5 results on '"Kumar, Amit"'
Search Results
2. Along‐strike variation in the shear wave crustal structure of the NE Himalayan and Indo‐Burmese arc: Evidence based on surface wave dispersion analysis.
- Author
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Chanu, Nongmaithem Menaka, Kumar, Naresh, Kumar, Amit, Mukhopadhyay, Sagarika, and Babu, Vivek G.
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SHEAR waves , *PARTICLE size determination , *WAVE analysis , *RAYLEIGH waves , *FRICTION velocity , *SEISMIC event location , *SEISMIC anisotropy - Abstract
Surface wave dispersion data is used to infer the shear wave velocity structure variation in the north‐east Himalaya and Indo‐Burmese arc regions. We have used 25 earthquakes data from four groups with a magnitude range of 5.0–6.7, epicentral distance range 368–800 km, and focal depth less than 50 km. Ray paths from the earthquake location to the seismic station are transversely passing different geotectonic units of the Himalayas, Indo‐Gangetic plains, and Indo‐Burma collision zones. The weighted average dispersion curve and the path averaged shear wave velocity models are computed for the four groups located at different azimuths around Shillong seismic station. Non‐linear least‐square inversion is performed to obtain the shear wave velocity structure of the crust and uppermost mantle from joint inversion of Rayleigh and Love waves group velocities. Subsequently, Rayleigh and Love waves group velocities are inverted separately to obtain vertical and horizontal components of S‐wave velocity. Next, using these components anisotropy coefficient values at different depths for each path are also estimated. A high variation of dispersion curves and the shear wave velocity models from one group to another indicates that the region is geotectonically very complex. An approximately 80 km‐thick zone beneath the study region has shear wave velocity as low as 1.7 km/s in the uppermost crust in the southern part and ~4.7 km in the uppermost mantle beneath the Eastern Himalayan Syntaxis (EHS). Inferred velocity is also lower than that of PREM and AK135 global models with a much thicker crust beneath the study region. Radial anisotropy varies even within the northern part from the Indo‐Eurasian collision zone to EHS and northern to southern Indo‐Burma ranges. Anisotropy is comparatively stronger in the deeper part below ~40 km for the three paths, except for the EHS, where the result is contrary. [ABSTRACT FROM AUTHOR]
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- 2022
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3. Causes and consequences of Rishiganga flash flood, Nanda Devi Biosphere Reserve, central Himalaya, India.
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Mehta, Manish, Kumar, Vinit, Sain, Kalachand, Tiwari, Sameer K., Kumar, Amit, and Verma, Akshaya
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BIOSPHERE reserves , *SLURRY - Abstract
On 7 February 2021 at 10:30 am, a huge amount of slurry material flooded the Rishiganga catchment, resulting in excessive flow along the valley. The main cause of this flood was the dislocation of a huge rock mass approximately 540 m wide and 720 m long from the main rock body, which slipped down towards the Raunthi Gadera valley floor, causing massive devastation in the areas such as Raini, Tapovan, and Vishnuprayag. This event was not expected and was the first event in history when a flash flood occurred in winter. In this study, we tried to answer two major questions which are not been explained so far that are related to this disaster. These questions are (i) why did this event occur in winters? (ii) where did so much debris and water come from?. This study clearly answers these questions based on field observations. [ABSTRACT FROM AUTHOR]
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- 2021
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4. Agroforestry systems in the mid-hills of the north-western Himalaya: A sustainable pathway to improved soil health and climate resilience.
