Origin of structural difference in metabolic networks with respect to temperature

<p>Abstract</p> <p>Background</p> <p>Metabolism is believed to adaptively shape-shift with changing environment. In recent years, a structural difference with respect to temperature, which is an environmental factor, has been revealed in metabolic networks, implying that metabolic networks transit with temperature. Subsequently, elucidatation of the origin of these structural differences due to temperature is important for understanding the evolution of life. However, the origin has yet to be clarified due to the complexity of metabolic networks.</p> <p>Results</p> <p>Consequently, we propose a simple model with a few parameters to explain the transitions. We first present mathematical solutions of this model using mean-field approximation, and demonstrate that this model can reproduce structural properties, such as heterogeneous connectivity and hierarchical modularity, in real metabolic networks both qualitatively and quantitatively. We next show that the model parameters correlate with optimal growth temperature. In addition, we present a relationship between multiple cyclic properties and optimal growth temperature in metabolic networks.</p> <p>Conclusion</p> <p>From the proposed model, we find that such structural properties are determined by the emergence of a short-cut path, which reduces the minimum distance between two nodes on a graph. Furthermore, we investigate correlations between model parameters and growth temperature; as a result, we find that the emergence of the short-cut path tends to be inhibited with increasing temperature. In addition, we also find that the short-cut path bypasses a relatively long path at high temperature when the emergence of the new path is not inhibited. Even further, additional network analysis provides convincing evidence of the reliability of the proposed model and its conclusions on the possible origins of differences in metabolic network structure.</p

Internationally recruited nurses from India and the Philippines in the United Kingdom: the decision to emigrate.

BACKGROUND: The United Kingdom has recruited nurses from countries with a reported surplus in their nursing workforce, such as India and the Philippines. However, little is known about the decision to emigrate made by nurses from these countries. One theory suggests that individuals weigh the benefits and costs of migration: the push and pull factors. This paper challenges the restricted economic focus of this predominant theory and compares the diverse motivations of nurses from different countries as well as those of nurses with previous migratory experience and first-time migrants. METHODS: This research was undertaken in a National Health Service acute trust in London by means of a qualitative interpretative approach. Data were collected through face-to-face longitudinal and cross-sectional interviews with internationally recruited nurses from India (n=6) and the Philippines (n=15); and analysis of their narratives was used to generate data about their expectations and experiences. Data were analysed by means of a framework approach that allowed for intra-case and cross-case analysis. RESULTS: From an individual perspective, nurses in this study reported economic reasons as the main trigger for migration in the first instance. Yet this doesn't entirely explain the decision to move from previous migratory destinations (e.g. Saudi Arabia) where economic needs are already fulfilled. In these cases migration is influenced by professional and social aspirations that highlight the influence of the cultural environment--specifically some religious and gender-related issues. Family support and support from migratory networks in the country of origin and destination were also important elements conducive to and supportive of migration. Nurses from India report coming to the United Kingdom to stay, while Filipina nurses come as temporary migrants sending remittances to support their families in the Philippines. CONCLUSION: This study shows the diverse motivations of nurses from different countries and with different migratory backgrounds and provides evidence that factors other than economic factors influence nurses' decision to emigrate. This information can help developing countries increase retention of this essential and often scarce resource and can also help the United Kingdom's National Health Service to improve the experience of internationally recruited nurses and therefore increase their retention in the United Kingdom