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31.
Astronomy Letters - We present the results of our spectroscopic study of the lenticular galaxy NGC 4143—a peripheral member of the Ursa Major cluster. Using the observations at the 6-m SAO... 相似文献
32.
Heavy metal pollution assessment through comparison of different indices in sewage-fed fishery pond sediments at East Kolkata Wetland,India 总被引：3，自引：0，他引：3
Subhasis Sarkar Phani Bhusan Ghosh Alok Kumar Sil Tapan Saha 《Environmental Earth Sciences》2011,63(5):915-924
The sediments of the raw sewage-fed fishpond system at East Kolkata Wetland (EKW) were analyzed for heavy metal content in
a comprehensive way. Various indices of contamination like enrichment factor (EF), geo-chemical index (I
geo), modified degree of contamination (mDC), and pollution load index (PLI) were assessed. In all cases, instead of literature values, the metal concentrations of less
contaminated sites, separated by the statistical approach of the hierarchical cluster analysis, were used as baseline values.
In the present study, about 70% of the pond sediments are found uncontaminated, 5% display low degree of contamination and
25% are designated as moderate degree of contamination. Both the EF and I
geo indices highlighted that the metals lead (Pb), cadmium (Cd), and chromium (Cr) are responsible for the contamination while
there is little anthropogenic input in cases of Cu, Zn, and Ni. Most of the ponds situated near the main sewage flowing canals
as well as the main traffic highway and close to the solid waste dumping areas recorded higher degree of metal contamination
as evident from spatial variation of mDC and PLI indices in the study area. Indices comparison study clearly indicates that although these are calculated using different
methods, these may or may not produce the same indices values and hence the values should neither be compared nor be averaged.
But all the above indices are directly related to a common term contamination factor (CF). Classification of contamination
levels based on these CF values is found to be similar and this classification is only valid up to the level of high degree
of contamination. Thus, the use of any one of these indices is sufficient to classify the degree of contamination of an area.
However, to evaluate the contamination per metal, both I
geo and EF are effective while, to assess the composite effect of all the metals, PLI is preferable to mDC. 相似文献
33.
Kanchan Wakadikar Avik Sil Niranjan Kolekar Shalini Tandon Rakesh Kumar 《Environmental Earth Sciences》2011,64(1):25-28
Drilling fluids are used for drilling natural gas, oil and water wells. These spill over into the surrounding soil at the
point of drilling, which may impair soil health. A laboratory investigation was carried out to determine the effect of non
aqueous drilling fluid (NADF) and synthetic base oil used with it on soil health as indicated by the dehydrogenase activity.
A non-sterile sandy loam soil was treated with different amounts of NADF and base oil at a rate of 800, 8,000 and 16,000 mg kg−1. Initially, reduction in dehydrogenase activity was observed, but it increased with the incubation time. On the 60th day
of incubation dehydrogenase activity in untreated control was 1.04 mg TPF g−1 h−1 whereas in the soil samples treated with NADF and the base oil (16,000 mg kg−1), the activity was 1.53 mg TPF h−1 and 1.90 mg TPF h−1, respectively, which was 72 and 82% more than in untreated control. Base oil-treated soil showed more dehydrogenase activity
than that observed with NADF. Both NADF and base oil stimulated the soil dehydrogenase activity. 相似文献
34.
Olga K. Sil’chenko Alexei S. Rastorguev Nikolai G. Bochkarev 《Astrophysics and Space Science》2007,307(4):385-393
SNAP, the SuperNova Acceleration Probe, is planned as a space-based telescope designed specifically to search for and monitor
cosmological supernovae and weak lensing. In this paper we propose some other mission objectives which are of great importance
in the fields of Galactic and extragalactic astronomy and which can be done as by-products with the same instrumentation and
survey strategy as currently proposed for the main SNAP mission. 相似文献
35.
