Determining the motion of the Solar system relative to the cosmic microwave background using Type Ia supernovae     

Christopher Gordon  Kate Land  An&#;e Slosar 《Monthly notices of the Royal Astronomical Society》2008,387(1):371-376

We estimate the Solar system motion relative to the cosmic microwave background using Type Ia supernovae (SNe) measurements. We take into account the correlations in the error bars of the SNe measurements arising from correlated peculiar velocities. Without accounting for correlations in the peculiar velocities, the SNe data we use appear to detect the peculiar velocity of the Solar system at about the 3.5σ level. However, when the correlations are correctly accounted for, the SNe data only detect the Solar system peculiar velocity at about the 2.5σ level. We forecast that the Solar system peculiar velocity will be detected at the 9σ level by GAIA and the 11σ level by the Large Synoptic Survey Telescope. For these surveys, we find the correlations are much less important as most of the signal comes from higher redshifts where the number density of SNe is insufficient for the correlations to be important.  相似文献   

The effect of submerged plateaux on Pleistocene gyral circulation and sea-surface temperatures in the Southwest Pacific     

Bruce W. Hayward  George H. Scott  Martin P. Crundwell  James P. Kennett  Lionel Carter  Helen L. Neil  Ashwaq T. Sabaa  Kate Wilson  J. Stuart Rodger  Grace Schaefer  Hugh R. Grenfell  Qianyu Li 《Global and Planetary Change》2008,63(4):309-316

Uniquely in the Southern Hemisphere the New Zealand micro-continent spans the interface between a subtropical gyre and the Subantarctic Circumpolar Current. Its 20° latitudinal extent includes a complex of submerged plateaux, ridges, saddles and basins which, in the present interglacial, are partial barriers to circulation and steer the Subtropical (STF) and Subantarctic (SAF) fronts. This configuration offers a singular opportunity to assess the influence of bottom topography on oceanic circulation through Pleistocene glacial – interglacial (G/I) cycles, its effect on the location and strength of the fronts, and its ability to generate significant differences in mixed layer thermal history over short distances.For this study we use new planktic foraminiferal based sea-surface temperature (SST) estimates spanning the past 1 million years from a latitudinal transect of four deep ocean drilling sites. We conclude that: 1. the effect of the New Zealand landmass was to deflect the water masses south around the bathymetric impediments; 2. the effect of a shallow submerged ridge on the down-current side (Chatham Rise), was to dynamically trap the STF along its crest, in stark contrast to the usual glacial–interglacial (G–I) meridional migration that occurs in the open ocean; 3. the effect of more deeply submerged, downstream plateaux (Campbell, Bounty) was to dynamically trap the SAF along its steep southeastern margin; 4. the effects of saddles across the submarine plateaux was to facilitate the development of jets of subtropical and subantarctic surface water through the fronts, forming localized downstream gyres or eddies during different phases in the G–I climate cycles; 5. the deep Pukaki Saddle across the Campbell-Bounty Plateaux guided a branch of the SAF to flow northwards during each glacial, to form a strong gyre of circumpolar surface water in the Bounty Trough, especially during the mid-Pleistocene Climate Transition (MIS 22-16) when exceptionally high SST gradients existed across the STF; 6. the shallower Mernoo Saddle, at the western end of the Chatham Rise, provided a conduit for subtropical water to jet southwards across the STF in the warmest interglacial peaks (MIS 11, 5.5) and for subantarctic water to flow northwards during glacials; 7. although subtropical or subantarctic drivers can prevail at a particular phase of a G–I cycles, it appears that the Antarctic Circumpolar Current is the main influence on the regional hydrography.Thus complex submarine topography can affect distinct differences in the climate records over short distances with implications for using such records in interpreting global or regional trends. Conversely, the local topography can amplify the paleoclimate record in different ways in different places, thus enhancing its value for the study of more minor paleoceanographic influences that elsewhere are more difficult to detect. Such sites include DSDP 594, which like some other Southern Ocean sites, has the typical late Pleistocene asymmetrical saw-tooth G–I climate pattern transformed to a gap-tooth pattern of quasi-symmetrical interglacial spikes that interrupt extended periods of minimum glacial temperatures.  相似文献   

On the Causes of Electrical Conductivity Anomalies in Tectonically Stable Lithosphere   总被引：2，自引：0，他引：2  

