126 resultados para Stream Network
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The competitiveness of tourism destinations is a relevant issue for tourism studies, moreso, is a key element on the daily basis of tourism destinations. In this sense, the management of tourism destinations is essential to maintain competitive advantages. In this article tourism destination is considered as a relational network, where interaction and cooperation is needed among tourist agents, to achieve major levels of competitive advantage and a more effective destination management system. In addition, the perceptions of tourists are obtained from two main sources. The first one is the social construction of a tourism destination previous to the visit and the second one is obtained from the interaction between tourists and tourism destination agents during the visit. In this sense, the management of tourism destination to emit a homogenous and collective image is a factor that can reduce the gap if dissatisfaction from the previous and real tourist perception. The discussion is centered on the relationship within a destination, between the supply network and the targeted demand, considering these two approaches jointly, to benefit destination management. The main result is a conceptual model that shows how tourism agents and tourists in the tourism destination interact to improve the destination competitiveness
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Regulatory and funding asymmetries in the Spanish motorway network produce huge differences in the structure of gasoline markets by motorway type: free or toll. While competition is encouraged among gas stations on free motorways, the regulations for toll motorways allow private concessionaires to auction all gas stations to the same provider, thereby limiting competition and consolidating market power. This paper reports how this regulatory asymmetry results in higher prices and fewer gas stations. Specifically, we show that competition is constrained on toll motorways by the granting of geographical monopolies, resulting in a small number of rivals operating in close proximity to each other, and allowing gas stations to operate as local monopolies. The lack of competition would seem to account for the price differential between toll and free motorways. According to available evidence, deregulation measures affecting toll motorway concessions could help to mitigate price inefficiencies and increase consumer welfare.
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PPPS: Problem: Public-private-partnerships in transport infrastructure characteristically increase user-fees. Purpose: We aim to identify the network effects of the use of PPPs and increased user tolls in road infrastructure. Methods: We study the increases in user tolls on motorways due to the use of PPPs in the US. Results and conclusions: Among other things, the monetization of motorways is associated with an increase in toll levels that has consequences for their users, and also for the rest of the sections of the network.
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This paper analyzes Spanish infrastructure policy since the early 1700s: Road building in the eighteenth century, railway creation and expansion in the nineteenth, motorway expansion in the twentieth, and high speed rail development in the twenty-first. The analysis reveals a long-term pattern, in which infrastructure policy in Spain has been driven not by the requirements of commerce and economic activity, but rather by the desire to centralize transportation around the country’s political capital.
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Competition in airline markets may be tough. In this context, network carriers have two alternative strategies to compete with low-cost carriers. First, they may establish a low-cost subsidiary. Second, they may try to reduce costs using the main brand. This paper examines a successful strategy of the first type implemented by Iberia in the Spanish domestic market. Our analysis of data and the estimation of a pricing equation show that Iberia has been able to charge lower prices than rivals with its low-cost subsidiary. The pricing policy of the Spanish network carrier has been particularly aggressive in less dense routes and shorter routes.
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Although approximately 50% of Down Syndrome (DS) patients have heart abnormalities, they exhibit an overprotection against cardiac abnormalities related with the connective tissue, for example a lower risk of coronary artery disease. A recent study reported a case of a person affected by DS who carried mutations in FBN1, the gene causative for a connective tissue disorder called Marfan Syndrome (MFS). The fact that the person did not have any cardiac alterations suggested compensation effects due to DS. This observation is supported by a previous DS meta-analysis at the molecular level where we have found an overall upregulation of FBN1 (which is usually downregulated in MFS). Additionally, that result was cross-validated with independent expression data from DS heart tissue. The aim of this work is to elucidate the role of FBN1 in DS and to establish a molecular link to MFS and MFS-related syndromes using a computational approach. To reach that, we conducted different analytical approaches over two DS studies (our previous meta-analysis and independent expression data from DS heart tissue) and revealed expression alterations in the FBN1 interaction network, in FBN1 co-expressed genes and FBN1-related pathways. After merging the significant results from different datasets with a Bayesian approach, we prioritized 85 genes that were able to distinguish control from DS cases. We further found evidence for several of these genes (47%), such as FBN1, DCN, and COL1A2, being dysregulated in MFS and MFS-related diseases. Consequently, we further encourage the scientific community to take into account FBN1 and its related network for the study of DS cardiovascular characteristics.
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A minimum cost spanning tree (mcst) problem analyzes the way to efficiently connect individuals to a source when they are located at different places. Once the efficient tree is obtained, the question on how allocating the total cost among the involved agents defines, in a natural way, a confliicting claims situation. For instance, we may consider the endowment as the total cost of the network, whereas for each individual her claim is the maximum amount she will be allocated, that is, her connection cost to the source. Obviously, we have a confliicting claims problem, so we can apply claims rules in order to obtain an allocation of the total cost. Nevertheless, the allocation obtained by using claims rules might not satisfy some appealing properties (in particular, it does not belong to the core of the associated cooperative game). We will define other natural claims problems that appear if we analyze the maximum and minimum amount that an individual should pay in order to support the minimum cost tree. Keywords: Minimum cost spanning tree problem, Claims problem, Core JEL classification: C71, D63, D71.
