Chemical abundances in a UV-selected sample of galaxies     

ThierryContini  Marie A.Treyer  MarkSullivan  Richard S.Ellis 《Monthly notices of the Royal Astronomical Society》2002,330(1):75-91

We discuss the chemical properties of a sample of UV-selected intermediate-redshift  (0≲z≲0.4)  galaxies in the context of their physical nature and star-formation history. This work represents an extension of our previous studies of the rest-frame UV-luminosity function (Treyer et al.) and the star-formation properties of the same sample (Sullivan et al.) . We revisit the optical spectra of these galaxies and perform further emission-line measurements restricting the analysis to those spectra with the full set of emission lines required to derive chemical abundances. Our final sample consists of 68 galaxies with heavy-element abundance ratios and both UV and CCD B -band photometry. Diagnostics based on emission-line ratios show that all but one of the galaxies in our sample are powered by hot, young stars rather than by an AGN. Oxygen-to-hydrogen (O/H) and nitrogen-to-oxygen (N/O) abundance ratios are compared with those of various local and intermediate-redshift samples. Our UV-selected galaxies span a wide range of oxygen abundances, from ∼0.1 to 1 Z_⊙, intermediate between low-mass H  ii galaxies and massive starburst nuclei. For a given oxygen abundance, most have strikingly low N/O values. Moreover, UV-selected and H  ii galaxies systematically deviate from the usual metallicity–luminosity relation in the sense of being more luminous by  2–3 mag  . Adopting the 'delayed-release' chemical evolution model, we propose our UV-selected sources are observed at a special stage in their evolution, following a powerful starburst that enriched their ISM in oxygen and temporarily lowered their mass-to-light ratios. We discuss briefly the implications of our conclusions on the nature of similarly selected high-redshift galaxies.  相似文献   

Reflection of Alfvén waves by non-uniform ionospheres     

P. Ellis  D.J. Southwood 《Planetary and Space Science》1983,31(1):107-117

Magnetospheric Alfvén waves are reflected by the ionosphere. We investigate the effect of horizontally varying ionospheric conductivity on the process of Alfvén wave reflection. Four idealised ionospheric models are considered in detail. We find that the reflection process is strongly dependent on the orientation of the wave electric field vector with respect to the boundary between high and low conductivities, and under certain conditions subsidiary Alfvén waves are generated. The field-aligned currents in the subsidiary Alfvén waves serve to close divergent horizontal currents resulting from the non-uniform ionospheric conductivity. The implications for ground-based pulsation studies are discussed.  相似文献   

Listric extensional fault systems - results of analogue model experiments   总被引：2，自引：0，他引：2  

P. G. Ellis  K. R. McClay 《Basin Research》1988,1(1):55-70

Abstract Analogue models are a powerful tool for investigating progressive deformation in extensional fault systems. This paper presents exciting new insights into the progressive evolution of hanging wall structures in listric extensional terranes. Analogue models, scaled to simulate deformation in a sedimentary sequence, were constructed for simple listric and ramp/flat listric extensional detachments. For each detachment geometry homogeneous sand, sand/mica and sand/clay models were used to simulate respectively, deformation of isotropic sediments, of anisotropic sediments and of sedimentary sequences with competency contrasts. Roll-over anticlines with geometrically necessary crestal collapse graben structures are characteristic of the steepening-upwards segments of listric extensional fault systems in all of our models. With progressive deformation, crestal collapse grabens show hanging wall nucleation of new faults. Variations in graben size, amount of fault rotation and throw, are dependent on detachment curvature and amount of extension. Individual faults and associated fault blocks may significantly change shape during extension. Complex and apparently conjugate fault arrays are the result of superposition of successive crestal collapse grabens. Ramp/flat listric extensional fault systems are characterized by a roll-over anticline and a crestal collapse graben system associated with each steepening-upwards segment of the detachment and a ramp zone consisting of a hanging wall syncline and a complex deformation zone with local reverse faults. The roll-over anticlines and crestal collapse graben are similar in geometry to those formed in simple listric extensional systems. The models demonstrate that the geometry of the detachments exerts a fundamental control on the evolution of hanging wall structures. Analysis of particle displacement paths for these experiments provides new insights into the mechanical development of roll-over anticlines. Two general models for deformation above simple listric and ramp/flat listric extensional detachments have been erected.  相似文献   

    

Mark E. Johnson  Ellis A. Monash  Michael S. Waterman 《Mathematical Geology》1979,11(1):63-74

Accepted practice dictates that waterflooding of gas reservoirs should commence, if ever, only when the reservoir pressure has declined to the minimum production pressure. Analytical proof of this hypothesis has yet to appear in the literature however. This paper considers a model for a gas-water reservoir with a variable production rate and enhanced recovery with waterflooding and, using an initial dynamic programming approach, confirms the above hypothesis.  相似文献   

