The star formation histories of elliptical galaxies across the Fundamental Plane     

L. A. Nolan  J. S. Dunlop  B. Panter  Raul Jimenez  A. Heavens  G. Smith 《Monthly notices of the Royal Astronomical Society》2007,375(1):371-380

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Vulnerability and adaptation in a dryland community of the Elqui Valley, Chile   总被引：1，自引：0，他引：1  

Gwendolynne Young  Humberto Zavala  Johanna Wandel  Barry Smit  Sonia Salas  Elizabeth Jimenez  Melitta Fiebig  Roxana Espinoza  Harry Diaz  Jorge Cepeda 《Climatic change》2010,98(1-2):245-276

Livelihoods in drylands are already challenged by the demands of climate variability, and climate change is expected to have further implications for water resource availability in these regions. This paper characterizes the vulnerability of an irrigation-dependent agricultural community located in the Elqui River Basin of Northern Chile to water and climate-related conditions in light of climate change. The paper documents the exposures and sensitivities faced by the community in light of current water shortages, and identifies their ability to manage these exposures under a changing climate. The IPCC identifies potentially increased aridity in this region with climate change; furthermore, the Elqui River is fed by snowmelt and glaciers, and its flows will be affected by a warming climate. Community vulnerability occurs within a broader physical, economic, political and social context, and vulnerability in the community varies amongst occupations, resource uses and accessibility to water resources, making some more susceptible to changing conditions in the future. This case study highlights the need for adaptation to current land and water management practices to maintain livelihoods in the face of changes many people are not expecting.  相似文献   

Microdeformation of lacustrine laminite sequences from Late Miocene formations of SE Spain: an interpretation of loop bedding   总被引：2，自引：0，他引：2  

Jose P. Calvo  Miguel Rodriguez-Pascua  Silvia Martin-Velazquez  Sergio Jimenez  & Gerardo De Vicente 《Sedimentology》1998,45(2):279-292

Lacustrine laminated sediments (laminites) present in Late Miocene formations of the Híjar Basin, SE Spain, display well developed loop bedding, a structure consisting of bundles of laminae that are sharply constricted at intervals, giving a morphology of loops or links of a chain. The laminite sequences, which are interbedded with turbidite marlstones, were accumulated on the bottom of a permanently stratified lake developed in a rapidly subsiding basin limited by 010° and 105° normal faults. As deduced from both macro- and microdeformational analyses, the basin evolved under an extensional stress field throughout the Late Miocene. Four main types of loops, simple and complex loops with subcategories, have been recognized within the laminite sequence. Simple loops of type 1 show the best definite pattern, quite similar to ' pinch and swell structures ', a type of boudinage typical of stretching of alternating beds where the competence contrast is not strongly marked. The remaining loop types display contortion and occasional breakage of laminae (microfaulted edges) indicative of microdeformation near the boundary between the ductile-brittle deformational fields. The distribution of the various loop types across the laminite sequence reflects an interplay between progressive lithification of the laminites as sedimentation progressed and tectonic stresses which affected the sediment sequence. Accordingly, a mechanism of deformation under an extensional stress field, ultimately related to the creep movement of the main basin faults which resulted in successive seismic shocks of low magnitude, is proposed to explain the formation of loop bedding in the laminites.  相似文献   

Detection of Cyclic Patterns Using Wavelets: An Example Study in the Ormskirk Sandstone, Irish Sea     

Nestor A. Rivera  S. Ray  Jerry L. Jensen  Andrew K. Chan  Walter B. Ayers 《Mathematical Geology》2004,36(5):529-543

This study shows how wavelet analysis can be used on well log and drill core data to identify cyclicity in sedimentary sequences. Three possible methods for determining wavelength were investigated: the Morlet wavelet, the Fourier transform, and the semivariogram. When applied to several hypothetical signals similar to those observed in petrophysical measurements in hydrocarbon reservoirs, all three methods could identify the presence of cyclicity. Only the wavelet scalogram, however, gave a clear indication of when the cyclic element was present and where frequency changes occurred in the signal. To illustrate the wavelet analysis, we processed well log and core data from a well in the Ormskirk Sandstone and determined the wavelet coefficients for each zone and the wavelengths of the strongest cyclicities. The cyclicities observed corresponded well with sedimentary features of the formation (e.g., channels and channel sets). Also, ratios of the cyclicity wavelengths corresponded with ratios of the Milankovitch precession, obliquity, and eccentricity periods. This result is in agreement with other investigators, who have proposed that Milankovitch-driven climate changes exercised an important control on Ormskirk Sandstone deposition.  相似文献   

Asymptotic Dykstra�CParsons Distribution, Estimates and Confidence Intervals     

Salvador Pintos  Claritza Bohorquez  Nestor V. Queipo 《Mathematical Geosciences》2011,43(3):329-343

