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521.
John Prenter Robert W. Elwood W. Ian Montgomery 《Behavioral ecology and sociobiology》1994,35(1):39-43
Assessments and decision-making underlying the initiation of mate guarding in a common web-building spider, Metellina segmentata, are examined in a series of field and laboratory studies. Adult males do not build webs but wander in search of females and mating opportunities. Adult males then wait at the edge of the webs of females and guard them prior to courtship and mating. Guarded females were heavier, larger and carried more mature eggs than solitary females. An active process of information gathering is apparent from introductions of males to the webs of females. Males make accurate assessments about female quality, even in the absence of the resident female. Cues involving web architecture are not used. Males may assess pheromonal cues on the web of the female in deciding whether to guard or abandon a female. 相似文献
522.
We conducted kinetic and equilibrium sorption experiments on removal of Zn(II) from aqueous solutions by scoria (a vesicular pyroclastic rock with basaltic composition) from Jeju Island, Korea, in order to examine its potential use as an efficient sorbent. The batch-type kinetic sorption tests under variable conditions indicated that the percentage of Zn(II) removal by scoria increases with decreasing initial Zn(II) concentration, particle size, and sorbate/sorbent ratio. However, the sorption capacity decreases with the decrease of the initial Zn(II) concentration and sorbate/sorbent ratio. Equilibrium sorption tests show that Jeju scoria has a larger capacity and affinity for Zn(II) sorption than commercial powdered activated carbon (PAC); at initial Zn(II) concentrations of more than 10mM, the sorption capacity of Jeju scoria is about 1.5 times higher than that of PAC. The acquired sorption data are better fitted to the Langmuir isotherm than the Freundlich isotherm. Careful examination of ionic concentrations in sorption batches suggests that the sorption behavior is mainly controlled by cation exchange and typically displays characteristics of 'cation sorption'. The Zn(II) removal capacity decreases when solution pH decreases because of the competition with hydrogen ions for sorption sites, while the Zn(II) removal capacity increases under higher pH conditions, likely due to hydroxide precipitation. At an initial Zn(II) concentration of 5.0mM, the removal increases from 70% to 96% with the increase of initial pH from 3.0 to 7.0. We recommend Jeju scoria as an economic and efficient sorbent for Zn(II) in contaminated water. 相似文献
523.
Tamara Krügel Michelle Lim Klaus Gase Rayko Halitschke Ian T. Baldwin 《Chemoecology》2002,12(4):177-183
Summary. Research into the genetic basis of the ecological sophistication of plants is hampered by the availability of transformable
systems with a wealth of well-described ecological interactions. We present an Agrobacterium-mediated transformation system for the model ecological expression system, Nicotiana attenuata, a native tobacco that occupies the post-fire niche in the Great Basin Desert of North America. We describe a transformation
vector and a transformation procedure that differs from the standard cultivated tobacco transformation protocols in its use
of selectable markers, explants, media and cultivation conditions. We illustrate its utility in the transformations with genes
coding for key enzymes in the oxylipin cascade (lipoxygenase, allene oxide synthase, hydroperoxide lyase) in antisense orientations
and present high-throughput screens useful for the detection of altered phenotypes for the oxylipin cascade (green leaf volatiles
and jasmonic acid after wounding).
Received 14 March 2002; accepted 10 May 2002 相似文献
524.
Hursthouse AS Matthews JM Figures JE Iqbal-Zahid P Davies IM Vaughan DH 《Environmental geochemistry and health》2003,25(2):171-203
Detailed surveys of intertidal sediments have been performed along the north and south shores of the Inner Clyde estuary, UK. Surface sediment data reveal significant spatial variation in Cr content and an association with major sediment characteristics and location within the estuary. Depth variation for Cr and other heavy metals cannot be explained by variation in major geochemical controls such as grain size and organic matter and highlights the impact of historical contamination on sediment quality. These elevated levels at depth may still have environmental impact through redox-reactivity, in association with iron and manganese. Sequential extraction of sediments and pore water analysis of Cr(VI) and Cr(III) provide detailed information on release potential from the sediments. The implication of Cr mobility for biota in the estuary has been assessed by the analysis of a common marine bivalve, Mytilus edulis (Blue Mussel) and a burrowing polychaete, Nereis diversicolor (rag worm) from a number of survey sites. Bioconcentration factors for Mytilus indicate that the weakly held portion of sediment Cr is available for uptake and in the case of Nereis, bioaccumulation appears to be inhibited by sediment organic matter. 相似文献
525.
526.
