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531.
The Southern Granulite Terrain with exposed Archean lower crustal rocks is studied using various geophysical tools. The crustal structure derived from seismic reflection and refraction/wide-angle reflection studies is used to understand the tectonic evolution of the region. Deep seismic reflection section along the Kolattur–Palani segment shows an oppositely dipping reflection fabric near the Moyar–Bhavani shear zone, which is interpreted as a signature of collision between the Dharwar craton and another crustal block in the south. The thickened crust due to collision was delaminated during the orogenic collapse and modified the central part, covering the Cauvery Shear Zone system, located between the Moyar–Bhavani and Karur–Oddanchatram shear zones. The delaminated lower crust is altered by magmatic underplating as evidenced by the high velocity layer just above the Moho. The velocity model of the region indicates crustal thickening at the boundary of the Dharwar craton and Moyar–Bhavani shear zone and thinning further south. Back-scattered seismic wave field with negative moveout and the Moho-offset indicate the spatial location and strike-slip nature of the shear zones. Present study suggests that the late Archean collision and suturing of the Dharwar craton with the southern crustal block at the Moyar–Bhavani shear zone may be responsible for the evolution of late Archean granulites. Late Neoproterozoic rifting is observed along the paleo-fault zones. The seismic studies constrained by gravity, magnetic and magnetotelluric data suggest that the Moyar–Bhavani and Karur–Oddanchatram shear zones of the Cauvery Shear Zone system mark terrane boundaries/suture zones. 相似文献
532.
The exposure of Puntius sophore to different concentrations of crude oil (200… 4000 ppm) revealed that 4000 ppm was acutely lethal to the fish and mortality did not occur at <500 ppm at 21±1 °C for up to 15 days. The increase in the opercular frequency during exposure to crude oil has been recorded almost parallel to toxicant concentrations. The objectionable odour of the crude oil and the formation of coagulated mucous film over the body and gills were the main factors causing mortality among the experimental fish. The 24, 48, 78 and 96-h TL 50 values have been 3275, 1750, 1650 and 1450 ppm. The corresponding regression coefficients b were –1.8056, –1.5849, –1.6037 and –1.6497. 相似文献
533.
In four tropical water works there are carried out investigations on the floc rising occurring during the day-hours, and especially in the hot season, in the flocculators. This phenomenon is caused by the great heating of the raw water during the day-hours, due to which between 10.00 a. m. and 10.00 p. m. a temperature difference up to 3.7 K between the influent and the effluent of the flocculators occurs during a retention period of 3.5… 5 h within the flocculators. Even temperature differences of only 1 K result in floc rising, reducing the filter run by four to seven hours. Oversaturation of the raw water with oxygen by the photosynthetic oxygen production constitutes an additional cause. As a measure against the rising and passing-on of flocs we recommend the aeration of the water at the raw water intake point, to prevent a thermal stratification during the day-hours and at the same time to remove the perhaps given oxygen oversaturation. 相似文献
534.
N Subba Reddy V Pulla Reddy A Annamalai C R K Prasad 《Journal of Earth System Science》1982,91(1):55-63
The magnetite-quartzites of Nainarmalai forms part of a large iron ore belt of Tamilnadu which occurs in a high grade granulite terrain. They are associated with basic granulites and gneisses. Mineralogical and chemical studies indicate their similarities with other metasedimentary iron ores. 相似文献
535.
Matthew P. Peters Stephen N. Matthews Louis R. Iverson Anantha M. Prasad 《International journal of geographical information science》2014,28(8):1547-1560
Species distribution models (SDM) are commonly used to provide information about species ranges or extents, and often are intended to represent the entire area of potential occupancy or suitable habitat in which individuals occur. While SDMs can provide results over various geographic extents, they normally operate within a grid and cannot delimit distinct, smooth boundaries. Additionally, there are instances where a zone of primary occupancy (i.e., a mostly continuous region where species exists, excluding outliers) is better suited for particular analyses, such as when examining source/sink population dynamics or modeling movement into new habitats. We present a semi-automated method to delineate a generalized species boundary (GSB) from SDM output, which provides a practical alternative to digitizing. This preliminary boundary is then manually updated based on inventory data and historical ranges. We used the method to generate contemporary boundaries for 132 tree species of the eastern United States, which are complementary to the ranges generated by Elbert Little for North America during the 1970s, but are not replacements. The methods we present can broadly be applied to other grid-based SDM to generate GSBs. 相似文献
536.
Global climate change is expected to result in greater variation in snow cover and subsequent impacts on land surface hydrology and vegetation production in the high Trans Himalayan region (THR). This paper examines how the changes in timing and duration of snow cover affect the spatio-temporal pattern of rangeland phenology and production in the region. Moderate Resolution Imaging Spectrometer (MODIS) 16-day normalized difference vegetation index (NDVI) data from 2000 to 2009 and concurrent snow cover, precipitation and temperature data were analyzed. In contrast to numerous studies which have suggested that an earlier start of the season and an extension of the length of the growing season in mid and higher latitude areas due to global warming, this study shows a delay in the beginning of the growing season and the peak time of production, and a decline in the length of growing season in the drier part of THR following a decline and a delay in snow cover. Soil moisture in the beginning of the growing season and consequent rangeland vegetation production in drier areas of the THR was found to be strongly dependent upon the timing and duration of snow cover. However, in the wetter part of the THR, an earlier start of season, a delay in end of season and hence a longer growing season was observed, which could be attributed to warming in winter and early spring and cooling in summer and late spring and changes in timing of snow melt. The study shows a linear positive relationship between rangeland vegetation production and snow cover in the drier parts of THR, a quadratic relationship near to permanent snow line, and a negative linear relationship in wetter highlands. These findings suggest that, while temperature is important, changes in snow cover and precipitation pattern play more important roles in snow-fed, drier regions for rangeland vegetation dynamics. 相似文献
537.
