Variations in the biomass of Antarctic krill (Euphausia superba) around the South Shetland Islands, 1996-2006   总被引：1，自引：0，他引：1  

Reiss  Christian S.; Cossio  Anthony M.; Loeb  Valerie; Demer  David A. 《ICES Journal of Marine Science》2008,65(4):497-508

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Latin America: Contesting extraction, producing geographies   总被引：3，自引：3，他引：0  

Anthony Bebbington 《Singapore journal of tropical geography》2009,30(1):7-12

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Tectonic evolution of the Cape and Karoo basins of South Africa   总被引：1，自引：0，他引：1  

Anthony Tankard  Herman Welsink  Peter Aukes  Robert Newton  Edgar Stettler 《Marine and Petroleum Geology》2009,26(8):1379-1412

The Cape and Karoo basins formed within the continental interior of Gondwana. Subsidence resulted from the vertical motion of rigid basement blocks and intervening crustal faults. Each basin episode records a three-stage evolution consisting of crustal uplift, fault-controlled subsidence, and long periods of regional subsidence largely unaccompanied by faulting or erosional truncation. The large-scale episodes of subsidence were probably the result of lithospheric deflection due to subduction-driven mantle flow. The early Paleozoic Cape basin records the combined effects of a north-dipping intra-crustal décollement (a late Neoproterozoic suture) and a right-stepping offset between thick Rio de la Plata craton and Namaqua basement. Following the Saldanian orogeny, a suite of small rift basins and their post-rift drape formed at this releasing stepover. Great thicknesses of quartz sandstone (Ordovician–Silurian) and mudstone (Devonian) accumulation are attributed to subsidence by rheological weakening and mantle flow. In contrast, the Karoo basin is a cratonic cover that mimics the underlying basement blocks. The Permian Ecca and lower Beaufort groups were deposited in a southward-deepening ramp syncline by extensional decoupling on the intra-crustal décollement. Reflection seismic and deep-burial diagenetic studies indicate that the Cape orogeny started in the Early Triassic. Deformation was partitioned into basement-involved strike-slip faults and thin-skinned thrusting. Uplift of the Namaqua basement resulted in erosion of the Beaufort cover. East of the Cape fold belt, contemporaneous subsidence and tilting of the Natal basement created a late Karoo transtensional foreland basin, the Stormberg depocentre. Early Jurassic tectonic resetting and continental flood basalts terminated the Karoo basin.  相似文献   

Direct impacts of alternative energy scenarios on water demand in the Middle East and North Africa   总被引：1，自引：1，他引：0  

Kerstin Damerau  Oscar P. R. van Vliet  Anthony G. Patt 《Climatic change》2015,130(2):171-183

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Projected changes in diverse ecosystems from climate warming and biophysical drivers in northwest Alaska     

Mark Torre Jorgenson  Bruce G. Marcot  David K. Swanson  Janet C. Jorgenson  Anthony R. DeGange 《Climatic change》2015,130(2):131-144

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The Wide Field Spectrograph (WiFeS): performance and data reduction     

Michael Dopita  Jonghwan Rhee  Catherine Farage  Peter McGregor  Gabe Bloxham  Anthony Green  Bill Roberts  Jon Neilson  Greg Wilson  Peter Young  Peter Firth  Gianni Busarello  Paola Merluzzi 《Astrophysics and Space Science》2010,327(2):245-257

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Exchange of ejecta between Telesto and Calypso: Tadpoles, horseshoes, and passing orbits     

Anthony R. Dobrovolskis  José Luis Alvarellos  Jack J. Lissauer 《Icarus》2010,210(1):436-445

We have numerically integrated the orbits of ejecta from Telesto and Calypso, the two small Trojan companions of Saturn’s major satellite Tethys. Ejecta were launched with speeds comparable to or exceeding their parent’s escape velocity, consistent with impacts into regolith surfaces. We find that the fates of ejecta fall into several distinct categories, depending on both the speed and direction of launch.The slowest ejecta follow suborbital trajectories and re-impact their source moon in less than one day. Slightly faster debris barely escape their parent’s Hill sphere and are confined to tadpole orbits, librating about Tethys’ triangular Lagrange points L₄ (leading, near Telesto) or L₅ (trailing, near Calypso) with nearly the same orbital semi-major axis as Tethys, Telesto, and Calypso. These ejecta too eventually re-impact their source moon, but with a median lifetime of a few dozen years. Those which re-impact within the first 10 years or so have lifetimes near integer multiples of 348.6 days (half the tadpole period).Still faster debris with azimuthal velocity components ?10 m/s enter horseshoe orbits which enclose both L₄ and L₅ as well as L₃, but which avoid Tethys and its Hill sphere. These ejecta impact either Telesto or Calypso at comparable rates, with median lifetimes of several thousand years. However, they cannot reach Tethys itself; only the fastest ejecta, with azimuthal velocities ?40 m/s, achieve “passing orbits” which are able to encounter Tethys. Tethys accretes most of these ejecta within several years, but some 1% of them are scattered either inward to hit Enceladus or outward to strike Dione, over timescales on the order of a few hundred years.  相似文献   

