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排序方式: 共有193条查询结果,搜索用时 328 毫秒
91.
James C. Matthews Jonathan P. Ward Paul A. Keitch Denis L. Henshaw 《Atmospheric environment (Oxford, England : 1994)》2010,44(39):5093-5100
High voltage power lines are known to produce corona ions that can be carried from the line by the wind, progressively attaching to ambient aerosol particles and causing fluctuations in the Earth’s atmospheric potential gradient. A fixed site monitoring station was installed near two power lines, which recorded the potential gradient at 1 s intervals and the ambient weather conditions every 10 min. The station ran continuously from January 2007 to December 2008, accumulating long-term data. Results from 2008 show an increase in potential gradient variability when a wind is blowing across the power lines towards the station, indicating that corona ions may be present in this environment. 相似文献
92.
Haemoglobinopathies including α- and β-thalassaemia are the world's most common class of single gene disorder. Prenatal diagnosis (PND) for β-thalassaemia has been proven to be an effective strategy for controlling the incidence of new cases and is widely used in several countries where the disease is common. Successful preimplantation genetic diagnosis (PGD) protocols for β-thalassaemia have been introduced using restriction fragment length polymorphism (RFLP), single-stranded conformation polymorphism (SSCP) and denaturing gradient gel electrophoresis (DGGE). However, contamination and allele dropout (ADO) remain an important concern for all of these strategies. In the present study two PGD protocols for detecting β-thalassaemia mutations (codon 41-42 and IVSI-110) and one for α-thalassaemia (SEA mutation) have been designed and tested. These methods contain failsafe mechanisms to reduce the risk of misdiagnosis due to ADO or contamination and utilise multiplex fluorescent PCR (F-PCR). Interestingly, amplification efficiency and ADO were significantly affected by the choice of DNA polymerase and the freshness of the single cells used. The close similarity between the DNA sequences of β-globin and δ-globin was also found to be an important issue that necessitated careful design of primers for the β-globin gene. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
93.
Jenny Farmer Robin Matthews Pete Smith Jo U. Smith 《Mitigation and Adaptation Strategies for Global Change》2014,19(6):863-885
Land use change on Indonesian peatlands contributes to global anthropogenic greenhouse gas (GHG) emissions. Accessible predictive tools are required to estimate likely soil carbon (C) losses and carbon dioxide (CO2) emissions from peat soils under this land use change. Research and modelling efforts in tropical peatlands are limited, restricting the availability of data for complex soil model parameterisation and evaluation. The Tropical Peatland Plantation-Carbon Assessment Tool (TROPP-CAT) was developed to provide a user friendly tool to evaluate and predict soil C losses and CO2 emissions from tropical peat soils. The tool requires simple input values to determine the rate of subsidence, of which the oxidising proportion results in CO2 emissions. This paper describes the model structure and equations, and presents a number of evaluation and application runs. TROPP-CAT has been applied for both site specific and national level simulations, on existing oil palm and Acacia plantations, as well as on peat swamp forest sites to predict likely emissions from future land use change. Through an uncertainty and sensitivity analysis, literature reviews and comparison with other methods of estimating soil C losses, the paper identifies opportunities for future model development, bridging between different approaches to predicting CO2 emissions from tropical peatlands under land use change. TROPP-CAT can be accessed online from www.redd-alert.eu in both English and Bahasa Indonesia. 相似文献
94.
Stephen Tong Tu'uhevaha Joy Kaitu'u-Lino Susan Philippa Walker Teresa Mary MacDonald 《黑龙江环境通报》2019,39(11):947-957
Fetal growth restriction (FGR) is associated with threefold to fourfold increased risk of stillbirth. Identifying FGR, through its commonly used surrogate—the small-for-gestational-age (SGA, estimated fetal weight and/or abdominal circumference <10th centile) fetus—and instituting fetal surveillance and timely delivery decrease stillbirth risk. Methods available to clinicians for antenatal identification of SGA fetuses have surprisingly poor sensitivity. About 80% of cases remain undetected. Measuring the symphysis-fundal height detects only 20% of SGA fetuses, and even universal third trimester ultrasound detects, at best, 57% of those born SGA. There is an urgent need to find better ways to identify this at-risk cohort. This review summarises efforts to identify molecular biomarkers (proteins, metabolites, or ribonucleic acids) that could be used to better predict FGR. Most studies examining potential biomarkers to date have utilised case-control study designs without proceeding to validation in independent cohorts. To develop a robust test for FGR, large prospective studies are required with a priori validation plans and cohorts. Given that current clinical care detects 20% of SGA fetuses, even a screening test with ≥60% sensitivity at 90% specificity could be clinically useful, if developed. This may be an achievable aspiration. If discovered, such a test may decrease stillbirth. 相似文献
95.
Natural fallout 210Pb may be extracted from soils with hot, dilute nitric acid without extracting significant quantities of 210Pb produced by decay of radon in the soil. This method was used to determine the distribution of fallout 210Pb in the profiles of nine New Zealand soils. The measured levels were similar to equilibrium cumulative depositions calculated from deposition records. The results indicate that these soils have quantitatively retained fallout 210Pb, with 75–100% of it being concentrated in the top 10 cm of soil. This permanent retention of fallout lead by soils suggests that accumulation of lead in the upper soil layer is likely in areas of aerosol lead pollution. 相似文献
96.
