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排序方式: 共有756条查询结果,搜索用时 15 毫秒
491.
Rogelio Cruz-Martínez Adolfo Etchegaray Saulo Molina-Giraldo Belen Nieto-Castro Enrique Gil Guevara Joaquin Bustillos Miguel Martínez-Rodríguez Alma Gámez-Varela Daniel Saldivar-Rodríguez Erendira Chávez-González Rodolfo Keller Ricardo Russo Eduardo Yepez-García Fausto Coronel-Cruz Johnatan Torres-Torres Alejandro Rojas-Macedo Daniel Ibarra-Ríos Ricardo Ordorica-Flores Jaime Nieto-Zermeño Manuel Alcocer-Alcocer 《黑龙江环境通报》2019,39(7):519-526
492.
493.
Manuel Alejandro Salaices Avila Roman Breiter 《Environmental Modeling and Assessment》2009,14(5):615-629
A general mathematical model to solve the advection–dispersion transport equation for multiple solutes was developed, where
the dual porosity mobile–immobile mass transfer, the two-site non-equilibrium model and first-order transformation reactions
were included. The two-site model was expressed with an equilibrium sorption term and a kinetic term. One of three kinetic
models could be used: the non-linear, the bilinear and the pore diffusion model. The traditional Freundlich or Langmuir isotherms
were employed to simulate no-interaction between the solutes, but with the extended Freundlich or extended Langmuir isotherms,
a competitive sorption could be simulated. The transport equation was solved with the Moving Concentration Slope method. The
mathematical model was tested and further simplified by using real data from soil column experiments, with 1,2-cis-dichloroethene and trichloroethene as model contaminants and silica gel and real soil samples as porous medium. 相似文献
494.
Luis F. de Diego Margarita de las Obras-Loscertales Francisco García-Labiano Aránzazu Rufas Alberto Abad Pilar Gayán Juan Adánez 《International Journal of Greenhouse Gas Control》2011,5(5):1190-1198
CO2 and SO2 are some of the main polluting gases emitted into atmosphere in combustion processes using fossil fuel for energy production. The former is one of the major contributors to build-up the greenhouse effect implicated in global climate change and the latter produces acid rain. Oxy-fuel combustion is a technology, which consists in burning the fuel with a mix of pure O2 and recirculated CO2. With this technology the CO2 concentration in the flue gas may be enriched up to 95%, becoming possible an easy CO2 recovery. In addition, oxy-fuel combustion in fluidized beds allows in situ desulfurization of combustion gases by supplying calcium based sorbent.In this work, the effect of the principal operation variables affecting the sulfation reaction rate in fluidized bed reactors (temperature, CO2 partial pressure, SO2 concentration and particle size) under typical oxy-fuel combustion conditions have been analyzed in a batch fluidized bed reactor using a limestone as sorbent. It has been observed that sulfur retention can be carried out by direct sulfation of the CaCO3 or by sulfation of the CaO (indirect sulfation) formed by CaCO3 calcination. Direct sulfation and indirect sulfation operating conditions depended on the temperature and CO2 partial pressure. The rate of direct sulfation rose with temperature and the rate of indirect sulfation for long reaction times decreased with temperature. An increase in the CO2 partial pressure had a negative influence on the sulfation conversion reached by the limestone due to a higher temperature was needed to work in conditions of indirect sulfation. Thus, it is expected that the optimum temperature for sulfur retention in oxy-fuel combustion in fluidized bed reactors be about 925–950 °C. Sulfation reaction rate rose with decreasing sorbent particle size and increasing SO2 concentration. 相似文献
495.
Paolo Cabras Alberto Angioni Vincenzo L. Garau Marinella Melis Filippo. M. Pirisi Franco Cabitza 《Journal of environmental science and health. Part. B》2013,48(6):1189-1199
Abstract Residues of three pesticides (dimethoate, parathion, and pyrazophos) in two artichoke cultivars, Masedu and Spinoso sardo, were investigated. The amount of pesticides in artichokes was greatly affected by the head shape. In the case of the calix‐shaped Masedu artichoke, the residues in whole heads at commercial ripening were on average about twice higher than those of the pagoda‐shaped Spinoso sardo artichoke. In the heart this ratio was 4 to 42 times greater. Residue decay rates were very fast, mainly owing to the dilution effect due to head growth. 相似文献
496.
Manuel Pompini Emily S. Clark Claus Wedekind 《Behavioral ecology and sociobiology》2013,67(4):649-656
Hatching is an important niche shift, and embryos in a wide range of taxa can either accelerate or delay this life-history switch in order to avoid stage-specific risks. Such behavior can occur in response to stress itself and to chemical cues that allow anticipation of stress. We studied the genetic organization of this phenotypic plasticity and tested whether there are differences among populations and across environments in order to learn more about the evolutionary potential of stress-induced hatching. As a study species, we chose the brown trout (Salmo trutta; Salmonidae). Gametes were collected from five natural populations (within one river network) and used for full-factorial in vitro fertilizations. The resulting embryos were either directly infected with Pseudomonas fluorescens or were exposed to waterborne cues from P. fluorescens-infected conspecifics. We found that direct inoculation with P. fluorescens increased embryonic mortality and induced hatching in all host populations. Exposure to waterborne cues revealed population-specific responses. We found significant additive genetic variation for hatching time, and genetic variation in trait plasticity. In conclusion, hatching is induced in response to infection and can be affected by waterborne cues of infection, but populations and families differ in their reaction to the latter. 相似文献
497.
