Thermosolutal instability of a partially-ionized plasma     

R. C. Sharma  Neela Rani 《Astrophysics and Space Science》1988,140(1):55-63

The thermosolutal instability of a partially-ionized plasma in the presence of a horizontal magnetic field is considered to include the frictional effect of collisions of ionized with neutrals. The sufficient conditions for non-existence of overstability are derived. The solute gradient and magnetic field introduce oscillatory modes in thermosolutal convection which were non-existent in their absence. The magnetic field and stable solute gradient are found to have stabilizing effects whereas collisional effect of ionized with neutrals is found to have destabilizing effect on thermosolutal instability of a partially ionized plasma.  相似文献   

Optical intra-day variability timescales and black hole mass of the blazars     

S.P. GuptaU.S. Pandey  K. SinghB. Rani  J. PanJ.H. Fan  A.C. Gupta 《New Astronomy》2012,17(1):8-17

In this paper, we have used optical intra-day variability archive data to calculate the central black hole masses and Eddington luminosities for nine blazars: 3C 66A, AO 0235+164, S5 0716+714, PKS 0735+178, OJ 287, 1215+303, 1216−010, 1308+326, PKS 1510−089, Mrk 501 and BL Lac using intra-day variability timescales and periodicity (if present). The calculated central black hole mass of these nine blazars using intra-day variability timescales are found to be in the range of 1.22-25.30 × 10⁷ M_⊙ and corresponding Eddington luminosity in the range of 1.58-32.88 × 10⁴⁵ erg s⁻¹. The black hole mass and Eddington luminosity are in the range of 0.32-31.23 × 10⁸ M_⊙ and 1.23-31.20 × 10⁴⁶ erg s⁻¹, respectively when optical Doppler factor is taken into account. The comparison show, our estimated values of black hole mass are consistent with earlier reported values. Periodicity were present in two blazars OJ 287 and 1216−010 which give the central black hole mass of these blazars in the range of 1.32-14.6 × 10⁷ M_⊙ and corresponding Eddington luminosity in the range of 1.60-19.0 × 10⁴⁵ erg s⁻¹, respectively.  相似文献   

The Eastern Ghats Belt … A polycyclic granulite terrain     

Dhruba Mukhopadhyay  Krishnapriya Basak 《Journal of the Geological Society of India》2009,73(4):489-518

The Eastern Ghats Belt is a polycyclic granulite terrain along the east coast of India whose western boundary is marked by a shear zone along which the granulites are thrusted over the cratonic units of the Indian shield, and its northern margin is marked by the presence of a number of fault-bounded blocks. Recent work has convincingly brought out that there are domains within the belt having different evolutionary histories. The segment south of the Godavari Rift went through a high grade thermo-tectonic event at ∼1.6–1.7 Ga. North of the Godavari Rift in a narrow zone along the western boundary the last high-grade metamorphic event is of late Archaean age. A series of alkaline plutons along the western boundary zone testifies to a rifting episode at ∼1.3–1.5 Ga. In the major part of the EGB the metamorphism is broadly of Grenvillian age, with two major thermo-tectonic pulses at ∼1.1–1.2 Ga and ∼0.95–1.0 Ga. But high grade conditions persisted for a long period and younger thermal events of ∼0.65 Ga to ∼0.80 Ga are locally recorded. There are differences in the tectonometamorphic histories of different domains, but the tectonic significance of these differences remains uncertain. Pan-African (0.50–0.55) thermal overprints are common and become conspicuous along the western boundary zone. The thrusting of the Eastern Ghats granulites in a hot state over the cratons to the west is of Pan-African age. In the Rodinia assembly (∼0.9 Ga) the Eastern Ghats and the Rayner-Napier Complexes of Antarctica were contiguous, but the pre-Rodinia configuration of these terrains remains unclear. At ∼0.8 Ga during the Rodinia break up Greater India rifted apart from East Antarctica, and only later it docked with Australia-East Antarctica at 530–550 Ma. The continuation of the East Antarctic Pan-African orogenic belts into the Eastern Ghats is yet to be ascertained.  相似文献   

