Critical mass transfer in double-degenerate Type Ia supernovae     

Rebecca G. Martin  Christopher A. Tout  Pierre Lesaffre 《Monthly notices of the Royal Astronomical Society》2006,373(1):263-270

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The white dwarf in AE Aqr brakes harder     

Christopher W. Mauche 《Monthly notices of the Royal Astronomical Society》2006,369(4):1983-1987

Taking advantage of the very precise de Jager et al. optical white dwarf orbit and spin ephemerides; ASCA , XMM–Newton and Chandra X-ray observations spread over 10 yr; and a cumulative 27-yr baseline, we have found that in recent years the white dwarf in AE Aqr is spinning down at a rate that is slightly faster than predicted by the de Jager et al. spin ephemeris. At the present time, the observed period evolution is consistent with either a cubic term in the spin ephemeris with     , which is inconsistent in sign and magnitude with magnetic dipole radiation losses, or an additional quadratic term with     , which is consistent with a modest increase in the accretion torques spinning down the white dwarf. Regular monitoring, in the optical, ultraviolet and/or X-rays, is required to track the evolution of the spin period of the white dwarf in AE Aqr.  相似文献   

Detection of large-scale intrinsic ellipticity–density correlation from the Sloan Digital Sky Survey and implications for weak lensing surveys     

Rachel Mandelbaum  Christopher M. Hirata  Mustapha Ishak  Uro&#; Seljak  Jonathan Brinkmann 《Monthly notices of the Royal Astronomical Society》2006,367(2):611-626

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The influence of radio galaxy activity on X-ray absorption lines from the intracluster medium     

Franziska Köckert  Christopher S. Reynolds 《Monthly notices of the Royal Astronomical Society》2006,368(2):668-676

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Large-scale slope failure involving Triassic and Middle Miocene salt and shale in the Gulf of Cádiz (Atlantic Iberian Margin)     

Adolfo Maestro  Luis Somoza  Teresa Medialdea  Christopher J. Talbot  Allen Lowrie  Juan T. Vázquez  V. Díaz-del-Río 《地学学报》2003,15(6):380-391

Sheets of salt and ductile shale advancing beyond the thrust front of the Gibraltar Arc (Iberian–Moroccan Atlantic continental margin) triggered downslope movements of huge allochthonous masses. These allochthons represent the Cádiz Nappe, which detached from the Gibraltar Arc along low‐angle normal faults and migrated downslope from the Iberian and Moroccan continental margins towards the Atlantic Ocean. Extensional tectonics initiated upslope salt withdrawal and downslope diapirism during large‐scale westward mass wasting from the shelf and upper slope. Low‐angle salt and shale detachments bound by lateral ramps link extensional structures in the shelf to folding, thrusting and sheets of salt and shale in the Gulf of Cádiz. From backstripping analyses carried out on the depocentres of the growth‐fault‐related basins on the shelf, we infer two episodes of rapid subsidence related to extensional collapses; these were from Late Tortonian to Late Messinian (200–400 m Myr^?1) and from Early Pliocene to Late Pliocene (100–150 m Myr^?1). The extensional events that induced salt movements also affected basement deformation and were, probably, associated with the westward advance of frontal thrusts of the Gibraltar Arc as a result of the convergence between Africa and Eurasia. The complexities of salt and/or shale tectonics in the Gulf of Cádiz result from a combination of the deformations seen at convergent and passive continental margins.  相似文献   

A new synthetic model for asymptotic giant branch stars     

Robert G. Izzard  Christopher A. Tout  Amanda I. Karakas  Onno R. Pols 《Monthly notices of the Royal Astronomical Society》2004,350(2):407-426

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Testing variations within the Tagish Lake meteorite—II: Whole‐rock geochemistry of pristine samples     

Alexandra I. Blinova  Christopher D. K. Herd  M. John M. Duke 《Meteoritics & planetary science》2014,49(6):1100-1118

Four pristine specimens of the Tagish Lake C2 chondrite meteorite were previously determined through mineralogy, petrology, and organic chemistry to have been affected by aqueous alteration in the order (from least to most altered) TL5b < TL11h < TL11i, and TL11v as a mixture of the other specimens (Herd et al. 2011 ; Blinova et al. 2014 ). Here, we report the whole‐rock data for a total of 65 elements for the same four Tagish Lake samples as determined by ICP‐MS and ICP‐AES (utilizing the Parr bomb digestion method on small samples, approximately 50 mg), and by INAA. Our data demonstrate that the determined aqueous alteration sequence has a positive correlation with trace elements, such as K and Br that are mobile during aqueous alteration, which appear to be controlled by an increase of phyllosilicates from least to most altered samples. Yet, the homogeneity of other elements suggests that elemental mass transfer occurred on a localized scale and aqueous alteration was isochemical for these elements, similar to other primitive carbonaceous chondrites. By plotting data from three samples (TL5b, TL11h, and TL11i) on a Zn/Mn versus Sc/Mn diagram, we also confirm that the Tagish Lake meteorite is not a simple mixture of CI and CM material.  相似文献   

