Rare,metal micrometeorites from the Indian Ocean     

M. Shyam Prasad  N. G. Rudraswami  Agnelo Alexandre De Araujo  V. D. Khedekar 《Meteoritics & planetary science》2019,54(2):290-299

Metal in various forms is common in almost all meteorites but considerably rare among micrometeorites. We report here the discovery of two metal micrometeorites, i.e., (1) an awaruite grain similar to those found in the metal nodules of CV chondrites and (2) a metal micrometeorite of kamacite composition enclosing inclusions of chromite and merrillite. This micrometeorite appears to be a fragment of H5/L5 chondrite. These metal micrometeorites add to the inventory of solar system materials that are accreted by the Earth in microscopic form. They also strengthen the argument that a large proportion of material accreted by the Earth that survives atmospheric entry is from asteroidal sources.  相似文献   

Spatio‐temporal prediction of land surface temperature using semantic kriging     

Shrutilipi Bhattacharjee  Jia Chen  Soumya K. Ghosh 《Transactions in GIS》2020,24(1):189-212

Spatio‐temporal prediction and forecasting of land surface temperature (LST) are relevant. However, several factors limit their usage, such as missing pixels, line drops, and cloud cover in satellite images. Being measured close to the Earth's surface, LST is mainly influenced by the land use/land cover (LULC) distribution of the terrain. This article presents a spatio‐temporal interpolation method which semantically models LULC information for the analysis of LST. The proposed spatio‐temporal semantic kriging (ST‐SemK) approach is presented in two variants: non‐separable ST‐SemK (ST‐SemK_NSep) and separable ST‐SemK (ST‐SemK_Sep). Empirical studies have been carried out with derived Landsat 7 ETM+ satellite images of LST for two spatial regions: Kolkata, India and Dallas, Texas, U.S. It has been observed that semantically enhanced spatio‐temporal modeling by ST‐SemK yields more accurate prediction results than spatio‐temporal ordinary kriging and other existing methods.  相似文献   

Classification of glacial lakes using integrated approach of DFPS technique and gradient analysis using Sentinel 2A data     

Prateek Verma  Sanjay Kumar Ghosh 《国际地球制图》2019,34(10):1075-1088

It is important to identify and locate glacial lakes for assessing any potential hazard. This study presents a combination of semi-automatic method Double-Window Flexible Pace Search (DFPS) and edge detection technique to identify glacial lakes using Sentinel 2A satellite data. Initially, Normalized Difference Water Index (NDWI) has been used to identify water and non-water areas, while DFPS and Edge detection technique has been used to identify an optimum threshold value to distinguish between water and shadow areas. The optimal threshold from DFPS process is 0.21, while threshold value of gradient magnitude using edge detection process is 0.318. The number of glacial lakes identified using the above algorithm is in close agreement with previously published results on glacial lakes in Gangotri glacier using different techniques. Thus, a combination of DFPS and edge detection process has successfully segregated glacial lakes from other features present in Gangotri glacier.  相似文献   

Biosedimentary record of postglacial coastal dynamics: high‐resolution sequence stratigraphy from the northern Tuscan coast (Italy)     

Alessandro Amorosi  Veronica Rossi  Daniele Scarponi  Stefano Claudio Vaiani  Anupam Ghosh 《Boreas: An International Journal of Quaternary Research》2014,43(4):939-954

