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141.
Peter H. Becker Robert W. Furness Diana Henning 《Environmental monitoring and assessment》1993,28(3):255-262
In 1991 we compared eggs, down and body feathers of chicks of Common Terns, Herring Gulls and Black-headed Gulls in their utility to assess contamination with mercury. Like eggs feathers distinctly show interspecific and intersite differences in contamination. Highest levels were found in Common Terns, lowest in Black-headed Gulls. Chicks hatched at the Elbe had much higher mercury levels than those in other areas of the German North Sea coast. Conversion ratios between tissues have to be used with caution. 相似文献
142.
The metal ion binding characteristics of particulate matter obtained from column experiments on the anaerobic digestion of solid waste were studied using a titrimetric approach. The experimental set-up allowed us to study the dynamics of particle bound ligand concentrations during digestion processes typically found in landfills.We developed a continuous titration method by simultaneously using a Cd-sensitive and pH electrode and combining metal and acid/base titrations. This technique allows for a more precise determination of pKa-log KM pairs for each ligand than metal titrations alone. The results were compared with titration methods using differential pulse anodic stripping voltammetry (DPASV) and atomic absorption spectroscopy (AAS) with longer equilibration times in order to further characterize ligand properties such as reaction kinetics, the electrochemical lability of the respective complex during DPASV, the distinction between metal adsorption to particulate matter and metal complexation by soluble ligands adhered to particles, reversibility of the binding process by competition studies, and resistance against purging with nitrogen gas.The properties of seven major metal binding ligands were identified and assignments to the most likely functional groups were made. The most important ligand properties are for ligand A: pKa ≈ 9.2, log Kcd ≈ 7.0 fast reaction kinetics (mercapto groups); ligand B: pKa = 4.8, log KCd ≈ 6.0, slow reaction kinetics (chelates with 3 or 4 carboxylic groups); ligand C: pKa ≈ 6.0, log KCd ≈ 13.0, irreversible metal binding at basic pH-values (uptake inside bacterial cells); ligand D: pKa = 7.7, log KCd = 4.0, runs parallel to N content of particulate matter with digestion time (primary amines neighboring oxo groups); ligand E: pKa ≈ 12.0, log KCd = 9.0, runs parallel to P content of particulate matter (phosphate); ligand F:pKa > 9.0, log KCdf = pKa + 0.4, runs parallel to N content of particulate matter (primary amines neighboring SH groups); and ligand G: pKa ≤ 4.8, log KPb ≈ 4.3, strong Pb2+ ligand, even at low pH-values.Metal ions were found to be irreversibly bound by ligand C at low heavy-metal concentratins, whereas at higher concentrations the binding is reversible and can be predicted using the mass of the digestion process (methanogenic phase). All other ligands have their concentration maximum in the transition phase between acetogenic and methanogenic phase. 相似文献
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Organizational neuroscience has great promise for advancing organizational research and practice. The field, however, is developing rapidly and has also become the subject of technological and methodological challenges that must be considered when conducting or interpreting neuroscience research as applied to organizational behavior. We explore four issues we deem to be important in understanding the role of neuroscience in organizational behavior research: (i) neuroscientific research and reductionism; (ii) the need to address methodological and technological challenges in conducting this type of research; (iii) how neuroscientific research is meaningful in organizations (the “So what?” issue); and (iv) neuroscience as just another management fad. In addressing these issues, we hope to set out a roadmap that will enable organizational scholars to avoid past mistakes and thus serve to advance multidisciplinary research in organizational behavior using neuroscientific approaches. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
146.
Contrary to many studies regarding the efficient use of resources that measure the marginal cost of nature conservation by looking at a specific objective and asks about efficient way to achieve it, this article tries to estimate the (marginal) cost of nature conservation in a more flexible way. Instead of looking at a specific objective and then not being able to compare different objectives, we take an approach that is based on experts’ valuation of increased satisfaction from nature conservation. We trace the marginal cost of conservation from their answers and use official cost statistics. Officials in the Israeli Nature and Parks Authority (NPA) were surveyed to determine the activities required to increase the level of nature conservation in two districts of the NPA as well as nationwide. We determined the costs of these proposed activities, and subsequently were able to calculate the total cost and marginal cost of conservation efforts. When operating on a limited budget, conservation authorities can use these schedules as an additional tool to help determine the efficiency of different proposed activities both on a regional scale and nationwide, and to ensure the sustainability of the resulting conservation. In addition, our results demonstrate the existence of economies of scale in nature conservation, and the benefit of both bottom-up and top-down decision processes in nature conservation. 相似文献
147.
A quantitative analysis is presented of not only the direct but also of the indirect effects resulting from the fact that waste in any one part of a nation's industrial structure also induces waste in other parts. 相似文献
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Soil fumigation using shank injection creates high fumigant concentration gradients in soil from the injection point to the soil surface. A temperature gradient also exists along the soil profile. We studied the degradation of methyl isothiocyanate (MITC) and 1,3-dichloropropene (1,3-D) in an Arlington sandy loam (coarse-loamy, mixed, thermic Haplic Durixeralf) at four temperatures and four initial concentrations. We then tested the applicability of first-order, half-order, and second-order kinetics, and the Michaelis-Menten model for describing fumigant degradation as affected by temperature and initial concentration. Overall, none of the models adequately described the degradation of MITC and 1,3-D isomers over the range of the initial concentrations. First-order and half-order kinetics adequately described the degradation of MITC and 1,3-D isomers at each initial concentration, with the correlation coefficients greater than 0.78 (r2> 0.78). However, the derived rate constant was dependent on the initial concentration. The first-order rate constants varied between 6 and 10x for MITC for the concentration range of 3 to 140 mg kg(-1), and between 1.5 and 4x for 1,3-D isomers for the concentration range of 0.6 to 60 mg kg(-1), depending on temperature. For the same initial concentration range, the variation in the half-order rate constants was between 1.4 and 1.7x for MITC and between 3.1 and 6.1x for 1,3-D isomers, depending on temperature. Second-order kinetics and the Michaelis-Menten model did not satisfactorily describe the degradation at all initial concentrations. The degradation of MITC and 1,3-D was primarily biodegradation, which was affected by temperature between 20 and 40 degrees C, following the Arrhenius equation (r2 > 0.74). 相似文献
150.
This study of a random sample of self-employed and non-self-employed dentists tests the French, Rodgers, and Cobb (1974) hypothesis, which predicts a curvilinear relationship between psychological strain and person-environment fit. Self-employed dentists had lower strain scores (based on measures of job satisfaction and self-esteem) and greater congruency in P-E fit (based on comparisons of preferred and typical hours in practice) than dentists who were not self-employed. The relationship between strain and P-E fit among self-employed dentists was curvilinear. Both self-esteem and job satisfaction were higher for dentists with a congruent fit between typical and preferred workload and lower for dentists with incongruent fit. 相似文献