Growth,production, food consumption,and mortality of juvenile spot and croaker: A comparison of tidal and nontidal nursery areas     

Benjamin M. Currin  James P. Reed  John M. Miller 《Estuaries and Coasts》1984,7(4):451-459

As the dominant juvenile finfish in southeast and Gulf of Mexico nursery areas, spot and croaker growth, food consumption, production, and mortality are compared in tidal salt marshes and nontidal brackish systems. Growth rates of spot and croaker from 5 studies ranged from 0.021–0.04 g per g per d. Differences in the annual production and food consumption estimates were primarily due to differences in average biomass. Although mean biomass varied widely, the daily production to mean biomass ratios ranged from 0.021–0.037, suggesting that these systems probably could support more juvenile fish than are present. Spot mortality ranged from 0.023–0.041% per d. Despite large hydrographic differences between tidal and nontidal systems and large differences in the amount of detrital input, the secondary production values and many of the fish population parameters are remarkably similar. This is interpreted as confirmation of the basic trophic similarity of the different systems and the highly adaptable and general nature of juvenile fish. The primary consumers are supported by 50–100% of the algal production. But because the dominant fishes consume only 10–35% of that secondary production, at least in some systems, food does not appear to limit juvenile fish production. Predation on the juveniles is implicated as a limiting factor.  相似文献   

Venus: The 17- to 38-micron spectrum     

R.A. Reed  W.J. Forrest  J.R. Houck  J.B. Pollack 《Icarus》1978,33(3):554-557

The Venus emission spectrum was measured from the NASA Lear Jet on five nights in June 1975. A cooled grating spectrometer with a resolution of γ/δγ ? 25 over the spectral interval 17 to 38μm was used. The main features in the observed spectrum are consisten with the theoretical emission spectrum of a haze of aqueous sulfuric acid droplets suspended in a CO₂ atmosphere.  相似文献   

Tectonic wedging along the rear of the offshore Taiwan accretionary prism     

Wu-Cheng Chi  Donald L. Reed  Greg Moore  Tuan Nguyen  Char-Shine Liu  Neil Lundberg 《Tectonophysics》2003,374(3-4):199-217

The structural geometry, kinematics and density structure along the rear of the offshore Taiwan accretionary prism were studied using seismic reflection profiling and gravity modeling. Deformation between the offshore prism and forearc basin at the point of incipient collision, and southward into the region of subduction, has been interpreted as a tectonic wedge, similar to those observed along the front of mountain ranges. This tectonic wedge is bounded by an east-dipping roof thrust and a blind, west-dipping floor thrust. An east-dipping sequence of forearc-basin strata in the hanging wall of the roof thrust reaches a thickness in excess of 4 km near the tip of the interpreted tectonic wedge. Section restoration of the roof sequence yields an estimate of 4 km of shortening, which is small compared with that inferred in the collision area to the north, based on the variation in distance between the apex of the prism and the island arc.Previous studies propose that either high-angle normal faulting or backfolding has exhumed the metamorphic rocks along the eastern flank of the Central Range in the collision zone on land. To better constrain the initial crustal configuration, we tested 350 crustal models to fit the free-air gravity anomaly data in the offshore region to study the density structure along the rear of the accretionary prism in the subduction and initial collision zones before the structures become more complex in the collision zone on land. The gravity anomaly, observed in the region of subduction (20.2°N), can be modeled with the arc basement forming a trenchward-dipping backstop that is overlain by materials with densities in the range of sedimentary rocks. Near the point of incipient collision (20.9°N), however, the free-air gravity anomaly over the rear of the prism is approximately 40 mgal higher, compared with the region of subduction, and requires a significant component of high density crustal rocks within the tectonic wedge. These results suggest that the forearc basement may be deformed along the rear of the prism, associated with the onset of collision, but not in the subduction region further to the south.  相似文献   

An Inter-Laboratory Assessment of the Thorium Isotopic Composition of Synthetic and Rock Reference Materials   总被引：2，自引：0，他引：2  

