1,839 research outputs found
Public goods and decay in networks
We propose a simple behavioral model to analyze situations where (1) a group of agents repeatedly plays a public goods game within a network structure and (2) each agent only observes the past behavior of her neighbors, but is affected by the decisions of the whole group. The model assumes that agents are imperfect conditional cooperators, that they infer unobserved contributions assuming imperfect conditional cooperation by others, and that they have some degree of bounded rationality. We show that our model approximates quite accurately regularities derived from public goods game experiments
The vulnerability of public spaces: challenges for UK hospitals under the 'new' terrorist threat
This article considers the challenges for hospitals in the United Kingdom that arise from the threats of mass-casualty terrorism. Whilst much has been written about the role of health care as a rescuer in terrorist attacks and other mass-casualty crises, little has been written about health care as a victim within a mass-emergency setting. Yet, health care is a key component of any nation's contingency planning and an erosion of its capabilities would have a significant impact on the generation of a wider crisis following a mass-casualty event. This article seeks to highlight the nature of the challenges facing elements of UK health care, with a focus on hospitals both as essential contingency responders under the United Kingdom's civil contingencies legislation and as potential victims of terrorism. It seeks to explore the potential gaps that exist between the task demands facing hospitals and the vulnerabilities that exist within them
Is the Scottish population living dangerously? Prevalence of multiple risk factors: the Scottish Health Survey 2003
<b>Background:</b>
Risk factors are often considered individually, we aimed to investigate the prevalence of combinations of multiple behavioural risk factors and their association with socioeconomic determinants.<p></p>
<b>Methods:</b>
Multinomial logistic regression was used to model the associations between socioeconomic factors and multiple risk factors from data in the Scottish Health Survey 2003. Prevalence of five main behavioural risk factors - smoking alcohol, diet, overweight/obesity, and physical inactivity, and the odds in relation to demographic, individual and area socioeconomic factors.<p></p>
<b>Results:</b>
Full data were available on 6,574 subjects (80.7% of the survey sample). Nearly the whole adult population (97.5%) reported to have at least one behavioural risk factor; while 55% have three or more risk factors; and nearly 20% have four or all five risk factors. The most important determinants for having four or five multiple risk factors were low educational attainment which conferred around a 3-fold increased odds compared to high education; and residence in the most deprived communities (relative to least deprived) which had greater than 3-fold increased odds.<p></p>
<b>Conclusions:</b>
The prevalence of multiple behavioural risk factors was high and the prevalence of absence of all risk factors very low. These behavioural patterns were socioeconomically determined. Policy to address factors needs to be joined up and better consider underlying socioeconomic circumstances.<p></p>
On the coexistence of cooperators, defectors and conditional cooperators in the multiplayer iterated Prisoner's Dilemma
Recent experimental evidence [Gruji\'c et al., PLoS ONE 5, e13749 (2010)] on
the spatial Prisoner's Dilemma suggests that players choosing to cooperate or
not on the basis of their previous action and the actions of their neighbors
coexist with steady defectors and cooperators. We here study the coexistence of
these three strategies in the multiplayer iterated Prisoner's Dilemma by means
of the replicator dynamics. We consider groups with n = 2, 3, 4 and 5 players
and compute the payoffs to every type of player as the limit of a Markov chain
where the transition probabilities between actions are found from the
corresponding strategies. We show that for group sizes up to n = 4 there exists
an interior point in which the three strategies coexist, the corresponding
basin of attraction decreasing with increasing number of players, whereas we
have not been able to locate such a point for n = 5. We analytically show that
in the infinite n limit no interior points can arise. We conclude by discussing
the implications of this theoretical approach on the behavior observed in
experiments.Comment: 12 pages, 10 figures, uses elsart.cl
Cardiovascular disease and air pollution in Scotland: no association or insufficient data and study design?
<p><b>Background:</b>
Coronary heart disease and stroke are leading causes of mortality and ill health in Scotland, and clear associations have been found in previous studies between air pollution and cardiovascular disease. This study aimed to use routinely available data to examine whether there is any evidence of an association between short-term exposure to particulate matter (measured as PM10, particles less than 10 micrograms per cubic metre) and hospital admissions due to cardiovascular disease, in the two largest cities in Scotland during the years 2000 to 2006.</p>
<p><b>Methods:</b> The study utilised an ecological time series design, and the analysis was based on overdispersed Poisson log-linear models.</p>
<p><b>Results:</b> No consistent associations were found between PM10 concentrations and cardiovascular hospital admissions in either of the cities studied, as all of the estimated relative risks were close to one, and all but one of the associated 95% confidence intervals contained the null risk of one.</p>
<p><b>Conclusions:</b> This study suggests that in small cities, where air quality is relatively good, then either PM10 concentrations have no effect on cardiovascular ill health, or that the routinely available data and the corresponding study design are not sufficient to detect an association.</p>
Gradient Representations and Affine Structures in AE(n)
We study the indefinite Kac-Moody algebras AE(n), arising in the reduction of
Einstein's theory from (n+1) space-time dimensions to one (time) dimension, and
their distinguished maximal regular subalgebras sl(n) and affine A_{n-2}^{(1)}.
The interplay between these two subalgebras is used, for n=3, to determine the
commutation relations of the `gradient generators' within AE(3). The low level
truncation of the geodesic sigma-model over the coset space AE(n)/K(AE(n)) is
shown to map to a suitably truncated version of the SL(n)/SO(n) non-linear
sigma-model resulting from the reduction Einstein's equations in (n+1)
dimensions to (1+1) dimensions. A further truncation to diagonal solutions can
be exploited to define a one-to-one correspondence between such solutions, and
null geodesic trajectories on the infinite-dimensional coset space H/K(H),
where H is the (extended) Heisenberg group, and K(H) its maximal compact
subgroup. We clarify the relation between H and the corresponding subgroup of
the Geroch group.Comment: 43 page
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