Nature versus nurture: the curved spine of the galaxy cluster X-ray luminosity–temperature relation     

W. G. Hartley  L. Gazzola  F. R. Pearce  S. T. Kay  P. A. Thomas 《Monthly notices of the Royal Astronomical Society》2008,386(4):2015-2021

The physical processes that define the spine of the galaxy cluster X-ray luminosity–temperature ( L – T ) relation are investigated using a large hydrodynamical simulation of the universe. This simulation models the same volume and phases as the millennium simulation and has a linear extent of  500  h ⁻¹ Mpc  . We demonstrate that mergers typically boost a cluster along but also slightly below the L – T relation. Due to this boost, we expect that all of the very brightest clusters will be near the peak of a merger. Objects from near the top of the L – T relation tend to have assembled much of their mass earlier than an average halo of similar final mass. Conversely, objects from the bottom of the relation are often experiencing an ongoing or recent merger.  相似文献   

Improving the Mellor–Yamada–Janjić Parameterization for wind conditions in the marine planetary boundary layer     

Kay Sušelj  Abha Sood 《Boundary-Layer Meteorology》2010,136(2):301-324

  相似文献   

Development of regional future climate change scenarios in South America using the Eta CPTEC/HadCM3 climate change projections: climatology and regional analyses for the Amazon, S?o Francisco and the Paraná River basins     

Jose A. Marengo  Sin Chan Chou  Gillian Kay  Lincoln M. Alves  José F. Pesquero  Wagner R. Soares  Daniel C. Santos  André A. Lyra  Gustavo Sueiro  Richard Betts  Diego J. Chagas  Jorge L. Gomes  Josiane F. Bustamante  Priscila Tavares 《Climate Dynamics》2012,38(9-10):1829-1848

The objective of this study is to assess the climate projections over South America using the Eta-CPTEC regional model driven by four members of an ensemble of the Met Office Hadley Centre Global Coupled climate model HadCM3. The global model ensemble was run over the twenty-first century according to the SRES A1B emissions scenario, but with each member having a different climate sensitivity. The four members selected to drive the Eta-CPTEC model span the sensitivity range in the global model ensemble. The Eta-CPTEC model nested in these lateral boundary conditions was configured with a 40-km grid size and was run over 1961–1990 to represent baseline climate, and 2011–2100 to simulate possible future changes. Results presented here focus on austral summer and winter climate of 2011–2040, 2041–2070 and 2071–2100 periods, for South America and for three major river basins in Brazil. Projections of changes in upper and low-level circulation and the mean sea level pressure (SLP) fields simulate a pattern of weakening of the tropical circulation and strengthening of the subtropical circulation, marked by intensification at the surface of the Chaco Low and the subtropical highs. Strong warming (4–6°C) of continental South America increases the temperature gradient between continental South America and the South Atlantic. This leads to stronger SLP gradients between continent and oceans, and to changes in moisture transport and rainfall. Large rainfall reductions are simulated in Amazonia and Northeast Brazil (reaching up to 40%), and rainfall increases around the northern coast of Peru and Ecuador and in southeastern South America, reaching up to 30% in northern Argentina. All changes are more intense after 2040. The Precipitation–Evaporation (P–E) difference in the A1B downscaled scenario suggest water deficits and river runoff reductions in the eastern Amazon and S?o Francisco Basin, making these regions susceptible to drier conditions and droughts in the future.  相似文献   

Quantitative Recovery of Elemental Sulfur and Improved Selectivity in a Chromium-Reducible Sulfur Distillation     

Jens Gröger  Jennifer Franke  Kay Hamer  Horst D. Schulz 《Geostandards and Geoanalytical Research》2009,33(1):17-27