Kate Selway 《Surveys in Geophysics》2014,35(1):219-257

Magnetotelluric (MT) data can image the electrical resistivity of the entire lithospheric column and are therefore one of the most important data sources for understanding the structure, composition and evolution of the lithosphere. However, interpretations of MT data from stable lithosphere are often ambiguous. Recent results from mineral physics studies show that, from the mid-crust to the base of the lithosphere, temperature and the hydrogen content of nominally anhydrous minerals are the two most important controls on electrical conductivity. Graphite films on mineral grain boundaries also enhance conductivity but are stable only to the uppermost mantle. The thermal profile of most stable lithosphere can be well constrained, so the two important unknowns that can affect the conductivity of a lithospheric section are hydrogen content and graphite films. The presence of both of these factors is controlled by the geological history of the lithosphere. Hydrogen in nominally anhydrous minerals behaves as an incompatible element and is preferentially removed during melting or high-temperature tectonothermal events. Grain-boundary graphite films are only stable to ~900 °C so they are also destroyed by high-temperature events. Conversely, tectonic events that enrich the lithosphere in incompatible elements, such as interaction with fluids from a subducting slab or a plume, can introduce both hydrogen and carbon into the lithosphere and therefore increase its electrical conductivity. Case studies of MT results from central Australia and the Slave Craton in Canada suggest that electrical conductivity can act as a proxy for the level of enrichment in incompatible elements of the lithosphere.  相似文献   

DOAS observations of formaldehyde and its impact on the HO<Subscript>x</Subscript> balance in the tropical Atlantic marine boundary layer     

Anoop S. Mahajan  Lisa K. Whalley  Elena Kozlova  Hilke Oetjen  Luis Mendez  Kate L. Furneaux  Andrew Goddard  Dwayne E. Heard  John M. C. Plane  Alfonso Saiz-Lopez 《Journal of Atmospheric Chemistry》2010,66(3):167-178

Measurements of formaldehyde (HCHO) were made at the Cape Verde Atmospheric Observatory between November 2006 and June 2007 using the Long-Path Differential Optical Absorption Spectroscopy (LP-DOAS) technique. Observations show that typical HCHO mixing ratios ranged between 350 and 550 pptv (with typical 2-σ uncertainties of ~110 pptv), with several events of high HCHO, the maximum being 1,885?±?149 pptv. The observations indicate a lack of strong seasonal or diurnal variations, within the uncertainty of the measurements. A box model is employed to test whether the observations can be explained using known hydrocarbon photochemistry; the model replicates well the typical diurnal profile and monthly mean values. The model results indicate that on average 20% of HO₂ production and 10% of OH destruction can be attributed to the mean HCHO levels, suggesting that even at these low average mixing ratios HCHO plays an important role in determining the HO_x (HO₂+OH) balance of the remote marine boundary layer.  相似文献   

Effects of temperature and chemical formulation on the acute toxicity of pentachlorophenol to Simocephalus vetulus (Schoedler, 1858) (Crustacea: Cladocera)     

Kate J. Willis  Nicholas Ling  M. Ann Chapman 《新西兰海洋与淡水研究杂志》2013,47(2):289-294

Abstract

The influence of temperature on the acute toxicity of a technical formulation (86%) and pure formulation (99%) of pentachlorophenol (PCP) to less than 24‐h‐old Simocephalus vetulus neonates was determined with 48‐h static toxicity tests. The technical grade PCP was significantly more toxic to S. vetulus than the pure PCP (P < 0.05). Sensitivity of S. vetulus to technical PCP also significantly increased with temperature (P < 0.05), but a significant temperature effect was not found with the pure PCP. The mean 48‐h LC₅₀ values for neonates exposed to technical PCP were 140 and 199 μg l^?1 at 22°C and 16°C, respectively, and for those exposed to pure PCP were 262 and 304 μg l^?1, respectively.  相似文献   

Variation in sunscreen compounds (mycosporine‐like amino acids) for marine species along a gradient of ultraviolet radiation transmission within doubtful sound,New Zealand     

Miles D. Lamare  Michael P. Lesser  Mike F. Barker  Thomas M. Barry  Kate B. Schimanski 《新西兰海洋与淡水研究杂志》2013,47(5):775-793

We examined the response of four species of New Zealand marine algae (Ecklonia radiata, Apophlaea lyallii, Rhodymenia spp., Ulva lactuca) and a sea urchin (Evechinus chloroticus) to spatial variation in ultraviolet radiation (UV‐R) by examining the concentration of UV‐R absorbing compounds known as mycosporine‐like amino acids (MAAs). The purpose was to understand how, and the degree to which, local marine species could potentially respond to any future increases in incident UV‐R in the New Zealand marine environment. The research was undertaken in Doubtful Sound, where we observed a gradient of water column UV‐R transmission along the 40 km length of the fiord. We examined spatial differences in MAAs along the UV‐B gradient in the macrophytes and temporal changes in MAAs in sea urchin gonads. Among the algae, thallus MAA concentrations (nmol mg^–1 protein) ranged from 12.5 to 87.8 in E. radiata, from 433.1 to 1446.4 in A. lyallii, 12.7 to 103.4 in Rhodymenia spp., but were not detected in U. lactuca. For E. chloroticus, gonadal MAA concentrations ranged from 83.9 to 224.3 nmol mg^–1 protein spatially, and over the year from 1.85 to 14.12 nmol mg^–1 dry weight (DW) depending on site and gametogenic cycle. Laboratory manipulations indicated that concentrations of MAAs in E. chloroticus gonads and eggs are influenced by diet. MAA concentration could be correlated with UV‐B intensities in two of the algal species. E. chloroticus MAA concentrations could also be correlated with UV‐B transmission, which we concluded was a reflection of the greater ingestion and accumulation of MAA‐rich macrophytes at those sites where higher ambient UV‐R induced greater MAA concentrations to occur in the algae. Given this, we suggest that one response of marine species to increases in UV‐B would be an increase in the synthesis and/or accumulation of MAAs for photoautotrophs and a dietary accumulation of those MAAs in E. chloroticus, an important herbivore in this system.  相似文献   

