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Dubey Anant Aishwarya Borthakur Annesh Ravi K. 《Geotechnical and Geological Engineering》2022,40(4):2371-2378
Geotechnical and Geological Engineering - Total soil suction is considered to be the accumulative influence of matric and osmotic suction, assuming that the soil is biologically inert. However,... 相似文献
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Monjit Borthakur Anup Saikia Kiran Sharma 《Singapore journal of tropical geography》2020,41(3):341-366
Changing urban landscape with multistoried high rises, roads and pavements is continuously reducing urban green space. These structures result in high surface temperature variation within cities. To explore the relationship between surface temperature and normalized difference vegetation index (NDVI), this study estimates two models—geographically weighted regression (GWR) and a fixed effect panel data model in relation to the Guwahati Metropolitan Area (GMA), a secondary city in north east India. The results indicate the superiority of GWR regression in presence of spatial dependence. Panel data analysis shows that the densely populated urban areas in the GMA with less than 10 per cent greenery are 1°C warmer than the sub-urban areas with 50 per cent greenery. 相似文献
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Jesper Rasmussen † Trevor J. Ponman Lourdes Verdes-Montenegro Min S. Yun Sanchayeeta Borthakur 《Monthly notices of the Royal Astronomical Society》2008,388(3):1245-1264
Galaxies in compact groups tend to be deficient in neutral hydrogen compared to isolated galaxies of similar optical properties. In order to investigate the role played by a hot intragroup medium (IGM) for the removal and destruction of H i in these systems, we have performed a Chandra and XMM–Newton study of eight of the most H i deficient Hickson compact groups. Diffuse X-ray emission associated with an IGM is detected in four of the groups, suggesting that galaxy–IGM interactions are not the dominant mechanism driving cold gas out of the group members. No clear evidence is seen for any of the members being currently stripped of any hot gas, nor for galaxies to show enhanced nuclear X-ray activity in the X-ray bright or most H i deficient groups. Combining the inferred IGM distributions with analytical models of representative disc galaxies orbiting within each group, we estimate the H i mass-loss due to ram-pressure and viscous stripping. While these processes are generally insufficient to explain observed H i deficiencies, they could still be important for H i removal in the X-ray bright groups, potentially removing more than half of the interstellar medium in the X-ray bright HCG 97. Ram pressure may also have facilitated strangulation through the removal of galactic coronal gas. In X-ray undetected groups, tidal interactions could be playing a prominent role, but it remains an open question whether they can fully account for the observed H i deficiencies. 相似文献
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Photosynthetic activity and antioxidative response of seagrass Thalassia hemprichii to trace metal stress 总被引：1，自引：0，他引：1
This study concerned the accumulation of trace metals in tissues of seagrass (Thalassia hemprichii) exposed to various concentrations of Zn2++, Cd2++, Pb2++ and Cu2++ for 10 d, and the effect of excessive metals on quantum yield (ΔF=Fm'), photosynthetic pigments and antioxidative enzymes like superoxide dismutase (SOD), guaiacol peroxidase (POD) were also examined. Cadmium was the most highly accumulated metal. Meanwhile, high metals levels led to a remarkable breakdown of photosynthetic parameters. Especially, ΔF=Fm', chlorophyll and carotenoid were significantly low during prolonged Cu exposure. Besides, ΔF=Fm' was more severely depressed by Cu and Zn than Pb and Cd. However, T. hemprichii had positive response by increasing the activity of SOD and POD. The results indicate that T. hemprichii is the most sensitive to Cu, and the antioxidative protection mechanisms of T. hemprichii are more efficiently activated to avoid damage of Zn, Cd and Pb stress. Finally, due to the high Cd-accumulation and strong Cd-tolerance capacity, T. hemprichii can be used for phytoremediation in Cd-contaminated areas. 相似文献
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Crustal thickness and Poisson’s ratios are estimated across the northwest (NW) Himalaya and eastern Ladakh applying H-k stacking method on receiver functions of teleseismic earthquakes recorded at 16 broadband seismological stations. The results show significant lateral variation of crustal thickness from the Lesser and Higher Himalaya (～50 km thick) to Ladakh (～80 km thick) through the Indus Tsangpo Suture Zone (ITSZ). The Indian Moho is continuously traceable across the ITSZ which is consistent with the underthrusting of the Indian plate beyond the surface collision boundary. The estimated Poisson’s ratios in the Lesser and Higher Himalaya are low (0.249–0.253), suggesting felsic composition of the crust. The Poisson’s ratio is intermediate in the Tethyan Himalaya (0.269–0.273) and high beneath Ladakh (0.280–0.303), indicating the effect of aqueous fluid/partial melt present in the crust. 相似文献
