A UK perspective on the development of marine ecosystem indicators   总被引：4，自引：0，他引：4  

Rogers SI  Greenaway B 《Marine pollution bulletin》2005,50(1):9-19

This paper reviews the suite of marine ecosystem indicators currently in use or under development in the UK to support the major national and international biodiversity and ecosystem policies. Indicators apply to a range of different ecosystem components, and range from those that can only be used for high level environmental health monitoring, to those which actively support management. Assessment of indicators against a management framework of driving force, pressure, state, impact and response, has shown that there are many indicators of state for ecosystem components, but relatively few for pressure of human activities on the environment, or of the socio-economic response to those pressures. This outcome, a result of unplanned sectorally driven indicator development, is not a co-ordinated contribution to marine environmental management and must be addressed if we are to avoid high monitoring costs and duplication of effort.  相似文献   

Tectonic significance of Late Neoproterozoic granites from the Tibesti massif in southern Libya inferred from Sr and Nd isotopes and U–Pb zircon data   总被引：1，自引：0，他引：1  

Ismail B. Suayah  Jonathan S. Miller  Brent V. Miller  Tovah M. Bayer  John J.W. Rogers   《Journal of African Earth Sciences》2006,44(4-5):561

The Neoproterozoic crust of the Tibesti massif was stabilized by magmatism that included subduction-generated batholithic suites and post-orogenic granite plutons. All of the magmatism occurred in a period of about 20 million years centered around 550 Ma, and nearly all of the granites have initial ⁸⁷Sr/⁸⁶Sr ratios of about 0.706. The Wadi Yebigue pluton has U–Pb zircon ages of 563 Ma and 558 Ma on two different phases and ε_Nd at 550 Ma from −0.5 to −2.2. These isotopic data and the geologic history of the massif suggest that granites in the Tibesti massif developed during and shortly after closure of a short-lived ocean basin that developed by fragmentation of pre-existing continental crust of the Saharan region.  相似文献   

Assessing the suitability of OSPAR EcoQOs for eutrophication vs ICES criteria for England and Wales     

Painting SJ  Devlin MJ  Rogers SI  Mills DK  Parker ER  Rees HL 《Marine pollution bulletin》2005,50(12):1569-1584

This paper provides a preliminary evaluation of the suitability of OSPAR Ecological Quality objectives for eutrophication for coastal and offshore waters of England and Wales on the basis of ICES criteria. In principle, EcoQOs are easy to understand, but responses to nutrient enrichment are complex. Few studies provide unequivocal evidence of links between inputs and response. Monitoring is generally feasible and in place, but needs to be improved. The best EcoQO is winter nutrient concentrations. Chlorophyll concentrations are a good indicator in environments susceptible to nutrient enrichment. The EcoQO for zoobenthos/fish kills potentially meets all criteria for a good indicator; EcoQOs for phytoplankton indicator species, oxygen concentrations and zoobenthos changes do not. Greater emphasis needs to be placed on seasonal effects of nutrient inputs and phytoplankton response, natural susceptibility of different water bodies, differences between coastal and offshore environments, and developing longer time series of data.  相似文献   

Associations of Vertebrate Skeletal Concentrations and Discontinuity Surfaces in Terrestrial and Shallow Marine Records: A Test in the Cretaceous of Montana     

