5,645 research outputs found
Two-dimensional colloidal fluids exhibiting pattern formation
Fluids with competing short range attraction and long range repulsive
interactions between the particles can exhibit a variety of microphase
separated structures. We develop a lattice-gas (generalised Ising) model and
analyse the phase diagram using Monte Carlo computer simulations and also with
density functional theory (DFT). The DFT predictions for the structures formed
are in good agreement with the results from the simulations, which occur in the
portion of the phase diagram where the theory predicts the uniform fluid to be
linearly unstable. However, the mean-field DFT does not correctly describe the
transitions between the different morphologies, which the simulations show to
be analogous to micelle formation. We determine how the heat capacity varies as
the model parameters are changed. There are peaks in the heat capacity at state
points where the morphology changes occur. We also map the lattice model onto a
continuum DFT that facilitates a simplification of the stability analysis of
the uniform fluid.Comment: 13 pages, 15 figure
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>
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>
Aspirated capacitor measurements of air conductivity and ion mobility spectra
Measurements of ions in atmospheric air are used to investigate atmospheric
electricity and particulate pollution. Commonly studied ion parameters are (1)
air conductivity, related to the total ion number concentration, and (2) the
ion mobility spectrum, which varies with atmospheric composition. The physical
principles of air ion instrumentation are long-established. A recent
development is the computerised aspirated capacitor, which measures ions from
(a) the current of charged particles at a sensing electrode, and (b) the rate
of charge exchange with an electrode at a known initial potential, relaxing to
a lower potential. As the voltage decays, only ions of higher and higher
mobility are collected by the central electrode and contribute to the further
decay of the voltage. This enables extension of the classical theory to
calculate ion mobility spectra by inverting voltage decay time series. In
indoor air, ion mobility spectra determined from both the novel voltage decay
inversion, and an established voltage switching technique, were compared and
shown to be of similar shape. Air conductivities calculated by integration
were: 5.3 +- 2.5 fS/m and 2.7 +- 1.1 fS/m respectively, with conductivity
determined to be 3 fS/m by direct measurement at a constant voltage.
Applications of the new Relaxation Potential Inversion Method (RPIM) include
air ion mobility spectrum retrieval from historical data, and computation of
ion mobility spectra in planetary atmospheres.Comment: To be published in Review of Scientific Instrument
Time trends in survival and readmission following coronary artery bypass grafting in Scotland, 1981-96: retrospective observational study
Improvements in coronary revascularisation techniques and an increase in the use of percutaneous interventions1 have led to a rise in the number of coronary artery bypass grafting operations in older patients with more severe cardiac disease and worse comorbidity and who have previously undergone revascularisation procedures. 2 3 Advances in surgical and anaesthetic techniques have prevented a worsening risk profile from being translated into an increase in perioperative deaths. 2 3 The aim of our study was to examine time trends in major outcomes up to two years after coronary artery bypass grafting
Can Modal Skepticism Defeat Humean Skepticism?
My topic is moderate modal skepticism in the spirit of Peter van Inwagen. Here understood, this is a conservative version of modal empiricism that severely limits the extent to which an ordinary agent can reasonably believe âexoticâ possibility claims. I offer a novel argument in support of this brand of skepticism: modal skepticism grounds an attractive (and novel) reply to Humean skepticism. Thus, I propose that modal skepticism be accepted on the basis of its theoretical utility as a tool for dissolving philosophical paradox
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