Optical properties of solid and liquid sulfur at visible and infrared wavelengths     

R. Sasson  R. Wright  E.T. Arakawa  B.N. Khare  Carl Sagan 《Icarus》1985,64(3):368-374

Knowledge of the optical constants of elemental sulfur has potential applications to Venus, Jupiter, Io, Amalthea, and the Earth. The real part, n, of the index of refraction of liquid sulfur (at 133°C) and of solid orthorhombic sulfur (at 25°C) for the wavelength range 0.4–2.0 μm were measured ellipsometrically. The imaginary part, k, of the refractive index of liquid sulfur was obtained by transmittance measurements at the same temperature and wavelength range. The reflectance of semi-infinite slabs of solid and liquid sulfur is calculated using the measured n and k values. We confirm that sulfur melts on Io would be classified as “black” by the Voyager imaging system.  相似文献   

Significance of correspondence between river discharge and proloculus size of benthic Foraminifera in paleomonsoonal studies     

Rajiv Nigam  Neloy Khare 《Geo-Marine Letters》1995,15(1):45-50

Variations in the mean proloculus size (MPS) of the benthic foraminiferal speciesRotalidium annectens were studied in a core collected off Karwar (20 m water depth), on the west coast of India. Comparison of downcore variations in the MPS with rainfall (five-year average) over a period of 100 years from the catchment area of the Kali River shows a direct correlation. This implies that higher MPS values indicate high rainfall over the catchment area and thus confirms the earlier hypothesis that the MPS is inversely related to salinity. The correspondence between MPS and rainfall shows a high potential in generating proximity data for the reconstruction of a paleo-precipitational history.  相似文献   

Collapsing supra-massive magnetars: FRBs,the repeating FRB121102 and GRBs     

Patrick Das Gupta  Nidhi Saini 《Journal of Astrophysics and Astronomy》2018,39(1):14

Fast Radio Bursts (FRBs) last for \(\sim \) few milli-seconds and, hence, are likely to arise from the gravitational collapse of supra-massive, spinning neutron stars after they lose the centrifugal support (Falcke & Rezzolla 2014). In this paper, we provide arguments to show that the repeating burst, FRB 121102, can also be modeled in the collapse framework provided the supra-massive object implodes either into a Kerr black hole surrounded by highly magnetized plasma or into a strange quark star. Since the estimated rates of FRBs and SN Ib/c are comparable, we put forward a common progenitor scenario for FRBs and long GRBs in which only those compact remnants entail prompt \(\gamma \)-emission whose kick velocities are almost aligned or anti-aligned with the stellar spin axes. In such a scenario, emission of detectable gravitational radiation and, possibly, of neutrinos are expected to occur during the SN Ib/c explosion as well as, later, at the time of magnetar implosion.  相似文献   

Characteristics of surface ozone in Agra,a sub-urban site in Indo-Gangetic Plain     

Nidhi Verma  Aparna Satsangi  Anita Lakhani  K Maharaj Kumari 《Journal of Earth System Science》2018,127(3):42

In the present study, measurements of surface ozone (\(\hbox {O}_{3}\)) and its precursors (NO and \(\hbox {NO}_{2}\)) were carried out at a sub-urban site of Agra (\(27{^{\circ }}10'\hbox {N}\), \(78{^{\circ }}05'\hbox {E}\)), India during May 2012–May 2013. During the study period, average concentrations of \(\hbox {O}_{3}\), NO, and \(\hbox {NO}_{2}\) were \(39.6 \pm 25.3\), \(0.8 \pm 0.8\) and \(9.1 \pm 6.6 \, \hbox {ppb}\), respectively. \(\hbox {O}_{3}\) showed distinct seasonal variation in peak value of diurnal variation: summer \({>}\) post-monsoon \({>}\) winter \({>}\) monsoon. However, \(\hbox {NO}_{2}\) showed highest levels in winter and lowest in monsoon. The average positive rate of change of \(\hbox {O}_{3}\) (08:00–11:00 hr) was highest in April (16.3 ppb/hr) and lowest in August (1.1 ppb/hr), while average negative rate of change of \(\hbox {O}_{3}\) (17:00–19:00 hr) was highest in December (–13.2 ppb/hr) and lowest in July (–1.1 ppb/hr). An attempt was made to identify the \(\hbox {VOC--NO}_{\mathrm{x}}\) sensitivity of the site using \(\hbox {O}_{3}/\hbox {HNO}_{3}\) ratio as photochemical indicator. Most of the days this ratio was above the threshold value (12–16), which suggests \(\hbox {NO}_{\mathrm{x}}\) sensitivity of the site. The episodic event of ozone was characterized through meteorological parameters and precursors concentration. Fine particles (\(\hbox {PM}_{2.5}\)) cause loss of ozone through heterogeneous reactions on their surface and reduction in solar radiation. In the study, statistical analyses were used to estimate the amount of ozone loss.  相似文献   

