Relative Toxicity of Some Non-Insecticidal Chemicals to the Free Living Larvae Guinea-Worm (Dracunculus medinensis)     

S. Mehta  R. C. Srivastava  A. N. Gupta 《洁净——土壤、空气、水》1982,10(4):397-400

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A theoretical study of bond distances,X-ray spectra and electron density distributions in borate polyhedra     

Abha Gupta  J. A. Tossell 《Physics and Chemistry of Minerals》1981,7(4):159-164

The borate polyhedra BO ₃ ^3? , B(OH)₃, BO ₄ ^5? , and B(OH) ₄ ^? are studied using the ab initio and multiple scattering Xα quantum mechanical methods. The ab initio self-consistent-field (SCF) molecular orbital (MO) method, at the minimum basis set level, predicts equilibrium B-O distances within 0.04 Å of their average values in solids so long as the polyhedron charge is small. Orbital energies from double zeta basis set ab initio calculations and analogies with isoelectric compounds are used to assign the X-ray spectra of BO ₃ ^3? and to predict the valence region spectra of BO ₄ ^5? . Contour maps of the difference between molecular and superimposed free atom electron densities show charge buildup along the B-O bond which is only slightly smaller than that observed in CO ₃ ^2? .  相似文献   

On the formation of a sharp layer of metallic constituents at sunrise in the lower thermosphere     

J S Shirke  R Sridharan  S P Gupta  A D Danilov  A A Pokhunkov  V K Semenov  V A Verfolomeev 《Journal of Earth System Science》1981,90(2):141-146

Results are presented of two instrumented rocket experiments performed from an equatorial station, one at night and the other shortly after sunrise. The ion neutral composition as well as electron density and the amplitude of plasma irregularities were monitored. During the latter flight, a sharp layer of ionisation with its lower boundary at 100 km was observed. The layer had a half width close to 1 km and a peak electron density of 5·6× 10⁴cm^?3. Large amplitude of plasma irregularities, noticed on the negative gradient portion of the layer indicates a downward direction of the polarisation electric field during the observations. The resulting downward drift of photoions as they are produced at sunrise followed by the local decrease of the drift is suggested to be the cause of the layer formation at that altitude. The long lasting nature of such layers once identified on ionograms indicates that they are constituted of metallic ions possibly of micrometeoritic origin deposited overnight in the lower thermosphere. The required photoionisation rate of production of the metallic ions at sunris eis about 2 cm^?3 sec^?1.  相似文献   

The numerical evaluation of theH-functions of radiative transfer in active amplifying media     

S. R. Das Gupta  Chitta Ranjan Nayak  Santanu Das Gupta 《Astrophysics and Space Science》1984,103(2):271-284

The present paper contains extensive tables of the values of theH-functionH(z,<0) and of the moments ofQ(x) (in terms of which the moments ofH(z, ) can be determined) appropriate for transfer of radiation in active amplifying media in which<0. These values have been computed correct to the 7th decimal place for values of in the range (–10^–12)-(–10³⁰) and for values of z[0,1] with the aid of a 48-point gaussian quadrature formula.  相似文献   

Nature of sedimentary organic matter in the lower reaches of the Godavari River basin, India     

Lallan Prasad Gupta   《Journal of Asian Earth Sciences》2001,19(6):364

The distribution and nature of sedimentary organic matter (OM) have been examined in sediment cores collected from the lower reaches, including estuary, of the Godavari River in order to understand sedimentation patterns, sources, and diagenesis of OM. The samples were analyzed for organic carbon (Corg), total nitrogen, amino acids and hexosamines. The observed irregular trends in Corg distribution with depth indicate the unstable nature of bed sediment in the lower reaches of the river. Yet, in the lower estuarine region, regular trends in Corg distribution with depth reflect the deposition of sediment. The atomic ratio of Corg and total nitrogen (C/N; 10.5–16.1) also supported this observation. The distribution of amino acids and diagenetic indicators (β-ala+γ-aba mol.%, AA/HA and Glc-NH₂/Gal-NH₂) in individual cores revealed the post-depositional changes in the OM. In the core sediment from the lower reaches, there was no clear cut trend in amino acid content with depth. In the estuarine region, however, amino acid content was very low (50.5 and 186.5 μg g⁻¹) in the upper layers compared to that in the lower layers (558.5 and 1099.3 μg g⁻¹). Reactivity index (range 0.3–3.7) revealed that OM in the upper few centimeters, especially in the lower estuarine region, was more reactive relative to that in the deeper layers.  相似文献   

Straightforward inversion scheme (SIS) for one-dimensional magnetotelluric data     

P. K. Gupta  Sri Niwas  V. K. Gaur 《Journal of Earth System Science》1996,105(4):413-429

This paper presents a Straightforward Inversion Scheme (SIS) for interpreting one-dimensional magnetotelluric sounding data. The basic steps of SIS are (i) parameterization of the layered model such that the layer thickness, expressed in units of its skin depth, is a constant (α); (ii) expansion of the reflection function at each interface as a power series in parameter u = exp(-2(1 +j)α√f);(iii) development of a recurrence relation between the coefficients of the same powers ofu in the power series of reflection functions of any two successive layers; (iv) estimation of the impedance power series coefficients using regressed minimum norm estimator; and (v) evaluation of layer resistivities and thicknesses using the inverse recurrence relation. The power of SIS is established by inverting four synthetic data sets and two field data sets. The effect of noise is extensively studied on a synthetic data set, deliberately corrupted with increasing levels of Gaussian random noise up to 25%. It is found that the scheme can retrieve broad features of the true model even with noise levels as high as 25%. On the basis of findings of different experiments conducted on SIS, it is concluded that SIS is an efficient, robust algorithm with high resolving power. Further, being linear, it is non-iterative and it dispenses with the requirement of having to choose an initial guess model.  相似文献   

