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271.
An assessment of the physicochemical characteristics of the rat hepatic receptors for 2,3,7,8-TCDD and for corticosteroid hormones reveals striking analogies between both receptor systems.  相似文献   
272.
Volatile iodinated organic compounds play an important role in the tropospheric photochemical system, but the current knowledge of the known sources and sinks of these alkyl iodides is still incomplete. This paper describes a new source of alkyl iodides from the pedosphere. Different organic-rich soils and humic acid were investigated for their release of volatile organoiodides. Six volatile organoiodides, iodomethane, iodoethane, 1-iodopropane, 2-iodopropane, 1-iodobutane and 2-iodobutane were identified and their release rates were determined. We assume an abiotic reaction mechanism induced by the oxidation of organic matter by iron(III). The influence of iron(III), iodide and pH on the formation of alkyl iodides was investigated. Additionally, different organic substances regarded as monomeric constituents of humus were examined for the production of alkyl iodides. Two possible reaction pathways for the chemical formation of alkyl iodides are discussed. As humic acids and iron(III) are widespread in the terrestrial environment, and the concentration of iodide in soil is strongly enriched (compared to seawater), this soil source of naturally occurring organoiodides is suggested to contribute significantly to the input of iodine into the troposphere.  相似文献   
273.
Ophiurid basket stars belonging to the family Gorgonocephalidae are distributed from the Arctic to the Antarctic and from the shallow subtidal to the deep sea, but their biology remains poorly known. In situ observations at the mouth of the Oslofjord by a remotely operated vehicle showed that Gorgonocephalus caputmedusae had a patchy distribution at 85 to 120 m water depth and frequently occurred in association with the gorgonian Paramuricea placomus and the coral Lophelia pertusa. Morphological and histological studies show that G. caputmedusae is well adapted to capture macroplanktonic prey. Histological examination of the arms revealed the presence of a thick layer of dermal mutable connective tissue which is probably an energy-efficient way to maintain its feeding posture against the current. This layer is connected to the nerve cord suggesting that the passive mechanical properties (stiffness) is controlled by the nervous system. In the distal parts of the arms, each segment has a pair of sticky tube feet and a sophisticated system of spines and hooks, which are connected to muscles and collagenous tendons. In combination, these features were shown, in an experimental flume study, to be used for capturing the locally abundant krill species Meganyctiphanes norvegica. This is the first documentation of G. caputmedusae of this kind.  相似文献   
274.
The mechanisms and functions of mixed-species shoaling were investigated in two sympatric species of cyprinids, the chub and the European minnow, from the river Wharfe where they comprised approximately 70% of all year 0+ fish over a 20-year survey. Chub preferred conspecific shoals over heterospecific ones with olfactory cues being more important than visual ones for shoal choice. This preference was consistent with measurements of length:flank area ratios and length:weight ratios which suggest that both species are similar in appearance. When presented with mixed-species shoals, chub increased the percentage time spent with stimulus shoals with increasing proportions of conspecifics. Feeding experiments suggest that the preference for conspecific shoals is driven by interspecific competition (with minnows out-competing similar-sized chub) and the oddity effect. The importance of this work in the context of species assortment in free-ranging shoals is discussed.  相似文献   
275.
276.
The effect of wind direction on ozone levels: a case study   总被引:3,自引:0,他引:3  
This paper provides an illustrative case study on how the wind direction plays an important role in determining the ozone levels, in a suburb of Houston. Circular correlation and circular regression methods are used in the analysis and the primary goal is to illustrate how circular data analytic methods help in analyzing certain environmental issues. Received: August 2003/Revised: June 2004  相似文献   
277.
