Dynamic arrest in polymer melts: competition between packing and intramolecular barriers

We present molecular dynamics simulations of a simple model for polymer melts with intramolecular barriers. We investigate structural relaxation as a function of the barrier strength. Dynamic correlators can be consistently analyzed within the framework of the mode coupling theory of the glass transition. Control parameters are tuned in order to induce a competition between general packing effects and polymer-specific intramolecular barriers as mechanisms for dynamic arrest. This competition yields unusually large values of the so-called mode coupling theory exponent parameter and rationalizes qualitatively different observations for simple bead-spring and realistic polymers. The systematic study of the effect of intramolecular barriers presented here also establishes a fundamental difference between the nature of the glass transition in polymers and in simple glass formers.

Shifted loops and coercivity from field imprinted high energy barriers in ferritin and ferrihydrite nanoparticles

We show that the coercive field in ferritin and ferrihydrite depends on the maximum magnetic field in a hysteresis loop and that coercivity and loop shifts depend both on the maximum and cooling fields. In the case of ferritin, we show that the time dependence of the magnetization also depends on the maximum and previous cooling fields. This behavior is associated to changes in the intraparticle energy barriers imprinted by these fields. Accordingly, the dependence of the coercive and loop-shift fields with the maximum field in ferritin and ferrihydrite can be described within the frame of a uniform-rotation model considering a dependence of the energy barrier with the maximum and the cooling fields.

When supply travels far beyond demand: Institutional and regulatory causes of oversupply in Spain’s transport infrastructure

Spain’s transport infrastructure policy has become a paradigmatic case of oversupply and of mismatch with demand. The massive expansion of the country’s transport infrastructure over the last decade has not been a response to demand bottlenecks or previously identified needs. For this reason, the intensity of use today on all interurban modes of transport in Spain falls well below that of other EU countries. This paper analyzes the institutional and regulatory factors that have permitted this policy, allowing us to draw lessons from the Spanish case that should help other countries avoid the pitfalls and shortcomings of Spanish policy. Based on our analysis, we also discuss policy remedies and suggest reforms in different regulatory areas, which could help improve the performance of Spain’s infrastructure policy.

The Institutional, Economic and Social Determinants of Local Government Transparency

Interest in public accountability and government transparency is increasing worldwide. The literature on the determinants of transparency is evolving but is still in its early stages. So far, it has typically focused on national or regional governments while neglecting the local government level. This paper builds on the scarce knowledge available in order to examine the economic, social, and institutional determinants of local government transparency in Spain. We draw on a 2010 survey and the transparency indexes constructed by the NGO Transparency International (Spain) in order to move beyond the fiscal transparency addressed in previous work. In so doing, we broaden the analysis of transparency to the corporate, social, fiscal, contracting, and planning activities of governments. Our results on overall transparency indicate that large municipalities and left-wing local government leaders are associated with better transparency indexes; while the worst results are presented by provincial capitals, cities where tourist activity is particularly important and local governments that enjoy an absolute majority. The analysis of other transparency categories generally shows the consistent impact of these determinants and the need to consider a wider set of variables to capture their effect.

Perceived Barriers to Physical Activity and Related Factors in Spanish University Students

Objective: The purpose of this study was to identify the influence of readiness of change for physical activity (PA), sociodemographic factors, lifestyle and physical activity status (PAS) on perceived barriers among Spanish university students. Participants: Seven hundred and seventy two (n = 772) men and women ages 17 - 39 at a north-west regional university in Spain participated in the study. Methods: The International Physical Activity Questionnaire, the States of Change for Physical Activity Behaviour Questionnaire and the Self-perceived Barriers for Physical Activity Questionnaire were used. Description, correlation and multiple regression analyses were completed. Results: Participants self-perceived low average-score barriers (2.6 ± 1.4 over 10.0). The 3-higher scores barriers corresponded to “too much work”; “lack of time for exercise” and “laziness”. Gender, PAS and self-perceived health were shown to be associated with perceived barriers. Conclusions: University institutions should consider those factors that predict barriers to PA to develop effective intervention programs.

Barriers and Motivators for Using Open Educational Resources in Schools

In an explorative study, we investigated on German schoolteachers how they use, reuse, produce and manage Open Educational Resources. The main questions in this research have been, what their motivators and barriers are in their use of Open Educational Resources, what others can learn from their Open Educational Practices, and what we can do to raise the dissemination level of OER in schools.

Identifying pedagogical, technological and organizational barriers in virtual learning environments

Virtual learning environments are online spaces where learners interact with other learners, teachers, resources and the environment in itself. Although technology is meant to enhance the learning process, there are important issues regarding pedagogical and organizational aspects that must be addressed. In this paper we review the barriers detected in a virtual university which exclusively uses Internet as the main channel of communication, with no face-to-face requirements exceptthose related to final evaluation.

