916 resultados para shift-share


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La presente investigación tiene por objeto analizar el cambio de paradigma en las organizaciones como fundamento del liderazgo ético desde una realidad postmoderna a fin de detectar la necesidad de un liderazgo ético en las organizaciones donde los líderes sean formadores de valores a través del modelaje directivo; es un estilo de liderazgo en el que la visión ética, sistémica e integradora son unas de las principales aptitudes que el líder ético ha de poner en la práctica. Se han desarrollado teorías de liderazgo centradas no tanto en los rasgos o comportamientos de los líderes, sino en la relación entre líder y sus seguidores

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This presentation explains a dozen tools and paradigm shifts that teachers should apply in transformative ways to working with their students, how Web 2.0, tagging, and RSS are crucial to this process, and how teachers can develop their own personal learning networks to practice continuous lifelong learning and 'teacher autonomy' before applying these concepts to students.

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Pteropods are an important component of the zooplankton community and hence of the food web in the Fram Strait. They have a calcareous (aragonite) shell and are thus sensitive in particular to the effects of the increasing CO2 concentration in the atmosphere and the associated changes of pH and temperature in the ocean. In the eastern Fram Strait, two species of thecosome pteropods occur, the cold water-adapted Limacina helicina and the subarctic boreal species Limacina retroversa. Both species were regularly observed in year-round moored sediment traps at ~ 200-300 m depth in the deep-sea long-term observatory HAUSGARTEN (79°N, 4°E). The flux of all pteropods found in the trap samples varied from < 20 to ~ 870 specimen/m**2/d in the years 2000-2009, being lower during the period 2000-2006. At the beginning of the time series, pteropods were dominated by the cold-water-adapted L. helicina, whereas the subarctic boreal L. retroversa was only occasionally found in large quantities (> 50/m**2/d). This picture completely changed after 2005/6 when L. retroversa became dominant and total pteropod numbers in the trap samples increased significantly. Concomitant to this shift in species composition, a warming event occurred in 2005/6 and persisted until the end of the study in 2009, despite a slight cooling in the upper water layer after 2007/8. Sedimentation of pteropods showed a strong seasonality, with elevated fluxes of L. helicina from August to November. Numbers of L. retroversa usually increased later, during September/October, with a maximum at the end of the season during December/January. In terms of carbonate export, aragonite shells of pteropods contributed with 11-77% to the annual total CaCO3 flux in Fram Strait. The highest share was found in the period 2007 to 2009, predominantly during sedimentation events at the end of the year. Results obtained by sediment traps occasionally installed on a benthic lander revealed that pteropods also arrive at the seafloor (~ 2550 m) almost simultaneous with their occurrence in the shallower traps. This indicates a rapid downward transport of calcareous shells, which provides food particles for the deep-sea benthos during winter when other production in the upper water column is shut down. The results of our study highlight the great importance of pteropods for the biological carbon pump as well as for the carbonate system in Fram Strait at present, and indicate modifications within the zooplankton community. The results further emphasize the importance of long-term investigation to disclose such changes.

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Identification of a sediment/basement contact using seismic reflection recordings has proven to be extremely difficult in wide areas of the North Pacific Ocean owing to the presence of massive, highly reflective chert layers within the sediment column. Leg 136 of the Ocean Drilling Program recovered coherent pieces of chert of sufficient size for the first comprehensive laboratory measurements of the seismic properties of this material. Compressional-wave velocities of six samples at 40-MPa confining pressure averaged 5.33 km/s, whereas shear-wave velocities at the same pressure averaged 3.48 km/s. Velocities were independent of porosity, which ranged from 5% to 13%, suggesting that pores within the samples were mostly high aspect ratio vugs as opposed to low aspect ratio cracks. Back-scattered electron images made with a scanning electron microscope confirmed this observation. Acoustic impedances were calculated for the chert samples and from shipboard measurements of the red clay sediment overlying the chert layers. An extremely large compressional-wave reflection coefficient (0.73) characterized the interface between the two lithologies. A synthetic seismogram was calculated using chert and typical pelagic carbonate properties to illustrate the influence of chert layers on a marine seismic-reflection section. Compressional-wave to shear-wave velocity ratios of the chert samples (Vp/Vs =1.53) are close to that of single-crystal quartz in spite of variable porosity. Shear-wave reflection coefficients are estimated to be approximately 0.94. A compressional-wave reflection coefficient for a basement/sediment (carbonate) interface is estimated to be approximately 0.50, significantly less than that of sediment/chert.

