846 research outputs found

    Sensitivity of wardrop equilibria

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    We study the sensitivity of equilibria in the well-known game theoretic traffic model due to Wardrop. We mostly consider single-commodity networks. Suppose, given a unit demand flow at Wardrop equilibrium, one increases the demand by ε or removes an edge carrying only an ε-fraction of flow. We study how the equilibrium responds to such an ε-change. Our first surprising finding is that, even for linear latency functions, for every ε> 0, there are networks in which an ε-change causes every agent to change its path in order to recover equilibrium. Nevertheless, we can prove that, for general latency functions, the flow increase or decrease on every edge is at most ε. Examining the latency at equilibrium, we concentrate on polynomial latency functions of degree at most p with nonnegative coefficients. We show that, even though the relative increase in the latency of an edge due to an ε-change in the demand can be unbounded, the path latency at equilibrium increases at most by a factor of (1 + ε) p . The increase of the price of anarchy is shown to be upper bounded by the same factor. Both bounds are shown to be tight. Let us remark that all our bounds are tight. For the multi-commodity case, we present examples showing that neither the change in edge flows nor the change in the path latency can be bounded

    Simple elbow dislocations: a systematic review of the literature

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    Objective: To identify if functional treatment is the best available treatment for simple elbow dislocations. Search strategy: Electronic databases MEDLINE, EMBASE, LILACS, and the Cochrane Central Register of Controlled Trials. Selection criteria: Studies were eligible for inclusion if they were trials comparing different techniques for the treatment of simple elbow dislocations. Data analysis: Results were expressed as relative risk for dichotomous outcomes and weighted mean difference for continuous outcomes with 95% confidence intervals. Main results: This review has included data from two trials and three observational comparative studies. Important data were missing from three observational comparative studies and the results from these studies were extracted for this review. No difference was found between surgical treatment of the collateral ligaments and plaster immobilisation of the elbow joint. Better range of movement, less pain, better functional scores, shorter disability and shorter treatment time were seen after functional treatment versus plaster immobilisation

    Teacher Awareness and Attitudes Regarding Adolescent Risk Behaviours : a Sample of Finnish Middle and High School Teachers

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    Empirical evidence has shown that youth gamble on both regulated and unregulated games, despite legislative prohibitions. This study assesses middle and high school teachers' awareness and attitudes regarding adolescent gambling and other potentially high-risk behaviours in Finland. A convenience sample of teachers (N = 157) from 13 provinces participated in the survey. The results suggest that teachers in Finland were more knowledgeable of the age limits of other adolescent high-risk behaviours than the legal age for gambling. Teachers were somewhat familiar with the behaviours and consequences associated with adolescent gambling. All other risk behaviours were perceived as being more important than gambling. Teachers' awareness about gambling prevention material in Finnish schools was limited. Results suggest that initiatives are required to enhance teachers' knowledge of adolescent problem gambling and its harmful short- and long-term consequences. School policies and guidelines including gambling behavior should be implemented in middle and high schools globally.Peer reviewe

    On the Price of Anarchy of Highly Congested Nonatomic Network Games

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    We consider nonatomic network games with one source and one destination. We examine the asymptotic behavior of the price of anarchy as the inflow increases. In accordance with some empirical observations, we show that, under suitable conditions, the price of anarchy is asymptotic to one. We show with some counterexamples that this is not always the case. The counterexamples occur in very simple parallel graphs.Comment: 26 pages, 6 figure

    A model for studying the hemostatic consumption or destruction of platelets

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    A fundamental issue in understanding homeostasis of the hematopoietic system is to what extent intrinsic and extrinsic factors regulate cell fate. We recently revisited this issue for the case of blood platelets and concluded that platelet life span is largely regulated by internal factors, in contrast to the long-held view that accumulated damage from the environment triggers clearance. However, it is known that in humans there is an ongoing fixed requirement for platelets to maintain hemostasis and prevent bleeding; hence a proportion of platelets may be consumed in such processes before the end of their natural life span. Whether it is possible to detect this random loss of platelets in normal individuals at steady-state is unknown. To address this question, we have developed a mathematical model that independently incorporates age-independent random loss and age-dependent natural senescent clearance. By fitting to population survival curves, we illustrate the application of the model in quantifying the fixed requirement for platelets to maintain hemostasis in mice, and discuss the relationship with previous work in humans. Our results suggest a higher requirement for platelets in mice than in humans, however experimental uncertainty in the data limits our ability to constrain this quantity. We then explored the relationship between experimental uncertainty and parameter constraint using simulated data. We conclude that in order to provide useful constraint on the random loss fraction the standard error in the mean of the data must be reduced substantially, either through improving experimental uncertainty or increasing the number of experimental replicates to impractical levels. Finally we find that parameter constraint is improved at higher values of the random loss fraction; thus the model find utility in situations where the random loss fraction is expected to be high, for example during active bleeding or some types of thrombocytopenia.Mark R. Dowling, Emma C. Josefsson, Katya J. Henley, Benjamin T. Kile, Philip D. Hodgki

