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951.
The extent to which genetic divergence can occur in the absence of physical barriers to gene flow is currently one of the
most controversial topics in evolutionary biology, with implications for our understanding of speciation, phenotypic plasticity
and adaptive potential. This is illustrated by a recent study reporting a surprising pattern of genetic differentiation between
intertidal and subtidal morphotypes of the broadcast-spawning Antarctic limpet Nacella concinna. To explore this further, we collected almost 400 Antarctic limpets from four depths (intertidal, 6, 15 and 25 m) at Adelaide
island, Antarctica, and conducted a combined morphometric and genetic analysis using 168 polymorphic amplified fragment length
polymorphism (AFLP) loci. Morphological analysis revealed not only pronounced differences between the two morphotypes, but
also a continuous cline in shell shape from the intertidal zone down to 25 m depth, suggesting that the distinction between
the morphotypes may be artificial. Moreover, genetic analysis using both F
st and a Bayesian analogue found no evidence for differentiation either between the two morphotypes or by depth, and a Bayesian
cluster analysis did not detect any cryptic genetic structure. Our findings lend support to the notion that limpets can be
phenotypically highly plastic, although further studies are required to determine unequivocally whether there is any genetic
basis to the observed variation in shell morphology. 相似文献
952.
Elaine S. Carvalho Rubén J. Sánchez Maria I. B. Tavares álano C. Lam?nica 《Journal of Polymers and the Environment》2010,18(4):661-667
The chemical modification of Acrylamidomethyl Cellulose Acetate Propionate (AMCAP) was carried out by radical addition of
acrylic acid. The structural modification was confirmed with the aid of FTIR, MS and NMR techniques. Thermal properties of
hydrophilic cellulose derivative (AMCAP–H2O2) such as glass transition (Tg 153 °C) and thermal stability (372.7 °C) were determined by DSC and TGA techniques, respectively. These thermal properties
confirmed the introduction of carboxylic groups into AMCAP structure, which causes an impact in their properties. The AMCAP–H2O2 shows minor contact angle compared to AMCAP, giving a more hydrophilic characteristic, due to acrylic acid addition into
the side chains of AMCAP polymer. 相似文献
953.
954.
Ricardo Ortiz Kenji Enya Kazuhiko Sekiguchi Kazuhiko Sakamoto 《Atmospheric environment (Oxford, England : 1994)》2009,43(2):382-388
An annular denuder and filter-pack system was tested in combination with the use of the in-tube and on-fiber O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine hydrochloride (PFBHA)-derivatization technique to simultaneously sample and measure gaseous and particulate concentrations of semivolatile bifunctional carbonyl compounds in the atmosphere. Ozone was denuded from the sampling air to avoid oxidation and PFBHA was used as the sorbent by coating the sampling denuders and impregnating the filters. The collection efficiency of the system was evaluated under different conditions in photochemical smog chamber experiments and in field samplings of urban and suburban atmospheres. The effects of concentration level, temperature, and humidity on the collection efficiency were assessed. The system showed average collection efficiencies in one denuder from 81% for pyruvic acid and 82% for glyoxylic acid to 87% for hydroxyacetone and dihydroxyacetone. The capacity of the filters to collect the gaseous fraction that cannot be collected in the denuders was also evaluated, and the system allows a correction for this artifact. The application of this method to chamber experiments and field samplings offers an easy-to-apply technique with good results that can be used to evaluate the partition mechanisms of these compounds in the atmosphere. 相似文献
955.
956.
957.
