Browsing by Author "R. Yadav"

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Abdominal tuberculosis in Indian children
(Springer Verlag, 1996) S.P. Sharma; A.N. Gangopadhyay; S.C. Gopal; D.K. Gupta; R. Yadav
During the period 1980-1991, 166 cases (121 surgically explored and 45 treated conservatively) of abdominal tuberculosis in children were encountered at the Children's Hospital, Institute of Medical Sciences, Banaras Hindu University. Various types of presentations and their management are discussed in the light of pertinent literature.
Geochronology and phase equilibria modelling of ultra-high temperature sapphirine + quartz-bearing granulite at Usilampatti, Madurai Block, Southern India
(John Wiley and Sons Ltd, 2018) D. Prakash; R. Yadav; S. Tewari; H.E. Frimmel; N. Koglin; H.K. Sachan; M.K. Yadav
Sapphirine-bearing granulite from Usilampatti in the Madurai block of southern India preserves a variety of mineral textures and reactions that help in reconstructing a three-stage metamorphic evolution. Corroded biotite, sillimanite and quartz inclusions within garnet represent relics from the prograde history. Peak metamorphic conditions were attained with the development of sapphirine + quartz in textural equilibrium (Stage 1). This was followed by nearly isothermal decompression, leading to the formation of sapphirine + cordierite at Stage 2. Subsequent retrograde hydration (Stage 3) is only locally evident. Using the Perple_X software and the model system NCKFMASH, the peak P-T conditions were estimated from core compositions, and the retrograde evolution was deduced from rim or symplectite compositions of different minerals as computed by isopleths of XMg garnet, XCa garnet, XMg orthopyroxene, XMg sapphirine and XMg biotite. The P-T conditions for Stage 1 thus obtained, and supported by thermodynamic modelling using the winTWQ programme, is approximately 9 kbar and 940°C. Stage 2 conditions were constrained as 6.7 kbar and 900°C. Dating of zircon and monazite in the sapphirine-bearing granulite and associated gneisses by the U-Pb method using LA-ICP-MS indicates metamorphic overprint of zircon (lower intercept ages of discordant data arrays) at 546 ± 8 and 547 ± 11 Ma and metamorphic growth of monazite between 542 ± 3 and 551 ± 2 Ma. Upper intercept ages for zircon point to zircon growth at approximately 2514 ± 66 Ma. Although it remains unclear whether the metamorphic age data refer to Stage 1 or Stage 2 or, most likely, a continuum between both, they clearly document a late Ediacaran age for ultra-high temperature (UHT) metamorphism in the area, which, based on the obtained P-T path, was most likely the result of crustal thickening followed by uplift and erosion. Thus, it is concluded that the sapphirine-bearing granulites formed in response to Pan-African orogeny that led to the collision of the western and eastern Madurai domains, whereas initial zircon growth probably took place during late Neoarchaean arc magmatism that formed much of the western domain. Copyright © 2017 John Wiley & Sons, Ltd. Copyright © 2017 John Wiley & Sons, Ltd.
Inconsistent change in surface hydrography of the eastern Arabian Sea during the last four glacial-interglacial intervals
(Cambridge University Press, 2020) Rajeev Saraswat; S.R. Kurtarkar; R. Yadav; A. Mackensen; D.P. Singh; S. Bhadra; A.D. Singh; M. Tiwari; S.P. Prabhukeluskar; S.R. Bandodkar; D.K. Pandey; P.D. Clift; D.K. Kulhanek; K. Bhishekar; S. Nair
The eastern Arabian Sea is influenced by both the advection of upwelled water from the western Arabian Sea and winter convective mixing. Therefore, sediments collected from the eastern Arabian Sea can help to understand the long-term seasonal hydrographic changes. We used the planktonic foraminifera census and stable isotopic ratio (δ18O) from sediments drilled during the International Ocean Discovery Program Expedition 355 to reconstruct surface hydrographic changes in the eastern Arabian Sea during the last 350 kyr. The increased abundance of Globigerina bulloides suggests enhanced advection of upwelled water during the latter half of MIS7 and the beginning of MIS6, as a result of a strengthened summer monsoon. A large drop in upwelling and/or advection of upwelled water from the western Arabian Sea is inferred during the subsequent interval of MIS6, based on the rare presence of G. bulloides. The comparable relative abundance of Neogloboquadrina dutertrei, G. bulloides and Globigerinoides ruber suggests that during the early part of MIS5, hydrographic conditions were similar to today. The upwelling decreased and winter convection increased with the progress of the glacial interval. A good coherence between planktonic foraminiferal assemblage-based monsoon stacks from both the eastern and western Arabian Sea suggests a coeval response of the entire northern Arabian Sea to the glacial-interglacial changes. The glacial-interglacial difference in δ18Osw-ivc was at a maximum with 4-5 psu change in salinity during Termination 2 and 3, and a minimum during Termination 4. The significantly reduced regional contribution to the glacial-interglacial change in δ18Osw-ivc during Termination 4 suggests a lesser change in the monsoon. © Cambridge University Press 2019.
