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101.
S. Satheesh A. R. Soniamby C. V. Sunjaiy Shankar S. Mary Josephine Punitha 《中国海洋大学学报(英文版)》2012,11(3):354-360
The present study aimed at assessing the antifouling activity of bacteria associated with marine sponges. A total of eight bacterial strains were isolated from the surface of sponge Sigmadocia sp., of them, SS02, SS05 and SS06 showed inhibitory activity against biofilm-forming bacteria. The extracts of these 3 strains considerably affected the extracellular polymeric substance producing ability and adhesion of biofilm-forming bacterial strains. In addition to disc diffusion assay, microalgal settlement assay was carried out with the extracts mixed with polyurethane wood polish and coated onto stainless steel coupons. The extract of strain SS05 showed strong microalgal settlement inhibitory activity. Strain SS05 was identified as Bacillus cereus based on its 16S rRNA gene. Metabolites of the bacterial strains associated with marine invertebrates promise to be developed into environment-friendly antifouling agents. 相似文献
102.
Ton Snelder José Barquín Ortiz Doug Booker Nicolas Lamouroux Hervé Pella Ude Shankar 《Aquatic Sciences - Research Across Boundaries》2012,74(1):45-59
Top-down methods for defining stream classifications are based on a conceptual model or expert-defined rules, whereas bottom-up
methods use biological training data and statistical modelling. We compared the performance of six classification methods
for explaining the taxonomic composition of invertebrate and fish assemblages recorded at 327 and 511 sites, respectively,
distributed throughout France. Classification 1 and 2 were top-down classifications; The European Water Framework System A
(WFDa,) and the French Hydro-ecoregions (HER 2). Four bottom-up classification procedures of increasing complexity were defined
based on 11 variables that included watershed characteristics describing climate, topography, and geology, and site characteristics
including elevation, bed slope and temperature. Classification 3 was defined using matrix correlation (MC) to select a combination
of variable categories that produced the best discrimination of the observed taxonomic composition. Classification 4 and 5
were defined by clustering the sites based on their taxonomic data and then using linear discriminant analysis (LDA) and Random
forests (RF) to discriminate the clusters based on the environmental variables. Classification 6 was defined using generalized
dissimilarity modelling (GDM). Our hypothesis was that the bottom-up classifications would perform better because they flexibly
accommodate complex relationships between compositional and environmental variation. We tested the classifications using the
classification strength statistic (CS). The RF-based classification fitted the taxonomic patterns better than GDM or LDA and these latter classifications generally
fitted better than the MC, WFDa or HER classifications. Cross validation analysis showed that differences in predictive CS (i.e. the CS statistics produced from sites not used in defining the classifications) were often significant. However, these differences
were generally small. Gains in predictive performance of classifications appear to be small relative to the increase in complexity
in the manner in which environmental variables are combined to define classes. 相似文献
103.
Sushma Panigrahy Gargi Upadhyay Shibendu Shankar Ray Jai S. Parihar 《Journal of the Indian Society of Remote Sensing》2010,38(4):627-632
The present study has been carried out to delineate the existing cropping systems in the Indo-Gangetic Plains (IGP) using
10 day composite SPOT VEGETATION (VGT) NDVI data acquired over a crop year (June–May). Results showed that it is feasible
to identify the major crops like rice, wheat, sugarcane, potato, and cotton in the dominant growing areas with good accuracy.
Double cropping pattern is the most prevalent. Rice-wheat, sugarcane based, cotton-wheat, rice-potato, rice-rice, maize/millet-wheat
are some of the major rotations followed. Rice-wheat is the dominant rotation accounting for around 40% of the net sown area.
Triple crop rotations was less than 5% of the area and observed in some parts of Uttar Pradesh, Bihar and West Bengal. Single
crop rotation of rice-fallow is significant only in West Bengal. 相似文献
104.
