A preliminary one-dimensional crustal velocity model for Himachal Pradesh,India     

Mahesh Prasad Parija  Sushil Kumar  Shubhasmita Biswal  Narendra Kumar  Saurabh Kumar Mishra 《Journal of Seismology》2016,20(1):305-318

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The Lohawat howardite: Mineralogy,chemistry and cosmogenic effects     

M. S. Sisodia  A. D. Shukla  K. M. Suthar  R. R. Mahajan  S. V. S. Murty  P. N. Shukla  N. Bhandari  R. Natarajan 《Meteoritics & planetary science》2001,36(11):1457-1466

Abstract— The Lohawat meteorite is a texturally heterogeneous breccia having a variety of mineral and lithic fragments. Among mineral fragments, pyroxenes show a wide range of composition (Wo_0.011–0.17En_0.37–0.78Fs_0.21–0.60) whereas plagioclase is anorthitic (An_0.92Ab_0.07Or_0.007). Abundant rounded “chondrule‐like” objects ranging in size up to ～7 mm, some with concentric layering, have been observed. Petrographic features, trace element composition and rare earth element patterns show the presence of eucritic and diogenitic components confirming that it is a typical howardite. Cosmogenic tracks, rare gases (He, Ne, and Ar) and radionuclides (²²Na and ²⁶Al) were measured. Track density in olivine and plagioclase varies between 0.7 to 6 times 10⁶/cm². ³⁸Ar exposure age is estimated to be ～110 Ma, being the highest among howardites. The track production rates correspond to ablation of 9 to 15 cm, implying a radius for its preatmospheric size of ～27 cm. ²²Na/²⁶Al ～ 1, as expected from the production models and solar modulation of galactic cosmic‐ray fluxes before its fall, suggesting that the meteoroid did not undergo any fragmentation during the past ～2 Ma in interplanetary space. The radiogenic age based on K‐Ar method is 4.3 Ga while the U‐Th‐⁴He age is 3.3 Ga indicating partial loss of He.  相似文献   

Cosmic ray irradiation patterns of Luna 16 and 20 soils: Implications to lunar surface dynamic processes     

Narendra Bhandari  Jitendra Goswami  Devendra Lal 《Earth and Planetary Science Letters》1973,20(3):372-380

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Mineralogy and trace element chemistry of the siliceous earth of barmer basin, Rajasthan: Evidence for a volcanic origin     

M. S. Sisodia  U. K. Singh  G. Lashkari  P. N. Shukla  A. D. Shukla  N. Bhandari 《Journal of Earth System Science》2005,114(2):111-124

We report the presence of a 3–5 cm thick loose fragmental layer in the Siliceous Earth at Matti ka Gol in the Barmer basin of Rajasthan. Petrographic, chemical and mineralogical study reveals the presence of abundant volcanic debris such as glass shards, agglutinates, hollow spheroids, kinked biotites, feldspars showing oscillatory zoning, olivines, ilmenite and native iron. The presence of similar particles in the whole section suggests that the Siliceous Earth is a volcanic ash. Stratigraphic correlation, palynological and microvertebrate data suggest that the Siliceous Earth may have deposited over a short span of time during the Upper Cretaceous to Lower Palaeocene. In view of the possibility that this section may contain K/T impact debris, we looked for grains having impact signatures. Some patches of the Siliceous Earth of Bariyara show the presence of Ni-rich (> 0.5%) vesicular glasses, sanidine spherules, magnesioferrite crystals, soot, etc., but because of their low abundance, it is not possible to establish if they are volcanic, micrometeorite ablation products or a part of the K/T impact ejecta.  相似文献   

High energy X-γ ray spectrometer on the Chandrayaan-1 mission to the Moon     

J. N. Goswami  D. Banerjee  N. Bhandari  M. Shanmugam  Y. B. Acharya  D. V. Subhedar  M. R. Sharma  C. N. Umapathy  P. Sreekumar  M. Sudhakar  L. Abraham  P. C. Agrawal 《Journal of Earth System Science》2005,114(6):733-738

The Chandrayaan-1 mission to the Moon scheduled for launch in late 2007 will include a high energy X-ray spectrometer (HEX) for detection of naturally occurring emissions from the lunar surface due to radioactive decay of the²³⁸U and²³²Th series nuclides in the energy region 20–250 keV. The primary science objective is to study the transport of volatiles on the lunar surface by detection of the 46.5 keV line from radioactive²¹⁰Pb, a decay product of the gaseous²²²Rn, both of which are members of the²³⁸U decay series. Mapping of U and Th concentration over the lunar surface, particularly in the polar and U-Th rich regions will also be attempted through detection of prominent lines from the U and Th decay series in the above energy range. The low signal strengths of these emissions require a detector with high sensitivity and good energy resolution. Pixelated Cadmium-Zinc-Telluride (CZT) array detectors having these characteristics will be used in this experiment. Here we describe the science considerations that led to this experiment, anticipated flux and background (lunar continuum), the choice of detectors, the proposed payload configuration and plans for its realization  相似文献   

Composition and Regeneration of Trees in the Community Forests of Lamjung District,Nepal     

Tilak Babu CHAPAGAI  Dipak KHADKA  Dinesh Raj BHUJU  Narendra Raj KHANAL  SHI Shi  CUI Dafang 《资源与生态学报(英文版)》2021,12(5):658-668