Chromium-reducible sulfur (CRS) distillations are intended to recover only reduced inorganic sulfur compounds (RIS) including elemental sulfur. However, the quantitative recovery of elemental sulfur is not ensured in common CRS-distillations. The new method presented here was designed to remedy this deficiency. An increase in ethanol concentration assured the quantitative recovery of elemental sulfur in various forms and, in addition, all other RIS-compounds were quantitatively recovered. Furthermore, the selectivity of the procedure was improved by an additional filtration step to eliminate zinc particles from the Cr(II)-solution. Thus, the recovery of sulfates and organic sulfur compounds was significantly decreased by a factor of up to 35, depending on the compound analysed. Exhaustive testing with a variety of pure phases, rock and soil samples demonstrated the precision and accuracy of the new method. The new protocol eliminated the constraints of previous procedures. The improved distillation efficiency for elemental sulfur ensured the quantitative recovery of all RIS-compounds in a single-step distillation.  相似文献   

Observable blueshifts near compact objects     

Jeffrey M. Cohen  Mitchell F. Struble  Kay R. Pechenick  Boris Kuharetz 《Astrophysics and Space Science》1982,88(2):307-312

We show that observable blueshifted radiation can emanate from material freely falling toward compact objects. Using a fully relativistic treatment and considering possible blocking of photon trajectories by a neutron star or black hole, we demonstrate that blueshifts are observable.Supported in part by the National Science Foundation.  相似文献   

The Racialization of Difference: Enlarging the Story Field     

Kay Anderson 《The Professional geographer》2002,54(1):25-30

In this article, I explore ways of loosening the interpretive grid of “race” in critical geographical analysis without obscuring that concept's efficacy as a social force. In recent years, social constructivist perspectives on race have brought much evidence to bear on the logics of race/power formations in America and other British settler societies. The risk of petrifying “race” in the analysis of social life and reinscribing the very power that antiracists wish to undo has, however, prompted efforts to reframe the geographical study of race and racism. This article takes up that challenge by exploring an alternative modality of representational power that can be tracked to figurations of humanity and animality in Western cultural process. Such discursive formations take us some way toward understanding the norms and interiorised anxieties out of which racialized whiteness and its subjugated others were, and continue to be, constructed.  相似文献   

Trace element and isotopic variations in a zoned pluton and associated volcanic rocks,Unalaska Island,Alaska: A model for fractionation in the Aleutian calcalkaline suite     

Michael R. Perfit  Hannes Brueckner  James R. Lawrence  Robert W. Kay 《Contributions to Mineralogy and Petrology》1980,73(1):69-87

Trace elements, including rare earth elements (REE), exhibit systematic variations in plutonic rocks from the Captains Bay pluton which is zoned from a narrow gabbroic rim to a core of quartz monzodiorite and granodiorite. The chemical variations parallel those in the associated Aleutian calcalkaline volcanic suite. Concentrations of Rb, Y, Zr and Ba increase as Sr and Ti decrease with progressive differentiation. Intermediate plutonic rocks are slightly enriched in light REE (La/Yb=3.45–9.22), and show increasing light REE fractionation and negative Eu anomalies (Eu/Eu^*=1.03–0.584). Two border-zone gabbros have similar REE patterns but are relatively depleted in total REE and have positive Eu anomalies; indicative of their cumulate nature. Initial ⁸⁷Sr/⁸⁶Sr ratios in 8 samples (0.70299 to 0.70377) are comparable to those of volcanic rocks throughout the arc and suggest a mantle source for the magmas. Oxygen isotopic ratios indicate that many of the intermediate plutonic rocks have undergone oxygen isotopic exchange with large volumes of meteoric water during the late stages of crystallization; however no trace element or Sr isotopic alteration is evident.Major and trace element variations are consistent with a model of inward fractional crystallization of a parental high-alumina basaltic magma at low pressures (6 kb). Least-squares approximations and trace element fractionation calculations suggest that differentiation in the plutonic suite was initially controlled by the removal of calcic plagioclase, lesser pyroxene, olivine and Fe-Ti oxides but that with increasing differentiation and water fugacity the removal of sub-equal amounts of sodic plagioclase and hornblende with lesser Fe-Ti oxides effectively drove residual liquids toward dacitic compositions. Major and trace element compositions of aplites which intrude the pluton are not adequately explained by fractional crystallization. They may represent partial melts derived from the island arc crust. Similarities in Sr isotopes, chemical compositions and differentiation trends between the plutonic series and some Aleutian volcanic suites indicates that shallow-level fractional crystallization is a viable mechanism for generating the Aleutian calcalkaline rock series.LDGO Contribution no. 2964  相似文献   

