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111.
Yu Wu Jishan Liu Derek Elsworth Zhongwei Chen Luke Connell Zhejun Pan 《International Journal of Greenhouse Gas Control》2010,4(4):668-678
Although the influence of gas sorption-induced coal deformation on porosity and permeability has been widely recognized, prior studies are all under conditions of no change in overburden stress and effective stress-absent where effective stresses scale inversely with applied pore pressures. Here we extend formalism to couple the transport and sorption of a compressible fluid within a dual-porosity medium where the effects of deformation are rigorously accommodated. This relaxes the prior assumption that total stresses remain constant and allows exploration of the full range of mechanical boundary conditions from invariant stress to restrained displacement. Evolution laws for permeability and related porosity are defined at the micro-scale and applied to both matrix and an assumed orthogonal, regular and continuous fracture system. Permeability and porosity respond to changes in effective stress where sorption-induced strains may build total stresses and elevate effective stresses. Gas accumulation occurs in both free- and adsorbed-phases and due to effective grain and skeletal compressibilities. A finite element model is applied to quantify the net change in permeability, the gas flow, and the resultant deformation in a prototypical coal seam under in situ stresses. Results illustrate how the CO2 injectivity is controlled both by the competition between the effective stress and the gas transport induced volume change within the matrix system and by the dynamic interaction between the matrix system and the fracture system. For typical parameters, initial injection-related increases in permeability due to reduced effective stresses may endure for days to years but are ultimately countered by long-term reductions in permeability which may decline by an order of magnitude. Models suggest the crucial role of stresses and the dynamic interaction between matrix and fractures in correctly conditioning the observed response. 相似文献
112.
Oikwathaile Onosi Nicole S. Upfold Michael D. Jukes Garry A. Luke Caroline Knox 《Food and environmental virology》2020,12(1):84-88
Human bocavirus (HBoV) has a global distribution and is associated with respiratory and enteric infections, particularly in the paediatric population. In this study, raw sewage and mussel samples were analysed for the presence of HBoV using nested PCR with primers targeting the VP1/VP2 junction. Amplification and sequencing of the 382 bp region followed by phylogenetic analysis indicated the presence of HBoV 2 in mussel samples and HBoV 3 in sewage samples. This is the first report describing the presence of enteric-associated HBoV in environmental samples from South Africa and in mussel samples from the African continent. The results signify the need for further studies examining the potential risk of foodborne transmission of HBoV and highlight the importance of continued screening to determine the prevalence and epidemiology of HBoV in South Africa. 相似文献
113.
A nation-wide ecosystem science network for Canada was formed in 1994. At that time, mercury was a re-emerging issue in Canada and the Coordinating Office for the networksought collaboration to assess the issue. The key mechanismsby which the network has added value in addressing this issue are: 1) Information Dissemination, the network has organised, facilitated and co-hosted a number of regional,national and international mercury events (meetings, conferences and workshops) which have served to bring theexpertise together, the network also disseminates informationon it's web page, and the Coordinating Office hosts an annualNational Science Conference; 2) Collaborative Mercury Monitoring, network partners advocated the need for a singlehemispheric mercury network which resulted in the developmentof a compatible Canada–U.S. mercury deposition network, whichmay also be expanded into Mexico, and 3) Environmental Reporting, the network has collaborated with others to reporton current mercury findings through initiatives such as the 1998 Northeast States and Eastern Canadian Mercury Study, a 1999 Mercury Case Study and is presently a partner in the University of Quebec's proposal to form a Collaborative Mercury Ecosystem Research Network in Canada. 相似文献
114.
Marianne Marcoux Luke Rendell Hal Whitehead 《Behavioral ecology and sociobiology》2007,61(7):1093-1098
Cultural variation can affect the genetic evolution of a species if there are consistent cultural differences that contribute
to fitness variation between groups of individuals. In this study, measures of the reproductive success of groups of sperm
whales from different cultural clans are used as proxies for fitness. We measure reproductive success using population length
distributions from acoustic and photographic measurements and visual observations of the presence of calves. The results obtained
are generally consistent between methods; there are large and significant differences between the clans in the measures of
reproductive success. The results from this study strengthen the case for cultural hitchhiking in sperm whales by indicating
that differences in culture between clans correlate with differences in fitness. 相似文献
115.
Surface waves and roughness in self-aerated supercritical flow 总被引:1,自引:1,他引:1
In high-velocity open channel flows, free-surface aeration is commonly observed. The effects of surface waves on the air–water
flow properties are tested herein. The study simulates the air–water flow past a fixed-location phase-detection probe by introducing
random fluctuations of the flow depth. The present model yields results that are close to experimental observations in terms
of void fraction, bubble count rate and bubble/droplet chord size distributions. The results show that the surface waves have
relatively little impact on the void fraction profiles, but that the bubble count rate profiles and the distributions of bubble
and chord sizes are affected by the presence of surface waves. 相似文献
116.
Summary. Following herbivory, induced responses involving plant secondary metabolites have been reported in a number of tree species.