- Author
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Verma, Tarun, Bhardwaj, D.R., Sharma, Uday, Sharma, Prashant, Kumar, Dhirender, and Kumar, Amit
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SUSTAINABLE agriculture , *CARBON dioxide mitigation , *HILL farming , *BAMBOO , *FRUIT trees , *CROPPING systems , *AGROFORESTRY - Abstract
Identifying the new tree crop combinations plays an important function in transforming the low input agriculture into land units with high economic returns, increasing carbon (C) sink and nutrients storage capacity, and acting as a panacea to achieve Sustainability Development Goals (SDGs). The present study aims to evaluate various tree-crop combinations for (i) biomass production, (ii) carbon accumulation, and (iii) soil nutrient enrichment of traditional and commercially evolved eight agroforestry systems (AFSs), including agri-silvi-horticulture system, agri-silviculture system, silvi-pasture, fruit tree, fodder tree, bamboo, melia and poplar based AFSs with sole cropping system in the mid-hill zone of the north-western Himalaya. The results demonstrated that poplar based AFS accumulated a higher amount of biomass (130.87 Mg ha−1) and carbon (65.44 Mg ha−1) closely followed by melia-based AFS. The C stored in leaf litter was higher (0.66 Mg ha−1) in poplar-based AFS, however, soil C stock was maximum (114.69 Mg ha−1) under bamboo-based AFS. Overall, the Melia based AFS exhibited a higher rate of carbon dioxide mitigation (19.30 Mg ha−1 yr−1) and C-sequestration (5.26 Mg ha−1 yr−1) than other studied AFSs. Moreover, soil macro-nutrients (available N, P, K, S and Ca) were maximum under bamboo-based AFS, on the other hand, the fruit-based AFS had the higher concentrations of micro-nutrients i.e., Cu (3.05), Fe (31.10 mg g−1) and Mn (17.31 mg g−1). The soil microbial counts were higher in poplar-based AFS, whereas, the soil quality index improved significantly under bamboo based and fruit tree based AFSs. Hence, it can be concluded that the experimentally evolved AFSs represent an effective approach for boosting C-sequestration, soil fertility, regenerating the soil and sustainability of hill agriculture in the north-western Himalayas over traditional AFSs and sole cropping. • Agroforestry systems (AFSs) contribute significantly to biomass production & carbon storage. • Poplar- and bamboo based AFSs accumulated maximum biomass & soil C stock, respectively. • Melia based AFSs exhibited highest rate of C-sequestration. • Bamboo based AFSs maintained the highest soil quality index. [ABSTRACT FROM AUTHOR]
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- 2023
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5. Isolation and anticancer activity evaluation of rare Bisaryl anthraquinone antibiotics from novel Streptomyces sp. strain of NW Himalayan region.
- Author
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Manhas, Ravi Singh, Ahmad, Syed Mudabir, Mir, Khalid Bashir, Ahmed, Ajaz, Sharma, Snigdha, Manhas, Diksha, Tiwari, Harshita, Kumar, Amit, Nargotra, Amit, Nandi, Utpal, Mukherjee, Debaraj, Goswami, Anindya, and Chaubey, Asha
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ANTINEOPLASTIC agents , *STREPTOMYCES , *ANTHRAQUINONES , *ANTIBIOTICS , *IN vivo studies - Abstract
Biosynthesis of bisaryl preanthraquinone antibiotics by various microorganisms differs in monomeric subunits as well as their dimerization positions leading to different configurations. The present study relates to the production of rare bisaryl anthraquinone antibiotics by a new Streptomyces strain isolated from Shivalik region of NW Himalayas. In vitro anticancer and anti-migratory effects of Setomimycin (9,9′ bisanthraquinone antibiotic) was seen with a significant reduction in the expression of both MEK as well as ERK pathways in a dose dependent manner at 6.5 μM & 8 μM concentration in HCT-116 and 5.5 μM & 7 μM concentration in MCF-7 cells. In vivo studies in aggressive orthotopic mouse mammary carcinoma model (4T1) demonstrated about 76% reduction of primary tumor weight and 90.5% reduction in the tumor volume within two weeks. In vivo pharmacokinetics study of setomimycin revealed that it can be rapidly absorbed with an adequate plasma exposure and half-life which can be linked to its in vivo efficacy. [Display omitted] • Setomimycin, a rare bisaryl anthraquinones isolated from novel Streptomyces sp. strain from NW Himalayas. • An optima increase of par-4 was observed at 8 μM in HCT-116 cells and 7 μM in MCF-7 cells. • In-vivo studies in 4T1 mice model resulted in 90.5% reduction in the tumor volume within two weeks. • Setomimycin could absorbe rapidly (T max < 20 min) with a maximum plasma concentration level (C max >1 μM). [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
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