New Occurrence of Sapphirine-spinel-bearing Granulite from NW of Chilka Lake, Eastern Ghats Belt, Odisha
(Geological Society of India, 2019) D. Prakash; B. Vishal; A.S. Naik; R. Yadav; S.K. Rai; S. Tewari; M.K. Yadav; S. Tiwari; S. Dash; C. Pattnaik
A new locality of sapphirine-spinel-bearing granulites from the Kaithapalli area which lies NW of Chilka Lake, Odisha is reported. The area tectonically forms a northern part of Eastern Ghats belt. It occurs as small enclaves within the khondalite and pelitic granulite. The mineral assemblage includes spinel-sapphirine-garnet-cordierite-orthopyroxene-sillimanite-biotite-k-feldspar-plagioclase-quartz. Development of reaction textures and symplectites are common in the sapphirine-spinel granulites which have been used to describe reaction history. The relative XMg values among various minerals are as follows: cordierite > biotite > sapphirine > orthopyroxene > garnet > spinel. The P-T evolution of these sapphirine-spinel granulites constrained through the pseudosection modelling in the NCKFMASH model system using Perple_X software indicate conditions of ultra-high temperature (UHT) metamorphism. The P-T estimates computed by isopleths define a retrograde trajectory with decompression of c.2.5 kbar from P-Tmax of c.10.5 kbar at c.950 o_C. The sequence of reactions as deduced from the symplectite assemblages, together with pseudosection modelling, from the Kaithapalli area, offer greater opportunities for providing a better picture of petrological evolution of northern part of the Eastern Ghats Belt (EGB). © 2019, Geological Society of India.
Occurrence of kornerupine-bearing granulite from Kunjan locality, Salem district, Tamil Nadu, India
(Indian Academy of Sciences, 2021) D. Prakash; C.K. Singh; R.S. Kumar; R. Yadav; S.K. Rai; M.K. Yadav; Pradip K. Singh; S. Jaiswal
Kornerupine, although a rare mineral, has been reported from several locations around the world in various types of aluminomagnesian Proterozoic rocks subjected to amphibolite and granulite facies metamorphism. Here we report the occurrence of kornerupine in qua-rtzo-feldspathic gneisses near Kunjan town located in the southwestern part of Salem district, Tamil Nadu, India. These kornerupine granulites show well-preserved retrogression texture, involving hydration reactions which helped develop the various mineral assemblages. The common stable assemblage in these granulites is orthopyroxene-cordierite-kornerupme-biotite-spinel-K-feldspar-plagioclase. The P-T conditions of these granulites have been derived using the winTWQ program, which gives results of ~800°C and ~6 kbar for kornerupine-bearing assemblage. The high P-T assemblage reported from this area bears a significant relationship with the metamorphic history and exhumation of the Salem-Namakkal block. © 2021. All Rights Reserved.
