Suchergebnisse

Abstract
Background
Toxicants often occur simultaneously. Some combinations show synergistic combined effects that go far beyond what is predicted with current effect models. Up until now, only the combined additive effects of similar acting chemicals have been assessed accurately, whereas the combined effects of dissimilar acting chemicals have been greatly underestimated in many cases.

Results
Here, we use the individual tri-phasic concentration–response relationship of two toxicants with different modes of action to model their combined synergistic effect on Daphnia magna. The novel stress addition approach (SA) predicted the combined effects (LC50) of different esfenvalerate and prochloraz combinations with an uncertainty factor of 2.8 at most, while the traditional effect addition (EA) and concentration addition (CA) approaches underestimated the combined effect by a factor of up to 150 and 660, respectively. Data of the single substance concentration–response relationships and on their combined effects enable to determine the degree of synergism. For the evaluation of the combined toxicant effect, we provide the approach as R package and as Indicate model (http://www.systemecology.eu/indicate/).

Conclusion
Adding stressors arithmetically, considering non-monotonic cause–effect relationships, is a decisive component in predicting the combined effects of multiple stressors within test systems. However, the extent of the synergistic effects that multiple stressors exert on populations within the ecosystem context is still highly controversial. Various processes are relevant at the ecosystem level, which are not considered in laboratory studies. However, the present work serves as a building block for understanding the effects of multiple stressors in the field.

Significant ambiguity remains in the literature regarding the conceptualization of organizational ambidexterity. We unpack this construct into one with two dimensions we term the balance dimension of ambidexterity (BD) and the combined dimension of ambidexterity (CD). BD corresponds to a firm's orientation to maintain a close relative balance between exploratory and exploitative activities, whereas CD corresponds to their combined magnitude. We reason that these dimensions are conceptually distinct, and rely on different causal mechanisms to enhance firm performance. We find that over and above their independent effects, concurrent high levels of BD and CD yield synergistic benefits. We also find that BD is more beneficial to resource-constrained firms, whereas CD is more beneficial to firms having greater access to internal and/or external resources. These results indicate that managers in resource-constrained contexts may benefit from a focus on managing trade-offs between exploration and exploitation demands, but for firms that have access to sufficient resources, the simultaneous pursuit of exploration and exploitation is both possible and desirable.

This writing positions the accompanying volume within a realm of complications of climate change journalism that operates amid recognized pressures of journalistic practice through notions of political economy, the social and cultural influences shaping news explanations, and critical interpretations of the current global crisis of a warming planet. Specifically, this volume is interested in how journalism may function among "synergistic effects" of climate change, the compounded impact of severe weather, social and political responses to changing global warming, and the often-unfortunate results and impacts on our environments as global communities attempt to address climate events already challenging for journalists to cover and the social and cultural outcomes associated with them.

The utilization of deployment synergies across infrastructure networks of different industries has been identified as a key to improve the broadband business case. Thus, an increasing number of broadband plans require owners of physical infrastructures such as the electricity, pipeline, highway and railroad networks to host broadband infrastructure. However, cross-industry cooperation brings about new complexity to optimal utilization of deployment synergies.This paper explores cost savings that can be achieved if national non-telecommunication infrastructures are considered as source for broadband networks in rural areas. Moreover, it assesses economic, political and regulatory measures required for improving synergy utilization. The presented approach is based on a techno-economic broadband deployment model, which is applied to all rural communities in Germany. Results indicate that synergy optimized network topologies can generally decrease rural broadband deployment cost. However, it is required that local authorities recognize the definition of broadband tender areas as a chance for the aggregation of demand. Moreover, national regulators need to ensure that metro-aggregation, backbone and co-location costs, which are associated with non-telecommunication infrastructures, do not exceed the costs of the incumbent by more than 50%.