A comparative study of soil erosion modelling by MMF,USLE and RUSLE   总被引：1，自引：0，他引：1  

Arun Mondal  Deepak Khare  Sananda Kundu 《国际地球制图》2018,33(1):89-103

The quantitative assessment of spatial soil erosion is valuable information to control the erosion. The study area in a part of Narmada river in central India is selected. The main objective is to assess and compare the results obtained from three soil erosion models using GIS platform. Variation in the rate of erosion of the three models is compared considering varying slope, soil and land use of the area. Three models selected are Morgan–Morgan–Finney (MMF), Universal Soil Loss Equation (USLE) and Revised Universal Soil Loss Equation (RUSLE). The best fit or the most reliable model for the study area is selected after validation with the observed sedimentation data. The results give –39.45%, –9.60% and 4.80% difference in the values of sedimentation by MMF, USLE and RUSLE, respectively, from the observed data. Finally, RUSLE model has been found to be most reliable for the study area.  相似文献   

Triton: stratospheric molecules and organic sediments     

Thompson WR  Singh SK  Khare BN  Sagan C 《Geophysical research letters》1989,16(8):981-984

Hydrocarbons and nitriles are produced in Triton's stratosphere by energetic electrons from Neptune's magnetosphere and other charged particle sources. Laboratory plasma experiments reported here show a substantial yield of molecules from low pressure flows of 10(-3) CH4 in N2 appropriate to Triton if both CH4 and N2 are saturated at the surface. An active magnetosphere similar to that of Uranus would result in a flux approximately 0.3 erg cm-2 s-1 of 0.1-1 MeV electrons in Triton's stratosphere; molecular production rates are then 10(6)-10(8) cm-2 s-1 for NH3, C2H2, HCN, and NCCN; tens of hundreds of gm cm-2 of these compounds per 10(9) yr (and lesser quantities of at least eight other molecules experimentally detected) would freeze to fine-grained white condensates in the lower stratosphere and sediment to the surface. Along with dark/colored organic haze produced in the stratosphere and other heteropolymers produced at the surface, these condensates are subjects to redistribution by aeolian processes and may appear as lag deposits and/or sediment layers. A simple eddy diffusion model indicates abundances approximately 10(19) molec cm-2 for HCN and C2H2, and > 10(17) molec cm-2 for NCCN, CH3CCH, CH2CCH2, and CH3CN in the stratosphere; these and other organic molecules will be detectable by IRIS if the stratosphere is (as expected) heated through ultraviolet and visible light absorption by the haze.  相似文献   

From global to local: Testing the potential of cross-scaling in global data sets     

Nidhi Nagabhatla  R. Wickramasuriya  S. N. Prasad 《Journal of the Indian Society of Remote Sensing》2009,37(3):443-455

