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41.
Adaptive performance is a facet of performance that reflects acquiring enhanced competencies in response to change. Micro‐level researchers have assumed that adaptive performance is beneficial for task performance. Similarly, macro‐level researchers have suggested that organizations need to attend to, monitor, and respond to contingencies in their environments for adaptive performance to be beneficial for firm performance. Drawing from the attention‐based theory of the firm and resource theory, we suggest that perceptions of organizational politics and individual differences in conscientiousness constitute contingencies of the adaptive performance–task performance relationship. In a sample of 92 call center employees, we found that adaptive performance is positively associated with task performance but that conscientiousness and organizational politics jointly influence the adaptive performance–task performance relationship. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
42.
María Pía Areal M. Lorena Arciniegas Fernanda Horst Verónica Lassalle Francisco H. Sánchez Vera A. Alvarez Jimena S. Gonzalez 《Journal of Polymers and the Environment》2018,26(8):3129-3138
Scientific and technological researches are devoted to obtain materials capable of retaining different kinds of pollutants, contributing to contamination solutions. In this context, hydrogels have emerged as great candidates because of their excellent absorption properties as well as good mechanical, thermal and chemical properties. More specifically, ferrogels (magnetic gels) present the extra advantage of being easily manipulated by a permanent magnet. Here, we present the results derived from the application of ferrogels as efficient tools to extract heavy metal pollutants from wastewater samples. The gels were prepared following the method of freezing and thawing of a polyvinyl alcohol aqueous solution with magnetic nanoparticles coated with polyacrylic acid. Ferrogels were fully characterized and their ability to retain Cu2+ and Cd2+, as model heavy metals, was studied. Thus kinetics and mechanisms of adsorption were evaluated and modeled. The concentration of MNPs on the PVA matrix was key to improve the adsorption capability (approximately the double of retention is improved by the MNPs addition). The adsorption kinetics was determined as pseudo-second order model, whereas the Langmuir model was the most appropriate to explain the behavior of the gels. Finally reuse ability was evaluated to determine the real potential of these materials, the ferrogels demonstrated high efficiency up to about five cycles, retaining about 80–90% of their initial adsorption capability. All the results indicated that the materials are promising candidates able to compete with the commercial technology regarding to water remediation. 相似文献
43.
The mangrove channels of Bahía Magdalena, Mexico, are important developmental areas for juvenile green, or black turtles (Chelonia mydas), but incidental bycatch and illegal hunting threaten population persistence. We studied size distribution, condition index
(CI), growth rates, and mortality of black turtles in Estero Banderitas, the largest mangrove channel in Bahía Magdalena,
to supply information for the development of effective conservation strategies. A total of 213 black turtles (including 88
recaptures) were caught in entanglement nets between July 2000 and July 2003. Average yearly catch per unit of effort (CPUE,
1 unit: 100 m of net fishing for 12 h) dropped during the study from 2.19 to 0.76. About 97% of all turtles were considered
juveniles, average size was 54.6 ± 9.5 cm. Turtles were significantly smaller at the head of Estero Banderitas than in the
central part of the Estero and in the open bay, indicating size-based habitat segregation. Average growth rate was 1.62 cm/year
and declined with increasing size. Growth was seasonal and three times higher in summer (0.28 cm/month) than in winter (0.09 cm/month),
body CI was also significantly higher during the summer months. A seasonalized von Bertalanffy growth function (VBGF) was
used to model growth for the size range studied (43–73 cm SCL), with the parameters: L
∞ = 101 cm SCL; K = 0.04 year−1; t
0 = 0; C = 0.4 and t
s = 0.75. Growth data indicate that black turtles may spend up to 20 years in Bahía Magdalena before they reach maturity at
about 77 cm SCL. The total mortality estimate (Z) from the length converted catch curve was 0.16, corresponding to a yearly survival probability of 0.85. 相似文献
44.
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46.