Stochastic stability of tethered buoyant platforms     

P.K. Muhuri  A.S. Gupta 《Ocean Engineering》1983,10(6):471-479

A moment method for analysing the stochastic stability of the surge motion of a tethered buoyant platform (TBP) in a random sea is examined. In the differential equation describing the surge motion the variation of tether tension caused by the vertical component of the wave forces is random-time dependent in form. The asymptotic moment behaviour of the solution is determined and approximated in terms of an integral equation. Under the assumption of a narrow band process imposed upon the random coefficient, the stability results are obtained with the aid of deterministic stability theory. The mean square stability is studied and criteria for stability are obtained in terms of the damping coefficient and the auto-correlation function of the random sea.  相似文献   

El Niño/Southern Oscillation (ENSO) Related Variations in Particulate Export Fluxes in the Western and Central Equatorial Pacific     

Hodaka Kawahata  Lallan Prasad Gupta 《Journal of Oceanography》2003,59(5):663-670

Time-series data from sediment trap moorings intermittently deployed during 1991–1999 show that the fluxes of biogenic material (carbonate, opal and organic matter, including amino acids) and other related parameters are temporally and spatially distinct across the Western Pacific Warm Pool (WPWP). These variations resulted from the El Niño and La Niña conditions, which alternately prevailed over the equatorial Pacific Ocean during the mooring deployments. The westernmost WPWP (a hemipelagic region) recorded relatively high average total mass and amino acid fluxes during the El Niño event. This was in sharp contrast to the eastern part of the WPWP (oligotrophic and weak upwelling regions) which recorded higher flux values during the La Niña event. Settling particulate organic matter was rich in labile components (amino acids) during La Niña throughout the study area. Relative molar ratios of aspartic acid to β-alanine together with relative molar content of non-protein amino acids β-alanine and γ-aminobutyric acid) suggested that organic matter degradation was more intense during La Niña relative to that during El Niño in the WPWP. This study clearly shows that during an El Niño event the well documented decrease in export flux in the easternmost equatorial Pacific is accompanied by a significant increase in export flux in the westernmost equatorial Pacific Ocean.  相似文献   

Metabolism of 2-acetylaminofluorene by rainbow trout     

Harish C. Sikka  A. Ruth Steward  Sayed A. Elmarakby  Subodh Kumar  U. Devanaboyin  Ramesh C. Gupta 《Marine environmental research》1995,39(1-4)

In order to examine factors that may contribute to the reported resistance of rainbow trout, Shasta strain, to the well-known hepatocarcinogenic effects of 2-acetylaminofluorene (AAF), the in-vitro and in-vivo metabolism of [¹⁴C]AAF in trout has been examined. Trout (compared to rat) liver microsomes metabolized AAF more efficiently, producing 3-fold larger amounts of ring-hydroxylated metabolites (7-hydroxy-AAF and 5-hydroxy-AAF), but 5-fold less N-hydroxy-AAF. Freshly isolated trout hepatocytes extensively metabolized AAF to form the same ring-hydroxylated metabolites and their respective glucuronide and sulfate conjugates. N-OH-AAF (plus its conjugates) and covalently-bound AAF derivatives amounted, respectively, to < 1% and 1.4–1.6% of total metabolites. Liver DNA of trout treated with AAF contained a single AAF-DNA adduct identified as N-(deoxyguanosin-8-yl)-2-aminofluorene (the major persistent AAF-DNA adduct found in rat liver). The level of this adduct (12 attomoles/μg DNA) was about 1000-fold lower than the level of AAF-DNA adduct previously reported in rat liver. The data show that trout liver, compared to rat liver, is considerably less efficient in metabolizing AAF to carcinogenic metabolites, and more efficient in forming nontoxic products, thus possibly explaining, in part, the resistance of trout to AAF-induced hepatocarcinogenesis.  相似文献   

Influence of wave approach angle on TLP's response     

S. Chandrasekaran  A.K. Jain  Anupam Gupta   《Ocean Engineering》2007,34(8-9):1322-1327

The current study focuses on the response analysis of triangular tension leg platform (TLP) for different wave approach angles varying from 0° through 90° and its influence on the coupled dynamic response of triangular TLPs. Hydrodynamic loading is modeled using Stokes fifth-order nonlinear wave theory along with various other nonlinearities arising caused by change in tether tension and change in buoyancy caused by set down effect. Low frequency surge oscillations and high frequency tension oscillations of tethers are ignored in the analysis. Results show that wave approach angle influences the coupled dynamic response of triangular TLP in all degrees of freedom except heave. Response in roll and sway degrees of freedom are activated which otherwise are not present in TLP's response to unidirectional waves. Pitch and roll responses are highly stochastic in nature indicating high degree of randomness. Variation in surge, sway and heave responses are nonlinear and are not proportional to change in wave height for the same period.  相似文献