The community forest program in Nepal is one of the successful conservation initiatives. Tree species in a forest ecosystem have a fundamental role in maintaining the vegetation structure, complexity, and heterogeneity. This study analyzes the composition and regeneration of tree species in five community forests (CFs) of the sub-tropical region, Lamjung district, Nepal for preparing baseline data for long-term research projects and helps the community to manage their CFs scientifically. Tree species data were generated by stratified random sampling using 35 quadrate plots (size: 20 m x 20 m). The density of adult trees in the forests ranged from 575 Ind ha ^-1 (Tilahar CF) to 1196 Ind/ha (Deurali Thadopakha CF). The sapling ranged from 2533 Ind ha ^-1 (Tilahar CF) to 4000 Ind ha ^-1 (Thuliban CF) and seedling from 19583 Ind ha ^-1 (Tilahar CF) to 37500 Ind ha ^-1 (Thuliban CF). Similarly, the adult tree basal area varied from 28.34 m ² ha ^-1 (Tilahar CF) to 49 m ²ha ^-1 (Deurali CF). The adult tree diversity index (Shannon-Weiner’s H) also ranged from 1.08 (Thuliban CF) to 1.88 (Tilahar CF). The tree species such as Sapium insigne, Ficus benghalensis, Lagerstroemia parviflore, Albizia sp. and Pinus roxburghii were weak regeneration. In general, the forests have good regeneration status except for Tilahar Community Forest, but based on the DBH size class distribution diagram, there is no sustainable regeneration. Among the five community forests the DBH size of adults was significantly different, and the DBH of Deurali Thadopakha was the lowest. But only few species have good regeneration and most of the species have weak, poor to no regeneration. The dominancy of fewer species like Shorea robusta, Castanopsis indica, and Schima wallichii accordingly maintain the overall regeneration of tree of CFs, so further plantation needs to be done inside the CF by triage accordingly those species whose regeneration has poor.  相似文献   

On the exact evaluation of displacements within a semi-infinite solid due to a buried line source     

Satyesh K Bhandari  Ramesh Chander 《Journal of Earth System Science》1984,93(1):37-45

Garvin’s variant of the Cagniard technique has been used to evaluate exactly the displacements at points within a homogeneous, isotropic, perfectly elastic, solid half space due to a buried explosive line source. The disturbance at any given time is confined to a region bounded by the free surface of the half space and theP wave front within it. The disturbance associated with the Rayleigh pulse affects a smaller region bounded by the free surface and the PP wave front.  相似文献   

Isotopic and related studies of Antarctic ice samples     

N Bhandari  S K Bhattacharya  V N Nijampurkar  D Sengupta  V G Shah  A K Singhvi  P N Shukla  K M Suthar  C P Vohra 《Journal of Earth System Science》1984,93(2):135-140

The ice samples obtained from Dakshin Gangotri, Antarctica show the presence of nuclear debris, attributed mainly to French nuclear explosions. Cosmogenic⁷Be occurs at levels of 30 dpm/L. The vertical profile ofδD in 6 m long drill core ranges between ?130 and ?180‰ compared to Standard Mean Ocean Water (SMOW). No systematic change with depth is seen. Small amounts of dust obtained by filtering melt water show presence of metallic spherules. Absence of elements characteristic of meteoritic or cometary debris suggests that most of them are of volcanic or industrial origin.  相似文献   

Assessment of urban heat island effect for different land use–land cover from micrometeorological measurements and remote sensing data for megacity Delhi     

Manju Mohan  Yukihiro Kikegawa  B. R. Gurjar  Shweta Bhati  Narendra Reddy Kolli 《Theoretical and Applied Climatology》2013,112(3-4):647-658

Urban heat island intensities (UHI) have been assessed based on in situ measurements and satellite-derived observations for the megacity Delhi during a selected period in March 2010. A network of micrometeorological observational stations was set up across the city. Site selection for stations was based on dominant land use–land cover (LULC) classification. Observed UHI intensities could be classified into high, medium and low categories which overall correlated well with the LULC categories viz. dense built-up, medium dense built-up and green/open areas, respectively. Dense urban areas and highly commercial areas were observed to have highest UHI with maximum hourly magnitude peaking up to 10.7 °C and average daily maximum UHI reaching 8.3 °C. UHI obtained in the study was also compared with satellite-derived land surface temperatures (LST). UHI based on in situ ambient temperatures and satellite-derived land surface temperatures show reasonable comparison during nighttime in terms of UHI magnitude and hotspots. However, the relation was found to be poor during daytime. Further, MODIS-derived LSTs showed overestimation during daytime and underestimation during nighttime when compared with in situ skin temperature measurements. Impact of LULC was also reflected in the difference between ambient temperature and skin temperature at the observation stations as built-up canopies reported largest gradient between air and skin temperature. Also, a comparison of intra-city spatial temperature variations based UHI vis-à-vis a reference rural site temperature-based UHI indicated that UHI can be computed with respect to the station measuring lowest temperature within the urban area in the absence of a reference station in the rural area close to the study area. Comparison with maximum and average UHI of other cities of the world revealed that UHI in Delhi is comparable to other major cities of the world such as London, Tokyo and Beijing and calls for mitigation action plans.  相似文献   

http://www.sciencedirect.com/science/article/pii/S1674987113001084     

V.Agarwal  G.Parthasarathy  M.S.Sisodia  N.Bhandari 《地学前缘(英文版)》2014,5(3):413-417

We report here for the first time the composition and mineralogical studies on a new meteorite,which fell in Dhayala ki Chappar(24°58'N,73°48'27"E) 5 km NW of Nathdwara in south Rajasthan,India,on Dec.25 th,2012.Mineralogical and compositional studies were carried out on a representative piece of the Nathdwara meteorite sample.The mineralogical composition of the meteorite has been found to be olivine(42-45 vol.%),feldspar(10-15 vol.%),orthopyroxene(23-25 vol.%),troilite(6-8 vol.%),and titanium bearing minerals(6-8 vol.%).Our investigations show that the Nathdwara meteorite belongs to H6 group of ordinary chondrites.  相似文献