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331.
Current organizational theory and research affirm the beneficial effects of experiencing positive affect at work. In recent years, researchers have begun to question the popular notion that the more positive affect at work, the better—that more positive affect is desirable for work‐related outcomes. In this article, we propose a rationale for why more positive affect may not be better for proactive behaviors at work. Findings from two field studies using two unique data sources demonstrate support for our hypothesis, suggesting that intermediate levels of positive affect are most beneficial for proactive behaviors. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
332.
Fritz Bopp 《Die Naturwissenschaften》1955,42(19):531-532
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Bentonites are widely used for waste repository systems because of their hydrodynamic, surface and chemical-retention properties. MX 80 bentonite (bentonite of Wyoming) contains approximately 85% Na/Ca-montmorillonite and 15% accessory minerals. The dominant presence of Na/Ca-montmorillonite in this clay mineral could cause it to perform exceptionally well as an engineered barrier for a radioactive waste repository because this buffer material is expected to fill up by swelling the void between canisters containing waste and the surrounding ground. However, the Na/Ca-montmorillonite could be transformed to other clay minerals as a function of time under repository conditions. Previous modelling studies based on the hydrolysis reactions have shown that the Na/Ca-montmorillonite-to-Ca-montmorillonite conversion is the most significant chemical transformation. In fact, this chemical process appears to be a simple cation exchange into the engineered barrier. The purpose of the present study was two-fold. Firstly, it was hoped to predict the newly formed products of bentonite-fluid reactions under repository conditions by applying a thermokinetic hydrochemical code (KIRMAT: Kinetic Reactions and Mass Transport). The system modelled herein was considered to consist of a 1-m thick zone of water-saturated engineered barrier. This non-equilibrated system was placed in contact with a geological fluid on one side, which was then allowed to diffuse into the barrier, while the other side was kept in contact with iron-charged water. Reducing initial conditions ( [P(O)2 approximately equals 0] ; Eh=-200 mV) and a constant reaction temperature (100 degrees C) were considered. Secondly, it was hoped to estimate the influence of inter-layer cations (Ca and Na) on the swelling behaviour of the MX 80 bentonite by using an isothermal system of water vapour adsorption and an environmental scanning electron microscope (ESEM) coupled with a digital image analysis (DIA) program. Here, the MX 80 bentonite was previously treated with concentrated solutions (1N) of calcium and sodium chlorides. The results confirmed that the Na/Ca-montmorillonite-to-Ca-montmorillonite conversion was the main chemical transformation in the bentonite barrier under repository conditions. A simplified method (based on volume balance) has shown that the swelling capacity of the engineered barrier would be slightly affected after 1000 years of diffusion-reaction because the volume of neo-formed swelling clays is almost directly proportional to the volume of transformed initial-montmorillonite. Minimal neo-formation of saponites, vermiculites and chlorites was also observed. In addition, an isothermal system of water adsorption and ESEM-DIA methods showed that in the raw-bentonite-to-Ca-bentonite exchange there is a small decrease in the amount of adsorbed water and the swelling potential. 相似文献
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338.
Fritz A. Seiler 《Environment international》1986,12(6)
Calculations of attributable risks, probabilities of causation, and assigned shares attracted increasing interest recently, particularly since the enactment of the Orphan Drug Act. Although efforts have been limited mostly to radiation as the toxic agent, the concept is general to all toxicants. In this paper, the systematic and random uncertainties in calculations of assigned shares are reviewed globally, and possibilities for their reduction are discussed. In addition, an algebraic study is made of the influence of random uncertainties in the input parameters on the random error of the assigned shares. Three dose-effect functions, appropriate for the low-dose, low-effects regions that are of interest here, are chosen for this investigation, and the algebraic properties of the random errors of the assigned shares are discussed. For shares near 0 and 1, the errors are shown to be small and to depend linearly on the value of the shares; the errors are largest for values of the shares near 50%, that is, in the region of almost equal or equal shares. 相似文献
339.
Mammalian hibernation, which lasts on average for about 6 months, can reduce energy expenditure by >90% in comparison to active
individuals. In contrast, the widely held view is that daily torpor reduces energy expenditure usually by about 30%, is employed
for a few hours every few days, and often occurs only under acute energetic stress. This interpretation is largely based on
laboratory studies, whereas knowledge on daily torpor in the field is scant. We used temperature telemetry to quantify thermal
biology and activity patterns of a small arid-zone marsupial, the stripe-faced dunnart Sminthopsis macroura (16.9 g), in the wild and to test the hypothesis that daily torpor is a crucial survival strategy of this species in winter.
All individuals entered torpor daily with the exception of a single male that remained normothermic for a single day (torpor
on 212 of 213 observation days, 99.5%). Torpor was employed at air temperatures (T
a) ranging from approximately −1°C to 36°C. Dunnarts usually entered torpor during the night and aroused at midday with the
daily increase of T
a. Torpor was on average about twice as long (mean 11.0 ± 4.7 h, n = 8) than in captivity. Animals employed sun basking during rewarming, reduced foraging time significantly, and occasionally
omitted activity for several days in sequence. Consequently, we estimate that daily torpor in this species can reduce daily
energy expenditure by up to 90%. Our study shows that for wild stripe-faced dunnarts daily torpor is an essential mechanism
for overcoming energetic challenges during winter and that torpor data obtained in the laboratory can substantially underestimate
the ecological significance of daily torpor in the wild. 相似文献
340.
Torpor and basking in a small arid zone marsupial 总被引:3,自引:3,他引:0
The high energetic cost associated with endothermic rewarming from torpor is widely seen as a major disadvantage of torpor.
We tested the hypothesis that small arid zone marsupials, which have limited access to energy in the form of food but ample
access to solar radiation, employ basking to facilitate arousal from torpor and reduce the costs of rewarming. We investigated
torpor patterns and basking behaviour in free-ranging fat-tailed dunnarts Sminthopsis crassicaudata (10 g) in autumn and winter using small, internal temperature-sensitive transmitters. Torpid animals emerged from their resting
sites in cracking soil at ∼1000 h with body temperatures as low as 14.6°C and positioned themselves in the sun throughout
the rewarming process. On average, torpor duration in autumn was shorter, and basking was less pronounced in autumn than in
winter. These are the first observations of basking during rewarming in S. crassicaudata and only the second direct evidence of basking in a torpid mammal for the reduction of energetic costs during arousal from
torpor and normothermia. Our findings suggest that although overlooked in the past, basking may be widely distributed amongst
heterothermic mammals. Therefore, the energetic benefits from torpor use in wild animals may currently be underestimated. 相似文献