On the scavenging of SO2 by large and small rain drops: V. A wind tunnel and theoretical study of the desorption of SO2 from water drops containing S(IV)     

S. K. Mitra  A. U. Hannemann 《Journal of Atmospheric Chemistry》1993,16(3):201-218

An experimental and theoretical study has been carried out to investigate the rate of desorption of SO₂ from water drops falling at terminal velocity in air. The experiments were carried out in the Mainz vertical wind tunnel in which water drops of various sizes containing S(IV) in various concentrations were freely suspended in the vertical airstream of the tunnel. The results of these experiments were compared with the predictions of three theoretical models, and with the experiments of Walceket al. This comparison shows that the predictions of the diffusion model of Kronig and Brink in the formulation given by Walcek and Pruppacher agree well with the experimental results for all relevant large and small rain-drop sizes, and for all considered concentrations of S(IV) inside the drops. In contrast, the predictions of the diffusion model which assumes complete internal mixing inside a drop agrees with the experimental results only if the concentration of S(IV) inside the drop is less than that equivalent of an equilibrium SO₂ concentration of 15 ppbv. At larger concentrations, the theoretical predictions of the model for complete internal mixing progressively deviate from the experimental results. It is further shown that Barrie's double film model can be used to interpret the resistance to diffusion inside a drop in terms of a diffusion boundary layer inside the drop which increases in thickness with decreasing concentration of S(IV). Applying our results to the desorption of SO₂ from small and large rain drops falling below an assumed cloud base, shows that for typical contents of S(IV) inside the drops substantial amounts of SO₂ will desorb from these drops unless H₂O₂ is present in the surrounding air.  相似文献   

Evolution of the multipolar magnetic field in isolated neutron stars     

Dipanjan Mitra  Sushan Konar  Dipankar Bhattacharya 《Monthly notices of the Royal Astronomical Society》1999,307(2):459-462

The evolution of the multipolar structure of the magnetic field of isolated neutron stars is studied assuming the currents to be confined to the crust. We find that, except for multipoles of very high order ( l ≳25), the evolution is similar to that of a dipole. Therefore no significant evolution is expected in the pulse shape of isolated radio pulsars because of the evolution of the multipole structure of the magnetic field.  相似文献   

Assessment of degraded lands of puruliya district, west bengal using remotely sensed data     

K M Saini  T K Deb  P P Mitra  S G Ghatol  A K Sen  N C Saha  S N Das 《Journal of the Indian Society of Remote Sensing》1999,27(1):23-30

Land degradation in Puruliya district, West Bengal was assessed using remote sensing techniques. Analysis of satellite data (False Colour Composite in 1:50,000 scale) was carried out visually and subsequent ground verification and translation of imgae interpretation units into various categories of degraded lands. The results indicate that 31.8 per cent area of the district suffers from one or the other kind of land degradation. Water induced soil erosion is the major problem which accounts for 31.3 per cent area of the district. Land degradation due to waterlogging is limited to only 0.3 per cent area whereas 0.2 per cent area is degraded due to rock quarries, brick kiln and indus-trial effluents.  相似文献   

Effects of estuarine organic matter biogeochemistry on the bioaccumulation of PAHs by two epibenthic species     

S. Mitra  P. L. Klerks  T. S. Bianchi  J. Means  K. R. Carman 《Estuaries and Coasts》2000,23(6):864-876

Polycyclic aromatic hydrocarbon (PAH) biota-sediment accumulation factors (BSAF) were quantified in sediments from two sites in southeastern Louisiana in a 14 d microcosm study usingPalaemonetes pugio, andRangia cuneata and two radiolabeled PAHs, phenanthrene and benzo[a]pyrene (b[a]p). For both PAHs studied, mean BSAFs were significantly higher (p<0.0001) in both organisms in sediments from Bayou Trepagnier, (BSAF=0.628 g OC g TLE⁻¹), a brackish swamp, compared to Pass Fourchon (0.065 g OC g TLE⁻¹), a coastal salt marsh. In order to explain observed patterns in BSAFs, organic carbon-normalized PAH distribution coefficients between the sediment and freely dissolved phases (K_OC)_OBS were determined as well as the various geochemical variables of particulate and dissolved organic matter (POM and DOM, respectively). These included analyses of particle surface area, total organic carbon (TOC), carbon to nitrogen ratios (C∶N), and dissolved organic carbon (DOC). Bayou Trepagnier was higher in surface area, TOC, C∶N, as well as DOC suggesting that the difference in BSAFs may be attributed to compositional differences in POM and DOM between sites. We can not exclude the possibility that other factors (such as differences in organism behavior resulting from contrasting sediment characteristics) were responsible for BSAFs varying between the two sites. Phenanthrene BSAFs were typically higher than b[a]p BSAFs, suggesting contaminants were limited in their desorption from sediment particles as a function of PAH molecular weight. Mean BSAFs for both PAHs were higher on Day 7 than on Day 14. The reason for this decrease is unclear, but did not appear to be due to organisms becoming increasingly stressed in the microcosms. Visual observations indicated that animals remained feeding while no decreases in organism total lipid levels were detected. The trends in BSAFs between sites and over the time course of this experiment suggest that contaminant bioaccumulation in estuarine systems should not be considered to be an equilibrium process.  相似文献   

