Thirty Years of Turnstiles and Transport

To characterize transport in a deterministic dynamical system is to compute exit time distributions from regions or transition time distributions between regions in phase space. This paper surveys the considerable progress on this problem over the past thirty years. Primary measures of transport for volume-preserving maps include the exiting and incoming fluxes to a region. For area-preserving maps, transport is impeded by curves formed from invariant manifolds that form partial barriers, e.g., stable and unstable manifolds bounding a resonance zone or cantori, the remnants of destroyed invariant tori. When the map is exact volume preserving, a Lagrangian differential form can be used to reduce the computation of fluxes to finding a difference between the action of certain key orbits, such as homoclinic orbits to a saddle or to a cantorus. Given a partition of phase space into regions bounded by partial barriers, a Markov tree model of transport explains key observations, such as the algebraic decay of exit and recurrence distributions.Comment: Updated and corrected versio

What do patients really know? An evaluation of patients’ physical activity guideline knowledge within general practice

Background: Physical inactivity is well recognised as one of the leading causes of preventable death. However, little is known about the general public’s knowledge surrounding national physical activity guidelines, particularly within general practice (GP). Setting: Two GPs (York and Maidenhead, UK). Question: Are GP patients aware of the national physical guidelines? Also, are health care professionals routinely raising the issue of physical inactivity and would patients welcome support from health care professionals regarding inactivity? Methodology: A questionnaire was distributed in two GPs over a one-week period to evaluate patients knowledge of the national physical activity guidelines. Results: Ninety-four participants completed the questionnaire over one week (60 female; 34 male), with an average age of 54.2 (standard deviation: 19.9 years). 14% (95% Confidence Interval (CI): 8–22%) of the total participants correctly knew the recommended national guidelines for physical activity. 52% (95% CI: 42–63%) recalled being asked by a health care professional about their activity levels. 46% (95% CI: 35–56%) would welcome support from a health care professional around improving their activity levels. Discussion/Conclusion: Only 14% of responders correctly knew the current national minimum activity guidelines. Encouragingly 46% of participants in our study were interested in physical activity advice from a health care professional. Health care professionals need to be aware that many patients do not know the current physical activity guidelines and recognise that primary care may be an underutilised opportunity to educate and promote physical activity

What do patients really know? An evaluation of patients’ physical activity guideline knowledge within general practice

Background: Physical inactivity is well recognised as one of the leading causes of preventable death. However, little is known about the general public’s knowledge surrounding national physical activity guidelines, particularly within general practice (GP). Setting: Two GPs (York and Maidenhead, UK). Question: Are GP patients aware of the national physical guidelines? Also, are health care professionals routinely raising the issue of physical inactivity and would patients welcome support from health care professionals regarding inactivity? Methodology: A questionnaire was distributed in two GPs over a one-week period to evaluate patients knowledge of the national physical activity guidelines. Results: Ninety-four participants completed the questionnaire over one week (60 female; 34 male), with an average age of 54.2 (standard deviation: 19.9 years). 14% (95% Confidence Interval (CI): 8–22%) of the total participants correctly knew the recommended national guidelines for physical activity. 52% (95% CI: 42–63%) recalled being asked by a health care professional about their activity levels. 46% (95% CI: 35–56%) would welcome support from a health care professional around improving their activity levels. Discussion/Conclusion: Only 14% of responders correctly knew the current national minimum activity guidelines. Encouragingly 46% of participants in our study were interested in physical activity advice from a health care professional. Health care professionals need to be aware that many patients do not know the current physical activity guidelines and recognise that primary care may be an underutilised opportunity to educate and promote physical activity

A 2.75-Approximation Algorithm for the Unconstrained Traveling Tournament Problem

A 2.75-approximation algorithm is proposed for the unconstrained traveling tournament problem, which is a variant of the traveling tournament problem. For the unconstrained traveling tournament problem, this is the first proposal of an approximation algorithm with a constant approximation ratio. In addition, the proposed algorithm yields a solution that meets both the no-repeater and mirrored constraints. Computational experiments show that the algorithm generates solutions of good quality.Comment: 12 pages, 1 figur

Influence of melt feeding scheme and casting parameters during direct-chill casting on microstructure of an AA7050 billet