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The opening of cracks and influx of fluids in the dilatancy zone of impending earthquake is expected to induce short-term changes in physical/chemical/hydrological properties during earthquake build-up cycle, which should be reflected in time-varying geophysical fields. With this rationale, eleven geophysical parameters are being recorded in continuous mode at the Multi-Parametric Geophysical Observatory (MPGO), in Ghuttu, Garhwal Himalaya, for earthquake precursory research. The critical analysis of various geophysical time series indicates anomalous behavior at few occasions; however, the data is also influenced by many external forces. These external influences are the major deterrent for the isolation of precursory signals. The recent work is focused on the data adoptive techniques to estimate and eliminate effects of solar-terrestrial and hydrological/environmental factors for delimiting the data to identify short-term precursors. Although any significant earthquake is not reported close to the observatory, some weak precursory signals and coseismic changes have been identified in few parameters related to the occurrence of moderate and strong earthquakes. 相似文献
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Saurabh Baruah Devajit Hazarika Naba K. Gogoi P. Solomon Raju 《Journal of Earth System Science》2007,116(1):37-47
Microearthquake spectra from Jubilee Hills, Hyderabad are analyzed to observe the effect of attenuation and site on these
spectra. The ratios of spectral amplitudes at lower and higher frequency are measured for three different stations at varying
epicentral distances to estimate Q value for both P-and S-wave in near and sub-surface layer. Average estimates of Qp and
Qs are 235 and 278 respectively. Value of Qs/Qp larger than 1.0 suggests dry crust for most of the Jubilee Hills region. The
near-surface low Qp and Qs for 0 km to 0.9 km depth coincide with the soil layer, top and semi-weathered and highly fractured
zone. In contrast, at a shallower depth beneath the Jubilee Hills area, Hyderabad, we obtain high Qp and Qs zone, which corresponds
to the dense and high velocity rocks of the region. The varying corner frequencies for these spectra are inferred to be characteristics
of site. Comparisons of disparity in spectral content with reference to hard rock site conclude that lithology of the northwest
part of Jubilee Hills area amplify about twice the incoming seismic signal, as compared to the southern part best outlined
at 8 to 10 Hz only. 相似文献
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Attenuation of coda waves in the Northeastern Region of India 总被引：1，自引：0，他引：1
Coda wave attenuation quality factor Qc is estimated in the northeastern region of India using 45 local earthquakes recorded
by regional seismic network. The quality factor Qc was estimated using the single backscattering model modified by Sato (J
Phys Earth 25:27–41, 1977), in the frequency range 1–18 Hz. The attenuation and frequency dependence for different paths and the correlation of the
results with geotectonics of the region are described in this paper. A total of 3,890 Qc measurements covering 187 varying
paths are made for different lapse time window of 20, 30, 40, 50, 60, 70, 80, and 90 s in coda wave. The magnitudes of the
analyzed events range from 1.2 to 3.9 and focal depths range between 7 and 38 km. The source–receiver distances of the selected
events range between 16 and 270 km. For 30-s duration, the mean values of the estimated Qc vary from 50 ± 12 (at 1 Hz) to
2,078 ± 211(at 18 Hz) for the Arunachal Himalaya, 49 ± 14 (at 1 Hz) to 2,466 ± 197 (at 18 Hz) for the Indo-Burman, and 45
± 13 (at 1 Hz) to 2,069 ± 198 (at 18 Hz) for Shillong group of earthquakes. It is observed that Qc increases with frequency
portraying an average attenuation relation for the region. Moreover, the pattern of Qc − 1 with frequency is analogous to the estimates obtained in other tectonic areas in the world, except with the observation that
the Qc − 1 is much higher at 1 Hz for the northeastern region. The Qc − 1 is about 10 − 1.8 at 1 Hz and decreases to about 10 − 3.6 at 18 Hz indicating clear frequency dependence. Pertaining to the spatial distribution of Qc values, Mikir Hills and western
part of Shillong Plateau are characterized by lower attenuation. 相似文献
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Kumar Naresh Kumar Parveen Chauhan Vishal Hazarika Devajit 《International Journal of Earth Sciences》2017,106(7):2371-2386
International Journal of Earth Sciences - Strong-motion records of recent Gorkha Nepal earthquake (M w 7.8), its strong aftershocks and seismic events of Hindu kush region have been analysed for... 相似文献