Calculations on the energetics of water dissolution in wadsleyite     

Wright  Kate  Catlow  C. R. A. 《Physics and Chemistry of Minerals》1996,23(1):38-41

Physics and Chemistry of Minerals - Computer simulation techniques are used to investigate the energetics and mechanisms of dissolution of water in the upper mantle mineral wadsleyite (β(Mg,...  相似文献   

Stratigraphic and structural expression of the lateral growth of thrust fault-propagation folds: results and implications from kinematic modelling     

Kate A. Cooper  Stuart Hardy  Rob Gawthorpe 《Basin Research》2003,15(2):165-182

In order to better understand the development of thrust fault‐related folds, a 3D forward numerical model has been developed to investigate the effects that lateral slip distribution and propagation rate have on the fold geometry of pre‐ and syn‐tectonic strata. We consider a fault‐propagation fold in which the fault propagates upwards from a basal decollement and along‐strike normal to transport direction. Over a 1 Ma runtime, the fault reaches a maximum length of 10 km and accumulates a maximum displacement of 1 km. Deformation ahead of the propagating fault tip is modelled using trishear kinematics while backlimb deformation is modelled using kink‐band migration. The applicability of two different lateral slip distributions, namely linear‐taper and block‐taper, are firstly tested using a constant lateral propagation rate. A block‐taper slip distribution replicates the geometry of natural fold‐thrusts better and is then used to test the sensitivity of thrust‐fold morphology to varied propagation rates in a set of fault‐propagation folds that have identical final displacement to length (D_max/L_max) ratios. Two stratigraphic settings are considered: a model in which background sedimentation rates are high and no topography develops, and a model in which a topographic high develops above the growing fold and local erosion, transport and deposition occur. If the lateral propagation rate is rapid (or geologically instantaneous), the fault tips quickly become pinned as the fault reaches its maximum lateral extent (10 km), after which displacement accumulates. In both stratigraphic settings, this leads to strike‐parallel rotation of the syn‐tectonic strata near the fault tips; high sedimentation rates relative to rates of uplift result in along‐strike thinning over the structural high, while low sedimentation rates result in pinchout against it. In contrast, slower lateral propagation rates (i.e. up to one order of magnitude greater than slip rate) lead to the development of along‐strike growth triangles when sedimentation rates are high, whereas when sedimentation rates are low, offflap geometries result. Overall we find that the most rapid lateral propagation rates produce the most realistic geometries. In both settings, time‐equivalent units display both nongrowth and growth stratal geometries along‐strike and the transition from growth to nongrowth has the potential to delineate the time of fault/fold growth at a given location. This work highlights the importance of lateral fault‐propagation and fault tip pinning on fault and fold growth in three dimensions and the complex syn‐tectonic geometries that can result.  相似文献   

A computer simulation study of (OH) defects in olivine     

Kate Wright  C. R. A. Catlow 《Physics and Chemistry of Minerals》1994,20(7):515-518

Recent experiments (Miller et al. 1987; Bell and Rossman 1992; Bai and Kohlstedt 1992) have shown that olivine, the dominant mineral in the Earth's upper mantle, can contain substantial amounts of water in the form of OH. There is uncertainty, however, as to the mechanisms by which water dissolves into the mineral structure and as to the site it occupies in the host lattice. We have therefore used atomistic computer simulation techniques based on the Born model of solids, to investigate the structures and energies of OH defects in olivine. Our calculations suggest that the most favourable route for incorporation of OH into olivine involves reactions with water accompanied by the reduction of ferric iron for which we obtain a solution energy of 0.46 eV. We propose therefore that the OH content will be largely controlled by the concentration of Fe³⁺.  相似文献   

Celebrating a Nation’s heritage on music stamps: Constructing an international community     

Kate Covington  Stanley D. Brunn 《GeoJournal》2006,65(1-2):125-135

Stamps convey important visible messages about a state’s heritage and worldview. They are images or official visible products seen by those living within the state’s borders and those beyond. They also can be considered as “imagined communities,” as like festivals, holidays, or WWW pages, they represent attachments to and images of place. We investigate stamps as elements of visual culture by examining salient music themes and topics from several countries and then focus on the music stamps of Brazil, Hungary, and Senegal. In each case, we examine the number and variety of issues, the importance they place on musical instruments, composers and performers, and musical events.  相似文献