Accretion disc viscosity: how big is alpha?     

A. R. King  J. E. Pringle  M. Livio 《Monthly notices of the Royal Astronomical Society》2007,376(4):1740-1746

We consider observational and theoretical estimates of the accretion disc viscosity parameter α. We find that in thin, fully ionized discs, the best observational evidence suggests a typical range α∼ 0.1–0.4, whereas the relevant numerical simulations tend to derive estimates for α which are an order of magnitude smaller. We discuss possible reasons for this apparent discrepancy.  相似文献   

Zircon     

R.J. King 《Geology Today》2008,24(5):195-198

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How do Canadian media report climate change impacts on health? A newspaper review     

King  Nia  Bishop-Williams  Katherine E.  Beauchamp  Sabrina  Ford  James D.  Berrang-Ford  Lea  Cunsolo  Ashlee  Team  IHACC Research  Harper  Sherilee L. 《Climatic change》2019,152(3-4):581-596

Climatic Change - Research on climate change media coverage is growing. Few studies, however, have investigated how the media portrays climate change impacts on human health. This review,...  相似文献   

Pliocene trace fossils from oyster substrates in the Nijar Basin,Betic Cordillera,southern Spain     

Stephen K. Donovan  Stuart J. Jones  Abigail R. King  David A.T. Harper 《Proceedings of the Geologists' Association. Geologists' Association》2021,132(3):358-368

The Almería-Níjar Basin is a Neogene, intermontane depression marginal to the Mediterranean in southern Spain in the vicinity of El Argamasón, Andalucia. The Pliocene Cuevas Formation rests unconformably on the Upper Messinian rock succession in the Carboneras Fault Zone. The Cuevas Formation is a coarse-grained, bioclastic-rich, calcarenite to calcirudite shoreface deposit. Oysters, namely Saccostrea cucullata (Born), are locally common and preserve a moderate diversity of borings: Caulostrepsis taeniola Clarke; Entobia isp.; Gastrochaenolites isp. aff. G. lapidicus Kelly and Bromley; Maeandropolydora isp. cf. M. sulcans Voigt; Oichnus paraboloides Bromley; and Talpina isp. aff. T. hirsuta Voigt. All represent domiciles except for the predatory O. paraboloides trace. This suite of ichnotaxa is assigned to the Entobia ichnofacies sensu Bromley and Asgaard; they are comparable, particularly, with the Boulder Assemblage of the Pliocene of Rhodes, Greece. Physical disturbance is an important parameter in favouring this pattern of infestation, whether the bored clasts are boulders or oyster valves.  相似文献   

Levelling co-located GNSS and tide gauge stations using GNSS reflectometry     

Alvaro Santamaría-Gómez  Christopher Watson  Médéric Gravelle  Matt King  Guy Wöppelmann 《Journal of Geodesy》2015,89(3):241-258

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Climatic and anthropogenic impacts on the decrease of sediment discharge to the Mediterranean coast from the largest river of Maghreb     

Ali Hadour  Gil Mahé  Mohamed Meddi 《国际泥沙研究》2021,36(2):268-278

The current study focuses on the issue of the decrease in sediment discharge to the Mediterranean Sea by the largest river in Algeria,the Wadi Cheliff(i.e.Cheliff River).This study clarifies the effect of climatic and anthropogenic factors on the changes in the sedimentary dynamics of the Cheliff River discharging to the sea.The data used(rainfall,water discharge,and sediment discharge)concern the Sidi Bel Attar gaging station on the Cheliff River,only 18 km from discharge to the Mediterranean Sea.A power-type statistical regression model was used to fill the 74.2% gap in Suspended Solids(SS)measurements in the establishment of a SS database for the period 1951e2012.The study results show that the transport of suspended sediment discharged to the sea is about 487 t/km^2/yr.Statistical tests of breaks highlight that rainfall decreased by 26% and that water and sediment input to the sea declined from 74%to 63% for the period of 1981e2012.The correlation analysis shows a decrease in the contribution of rainfall on sediment and water input at the outlet equal to 77.9% and 77.8%,respectively,during the period of 1980 e2012,compared to the period of 1968e1980.However,the double mass method reflects the contribution of factors other than rainfall to the decrease of sediment input to the sea.These other factors mainly include large dams,which intercepted about 71%of the total volume of sediment discharged to the sea during the period of 1968e2010.In addition the contribution of large dams to the reduction of sedimentary input to the sea is more important than that of the decrease in rainfall.The management of large dams also contributes to the increase in the sediment deficit to the sea through the prioritization of interception of sediment at the expense of releases,for socio-economic purposes,68.4%of the Cheliff River discharge is diverted for human use.This has led to an increase in the mean water bed level at bankfull downstream,where the Cheliff River gave up 51%of its width to the floodplain between 1996 and 2009.In the light of the scarcity of sediment transport data in North Africa and in many other areas,the current study provides a reference framework for other studies:providing useful information for the study of the transfer of sediment from land to sea,and the links with the socio-economic needs.  相似文献   

Influence of salinity and fish species on PAH uptake from dispersed crude oil     

Ramachandran SD  Sweezey MJ  Hodson PV  Boudreau M  Courtenay SC  Lee K  King T  Dixon JA 《Marine pollution bulletin》2006,52(10):1182-1189

