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91.
92.
93.
The early Mesoproterozoic Rohtas Limestone in the Son valley area of central India represents an overall shallowing-upward
carbonate succession. Detailed facies analysis of the limestone reveals outer- to inner-shelf deposition in an open marine
setting. Wave-ripples, hummocky cross stratifications and edgewise conglomerates argue against a deep marine depositional
model for the Rohtas Limestone proposed earlier. Stable isotope analysis of the limestone shows that δ13C and δ18O values are compatible with the early Mesoproterozoic open seawater composition. The ribbon limestone facies in the Rohtas
Limestone is characterized by micritic beds, each decoupled in a lower band enriched and an upper band depleted in dissolution
seams. Band-wise isotopic analysis reveals systematic short-term variations. Comparative enrichment of the heavier isotopes
in the upper bands is attributed to early cementation from sea water and water derived from the lower band undergoing dissolution
because of lowering of pH at depth. The short-term positive shifts in isotopic compositions in almost every upward gradational
transition from a seamed band to a non-seamed band support the contention that dissolution seams here are of early diagenetic
origin, although their formation was accentuated under overburden pressure. 相似文献
94.
Gravitational field of a stationary circular cosmic string loop has been studied in the context of full nonlinear Einstein's
theory of gravity. It has been assumed that the radial and tangential stresses of the loop are equal to the energy density
of the string loop. An exact solution for the system has been presented which has a singularity at a finite distance from
the axis, but is regular for any other distances from the axis of the loop.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
95.
The LC50 of Malathion for Channu punctatus is determined for 24… 96 h of exposure as 10.95… 3.22 mg/l. At exposure to 2.5 mg./l Malathion, growth–measured by increase in weight–is significantly reduced from the 19th day and reduced by 10 % till the 31st day. During the same period of time, the RNA and protein contents of the muscle is lowered by 10 and 15 %, respectively, as compared with the control. In addition to an acute toxic effect, in sublethal concentrations Malathion has also pronounced effects on growth and metabolism. 相似文献
96.
In the Schirmacher Hills, most of the ductile shearing took place under high to medium grade amphibolite facies metamorphism. The microstructure of the mylonites shows characteristic features of high temperature deformation and thus gives us an idea of deformation mechanisms of the constituent minerals at great crustal depth. The variation in microstructure of the sheared rock is partly due to heterogeneity of the intensity of strain from domain to domain, producing protomylonites, orthomylonites and ultramylonites. However, a large part of the microstructural variation has resulted from syn- to post-tectonic recrystallization and grain growth of constituent minerals. Both quartz and feldspar have deformed by crystal plastic processes with dominant grain boundary migration. The present aspect ratio of the feldspar grains is a result of various degrees of dynamic recrystallization along the grain boundary. The ratio varies between 1.5 and 2. Presence of exsolution lamellae in perthites and formation of myrmekite at the strained grains of K-feldspar suggest diffusion assisted dislocation creep. These mylonites are characterized by the presence of weakly strained or unstrained long quartz ribbons. The development of quartz ribbons with the absence of significant strain suggests grain recovery and grain growth during high temperature mylonitization. The growth of quartz ribbons took place by coalescing neighbouring grains both along and across the ribbon length. At the ultramylonite stage the fine-grained matrix of quartz and feldspar mostly accommodates the bulk strain. 相似文献
97.
Santanu Banerjee S.K. Bhattacharya Subir Sarkar 《Journal of Asian Earth Sciences》2007,29(5-6):823-831
Variations of carbon and oxygen isotopic ratios in response to cyclical sea level fluctuations have been documented from a Paleoproterozoic peritidal stromatolite succession. The upper division of the Kajrahat Limestone, Vindhyan Supergroup of central India consists of several shallowing upward stromatolite cycles identified by regular and systematic changes in stromatolite size. Normally, larger stromatolites are followed upward in the succession by smaller stromatolites and microbial laminites that occupy the top of the cycle. Desiccation cracks are found in all the facies indicating subaerial exposure. We investigated the stable isotope compositional variations across nine complete stromatolite cycles showing frequent subaerial emergence. Carbon and oxygen isotopic values of the limestones, in general, are comparable to contemporary marine values available from earlier studies but show regular depletion in response to shallowing of the water level. The δ13C and δ18O values of the limestones vary within an individual stromatolite cycle; depleted values characterize the topmost part of the cycles. The isotope pattern is explained by micritic carbonate deposition in different sub environments of the shallow marine domain having different salinity and variable duration of exposure. These variations also probably caused the observed scatter in δ13C and δ18O values of supratidal microbial laminites. 相似文献
98.
99.
Temperature dependence of magnetic susceptibility in an argon environment: implications for pedogenesis of Chinese loess/palaeosols 总被引:15,自引:0,他引:15
100.
William Johnston Nilanjan Banerjee Jackson Cothren James P. Parkerson 《Transactions in GIS》2014,18(4):555-573
Information‐rich maps are today rendered from powerful back‐end servers. Unfortunately, there may be circumstances in which access to such Internet‐resident web services is infeasible or unreliable. These disconnected environments can theoretically occur during major power outages, malicious attacks on communications infrastructure, natural disasters, or in remote operating environments. One might also envision applications in which a disconnected service is preferred over Internet‐resident services, such as when the local internet service is overloaded with traffic, making communication though it difficult. To this end, this article presents a software stack (a map stack) that can serve GIS information from low power embedded nodes. The system combines a spatially enabled SQL database, location‐based routing, and multi‐scale map rendering to serve information‐rich GIS data on common hand‐held devices at minimal energy consumption. The maps are rendered on browsers on off‐the‐shelf mobile devices such as smart phones and tablets. The system also provides a crowd sourced capability where end users can annotate maps with up‐to‐date information on the scene of the natural disaster. We have prototyped a fully functional map stack on a battery powered Gumstix Overo air platform. We show that the map stack is a highly extensible platform that provides low latency, and low energy dissemination of maps during a natural disaster. 相似文献