Nature of Coherent Radio Emission from Pulsars     

Dipanjan Mitra 《Journal of Astrophysics and Astronomy》2017,38(3):52

The pulsar radio emission originates from regions below 10% of the light cylinder radius. This requires a mechanism where coherent emission is excited in relativistic pair plasma with frequency \(\nu _{\mathrm{cr}}\) which is below the plasma frequency \(\nu _{\circ }\) i.e. \(\nu _{\mathrm{cr}} < \nu _{\circ }\). A possible model for the emission mechanism is charged bunches (charged solitons) moving relativistically along the curved open dipolar magnetic field lines capable of exciting coherent curvature radio emission. In this article, we review the results from high quality observations in conjunction with theoretical models to unravel the nature of coherent curvature radio emission in pulsars.  相似文献   

Identification and classification of geographically isolated wetlands in North Alabama using geographic object based image analysis (GeOBIA)     

Tyler Jones  Luke Marzen  Chandana Mitra  Michael Barbour 《国际地球制图》2019,34(7):769-784

Due to recent Supreme Court rulings, there has been an increased interest in the isolated wetlands of the United States. These types of wetlands serve vital ecological roles such as water quality regulation and as a habitat of biological diversity. This study focuses specifically on mapping of geographically isolated wetlands, or those that are separated from traditional wetlands by a given spatial extent, using Geographic Object-Based Image Analysis (GeOBIA). GeOBIA is a type of remote sensing analysis that identifies objects and features in data-sets via automated methodologies. This type of analysis offers the opportunity to increase the efficiency of what has traditionally been a very labour intensive process of manual photo-interpretation. This analysis resulted in the delineation of 26,424 areas as geographically isolated wetlands. These results were assessed for accuracy through both manual inspection of aerial imagery and field verification which yielded accuracies of 83.7 and 87.7%, respectively.  相似文献   

Statistical improvement in detection level of gravitational microlensing events from their light curves     

Ichsan Ibrahim  Hakim L.Malasan  Chatief Kunjaya  Anton Timur Jaelani  Gerhana Puannandra Putri  Mitra Djamal 《天文和天体物理学研究(英文版)》2018,(4)

In astronomy,the brightness of a source is typically expressed in terms of magnitude.Conventionally,the magnitude is defined by the logarithm of received flux.This relationship is known as the Pogson formula.For received flux with a small signal to noise ratio(S/N),however,the formula gives a large magnitude error.We investigate whether the use of Inverse Hyperbolic Sine function(hereafter referred to as the Asinh magnitude)in the modified formulae could allow for an alternative calculation of magnitudes for small S/N flux,and whether the new approach is better for representing the brightness of that region.We study the possibility of increasing the detection level of gravitational microlensing using 40 selected microlensing light curves from the 2013 and 2014 seasons and by using the Asinh magnitude.Photometric data of the selected events are obtained from the Optical Gravitational Lensing Experiment(OGLE).We found that utilization of the Asinh magnitude makes the events brighter compared to using the logarithmic magnitude,with an average of about 3.42×10~(-2)magnitude and an average in the difference of error between the logarithmic and the Asinh magnitude of about 2.21×10(-2)magnitude.The microlensing events OB140847 and OB140885 are found to have the largest difference values among the selected events.Using a Gaussian fit to find the peak for OB140847 and OB140885,we conclude statistically that the Asinh magnitude gives better mean squared values of the regression and narrower residual histograms than the Pogson magnitude.Based on these results,we also attempt to propose a limit in magnitude value for which use of the Asinh magnitude is optimal with small S/N data.  相似文献   

Parametric Study of Smooth Joint Parameters on the Shear Behaviour of Rock Joints     

M. Bahaaddini  P. C. Hagan  R. Mitra  B. K. Hebblewhite 《Rock Mechanics and Rock Engineering》2015,48(3):923-940

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Characterizing the multi-risk with respect to plausible natural hazards in the Balasore coast,Odisha, India: a multi-criteria analysis (MCA) appraisal     

Anirban Mukhopadhyay  Sugata Hazra  Debasish Mitra  C. Hutton  Abhra Chanda  Sandip Mukherjee 《Natural Hazards》2016,80(3):1495-1513

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An alternative interpretation for the map expression of “abrupt” changes in lateral stratigraphic level near transverse zones in fold-thrust belts     

Sanghoon Kwon  Gautam Mitra 《地学前缘(英文版)》2012,3(4):401-406

The map expression of "abrupt" changes in lateral stratigraphic level of a thrust fault has been traditionally interpreted to be a result of the presence of(1) a lateral(or oblique) thrust-ramp,or(2) a frontal ramp with displacement gradient、and/or(3) a combination of these geometries.These geometries have been used to interpret the structures near transverse /ones in fold-thrust belts(FTB).This contribution outlines an alternative explanation that can result in the same map pattern by lateral variations in stratigraphy along the strike of a low angle thrust fault.We describe the natural example of the Leamington transverse zone.which marks the southern margin of the Pennsy lvanian—Permian Oquirrh basin with genetically related lateral stratigraphic variations in the North American Sevier(TB.Thus.the observed map pattern at this zone is closely related to lateral stratigraphic variations along the strike of a horizontal fault.Even though the present-day erosional level shows the map pattern that could be interpreted as a lateral ramp.the observed structures along the Leamington zone most likely share the effects of the presence of a lateral(or oblique) ramp,lateral stratigraphic variations along the fault trace.and the displacement gradient.  相似文献