27 research outputs found

    Wiedemann-Franz law and abrupt change in conductivity across the pseudogap critical point of a cuprate superconductor

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    The thermal conductivity κ\kappa of the cuprate superconductor La1.6x_{1.6-x}Nd0.4_{0.4}Srx_xCuO4_4 was measured down to 50 mK in seven crystals with doping from p=0.12p=0.12 to p=0.24p=0.24, both in the superconducting state and in the magnetic field-induced normal state. We obtain the electronic residual linear term κ0/T\kappa_0/T as T0T \to 0 across the pseudogap critical point p=0.23p^{\star}= 0.23. In the normal state, we observe an abrupt drop in κ0/T\kappa_0/T upon crossing below pp^{\star}, consistent with a drop in carrier density nn from 1+p1 + p to pp, the signature of the pseudogap phase inferred from the Hall coefficient. A similar drop in κ0/T\kappa_0/T is observed at H=0H=0, showing that the pseudogap critical point and its signatures are unaffected by the magnetic field. In the normal state, the Wiedemann-Franz law, κ0/T=L0/ρ(0)\kappa_0/T=L_0/\rho(0), is obeyed at all dopings, including at the critical point where the electrical resistivity ρ(T)\rho(T) is TT-linear down to T0T \to 0. We conclude that the non-superconducting ground state of the pseudogap phase at T=0T=0 is a metal whose fermionic excitations carry heat and charge as conventional electrons do.Comment: 10 pages, including Supplementary Materia

    Evaluation of alternative respiratory syndromes for specific syndromic surveillance of influenza and respiratory syncytial virus: a time series analysis

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    <p>Abstract</p> <p>Background</p> <p>Syndromic surveillance is increasingly being evaluated for its potential for early warning of increased disease activity in the population. However, interpretation is hampered by the difficulty of attributing a causative pathogen. We described the temporal relationship between laboratory counts of influenza and respiratory syncytial virus (RSV) detection and alternative groupings of Emergency Department (ED) respiratory diagnoses.</p> <p>Methods</p> <p>ED and laboratory data were obtained for the south-eastern area of Sydney, NSW for the period 1 June 2001 - 1 December 2006. Counts of ED visits and laboratory confirmed positive RSV and influenza cases were aggregated by week. Semi-parametric generalized additive models (GAM) were used to determine the association between the incidence of RSV and influenza and the incidence of respiratory syndrome ED presentations while controlling for temporal confounders.</p> <p>Results</p> <p>For every additional RSV laboratory count, ED diagnoses of bronchiolitis increased by 3.1% (95%CI: 2.7%-3.5%) in the same week. For every additional influenza laboratory count, ED diagnoses of influenza-like illness increased by 4.7% (95%CI: 4.2%-5.2%) one week earlier.</p> <p>Conclusion</p> <p>In this study, large increases in ED diagnoses of bronchiolitis and influenza-like illness were independent and proxy indicators for RSV and influenza activity, respectively.</p

    Value of syndromic surveillance within the Armed Forces for early warning during a dengue fever outbreak in French Guiana in 2006

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    <p>Abstract</p> <p>Background</p> <p>A dengue fever outbreak occured in French Guiana in 2006. The objectives were to study the value of a syndromic surveillance system set up within the armed forces, compared to the traditional clinical surveillance system during this outbreak, to highlight issues involved in comparing military and civilian surveillance systems and to discuss the interest of syndromic surveillance for public health response.</p> <p>Methods</p> <p>Military syndromic surveillance allows the surveillance of suspected dengue fever cases among the 3,000 armed forces personnel. Within the same population, clinical surveillance uses several definition criteria for dengue fever cases, depending on the epidemiological situation. Civilian laboratory surveillance allows the surveillance of biologically confirmed cases, within the 200,000 inhabitants.</p> <p>Results</p> <p>It was shown that syndromic surveillance detected the dengue fever outbreak several weeks before clinical surveillance, allowing quick and effective enhancement of vector control within the armed forces. Syndromic surveillance was also found to have detected the outbreak before civilian laboratory surveillance.</p> <p>Conclusion</p> <p>Military syndromic surveillance allowed an early warning for this outbreak to be issued, enabling a quicker public health response by the armed forces. Civilian surveillance system has since introduced syndromic surveillance as part of its surveillance strategy. This should enable quicker public health responses in the future.</p
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