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Anthropogenic increases in the partial pressure of CO2 (pCO2) cause ocean acidification, declining calcium carbonate saturation states, reduced coral reef calcification and changes in the compositions of marine communities. Most projected community changes due to ocean acidification describe transitions from hard coral to non-calcifying macroalgal communities; other organisms have received less attention, despite the biotic diversity of coral reef communities. We show that the spatial distributions of both hard and soft coral communities in volcanically acidified, semi-enclosed waters off Iwotorishima Island, Japan, are related to pCO2 levels. Hard corals are restricted to non-acidified low- pCO2 (225 µatm) zones, dense populations of the soft coral Sarcophyton elegans dominate medium- pCO2 (831 µatm) zones, and both hard and soft corals are absent from the highest- pCO2 (1,465 µatm) zone. In CO2-enriched culture experiments, high- pCO2 conditions benefited Sarcophyton elegans by enhancing photosynthesis rates and did not affect light calcification, but dark decalcification (negative net calcification) increased with increasing pCO2. These results suggest that reef communities may shift from reef-building hard corals to non-reef-building soft corals under pCO2 levels (550-970 µatm) predicted by the end of this century, and that higher pCO2 levels would challenge the survival of some reef organisms.

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Effects of ocean acidification on Emiliania huxleyi strain RCC 1216 (calcifying, diploid life-cycle stage) and RCC 1217 (non-calcifying, haploid life-cycle stage) were investigated by measuring growth, elemental composition, and production rates under different pCO2 levels (380 and 950 µatm). In these differently acclimated cells, the photosynthetic carbon source was assessed by a (14)C disequilibrium assay, conducted over a range of ecologically relevant pH values (7.9-8.7). In agreement with previous studies, we observed decreased calcification and stimulated biomass production in diploid cells under high pCO2, but no CO2-dependent changes in biomass production for haploid cells. In both life-cycle stages, the relative contributions of CO2 and HCO3 (-) uptake depended strongly on the assay pH. At pH values =< 8.1, cells preferentially used CO2 (>= 90 % CO2), whereas at pH values >= 8.3, cells progressively increased the fraction of HCO3 (-) uptake (~45 % CO2 at pH 8.7 in diploid cells; ~55 % CO2 at pH 8.5 in haploid cells). In contrast to the short-term effect of the assay pH, the pCO2 acclimation history had no significant effect on the carbon uptake behavior. A numerical sensitivity study confirmed that the pH-modification in the (14)C disequilibrium method yields reliable results, provided that model parameters (e.g., pH, temperature) are kept within typical measurement uncertainties. Our results demonstrate a high plasticity of E. huxleyi to rapidly adjust carbon acquisition to the external carbon supply and/or pH, and provide an explanation for the paradoxical observation of high CO2 sensitivity despite the apparently high HCO3 (-) usage seen in previous studies.

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Switzerland held federal elections on 18 October, with the conservative Swiss People’s Party winning the largest share of the votes. Daniel Bochsler, Marlène Gerber and David Zumbach write that while the increase in vote share for the Swiss People’s Party was relatively limited, the party managed to significantly increase the number of seats it holds in Switzerland’s lower house of parliament, the National Council. Nevertheless, the party is unlikely to make substantial gains in the country’s upper house, the Senate, as it traditionally struggles under the two-round electoral system used in Senate elections.

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Providing price incentives to farmers is usually considered essential for agricultural development. Although such incentives are important, regarding price as the sole explanatory factor is far from satisfactory in understanding the complex realities of agricultural production in Africa. By analyzing the share contracts widely practiced in Ghana, this article argues that local institutions such as land tenure systems and agrarian contracts provide strong incentives and disincentives for agricultural production. Based on data derived from fieldwork in the 1990s, the study analyzes two types of share contracts and the incentive structures embedded in them. The analysis reveals that farmers' investment behavior needs to be understood in terms of both short-term incentive to increase yield and long-term incentive to strengthen land rights. The study concludes that the role of price incentives in agricultural production needs to be reconsidered by placing it in wider incentive structures embedded in local institutions.