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M. Aguilera C. Espinar J.P. Ferrio G. Prez J. Voltas 《Journal of Geochemical Exploration》2009,102(3):157
Carbon isotope composition (δ13C) in tree-rings has become routinely used in palaeoclimatic research for the assessment of changes in plant water availability in seasonally dry climates. However, the distribution of long tree-ring records around the world is very limited. Alternatively, the original climate signal of wood δ13C is well preserved in fossil charcoal and, accordingly, charcoal δ13C can be used to quantify past changes in water availability (e.g. precipitation). We report a case study on spatial palaeoclimate reconstruction which aims to characterize the transition between Bronze and Iron Ages, the so-called Iron Age Cold Epoch (ca. 900–300 BCE), using charcoals of Quercus ilex/coccifera from a set of 11 contemporary archaeological sites of eastern Spain. Climatic inferences were obtained after calibrating a linear model predicting seasonal precipitation from δ13C of Q. ilex wood samples obtained across a rainfall gradient. The best regression model corresponded to September–December (autumn) precipitation (Paut), in agreement with the fact that Q. ilex is able to exploit previous-year water reserves thanks to very effective water uptake. Subsequently, we estimated Paut from the δ13C of fossil charcoal to infer spatial patterns in water availability. Overall, estimated past Paut was about 19% higher (296 mm) than present-time values averaged across archaeological sites (249 mm). However, a clear geographic pattern of differences in precipitation could be observed in which the inner continental regions of eastern Spain were characterized by more humid conditions in the past, whereas the coastal strip of the Mediterranean Sea barely differed in past and present Paut values. The quite uniform distribution of archaeological sites over eastern Spain allowed development of contour maps of absolute and relative (to present) past Paut using gridded interpolation methods implemented in a GIS, highlighting the potential of this approach for reconstructing high-resolution spatial patterns of past climate. 相似文献
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D. N. Aguilera 《Astrophysics and Space Science》2007,308(1-4):443-450
We present results of a microscopic calculation using NJL-type model of possible spin-one pairings in two flavor quark matter
for applications in compact star phenomenology. We focus on the color-spin locking phase (CSL) in which all quarks pair in
a symmetric way, in which color and spin rotations are locked. The CSL condensate is particularly interesting for compact
star applications since it is flavor symmetric and could easily satisfy charge neutrality. Moreover, the fact that in this
phase all quarks are gapped might help to suppress the direct Urca process, consistent with cooling models. The order of magnitude
of these small gaps (≃1 MeV) will not influence the EoS, but their also small critical temperatures (T
c
≃800 keV) could be relevant in the late stages neutron star evolution, when the temperature falls below this value and a CSL
quark core could form.
D.N.A. work and attendance to the meeting was supported by VESF-Fellowships EGO-DIR-112/2005. 相似文献
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A novel modeling method is presented for indexing and normalizing natural gas endowments of petroleum provinces. The approach
is demonstrated with data from Canada, the Unites States, and Latin American and Caribbean (LAC) countries. A variable shape
distribution model (VSD) is used to fit the conventional natural gas endowment published by the United States Geological Survey
(USGS) for 29 provinces in LAC countries and 85 provinces in Canada and the United States. These data are indexed and normalized
to generate curves showing number of provinces versus normalized endowments. Results are compared with normalized endowments
from provinces in other regions around the world, including Europe, Asia Pacific, the Middle East, North Africa, and the former
Soviet Union (FSU). The comparison gives the method predictive power for estimating the natural gas endowment, particularly
in LAC provinces that at present have little exploration activity. Of particular importance is the fact that all the curves
of the various regions display a generally concave pattern throughout. The exception is the LAC curve, which displays the
shape of an inverted S and has a distinct convex pattern at the largest gas endowment volumes. This comparison suggests there
is potentially a large volume of natural gas in the region that has not been considered in previous studies. 相似文献
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Spain, which has always been a land of emigrants, is currently a centre of attraction for immigrants, as are other countries in Mediterranean Europe. The proportion is not as high as in other countries with a longer tradition of immigration. In this survey we selected the six nationalities which provide the highest numbers of immigrants from the developing world, and which have the greatest racial or cultural contrast to the native population. We analyse their structural features, whether or not immigrants from the same country are collect in the Madrid Metropolitan Area, the recent mobility of the immigrant population, and the evolution of immigration since the Administration carried out a regularization process, as well as Spaniards' opinion of foreign immigrants. 相似文献
