432 research outputs found

    Diluted Networks of Nonlinear Resistors and Fractal Dimensions of Percolation Clusters

    Full text link
    We study random networks of nonlinear resistors, which obey a generalized Ohm's law, VIrV\sim I^r. Our renormalized field theory, which thrives on an interpretation of the involved Feynman Diagrams as being resistor networks themselves, is presented in detail. By considering distinct values of the nonlinearity r, we calculate several fractal dimensions characterizing percolation clusters. For the dimension associated with the red bonds we show that dred=1/νd_{\scriptsize red} = 1/\nu at least to order {\sl O} (\epsilon^4), with ν\nu being the correlation length exponent, and ϵ=6d\epsilon = 6-d, where d denotes the spatial dimension. This result agrees with a rigorous one by Coniglio. Our result for the chemical distance, d_{\scriptsize min} = 2 - \epsilon /6 - [ 937/588 + 45/49 (\ln 2 -9/10 \ln 3)] (\epsilon /6)^2 + {\sl O} (\epsilon^3) verifies a previous calculation by one of us. For the backbone dimension we find D_B = 2 + \epsilon /21 - 172 \epsilon^2 /9261 + 2 (- 74639 + 22680 \zeta (3))\epsilon^3 /4084101 + {\sl O} (\epsilon^4), where ζ(3)=1.202057...\zeta (3) = 1.202057..., in agreement to second order in ϵ\epsilon with a two-loop calculation by Harris and Lubensky.Comment: 29 pages, 7 figure

    Remarks on 2+1 Self-dual Chern-Simons Gravity

    Get PDF
    We study 2+1 Chern-Simons gravity at the classical action level. In particular we rederive the linear combinations of the ``standard'' and ``exotic'' Einstein actions, from the (anti) self-duality of the ``internal'' Lorentzian indices. The relation to a genuine four-dimensional (anti)self-dual topological theory greatly facilitates the analysis and its relation to hyperbolic three-dimensional geometry. Finally a non-abelian vector field ``dual'' action is also obtained.Comment: 16+1 pages, LaTeX file, no figures, clarifications and comments added, typos corrected and one reference adde

    Credible intervals for nanoparticle characteristics

    Get PDF
    Solving the inverse problem of nanoparticle characterization has the potential to advance science and benefit society. While considerable progress has been made within a framework based on the scattering of surface plasmon-polaritons, an aspect not heretofore considered is the quantification of uncertainty in the estimation of a nanoparticle characteristic. Therefore, the present article offers a technique by which an investigator may augment an estimate of a nanoparticle characteristic with a companion “credible interval”. Analogous to the familiar confidence interval but arising from within the Bayesian statistical paradigm, a credible interval allows the investigator to make a statement such as “the nanoparticle diameter lies between 36 and 48 nm with 95% probability” instead of merely “the nanoparticle diameter is estimated to be 42 nm”. Our technique may even be applied outside of the surface plasmon-polariton scattering framework, as long as the investigator specifies his/her prior beliefs about the nanoparticle characteristic and indicates which potential outcomes are likely or unlikely in whatever experiment he/she designs to estimate the nanoparticle characteristic. Two numerical studies illustrate the implementation and performance of our technique in constructing ranges of likely values for nanoparticle diameters and agglomeration levels, respectively.NSFpre-prin

    Normative resistance to responsibility to protect in times of emerging multipolarity: the cases of Brazil and Russia

    Get PDF
    This article assesses the normative resistance to Responsibility to Protect adopted by Brazil and Russia against the backdrop of their international identities and self-assigned roles in a changing global order. Drawing upon the framework of Bloomsfield's norm dynamics role spectrum, it argues that while the ambiguous Russian role regarding this principle represents an example of 'norm antipreneurship', particularities of Brazil's resistance are better grasped by a new category left unaccounted for by this model, which this study portrays as 'contesting entrepreneur'.- (undefined

