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461.
The solubility data for a series of non‐hydrogen bonding, monosubstituted benzenes in binary mixtures of water and non‐hydrogen bonding cosolvents is presented. Good correlation between log solubility and fraction cosolvent is obtained, therefore the estimation of solubility in mixed solvents by a log‐linear relationship can be attained. Slight positive or negative deviations from predicted solubility values are seen at high volume fractions of cosolvents. These deviations are attributed to the cosolvent‐water interactions. 相似文献
462.
Bottom trawling is associated with reduced biomass and production in the marine benthic community. Abundance of hard-bodied
organisms such as bivalves, crustaceans and echinoderms typically declines in favour of soft-bodied opportunists such as polychaetes.
Trawling effects vary with habitat; impact and recovery time are typically greater for more complex substrates/communities
and those with lower rates of natural disturbance. Benthic organisms represent the prey base of a large component of the demersal
fish assemblage. Hence, trawling-induced change in benthic community structure and function may exert an indirect effect on
feeding success and growth of important commercially exploited fishes such as plaice Pleuronectes platessa. We present habitat-specific mixed effects models of plaice length as a function of age, bottom-trawling effort, population
density and near-bottom temperature, with sampling year and area, and fish sex incorporated as random effects. Across an observed
gradient of trawling effort in the Celtic Sea, plaice on gravel habitat showed significant declines in length at age while
plaice on sand habitat showed significant increases in length at age. Contrasting trawling effects likely reflect dietary
differences between habitats. Plaice on sand substrates are known to consume predominately polychaetes, which may proliferate
at moderate trawling intensity in this habitat. Conversely, plaice on gravel substrates are reported to consume more of the
fragile organisms such as echinoderms and bivalves that show marked declines with bottom trawling. An indirect effect of trawling
on prey availability and growth of demersal fish has substantial implications for fisheries sustainability via reduced ecosystem
carrying capacity and production of commercial fish. 相似文献
463.
Wilson Y. Fantong Hiroshi Satake Samuel N. Ayonghe Emmanuel C. Suh Segun M. A. Adelana Emilia Bi S. Fantong Hycinth S. Banseka Cletus D. Gwanfogbe Leonard N. Woincham Yoshitoshi Uehara Jing Zhang 《Environmental geochemistry and health》2010,32(2):147-163
The 500,000 inhabitants of Mayo Tsanaga River Basin are vulnerable to a “silent” fluorosis from groundwater consumption. For the first time, the groundwater is investigated for the purpose of identifying the provenance of fluoride and estimating an optimal dose of fluoride in the study area. Based on the fluoride content of groundwater, fluorine and major oxides abundances in rocks from the study area, mean annual atmospheric temperature, and on-site diagnosis of fluorosis in children, the following results and conclusions are obtained: Fluoride concentration in groundwater ranges from 0.19 to 15.2 mg/l. Samples with fluoride content of <1.5 mg/l show Ca–HCO3 signatures, while those with fluoride >1.5 mg/l show a tendency towards Na-HCO3 type. Fluor-apatite and micas in the granites were identified as the main provenance of fluoride in the groundwater through water-rock interactions in an alkaline medium. The optimal fluoride dose in drinking water of the study area should be 0.7 mg/l, and could be adjusted downward to a level of 0.6 mg/l due to the high consumption rate of groundwater, especially during drier periods. 相似文献
464.
OBJECTIVE: Assess currently available evidence regarding the ability of a motor vehicle collision (MVC) to trigger the development of fibromyalgia (FM). METHODS: Consensus standards developed by the American College of Rheumatology Environmental Disease Study Group were used to assess the ability of an MVC to trigger FM. RESULTS: Increasing evidence suggests that FM and related disorders are characterized by abnormalities in central nervous system function related to sensory processing, autonomic regulation, and neuroendocrine function. MVC trauma appears capable of triggering FM, but generally not through direct biomechanical injury. Instead, the evidence suggests that MVC trauma can act as a "stressor," which in concert with other factors, such as an individual's biologic vulnerability, psychosocial factors, cultural factors, and so on, may result in the development of chronic widespread pain and other somatic symptoms. MVC trauma is only one of many stressors which can trigger such disorders, and the environment within which the stressor is experienced (biological and psychosocial) may largely determine whether there is an adverse physiologic result or not. CONCLUSIONS: The evidence that MVC trauma may trigger FM meets established criteria for determining causality, and has a number of important implications, both for patient care, and for research into the pathophysiology and treatment of these disorders. 相似文献
465.
Samuel W. Karickhoff 《Chemosphere》1981,10(8):833-846
Methods were developed for estimating the equilibrium sorption behavior of hydrophobic pollutants. At low pollutant concentration (aqueous phase concentration less than half the solubility), sorption isotherms were linear, reversible, and characterized by a partition coefficient, Kp. Partition coefficients normalized to organic carbon, KOC ( organic carbon), were highly invariant over a set of sediments and soils collected from throughout the nation. Equations for estimating KOC from water solubility (including crystal energy) and octanol/water partition coefficients were developed. The predictive equations were tested on literature sorption data and found to estimate measured KOC's generally within a factor of two. 相似文献
466.
