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961.
Steven S. Perakis 《水文研究》2002,16(17):3507-3511
962.
Peter J. Boyce Steven Phillipps J. Bryn Jones Simon P. Driver Rodney M. Smith Warrick J. Couch 《Monthly notices of the Royal Astronomical Society》2001,328(1):277-282
We present the results of a study of the morphology of the dwarf galaxy population in Abell 868, a rich, intermediate-redshift cluster which has a galaxy luminosity function (LF) with a steep faint-end slope . A statistical background subtraction method is employed to study the colour distribution of the cluster galaxies. This distribution suggests that the galaxies contributing to the faint-end of the measured cluster LF can be split into three populations: dwarf irregular galaxies (dIrrs) with dwarf elliptical galaxies (dEs) with and contaminating background giant ellipticals (gEs) with . The removal of the contribution of the background gEs from the counts only marginally lessens the faint-end slope . However, the removal of the contribution of the dIrrs from the counts produces a flat LF . The dEs and the dIrrs have similar spatial distributions within the cluster, except that the dIrrs appear to be totally absent within a central projected radius of about 0.2 Mpc . The number densities of both dEs and dIrrs appear to fall off beyond a projected radius of ≃ 0.35 Mpc. We suggest that the dE and dIrr populations of A868 have been associated with the cluster for similar time-scales, but evolutionary processes such as 'galaxy harassment' tend to fade the dIrr galaxies while having a much smaller effect on the dE galaxies. The harassment would be expected to have the greatest effect on dwarfs residing in the central parts of the cluster. 相似文献
963.
964.
965.
Steven B. SIMON Lawrence GROSSMAN Andrew M. DAVIS 《Meteoritics & planetary science》1997,32(2):259-269
Abstract— Through freeze-thaw disaggregation of the Murchison meteorite, we have recovered, in addition to many spinel-hibonite spherules, several hibonite-rich inclusion fragments in which the hibonite has wider ranges in TiO2 contents (e.g., 0.07–8.6 wt% in one inclusion and 2–10 wt% in another) than previously observed within single inclusions. In these inclusions, there are sharp contacts between texturally early, Ti-poor hibonite and relatively late, Ti-rich hibonite, and the two types occur in complex intergrowth textures that are not consistent with crystallization from a melt in a single-stage cooling event. One inclusion has, in addition to relatively TiO2-rich hibonite, some that is virtually TiO2-free but contains ~1 wt% MgO and ~1.5 wt% SiO2. Instead of the common substitution of Mg + Ti for 2Al, Mg coupled with Si in this case, probably reflecting crystallization from an unusual, Ti-free silicate liquid. Ion microprobe analyses of Ti-rich and Ti-poor hibonite from this inclusion yield quite similar trace-element patterns and Mg-isotopic compositions. The results are most consistent with formation of Ti-rich hibonite from Ti-poor hibonite by addition of Mg and Ti to the latter by exchange with a hot, Ti-rich liquid. That this occurred without a resolvable change in the Mg-isotopic composition requires that the Ti-rich, second generation of hibonite formed <2.5 times 105 yr later than the Ti-poor hibonite. Observations of spinel-hibonite spherules and spherule fragments in our sample suite provide additional evidence that, despite the claims by Greenwood et al. (1994), spinel-hibonite spherules crystallized from individual, molten droplets, as earlier suggested by Macdougall (1981) and MacPherson et al. (1983). 相似文献
966.
Bonnie X. Chang Allan H. Devol Steven R. Emerson 《Deep Sea Research Part I: Oceanographic Research Papers》2010,57(9):1092-1101
Recent studies of the nitrogen gas excess produced during water column denitrification have indicated that water column denitrification rates calculated using nitrate deficit-type methods could be a substantial underestimate. Since there are no other significant processes that produce (or consume) N2 in the oxygen deficient zone (ODZ), its excess above background can be used to estimate the amount of denitrification, avoiding assumptions made in nitrate deficit calculations of the composition of the respired organic matter and also uncertainties in the nitrogen removal pathways. Dissolved N2, Ar, and nutrient concentrations were measured at 2 stations in the ODZ of the eastern tropical South Pacific (ETSP) in order to compare the nitrogen gas excess with the dissolved inorganic nitrogen (DIN) deficit due to denitrification. In contrast with previous findings in the Arabian Sea ODZ, the shapes of the N2 excess and DIN deficit profiles were similar in the ETSP ODZ, with maxima at the top of the ODZ. Maximum DIN deficits at each station were 19 and 18 μM N compared to the maximum N2 excesses of 15 and 20 μM N, respectively. Given the same considerations of the volume and residence time for the oxygen deficient zone waters, denitrification rates for the ETSP estimated from the N2 excess would be comparable or no greater than 30% larger than the one determined using the DIN deficit. This implies that the source of the DIN removed from the ODZ is either deep sea nitrate or organic matter with an N:P ratio close to Redfield. 相似文献
967.
968.
... all for the want of a nail. English nursery rhyme Feedback is the essential property of multiphase models for the evolution of galaxies. In this review, we stress the generic
behavior of toy models to highlight those features that are inevitable consequences of assumptions in the current catalog
of galactic evolution calculations.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
969.
Timothy P. Jones Steven M. Fortier Volker Mosbrugger Jochen Roessler Thorsen Utescher & Abdul R. Ashraf 《地学学报》1997,9(1):19-23
A detailed stable carbon isotopic profile of a late Miocene browncoal seam from the Lower Rhine Embayment, Germany, reveals two clear separate cycles of different frequency: this is the first instance of this type of isotopic signature being recognized within coals. The ratio of the two frequencies suggests this isotopic signal possibly resulted from climatic or vegetational responses to orbital forcing. The cyclicity has been enhanced by the application of conventional filtering methods on the data set. An analysis of the seam's palynology indicates a correlation between heavier isotopic compositions and the presence of Sequoiapollenites polyformosus , whose parent plant is believed to have favoured moist climates and higher groundwater tables. 相似文献
970.
Alarcon Vladimir J. Linhoss Anna C. Kelble Christopher R. Mickle Paul F. Sanchez-Banda Gonzalo F. Mardonez-Meza Fernando E. Bishop Joseph Ashby Steven L. 《Natural Hazards》2022,111(3):2933-2962
Natural Hazards - Southeast Florida (SF) is among the most vulnerable regions to sea-level rise in the United States of America. The consequences associated with sea-level rise (SLR) are already... 相似文献