Radioelements,radiogenic helium and age relationships for groundwaters from the granites at Stripa,Sweden   总被引：1，自引：0，他引：1  

J.N Andrews  I.S Giles  R.L.F Kay  D.J Lee  J.K Osmond  J.B Cowart  P Fritz  J.F Barker  J Gale 《Geochimica et cosmochimica acta》1982,46(9):1533-1543

The solution of radioelements and radiogenic ⁴He by groundwaters in fractured rocks is dependent upon the radioelement distribution in the rock matrix and the extent of the rock-water interface. The ${}^{234}\text{U}{}^{238}\text{U}$ activity ratio and the dissolved U, Rn and He contents of such groundwaters respond to changes in the flow regime with time. Although ${}^{234}\text{U}{}^{238}\text{U}$ activity ratios change with groundwater residence time as a consequence of ²³⁴Th-recoil induced solution of ²³⁴U, the activity ratio is strongly influenced by the U distribution within fractures, by the extent of the rock-water interface and by the amount of ²³⁸U in solution. A model for the quantitative evaluation of these effects is presented.Groundwaters from depths up to 880 m in the Stripa granite have variable dissolved uranium contents and ${}^{234}\text{U}{}^{238}\text{U}$ activity ratios. The uranium geochemistry is primarily determined by variations in flow path rather than by groundwater age.Dissolved radiogenic ⁴He in the groundwaters increases with their depth of origin, and is dependent upon the U content of the granite and upon its fracture porosity. It increases with groundwater residence time but movement of ⁴He by diffusion and transport processes make the actual groundwater age indeterminate.  相似文献   

Surface charge evolution of mineral-organic complexes during pedogenesis in Hawaiian basalt     

Jon Chorover  Mary Kay Amistadi 《Geochimica et cosmochimica acta》2004,68(23):4859-4876

Changes in surface charge of soil particles that accompany mineral transformations during soil formation were measured for a humid tropical chronosequence in Hawaiian basalt ranging in lava flow age from 0.3 to 4100 kiloyears (ky). Parent mineralogy is dominated by glass, olivine, pyroxene, and feldspar, whereas poorly crystalline (PC) weathering products (allophane, microcrystalline gibbsite, ferrihydrite) accumulate in early to intermediate weathering stages (through 400 ky), and crystalline secondary minerals (kaolinite, gibbsite, goethite) are dominant in the oldest (1400 and 4100 ky) soils. Detailed characterization of the solid phase was accomplished with chemical extractions, X-ray diffraction analysis, and molecular spectroscopy (FTIR and ¹³C MAS NMR). Simultaneous proton titration and background ion adsorption measurements were made on LiCl saturated soils over a range in pH (2-9) and ionic strength (0.001 and 0.01 M LiCl). Dependence of variable surface charge on solution composition reflects the changing nature of mineral-organic interactions over the course of pedogenesis. Points of zero net proton charge (PZNPC) ranged from 3.4 to 6.2 and 2.0 to 5.8 at 0.001 and 0.01 M ionic strength (I), respectively. Intermediate-aged soils containing the highest mass concentration of humified soil organic matter (SOM) and its complexes with PC minerals gave rise to the steepest charging curves (largest pH dependence) and highest PZNPC values. Surface charge properties of these soils most closely reflected their weakly acidic Al and Fe hydroxide constituents, which is consistent with metal hydroxide saturation of organic functional groups, rather than organic coating of mineral surfaces. Charging curves were less steep and PZNPC values were lower for the older soils, consistent with SOM coating of more crystalline goethite, kaolinite, and gibbsite surfaces in a soil system less impacted by labile Al and Fe.  相似文献   

A stochastic physical system approach to modeling river water quality     

W. F. Curi  T. E. Unny  J. J. Kay 《Stochastic Hydrology and Hydraulics》1995,9(2):117-132

  相似文献