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Neil Trentham Leda Sampson Manda Banerji 《Monthly notices of the Royal Astronomical Society》2005,357(2):783-792
Redshift surveys such as the Sloan Digital Sky Survey (SDSS) have given a very precise measurement of the galaxy luminosity function down to about MR =−17 (≈ MB =−16) . Fainter absolute magnitudes cannot be probed because of the flux limit required for spectroscopy. Wide-field surveys of nearby groups using mosaic CCDs on large telescopes are able to reach much fainter absolute magnitudes, about MR =−10 . These diffuse, spiral-rich groups are thought to be typical environments for galaxies, so their luminosity functions should be the same as the field luminosity function. The luminosity function of the groups at the bright end ( MR < −17) is limited by Poisson statistics and is far less precise than that derived from redshift surveys. Here we combine the results of the SDSS and the surveys of nearby groups, and we supplement the results with studies of Local Group galaxies in order to determine the galaxy luminosity function over the entire range −25 < MR < −9 . The average logarithmic slope of the field luminosity function between MR =−19 and MR =−9 is α=−1.26 , although a single power law is a poor fit to the data over the entire magnitude range. We also determine the luminosity function of galaxy clusters and demonstrate that it is different from the field luminosity function at a high level of significance; there are many more dwarf galaxies in clusters than in the field, due to a rise in the cluster luminosity function of α∼−1.6 between MR =−17 and MR =−14 . 相似文献
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Ann Bostrom Robert E. O’Connor Gisela Böhm Daniel Hanss Otto Bodi Frida Ekström Pradipta Halder Sven Jeschke Birgit Mack Mei Qu Lynn Rosentrater Anethe Sandve Ingrid Sælensminde 《Global Environmental Change》2012,22(1):210-222
Few comparative international studies describe the climate change policies people are willing to support and the reasons for their support of different policies. Using survey data from 664 economics and business undergraduates in Austria, Bangladesh, Finland, Germany, Norway, and the United States, we explore how perceived risk characteristics and mental models of climate change influence support for policy alternatives. General green policies such as funding research on renewable technologies and planting trees were the overwhelmingly most popular policy alternatives. Around half the students support carbon reduction policies such as requiring higher car fuel efficiency and increasing taxes on fossil fuels. Least popular were engineering alternatives such as fertilizing the oceans and replacing fossil fuels with nuclear power. Variations among nations are generally small. Support for different policy alternatives corresponds with different causal thinking. Those who hold a pollution model of the causes of climate change, tend to blame environmental harms (e.g., air pollution from toxic chemicals), see general green policy alternatives as effective, and support general green policies. Support of carbon reduction strategies is associated with seeing carbon emissions as the cause and reducing carbon emissions as effective solutions. Support of engineering solutions increases with identifying volcanoes among causes and regarding engineering solutions as effective. Although these international students agree that climate change is a threatening problem, their causal thinking correlates with support for different mitigative policy actions, with the most popular ones not necessarily the most effective. 相似文献
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The investigations on the Plasma Laser Star Model of QSOs reported in our previous paper are continued. Here we assume that QSOs are early type stars with temperatures in the range 104–105 K. It is pointed out that the spectral lines of such stars may have asymmetric shapes and large broadening leading to errors in measurement up to 20 Å. The conventional red-shift theory, however, allows fitting errors much more than this amount for many QSO emission lines. By taking the abundances of elements in QSO atmsopheres identical with the average cosmic abundance we analyze and compare the interpretations of the emission lines of 330 QSOs (263 QSOs are from Burbidgeet al.'s list and the rest are more recently discovered (QSOs) according to the new and the conventional theories. 相似文献
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The tenets of sustainable development are often ignored by growing cities in developing countries. Salt Lake City, located on the eastern fringes of Kolkata, despite being a planned township, has failed to manage its water resources in a sustainable way. Results from the study show that the water supplied at the households is hard in nature, saline, and replete with dissolved solids. The problem is further aggravated due to over-extraction of groundwater resources, resulting in an intense fall of the groundwater level in the area. This paper attempts to suggest measures for sustainable water resource management, with particular emphasis on rainwater harvesting. 相似文献
