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CHANDRA K. SHARMA 《水文科学杂志》2013,58(3):327-333
Abstract In a mountainous country like Nepal, where precipitation from the monsoon (July) and the westerlies (January) occurs yearly, it is surprising to find partial drought conditions in space and time. This paper deals with the partial drought conditions and also the measures to combat them. 相似文献
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M CHANDRA SEKARAN RAJNEESH BHUTANI S BALAKRISHNAN 《Journal of Earth System Science》2016,125(3):605-622
Pudukkottai region in the northeastern part of the Madurai Block exposes the garnetiferous pink granite that intruded the biotite gneiss. Charnockite patches are associated with both the rock types. Rb–Sr biotite and Sm–Nd whole-rock isochron ages indicate a regional uplift and cooling at ～550 Ma. The initial Nd isotope ratios (\(\varepsilon _{\text {Nd}}^{\mathrm {t}}=-20\) to ?22) and Nd depleted-mantle model ages (TDM = 2.25 to 2.79 Ga) indicate a common crustal source for the pink-granite and associated charnockite, while the biotite gneiss and the charnockite within it represent an older crustal source (\(\varepsilon _{\text {Nd}}^{\mathrm {t}}= -29\) and TDM = > 3.2 Ga). The Rb–Sr whole-rock data and initial Sr–Nd isotope ratios also help demonstrate the partial but systematic equilibration of Sr isotope and Rb/Sr ratios during metamorphic mineral-reactions resulting in an ‘apparent whole-rock isochron’. The available geochronological results from the Madurai Block indicate four major periods of magmatism and metamorphism: Neoarchaean–Paleoproterozoic, Mesoproterozoic, mid-Neoproterozoic and late-Neoproterozoic. We suggest that the high-grade and ultrahigh-temperature metamorphism was preceded by magmatism which ‘prepared’ the residual crust to sustain the high P–T conditions. There also appears to be cyclicity in the tectono-magmatic events and an evolutionary model for the Madurai Block should account for the cyclicity in the preserved records. 相似文献
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The dynamic strength of an ordinary chondrite 总被引：1，自引：0，他引：1
Abstract– Dynamic and quasistatic unconfined compression experiments were performed on samples of the L5 ordinary chondrite MacAlpine Hills (MAC) 88118. The dynamic compressive strength measurements are the first of its kind for a stony meteorite, and indicate that the material tested here exhibits significant increase in compressive strength with increasing strain rate. This increase in compressive strength is larger than the increases typically observed in terrestrial rock specimens compressed over a similar range of strain rates. The details of the failure process are investigated by recording images of the experiments in real time. Specifically, the crack growth speeds in the dynamic compression experiments are measured from ultrahigh‐speed images. These speeds are significantly lower than the speeds observed in terrestrial analogs that are typically used in numerical investigations of large‐scale impacts. The implications of these measurements of strength and failure process are explored in the contexts of atmospheric disruption of meteors and impact cratering/disruption of asteroids. 相似文献
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NAVEEN GANDHI SANJEEV KUMAR S PRAKASH R RAMESH M S SHESHSHAYEE 《Journal of Earth System Science》2011,120(1):99-111
Various experiments involving the measurement of new, regenerated and total productivity using 15N and 13C tracers were carried out in the Bay of Bengal (BOB) and in the Arabian Sea. Results from 15N tracer experiments indicate that nitrate uptake can be underestimated by experiments with incubation time <4 hours. Indirect
evidence suggests pico- and nano-phytoplankton, on their dominance over microphytoplankton, can also influence the f-ratios.
Difference in energy requirement for assimilation of different nitrogen compounds decides the preferred nitrogen source during
the early hours of incubation. Variation in light intensity during incubation also plays a significant role in the assimilation
of nitrogen. Results from time course experiments with both 15N and 13C tracers suggest that photoinhibition appears significant in BOB and the Arabian Sea during noon. A significant correlation
has been found in the productivity values obtained using 15N and 13C tracers. 相似文献
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SIDDHARTHA BHATTACHARYYA APURBA BERA SOMNATH BHARADWAJ N. D. RAMESH BHAT JAYARAM N. CHENGALUR 《Journal of Astrophysics and Astronomy》2017,38(1):17
We developed a generic formalism to estimate the event rate and the redshift distribution of Fast Radio Bursts (FRBs) in our previous publication (Bera et al. 2016), considering FRBs are of an extragalactic origin. In this paper, we present (a) the predicted pulse widths of FRBs by considering two different scattering models, (b) the minimum total energy required to detect events, (c) the redshift distribution and (d) the detection rates of FRBs for the Ooty Wide Field Array (OWFA). The energy spectrum of FRBs is modelled as a power law with an exponent ?α and our analysis spans a range ?3≤α≤5. We find that OWFA will be capable of detecting FRBs with α≥0. The redshift distribution and the event rates of FRBs are estimated by assuming two different energy distribution functions; a Delta function and a Schechter luminosity function with an exponent ?2≤γ≤2. We consider an empirical scattering model based on pulsar observations (model I) as well as a theoretical model (model II) expected for the intergalactic medium. The redshift distributions peak at a particular redshift z p for a fixed value of α, which lie in the range 0.3≤z p ≤1 for the scattering model I and remain flat and extend up to high redshifts (z?5) for the scattering model II. 相似文献
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RANDIVE K R KORAKOPPA M M MULEY S V VARADE A M KHANDARE H W LANJEWAR S G TIWARI R R ARADHI K K 《Journal of Earth System Science》2015,124(1):213-225
Journal of Earth System Science - Green mica (fuchsite or chromian-muscovite) is reported worldwide in the Archaean metasedimentary rocks, especially quartzites. They are generally associated with... 相似文献