Climate Dynamics - A proper knowledge and understanding of wind-wave characteristics and its variability on basin, regional and local scales have profound importance and practical applications in... 相似文献
538.
Impact of period and timescale of FDDA analysis nudging on the numerical simulation of tropical cyclones in the Bay of Bengal 总被引:1,自引:0,他引:1
V. Yesubabu C. V. Srinivas S. S. V. S. Ramakrishna K. B. R. R. Hari Prasad 《Natural Hazards》2014,74(3):2109-2128
In this study, the impact of four-dimensional data assimilation (FDDA) analysis nudging is examined on the prediction of tropical cyclones (TC) in the Bay of Bengal to determine the optimum period and timescale of nudging. Six TCs (SIDR: November 13–16, 2007; NARGIS: April 29–May 02, 2008; NISHA: November 25–28, 2008; AILA: May 23–26, 2009; LAILA: May 18–21, 2010; JAL: November 04–07, 2010) were simulated with a doubly nested Weather Research and Forecasting (WRF) model with a horizontal resolution of 9 km in the inner domain. In the control run for each cyclone, the National Centers for Environmental Prediction (NCEP) Global Forecast System (GFS) analysis and forecasts at 0.5° resolution are used for initial and boundary conditions. In the FDDA experiments available surface, upper air observations obtained from NCEP Atmospheric Data Project (ADP) data sets were used for assimilation after merging with the first guess through objective analysis procedure. Analysis nudging experiments with different nudging periods (6, 12, 18, and 24 h) indicated a period of 18 or 24 h of nudging during the pre-forecast stage provides maximum impact on simulations in terms of minimum track and intensity forecasts. To determine the optimum timescale of nudging, two cyclone cases (NARGIS: April 28–May 02, 2008; NISHA: November 25–28, 2008) were simulated varying the inverse timescales as 1.0e?4 to 5.0e?4 s?1 in steps of 1.0e?4 s?1. A positive impact of assimilation is found on the simulated characteristics with a nudging coefficient of either 3.0e?4 or 4.0e?4 s?1 which corresponds to a timescale of about 1 h for nudging dynamic (u,v) and thermodynamical (t,q) fields. 相似文献
539.
Md. M. R. Khan M. Z. B. Mukhlish M. S. I. Mazumder K. Ferdous D. M. R. Prasad Z. Hassan 《International Journal of Environmental Science and Technology》2014,11(4):1027-1034
Adsorption characteristics of water hyacinth roots powder for the removal of Indosol Dark-blue GL dye were investigated in batch mode. Operating variables, such as initial solution pH, presence of detergent, adsorbent dosage, initial concentration and contact time, were studied. The results showed that the adsorption of dye increased with increasing the initial concentration and contact time. The adsorption is highly pH dependent and adsorption capacity increased with decrease in pH. Kinetic study revealed that the uptake of Indosol Dark-blue GL was very rapid within the first 15 min and equilibrium time was independent of initial concentration. Batch equilibrium experiments were carried out at different pH and found that equilibrium data fitted well to Langmuir isotherm model. The maximum sorption capacity of the adsorbent was found as 86 mg g?1 at pH 3 which reduced to 64 mg g?1 at pH 5. The presence of detergent reduced the sorption capacity of the adsorbent significantly. Using equilibrium and kinetic data, the forward and backward rate constants were determined from the unified approach model. Desorption study revealed that the dye can be recovered by swing the pH from low to high. 相似文献
540.
Holocene climate variability and cultural evolution in the Near East from the Dead Sea sedimentary record 总被引:4,自引:2,他引:2
Claudia Migowski Mordechai Stein Sushma Prasad Jrg F.W. Negendank Amotz Agnon 《Quaternary Research》2006,66(3):421-431
A comprehensive record of lake level changes in the Dead Sea has been reconstructed using multiple, well dated sediment cores recovered from the Dead Sea shore. Interpreting the lake level changes as monitors of precipitation in the Dead Sea drainage area and the regional eastern Mediterranean palaeoclimate, we document the presence of two major wet phases ( 10–8.6 and 5.6–3.5 cal kyr BP) and multiple abrupt arid events during the Holocene. The arid events in the Holocene Dead Sea appear to coincide with major breaks in the Near East cultural evolution (at 8.6, 8.2, 4.2, 3.5 cal kyr BP). Wetter periods are marked by the enlargement of smaller settlements and growth of farming communities in desert regions, suggesting a parallelism between climate and Near East cultural development. 相似文献