The history of star-forming galaxies in the Sloan Digital Sky Survey     

N. V. Asari  R. Cid Fernandes  G. Stasi&#;ska  J. P. Torres-Papaqui  A. Mateus  L. Sodré Jr    W. Schoenell  J. M. Gomes 《Monthly notices of the Royal Astronomical Society》2007,381(1):263-279

  相似文献   

Semi-empirical analysis of Sloan Digital Sky Survey galaxies – IV. A nature via nurture scenario for galaxy evolution     

Abílio Mateus  Laerte Sodré  Jr    Roberto Cid Fernandes  Gra&#;yna Stasi&#;ska 《Monthly notices of the Royal Astronomical Society》2007,374(4):1457-1472

  相似文献   

The star formation history of Seyfert 2 nuclei     

R. Cid Fernandes  Q. Gu  J. Melnick  E. Terlevich †  R. Terlevich †  D. Kunth  R. Rodrigues Lacerda  B. Joguet 《Monthly notices of the Royal Astronomical Society》2004,355(1):273-296

  相似文献   

Massive star populations in Wolf–Rayet galaxies     

I. F. Fernandes  R. de Carvalho  T. Contini  R. R. Gal 《Monthly notices of the Royal Astronomical Society》2004,355(3):728-746

  相似文献   

40Ar‐39Ar chronology of lunar meteorites Northwest Africa 032 and 773     

Vera A. Fernandes  Ray Burgess  Grenville Turner 《Meteoritics & planetary science》2003,38(4):555-564

Abstract— The ⁴⁰Ar‐³⁹Ar dating technique has been applied to the lunar meteorites Northwest Africa 032 (NWA 032), an unbrecciated mare basalt, and Northwest Africa 773 (NWA 773), (composed of cumulate and breccia lithologies), to determine the crystallization age and timing of shock events these meteorites may have experienced. Stepped heating analyses of several different samples of NWA 032 gave complex age spectra but indistinguishable total ages with a mean of 2.779 ± 0.014 Gyr. Possible causes of the complex age spectra obtained from NWA 032 include recoil of ³⁹Ar, or the presence of pre‐shock ⁴⁰Ar incorporated into shock‐melt veins. The effects of shock veins were investigated by laser fusion of 20 small samples expected to contain varying proportions of the shock veins. The laser ages show a narrow age distribution between 2.61–2.86 Gyr and a mean of 2.73 ± 0.03 Gyr, identical to the total age of ?2.80 Gyr obtained for the bulk sample. Diffusion calculations based on the stepped heating data indicate that Ar release can be reconciled by release from feldspar (and possibly shock veins) at low temperatures followed by pyroxene at higher temperatures. The exposure age of NWA 032 is 212 ± 11 Myr, and it contains low trapped solar Ar. Stepped heating of cumulate and breccia portions of NWA 773 also give a relatively young age of 2.91 Gyr. The presence of trapped Ar in the breccia makes the age determination of this component less precise, but release of Ar appears to be from the same mineral phase, assumed to be plagioclase, in both lithologies. A marked difference in exposure age between the 2 lithologies also exists, with the breccia having spent 81 Myr longer at the lunar surface; this finding is consistent with the higher trapped Ar content of this lithology. Assuming that 2.80 Gyr and 2.91 Gyr are the crystallization ages of NWA 032 and NWA 773 respectively, these two meteorites are the youngest lunar mare basalts available for study.  相似文献   

Brazilian Decimetric Array (Phase-I)     

H. S. Sawant  R. Ramesh  J. R. Cecatto  C. Faria  F. C. R. Fernandes  R. R. Rosa  M. C. Andrade  S. Stephany  L. B. T. Cividanes  C. A. I. Miranda  L. C. L. Botti  J. W. S. V. Boas  J. H. Saito  C. E. Moron  N. D. Mascarenhas  K. R. Subramanian  M. S. Sundararajan  E. Ebenezer  M. R. Sankararaman 《Solar physics》2007,242(1-2):213-220

An East – West, one-dimensional radio interferometer array consisting of five parabolic dish antennas has been set up at Cachoeira Paulista (longitude 45°0′20″ W, latitude 22°41′19″ S) for observations of the Sun and some of the strong sidereal sources by the Instituto Nacional de Pesquisas Espaciais (INPE), Brazil. This is Phase-I of the proposed Brazilian Decimetric Array and can be operated at any frequency in the range 1.2 – 1.7 GHz. The instrument has been in operation since November 2004 onwards at 1.6 GHz. The angular and temporal resolutions at this frequency are ∼3′ and 100 ms, respectively. Details of the array, analog/digital receiver system, and a preliminary East – West one-dimensional solar image at the 1.6 GHz are presented in this paper.  相似文献   

Northwest Africa 032: Product of lunar volcanism     

T. J. Fagan  G. J. Taylor  K. Keil  T. E. Bunch  J. H. Wittke  R. L. Korotev  B. L. Jolliff  J. J. Gillis  L. A. Haskin  E. Jarosewich  R. N. Clayton  T. K. Mayeda  V. A. Fernandes  R. Burgess  G. Turner  O. Eugster  S. Lorenzetti 《Meteoritics & planetary science》2002,37(3):371-394