A missing spatial link in institutional quality

History tells that institutions evolve gradually over time, pushing new ideas across borders and cultures. Globalisation is argued to accelerate this process. We examine the spatial links of different political institutions across borders. Applying various tests for spatial proximity, we do not find evidence of contemporaneous spatial links. This result is robust to various measures of distance and of cultural proximity across countries. Instead, when we analyse long run dynamics diffusion of institutions seems to occur only gradually.

Institutional Determinants of Military Spending

Drawing on a database for 1988-2006 containing information on 157 countries, we investigate the effects on military spending of government form, electoral rules, concentration of parliamentary parties, and ideology. From an OLS regression on pooled data, our results show that presidential democracies spend more than parliamentary systems on defense, whereas the presence of a plurality voting system will reduce the defense burden. Our findings suggest that, in contrast to theoretical predictions in the literature, institutions do not have the same impact on the provision of all public goods. We present as well evidence regarding the effect of ideology on defense spending.

Intraregional trade in South America, 1913-50. Economic linkages before institutional agreements

Dejando de lado NAFTA, la integración comercial en América Latina sigue siendo muy moderada hoy en día, representando alrededor del 20% del comercio total. Lo sorprendente es que estos valores eran más altos en 1945. Esto constituye un hecho paradoxal: la integración comercial alcanzó su récord antes de la firma de acuerdos de integración comercial. En el presente trabajo se estudia el comercio intrarregional a lo largo del período de entreguerras (1913-1950) a través del análisis de cinco casos: Argentina, Bolivia, Brasil, Chile y Peru. El análisis de la integración comercial en este período representa una novedad en la literatura, ya que los trabajos sobre América Latina, específicos de comercio intraregional, se centran en el período a partir de la década de 1960. El documento destaca dos conclusiones principales: a) con la excepción de los períodos de las guerras mundiales, el comercio intraregional ha sido muy modesto desde 1913 hasta la actualidad, b) en general, el comercio intrarregional repitió la especialización del comercio mundial: una alta concentración en productos de bajo valor añadido.

Intraregional trade in South America, 1913-50. Economic linkages before institutional agreements

Dejando de lado NAFTA, la integración comercial en América Latina sigue siendo muy moderada hoy en día, representando alrededor del 20% del comercio total. Lo sorprendente es que estos valores eran más altos en 1945. Esto constituye un hecho paradoxal: la integración comercial alcanzó su récord antes de la firma de acuerdos de integración comercial. En el presente trabajo se estudia el comercio intrarregional a lo largo del período de entreguerras (1913-1950) a través del análisis de cinco casos: Argentina, Bolivia, Brasil, Chile y Peru. El análisis de la integración comercial en este período representa una novedad en la literatura, ya que los trabajos sobre América Latina, específicos de comercio intraregional, se centran en el período a partir de la década de 1960. El documento destaca dos conclusiones principales: a) con la excepción de los períodos de las guerras mundiales, el comercio intraregional ha sido muy modesto desde 1913 hasta la actualidad, b) en general, el comercio intrarregional repitió la especialización del comercio mundial: una alta concentración en productos de bajo valor añadido.

The evolution of post-zygotic isolation barriers by immune-triggered hybrid incompatibilities in Arabidopsis thaliana

A long-standing question in evolutionary biology is what defines a species. The biological species concept considers a species as a population of individuals that interbreeds freely and produces viable offspring. Therefore, reproductive isolation is the essence of species. Hybrid necrosis is one form of post-zygotic reproductive isolation. In this chapter, we summarize what is known to date about this phenomenon and highlight progress made in the understanding of these immune-triggered hybrid incompatibilities through our research in the plant model Arabidopsis thaliana.

The evolution of post-zygotic isolation barriers by immune-triggered hybrid incompatibilities in Arabidopsis thaliana

A long-standing question in evolutionary biology is what defines a species. The biological species concept considers a species as a population of individuals that interbreeds freely and produces viable offspring. Therefore, reproductive isolation is the essence of species. Hybrid necrosis is one form of post-zygotic reproductive isolation. In this chapter, we summarize what is known to date about this phenomenon and highlight progress made in the understanding of these immune-triggered hybrid incompatibilities through our research in the plant model Arabidopsis thaliana.

The institutional vs. the academic definition of the quality of work life. What is the focus of the European Commission?

In recent years, we have seen how the quality of work life has been focused and defined by the European Commission (EC). In our study we compare the EC definition with the academic one and try to see how close they are. We also analyse the possibility of applying the institutional definition to the Spanish case through the development of specific indicators. Our main conclusions are that QWL is increasingly important for policy makers. In addition, it is essential to have objective indicators and to conduct surveys in order to reliably measure QWL.

Effects of institutional environment and technology development on payment choice

The purpose of this paper is to analyze the combination of institutional factors and technology advances as determinants of payment systems choice. The theoretical set up suggests that countries entering into a new institutional environment approach accepting group attitudes towards payment choices as a consequence of institutional pressure and technology development. We apply the results of the model to 2004 European Union enlargement process. Results confirm the relevance of both institutional environment and technology development in retail payment system decisions of newly acceded countries.