The sample Dykstra?CParsons (DP) coefficient, the most popular heterogeneity static measure among petroleum engineers, may exhibit significant sampling errors. Moreover, approximations of its probability distributions (uncertainty estimates) are only available for specific families of permeability models (e.g., log-normal). The cited probability distributions allow for the specification of confidence intervals and other inferences for the theoretical DP, which will be useful for reservoir screening purposes, or to establish if a more detailed study is justified. This paper presents the development of an asymptotic approximation of the distribution of the sample Dykstra?CParsons coefficient, which is independent of the permeability probability distribution. The effectiveness (bias and confidence intervals) of the proposed approach is demonstrated using analytical and field case studies and by comparing the results gleaned with those obtained using a well-known parametric approximation, under different scenarios of reservoir maturity levels (i.e., number of wells) and different degrees of deviation from the log-normal probability density function assumption. The results show that, in the vast majority of the case studies, the proposed approach outperformed the parametric approximation; in particular, our approach resulted in a significant reduction of the bias and the confidence intervals always including the theoretical DP coefficient. In addition, an excellent agreement was observed between the asymptotic cumulative distribution of the DP coefficient and the corresponding empirical distribution for sample sizes as small as one hundred, which suggests that high success rates can be obtained when reservoirs are classified according to the asymptotic DP coefficient.  相似文献   

Fast identification of transits from light-curves     

Pavlos Protopapas  Raul Jimenez  Charles Alcock 《Monthly notices of the Royal Astronomical Society》2005,362(2):460-468

We present an algorithm that allows fast and efficient detection of transits, including planetary transits, from light-curves. The method is based on building an ensemble of fiducial models and compressing the data using the moped compression algorithm. We describe the method and demonstrate its efficiency by finding planet-like transits in simulated Panoramic Survey Telescope & Rapid Response System (Pan-STARRS) light-curves. We show that our method is independent of the size of the search space of transit parameters. In large sets of light-curves, we achieve speed-up factors of the order of 10³ times over an optimized adaptive search in the χ² space. We discuss how the algorithm can be used in forthcoming large surveys like Pan-STARRS and the Large Synoptic Survey Telescope (LSST), and how it may be optimized for future space missions like Kepler and COROT where most of the processing must be done on board.  相似文献   

The ages of quasar host galaxies     

L. A. Nolan  J. S. Dunlop  M. J. Kukula  D. H. Hughes  T. Boroson  R. Jimenez † 《Monthly notices of the Royal Astronomical Society》2001,323(2):308-330

We present the results of fitting deep off-nuclear optical spectra of radio-quiet quasars, radio-loud quasars and radio galaxies at z ≃0.2 with evolutionary synthesis models of galaxy evolution. Our aim was to determine the age of the dynamically dominant stellar populations in the host galaxies of these three classes of powerful active galactic nuclei (AGN). Some of our spectra display residual nuclear contamination at the shortest wavelengths, but the detailed quality of the fits longward of the 4000-Å break provides unequivocal proof, if further proof were needed, that quasars lie in massive galaxies with (at least at z ≃0.2) evolved stellar populations. By fitting a two-component model we have separated the very blue (starburst and/or AGN contamination) from the redder underlying spectral energy distribution, and find that the hosts of all three classes of AGN are dominated by old stars of age 8–14 Gyr. If the blue component is attributed to young stars, we find that, at most, 1 per cent of the visible baryonic mass of these galaxies is involved in star formation activity at the epoch of observation, at least over the region sampled by our spectroscopic observations. These results strongly support the conclusion reached by McLure et al. that the host galaxies of luminous quasars are massive ellipticals which have formed by the epoch of peak quasar activity at z ≃2.5.  相似文献   

Synthetic stellar populations: single stellar populations, stellar interior models and primordial protogalaxies     

Raul Jimenez  James MacDonald  James S. Dunlop  Paolo Padoan  John A. Peacock 《Monthly notices of the Royal Astronomical Society》2004,349(1):240-254

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Old elliptical galaxies at  z ≃ 1.5  and the Kormendy relation     

I. Waddington  R. A. Windhorst  S. H. Cohen  J. S. Dunlop  J. A. Peacock  R. Jimenez  R. J. McLure  A. J. Bunker  H. Spinrad  A. Dey  D. Stern 《Monthly notices of the Royal Astronomical Society》2002,336(4):1342-1350

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Stages of development in the Polish Carpathian Foredeep basin     

Nestor Oszczypko  Marta Oszczypko-Clowes 《Central European Journal of Geosciences》2012,4(1):138-162

In southern Poland, Miocene deposits have been recognised both in the Outer Carpathians and the Carpathian Foredeep (PCF). In the Outer Carpathians, the Early Miocene deposits represent the youngest part of the flysch sequence, while in the Polish Carpathian Foredeep they are developed on the basement platform. The inner foredeep (beneath the Carpathians) is composed of Early to Middle Miocene deposits, while the outer foredeep is filled up with the Middle Miocene (Badenian and Sarmatian) strata, up to 3,000mthick. The Early Miocene strata are mainly terrestrial in origin, whereas the Badenian and Sarmatian strata are marine. The Carpathian Foredeep developed as a peripheral foreland basin related to the moving Carpathian front. The main episodes of intensive subsidence in the PCF correspond to the period of progressive emplacement of the Western Carpathians onto the foreland plate. The important driving force of tectonic subsidence was the emplacement of the nappe load related to subduction roll-back. During that time the loading effect of the thickening of the Carpathian accretionary wedge on the foreland plate increased and was followed by progressive acceleration of total subsidence. The mean rate of the Carpathian overthrusting, and north to north-east migration of the axes of depocentres reached 12 mm/yr at that time. During the Late Badenian-Sarmatian, the rate of advance of the Carpathian accretionary wedge was lower than that of pinch-out migration and, as a result, the basin widened. The Miocene convergence of the Carpathian wedge resulted in the migration of depocentres and onlap of successively younger deposits onto the foreland plate.  相似文献