    Credible intervals for nanoparticle characteristics

    Get PDF
    Solving the inverse problem of nanoparticle characterization has the potential to advance science and benefit society. While considerable progress has been made within a framework based on the scattering of surface plasmon-polaritons, an aspect not heretofore considered is the quantification of uncertainty in the estimation of a nanoparticle characteristic. Therefore, the present article offers a technique by which an investigator may augment an estimate of a nanoparticle characteristic with a companion “credible interval”. Analogous to the familiar confidence interval but arising from within the Bayesian statistical paradigm, a credible interval allows the investigator to make a statement such as “the nanoparticle diameter lies between 36 and 48 nm with 95% probability” instead of merely “the nanoparticle diameter is estimated to be 42 nm”. Our technique may even be applied outside of the surface plasmon-polariton scattering framework, as long as the investigator specifies his/her prior beliefs about the nanoparticle characteristic and indicates which potential outcomes are likely or unlikely in whatever experiment he/she designs to estimate the nanoparticle characteristic. Two numerical studies illustrate the implementation and performance of our technique in constructing ranges of likely values for nanoparticle diameters and agglomeration levels, respectively.NSFpre-prin

    Factors associated with self-assessed increase in tobacco consumption among over-indebted individuals in Germany: a cross-sectional study

    Get PDF
    Background Over-indebtedness is an increasing phenomenon in industrialised nations causing individual hardship and societal problems. Nonetheless, few studies have explored smoking among over-indebted individuals. Methods A cross-sectional survey (n=949) on retrospectively assessed changes in tobacco consumption was carried out in 2006 and 2007 among clients of 84 officially approved debt and insolvency counselling centres in Germany (response rate 39.7%). Logistic regressions were performed to explore factors associated with reports of increased smoking after onset of over-indebtedness. Results 63% of all respondents stated daily or occasional tobacco consumption. Almost one fifth reported an increase in smoking after becoming over-indebted. Females were less likely to report increased smoking than men (aOR 0.66, 95% CI 0.44-0.99) whereas respondents who had been over-indebted for more than 10 years were more likely to report increased smoking than those who had been over-indebted for less than five years (aOR 1.66; 95%-CI 1.00-2.76). The odds of increased smoking were also elevated among those who reported that their families and friends had withdrawn from them as a consequence of their over-indebtedness (aOR 1.82; 95%-CI 1.06-3.14). Conclusions The study identifies over-indebted individuals and particularly over-indebted men as a high-risk group of smokers. Low levels of social embeddedness/support were associated with a further increase in smoking after becoming over-indebted. Given recent increases of over-indebtedness, the findings highlight the need to develop appropriate public health policies

    Minimum pricing of alcohol versus volumetric taxation:which policy will reduce heavy consumption without adversely affecting light and moderate consumers?

    Get PDF
    Background We estimate the effect on light, moderate and heavy consumers of alcohol from implementing a minimum unit price for alcohol (MUP) compared with a uniform volumetric tax. Methods We analyse scanner data from a panel survey of demographically representative households (n = 885) collected over a one-year period (24 Jan 2010–22 Jan 2011) in the state of Victoria, Australia, which includes detailed records of each household's off-trade alcohol purchasing. Findings The heaviest consumers (3% of the sample) currently purchase 20% of the total litres of alcohol (LALs), are more likely to purchase cask wine and full strength beer, and pay significantly less on average per standard drink compared to the lightest consumers (A1.31[951.31 [95% CI 1.20–1.41] compared to 2.21 [95% CI 2.10–2.31]). Applying a MUP of A1perstandarddrinkhasagreatereffectonreducingthemeanannualvolumeofalcoholpurchasedbytheheaviestconsumersofwine(15.78LALs[951 per standard drink has a greater effect on reducing the mean annual volume of alcohol purchased by the heaviest consumers of wine (15.78 LALs [95% CI 14.86–16.69]) and beer (1.85 LALs [95% CI 1.64–2.05]) compared to a uniform volumetric tax (9.56 LALs [95% CI 9.10–10.01] and 0.49 LALs [95% CI 0.46–0.41], respectively). A MUP results in smaller increases in the annual cost for the heaviest consumers of wine (393.60 [95% CI 374.19–413.00]) and beer (108.26[95108.26 [95% CI 94.76–121.75]), compared to a uniform volumetric tax (552.46 [95% CI 530.55–574.36] and $163.92 [95% CI 152.79–175.03], respectively). Both a MUP and uniform volumetric tax have little effect on changing the annual cost of wine and beer for light and moderate consumers, and likewise little effect upon their purchasing. Conclusions While both a MUP and a uniform volumetric tax have potential to reduce heavy consumption of wine and beer without adversely affecting light and moderate consumers, a MUP offers the potential to achieve greater reductions in heavy consumption at a lower overall annual cost to consumers