© The Minerals, Metals & Materials Society and ASM International 2012Direct-chill (DC) casting billets of an AA7050 alloy produced with different melt feeding schemes and casting speeds were examined in order to reveal the effect of these factors on the evolution of microstructure. Experimental results show that grain size is strongly influenced by the casting speed. In addition, the distribution of grain sizes across the billet diameter is mostly determined by melt feeding scheme. Grains tend to coarsen towards the center of a billet cast with the semi-horizontal melt feeding, while upon vertical melt feeding the minimum grain size was observed in the center of the billet. Computer simulations were preformed to reveal sump profiles and flow patterns during casting under different melt feeding schemes and casting speeds. The results show that solidification front and velocity distribution of the melt in the liquid and slurry zones are very different under different melt feeding scheme. The final grain structure and the grain size distribution in a DC casting billet is a result of a combination of fragmentation effects in the slurry zone and the cooling rate in the solidification range

A comprehensive model for familial breast cancer incorporating BRCA1, BRCA2 and other genes

In computing the probability that a woman is a BRCA1 or BRCA2 carrier for genetic counselling purposes, it is important to allow for the fact that other breast cancer susceptibility genes may exist. We used data from both a population based series of breast cancer cases and high risk families in the UK, with information on BRCA1 and BRCA2 mutation status, to investigate the genetic models that can best explain familial breast cancer outside BRCA1 and BRCA2 families. We also evaluated the evidence for risk modifiers in BRCA1 and BRCA2 carriers. We estimated the simultaneous effects of BRCA1, BRCA2, a third hypothetical gene ‘BRCA3’, and a polygenic effect using segregation analysis. The hypergeometric polygenic model was used to approximate polygenic inheritance and the effect of risk modifiers. BRCA1 and BRCA2 could not explain all the observed familial clustering. The best fitting model for the residual familial breast cancer was the polygenic, although a model with a single recessive allele produced a similar fit. There was also significant evidence for a modifying effect of other genes on the risks of breast cancer in BRCA1 and BRCA2 mutation carriers. Under this model, the frequency of BRCA1 was estimated to be 0.051% (95% CI: 0.021–0.125%) and of BRCA2 0.068% (95% CI: 0.033–0.141%). The breast cancer risk by age 70 years, based on the average incidence over all modifiers was estimated to be 35.3% for BRCA1 and 50.3% for BRCA2. The corresponding ovarian cancer risks were 25.9% for BRCA1 and 9.1% for BRCA2. The findings suggest that several common, low penetrance genes with multiplicative effects on risk may account for the residual non-BRCA1/2 familial aggregation of breast cancer. The modifying effect may explain the previously reported differences between population based estimates for BRCA1/2 penetrance and estimates based on high-risk families

Determination of Survivable Fires

At NASA, there exists no standardized design or testing protocol for spacecraft fire suppression systems (either handheld or total flooding designs). An extinguisher's efficacy in safely suppressing any reasonable or conceivable fire is the primary benchmark. That concept, however, leads to the question of what a reasonable or conceivable fire is. While there exists the temptation to over-size' the fire extinguisher, weight and volume considerations on spacecraft will always (justifiably) push for the minimum size extinguisher required. This paper attempts to address the question of extinguisher size by examining how large a fire a crew member could successfully survive and extinguish in the confines of a spacecraft. The hazards to the crew and equipment during an accidental fire include excessive pressure rise resulting in a catastrophic rupture of the vehicle skin, excessive temperatures that burn or incapacitate the crew (due to hyperthermia), carbon dioxide build-up or other accumulation of other combustion products (e.g. carbon monoxide). Estimates of these quantities are determined as a function of fire size and mass of material burned. This then becomes the basis for determining the maximum size of a target fire for future fire extinguisher testing

'Word from the street' : when non-electoral representative claims meet electoral representation in the United Kingdom

Taking the specific case of street protests in the UK – the ‘word from the street’– this article examines recent (re)conceptualizations of political representation, most particularly Saward’s notion of ‘representative claim’. The specific example of nonelectoral claims articulated by protestors and demonstrators in the UK is used to illustrate: the processes of making, constituting, evaluating and accepting claims for and by constituencies and audiences; and the continuing distinctiveness of claims based upon electoral representation. Two basic questions structure the analysis: first, why would the political representative claims of elected representatives trump the nonelectoral claims of mass demonstrators and, second, in what ways does the ‘perceived legitimacy’ of the former differ from the latter