This paper analyses some of the higher education and research capacity building experiences gained from 1998-2006 by Danish and Malaysian universities. The focus is on waste management, directly relating to both the environmental and socio-economic dimensions of sustainable development. Primary benefits, available as an educational legacy to universities, were obtained in terms of new and enhanced study curricula established on Problem-oriented Project-based Learning (POPBL) pedagogy, which strengthened academic environmental programmes at Malaysian and Danish universities. It involved more direct and mutually beneficial cooperation between academia and businesses in both countries. This kind of university reach-out is considered vital to development in all countries actively striving for global and sustainable development. Supplementary benefits were accrued for those involved directly in activities such as the 4 months of field studies, workshops, field courses and joint research projects. For students and academics, the gains have been new international dimensions in university curricula, enhanced career development and research collaboration based on realworld cases. It is suggested that the area of solid waste management offers opportunities for much needed capacity building in higher education and research, contributing to sustainable waste management on a global scale. Universities should be more actively involved in such educational, research and innovation programmes to make the necessary progress. ISWA can support capacity building activities by utilizing its resources--providing a lively platform for debate, securing dissemination of new knowledge, and furthering international networking beyond that which universities already do by themselves. A special challenge to ISWA may be to improve national and international professional networks between academia and business, thereby making education, research and innovation the key driving mechanisms in sustainable development in solid waste management.  相似文献   
278.
Increasing reservoir storage is commonly proposed to mitigate increasing water demand and provide drought reserves, especially in semiarid regions such as California. This paper examines the value of expanding surface reservoir capacity in California using hydroeconomic modeling for historical conditions, a future warm‐dry climate, and California's recently adopted policy to end groundwater overdraft. Results show expanding surface storage capacity rarely provides sizable economic value in most of California. On average, expanding facilities north of California's Delta provides some benefit in 92% of 82 years modeled under historical conditions and in 61% of years modeled in a warm‐dry climate. South of California's Delta, expanding storage capacity provides no benefits in 14% of years modeled under historical conditions and 99% of years modeled with a warm‐dry climate. Results vary across facilities between and within regions. The limited benefit of surface storage capacity expansion to statewide water supply should be considered in planning California's water infrastructure.  相似文献   
279.
Urban areas worldwide are challenged by climate change and urban flooding. Within the academic literature, adaptive measures that can be integrated into other issues such as recreation, nature reserves, and social issues are considered the way forward. Adaptation has recently become a mandatory planning theme for Danish municipalities, which in the absence of established practices are struggling to find the best institutional set-up to address adaptation as an integrated issue. Based on a case study of an integrated project organised as a partnership, this article identifies and discusses governance challenges that must be addressed if municipalities are to benefit from synergies through integrated projects. The municipality in question has established a partnership with housing organisations, foundations, and a utility company as well as facilitated a dialogue with citizens and institutions to address flooding threats and social issues at the neighbourhood scale. Because of strong political and leadership support, funding from partners, and good project facilitation both partners and politicians are enthusiastic about the project and its potential. Several challenges, however, needed to be addressed, particularly in relation to clashing norms from different governance paradigms. This is an issue requiring more attention both in research and practice.  相似文献   
280.
Radium and heavy metal contaminated tailings and scales resulting from Polish hard coal mining were investigated for their mobilisation potential by using leaching methods. The main focus is set on a three-step extraction procedure proposed by BCR (Bureau Communautaire de Référence, now Standards Measurements and Testing Programme) of the European Union, which was used for investigating the availability of radium isotopes. In addition, the results of a Polish extraction procedure for the heavy metals' water solubility are presented for rough comparison. After a special treatment, the BCR-reagents were measured by gamma-spectrometry to define their radium activity concentrations; the heavy metal content in the water soluble fractions was determined by ICP-AES. The samples were collected at two different sites influenced by the discharge of pit water from hard coal mining. The tailings were taken from a former tailing pond, which now is no longer in use, but the settled material is still present. At another abandoned and meanwhile flooded tailing pond, the scales were scraped from the inside of a discharge tube. The results obtained show that there is different leaching behaviour between the radium isotopes. The tailings being characterised by surface adsorbed radium provide up to 25% of the initial (226)Ra content, (228)Ra is altogether leached up to 15%. The scales comprise stable radiobaryte (Ba[Ra]SO(4)) and can be considered as being unable to provide radium isotopes, since no trace of radium dissolution was observed. The leaching behaviour of heavy metals is similar to that of radium. Mn, Ni and Zn are dissolved by water from the tailings; the scales do not provide any.  相似文献   
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