Rogers RR  Kidwell SM 《The Journal of geology》2000,108(2):131-154

Although lags of bones and teeth are commonly cited criteria for marine unconformities, the consistency of the association of vertebrate fossils and discontinuity surfaces, as well as the taphonomic (postmortem) controls on this relationship, are poorly understood. A field test across fluvial, paralic, and shallow marine facies in the Campanian Two Medicine and Judith River formations of Montana indicates that the distribution of vertebrate skeletal concentrations is poorly correlated with the inferred durations of erosional and omissional hiatuses. Instead, vertebrate concentrations associated with discontinuities of all durations tend to be patchy and closely track the abundance of fossil material in underlying and lateral facies. Based on the analysis of 83 measured sections, we found first that erosional bases of channels and minor scours within channels yield vertebrate lags; tidally influenced fluvial deposits are more productive than are "upland" fluvial deposits. Second, erosional shoreface ravinements and their correlative transgressive marine flooding surfaces (fourth-order sequence boundaries) have well-developed vertebrate lags only along segments that cut across older shoreface deposits. Third, a nonerosional, widely traceable discontinuity, which is interpreted as the nonmarine extension of a 75.4-Ma third-order transgressive surface, is completely lacking in vertebrate concentrations. Despite being unfossiliferous itself, this discontinuity does mark a regional change in the richness of the vertebrate fossil record, with overlying beds characterized by a much greater abundance of skeletal material. Fourth, a laterally extensive set of erosional surfaces, embedded within multistory fluvial sandstone sheets, is the nonmarine extension of an 80-Ma third-order sequence boundary in the marine basin and lacks vertebrate concentrations. The strong dependence of vertebrate lag development on preexisting local sources of skeletal material rather than on the magnitude of the erosional vacuity or the duration of the hiatus contrasts with skeletal concentrations of invertebrates in marine successions, where exhumation is generally much less important than the production of new elements during the hiatus. These findings provide a guide to prospecting productive fossil horizons in terrestrial records and underscore fundamental differences in the ways in which bioclastic material accumulates in terrestrial and shallow marine settings, the qualities of paleobiologic data derived from such concentrations, and the relative reliabilities of skeletal material as cues to stratigraphically significant discontinuities.  相似文献   

Cyclic variations in the angular diameter of χ Cygni     

J. S. Young  J. E. Baldwin  R. C. Boysen  C. A. Haniff  D. Pearson  J. Rogers  D. St-Jacques  †  P. J. Warner  D. M. A. Wilson 《Monthly notices of the Royal Astronomical Society》2000,318(2):381-386

We report the direct detection of cyclic diameter variations in the Mira variable χ Cygni. Interferometric observations made between 1997 July and 1999 September, using the Cambridge Optical Aperture Synthesis Telescope (COAST) and the William Herschel Telescope (WHT), indicate periodic changes in the apparent angular diameter at a wavelength of 905 nm, with amplitude 45 per cent of the smallest value. The star appears largest at minimum light. Measurements made at a wavelength of 1.3 μm over the same period suggest much smaller size changes. This behaviour is consistent with a model in which most of the apparent diameter variation at 905 nm is caused by a large increase in the opacity of the outer atmospheric layers (which is mostly owing to titanium oxide) near minimum light, rather than by physical motions of the photosphere. The 1.3-μm waveband is relatively uncontaminated by TiO, and so much smaller size changes would be expected in this band. The latest non-linear pulsational models predict maximum physical size close to maximum light, and increases in opacity near minimum light that are too small to reproduce the diameter variation seen at 905 nm. This suggests either that the phase-dependence of the model pulsation is incorrect, or that the opacities in the models are underestimated. Future interferometric monitoring in uncontaminated near-infrared wavebands should resolve this question.  相似文献   

Volumetric Fracture Intensity Measurement for Improved Rock Mass Characterisation and Fragmentation Assessment in Block Caving Operations     

S. Rogers  D. Elmo  G. Webb  A. Catalan 《Rock Mechanics and Rock Engineering》2015,48(2):633-649

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Gaseous electron multiplier gain characteristics using low-pressure Ar/CO<Subscript>2</Subscript>     

T. Rogers  R. McEntaffer  T. Schultz  J. McCoy  D. Miles  J. Tutt 《Experimental Astronomy》2017,43(2):201-210

Gaseous Electron Multiplier detectors, or GEMs, show promise for use on space-based X-ray missions. Operating pressure strongly affects the gain of the detector and must be optimized for best performance. We have measured the gain characteristics of a GEM detector at various pressures below atmosphere using a mixture of Ar:CO₂ with the goal of maximizing gain to push GEM capabilities to the lowest energies possible. This paper discusses our tests, results, and their implications for choosing a detector pressure. We found that at any operating pressure the detector voltage can be adjusted to achieve roughly the same maximum gain prior to the onset of electrical discharges. We also find that the gain varies substantially by spatial location across the detector, but this variation is insensitive to changes in pressure allowing it to be calibrated and corrected if necessary. The detector pressure can therefore be optimized in the interest of other performance parameters such as leak rate, window stress, power requirements, or quantum efficiency without concern for negatively affecting the gain. These results can inform the choice of operating pressure and voltage for GEMs used onboard future space missions.  相似文献   