Developing seasonal rainfall scenarios for food security early warning     

Gregory J. Husak  Christopher C. Funk  Joel Michaelsen  Tamuka Magadzire  Kirk P. Goldsberry 《Theoretical and Applied Climatology》2013,114(1-2):291-302

Rainfed agriculture in Sub-Saharan Africa accounts for 95 % of the local cereal production, impacting hundreds of millions of people. Early identification of poor rainfall conditions is a critical indicator of food security. As such, monitoring accumulated seasonal rainfall gives an important mid-season estimate of final accumulated totals. However, characterizing the remaining uncertainty in a season has largely been ignored by the food security community. This paper presents a new technique describing rainfall conditions over the duration of a crop-growing cycle by combining estimated rainfall-to-date with potential scenarios for the remaining season based on available satellite rainfall estimates, the common tool for rainfall analysis in Africa. The limited historical record provided by satellite rainfall estimates using previous seasons provides only a coarse view of likely seasonal totals. To combat this, scenarios developed by bootstrapping dekadal data to create synthetic seasons allow for a finer understanding of potential seasonal accumulations. Updating this throughout the season shows a narrowing envelope of seasonal totals, converging on the final seasonal result. The resulting scenarios inform the expectations for the final seasonal rainfall accumulation, allowing analysts to quantify and visualize the uncertainty in seasonal totals. Giving decision makers a tool for understanding the likelihood of specific rainfall amounts provides additional time to enact and mobilize efforts to reduce the impact of agricultural drought.  相似文献   

Sea‐level response at Nain,Labrador, to atmospheric pressure and wind     

Christopher Garrett  Fouad Majaess  Bechara Toulany 《大气与海洋》2013,51(2):95-117

Abstract

Two years of subtidal sea‐level data from Nain, Labrador, are analysed in terms of local atmospheric pressure and the two components of geostrophic wind or stress. Frequency‐dependent response coefficients are determined by multiple regression analysis involving inversion of the cross‐spectral matrix of the inputs. At very low frequencies the response to pressure is isostatic and the wind stress coefficients are consistent with those determined by Thompson et al. (1985) from analysis of a longer series of monthly means. There is very little change in the response between icy and ice‐free seasons. The wind, or stress, coefficients correspond to geostrophic set‐up by a narrow longshore current but do not show as much of an increase of phase lag with increasing frequency as expected. The pressure response is less than isostatic and lags as the frequency increases from zero to about 0.02 cph. Possible reasons for this are discussed. Removal of wind as well as pressure effects ffom the sea‐level data makes only minor changes to the monthly mean residual sea‐level.  相似文献   

Simulating the impact of the large-scale circulation on the 2-m temperature and precipitation climatology     

Jared H. Bowden  Christopher G. Nolte  Tanya L. Otte 《Climate Dynamics》2013,40(7-8):1903-1920

The impact of the simulated large-scale atmospheric circulation on the regional climate is examined using the Weather Research and Forecasting (WRF) model as a regional climate model. The purpose is to understand the potential need for interior grid nudging for dynamical downscaling of global climate model (GCM) output for air quality applications under a changing climate. In this study we downscale the NCEP-Department of Energy Atmospheric Model Intercomparison Project (AMIP-II) Reanalysis using three continuous 20-year WRF simulations: one simulation without interior grid nudging and two using different interior grid nudging methods. The biases in 2-m temperature and precipitation for the simulation without interior grid nudging are unreasonably large with respect to the North American Regional Reanalysis (NARR) over the eastern half of the contiguous United States (CONUS) during the summer when air quality concerns are most relevant. This study examines how these differences arise from errors in predicting the large-scale atmospheric circulation. It is demonstrated that the Bermuda high, which strongly influences the regional climate for much of the eastern half of the CONUS during the summer, is poorly simulated without interior grid nudging. In particular, two summers when the Bermuda high was west (1993) and east (2003) of its climatological position are chosen to illustrate problems in the large-scale atmospheric circulation anomalies. For both summers, WRF without interior grid nudging fails to simulate the placement of the upper-level anticyclonic (1993) and cyclonic (2003) circulation anomalies. The displacement of the large-scale circulation impacts the lower atmosphere moisture transport and precipitable water, affecting the convective environment and precipitation. Using interior grid nudging improves the large-scale circulation aloft and moisture transport/precipitable water anomalies, thereby improving the simulated 2-m temperature and precipitation. The results demonstrate that constraining the RCM to the large-scale features in the driving fields improves the overall accuracy of the simulated regional climate, and suggest that in the absence of such a constraint, the RCM will likely misrepresent important large-scale shifts in the atmospheric circulation under a future climate.  相似文献