    The growth in newspaper coverage of tobacco control in China, 2000-2010

    Get PDF
    <p>Abstract</p> <p>Background</p> <p>Media coverage of tobacco-related issues can potentially shape individual beliefs, attitudes and behaviors about tobacco use. This study aims to describe news coverage of tobacco control related issues in Chinese newspapers from 2000 to 2010.</p> <p>Methods</p> <p>All 1149 articles related to tobacco control were extracted from the Database of Chinese Important Newspapers and content analyzed for the period Jan 1, 2000 to Dec 31, 2010. The changing pattern of tobacco control topic, article type, viewpoint, and article origin, and their relationship were analysed.</p> <p>Results</p> <p>News coverage of tobacco control related issues increased significantly (<it>p </it>< 0.01) from 2000 to 2010, with news coverage being relatively intensive in May and June (<it>p </it>< 0.01), around World No Tobacco Day. 24.9% (n = 286) of all articles focused on secondhand smoke, 25.3% (n = 291) warned about the dangers of active smoking, and 10.0% (n = 115) focused on prevention and cessation programs and campaigns. Tobacco control topics varied significantly between national vs city/regional newspapers (<it>χ</it><sup>2 </sup>= 24.09, <it>p </it>= 0.002) and article types (<it>χ</it><sup>2 </sup>= 193.35, <it>p </it>< 0.001). Articles in national newspapers had more coverage of the dangers of tobacco and on enforcing bans on tobacco-advertising. News stories centered around monitoring tobacco use and smoke free activity, while editorials focused on enforcing bans on tobacco-advertising, youth access and programs and campaigns. Letters to editors focused on the dangers of smoking, raising tax, and smoking cessation. More articles (50.4%) took an anti-tobacco position (compared with 10.5% which were pro-smoking), with the amount of negative coverage growing significantly across the decade. National articles tended to lean toward anti-tobacco, however, local articles tended mix of pro-tobacco and neutral/balance positions. Editorials seemed to be more anti-tobacco oriented, but letters to the editor tended to show a mix of anti-tobacco and pro-tobacco positions.</p> <p>Conclusion</p> <p>Chinese newspapers are giving increasing attention to tobacco control, but coverage remains lower than in the USA and Australia. Health workers need to give higher priority to efforts to increase news coverage beyond the present concentration around World No Tobacco Day and to develop strategies for making tobacco control issues more newsworthy to both national and local news outlets.</p

    Blood pressure and cholesterol level checks as dynamic interrelated screening examinations

    Get PDF
    This study analysed the determinants of screening uptake for blood pressure and cholesterol level checks. Furthermore, it investigated the presence of possible spillover effects from one type of cardiovascular screening to another type of cardiovascular screening. A dynamic random effects bivariate panel probit model with initial conditions (Wooldridge-type estimator) was adopted for the estimation. The outcome variables were the participation in blood pressure and cholesterol level checks by individuals in a given year. The balanced panel sample of 21,138 observations was constructed from 1,626 individuals from the British Household Panel Survey (BHPS) between 1996 and 2008. The analysis showed the significance of past screening behaviour for both cardiovascular screening examinations. For both cardiovascular screening examinations state dependence exist. The study also shows a significant spillover effect of the cholesterol level check on the blood pressure check and vice versa. Also a poorer health status led to a higher uptake for both types of screening examinations. Changes in recommendations have to consider the fact that taking part in one type of cardiovascular screening examination can influence the decision to take part in the other type of cardiovascular screening examination
    corecore