The present study investigates the potential of readily available and easily accessible global data sets to understand regional/local level interactions in wetland systems. The biogeographical zones of India were used a base-frame to select three sites. The study well fits the interests of National Wetland Committee of India to investigate and document fundamental information on wetland extent/distribution. The national partnership with SACON represents this interest. SACON commenced the inland wetland inventory module at national scale using geospatial data, although the provincial scale analysis is underway. In addition, the global irrigated area mapping (GIAM-IWMI) project generated multi-scalar spatial outputs for irrigated/rain-fed areas. With the existing information base, a multi-level geospatial analysis using Arc GIS algorithmic modelling was used to derive comprehensive appraisal of wetland systems complementing the data from GIAM and SACON. It was observed that the overlap between the two layers was 58 percent for Gujarat and 10 percent in Tamil Nadu. In Krishna basin the wetland’s cover 1.04 million hectare excluding the rice agro-ecosystem. The difference in the biogeography of the case sites governs the gradient of information derived from both data layers. Additionally, the global lakes and wetlands database (GLWD) database added thematic information on coastal wetlands. In summary we describe the cross-scaling the global data layers to compliment the regional/national level monitoring assignments.  相似文献   

Impacts of salinity parameterizations on temperature simulation over and in a hypersaline lake     

WEN Lijuan  NAGABHATLA Nidhi  ZHAO Lin  LI Zhaoguo  CHEN Shiqiang 《中国海洋湖沼学报》2015,33(3)

In this paper,we introduced parameterizations of the salinity effects(on heat capacity,thermal conductivity,freezing point and saturated vapor pressure) in a lake scheme integrated in the Weather Research and Forecasting model coupled with the Community Land Model(WRF-CLM). This was done to improve temperature simulation over and in a saline lake and to test the contributions of salinity effects on various water properties via sensitivity experiments. The modified lake scheme consists of the lake module in the CLM model,which is the land component of the WRF-CLM model. The Great Salt Lake(GSL) in the USA was selected as the study area. The simulation was performed from September 3,2001 to September 30,2002. Our results show that the modif ied WRF-CLM model that includes the lake scheme considering salinity effects can reasonably simulate temperature over and in the GSL. This model had much greater accuracy than neglecting salinity effects,particularly in a very cold event when that effect alters the freezing point. The salinity effect on saturated vapor pressure can reduce latent heat flux over the lake and make it slightly warmer. The salinity effect on heat capacity can also make lake temperature prone to changes. However,the salinity effect on thermal conductivity was found insignificant in our simulations.  相似文献   

Trapping and amplification of quasi-longitudinal whistler wave in kinetic Alfvén wave localized structures     

Rajesh Kumar Rai  Swati Sharma  Nidhi Gaur  R. P. Sharma 《Astrophysics and Space Science》2016,361(3):110

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GPR studies over the tsunami affected Karaikal beach,Tamil Nadu,south India     

V J Loveson  A R Gujar  R Barnwal  Richa Khare  G V Rajamanickam 《Journal of Earth System Science》2014,123(6):1375-1385

In this study, results of GPR profiling related to mapping of subsurface sedimentary layers at tsunami affected Karaikal beach are presented . A 400 MHz antenna was used for profiling along 262 m stretch of transect from beach to backshore areas with penetration of about 2.0 m depth (50 ns two-way travel time). The velocity analysis was carried out to estimate the depth information along the GPR profile. Based on the significant changes in the reflection amplitude, three different zones are marked and the upper zone is noticed with less moisture compared to other two (saturated) zones. The water table is noticed to vary from 0.5 to 0.75 m depth (12–15 ns) as moving away from the coastline. Buried erosional surface is observed at 1.5 m depth (40–42 ns), which represents the limit up to which the extreme event acted upon. In other words, it is the depth to which the tsunami sediments have been piled up to about 1.5 m thickness. Three field test pits were made along the transect and sedimentary sequences were recorded. The sand layers, especially, heavy mineral layers, recorded in the test pits indicate a positive correlation with the amplitude and velocity changes in the GPR profile. Such interpretation seems to be difficult in the middle zone due to its water saturation condition. But it is fairly clear in the lower zone located just below the erosional surface where the strata is comparatively more compact. The inferences from the GPR profile thus provide a lucid insight to the subsurface sediment sequences of the tsunami sediments in the Karaikal beach.  相似文献