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121.
We analyze a mathematical model of the epizootic of Hantavirus in mice populations, including the effect of species that compete with the host. We show that the existence of the second species has an important consequence for the prevalence of the infectious agent in the host. When the two mice species survive in the ecosystem, the competitive pressure of the second species may lead to reduction or complete elimination of the prevalence of infection. The transition between the disappearance of the infection and its presence occurs at a critical value of the competitor's population, resembling a second-order phase transition in a statistical system. The results provide a rigorous framework for the study of the impact of biodiversity in the propagation of infectious diseases, and further lends itself to future experimental verification. 相似文献
122.
This study analyzed the evolution of metal levels in surface sediments from the Guadalquivir estuary between 1997 and 2002 and assessed the impact of the April 1998 Aznalcollar tailings dam failure and subsequent cleanup on metal concentrations in surface sediments. We also analyzed metal distribution with time in five chemical fractions of the surface sediments: exchangable, carbonate, reducible, oxidizable, and residual. This work showed that the April 1998 Aznalcollar tailings dam failure caused a considerable increase in the concentrations of Cd, Zn, Cu, and Pb in the surface sediments of the Guadalquivir estuary. It was also found there was a change in the distribution of Cd, Zn, Cu, and Pb between the chemical fractions of the sediment after the failure of the dam. There were increases in the percentages of Cd in the carbonate fraction, of Zn and Pb in the reducible fraction, and of Cu in the oxidizable fraction, whereas the percentages of these elements associated with the residual fraction decreased. In 1999, there was a decrease in the metal concentrations in the surface sediments from the Guadalquivir estuary, and by 2000 the chemical distribution and metal levels had returned to levels similar those before the dam failure. 相似文献
123.
Population frequencies of alternative male phenotypes in tree lizards: geographic variation and common-garden rearing studies 总被引:2,自引:0,他引:2
Diana K. Hews Christopher W. Thompson Ignacio T. Moore Michael C. Moore 《Behavioral ecology and sociobiology》1997,41(6):371-380
Tree lizards (Urosaurus ornatus) vary in throat fan (dewlap) color. Earlier, we described five dewlap types (Orange, Orange-Blue, Yellow, Yellow-Blue, and
Blue), and reported that only males had blue in the dewlap and that presence or absence of a discrete blue patch was correlated
with male alternative reproductive phenotypes in a central Arizona population. Here, with a modified scheme characterizing
two dewlap elements, background color (orange, yellow, blue) and blue patch occurrence, we assessed: (1) sexual, annual, and
geographic variation in the frequencies of dewlap elements; (2) simple habitat correlates; and (3) the effects of laboratory
rearing regime on dewlap type. Within a population, frequencies of males and females expressing orange or yellow backgrounds
did not differ, suggesting that control of background is similar in the sexes. Within several populations, frequencies of
the dewlap elements did not differ across years (and probably generations), indicating that phenotype frequencies are relatively
stable. Among five populations frequencies of background colors varied, as did frequencies of male types (blue patch present
or absent). Dewlap frequencies did not correlate with habitat (boulders or mesquite trees), although few populations were
sampled. In male and female offspring reared from eggs to sexual maturity in a common-garden laboratory study, background
color frequencies in both sexes and blue patch frequencies in males differed among offspring from different populations. Offspring
frequencies matched respective parental population frequencies. Results suggest that among-population variation in frequencies
of the two dewlap elements are mediated by differences in genetics, in maternal effects, or both. Thus, differences in male
behavior functionally linked to the blue patch also may be controlled by genetic or maternal effects.
Received: 17 January 1997 / Accepted after revision: 30 August 1997 相似文献
124.
Enrique Morán-Tejeda Antonio Ceballos-Barbancho José Manuel Llorente-Pinto Juan Ignacio López-Moreno 《Regional Environmental Change》2012,12(1):17-33
Land-use and land-cover changes have attracted substantial scientific interest in recent years because of their marked influence
on hydrological cycles. In developed countries of the Mediterranean basin, the generalized revegetation and forest growth
in mountainous areas that occurred during the last five decades are negatively affecting the evolution of water resources
in headwaters. In this study, changes in land cover in the Duero River Basin (northern Spain) during the last 50 years were
analyzed and their role in hydrological evolution was estimated. For this purpose, step-wise linear regressions were developed
to estimate the evolution of runoff as a function of climate (precipitation and temperatures). The results show a significant
expansion of forest cover in the headwaters, although it has been more extensive in the mountains to the north of the basin
than to the south. River discharges in the headwaters underwent a generalized decline during the study period (1961–2006),
but precipitation over the same period did not show an appreciable trend. In the absence of noticeable trends in removal of
water for human consumption, our results indicate that revegetation is contributing to the observed hydrological decline.