Abstract— Mineralogy, major element compositions of minerals, and elemental and oxygen isotopic compositions of the whole rock attest to a lunar origin of the meteorite Northwest Africa (NWA) 032, an unbrecciated basalt found in October 1999. The rock consists predominantly of olivine, pyroxene and chromite phenocrysts, set in a crystalline groundmass of feldspar, pyroxene, ilmenite, troilite and trace metal. Whole‐rock shock veins comprise a minor, but ubiquitous portion of the rock. Undulatory to mosaic extinction in olivine and pyroxene phenocrysts and micro‐faults in groundmass and phenocrysts also are attributed to shock. Several geochemical signatures taken together indicate unambiguously that NWA 032 originated from the Moon. The most diagnostic criteria include whole‐rock oxygen isotopic composition and ratios of Fe/Mn in the whole rock, olivine, and pyroxene. A lunar origin is documented further by the presence of Fe‐metal, troilite, and ilmenite; zoning to extremely Fe‐rich compositions in pyroxene; the ferrous oxidation state of all Fe in pyroxene; and the rare earth element (REE) pattern with a well‐defined negative europium anomaly. This rock is similar in major element chemistry to basalts from Apollo 12 and 15, but is enriched in light REE and has an unusually high Th/Sm ratio. Some Apollo 14 basalts yield a closer match to NWA 032 in REE patterns, but have higher concentrations of Al₂O₃. Ar‐Ar step release results are complex, but yield a whole‐rock age of ?2.8 Ga, suggesting that NWA 032 was extruded at 2.8 Ga or earlier. This rock may be the youngest sample of mare basalt collected to date. Noble gas concentrations combined with previously collected radionuclide data indicate that the meteorite exposure history is distinct from currently recognized lunar meteorites. In short, the geochemical and petrographic features of NWA 032 are not matched by Apollo or Luna samples, nor by previously identified lunar meteorites, indicating that it originates from a previously unsampled mare deposit. Detailed assessment of petrographic features, olivine zoning, and thermodynamic modelling indicate a relatively simple cooling and crystallization history for NWA 032. Chromite‐spinel, olivine, and pyroxene crystallized as phenocrysts while the magma cooled no faster than 2 °C/h based on the polyhedral morphology of olivine. Comparison of olivine size with crystal growth rates and preserved Fe‐Mg diffusion profiles in olivine phenocrysts suggest that olivine was immersed in the melt for no more than 40 days. Plumose textures in groundmass pyroxene, feldspar, and ilmenite, and Fe‐rich rims on the phenocrysts formed during rapid crystallization (cooling rates ?20 to 60 °C/h) after eruption.  相似文献   

The Brazilian decimetric array and space weather     

Hanumant S. Sawant  Natchimuthuk Gopalswamy  Reinaldo R. Rosa  Robert A. Sych  Sergey A. Anfinogentov  Francisco C.R. Fernandes  José R. Cecatto  Joaquim E.R. Costa 《Journal of Atmospheric and Solar》2011,73(11-12):1300-1310

  相似文献   

Effects of alkaline-activated fly ash and Portland cement on soft soil stabilisation     

Nuno Cristelo  Stephanie Glendinning  Lisete Fernandes  Amândio Teixeira Pinto 《Acta Geotechnica》2013,8(4):395-405

This paper studies the effects of sodium-based alkaline activators and class F fly ash on soil stabilisation. Using the unconfined compressive strength test (UCS), the effectiveness of this binder is compared with that of a common cement-based binder. Influence of the activator/ash ratio, sodium oxide/ash ratio and sodium hydroxide concentration was also analysed. Sodium hydroxide concentrations of 10, 12.5 and 15 molal were used for the alkaline-activated specimens (AA), with activator/ash ratios between 1 and 2.5 and ash percentages of 20, 30 and 40 %, relatively to the total solids (soil + ash). UCS was determined at curing periods of 7, 28, 90 and 365 days, and the most effective mixtures were analysed for mineralogy with XRD. The results showed a clear increase in strength with decreasing activator/ash ratio (up to a maximum of 43.4 MPa), which is a positive result since the activator is the most expensive component in the mixture. Finally, UCS results of the cement and AA samples, at 28 days curing, were very similar. However, AA results proved to be just between 20 and 40 % of the maximum UCS obtained at 1 year curing, while cement results at 28 days are expected to be between 80 and 90 % of its maximum.  相似文献   

Estimation of nitrate load from septic systems to surface water bodies using an ArcGIS-based software     

Liying Wang  Ming Ye  J. Fernando Rios  Raoul Fernandes  Paul Z. Lee  Richard W. Hicks 《Environmental Earth Sciences》2013,70(4):1911-1926

Nitrate, as a commonly identified groundwater and surface water pollutant, poses serious threats to human health and the environment. One important source of nitrate in the environment is due to wastewater treatment using Onsite Sewage Treatment and Disposal Systems (OSTDS) (a.k.a., septic systems). To facilitate water resources and environmental management, an ArcGIS-Based Nitrate Load Estimation Toolkit (ArcNLET) is developed to simulate nitrate transport and estimate nitrate load from septic systems and collocated fertilizer applications in groundwater to surface water bodies. It is a screening tool based on a simplified conceptual model of groundwater flow and nitrate transport. It is used in this study to estimate nitrate load from thousands of septic systems to surface water bodies in two neighborhoods located in Jacksonville, FL, USA, where nitrate due to septic systems is believed to be one of the reasons of nutrient enrichment and an isotope study indicates that denitrification is significant. A global sensitivity analysis is performed to identify critical parameters for model calibration, and the most critical parameter is the first-order decay coefficient used to simulate the denitrification process. Hydraulic conductivities at different soil zones have different levels of influence on simulated nitrate concentrations at different locations. By manually adjusting model parameters, simulated shapes of water table and nitrate concentration agree reasonably with average field observations, suggesting that ArcNLET is able to simulate spatial variability of field observations. Estimated nitrate loads exhibit spatial variability, which is useful to facilitate decisions on the conversion of OSTDS into sewers in certain areas for reducing nitrate load from septic systems to surface water bodies.  相似文献