Extraction of Nd isotopes from bulk deep sea sediments for paleoceanographic studies on Cenozoic time scales     

Ellen E. Martin  Susanna W. Blair  George D. Kamenov  Howie D. Scher  Elodie Bourbon  Chandranath Basak  Derrick N. Newkirk 《Chemical Geology》2010,269(3-4):414-431

Nd isotopes preserved in fossil fish teeth and ferromanganese crusts have become a common tool for tracking variations in water mass composition and circulation through time. Studies of Nd isotopes extracted from Pleistocene to Holocene bulk sediments using hydroxylamine hydrochloride (HH) solution yield high resolution records of Nd isotopes that can be interpreted in terms of deep water circulation, but concerns about diagenesis and potential contamination of the seawater signal limit application of this technique to geologically young samples.In this study we demonstrate that Nd extracted from the > 63 μm, decarbonated fraction of older Ocean Drilling Program (ODP) sediments using a 0.02 M HH solution produces Nd isotopic ratios that are within error of values from cleaned fossil fish teeth collected from the same samples, indicating that the HH-extractions are robust recorders of deep sea Nd isotopes. This excellent correlation was achieved for 94 paired fish teeth and HH-extraction samples ranging in age from the Miocene to Cretaceous, distributed throughout the north, tropical and south Atlantic, and composed of a range of lithologies including carbonate-rich oozes/chalks and black shales. The strong Nd signal recovered from Cretaceous anoxic black shale sequences is unlikely to be associated with ferromanganese oxide coatings, but may be derived from abundant phosphatic fish teeth and debris or organic matter in these samples.In contrast to the deep water Nd isotopic signal, Sr isotopes from HH-extractions are often offset from seawater values, suggesting that evaluation of Sr isotopes is a conservative test for the integrity of Nd isotopes in the HH fraction. However, rare earth elements (REE) from the HH-extractions and fish teeth produce distinctive middle REE bulge patterns that may prove useful for evaluating whether the Nd isotopic signal represents uncontaminated seawater. Alternatively, a few paired HH-extraction and cleaned fish teeth samples from each site of interest can be used to verify the seawater composition of the HH-extractions. The similarity between isotopic values for the HH-extraction and fish teeth illustrates that the extensive cleaning protocol applied to fish teeth samples is not necessary in typical, carbonate-rich, deep sea sediments.  相似文献   

Photogrammetry and 3D laser scanning as spatial data capture techniques for a national craniofacial database     

Zulkepli  Majid  Albert K.  Chong  Anuar  Ahmad  Halim  Setan  Abdul Rani  Samsudin 《The Photogrammetric Record》2005,20(109):48-68

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A note on 2-D lithospheric deformation due to a blind strike-slip fault     

Sunita Rani  Sarva Jit Singh 《Journal of Earth System Science》2005,114(1):105-110

Analytical solution for the problem of a surface-breaking long strike-slip fault in an elastic layer overlying an elastic half-space is well known. The purpose of this note is to obtain the corresponding solution for a blind fault. Since the solution is valid for arbitrary values of the fault-depth and the dip angle, the effects of these two important fault parameters can be studied numerically. The variation of the parallel displacement and shear stress with the distance from the fault is studied numerically for different values of the fault-depth and dip angle.  相似文献   

Atmospheric Dry Deposition to Marble and Red Stone     

Ranjit?Kumar  Abha?Rani  K.?Maharaj?Kumari  S.?S.?SrivastavaEmail author 《Journal of Atmospheric Chemistry》2005,50(3):243-261