    Citizen Science and Open Data: a model for Invasive Alien Species in Europe

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    Invasive Alien Species (IAS) are a growing threat to Europe's biodiversity. The implementation of European Union Regulation on IAS can benefit from the involvement of the public in IAS recording and management through Citizen Science (CS) initiatives. Aiming to tackle issues related with the use of CS projects on IAS topics, a dedicated workshop titled “Citizen Science and Open Data: a model for Invasive Alien Species in Europe” was organized by the Joint Research Centre (JRC) and the European Cooperation in Science and Technology (COST Association). Fifty key stakeholders from all Europe, including two Members of the European Parliament, attended the workshop. With a clear focus on IAS, the workshop aimed at addressing the following issues: a) CS and policy, b) citizen engagement, and c) CS data management. Nine short presentations provided input on CS and IAS issues. Participants discussed specific topics in several round tables (“world café” style) and reported back their conclusions to the audience and full assembly moderated discussions. Overall, the workshop enabled the sharing of ideas, approaches and best practices regarding CS and IAS. Specific opportunities and pitfalls of using CS data in the whole policy cycle for IAS were recognized. Concerning the implementation of the IAS Regulation, CS data could complement official surveillance systems, and contribute to the early warning of the IAS of Union concern after appropriate validation by the Member States’ competent authorities. CS projects can additionally increase awareness and empower citizens. Attendees pointed out the importance for further public engagement in CS projects on IAS that demonstrate specific initiatives and approaches and analyze lessons learned from past experiences. In addition, the workshop noted that the data gathered from different CS projects on IAS are fragmented. It highlighted the need for using an open and accessible platform to upload data originating from CS sources or to mirror validated data into a single, easy-to-use web service, in line with the EU Open Science Strategic Priority. The workshop provided ten key recommendations of best practices for CS projects on IAS, addressed to researchers, policy makers and implementing authorities, indicating future research and policy directions and opportunities

    Platelet function in brown bear (Ursus arctos) compared to man

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    The article can also be located here: http://www.thrombosisjournal.com/content/8/1/11Background: Information on hemostasis and platelet function in brown bear (Ursus arctos) is of importance for understanding the physiological, protective changes during hibernation. Objective: The study objective was to document platelet activity values in brown bears shortly after leaving the den and compare them to platelet function in healthy humans. Methods: Blood was drawn from immobilized wild brown bears 7-10 days after leaving the den in mid April. Blood samples from healthy human adults before and after clopidogrel and acetylsalicylic acid administration served as control. We analyzed blood samples by standard blood testing and platelet aggregation was quantified after stimulation with various agonists using multiple electrode aggregometry within 3 hours of sampling. Results: Blood samples were collected from 6 bears (3 females) between 1 and 16 years old and from 10 healthy humans. Results of adenosine diphosphate, aspirin, and thrombin receptor activating peptide tests in bears were all half or less of those in humans. Platelet and white blood cell counts did not differ between species but brown bears had more and smaller red blood cells compared with humans. Conclusion: Using three different tests, we conclude that platelet function is lower in brown bears compared to humans. Our findings represent the first descriptive study on platelet function in brown bears and may contribute to explain how bears can endure denning without obvious thrombus building. However, the possibility that our findings reflect test-dependent and not true biological variations in platelet reactivity needs further studies

    Detection of human papillomavirus DNA and p53 codon 72 polymorphism in prostate carcinomas of patients from Argentina

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    BACKGROUND: Infections with high-risk human papillomaviruses (HPVs), causatively linked to cervical cancer, might also play a role in the development of prostate cancer. Furthermore, the polymorphism at codon 72 (encoding either arginine or proline) of the p53 tumor-suppressor gene is discussed as a possible determinant for cancer risk. The HPV E6 oncoprotein induces degradation of the p53 protein. The aim of this study was to analyse prostate carcinomas and hyperplasias of patients from Argentina for the presence of HPV DNA and the p53 codon 72 polymorphism genotype. METHODS: HPV DNA detection and typing were done by consensus L1 and type-specific PCR assays, respectively, and Southern blot hybridizations. Genotyping of p53 codon 72 polymorphism was performed both by allele specific primer PCRs and PCR-RFLP (Bsh1236I). Fischer's test with Woolf's approximation was used for statistical analysis. RESULTS: HPV DNA was detected in 17 out of 41 (41.5 %) carcinoma samples, whereas all 30 hyperplasia samples were HPV-negative. Differences in p53 codon 72 allelic frequencies were not observed, neither between carcinomas and hyperplasias nor between HPV-positive and HPV-negative carcinomas. CONCLUSION: These results indicate that the p53 genotype is probably not a risk factor for prostate cancer, and that HPV infections could be associated with at least a subset of prostate carcinomas
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