271 research outputs found

    Fast and reliable pricing of American options with local volatility

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    We present globally convergent multigrid methods for the nonsymmetric obstacle problems as arising from the discretization of Black—Scholes models of American options with local volatilities and discrete data. No tuning or regularization parameters occur. Our approach relies on symmetrization by transformation and data recovery by superconvergence

    Global-scale climate impact functions: the relationship between climate forcing and impact

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    Although there is a strong policy interest in the impacts of climate change corresponding to different degrees of climate change, there is so far little consistent empirical evidence of the relationship between climate forcing and impact. This is because the vast majority of impact assessments use emissions-based scenarios with associated socio-economic assumptions, and it is not feasible to infer impacts at other temperature changes by interpolation. This paper presents an assessment of the global-scale impacts of climate change in 2050 corresponding to defined increases in global mean temperature, using spatially-explicit impacts models representing impacts in the water resources, river flooding, coastal, agriculture, ecosystem and built environment sectors. Pattern-scaling is used to construct climate scenarios associated with specific changes in global mean surface temperature, and a relationship between temperature and sea level used to construct sea level rise scenarios. Climate scenarios are constructed from 21 climate models to give an indication of the uncertainty between forcing and response. The analysis shows that there is considerable uncertainty in the impacts associated with a given increase in global mean temperature, due largely to uncertainty in the projected regional change in precipitation. This has important policy implications. There is evidence for some sectors of a non-linear relationship between global mean temperature change and impact, due to the changing relative importance of temperature and precipitation change. In the socio-economic sectors considered here, the relationships are reasonably consistent between socio-economic scenarios if impacts are expressed in proportional terms, but there can be large differences in absolute terms. There are a number of caveats with the approach, including the use of pattern-scaling to construct scenarios, the use of one impacts model per sector, and the sensitivity of the shape of the relationships between forcing and response to the definition of the impact indicator

    Reasons for non-vaccination against HPV and future vaccination intentions among 19-26 year-old women

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    <p>Abstract</p> <p>Background</p> <p>Despite CDC recommendations regarding universal catch-up vaccination against human papillomavirus (HPV), only about ten percent of young adult women in the United States have been vaccinated. The purpose of this study was to better understand reasons for non-vaccination among insured 19-26 year-old women and to evaluate future vaccination intentions.</p> <p>Methods</p> <p>We used an administrative claims database from a large US managed care plan to identify women aged 19-26 for receipt of a mailed survey. From a sample of 1,375 women with no evidence of HPV vaccination from June 1, 2006 through April 30, 2007, 222 completed surveys were received, of which 185 were eligible for this analysis. The main outcome measures were unvaccinated women's attitudes and vaccine awareness, likelihood of future action regarding the vaccine, and reasons for inaction.</p> <p>Results</p> <p>Among the 185 non-vaccinees, 25.4% were married, 83.2% were white, and 89.2% had a college or higher level education. The vaccine was described as very important by 32.4% of subjects, and 30.1% had discussed the vaccine with a doctor and received a doctor's recommendation. Half or fewer of respondents were "very" or "extremely" likely to discuss the vaccine with their doctor (50.0%), do additional research on the vaccine (42.6%), ask a doctor to get the vaccine (37.5%), or make an appointment to get the vaccine (27.8%), while 48.0% were "somewhat", "very", or "extremely" likely to do nothing to get the vaccine. Among the latter, reasons for taking no action included being married or in a monogamous relationship (54.9%), belief that the vaccine is too new (35.4%), not having enough information about the vaccine (31.7%), concerns about side effects (24.4%), and uncertainty about insurance coverage (24.4%).</p> <p>Conclusions</p> <p>Educational interventions may be needed to enhance HPV vaccination rates among 19-26 year-old women, particularly regarding information about vaccine safety, vaccine efficacy, insurance coverage, and the value of vaccination to women in monogamous relationships.</p

    On the analysis of the contact angle for impacting droplets using a polynomial fitting approach

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    ractical considerations on the measurement of the dynamic contact angle and the spreading diameter of impacting droplets are discussed in this paper. The contact angle of a liquid is commonly obtained either by a polynomial or a linear fitting to the droplet profile around the triple phase point. Previous works have focused on quasi-static or sessile droplets, or in cases where inertia does not play a major role on the contact angle dynamics. Here, we study the effect of droplet shape, the order of the fitting polynomial, and the fitting domain, on the measurement of the contact angle on various stages following droplet impact where the contact line is moving. Our results, presented in terms of the optical resolution and the droplet size, show that a quadratic fitting provides the most consistent results for a range of various droplet shapes. As expected, our results show that contact angle values are less sensitive to the fitting conditions for the cases where the droplet can be approximated to a spherical cap. Our experimental conditions include impact events with liquid droplets of different sizes and viscosities on various substrates. In addition, validating past works, our results show that the maximum spreading diameter can be parameterised by the Weber number and the rapidly advancing contact angle

    Characteristics of chronic non-specific musculoskeletal pain in children and adolescents attending a rheumatology outpatients clinic: a cross-sectional study

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    Background: Chronic non-specific musculoskeletal pain (CNSMSP) may develop in childhood and adolescence, leading to disability and reduced quality of life that continues into adulthood. The purpose of the study was to build a biopsychosocial profile of children and adolescents with CNSMSP. Methods: CNSMSP subjects (n = 30, 18 females, age 7-18) were compared with age matched pain free controls across a number of biopsychosocial domains. Results: In the psychosocial domain CNSMSP subjects had increased levels of anxiety and depression, and had more somatic pain complaints. In the lifestyle domain CNSMSP subjects had lower physical activity levels, but no difference in television or computer use compared to pain free subjects. Physically, CNSMSP subjects tended to sit with a more slumped spinal posture, had reduced back muscle endurance, increased presence of joint hypermobility and poorer gross motor skills. Conclusion: These findings support the notion that CNSMSP is a multidimensional biopsychosocial disorder. Further research is needed to increase understanding of how the psychosocial, lifestyle and physical factors develop and interact in CNSMSP

    Bacterial adaptation is constrained in complex communities

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    © 2020, The Author(s). A major unresolved question is how bacteria living in complex communities respond to environmental changes. In communities, biotic interactions may either facilitate or constrain evolution depending on whether the interactions expand or contract the range of ecological opportunities. A fundamental challenge is to understand how the surrounding biotic community modifies evolutionary trajectories as species adapt to novel environmental conditions. Here we show that community context can dramatically alter evolutionary dynamics using a novel approach that ‘cages’ individual focal strains within complex communities. We find that evolution of focal bacterial strains depends on properties both of the focal strain and of the surrounding community. In particular, there is a stronger evolutionary response in low-diversity communities, and when the focal species have a larger genome and are initially poorly adapted. We see how community context affects resource usage and detect genetic changes involved in carbon metabolism and inter-specific interaction. The findings demonstrate that adaptation to new environmental conditions should be investigated in the context of interspecific interactions
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