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The similarities of the spectra of QSOs with those of Wolf-Rayet stars are pointed out. The emission spectrum of the earliest discovered QSO, 3C 273, in the ultraviolet and visible regions is interpreted as that of an object deficient in hydrogen like Wolf-Rayet stars but havingno redshift. The visible emission spectra of two other QSOs, 3C 48 and 3C 280.1, are also similarly interpreted. It is further assumed that the absorption lines of QSOs are produced in an expanding atmosphere so that they are violet shifted as in Wolf-Rayet stars. Fifty-four out of 55 narrow absorption lines of the QSO Q 1246-057 are interpreted on the assumption that the average velocity of the absorbing ions is 500 km s–1, although the redshift theory can explain only 23 lines by invoking six different redshifts: Four of the five emission lines of the same object can be identified assuming no shift. Since the QSOs are here assumed to be comparatively local objects, the problems of energy supply, superluminal velocities, etc., raised by the conventional explanation do not arise in this case.Presently at the Institut für Physikalische und Theoretische Chemie, Universität Erlangen, F.R.G. 相似文献
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The present paper reports significant evidence of insect-plant interactions in the Upper Gondwana sequence (Early Cretaceous) from various localities of the Rajmahal Formation in the Rajmahal Basin of Jharkhand State, India. This evidence is among the first Early Cretaceous evidence of phytophagy and is recognised by various types of feeding traces namely continuous marginal, discontinuous marginal and non-marginal. These traces may indicate herbivory of pinnate leaves ofPtilophyllurn (Bennettitales) and these herbivores may have assisted the plants in pollination. Additional evidence for a plant-insect relationship is on the lamina o f Phyllopteroides pinnae (Osmundaceae) which was used for ovipostional sites containing oval egg impressions that occur along the veins in the leaf lamina. Further, the evidence of insect galls recognised on a Nipaniophyllurn (Pentoxylales) leaf surface indicates that the lamina was used as a shelter habitat for insect larvae. These galls show some similarity with extinct leaf galls reported on Glossopteris (Glossopteridales) leaves recorded from the Permian of Kashmir Himalaya, India as well as on galls on Sophora (Fabaceae) and Eomangferophyllum (Anacardiaceae) leaves from the Neogene flora of India. Similar spherical leaf galls are induced by Diptera (Cecidomyiidae) and Hymenoptera (Pteromalidae) on leaves of modern Anadenanthera peregrina from Brazil. The present findings from the Upper Gondwana Sequence of India reveals that these types of insect-plant relationships existed during the Gondwana time and continued up to the recent, perhaps having a role in the co-evolution of present flora and fauna. 相似文献
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Narendra Kumar Meena M. Prakasam Ravi Bhushan Sudipta Sarkar Pranaya Diwate Upasana Banerji 《Environmental Earth Sciences》2017,76(1):39
The lakes of the Himalaya are degrading due to increase in toxic heavy metal loading. This study reports the last 50-year heavy metal pollution loading in the Rewalsar Lake, Himachal Pradesh, India. Sediment cores were recovered to study the pollution loading in the lake sediments. The 137Cs and 210Pb isotope-based sedimentation rate suggest rapid sedimentation in the lake during the last ~50 years. The concentrations of Mn, Cu, Zn, Cd, Pb, Co, Ni, Cr metals in the lake sediments owe its contributions both to the natural and anthropogenic sources. Prior to ca 1990 AD, metal loading was dominated by the lithogenic input, whereas post ca 1990 AD the metal loading was controlled by the anthropogenic factors. The Pb concentration in the lake gradually increased during 1990–2004 and then decreased significantly till present. The higher concentration of Pb seems to be derived from the fossil fuel burning, while the Cr concentration in the lake indicates the use of fertilizer in the catchment area. The lowest concentrations of elements around ca 1990 AD seem to have occurred due to channelization of the lake feeding system. 相似文献
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Varshni maintained that the emission lines observed in QSOs can be satisfactorily explained as being due to laser action in certain atomic species in the expanding envelope of a star and having no appreciable redshift. In order to test this hypothesis we have examined the conditions conducive to laser action in the stellar atmosphere and compared all the emission lines of 633 QSOs discovered till August 1976 (as listed by Burbidgeet al.) with the laser transitions found in the laboratory till April 1976 (as listed by Willett and Becket al.). It was found that 88% of the QSO lines agreed to within 10 Å with the laser lines and 94% agreed to within 20 Å. The main reason Greenstein and Schmidt failed to fit the spectral lines of 3C 48 and 3C 273 with known emission lines is that laser transitions in hydrogen do not occur in stellar atmospheres. The spectra are explained on the basis of the new theory and the broadening of lines explained. 相似文献