Allen S. Hope Donald E. Petzold Samuel N. Goward Robert M. Ragan 《Journal of the American Water Resources Association》1986,22(6):1011-1019
ABSTRACT: A canopy reflectance model is incorporated into a routine for simulating water and energy flows in the soil-plant-atmosphere system. The reflectance model is structured tocalculate canopy albedo throughout each simulation period and to determine spectral reflectances at a specified time during the day. Spectral vegetation indices are then calculated from the reflectances and related to the evapotranspiration and thermal response of the canopy. The canopy reflectance model is also used to establish the photo-sytheticaily active radiation load at various depths in the canopy. Stomatal resistances are calculated using these radiation values and integrated to give the minimum canopy resistance. Actual canopy resistance is obtained by adjusting minimum canopy resistance for environmental stresses such as leaf water potential and leaf temperature. Using data for a soybean canopy, canopy evapotranspiration and temperatures are simulated for a range of leaf area index values and compared with the corresponding spectral vegetation indices. The resuits indicate that the normalized difference spectral index has an inverse linear relationship with canopy temperature, concurring with results obtained from satellite observations. The possibility of using a spectral vegetation index and thermal observations together to parameterize surface moisture availability for evapotranspiration is considered. 相似文献
467.
Samuel A. Bamberg Herbert N. Friesen 《Journal of the American Water Resources Association》1972,8(6):1108-1119
A technique is presented for developing an isohyet map for the Hualapai Valley, a closed hydrologic basin of about 315 square miles in the northwestern Great Basin in Nevada. In this basin there is practically no climatic data, and in the northwest Great Basin there are too few stations for determination of rainfall on a detailed basis. Using a vegetational typing to represent a range in elevation and precipitation, an initial mean annual rainfall is determined for selected points on a grid pattern. This rainfall is then modified by using topographic parameters of slope, orientation, exposure, and rainfall shadow effect. The resulting point determinations of mean annual rainfall are then smoothed using a trend surface analysis, and an isohyetal map is drawn from the smoothed points. The technique provides an estimated accuracy of one inch of mean annual precipitation and one mile of resolution on isohyets. 相似文献
468.
Daniel Miller Runfola Samuel Ratick Julie Blue Elia Axinia Machado Nupur Hiremath Nick Giner Kathleen White Jeffrey Arnold 《Mitigation and Adaptation Strategies for Global Change》2017,22(3):349-368
A flexible procedure for the development of a multi-criteria composite index to measure relative vulnerability under future climate change scenarios is presented. The composite index is developed using the Weighted Ordered Weighted Average (WOWA) aggregation technique which enables the selection of different levels of trade-off, which controls the degree to which indicators are able to average out others. We explore this approach in an illustrative case study of the United States (US), using future projections of widely available indicators quantifying flood vulnerability under two scenarios of climate change. The results are mapped for two future time intervals for each climate scenario, highlighting areas that may exhibit higher future vulnerability to flooding events. Based on a Monte Carlo robustness analysis, we find that the WOWA aggregation technique can provide a more flexible and potentially robust option for the construction of vulnerability indices than traditionally used approaches such as Weighted Linear Combinations (WLC). This information was used to develop a proof-of-concept vulnerability assessment to climate change impacts for the US Army Corps of Engineers. Lessons learned in this study informed the climate change screening analysis currently under way. 相似文献
469.
Frederick A. Armah Justice O. Odoi Genesis T. Yengoh Samuel Obiri David O. Yawson Ernest K. A. Afrifa 《Mitigation and Adaptation Strategies for Global Change》2011,16(3):291-306
Desertification, climate variability and food security are closely linked through drought, land cover changes, and climate
and biological feedbacks. In Ghana, only few studies have documented these linkages. To establish this link the study provides
historical and predicted climatic changes for two drought sensitive agro-ecological zones in Ghana and further determines
how these changes have influenced crop production within the two zones. This objective was attained via Markov chain and Fuzzy
modelling. Results from the Markov chain model point to the fact that the Guinea savanna agro-ecological zone has experienced
delayed rains from 1960 to 2008 while the Sudan savanna agro-ecological zone had slightly earlier rains for the same period.
Results of Fuzzy Modelling indicate that very suitable and moderately suitable croplands for millet and sorghum production
are evenly distributed within the two agro-ecological zones. For Ghana to adapt to climate change and thereby achieve food
security, it is important to pursue strategies such as expansion of irrigated agricultural areas, improvement of crop water
productivity in rain-fed agriculture, crop improvement and specialisation, and improvement in indigenous technology. It is
also important to encourage farmers in the Sudan and Guinea Savanna zones to focus on the production of cereals and legumes
(e.g. sorghum, millet and soybeans) as the edaphic and climatic factors favour these crops and will give the farmers a competitive
advantage. It may be necessary to consider the development of the study area as the main production and supply source of selected
cereals and legumes for the entire country in order to free lands in other regions for the production of crops highly suitable
for those regions on the basis of their edaphic and climatic conditions. 相似文献
470.
Combining material characterization with single and multi-oxyanion
adsorption for mechanistic study of chromate removal by cationic hydrogel 总被引:1,自引:1,他引:0
Cationic hydrogel with magnetic property was synthesized via radical polymerization and its removal capacity of chromate from
contaminated water was found to be 200 mg/g. Using Fourier transform infrared spectroscopy (FT-IR) study, the mechanism of
chromate removal by hydrogel was found to be non-specific adsorption, mainly due to ion exchange, as evidenced by the positively
charged functional group, trimethyl ammonium –N+(CH3)3; in the monomer. Verifications were accordingly determined by testing
different oxyanion adsorption onto the hydrogel. The results of the chromate adsorption experiments illustrated that the amount
of chromate adsorbed was nearly equal to that of the chloride released from the hydrogel, which is part of the evidence for ion
exchange. Single and multi-oxyanion adsorption experiments were also performed, and it was demonstrated that ion removal was
species independent, but charge dependent, another characteristic of the ion exchange process. It was found that the same Langmuir
model can be applied to best fit the findings of single and multi-oxyanion adsorption, which further indicates the mechanism of chromate
removal is attributed to ion exchange. In view of the above, the background anions compete for adsorption sites with chromate,
evidenced by inhibitive chromate removal in the presence of background electrolytes in the batch studies, further echoing the ion
exchange mechanism. 相似文献