Bias in protected‐area location and its effects on long‐term aspirations of biodiversity conventions
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Oscar Venter Ainhoa Magrach Nick Outram Carissa Joy Klein Hugh P. Possingham Moreno Di Marco James E.M. Watson 《Conservation biology》2018,32(1):127-134
To contribute to the aspirations of recent international biodiversity conventions, protected areas (PAs) must be strategically located and not simply established on economically marginal lands as they have in the past. With refined international commitments under the Convention on Biological Diversity to target protected areas in places of “importance to biodiversity,” perhaps they may now be. We analyzed location biases in PAs globally over historic (pre‐2004) and recent periods. Specifically, we examined whether the location of protected areas are more closely associated with high concentrations of threatened vertebrate species or with areas of low agricultural opportunity costs. We found that both old and new protected areas did not target places with high concentrations of threatened vertebrate species. Instead, they appeared to be established in locations that minimize conflict with agriculturally suitable lands. This entrenchment of past trends has substantial implications for the contributions these protected areas are making to international commitments to conserve biodiversity. If protected‐area growth from 2004 to 2014 had strategically targeted unrepresented threatened vertebrates, >30 times more species (3086 or 2553 potential vs. 85 actual new species represented) would have been protected for the same area or the same cost as the actual expansion. With the land available for conservation declining, nations must urgently focus new protection on places that provide for the conservation outcomes outlined in international treaties. 相似文献
97.
Metachromatic polyelectrolyte titration was investigated as a means of analyzing polymeric quaternary ammonium salts (polyquaterniums) of relatively low charge density used as ingredients in cosmetics. They are of possible toxicological concern, but little is known of their environmental fate and behavior. With o-toluidine blue as the indicator, determination of the concentration of a range of polyquaterniums of commercial importance and cosmetic origin was possible. Using a visual endpoint, normalities as low as 3 × 10?5 N could be determined, while with a spectrophotometric endpoint, the technique was effective to approximately 3 × 10?6 N. The concentrations (g L?1) to which these normalities correspond depend on the charge density of the polymer. Polyquaterniums are frequently used in association with anionic surfactants in cosmetic formulations and the presence of an anionic surfactant even in excess did not affect results although the color change was less stable. Titration in the presence of prepared humic acid was also possible. 相似文献
98.
Hobbs WO Hobbs JM LaFran?ois T Zimmer KD Theissen KM Edlund MB Michelutti N Butler MG Hanson MA Carlson TJ 《Ecological applications》2012,22(5):1483-1496
Multiple stressors to a shallow lake ecosystem have the ability to control the relative stability of alternative states (clear, macrophyte-dominated or turbid, algal-dominated). As a consequence, the use of remedial biomanipulations to induce trophic cascades and shift a turbid lake to a clear state is often only a temporary solution. Here we show the instability of short-term manipulations in the shallow Lake Christina (Minnesota, USA) is governed by the long-term state following a regime shift in the lake. During the modern, managed period of the lake, three top-down manipulations (fish kills) were undertaken inducing temporary (5-10 years) unstable clear-water states. Paleoecological remains of diatoms, along with proxies of primary production (total chlorophyll a and total organic carbon accumulation rate) and trophic state (total P) from sediment records clearly show a single regime shift in the lake during the early 1950s; following this shift, the functioning of the lake ecosystem is dominated by a persistent turbid state. We find that multiple stressors contributed to the regime shift. First, the lake began to eutrophy (from agricultural land use and/or increased waterfowl populations), leading to a dramatic increase in primary production. Soon after, the construction of a dam in 1936 effectively doubled the depth of the lake, compounded by increases in regional humidity; this resulted in an increase in planktivorous and benthivorous fish reducing phytoplankton grazers. These factors further conspired to increase the stability of a turbid regime during the modern managed period, such that switches to a clear-water state were inherently unstable and the lake consistently returned to a turbid state. We conclude that while top-down manipulations have had measurable impacts on the lake state, they have not been effective in providing a return to an ecosystem similar to the stable historical period. Our work offers an example of a well-studied ecosystem forced by multiple stressors into a new long-term managed period, where manipulated clear-water states are temporary, managed features. 相似文献
99.
100.
The objective of this present study is to examine the effect of nanobubbles on the physical properties improvement in the chosen water sample. So far, the research outcomes stated that the physical properties could be enhanced by addition of nanoparticles, but very few studies were performed with nanobubbles. The unique properties of nanobubbles (70–120 nanometers) explain their use in a wide range of engineering fields. Simple method for producing nanobubbles in a variety of aqueous solutions along with examples of their use is outlined in this work. Global environmental issues, including the deterioration and depletion of water supply are driving today's need for water treatment technology. As a solution, the use of micro- and nano-bubble (MNB) technologies in wastewater treatment has evolved. This page discuss the fundamentals of water treatment research, including their stability of bubbles, manufacturing processes, and chemical and physical features. 相似文献