Astrid Geschke V. Koch J. Schabronath W. Veerkamp R. Wittlinger 《Environmental Sciences Europe》1992,4(4):198-207
Different concepts for hazard assessment of 2,3,7,8-TCDD in soil are presented and a comparison of the approaches is made. Both approaches clearly show that hazard assessment should be site and use specific. 相似文献
47.
48.
Hydrodynamics,diffusion-boundary layers and photosynthesis of the seagrasses Thalassia testudinum and Cymodocea nodosa 总被引:2,自引:0,他引:2
E. W. Koch 《Marine Biology》1994,118(4):767-776
Photosynthetic rates of aquatic plants frequently increase with increasing current velocities. This is presumably due to a reduction in the thickness of the diffusion boundary-layer which allows for a higher carbon availability on the plant surface. Blades of the seagrasses Thalassia testudinum and Cymodocea nodosa exposed to different current velocities under controlled laboratory conditions, showed increased photosynthetic rates with increasing flow only at low current velocities (expressed as blade friction velocities, u
*). Carbon saturation of photosynthetic processes occurred at a relatively low u
* level (0.25 cm s-1) for T. testudinum collected from a calm environment compared to C. nodosa (0.64 cm s-1) collected from a surf zone. No further enhancement of photosynthetic rates was observed at higher u
* levels, suggesting limitations in carbon diffusion through the boundary layer below critical u
* levels and possible limitations in carbon fixation by the enzymatic system at higher u
* levels. These results, as well as those of previous theoretical studies, assumed the flow on the immediate seagrass-blade surface to be hydrodynamically smooth. The presence of epiphytes and attached debris causes the surface of in situ seagrass blades to be exposed to flows ranging from smooth to rough-turbulent. As a consequence, the boundary-layer thickness on moderately epiphytized blades under medium to high flow-conditions is not continuous, but fluctuates in time and space, enhancing carbon transport. In situ u
* levels measured directly on blades of seagrasses indicate that T. testudinum and C. nodosa can be exposed to conditions under which the boundary layer limits photosynthesis during short periods of time (milliseconds) during low-energy events. As waves cause the thickness of the diffusion boundary-layer to fluctuate constantly, carbon-limiting conditions do not persist for prolonged periods. 相似文献
49.
Summary. Ponderosa pine, Pinus ponderosa Laws. (Pinaceae), forests in Arizona have suffered from a nine-year period of drought and bark beetle, Ips lecontei Swaine (Coleoptera: Scolytidae), outbreaks. Abiotic and biotic stress in ponderosa pine results in the induced synthesis
of certain monoterpenes that may in turn affect bark beetle behavior and survival. In this study, we investigate whether induced
monoterpene production could result in a different monoterpene composition that remains stored in the needles or the trunk
resin of the tree. Needle and resin samples in addition to trunk cores were collected from ponderosa pines at three locations
in Arizona. Ungulate browsing induced a significant increase in limonene (P=0.010) and in chemodiversity (P=0.009), a measure
of the evenness of distribution among the monoterpenes present in needles. We compared the level of ‘stress’ of the trees
by measuring the thickness of annual rings in living trees and those that were killed by bark beetles. Where drought occurred,
the spacing of annual rings from the last 10 years of trees killed by bark beetles was significantly smaller (P=0.020) compared
to living trees. There was no difference in the monoterpene composition between the core sections of closest spacing of annual
rings (stressed years) compared to the sections of widest spacing, which indicates that monoterpenes are distributed evenly
throughout the extended resin system. In the area where the degree of drought was less overall, none of the individual monoterpenes
present in the resin was related to bark beetle killed trees. However, about half the living pines had resin in which one
of the major monoterpenes (α-pinene, Δ3-carene, and limonene) was absent, and these trees had a lower monoterpene chemodiversity compared to trees killed by bark
beetles. Trees with these three major monoterpenes, corresponding to the average relative proportion in living pines at that
location, may sustain higher selection and colonization by bark beetles. 相似文献
50.