Integrating analysis of the benthic palaeoecological record with multivariate ordination techniques represents a powerful synergy able to provide an improved characterization of coastal depositional facies in a sequence stratigraphical perspective. Through quantitative analysis of benthic foraminifer, ostracod and mollusc associations from the postglacial succession of Core M3 (Arno coastal plain, Tuscany, Italy), and application of detrended correspondence analysis (DCA) to the mollusc sub‐data set, we offer a refined picture of stratigraphical variations in faunal content from a paralic depositional setting, and reconstruct the palaeoenvironmental gradients that account for such variations. Despite distinct ecological behaviours, and taphonomic and sedimentological constraints, a strong ecological control on meio‐ and macrofaunal biofacies and taxa turnover is documented across the study succession. Amongst all possible mechanisms that may play a role in ‘shaping’ fossil distribution, the ecological signal driven by salinity represents the most prominent factor controlling the composition of fossil associations in the cored succession. Molluscs can even provide outstanding quantitative estimates of palaeosalinity along the sampled core. When plotted stratigraphically, the three fossil sub‐data sets show consistent patterns of vertical evolution that enable prompt identification of the key surfaces for sequence stratigraphical interpretation in otherwise lithologically indistinguishable deposits. The concomitant maximum richness of species with strong marine affinity, paralleled by the highest DCA salinity estimates, allows recognition of the maximum flooding zone, dated to ～7.7 cal. ka BP, within a homogeneous succession of outer lagoon clays. These clays are sandwiched between early transgressive, swamp to inner lagoon deposits and overlying prograding coastal?alluvial plain facies.  相似文献   

On the photogravitational R4BP when the third primary is a triaxial rigid body     

Md Chand Asique  Umakant Prasad  M. R. Hassan  Md Sanam Suraj 《Astrophysics and Space Science》2016,361(12):379

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Smearing of mass accretion rate variation by viscous processes in accretion disks in compact binary systems     

A. Ghosh  Sandip K. Chakrabarti 《Astrophysics and Space Science》2016,361(9):310

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Probing Statistical Isotropy of Cosmological Radio Sources using Square Kilometre Array     

Shamik Ghosh  Pankaj Jain  Gopal Kashyap  Rahul Kothari  Sharvari Nadkarni-Ghosh  Prabhakar Tiwari 《Journal of Astrophysics and Astronomy》2016,37(4):25

There currently exist many observations which are not consistent with the cosmological principle. We review these observations with a particular emphasis on those relevant for the Square Kilometre Array (SKA). In particular, several different data sets indicate a preferred direction pointing approximately towards the Virgo cluster. We also observe a hemispherical anisotropy in the Cosmic Microwave Background radiation (CMB) temperature fluctuations. Although these inconsistencies may be attributed to systematic effects, there remains the possibility that they indicate new physics and various theories have been proposed to explain them. One possibility, which we discuss in this review, is the generation of perturbation modes during the early pre-inflationary epoch, when the Universe may not obey the cosmological principle. Better measurements will provide better constraints on these theories. In particular, we propose measurement of the dipole in number counts, sky brightness, polarized flux and polarization orientations of radio sources. We also suggest test of alignment of linear polarizations of sources as a function of their relative separation. Finally we propose measurement of hemispherical anisotropy or equivalently dipole modulation in radio sources.  相似文献   

Implementing climate change adaptation: lessons from India’s national adaptation fund on climate change (NAFCC)     

Ravi S. Prasad 《Climate Policy》2019,19(3):354-366

With poverty alleviation and sustainable development as key imperatives for a developing economy like India, what drives the resource-constrained state governments to prioritize actions that address climate change impacts? We examine this question and argue that without access to additional earmarked financial resources, climate action would get overshadowed by developmental priorities and effective mainstreaming might not be possible. A systematic literature review was carried out to draw insights from the current state of implementation of adaptation projects, programmes and schemes at the subnational levels, along with barriers to mainstreaming climate change adaptation. The findings from a literature review were supplemented with lessons emerging from the implementation of India’s National Adaptation Fund on Climate Change (NAFCC). The results of this study underscore the scheme’s relevance.

Key policy insights

• Experience with NAFCC implementation reveals that states require sustained ‘handholding’ in terms of financial, technical and capacity support until climate change issues are fully understood and embedded in the policy landscape.

• Domestic sources of finance are critically important in the absence of predictable and adequate adaptation finance from international sources.

• The dedicated window for climate finance fosters a spirit of competitive federalism among states and encourages enhanced climate action.

• Enhanced budgetary allocation to NAFCC to strengthen the state-level adaptation response and create capacity to mainstream climate change concerns in state planning frames, is urgently needed.

