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141.
Mitigation of Iron Toxicity and Iron,Zinc, and Manganese Nutrition of Wetland Rice Cultivars (Oryza sativa L.) Grown in Iron‐Toxic Soil 下载免费PDF全文
142.
143.
Structural analysis of the Chhotanagpur gneiss and the adjoining schistose rocks of the Singhbhum Group indicates perfect
conformity in their structures on macroscopic, mesoscopic and microscopic scales. This precludes the possibility of the gneissic
rocks having intruded into the deformed and metamorphozed schistose rocks. The observed features can be best explained by
considering the gneissic rocks as the basement and the schistose rocks as the cover, both deformed and metamorphozed together.
However, this does not exclude the possibility of the gneissic rocks being reactivated and intruding elsewhere. 相似文献
144.
Dhruba Mukhopadhyay Nandini Chattopadhyay Tapas Bhattacharyya 《Journal of the Geological Society of India》2010,75(1):18-31
The structural geometry of the Anasagar gneiss dome in the axial zone of the South Delhi Fold Belt is controlled by polyphase
folding. It is classified as a thrust-related gneiss dome and not as a metamorphic core complex. Four phases of deformation
have affected both the gneiss and the enveloping supracrustal rocks. D2 and D3 deformations probably represent early and late stages of a progressive deformation episode in a simple shear regime combined
with compression. The contact between the gneiss and the supracrustal rocks is a dislocation plane (thrust) with top-to-east
sense of movement which is consistent with the vergence of the D2 folds. The thrust had a ramp-and-flat geometry at depth. At the present level of exposure it is a footwall flat (that is,
parallel to the gneissosity in the footwall), but it truncates the bedding of the hanging wall at some places and is parallel
at others. The thrusting was probably broadly coeval with the D2 folds and the thrust plane is locally folded by D2. D2 and D3 folds have similar style and orientation as the first and second phases respectively of major folds in the Delhi Supergroup
of the South Delhi Fold Belt and these are mutually correlatable. It is suggested that D1 may be Pre-Delhi in age. Available
geochronological data indicate that the emplacement of the Anasagar gneiss predated the formation of volcanic rocks in the
Delhi Supergroup and also predated the main crust forming event in the fold belt. The Anasagar gneiss and its enveloping supracrustal
rocks are probably older than the Delhi Supergroup. 相似文献
145.
A. Bhattacharyya P. S. Ranhotra J. T. Gergan 《Journal of the Geological Society of India》2011,77(5):401-408
Palynological analysis from a 10 m deep sediment profile from Dokriani valley, Garhwal Himalaya, provides temporal variation
of vegetation vis-à-vis climate and glacier history of the region. This study reveals that between 12,406 and 10,633 cal yr
BP vegetation was sparse when the climate was cool-dry and the glacier snout might had been located at lower elevations in
comparison to its present position. Subsequently around 10,633 cal yr BP, an increase in the growth of diversified taxa close
to the site, indicates the early Holocene climatic amelioration when glacier might have retreated at faster rate. Further,
within Holocene some intermittent cool-dry episodes were recorded around 9,670 to 9,000 cal yr BP and 7,100 cal yr BP when
glacier might have shown reduction in retreat rate or came to stagnation. 相似文献
146.
In earthquake prone areas, understanding of the seismic passive earth resistance is very important for the design of different geotechnical earth retaining structures. In this study, the limit equilibrium method is used for estimation of critical seismic passive earth resistance for an inclined wall supporting horizontal cohesionless backfill. A composite failure surface is considered in the present analysis. Seismic forces are computed assuming the backfill soil as a viscoelastic material overlying a rigid stratum and the rigid stratum is subjected to a harmonic shaking. The present method satisfies the boundary conditions. The amplification of acceleration depends on the properties of the backfill soil and on the characteristics of the input motion. The acceleration distribution along the depth of the backfill is found to be nonlinear in nature. The present study shows that the horizontal and vertical acceleration distribution in the backfill soil is not always in-phase for the critical value of the seismic passive earth pressure coefficient. The effect of different parameters on the seismic passive earth pressure is studied in detail. A comparison of the present method with other theories is also presented, which shows the merits of the present study. 相似文献
147.