A series of experiments using bulk precipitation collectors of the type used in the UK precipitation chemistry network measured the amounts of NH4+, SO42− and other ions that could be washed from funnels (diameter 15 cm) exposed to a wide range of NH3 and SO2 concentrations over periods from hours to days. In dry conditions, the average deposition flux of NH3 was between 50 and 120 nmol NH4+ funnel−1 d−1 (0.1–0.3 kg N ha−1 yr−1), and was independent of the concentration of NH3. Dry deposition of NH3 to wet funnels at small NH3 concentrations was almost 5 times that to dry funnels under the same conditions (average 240 nmol funnel−1 d−1; 0.7 kg ha−1 yr−1), and increased with increasing NH3 concentrations. The amount of NH4+ ions remaining on the funnel surface was inversely proportional to the vapour pressure deficit during the experiment. This result was interpreted as a dependence on the duration of surface wetness, with greater deposition of NH4+ when evaporation rates of surface water were small.The amount of SO2 deposited on funnel surfaces was closely related to the amount of NH3 deposited, in both wet and dry conditions, but was not strongly correlated with the SO2 concentration. At low NH3 and SO2 concentrations the average deposition to dry funnels was 70 nmol SO42− funnel−1 d−1 (0.5 kg ha−1 yr−1), and to wet funnels was approximately 2.5 times larger. The results are interpreted in terms of the balance between the rate of evaporation of surface water, and the rate of oxidation of SO2, which leads to the ‘fixing’ of NH4+ ions on the surface as involatile salts.It is predicted that dry deposition of NH3 to funnel surfaces across the UK Secondary Network could account for as much as one-half of the measured bulk wet deposition at sites where wet deposition of NH4–N is small. The amount of dry deposition depends on how long and how often funnel surfaces are wetted by rain or dew, and on the air concentrations of NH3. These predictions are based on funnels being wetted only once per day. More frequent wetting would increase the contribution from dry deposition, and the consequent overestimate of wet deposition of NH4–N across the UK by using data obtained from bulk collectors. To some extent this overestimate may be offset by microbial degradation and loss of NH4–N in weekly bulk precipitation samples during collection and storage. 相似文献
527.
Ellen L. Petticrew Ian G. Droppo Nives Ogrinc Brian Kronvang Jadran Faganeli 《Water, Air, & Soil Pollution: Focus》2006,6(5-6):365-369
The 10th International Symposium on Interactions Between Sediment and Water was held in Lake Bled, Slovenia from August 28 to September
3, 2005. Approximately 155 delegates, attended the symposium where talks and posters addressed five themes incorporating the
physical, chemical, biological, and/or management aspects of lacustrine, reverine, estuarine, and/or marine sediment were
presented. A review of the symposium themes and plenary talks was provided. As well, this symposiums’ focus is put into context
with respect to historical changes noted over the 29 years that the International Association for Sediment Water Science (IASWS)
has been meeting. 相似文献
528.
Counselling the parents following a diagnosis of fetal congenital heart disease (CHD) is as important a task for the fetal cardiologist, as the skill involved in achieving an accurate diagnosis. The counsellor will base prognosis not only on the diagnosis itself but also on the security of diagnosis, the stage in gestation and potential for change, the association with extracardiac malformations and the known results of treatment. Depending on the gestational age and legal situation the counsellor is operating in, termination of pregnancy may be one of the options to consider and one that should always be raised in discussion. Thus, the parents may be in the position of making a crucial decision concerning the management of the pregnancy on the basis of the information received, so it is vital that the counsellor is truly able to communicate with them, whatever be their level of understanding. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
529.
Tradable-permit schemes are becoming an increasingly popular technique for encouraging materials recovery and the diversion of waste from landfill. Such schemes operate using various forms of market-based trading of waste permits between polluters but usually rely on mandatory recycling targets to provide an incentive for trading. Using the UK's Packaging Recovery Note (PRN) scheme as a template, this paper examines the potential for permit trading where mandatory targets are absent and schemes must be driven solely by the financial benefits of reduced landfill costs and permit/material sales. The case examined is sterilized clinical waste, which has considerable recycling potential but suffers from health concerns and a poor public image. Interviews with healthcare and waste-management representatives indicate that although elements of the PRN scheme might prove appropriate for encouraging materials recovery, the absence of government targets and uncertain end markets for sterilized clinical waste present major obstacles to trading. Alternative incentives would therefore be required to catalyse schemes and develop recycling infrastructure. In the final analysis, thermal processing may be a more practical alternative to landfill than materials recovery for this particular waste stream. 相似文献
530.
Ian J. Bateman Ian H. Langford Naohito Nishikawa Iain Lake 《Journal of Environmental Planning and Management》2000,43(2):291-302
Recent debate following the rejection of the Environment Agency case regarding an application for water abstraction at Axford on the River Kennet has focused upon the benefits procedure employed for aggregating non-user benefits which underpinned the economic case put forward by the Agency (although this was not the reason cited by the inquiry for rejection of the case). Commentators have seen this case as setting an unfortunate precedent for the use of economic assessments in such resource management issues. The paper presents a number of highly tractable alternative methods for the aggregation of benefits estimates designed to address the central problems of the definition of a relevant aggregation population and a potential decay of values with increasing distance from a given valuation site. These methods are tested using data obtained from a national survey of non-users of a specific natural area. Results from this application indicate that simpler approaches such as that used at the Axford inquiry may result in aggregate benefits estimates which are very substantially larger than those produced by our proposed alternative approaches to aggregation. 相似文献