Kenneth W.W. Sims  James B. Gill  Anthony Dosseto  Dirk L. Hoffmann  Craig C. Lundstrom  Ross W. Williams  Lary Ball  Darren Tollstrup  Simon Turner  Julie Prytulak  Justin J.G. Glessner  J.J. Standish  Tim Elliott 《Geostandards and Geoanalytical Research》2008,32(1):65-91

We present a concerted international effort to cross-calibrate five synthetic Th isotope reference materials (UCSC Th "A", OU Th "U", WUN, IRMM-35 and IRMM-36), and six rock reference materials (UCSC TML, Icelandic ATHO, USGS BCR-2, USGS W-2, USGS BHVO-2, LV18) using multi-collector inductively coupled plasma-mass spectrometry (MC-ICP-MS). We then compare our new values with a compilation of literature mass spectrometric data for these reference materials and derive recommended "consensus"²³⁰Th/²³²Th values for each. We also present isotope dilution U and Th concentration data for four rock reference materials (UCSC TML, Icelandic ATHO, USGS BCR-2, USGS W-2).  相似文献   

Simulating Groundwater-Streamflow Connections in the Upper Colorado River Basin     

Hoang Tran  Jun Zhang  Jean-Martial Cohard  Laura E. Condon  Reed M. Maxwell 《Ground water》2020,58(3):392-405

In mountain, snow driven catchments, snowmelt is supposed to be the primary contribution to river streamflows during spring. In these catchments the contribution of groundwater is not well documented because of the difficulty to monitor groundwater in such complex environment with deep aquifers. In this study we use an integrated hydrologic model to conduct numerical experiments that help quantify the effect of lateral groundwater flow on total annual and peak streamflow in predevelopment conditions. Our simulations focus on the Upper Colorado River Basin (UCRB; 2.8 × 10⁵ km²) a well-documented mountain catchment for which both streamflow and water table measurements are available for several important sub-basins. For the simulated water year, our results suggest an increase in peak flow of up to 57% when lateral groundwater flow processes are included—an unexpected result for flood conditions generally assumed independent of groundwater. Additionally, inclusion of lateral groundwater flow moderately improved the model match to observations. The correlation coefficient for mean annual flows improved from 0.84 for the no lateral groundwater flow simulation to 0.98 for the lateral groundwater flow one. Spatially we see more pronounced differences between lateral and no lateral groundwater flow cases in areas of the domain with steeper topography. We also found distinct differences in the magnitude and spatial distribution of streamflow changes with and without lateral groundwater flow between Upper Colorado River Sub-basins. A sensitivity test that scaled hydraulic conductivity over two orders of magnitude was conducted for the lateral groundwater flow simulations. These results show that the impact of lateral groundwater flow is as large or larger than an order of magnitude change in hydraulic conductivity. While our results focus on the UCRB, we feel that these simulations have relevance to other headwaters systems worldwide.  相似文献   

Factors Influencing Adoption and Implementation of Conservation Development Ordinances in Rural United States     

Heidi E. Kretser  Elliot Dale  Leslie Karasin  Liba Pejchar  Sarah E. Reed 《社会与自然资源》2019,32(9):1021-1039

Conservation Development (CD) is a land-use tool to reduce the impacts of development on natural resources, yetthe use of CD is highly variable. We used a collaborative conservation model to examine factors influencing adoption and implementation to improve the future application of CD. We interviewed 2–3 individuals including planners, board members, and developers (n?=?46) from 16 rural communities in the intermountain west and northeast U.S. Motivations to preserve rural character or comply with state statutes drove adoption. Greater capacity such as outside expertise, model regulations, and iterative revisions of ordinances was associated with stronger ordinances. Adoption processes including ample dialog across diverse constituents, especially those overseeing subdivision development, facilitated higher rates of implementation. Concerns over open space management, lack of successful CD examples, and inexperience with CD posed barriers to implementation. Understanding social context revealed the strengths and shortcomings of CD and provided guidance for strategically engaging communities in private lands conservation.  相似文献   

The complete set of ASCA X-ray observations of non-magnetic cataclysmic variables   总被引：1，自引：0，他引：1  