Assessment of the resonant perturbation errors in Galilean satellite ephemerides using precisely measured eclipse times     

Anthony Mallama  Chris Stockdale 《Icarus》2010,210(1):346-357

Astrometric satellite positions are derived from timings of their eclipses in the shadow of Jupiter. The 548 data points span 20 years and are accurate to about 0.006 arcsec for Io and Europa and about 0.015 arcsec or better for Ganymede and Callisto. The precision of the data set and its nearly continuous distribution in time allows measurement of regular oscillations with an accuracy of 0.001 arcsec. This level of sensitivity permits detailed evaluation of modern ephemerides and reveals anomalies at the 1.3 year period of the resonant perturbations between Io, Europa and Ganymede. The E5 ephemeris shows large errors at that period for all three satellites as well as other significant anomalies. The L1 ephemeris fits the observations much more closely than E5 but discrepancies for the resonant satellites are still apparent and the measured positions of Io are drifting away from the predictions. The JUP230 ephemeris fits the observations more accurately than L1 although there is still a measurable discordance between the predictions and observations for Europa at the resonance period.  相似文献   

A hybrid artificial neural network-numerical model for ground water problems     

Szidarovszky F  Coppola EA  Long J  Hall AD  Poulton MM 《Ground water》2007,45(5):590-600

Numerical models constitute the most advanced physical-based methods for modeling complex ground water systems. Spatial and/or temporal variability of aquifer parameters, boundary conditions, and initial conditions (for transient simulations) can be assigned across the numerical model domain. While this constitutes a powerful modeling advantage, it also presents the formidable challenge of overcoming parameter uncertainty, which, to date, has not been satisfactorily resolved, inevitably producing model prediction errors. In previous research, artificial neural networks (ANNs), developed with more accessible field data, have achieved excellent predictive accuracy over discrete stress periods at site-specific field locations in complex ground water systems. In an effort to combine the relative advantages of numerical models and ANNs, a new modeling paradigm is presented. The ANN models generate accurate predictions for a limited number of field locations. Appending them to a numerical model produces an overdetermined system of equations, which can be solved using a variety of mathematical techniques, potentially yielding more accurate numerical predictions. Mathematical theory and a simple two-dimensional example are presented to overview relevant mathematical and modeling issues. Two of the three methods for solving the overdetermined system achieved an overall improvement in numerical model accuracy for various levels of synthetic ANN errors using relatively few constrained head values (i.e., cells), which, while demonstrating promise, requires further research. This hybrid approach is not limited to ANN technology; it can be used with other approaches for improving numerical model predictions, such as regression or support vector machines (SVMs).  相似文献   

Development of a benthic index to assess sediment quality in the Tampa Bay Estuary   总被引：1，自引：0，他引：1  

Malloy KJ  Wade D  Janicki A  Grabe SA  Nijbroek R 《Marine pollution bulletin》2007,54(1):22-31

The identification, remedial treatment, and monitoring of contaminated sediments are among the priorities for managers of the Tampa Bay Estuary. Tampa Bay, as an urbanized estuary, is subject to the input of watershed sources of chemical contaminants, including metals, pesticides, and organic chemicals. Although the use of biological indicators and their incorporation into multi-metric indices is not new, the refinement and applications of such techniques for determining environmental condition still require further development and exploration. We present a single Tampa Bay Benthic Index (TBBI) that was developed specifically for Tampa Bay. Stepwise discriminant analysis was applied to a comprehensive list of potential benthic metrics. Results from the stepwise procedure identified the metrics that best discriminated between "healthy" and "degraded" conditions, as defined by sediment contaminant effect levels and dissolved oxygen. Discriminant analysis was then applied to the resultant three variables to determine the linear combination for the index.  相似文献