Collective traffic-like movement of ants on a trail: dynamical phases and phase transitions

The traffic-like collective movement of ants on a trail can be described by a stochastic cellular automaton model. We have earlier investigated its unusual flow-density relation by using various mean field approximations and computer simulations. In this paper, we study the model following an alternative approach based on the analogy with the zero range process, which is one of the few known exactly solvable stochastic dynamical models. We show that our theory can quantitatively account for the unusual non-monotonic dependence of the average speed of the ants on their density for finite lattices with periodic boundary conditions. Moreover, we argue that the model exhibits a continuous phase transition at the critial density only in a limiting case. Furthermore, we investigate the phase diagram of the model by replacing the periodic boundary conditions by open boundary conditions.Comment: 8 pages, 6 figure

Natriuretic peptide receptors regulate cytoprotective effects in a human ex vivo 3D/bioreactor model

© 2013 Peake et al.; licensee BioMed Central Ltd. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited

Generational differences in factors influencing physicians to choose a work location.

INTRODUCTION: Canadian medical schools have increased enrolment and recruited more rural students in an effort to address general and rural physician shortages. The success of this approach depends on the recruitment of these newly trained physicians to under-serviced areas. Studies from North America suggest that the career expectations and practice patterns of younger, more recently graduated physicians differ from those of their older counterparts. This study explored the factors that influenced the work location choices of physicians of differing generations, who trained at universities in Saskatchewan, and Newfoundland and Labrador, two Canadian provinces with large rural populations and no community larger than 235 000 population. METHODS: Semi-structured, qualitative interviews were conducted with physicians who graduated from either the Memorial University of Newfoundland or the University of Saskatchewan. Generation definitions were based on the graduation year. Early-career physicians graduated between 1995 and 1999; mid-career physician graduated between 1985 and 1989; late-career physicians graduated between 1975 and 1979; and end-career physicians graduated between 1965 and 1969. Each physician was asked questions about the number and nature of work location changes over the course of their careers and the factors related to their decision to choose each location. Interview transcripts and notes were analyzed using a thematic analysis approach. Although the study focus was on generational differences, similarities and differences between universities, sexes and specialties (family physicians/GPs vs specialists) were also examined. Recruitment to the provinces was focused on as a whole, because the largest communities in the provinces are small compared with most urban communities. RESULTS: Forty-eight physicians were interviewed, five to nine physicians who graduated in each decade and from each university. The desire to be near family and friends was cited as the primary consideration when choosing a work location, regardless of generation. Likewise, residency training location, the ability to use their skills and knowledge fully, and the quality of recruitment efforts were important considerations in choosing a work location for all physicians. For some, remuneration was very influential in their work location decision; however, many physicians who chose to remain in their smaller 'home' provinces noted the lower cost of living in these provinces. Physicians who graduated in the 1980s and 1990s placed greater emphasis on work-life balance and spouse's employment opportunities than their older generation counterparts. In contrast, physicians who graduated in the 1960s and 1070s highlighted the medical need of the community, and the desire for adventure and to see new places as important. CONCLUSIONS: While many factors for choosing a work location appear to be stable over generations, a number of generational differences were found. Younger physicians placed greater emphasis on work-life balance and spouse's employment than older generation physicians. These differences may have important implications for small population regions which may not be able to support physician-spouse pairs or certain subspecialties. Although economic factors have largely been the focus of recruitment and retention initiatives in these provinces, the findings highlight the importance of addressing the needs and expectations of younger generation physicians in order to attract these physicians