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Radon emanation of heterogeneous basin deposits in Kathmandu Valley,Nepal     

Frédéric Girault  Ananta Prasad Gajurel  Frédéric Perrier  Bishal Nath Upreti  Patrick Richon 《Journal of Asian Earth Sciences》2011,40(2):595-610

Effective radium-226 concentration (EC_Ra) has been measured in soil samples from seven horizontal and vertical profiles of terrace scarps in the northern part of Kathmandu Valley, Nepal. The samples belong to the Thimi, Gokarna, and Tokha Formations, dated from 50 to 14 ky BP, and represent a diverse fluvio-deltaic sedimentary facies mainly consisting of gravelly to coarse sands, black, orange and brown clays. EC_Ra was measured in the laboratory by radon-222 emanation. The samples (n = 177) are placed in air-tight glass containers, from which, after an accumulation time varying from 3 to 18 days, the concentration of radon-222, radioactive decay product of radium-226 and radioactive gas with a half-life of 3.8 days, is measured using scintillation flasks. The EC_Ra values from the seven different profiles of the terrace deposits vary from 0.4 to 43 Bq kg^?1, with profile averages ranging from 12 ± 1 to 27 ± 2 Bq kg^?1. The values have a remarkable consistency along a particular horizon of sediment layers, clearly demonstrating that these values can be used for long distance correlations of the sediment horizons. Widely separated sediment profiles, representing similar stratigraphic positions, exhibit consistent EC_Ra values in corresponding stratigraphic sediment layers. EC_Ra measurements therefore appear particularly useful for lithologic and stratigraphic discriminations. For comparison, EC_Ra values of soils from different localities having various sources of origin were also obtained: 9.2 ± 0.4 Bq kg^?1 in soils of Syabru–Bensi (Central Nepal), 23 ± 1 Bq kg^?1 in red residual soils of the Bhattar-Trisuli Bazar terrace (North of Kathmandu), 17.1 ± 0.3 Bq kg^?1 in red residual soils of terrace of Kalikasthan (North of Trisuli Bazar) and 10 ± 1 Bq kg^?1 in red residual soils of a site near Nagarkot (East of Kathmandu). The knowledge of EC_Ra values for these various soils is important for modelling radon exhalation at the ground surface, in particular in the vicinity of active faults. Importantly, the study also reveals that, above numerous sediments of Kathmandu Valley, radon concentration in dwellings can potentially exceed the level of 300 Bq m^?3 for residential areas; a fact that should be seriously taken into account by the governmental and non-governmental agencies as well as building authorities.  相似文献   

Subsurface structure derived from detailed gravity and magnetic investigations along the Pala-Maneri traverse of the Main Central Thrust,NW Himalaya     

T. Seshunarayana  B. Rajendra Prasad  A. S. S. S. R. S. Prasad  D. Mysaiah 《Journal of the Geological Society of India》2011,77(3):213-218

A detailed, integrated gravity and magnetic study across the Main Central Thrust (MCT) along the Pala-Maneri traverse in Uttaranchal, NW Himalaya was carried out. The gravity data was acquired using a CG-3 gravity meter with an accuracy of 0.005 mGal, while magnetic data was acquired using a proton precession magnetometer with a station interval of 20 m. Data was collected along a 11.7 km, NE-SW traverse from Pala to Maneri along the proposed route of a hydroelectric headrace tunnel. The measured variation in the gravity field was approximately 70 mGal, with two prominent highs recorded at distances of 0.5 km, 7.5 km and lows at 3.0 km, 10.5 km from Maneri. The gravity highs can be attributed to presence of high-density rocks along the thrust planes. The sharp gravity low recorded at 10.5 km distance possibly indicates a sympathetic fault of the MCT that is highly saturated with fluids (water). The broad gravity low between 2.5 km and 4.0 km distance is likely to represent the gravity signature of the MCT itself. The measured variation in the magnetic field was approximately 285 nT. The associated gravity and magnetic signatures located several faults along the traverse including presence of the MCT at Kumaltigad.  相似文献