The use of chemical oil dispersants to minimize spill impacts causes a transient increase in hydrocarbon concentrations in water, which increases the risk to aquatic species if toxic components become more bioavailable. The risk of effects depends on the extent to which dispersants enhance the exposure to toxic components, such as polycyclic aromatic hydrocarbons (PAH). Increased salinities can reduce the solubility of PAH and the efficiency of oil dispersants. This study measured changes in the induction of CYP1A enzymes of fish to demonstrate the effect of salinity on PAH availability. Freshwater rainbow trout and euryhaline mummichog were exposed to water accommodated fractions (WAF), and chemically-enhanced water accommodated fractions (CEWAF) at 0 per thousand, 15 per thousand, and 30 per thousand salinity. For both species, PAH exposure decreased as salinity increased whereas dispersant effectiveness decreased only at the highest salinity. Hence, risks to fish of PAH from dispersed oil will be greatest in coastal waters where salinities are low.  相似文献   

A photohabitable zone in the martian snowpack? A laboratory and radiative-transfer study of dusty water-ice snow     

J.L. France  M.D. King 《Icarus》2010,207(1):133-139

Dusty water-ice snowpacks on Mars may provide a habitable zone for DNA based photosynthetic life. Previous work has over estimated the depths and thicknesses of such photohabitable zones by not considering the effect of red dust within the snowpack. For the summer solar solstice, at 80°N and a surface albedo of 0.45, there is a calculated photohabitable zone in the snowpack between depths of 5.5 and 7.5 cm. For an albedo of 0.62, there is a calculated photohabitable zone in the snowpack between depths of 8 and 11 cm. A coupled atmosphere-snow radiative-transfer model was set to model the Photosynthetic Active Radiation and DNA dose rates through water-ice snow at the north polar region of Mars. The optical properties of the polar caps were determined by creating a laboratory analogue to the Mars north polar deposits, and directly measuring light penetration and albedo. It is important for future exobiology missions to the polar regions of Mars to consider the implications of these findings, as drilling to depths of ∼11 cm should be sufficient to determine whether life exists within the martian snows, whether it is photosynthetic or otherwise, as at this depth the snow cover will provide a permanent protection from DNA damaging UV radiation.  相似文献   

Hindered settling velocity of cohesive/non-cohesive sediment mixtures   总被引：1，自引：0，他引：1  

Alan Cuthbertson  Ping Dong  Stuart King  Peter Davies 《Coastal Engineering》2008,55(12):1197-1208

New methods are proposed for predicting the hindered settling conditions encountered by concentrated suspensions containing mixtures of sand particles and mud flocs. These methods, based on two-fraction formulations, are developed by consideration of the settling characteristics of monodisperse and polydisperse solid particle suspensions applied to cohesive/non-cohesive mixtures of mud flocs and sand particles. The behaviour of these predictive methods is evaluated over a wide range of mixture conditions and compared with existing formulations, with their parametric dependence on the relative volumetric concentrations and floc/particle sizes for the mud and sand constituents established. The results indicate that consideration of the full return flow effects generated by both fractions provides the best modelling framework for predicting the hindered settling conditions over a wide range of sand–mud mixtures.  相似文献   

Influences of upwelling and downwelling winds on red tide bloom dynamics in Monterey Bay,California     

John P. Ryan  Andrew M. Fischer  Raphael M. Kudela  James F.R. Gower  Stephanie A. King  Roman Marin  Francisco P. Chavez 《Continental Shelf Research》2009,29(5-6):785-795

It has recently been shown that inner shelf waters of NE Monterey Bay, California function as an “extreme bloom incubator”, frequently developing dense “red tide” blooms that can rapidly spread. Located within the California Current upwelling system, this open bay is strongly influenced by oceanographic dynamics resulting from cycles of upwelling favorable winds and their relaxation and/or reversal. Different wind forcing causes influx of different water types that originate outside the bay: cold nutrient-rich waters during upwelling and warm nutrient-poor waters during relaxation. In this study, we examine how the bay's bloom incubation area can interact with highly variable circulation to cause red tide spreading, dispersal and retention. This examination of processes is supported by satellite, airborne and in situ observations of a major dinoflagellate bloom during August and September of 2004. Remote sensing of high spatial, temporal and spectral resolution shows that the bloom originated in the NE bay, where it was highly concentrated in a narrow band along a thermal front. Upwelling circulation rapidly spread part of the bloom, mixing cool waters of an upwelling filament with warm bloom source waters as they spread. Vertical migration of the dinoflagellate populations was mapped by autonomous underwater vehicle surveys through the spreading bloom. Following bloom expansion, a two-day wind reversal forced intrusion of warm offshore waters that dispersed much of the bloom. Upwelling winds then resumed, and the bloom was further dispersed by an influx of cold water. Throughout these oceanographic responses to changing winds, an intense bloom persisted in sheltered waters of the NE bay, where extreme blooms are most frequent and intense. Microscopic examination of surface phytoplankton samples from the central bay showed that spreading of the bloom from the NE bay and mixing with regional water masses resulted in significantly increased abundance of dinoflagellates and decreased abundance of diatoms. Similar dinoflagellate bloom incubation sites are indicated in other areas of the California Current system and other coastal upwelling systems. Through frequent bloom development and along-coast transports, relatively small incubation sites may significantly influence larger regions of the coastal marine ecosystems in which they reside.  相似文献