Direct nitrous oxide (N2O) emissions from fertilized soils are generally estimated using emission factors. However, the emission factors for N2O emission of applied slurry are not well quantified. The effect of slurry application technique on N2O emission was quantified in field experiments in the Netherlands in order to derive N2O emission factors for (shallow) injected and surface-applied cattle and pig slurries. Fluxes of N2O were measured using a closed flux chamber technique and a photo-acoustic infra-red gasmonitor. Fluxes of N2O were measured 64–83 times on grassland on sandy and clay soils and maize land on sandy soil, in the period 2007–2009. There were large differences in total N2O emission between the years, and differences between treatments were not consistent over the years and sites. The average emission factor of all treatments and years (n = 35) was 0.9% of the N applied, which is close to the default IPCC emission factor of 1%. However, the range in emission was large, i.e. from ?0.2% to 7.0%. The average emission factor for grassland was 1.7% of the N applied for calcium ammonium nitrate (CAN), 0.4% for shallow injected cattle slurry, and 0.1% for surface-applied cattle slurry. For maize land, the average emission factor for CAN was 0.1% of the N applied, for injected cattle slurry 0.9% and for surface-applied cattle slurry 0.4%. The emission factors for pig slurry applied to maize land were higher than for cattle slurry; 3.6% for injected pig slurry and 0.9% for surface-applied pig slurry. Increasing the N application rate on maize land resulted in higher emission factors for CAN, injected cattle slurry, and injected pig slurry. Concluding, on both grassland and maize land (shallow) injection of slurry increased the average emission factor of N2O in comparison to surface application. Differentiation of N2O emission factors which takes specific factors into account, such as N type and rate and application technique, can improve the quantification of N2O emission from agricultural soils and is needed to derive most efficient options for mitigation. 相似文献
958.
Shuokr Qarani Aziz Hamidi Abdul Aziz Mohd Suffian Yusoff Mohammed J.K. Bashir Muhammad Umar 《Journal of environmental management》2010,91(12):2608-2614
This study analyzes and compares the results of leachate composition at the semi-aerobic Pulau Burung Landfill Site (PBLS) (unaerated pond and intermittently aerated pond) and the anaerobic Kulim Sanitary Landfill in the northern region of Malaysia. The raw samples were collected and analyzed for twenty parameters. The average values of the parameters such as phenols (1.2, 6.7, and 2.6 mg/L), total nitrogen (448, 1200, and 300 mg/L N-TN), ammonia-N (542, 1568, and 538 mg/L NH3-N), nitrite (91, 49, and 52 mg/L NO2?-N), total phosphorus (21, 17, and 19 mg/L), BOD5 (83, 243, and 326 mg/L), COD (935, 2345, and 1892 mg/L), BOD5/COD (0.096,0.1124,0.205%), pH (8.20, 8.28, and 7.76), turbidity (1546, 180, and 1936 Formazin attenuation units (FAU)), and color (3334, 3347, and 4041 Pt Co) for leachate at the semi-aerobic PBLS (unaerated and intermittently aerated) and the anaerobic Kulim Sanitary Landfill were recorded, respectively. The obtained results were compared with previously published data and data from the Malaysia Environmental Quality Act 1974. The results indicated that Pulau Burung leachate was more stabilized compared with Kulim leachate. Furthermore, the aeration process in PBLS has a considerable effect on reducing the concentration of several pollutants. The studied leachate requires treatment to minimize the pollutants to an acceptable level prior to discharge into water courses. 相似文献
959.
Rehan Sadiq Sikandar A. Haji Geneviève Cool Manuel J. Rodriguez 《Journal of environmental management》2010,91(3):706-716
The purpose of indices is to summarize a large volume of information into a single number that is easy to understand and interpret. Environmental indices provide a composite picture of an environmental condition derived from a series of observed measurements and parameters. They are used as communication tools by regulatory agencies to characterize the state of a specific environmental system (air, water, and sediments) and to study the impact of regulatory policies on various environmental management practices. In the development of environmental indices, a few issues and problems have been encountered arising as a result of the abstraction of information and data. These problems are referred to as characteristic properties that include ambiguity, eclipsing, compensation and rigidity. These characteristic properties have long been identified and interpreted in Boolean (e.g., Yes/No) or qualitative (e.g., low, medium, high) terms. In this paper, we propose a new approach to describe the above stated characteristic properties on a continuous scale to evaluate and compare the behavior of various aggregation models. Our approach is based on developing penalty functions for each characteristic property. A water quality index example by Swamee and Tyagi (2000) is used to explain our approach. A detailed case study for a developing microbial risk index is also provided to show how the proposed approach can be extended to complex hierarchical systems. Results show that it is possible to improve aggregation models for index development. Future research directions to improve index development are also discussed. 相似文献
960.