Deeper groundwater chemistry and geochemical modeling of the arsenic affected western Bengal basin,West Bengal,India 总被引:1,自引:0,他引:1
A regional scale hydrogeochemical study of a ∼21,000-km2 area in the western Bengal basin shows the presence of hydrochemically distinct water bodies in the main semiconfined aquifer and deeper isolated aquifers. Spatial trends of solutes and geochemical modeling indicate that carbonate dissolution, silicate weathering, and cation exchange control the major-ion chemistry of groundwater and river water. The main aquifer water has also evolved by mixing with seawater from the Bay of Bengal and connate water. The isolated aquifers contain diagenetically altered water of probable marine origin. The postoxic main aquifer water exhibits overlapping redox zones (metal-reducing, sulfidic and methanogenic), indicative of partial redox equilibrium, with the possibility of oxidation in micro-scale environments. The redox processes are depth-dependent and hydrostratigraphically variable. Elevated dissolved As in the groundwater is possibly related to Fe(III) reduction, but is strongly influenced by coupled Fe–S–C redox cycles. Arsenic does not show good correlations with most solutes, suggesting involvement of multiple processes in As mobilization. The main river in the area, the Bhagirathi–Hoogly, is chemically distinctive from other streams in the vicinity and probably has little or no influence on deep groundwater chemistry. Arsenic in water of smaller streams (Jalangi and Ichamati) is probably introduced by groundwater discharge during the dry season. 相似文献
148.
Parminder S. Ranhotra Amalava Bhattacharyya 《Journal of the Geological Society of India》2013,82(2):133-142
Modern pollen-vegetation relationship has been analyzed in respect to vegetational distribution and pollen dispersal from sub-alpine and alpine ecological regimes within the higher reaches of the Gangotri glacier valley. The results in general cope with the local ecological conditions of the sites within the valley. Above the tree line limits, the pollen frequency of arboreal taxa is found lower than those of non-arboreal taxa. In contrast the pine-birch forest area at Chirbasa represented the frequency of arboreal pollen (AP) more than that of non-arboreal pollen (NAP) due to over representation of Pinus wallichiana (conifer). Pollen grains of extra-local arboreal elements, mostly conifers have also been recorded here with fair amount of temperate broad-leaved arboreal taxa viz. Quercus, Alnus, Corylus, Carpinus, Ulmus, Juglans etc. that have been transported by the upthermic winds from their growing limits at lower altitudes to the study sites at higher altitudes. Non-arboreal taxa viz. marshy/aquatic, steppe and of other herbaceaous taxa, represents the existing ecological regimes of their respective sites within the valley. Differential pollen preservation has been observed between the moss cushion and sediment samples from the same site that may be due to the direct exposure of moss cushions to air, thus showing more concentration of wind pollinated pollen-spores as compared to surface sediments. 相似文献
149.
The problem of selecting the optimum operating frequency of a scatterometer, used for remote sensing of sea surface wind speed
has been addressed by applying the criteria of maximum sensitivity of backscattering coefficient to wind speed as well as
its correlation with wind speed. The backscattering coefficient values for sea surface were computed by the two-scale scattering
theory. To compute the atmospheric transmittance, 753 clear sky atmospheres over Indian Ocean were used. While the correlation
coefficient was uniform (0.94) throughout the frequency range of 1 to 30GHz, only frequencies above 5GHz were found sensitive
enough to yield a wind speed accuracy of ±2msec−1 and better, the accuracy improving with frequency. 相似文献
150.
The paper deals with the relationship between the sea surface wind speed (U) and the backscattering coefficient (σ0) for microwave frequencies and quasi specular range of angles. Valenzuela’s effective reflection coefficient based on the theory of scattering of electromagnetic waves from rought dielectric surfaces has been introduced in the expression of backscattering coefficient and the final result compared with the σ0-U relationship derived fromSEASAT scatterometer and concurrent sea truth data. 相似文献