An elementary parcel model with explicit condensation and supersaturation     

R.R. Rogers 《大气与海洋》2013,51(4):192-204

The development of droplet size, supersaturation, and temperature in an ascending, unmixed parcel of cloudy air was investigated using a numerical model in which condensation and supersaturation are explicitly calculated. Of particular interest was the steady‐state value which the super‐saturation attains, and the time required to reach this value. The results were found to be in reasonable agreement with an approximate analytical solution of the equations that predicts a steady‐state supersaturation equal to G(p, T)U/vr, where G(p, T) is a known thermodynamic function of temperature and pressure, U is the updraft speed (assumed constant), v is the number of droplets per unit mass of air (assumed constant), and r is the droplet radius. The approach to this limiting value is very nearly exponential, with a time constant equal to G(p, T)/Q ₁ vr, where Q ₁ is a function of temperature. Without giving up the possibility of approximate analytical solutions, the equations can be elaborated to allow an accelerating updraft or to simulate the effects of rapid droplet coalescence.  相似文献   

An automated superconducting magnetometer and demagnetizing system     

J. Shaw  J. A. Share  J. Rogers 《Geophysical Journal International》1984,78(1):209-217

Summary. A novel 3-axis superconducting magnetometer has been constructed using just one SQUID (Superconducting Quantum Interference Device) sensor. The magnetometer has been placed in a large mu-metal shield together with a non-magnetic oven and 3-axis af demagnetizer. Once a sample is entered into the system a microprocessor controller executes a predetermined measuring and demagnetizing/remagnetizing sequence. The system was originally designed automatically to determine field magnitude values from ceramics and igneous rocks but has proved itself to be a useful general purpose palaeomagnetic instrument.  相似文献   

A Complex Petrogenesis for an Arc Magmatic Suite, St Kitts, Lesser Antilles   总被引：2，自引：0，他引：2  

Toothill  J.; Williams  C. A.; MacDonald  R.; Turner  S. P.; Rogers  N. W.; Hawkesworth  C. J.; Jerram  D. A.; Ottley  C. J.; Tindle  A. G. 《Journal of Petrology》2007,48(1):3-42

St Kitts forms one of the northern group of volcanic islandsin the Lesser Antilles arc. Eruptive products from the Mt Liamuigacentre are predominantly olivine + hypersthene-normative, low-Kbasalts through basaltic andesites to quartz-normative, low-Kandesites. Higher-Al and lower-Al groups can be distinguishedin the suite. Mineral assemblages include olivine, clinopyroxene,orthopyroxene, plagioclase and titanomagnetite with rarer amphibole,ilmenite and apatite. Eruptive temperatures of the andesitesare estimated as 963–950°C at fO₂ NNO + 1 (whereNNO is the nickel–nickel oxide buffer). Field and mineralchemical data provide evidence for magma mixing. Glass (melt)inclusions in the phenocrysts range in composition from andesiteto high-silica rhyolite. Compositional variations are broadlyconsistent with the evolution of more evolved magmas by crystalfractionation of basaltic parental magmas. The absence of anycovariation between ⁸⁷Sr/⁸⁶Sr or ¹⁴³Nd/¹⁴⁴Nd and SiO₂ rulesout assimilation of older silicic crust. However, positive correlationsbetween Ba/La, La/Sm and ²⁰⁸Pb/²⁰⁴Pb and between ²⁰⁸Pb/²⁰⁴Pband SiO₂ are consistent with assimilation of small amounts (<10%)of biogenic sediments. Trace element and Sr–Nd–Pbisotope data suggest derivation from a normal mid-ocean ridgebasalt (N-MORB)-type mantle source metasomatized by subductedsediment or sediment melt and fluid. The eruptive rocks arecharacterized by ²³⁸U excesses that indicate that fluid additionof U occurred <350 kyr ago; U–Th isotope data for mineralseparates are dominated by melt inclusions but would allow crystallizationages of 13–68 ka. However, plagioclase is consistentlydisplaced above these ‘isochrons’, with apparentages of 39–236 ka, and plagioclase crystal size distributionsare concave-upwards. These observations suggest that mixingprocesses are important. The presence of ²²⁶Ra excesses in twosamples indicates some fluid addition <8 kyr ago and thatthe magma residence times must also have been less than 8 kyr. KEY WORDS: Sr–Nd–Pb isotopes; U-series isotopes; crystal size distribution; petrogenesis  相似文献