O. K. Sil’chenko 《Astronomy Letters》2002,28(4):207-216
Our inzvestigation of the central region in NGC 4548, a bright Sb galaxy with a large-scale bar, using the Multipupil Field Spectrograph of the 6-m telescope revealed a chemically decoupled compact stellar nucleus with [Fe/H]=+0.6 and [Mg/Fe]=+0.1...+0.2 and with a mean stellar-population age of 5 Gyr. This nucleus, a probable circumnuclear disk coplanar with the global galactic disk, is embedded in the bulge whose stars are generally also young, T≈4 Gyr, although they are a factor of 2.5 more metal-poor. The bulge of NGC 4548 is triaxial and has a de Vaucouleurs surface-brightness profile; the unusual characteristics of its stellar population suggest the bulge formation or completion in the course of secular evolution in the triaxial potential of the global bar. The ionized gas within 3″ of the NGC 4548 nucleus rotates in a plane inclined to the principal symmetry plane of the galaxy, possibly, even in its polar plane, which may also result from the action of the large-scale bar. 相似文献
36.
Acounter-rotating gas disk has been detected in the SA0 galaxy IC 560 located at the periphery of a sparse group of six late-type galaxies. The pattern of gas excitation and mid-infrared colors are indicative of ongoing star formation within 1 kpc of the center. Outside the gas disk with star formation the large-scale stellar disk of the galaxy has an old age and a very low metallicity, [Z/H] ≈ ?1. The source of external gas accretion onto IC 560 is undetected; the only option is a single infall of a companion rich in high-metallicity gas. 相似文献
37.
I. V. Chilingarian O. K. Sil’chenko V. L. Afanasiev Ph. Prugniel 《Astronomy Letters》2007,33(5):292-298
We report the discovery of young embedded structures in three diffuse elliptical galaxies (dE) in the Virgo cluster: IC 783,
IC 3468, and IC 3509. We performed 3D spectroscopic observations of these galaxies with the MPFS spectrograph at the 6-m Special
Astrophysical Observatory telescope and obtained spatially resolved distributions of kinematic and stellar population parameters
by fitting high-resolution PEGASE. HR synthetic single stellar populations (SSP) in pixel space. In all three galaxies, the
luminosity-weighted age of the nuclei (∼4 Gyr) is considerably younger than that of the population in the outer regions of
the galaxies. We discuss two possibilities for the formation of such structures—a dissipative merger event and a different
ram pressure stripping efficiency during two consecutive crossings of the Virgo cluster centre.
The article was translated by the authors. 相似文献
38.
To reconstruct dark energy models the redshift z eq , marking the end of radiation era and the beginning of matter-dominated era, can play a role as important as z t , the redshift at which deceleration parameter experiences a signature flip. To implement the idea we propose a variable equation of state for matter that can bring a smooth transition from radiation to matter-dominated era in a single model. A popular Λ∝ ρ dark energy model is chosen for demonstration but found to be unacceptable. An alternative Λ∝ ρ a 3 model is proposed and found to be more close to observation. 相似文献
39.
Pothapakula Praveen Kumar Osuri Krishna K. Pattanayak Sujata Mohanty U. C. Sil Sourav Nadimpalli Raghu 《Natural Hazards》2017,88(3):1769-1787
Natural Hazards - Sea surface temperature (SST) plays a significant role in tropical cyclone (TC) formation and intensity evolution, while at the same time, TC induces SST changes during its life... 相似文献
40.
We present the results of a comprehensive spectrophotometric study of the central region in the regular lenticular galaxy NGC 4036 with two spectrographs of the 6-m telescope. The unresolved nucleus of NGC 4036 is shown to be chemically decoupled: [Mg/Fe]=+0.3 at the very center, whereas in the immediate vicinity of its nucleus, this ratio abruptly drops to +0.1 and does not change further along the radius. A study of isophotal morphology in combination with a kinematic analysis has proven that the rotation of stars at the NGC 4036 center is axisymmetric. However, the major-axis turn within R<5″ should be considered real. We interpret this turn as evidence for the existence of a tilted circumnucelar stellar disk with a radius of ～250 pc in NGC 4036. The NGC 4036 bulge may be triaxial, and the ionized gas at the galactic center is then concentrated toward the principal plane of the ellipsoidal potential. 相似文献