Although a wide range of plant secondary metabolites appear to operate as constitutive plant defences in trees belonging to
the Eucalyptus genus, no induced responses have as yet been reported following foliar-chewing insect damage. We empirically tested whether
branch defoliation (artificial and larval) of 2-year-old Eucalyptus globulus Labill. trees altered the abundance of specific plant secondary metabolites immediately (3 months after initial larval feeding)
and 8 months after the cessation of larval feeding. Metabolites assayed, included essential oils, polyphenolic groups and
foliar wax compounds and in all cases their abundance was not significantly altered by defoliation. However, the level of
foliar tannins after 3 months of larval feeding did display a trend that suggested elevated levels as the result of defoliation,
though this trend was not evident 8 months later, indicating that, if real, the response was a rapid and not a delayed induced
response. The level of foliar tannins was also negatively correlated to both average larval survival and average percentage
branch defoliation, suggesting that foliar tannins may operate as toxins and/or anti-feedants to M. privata larval feeding. 相似文献
117.
Modeling of adsorption isotherms and kinetics of uranium sorption by magnetic ion imprinted polymers
Application of magnetic U(VI) ion imprinted polymers (IIPs) coated on magnetic nanoparticles was investigated for pre-concentration and determination of U(VI) ions in aqueous solutions. The scanning electron micrographs revealed the microporosity of the adsorbent. Uranium leaching was successful as the energy-dispersive X-ray spectra showed. The Brunauer–Emmett–Teller (BET) surface area improved by more than 13-fold (83.1 and 6.2 m2 g?1 for the leached and unleached magnetic IIP, respectively). U(VI) uptake was optimized using batch experiments with parameters affecting the uptake performance, such as initial uranium concentration, pH, contact time, and adsorbent dose investigated. Pseudo-second-order kinetics and the Langmuir isotherm model best fitted the experimental data. The maximum adsorption capacity of uranium onto the activated magnetic IIP reached 5.4 mg g?1. The selectivity order was determined to be U(VI) > Ni(II) > Th(IV). 相似文献
118.
Selecting pseudo-absence data for presence-only distribution modeling: How far should you stray from what you know? 总被引:1,自引:0,他引:1
An important decision in presence-only species distribution modeling is how to select background (or pseudo-absence) localities for model parameterization. The selection of such localities may influence model parameterization and thus, can influence the appropriateness and accuracy of the model prediction when extrapolating the species distribution across time and space. We used 12 species from the Australian Wet Tropics (AWT) to evaluate the relationship between the geographic extent from which pseudo-absences are taken and model performance, and shape and importance of predictor variables using the MAXENT modeling method. Model performance is lower when pseudo-absence points are taken from either a restricted or broad region with respect to species occurrence data than from an intermediate region. Furthermore, variable importance (i.e., contribution to the model) changed such that, models became increasingly simplified, dominated by just two variables, as the area from which pseudo-absence points were drawn increased. Our results suggest that it is important to consider the spatial extent from which pseudo-absence data are taken. We suggest species distribution modeling exercises should begin with exploratory analyses evaluating what extent might provide both the most accurate results and biologically meaningful fit between species occurrence and predictor variables. This is especially important when modeling across space or time—a growing application for species distributional modeling. 相似文献
119.
A review of traffic-related air pollution exposure assessment studies in the developing world 总被引:9,自引:0,他引:9
Exposure assessment studies in the developing world are important. Although recent years have seen an increasing number of traffic-related pollution exposure studies, exposure assessment data on this topic are still limited. Differences among measuring methods and a lack of strict quality control in carrying out exposure assessment make it difficult to generalize and compare findings between studies. In this article, exposure assessment studies carried out in the developing world on several traffic-related air pollutants are reviewed. These pollutants include particulate matter (PM), carbon monoxide (CO), nitrogen dioxide (NO(2)), volatile organic compounds (VOCs), and polycyclic aromatic hydrocarbons (PAHs). In addition, it discusses advantages and disadvantages of various monitoring methods (ambient fixed-site monitoring, microenvironment monitoring, and personal exposure assessment using portable samplers) for these pollutants in exposure assessment studies. Also included in this paper is a brief introduction of standards for these pollutants in ambient air or in occupational settings established by the United States Environmental Protection Agency (USEPA), the United States Occupational Safety and Health Administration (OSHA) and the World Health Organization (WHO). The review ends with a summary of the limitations and gaps in recent studies and suggestions for future research in the developing world. 相似文献
120.
Luke P. Miller 《Marine Biology》2013,160(6):1489-1496
In highly seasonal intertidal habitats, changes in temperature through the year may drive substantial shifts in feeding and growth rates of organisms. For the dogwhelk Nucella lapillus, attacking and consuming Mytilus edulis mussels can take hours or days, depending on temperature. Handling time of dogwhelks feeding on mussels is therefore greatly affected by ocean temperature. I recorded attack time in the laboratory, partitioned into drilling and consumption time, for juvenile dogwhelks across a range of seawater temperatures representative of field seawater temperatures during the main growing seasons of summer and autumn. The combined length of a drilling attack and subsequent ingestion time tripled across the 10 °C decline in water temperatures from July through November, driven primarily by an increase in ingestion time. The observed reduction in handling time, coupled with projected sea surface warming in New England by the end of the twenty-first century, could extend the length of the growing season for Nucella and subsequently have cascading effects on the prey community. 相似文献