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Nowadays, Wireless Sensor Networks (WSN) arealready a very important data source to obtain data about the environment. Thus, they are key to the creation of Cyber-Physical Systems (CPS). Given the popularity of P2P middlewares as ameans to efficiently process information and distribute services, being able to integrate them to WSN¿s is an interesting proposal. JXTA is a widely used P2P middleware that allows peers to easily exchange information, heavily relying on its main architectural highlight, the capability to organize peers with common interests into peer groups. However, right now, approaches to integrate WSNs to a JXTA network seldom take advantage of peer groups. For this reason, in this paper we present jxSensor, an integrationlayer for sensor motes which facilitates the deployment of CPS¿s under this architecture. This integration has been done taking into account JXTA¿s idiosyncrasies and proposing novel ideas,such as the Virtual Peer, a group of sensors that acts as a single entity within the peer group context.
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Freshwater species worldwide are experiencing dramatic declines partly attributable to ongoing climate change. It is expected that the future effects of climate change could be particularly severe in mediterranean climate (med-) regions, which host many endemic species already under great stress from the high level of human development. In this article, we review the climate and climate-induced changes in streams of med-regions and the responses of stream biota, focusing on both observed and anticipated ecological responses. We also discuss current knowledge gaps and conservation challenges. Expected climate alterations have already been observed in the last decades, and include: increased annual average air temperatures; decreased annual average precipitation; hydrologic alterations; and an increase in frequency, intensity and duration of extreme events, such as floods, droughts and fires. Recent observations, which are concordant with forecasts built, show stream biota of med-regions when facing climate changes tend to be displaced towards higher elevations and upper latitudes, communities tend to change their composition and homogenize, while some life-history traits seem to provide biota with resilience and resistance to adapt to the new conditions (as being short-lived, small, and resistant to low streamflow and desiccation). Nevertheless, such responses may be insufficient to cope with current and future environmental changes. Accurate forecasts of biotic changes and possible adaptations are difficult to obtain in med-regions mainly because of the difficulty of distinguishing disturbances due to natural variability from the effects of climate change, particularly regarding hydrology. Long-term studies are needed to disentangle such variability and improve knowledge regarding the ecological responses and the detection of early warning signals to climate change. Investments should focus on taxa beyond fish and macroinvertebrates, and in covering the less studied regions of Chile and South Africa. Scientists, policy makers and water managers must be involved in the climate change dialogue because the freshwater conservation concerns are huge.
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Contemporary public administrations have become increasingly more complex, having to cordinate actions with emerging actors in the public and the private spheres. In this scenario the modern ICTs have begun to be seen as an ideal vehicle to resolve some of the problems of public administration. We argue that there is a clear need to explore the extent to which public administrations are undergoing a process of transformation towards a netowork government linked to the systematic incorporation of ICTs in their basic activities. Through critically analysing a selection of e-government evaluation reports, we conclude that research should be carried out if we are to build a solid government assessment framework based on network-like organisation characteristics.
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The presence of e-portfolios in educational centres, companies and administrations has emergedstrongly during the last years by creating very different practices coming from different objectives and purposes. This situation has led researchers and practitioners to design and implement e-portfolios with little reference to previous knowledge of them; consequently, developments are disparate with many of the processes and dimensions used both in development and use being unnecessary complex. In order to minimize the inconveniences, unify these developmental processes and improve the resultsof implementation and use of e-portfolios, it seemed necessary to create a network of researchers, teachers and trainers coming from different universities and institutions of different kinds who are interested in the investigation and the practice of e-portfolios in Spain. Therefore, The Network on e-portfoliowas created in 2006, funded by the Spanish Ministry of Education and led by the UniversitatOberta de Catalunya. Besides the goals associatedwith the creation of this network and which wewanted to share with other European researchers and experts of other continents, we will also present in this paper some data concerned with the first study carried out on the use of e-portfolios in our country that shows where we are and which trends are the most important for the near future.
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Peer-reviewed
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Peer-reviewed
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Peer-reviewed
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Top predator loss is a major global problem, with a current trend in biodiversity loss towards high trophic levels that modifies most ecosystems worldwide. Most research in this area is focused on large-bodied predators, despite the high extinction risk of small-bodied freshwater fish that often act as apex consumers. Consequently, it remains unknown if intermittent streams are affected by the consequences of top-predators' extirpations. The aim of our research was to determine how this global problem affects intermittent streams and, in particular, if the loss of a small-bodied top predator (1) leads to a 'mesopredator release', affects primary consumers and changes whole community structures, and (2) triggers a cascade effect modifying the ecosystem function. To address these questions, we studied the topdown effects of a small endangered fish species, Barbus meridionalis (the Mediterranean barbel), conducting an enclosure/exclosure mesocosm experiment in an intermittent stream where B. meridionalis became locally extinct following a wildfire.We found that top predator absence led to 'mesopredator release', and also to 'prey release' despite intraguild predation, which contrasts with traditional food web theory. In addition, B. meridionalis extirpation changed whole macroinvertebrate community composition and increased total macroinvertebrate density. Regarding ecosystem function, periphyton primary production decreased in apex consumer absence. In this study, the apex consumer was functionally irreplaceable; its local extinction led to the loss of an important functional role that resulted in major changes to the ecosystem's structure and function. This study evidences that intermittent streams can be affected by the consequences of apex consumers' extinctions, and that the loss of small-bodied top predators can lead to large ecosystem changes. We recommend the reintroduction of small-bodied apex consumers to systems where they have been extirpated, to restore ecosystem structure and function.