Darren S. Baskill  Peter J. Wheatley  Julian P. Osborne 《Monthly notices of the Royal Astronomical Society》2005,357(2):626-644

We present the complete set of 34 ASCA observations of non-magnetic cataclysmic variables. Timing analysis reveals large X-ray flux variations in dwarf novae in outburst (Z Cam, SS Cyg and SU UMa) and orbital modulation in high inclination systems (including OY Car, HT Cas, U Gem, T Leo). We also found episodes of unusually low accretion rate during quiescence (VW Hyi and SS Cyg). Spectral analysis reveals broad temperature distributions in individual systems, with emission weighted to lower temperatures in dwarf novae in outburst. Absorption in excess of interstellar values is required in dwarf novae in outburst, but not in quiescence. We also find evidence for subsolar abundances and X-ray reflection in the brightest systems.
LS Peg, V426 Oph and EI UMa have X-ray spectra that are distinct from the rest of the sample and all three exhibit candidate X-ray periodicities. We argue that they should be reclassified as intermediate polars.
In the case of V345 Pav we found that the X-ray source had been previously misidentified.  相似文献   

The DEEP2 galaxy redshift survey: evolution of the colour–density relation at  0.4 < z < 1.35      

Michael C. Cooper  Jeffrey A. Newman †  Alison L. Coil †  Darren J. Croton  Brian F. Gerke  Renbin Yan  Marc Davis  S. M. Faber  Puragra Guhathakurta  David C. Koo  Benjamin J. Weiner  Christopher N. A. Willmer ‡ 《Monthly notices of the Royal Astronomical Society》2007,376(4):1445-1459

Using a sample of 19 464 galaxies drawn from the DEEP2 Galaxy Redshift Survey, we study the relationship between galaxy colour and environment at  0.4 < z < 1.35  . We find that the fraction of galaxies on the red sequence depends strongly on local environment out to   z > 1  , being larger in regions of greater galaxy density. At all epochs probed, we also find a small population of red, morphologically early-type galaxies residing in regions of low measured overdensity. The observed correlations between the red fraction and local overdensity are highly significant, with the trend at   z > 1  detected at a greater than 5σ level. Over the entire redshift regime studied, we find that the colour–density relation evolves continuously, with red galaxies more strongly favouring overdense regions at low z relative to their red-sequence counterparts at high redshift. At   z ≳ 1.3  , the red fraction only weakly correlates with overdensity, implying that any colour dependence to the clustering of  ∼ L *  galaxies at that epoch must be small. Our findings add weight to existing evidence that the build-up of galaxies on the red sequence has occurred preferentially in overdense environments (i.e. galaxy groups) at   z ≲ 1.5  . Furthermore, we identify the epoch  ( z ∼ 2)  at which typical  ∼ L *  galaxies began quenching and moved on to the red sequence in significant number. The strength of the observed evolutionary trends at  0 < z < 1.35  suggests that the correlations observed locally, such as the morphology–density and colour–density relations, are the result of environment-driven mechanisms (i.e. 'nurture') and do not appear to have been imprinted (by 'nature') upon the galaxy population during their epoch of formation.  相似文献   

The 2dF Galaxy Redshift Survey: the luminosity function of cluster galaxies     

Roberto De Propris  Matthew Colless  Simon P. Driver  Warrick Couch  John A. Peacock  Ivan K. Baldry  Carlton M. Baugh  Joss Bland-Hawthorn  Terry Bridges  Russell Cannon  Shaun Cole  Chris Collins  Nicholas Cross  Gavin B. Dalton  George Efstathiou  Richard S. Ellis  Carlos S. Frenk  Karl Glazebrook  Edward Hawkins  Carole Jackson  Ofer Lahav  Ian Lewis  Stuart Lumsden  Steve Maddox  Darren S. Madgwick  Peder Norberg  Will Percival  Bruce Peterson  Will Sutherland  Keith Taylor 《Monthly notices of the Royal Astronomical Society》2003,342(3):725-737

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Fossils explained 51     

Darren Naish 《Geology Today》2005,21(6):232-238

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