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Adaptive variability to low‐pH river discharges in Acartia tonsa and stress responses to high PCO2 conditions 
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下载免费PDF全文 Victor M. Aguilera Cristian A. Vargas Marco A. Lardies María J. Poupin 《Marine Ecology》2016,37(1):215-226
Environmental transitions leading to spatial physical–chemical gradients are of ecological and evolutionary interest because they are able to induce variations in phenotypic plasticity. Thus, the adaptive variability to low‐pH river discharges may drive divergent stress responses [ingestion rates (IR) and expression of stress‐related genes such as Heat shock protein 70 (Hsp70) and Ferritin] in the neritic copepod Acartia tonsa facing changes in the marine chemistry associated to ocean acidification (OA). These responses were tested in copepod populations inhabiting two environments with contrasting carbonate system parameters (an estuarine versus coastal area) in the Southern Pacific Ocean, and assessing an in situ and 96‐h experimental incubation under conditions of high pressure of CO2 (PCO2 1200 ppm). Adaptive variability was a determining factor in driving variability of copepods' responses. Thus, the food‐rich but colder and corrosive estuary induced a traits trade‐off expressed as depressed IR under in situ conditions. However, this experience allowed these copepods to tolerate further exposure to high PCO2 levels better, as their IRs were on average 43% higher than those of the coastal individuals. Indeed, expression of both the Hsp70 and Ferritin genes in coastal copepods was significantly higher after acclimation to high PCO2 conditions. Along with other recent evidence, our findings confirm that adaptation to local fluctuations in seawater pH seems to play a significant role in the response of planktonic populations to OA‐associated conditions. Facing the environmental threat represented by the inter‐play between multiple drivers of climate change, this biological feature should be examined in detail as a potential tool for risk mitigation policies in coastal management arrangements. 相似文献
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A. D. Maldonado P. A. Aguilera A. Salmerón 《Stochastic Environmental Research and Risk Assessment (SERRA)》2016,30(5):1441-1455
Bayesian networks (BNs) are being increasingly applied to environmental research. Nonetheless, most of the literature related to environmental sciences use discrete or discretized data, which entails a loss of information. We propose a novel methodology based on continuous BNs to predict the probability that surface waters do not meet the standards, in relation to nitrate concentration, established by the European Water Framework Directive. In order to achieve our purpose, a Tree Augmented Naive Bayes (TAN), was developed and applied to estimate and map the risk of failing to meet the European standards established. The TAN models were tested by means of the k-fold cross validation method. The results revealed that the TAN model performed proper risk maps and suggested that poor water quality is highly probable in watersheds dominated by irrigated herbaceous crops. On the contrary, “good surface water status” is more likely to occur in areas where forest is notably present. 相似文献
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Barriers to dispersal are recognized to play an important role in the differentiation of populations and ultimately in speciation. In the southeast Pacific, on the northern coast of Peru, a transition zone between the Peruvian and Panamic marine biogeographic provinces exists. Here, the convergence between two contrasting surface currents could generate a barrier effect for the larval dispersal of meroplanktonic invertebrates, which could in turn generate differentiated populations or genetic lineages on both sides of the transition zone. To address this, we studied to Echinolittorina paytensis, an abundant rocky intertidal periwinkle that spans both biogeographic provinces. A total of 95 individuals from Ecuador (2°19′S) to central Peru (7°31′S), covering the Panamic Province, the Peruvian Province, and the transition zone between, were collected. The mitochondrial markers cytochrome c oxidase I and 16SrRNA were sequenced in order to investigate phylogeography and genetic structuring. In general, no genetic structuring was found across the transition zone, suggesting this biogeographic boundary would not be acting as a barrier in this species. Factors such as a high larval dispersal capability and the occurrence of El Niño–Southern Oscillation events such as El Niño are discussed. 相似文献
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