Swelter in the city: Urban greenery and its effects on temperature in Guwahati,India     

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   

Investigation of Soil Suction Characteristics Induced by the Degradation of Organic Matter     

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   

Galaxy evolution in Hickson compact groups: the role of ram-pressure stripping and strangulation     

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   

Photosynthetic activity and antioxidative response of seagrass Thalassia hemprichii to trace metal stress   总被引：1，自引：0，他引：1  

LI Lei  HUANG Xiaoping  Devajit Borthakur  NI Hui 《海洋学报(英文版)》2012,31(3):98-108

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=F_m'), 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=F_m', chlorophyll and carotenoid were significantly low during prolonged Cu exposure. Besides, ΔF=F_m' 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