Petrology and isotopic evolution of granulites from central Madurai Block (southern India): reference to Ediacaran crustal evolution
(Taylor and Francis Inc., 2018) S. Tewari; D. Prakash; M.K. Yadav; R. Yadav
The Madurai Block, constituting part of the southern granulite terrain in southern India, has contributed significantly towards understanding the UHT (ultrahigh-temperature) granulites that serve as a window into the mid-lower continental crust. The dominant rock types are charnockites, sapphirine-bearing granulites, garnet cordierite gneisses, and quartzites. Significant textural relations reveal multiphase reactions responsible for the formation of diverse mineral parageneses during prolonged metamorphic history of the area. Prograde reaction is evident from the textural relationship where biotite/sillimanite relics are seen as inclusion in garnet/orthopyroxene, suggesting dehydration reactions. The symplectitic assemblages that formed during isothermal decompression involve a series of cordierite-forming reactions, followed by retrogression and cooling. Variety of mineral assemblages present in the rocks of this area offer a wide spectrum of P–T sensors that provide details on the physical conditions of metamorphism. For the rigorous interpretation of the P–T path in the Perumalmalai area, quantitative phase diagrams (P–T pseudosections) have been constructed and contoured for the compositional as well as modal isopleths of involved mineral phases. The rocks of Perumalmalai area document a clockwise decompression P–T trajectory, consistent with crustal thickening followed by extensional collapse. SHRIMP U–Pb ages from zircon associated with sapphirine-bearing granulite facies rocks of Perumalmalai area suggest a widespread Ediacaran tectonothermal event. The occurrence of Ediacaran UHT metamorphism followed by isothermal decompression in the Madurai Block is consistent with the timing and physical conditions associated with the formation of East African Orogen during the amalgamation of Gondwana. © 2017, © 2017 Informa UK Limited, trading as Taylor & Francis Group.
Prograde polyphase regional metamorphism of pelitic rocks, NW of Jamshedpur, eastern India: Constraints from textural relationship, pseudosection modelling and geothermobarometry
(Cambridge University Press, 2020) D. Prakash; D.K. Patel; M.K. Yadav; B. Vishal; S. Tewari; R. Yadav; S.K. Rai; C.K. Singh
The study area belongs to the Singhbhum metamorphic belt of Jharkhand, situated in the eastern part of India. The spatial distribution of the index minerals in the pelitic schists of the area shows Barrovian type of metamorphism. Three isograds, viz. garnet, staurolite and sillimanite, have been delineated and the textural study of the schists has revealed a time relation between crystallization and deformation. Series of folds with shifting values of plunges in the supracrustal rocks having axial-planar schistosity to the folds have been widely cited. Development of these folds could be attributed to the second phase of deformation. In total, two phases of deformation, D1 and D2, in association with two phases of metamorphism, M1 and M2, have been lined up in the study area. Chemographic plots of reactant and product assemblages corresponding to various metamorphic reactions suggest that the pattern of metamorphic zones mapped in space is in coherence with the temporal-sequential change during prograde metamorphism. The prograde P-T evolution of the study area has been obtained using conventional geothermobarometry, internally consistent winTWQ program and Perple_X software in the MnNCKFMASHTO model system. Our observations suggest that the progressive metamorphism in the area is not related to granitic intrusion or migmatization but that it was possibly the ascending plume that resulted in the M1 phase of metamorphism followed by D1 deformation. The second and prime metamorphic phase, M2, with its possible heat source generated by crustal overloading, was preceded by D1 and it lasted until late-to post-D2 deformation. © 2019 Cambridge University Press.
Secure D2D communication in 5G networks
(Newswood Limited, 2018) R. Yadav; S. Sanyal
5G technology is presently the most prominent technologies in network domain. Although, it is said to be available by year 2020, but still there are lot of views about the features and benefits which 5G will offer to the world in comparison with 4G.Also there are lot of discussions about its resource requirements with which our world will enter into a new era of mobile technology after implementing these requirements. With the concept of Internet of Things brought together by 5G, we can expect that this technology will go one step ahead as future network technology. As different application areas as well as new architecture and technologies will grow with 5G, so we can also expect that we will face different security and privacy protection challenges. One of the most promising area of 5G technology is device to device communication. With the growth of such promising technology, we know that since 2G, user privacy and security has been a very important issue. In this paper, we broadly review D2D communication security in 5G networks. At last, future research directions are presented which can strengthen the security of 5G technology. © 2018 Newswood Limited. All rights reserved.