Geothermal modeling of the gas hydrate stability zone along the Krishna Godavari Basin 总被引:1,自引:1,他引:0
A wide-spread bottom simulating reflector (BSR), interpreted to mark the thermally controlled base of the gas hydrate stability zone, is observed over a close grid of multichannel seismic profiles in the Krishna Godavari Basin of the eastern continental margin of India. The seismic data reveal that gas hydrate occurs in the Krishna Godavari Basin at places where water depths exceed 850 m. The thickness of the gas hydrate stability zone inferred from the BSR ranges up to 250 m. A conductive model was used to determine geothermal gradients and heat flow. Ground truth for the assessment and constraints on the model were provided by downhole measurements obtained during the National Gas Hydrate Program Expedition 01 of India at various sites in the Krishna Godavari Basin. Measured downhole temperature gradients and seafloor-temperatures, sediment thermal conductivities, and seismic velocity are utilized to generate regression functions for these parameters as function of overall water depth. In the first approach the base of gas hydrate stability is predicted from seafloor bathymetry using these regression functions and heat flow and geothermal gradient are calculated. In a second approach the observed BSR depth from the seismic profiles (measured in two-way travel time) is converted into heat flow and geothermal gradient using the same ground-truth data. The geothermal gradient estimated from the BSR varies from 27 to 67°C/km. Corresponding heat flow values range from 24 to 60 mW/m2. The geothermal modeling shows a close match of the predicted base of the gas hydrate stability zone with the observed BSR depths. 相似文献
105.
Prabal Shankar Das Rima Chatterjee Sumangal Dasgupta Ranajit Das Debjani Bakshi Mukesh Gupta 《Geophysical Prospecting》2019,67(1):150-166
Sands belonging to Kamalapuram Formation of Paleocene-Eocene age are deposited in Cauvery basin as incised valley fill during a regressive cycle. Here we attempt to quantify the influence of diagenesis on pore-filling materials using rock physics template constrained by geohistory modelling. Primarily, porosity–velocity and acoustic impedance – the ratio of P-wave and S-wave velocity (VP/Vs) cross-plots are used as rock physics templates. Rock physics template has efficiently quantified pore-filling materials namely; contact cement and non-contact cement. The estimated contact cement and non-contact cement are correlated with conventional petrophysical logs within the selected depth interval. Further, this correlation is used to interpret the composition of pore-filling materials. Shallower depth intervals (I and II) exhibit moderate non-contact cement (4–5%) and insignificant contact cement (1–2% approx.) depositions. However, deeper interval (III) records a significant amount of pore-filling materials amounting average of 12% non-contact cement and 4% contact cement. Pore-filling materials demonstrate a positive correlation with the depth of burial. The fluid response is substantially affected by the degree of diagenesis, composition and spatial distribution of pore-filling materials. Shallower depth intervals (1770–1786 m and 1858–1878 m) are relatively more sensitive to fluid changes as it is affected by insignificant contact cement. The depth interval 1770–1786 m shows class II (oil) and class III (gas) amplitude variation with offset anomalies. The sand occurring in depth interval 1858–1878 m demonstrates class IIP (oil) and II (gas) anomaly. The deeper interval (2118–2170 m) is comparatively stiffer and demonstrates class I amplitude variation with offset (oil and gas sand) anomaly. 相似文献
106.
A three-dimensional finite difference transport model appropriate for the coastal environment is developed for the solution of the three-dimensional convection-diffusion equation. A higher order upwind scheme is used for the convective terms of the convection-diffusion equation, to minimise the numerical diffusion. The validity of the numerical model is verified through five test problems, whose exact solutions are known. 相似文献
107.
Ground water is an excellent solvent, which dissolves chemicals ions as it moves through rocks and subsurface soil. This leads
to more mineralization in groundwater than surface water. The objective of the present study is to examine the groundwater
quality of the Paravanar River Sub-basin, Cuddalore district, Tamil Nadu, India. The Electrical Conductivity (EC) values ranges
between 160 and 2,580 μS/cm in groundwater samples. The highest value of 2,580 μS/cm was recorded in wells near the coast.
pH values ranges from 7.2 to 8.6. NNE and southern part of the study area has low pH values, rest of the area represents the
alkaline nature of groundwater. In south eastern part of the study area alkali values are slightly higher but it is within
WHO’s tolerable limits. The spatial distribution of chloride concentration shows that Meenatchipettai, Vazhisothani palayam
and Allapakkam represents maximum Cl2 concentration of 527, 320 and 374 ppm, which is above ISI drinking standards of 250 ppm. Increase in isochlore is observed
from the coast up to the Neyveli lignite mine. Nitrate concentration of groundwater samples ranges from 0.1 mg/l to 64 mg/l.
As most of the study area is cultivated, fertilizers used for agriculture may be the cause for increase in concentration of
nitrates in few concentrated locations. 相似文献
108.
