Elemental abundance measurements in low-redshift damped Lyman α absorbers     

Joseph D. Meiring  Varsha P. Kulkarni  Pushpa Khare  Jill Bechtold  Donald G. York  Jun Cui  James T. Lauroesch  Arlin P. S. Crotts  Osamu Nakamura 《Monthly notices of the Royal Astronomical Society》2006,370(1):43-62

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Laboratory experiments of Titan tholin formed in cold plasma at various pressures: implications for nitrogen-containing polycyclic aromatic compounds in Titan haze     

Hiroshi Imanaka  Bishun N. Khare  Emma L.O. Bakes  Dale P. Cruikshank  Takafumi Matsui 《Icarus》2004,168(2):344-366

Titan, the largest satellite of Saturn, has a thick nitrogen/methane atmosphere with a thick global organic haze. A laboratory analogue of Titan's haze, called tholin, was formed in an inductively coupled plasma from nitrogen/methane=90/10 gas mixture at various pressures ranging from 13 to 2300 Pa. Chemical and optical properties of the resulting tholin depend on the deposition pressure in cold plasma. Structural analyses by IR and UV/VIS spectroscopy, microprobe laser desorption/ionization mass spectrometry, and Raman spectroscopy suggest that larger amounts of aromatic ring structures with larger cluster size are formed at lower pressures (13 and 26 Pa) than at higher pressures (160 and 2300 Pa). Nitrogen is more likely to incorporate into carbon networks in tholins formed at lower pressures, while nitrogen is bonded as terminal groups at higher pressures. Elemental analysis reveals that the carbon/nitrogen ratio in tholins increases from 1.5-2 at lower pressures to 3 at 2300 Pa. The increase in the aromatic compounds and the decrease in C/N ratio in tholin formed at low pressures indicate the presence of the nitrogen-containing polycyclic aromatic compounds in tholin formed at low pressures. Tholin formed at high pressure (2300 Pa) consists of a polymer-like branched chain structure terminated with CH₃, NH₂, and CN with few aromatic compounds. Reddish-brown tholin films formed at low pressures (13-26 Pa) shows stronger absorptions (almost 10 times larger k-value) in the UV/VIS range than the yellowish tholin films formed at high pressures (160 and 2300 Pa). The tholins formed at low pressures may be better representations of Titan's haze than those formed at high pressures, because the optical properties of tholin formed at low pressures agree well with that of Khare et al. (1984a, Icarus 60, 127-137), which have been shown to account for Titan's observed geometric albedo. Thus, the nitrogen-containing polycyclic aromatic compounds we find in tholin formed at low pressure may be present in Titan's haze. These aromatic compounds may have a significant influence on the thermal structure and complex organic chemistry in Titan's atmosphere, because they are efficient absorbers of UV radiation and efficient charge exchange intermediaries. Our results also indicate that the haze layers at various altitudes might have different chemical and optical properties.  相似文献   

Pan Sharpening for Hyper Spectral Imagery Using Spectral Mixing-Based Color Preservation Model     

Munmun Baisantry  Ayushi Khare 《Journal of the Indian Society of Remote Sensing》2017,45(5):743-748

With nanometric spectral resolution and number of bands as high as 220, Hyper spectral sensors like Hyperion and AVIRIS are gaining wide appreciation. Narrow, continuous wavelength of bands upon a vast spectrum of electromagnetic wavelength enables better precision in identification of materials by distinguishing between their unique spectral signatures. However, their poor spatial resolution is a major impediment in realising the full potential of hyperspectral imaging. Efforts are being made worldwide to improve the spatial resolution of hyperspectral imagery by fusing them with registered panchromatic imagery of higher resolution. However, most of the conventional methods fail to preserve the spectral fidelity of the fused images due to severe color distortion. Here, we propose an efficient paradigm to sharpen hyperspectral imagery with high spatial information content and minimal color distortion using color normalization by Lαβ and intensity image generation using Spectral Mixture Analysis. Quantitative assessment indices have been calculated to prove that our method is superior in terms of minimization of color distortion and maximization of spatial details as compared to other methods.  相似文献   

Signatures of different water masses in δ<Superscript>18</Superscript>O values,relative abundance of <Emphasis Type="Italic">G. Bulloides</Emphasis> and total planktonic foraminiferal assemblage across the Indian Ocean sector of the southern ocean: Initial results     

N. Khare  S. K. Chaturvedi 《Oceanology》2012,52(3):372-379

Nineteen surface sediment samples, collected onboard ORV Sagar Kanya during the 199C and 200th (the pilot expedition to Southern Ocean) cruises along a north-south transect between 1.92° S to 55.01° S latitude and 67.88° E and 44.89° E longitude, were studied for total planktonic foraminiferal assemblage, relative abundance and the oxygen isotopic values of the indicator planktic species Globigerina bulloides. These profiles were compared with the latitudinal variations in the average salinity and nutrient (phosphate) contents of the top 100 meters water column. The initial results have traced the signatures of salinity linked variations of different water masses in the study region. The influence of Australian Mediterranean Water (AAMW) has been noticed in the present dataset.  相似文献   

Extinction and scattering by several types of silicate sphere of radius 0.05–1.0μm,for the wavelength range 0.21–50μm     