Our hypothesis is confirmed because of the greater divergence in the evolution of precipitation and runoff in the northern
headwaters (more forest growth) than in the south headwaters (less forest growth). Results suggest that further increases
in forest area will enhance hydrological decline and highlight the importance of integrating land-cover information in water
availability assessments in a region where water is a strategic resource. 相似文献
125.
126.
This work, on the ashes from the wastewater treatment plant of Galindo (Vizcaya, Spain), has been outlined with the purpose of finding their physico-chemical properties and suggesting possible applications. Ashes contain important quantities of iron, calcium, silica, alumina and phosphates. X-Ray diffraction data make it possible to estimate the mineralogical compositions of the original ashes and also, after thermal treatment at 1200 and 1300 degrees C, the main reactions occurring in thermal treatment. Particle size analysis makes it possible to classify ashes as a very fine powdered material. The thermal treatment leads to a densification of the material and provokes losses of weight mainly due to the elimination of water, carbon dioxide and sulphur trioxide. Application tests show that ashes are not suitable for landfill and similar applications, because of their plastic properties. Testing for pozzolanic character, after the ashes had been heated at 1200 degrees C, did not lead to a strong material probably due to low contents in silica and alumina or to requiring a higher heating temperature. Thermal treatment leads to densification of the material with a considerable increase of compressive strength of the probes. The use of additives (clays and powdered glass) to improve ceramic properties of ashes will be the aim of a future work. 相似文献
127.
The Prestige oil spill in November 2002 is considered the biggest large-scale catastrophe of its type in Europe, thousands of seabirds dying in the subsequent months. Here, the total concentration of 16 polycyclic aromatic hydrocarbons (TPAH) was measured in the blood cell fraction of adult and chick yellow-legged gulls (Larus michahellis) from unoiled and oiled coastal areas in North Western Spain. In addition, hematocrit, plasma metabolites, electrolytes and enzymes, as well as body mass were determined in the same individuals. Our results strongly suggest the presence of health damages of sublethal nature in adult gulls breeding in oiled colonies 17 months after the Prestige oil spill. This is supported by the following evidences: (1) gulls sampled in unoiled and oiled colonies differed in blood TPAH levels, (2) gulls sampled in unoiled and oiled colonies differed in several blood parameters indicative of physiological disorders, and (3) TPAH in blood was significantly related to several of these parameters. Differences in the level of asparatate aminotransferase (AST), gamma-glutamyl transferase (GGT), total protein, glucose and inorganic phosphorus suggest damages on some vital organs (i.e. liver and kidney) in adult birds from oiled areas. Meanwhile, chicks presented weaker effects than adults, showing only between-area differences in hematocrit. Since TPAH levels in blood did not differ between both age-groups, the stronger effects on adults should be due to their longer exposure to these pollutants and/or to severe exposure in the months following the spill. The presence of PAHs in chicks indicates that these pollutants were incorporated into the food chain because nestlings would have been only exposed to contaminated organisms in the diet (e.g. fishes and crustaceans). Our findings support the view that PAHs may deeply alter the physiology of seabirds, and emphasize the necessity of quantifying the circulating levels of these compounds in order to evaluate the sublethal effects associated to large oil spills. 相似文献
128.
del Real Álvaro Expósito Andrea Ruiz-Azcona Laura Santibáñez Miguel Fernández-Olmo Ignacio 《Environmental science and pollution research international》2022,29(42):62973-62983
Environmental Science and Pollution Research - We aimed to determine the presence of SARS-CoV-2 RNA in indoor and outdoor size-segregated aerosol samples (PM10-2.5, PM2.5). Five outdoor daily... 相似文献
129.
Fernández-Macías Juan Carlos Ochoa-Martínez Angeles Catalina Pérez-López Anette Aylin Pérez-López Amairani Lizbeth Neri-Maldonado Ignacio Piña-López Iris Gabriela Pérez-Maldonado Iván Nelinho 《Environmental science and pollution research international》2022,29(32):48466-48476
Environmental Science and Pollution Research - Cardiovascular diseases (CVDs) are the leading cause of morbidity and mortality worldwide. Environmental and genetic factors are recognized as risk... 相似文献