This study describes the reproductive cycle of Petrosia ficiformis and documents for the first time embryogenesis in an oviparous haplosclerid demosponge. Gonochoric adults, occurring in 2:1
female/male ratios, spawned in late autumn, after a 7-month long oogenesis and a 2.5-week-long spermatogenesis. Following
a remarkable migration, the oocytes were released as 250 μm eggs bearing attached polar bodies and a thin mucous cover. Round-headed
spermatozoa with three large mitochondria, and many proacrosomal vesicles fertilized the eggs externally. A fertilization
membrane appeared around the zygotes. Nearly equal and total cleavage led to a stereoblastula that subsequently became an
entirely ciliated larva. The larva alternated spherical and multilobate body shape and consisted of undifferentiated cells.
It had poor abilities to swim and glide, probably experiencing passive dispersal and unselective attachment. Settlers developed
choanocyte chambers after 1.5 months. Symbiotic microbes were absent from gametes and larvae, being necessarily acquired from
the ambient at each sponge generation.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
498.
Ulises Diéguez-Aranda Fernando Castedo Dorado Juan Gabriel Álvarez González Alberto Rojo Alboreca 《Ecological modelling》2006
In this study we developed a dynamic growth model for Scots pine (Pinus sylvestris L.) plantations in Galicia (north-western Spain). The data used to develop the model were obtained from a network of permanent plots, of between 10 and 55-year-old, which the Unidade de Xestión Forestal Sostible (Sustainable Forest Management Unit) of the University of Santiago de Compostela has set up in pure plantations of this species of pine in its area of distribution in Galicia. In this model, the initial stand conditions at any point in time are defined by three state variables (number of trees per hectare, stand basal area and dominant height), and are used to estimate stand volume, classified by commercial classes, for a given projection age. The model uses three transition functions expressed as algebraic difference equations of the three corresponding state variables used to project the stand state at any point in time. In addition, the model incorporates a function for predicting initial stand basal area, which can be used to establish the starting point for the simulation. This alternative should only be used when the stand is not yet established or when no inventory data are available. Once the state variables are known for a specific moment, a distribution function is used to estimate the number of trees in each diameter class, by recovering the parameters of the Weibull function, using the moments of first and second order of the distribution (arithmetic mean diameter and variance, respectively). By using a generalized height–diameter function to estimate the height of the average tree in each diameter class, combined with a taper function that uses the above predicted diameter and height, it is then possible to estimate total or merchantable stand volume. 相似文献
499.
Maurizio Pettine Silvio Capri Maria Giuseppina Farrace Maura Manganelli Luisa Patrolecco Alberto Puddu Annamaria Zoppini 《Chemistry and Ecology》2002,18(1):13-25
The results obtained in the four seasonal cruises planned in the PRISMA II project are reported. These concern dissolved and colloidal organic carbon, free amino acids and total dissolved carbohydrates and heterotrophic activity. Main factors controlling organic matter degradation, resulting from laboratory tests not planned in the above project, are also discussed. Dissolved organic matter shows seasonal accumulation, which may be markedly different from year to year, and large contributions by colloidal and saccharide components. Heterotrophic activities play an important role in the carbon cycle, although laboratory runs highlight limitations caused by aging of organic matter and phosphorus deficiency. 相似文献
500.
Manuel Blouin Nicolas Sery Daniel Cluzeau Jean-Jacques Brun Alain Bédécarrats 《Environmental management》2013,52(2):309-320
Energy crisis, climate changes, and biodiversity losses have reinforced the drive for more ecologically-based approaches for environmental management. Such approaches are characterized by the use of organisms rather than energy-consuming technologies. Although earthworms are believed to be potentially useful organisms for managing ecosystem services, there is actually no quantification of such a trend in literature. This bibliometric analysis aimed to measure the evolution of the association of “earthworms” and other terms such as ecosystem services (primary production, nutrient cycling, carbon sequestration, soil structure, and pollution remediation), “ecological engineering” or “biodiversity,” to assess their convergence or divergence through time. In this aim, we calculated the similarity index, an indicator of the paradigmatic proximity defined in applied epistemology, for each year between 1900 and 2009. We documented the scientific fields and the geographical origins of the studies, as well as the land uses, and compare these characteristics with a 25 years old review on earthworm management. The association of earthworm related keywords with ecosystem services related keywords was increasing with time, reflecting the growing interest in earthworm use in biodiversity and ecosystem services management. Conversely, no significant increase in the association between earthworms and disciplines such as ecological engineering or restoration ecology was observed. This demonstrated that general ecologically-based approaches have yet to emerge and that there is little exchange of knowledge, methods or concepts among balkanized application realms. Nevertheless, there is a strong need for crossing the frontiers between fields of application and for developing an umbrella discipline to provide a framework for the use of organisms to manage ecosystem services. 相似文献