earthquakes. Poor performance of pile foundations remains a great concern to the earthquake engineering community. This review paper compares and contrasts the two plausible theories on pile failure in liquefiable soils. The well established theory of pile failure is based on a flexural mechanism; where the lateral loads on the pile (due to inertia and/or lateral spreading) induce bending failure. This theory is well researched in the recent past and assumes that piles are laterally loaded beams. A more recent theory based on buckling instability treats the piles as laterally unsupported slender columns in liquefiable soils and investigates the buckling instability (bifurcation). The objective of this paper is to investigate the implications to practical pile foundation design that flow from both these theories. Provisions for design made by major international codes of practice for pile design including the Japanese Highway Code (JRA) will be considered. The necessity for such codes to consider alternative forms of failure mechanisms such as the buckling instability of piles in liquefied ground will be discussed. S. Bhattacharya–Previously Departmental Lecturer in Engineering Science, University of Oxford, UK and Fellow of Somerville College, Oxford. S. P. G. Madabhushi–Fellow of Girton College, Cambridge.  相似文献   

Implications of kHz quasi-periodic brightness oscillations in X-ray binaries for neutron star structure     

Arun V. Thampan  Dipankar Bhattacharya  Bhaskar Datta 《Monthly notices of the Royal Astronomical Society》1999,302(4):L69-L73

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Magnetic field evolution of accreting neutron stars -- II     

Sushan Konar †  Dipankar Bhattacharya † 《Monthly notices of the Royal Astronomical Society》1999,303(3):588-594

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