G. E. Bromage  K. Nandy  B. N. Khare 《Astrophysics and Space Science》1973,20(1):213-224

The exact calculation of scattering and absorption by various sub-micron sized silicate spheres is presented here, using accurately determined optical constants in the wavelength range from 50 m to 0.21 m. The extinction features near 10 m and 20 m for various samples are discussed. It is found that the ratio of peak extinction at 20 m to that at 10 m is constant for small particles up tor=0.4 m, but is less for particles of radius 1 m. The ratio of maximum extinction in the ultraviolet to that at 10 m decreases with increasing particle size.  相似文献   

Organic solids produced by electrical discharge in reducing atmospheres: Tholin molecular analysis     

B.N. Khare  Carl Sagan  John E. Zumberge  Deborah S. Sklarew  Bartholomew Nagy 《Icarus》1981,48(2):290-297

The complex dark brown solid of a class called tholins, produced on passage of an electrical discharge through a roughly equimolar mixture of methane and ammonia with 2.6% water vapor, is analyzed by vacuum pyrolysis followed by gas chromatography and mass spectrometry. Pyrolyzates include a wide range of aliphatic and aromatic nitriles, alkanes, aromatic hydrocarbons, pyrrole, and pyridine. This tholin is remarkably stable to 950°C. It and its degradation products are candidate constituents of planetary aerosols in the outer solar system and of the grains in the interstellar medium.  相似文献   

Genesis of some tertiary Indian coals from the chemical composition of ash – a statistical approach: Part 1     

Arpita Sharma  Ananya Saikia  Puja Khare  B P Baruah 《Journal of Earth System Science》2014,123(7):1705-1715

In the present investigation, 37 numbers of high sulphur tertiary coal samples from Meghalaya, India have been studied on the basis of proximate and ash analysis. Various statistical tools like Bivariant Analysis, Principal Component Analysis (PCA) and Hierarchical Clustering Analysis (HCA), and also the geochemical indicators were applied to determine the dominant detrital or authigenic affinity of the ash forming elements in these coals. The genetic interpretation of coal as well as the coal ash has been carried out based on chemical compositions of high temperature ash (HTA) by using Detrital/Authigenic Index. X-Ray Diffraction (XRD) analysis was also carried out to study the mineralogy of the studied coal ashes. Both statistical tools and geochemical indicators have confirmed the detrital nature of these coals as well as the ash forming elements.  相似文献   

Uncertainty of soil erosion modelling using open source high resolution and aggregated DEMs     

Arun Mondal  Deepak Khare  Sananda Kundu  Sandip Mukherjee  Anirban Mukhopadhyay  Surajit Mondal 《地学前缘(英文版)》2017,8(3):425-436

Digital Elevation Model (DEM) is one of the important parameters for soil erosion assessment. Notable uncertainties are observed in this study while using three high resolution open source DEMs. The Revised Universal Soil Loss Equation (RUSLE) model has been applied to analysis the assessment of soil erosion uncertainty using open source DEMs (SRTM, ASTER and CARTOSAT) and their increasing grid space (pixel size) from the actual. The study area is a part of the Narmada river basin in Madhya Pradesh state, which is located in the central part of India and the area covered 20,558 km². The actual resolution of DEMs is 30 m and their increasing grid spaces are taken as 90, 150, 210, 270 and 330 m for this study. Vertical accuracy of DEMs has been assessed using actual heights of the sample points that have been taken considering planimetric survey based map (toposheet). Elevations of DEMs are converted to the same vertical datum from WGS 84 to MSL (Mean Sea Level), before the accuracy assessment and modelling. Results indicate that the accuracy of the SRTM DEM with the RMSE of 13.31, 14.51, and 18.19 m in 30, 150 and 330 m resolution respectively, is better than the ASTER and the CARTOSAT DEMs. When the grid space of the DEMs increases, the accuracy of the elevation and calculated soil erosion decreases. This study presents a potential uncertainty introduced by open source high resolution DEMs in the accuracy of the soil erosion assessment models. The research provides an analysis of errors in selecting DEMs using the original and increased grid space for soil erosion modelling.  相似文献   

Co-composting of cow dung,municipal solid waste,roadside pond sediment and tannery sludge: role of human hair     

T. Karak  F. R. Kutu  R. K. Paul  K. Bora  D. K. Das  P. Khare  K. Das  A. K. Dutta  R. K. Boruah 《International Journal of Environmental Science and Technology》2017,14(3):577-594

In general, farmers from developing countries often use several feeding mixtures based on materials available in their vicinity resulting in a final poor-quality compost product. Human hair as a composting feed could impact on the nutrient status in prepared compost. In this study, the effect of different amount of human hair to tannery sludge, roadside pond sediment, municipal solid waste and cow dung was investigated during 70-day composting cycle. Human hair addition increased N, P and K from 1.36 to 22.85, 53.06 to 189.80 and 4.13 to 39.26%, respectively, over control. Total metal and arsenic contaminations were significantly higher than in control but lower than the Indian permissible limit. Highest amount of human hair in composting feed indicated that the germination index for tea seed (Camellia sinensis L.) was less than 80% reflecting the possible remaining phytotoxic substances. Redundancy analysis revealed that there was a significance influence of the physico-chemical variables on bacterial community.  相似文献