Use of composite data sets for source-tracking enterococci in the water column and shoreline interstitial waters on Pensacola Beach, Florida     

Genthner FJ  James JB  Yates DF  Friedman SD 《Marine pollution bulletin》2005,50(7):724-732

Sources of Enterococcus faecalis isolates from Pensacola Beach, FL. were identified using a library-based approach by applying the statistical method of average similarity to single and composite data sets generated from separate analyses. Data sets included antibiotic resistance analysis (ARA), rep-fingerprints, and fatty acid methyl ester (FAME) profiles. Use of a composite data set composed of ARA and rep-fingerprints, added to the confidence of the identifications. The addition of FAME data to composite data sets did not add to the confidence of identifications. Source identification was performed to better understand risk associated with higher densities of enterococci found in swash zone interstitial water (SZIW) as compared to adjacent bathing water on Pensacola Beach, FL. The "swash zone" is that area of the beach continually washed over by waves. As the potential sources of enterococci were limited in this environment, only two library units, sea gull and human, were constructed. Identification of the beach isolates using a composite data set indicated a sea gull origin. The clonality of the beach isolates suggested that the beach environment selects certain subspecies of E. faecalis.  相似文献   

Volcanic hydrothermal areas and the interpretation of thermal water compositions     

A. J. Ellis 《Bulletin of Volcanology》1966,29(1):575-584

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Marine disposal of mine tailing     

J.L. Littlepage  D.V. Ellis  J. Mcinerney 《Marine pollution bulletin》1984,15(7):242-244

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A case study of coping strategies and landslides in two villages of Central-Eastern Nepal     

Karen Sudmeier-Rieux  Stephanie Jaquet 《Applied geography (Sevenoaks, England)》2012,32(2):680-690

Landslides are an increasing problem in Nepal’s Middle Hills due to both natural and human phenomena: mainly increasingly intense monsoon rains and a boom in rural road construction. This problem has largely been neglected due to underreporting of losses and the dispersed nature of landslides. Understanding how populations cope with landslides is a first step toward developing more effective landslide risk management programs. The present research focuses on two villages in Central-Eastern Nepal, both affected by active landslides but with different coping strategies. Research methods are interdisciplinary, based on a geological assessment of landslide risk and a socio-economic study of the villages using household questionnaires, focus group discussions and transect walks. Community risk maps are compared with geological landslide risk maps to better understand and communicate community risk perceptions, priorities and coping strategies. A modified typology of coping strategies is presented, based on previous work by Burton, Kates, and White (1993) that is useful for decision-makers for designing more effective programs for landslide mitigation. Main findings underscore that coping strategies, mainly seeking external assistance and outmigration, are closely linked to access to resources, ethnicity/social status and levels of community organization. Conclusions include the importance of investing in organizational skills, while building on local knowledge about landslide mitigation for reducing landslide risk. There is great potential to increase coping strategies by incorporating skills training on landslide mitigation in existing agricultural outreach and community forest user group training.  相似文献   

Public policy, institutional investors and climate change: a UK case-study     

Stephanie Pfeifer  Rory Sullivan 《Climatic change》2008,89(3-4):245-262

Institutional investors have two important roles to play in encouraging companies to address the risks and take advantage of the opportunities presented by climate change. The first is through using their influence as shareholders to encourage companies to adopt more proactive approaches to managing the risks and opportunities presented by climate change. The second is through explicitly factoring climate change risks and opportunities into ‘mainstream’ investment analysis processes. While there is growing investor activity on the former, the integration of climate change into investment analysis remains confined to sectors where there are strong government incentives (e.g. for renewable energy) or where greenhouse gas emissions have a market price. This article reviews the evolution of UK institutional investor interest in climate change from 1990 to 2005, focusing in particular on the relative contributions of ‘soft’ policy measures such as information-disclosure and awareness raising, and ‘hard’ policy measures such as regulation and market-based instruments. The article concludes that, over this period, soft policy measures played an important role in encouraging investors to discuss climate change issues with companies, but had minimal influence on investment decisions. It was only with the introduction of hard policy measures that climate change started to be systematically factored into investment analysis. The article canvasses the implications of these findings for government efforts in the UK and elsewhere to encourage investors to play a more proactive role in the climate change debate. It also considers the role that institutional investors themselves can play in strengthening public policy measures to reduce greenhouse gas emissions.  相似文献   

LoCuSS: luminous infrared galaxies in the merging cluster Abell 1758 at z= 0.28     

C. P. Haines  G. P. Smith  E. Egami  N. Okabe  M. Takada  R. S. Ellis  S. M. Moran  K. Umetsu 《Monthly notices of the Royal Astronomical Society》2009,396(3):1297-1307

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