Limitations Of The Tangent Plane Approximation For Wide-field Imaging Using The Mauritius Radio Telescope 总被引:1,自引:0,他引:1
The Mauritius Radio Telescope (MRT) is a Fourier synthesis, non-coplanar T array. The primary objective of the telescope is
to survey the southern sky at 151.5 MHz in the declination range -70° to -10°. Due to non-coplanarity, wide-field imaging and deconvolution of wide field images made using MRT are challenging problems
in applications of radio interferometric techniques. This paper discusses the usefulness and limitations of the tangent plane
approximation in transforming the measured visibilities to wide field images and in estimating the point spread function (PSF)
required for the deconvolution.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
109.
N Ramesh Babu M Venkateshwarlu Ravi Shankar E Nagaraju V Parashuramulu 《Journal of Earth System Science》2018,127(1):3
Here we report new paleomagnetic results and precise paleopole position of the extensional study on \(\sim \)2367 Ma mafic giant radiating dyke swarm in the Dharwar craton, southern India. We have sampled 29 sites on 12 dykes from NE–SW Karimnagar–Hyderabad dykes and Dhone–Gooty sector dykes, eastern Dharwar craton to provide unambiguous paleomagnetism evidence on the spectacular radiating dyke swarm and thereby strengthening the presence of single magmatic event at \(\sim \)2367 Ma. A total of 158 samples were subjected to detailed alternating field and thermal demagnetization techniques and the results are presented here along with previously reported data on the same dyke swarm. The remanent magnetic directions are showing two components, viz., seven sites representing four dykes show component (A) with mean declination of \(94{{}^{\circ }}\) and mean inclination of \(-\,70{{}^{\circ }}\) (\(\hbox {k}=87\), \(\upalpha _{95}=10{{}^{\circ }}\)) and corresponding paleopole at \(16{{}^{\circ }}\hbox {N}\), \(41{{}^{\circ }}\hbox {E}\) (\(\hbox {dp}=15{{}^{\circ }}\) and \(\hbox {dm}=17{{}^{\circ }}\)) and 22 sites representing 8 dykes yielded a component (B) with mean declination of \(41{{}^{\circ }}\) and mean inclination of \(-\,21{{}^{\circ }}\) (\(\hbox {k}=41\), \(\upalpha _{95}=9{{}^{\circ }}\)) with a paleopole at \(41{{}^{\circ }}\hbox {N}\), \(200{{}^{\circ }}\hbox {E}\) (\(\hbox {dp}=5{{}^{\circ }}\) and \(\hbox {dm}=10{{}^{\circ }}\)). Component (A) results are similar to the previously reported directions from the \(\sim \)2367 Ma dyke swarm, which have been confirmed fairly reliably to be of primary origin. The component (B) directions appear to be strongly overprinted by the 2080 Ma event. The grand mean for the primary component (A) combined with earlier reported studies gives mean declination of \(97{{}^{\circ }}\) and mean inclination of \(-\,79{{}^{\circ }}\) (\(\hbox {k}=55\), \(\upalpha _{95}=3{{}^{\circ }}\)) with a paleopole at \(15{{}^{\circ }}\hbox {N}\), \(57{{}^{\circ }}\hbox {E}\) (\(\hbox {dp}=5{{}^{\circ }}\), \(\hbox {dm}=6{{}^{\circ }}\)). Paleogeographical position for the Dharwar craton at \(\sim \)2367 Ma suggests that there may be a chance to possible spatial link between Dharwar dykes of Dharwar craton (India), Widgemooltha and Erayinia dykes of Yilgarn craton (Australia), Sebanga Poort Dykes of Zimbabwe craton (Africa) and Karelian dykes of Kola-Karelia craton (Baltica Shield). 相似文献
110.
Multichannel seismic reflection data from the continental margin of western India suggest the potential presence of fluid
expulsion features, which may or may not be associated with gas hydrates. No typical bottom simulating reflector was observed
on the reflection seismic section. As a result we look for other evidence in seismic sections in a small corridor of the western
continental margin of India in order to establish the presence of gas hydrates. We study features including venting through
the seafloor, pockmarks, sea floor collapse, faults acting as migration paths for fluid flow, transparent gas-charged sediment,
reduction in amplitude strength, diapirism and mud-volcano. Presence of all these gas-escape features on a seismic section
implies the probable presence of methane within the zone of hydrate stability field. 相似文献