This paper presents dry deposition flux and deposition velocity of atmospheric particles on white marble and red stone at Dayalbagh, a suburban site of semi arid region, which is 10 km away from the industrial sector of the Agra city where due to agricultural practices vegetation predominates. The wind speed at Agra is mostly in the range of 1–2 m s^–1. The atmospheric calm conditions at Agra in summer, monsoon, and winter seasons are 47%, 35%, and 76%, respectively. Industrial areas of the city are away from Dayalbagh and are located in the NE, E, SE, and SW sectors. The main industrial activities, which are in operation in Agra city and its outskirts, are foundry and forging industry. The other industrial activities in Agra are rubber processing, lime oxidation and pulverization, chemicals, engineering and brick refractory kilns. Dry deposition samples were collected on dry days on white marble and red stone (0.224 m × 0.224 m × 0.02 m) using surface washing method. Both slabs were fixed to an iron stand (1.5 m height) at an angle of about 80 from the horizontal and exposed for 24 h on the roof of the faculty building. The order of deposition flux on white marble is NH₄⁺ > Mg²⁺ > Ca²⁺ > Na⁺ > Cl^– > K⁺ > NO₃^– > SO₄^2– > F^– and that on red stone is NH₄⁺ > Mg²⁺ > Ca²⁺ > SO₄^2– > Na⁺ > NO₃^– > K⁺ > F^– > Cl^–. Average dry deposition flux of major ions varies from 3.4 to 128.5 M m^–2 d^–1. The sum of major cations on white marble and red stone are 516.4 and 450.4 eq m^–2 d^–1, respectively while sum of major anions are 425.3 and 400.4 eq m^–2 d^–1 on white marble and red stone, respectively. Higher deposition of all ions was observed when wind blows from NE as most of the Agra Iron foundries and Ferozabad glass industries lie in this direction. The mean values of dry deposition velocity of ions vary between 0.22 cm s^–1 to 1.49 cm s^–1. Deposition velocity for all ions is higher on white marble than red stone inspite of rougher surface of red stone as compared to white marble. This could be due to the chemical nature of white marble, which is made of dolomite and hence adds significant amount of ions by dissolution during washing. Seasonally the deposition velocity was highest in winter.  相似文献   

A Long Term Study on Chemical Composition of Rainwater at Dayalbagh, a Suburban Site of Semiarid Region     

Ranjit Kumar  Abha Rani  S. P. Singh  K. Maharaj Kumari  S. S. Srivastava 《Journal of Atmospheric Chemistry》2002,41(3):265-279

Rainwater samples were collected for the monsoon period of 1988 and 1991–1996 at Dayalbagh (Agra), a suburban site situated in semiaridregion. The mean pH was 7.01 ±1.03 well above 5.6, which is the reference pH. Concentration of Ca²⁺ was observed to be highest followed by Mg²⁺, NH₄ ⁺,SO₄ ^2–, Cl^–,NO₃ ^–, Na⁺, F^– and K⁺. The ratios of SO₄ ^2– + NO₃ ^– andCa²⁺ + Mg²⁺ (TA/TC) have been considered as indicatorfor acidity. In the Agra region ratio of TA/TC is quite below 1.0 indicating alkaline nature of rainwater. The lowest value of 0.24 was observed in 1991 likely due to the lowest rain depth of the decade. The highest value of 0.54 was observed in 1996, a year with a large rain depth and increase in line (vehicular traffic) and area sources (population growth). Good correlation between Ca²⁺ and NO₃ ^–,Ca²⁺ and SO₄ ^2– andSO₄ ^2– and NO₃ ^–,indicates that wind carried dust and soil play a significant role in neutralization of precipitation acidity.  相似文献   

Crustal deformation due to non-uniform slip along a long fault     

Sarva Jit Singh  Mukesh Punia  Sunita Rani 《Geophysical Journal International》1994,118(2):411-427

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Static deformation of two welded half-spaces due to dip-slip faulting     

Sunita Rani  Sarva Jit Singh 《Journal of Earth System Science》1992,101(3):269-282

Closed-form expressions for the displacements and stresses at any point of either of two elastic half-spaces in welded contact caused by a dip-slip line source obtained earlier are integrated analytically to derive the elastic residual field due to a long dip-slip fault of finite width. The results are valid for an arbitrary dip of the fault. The variation of the displacement field with the distance from the fault as well as with the distance from the interface is studied numerically. It is found that the displacement field is heavily dependent on the dip angle. Contour maps showing the residual elastic field in the two half-spaces caused by a vertical dip-slip fault located in one of the half-spaces are also obtained.  相似文献