Colouring triangle-free graphs with local list sizes

We prove two distinct and natural refinements of a recent breakthrough result of Molloy (and a follow-up work of Bernshteyn) on the (list) chromatic number of triangle-free graphs. In both our results, we permit the amount of colour made available to vertices of lower degree to be accordingly lower. One result concerns list colouring and correspondence colouring, while the other concerns fractional colouring. Our proof of the second illustrates the use of the hard-core model to prove a Johansson-type result, which may be of independent interest.Comment: 16 pages; v2 includes minor corrections after review; to appear in Random Structures & Algorithm

Quantification of airborne road-side pollution carbon nanoparticles

Roadside diesel particulate matter (DPM) has been collected using a P-Trak particle counter with modified inlet filter. The P-Trak monitor assesses ultrafine particle number in real-time rather than accumulated PM mass over a period of time, which is important for DPM where the particles are often <100nm in size. Collected pollution particulate matter was analysed by SEM and TEM, quantifying particle size, morphology and size distribution. The primary carbon nanoparticles form complex fractal aggregates with open porous morphologies and evidence of secondary carbon deposition. For the chosen collection sites, occasional but significantly larger mineral and fibrous particles were identified. The assessment of airborne particles by mass collection (TEOM), particle-number (P-Trak) and TEM methods is discussed

Effects of air pollution and the introduction of the London Low Emission Zone on the prevalence of respiratory and allergic symptoms in schoolchildren in East London: a sequential cross-sectional study

The adverse effects of traffic-related air pollution on children’s respiratory health have been widely reported, but few studies have evaluated the impact of traffic-control policies designed to reduce urban air pollution. We assessed associations between traffic-related air pollutants and respiratory/allergic symptoms amongst 8–9 year-old schoolchildren living within the London Low Emission Zone (LEZ). Information on respiratory/allergic symptoms was obtained using a parent-completed questionnaire and linked to modelled annual air pollutant concentrations based on the residential address of each child, using a multivariable mixed effects logistic regression analysis. Exposure to traffic-related air pollutants was associated with current rhinitis: NOx (OR 1.01, 95% CI 1.00–1.02), NO2 (1.03, 1.00–1.06), PM10 (1.16, 1.04–1.28) and PM2.5 (1.38, 1.08–1.78), all per μg/m3 of pollutant, but not with other respiratory/allergic symptoms. The LEZ did not reduce ambient air pollution levels, or affect the prevalence of respiratory/allergic symptoms over the period studied. These data confirm the previous association between traffic-related air pollutant exposures and symptoms of current rhinitis. Importantly, the London LEZ has not significantly improved air quality within the city, or the respiratory health of the resident population in its first three years of operation. This highlights the need for more robust measures to reduce traffic emissions

Contemporary carbon fluxes do not reflect the long-term carbon balance for an Atlantic blanket bog

Peatlands are one of the largest terrestrial stores of carbon. Carbon exchange in peatlands is often assessed solely by measurement of contemporary fluxes; however, these fluxes frequently indicate a much stronger sink strength than that measured by the rate of C accumulation in the peat profile over longer timescales. Here we compare profile-based measurements of C accumulation with the published net ecosystem C balance for the largest peatland area in Britain, the Flow Country of northern Scotland. We estimate the long-term rate of C accumulation to be 15.4 g C m−2 yr−1 for a site where a recent eddy covariance study has suggested contemporary C uptake more than six times greater (99.37 g C m−2 yr−1). Our estimate is supported by two further long-term C accumulation records from nearby sites which give comparable results. We demonstrate that a strong contemporary C sink strength may not equate to a strong long-term sink and explore reasons for this disparity. We recommend that contemporary C sequestration should be viewed in the context of the long-term ecological drivers, such as fires, ecohydrological feedbacks and the changing quality of litter inputs

Reduced Quantitative Ultrasound Bone Mineral Density in HIV-Infected Patients on Antiretroviral Therapy in Senegal

Background: Bone status in HIV-infected patients on antiretroviral treatment (ART) is poorly documented in resource-limited settings. We compared bone mineral density between HIV-infected patients and control subjects from Dakar, Senegal. Methods: A total of 207 (134 women and 73 men) HIV-infected patients from an observational cohort in Dakar (ANRS 1215) and 207 age-and sex-matched controls from the general population were enrolled. Bone mineral density was assessed by quantitative ultrasound (QUS) at the calcaneus, an alternative to the reference method (i.e. dual X-absorptiometry), often not available in resource-limited countries. Results: Mean age was 47.0 (+/- 8.5) years. Patients had received ART for a median duration of 8.8 years; 45% received a protease inhibitor and 27% tenofovir; 84% had undetectable viral load. Patients had lower body mass index (BMI) than controls (23 versus 26 kg/m(2), P<0.001). In unadjusted analysis, QUS bone mineral density was lower in HIV-infected patients than in controls (difference: -0.36 standard deviation, 95% confidence interval (CI): -0.59;-0.12, P = 0.003). Adjusting for BMI, physical activity, smoking and calcium intake attenuated the difference (-0.27, CI: -0.53; -0.002, P = 0.05). Differences in BMI between patients and controls explained a third of the difference in QUS bone mineral density. Among patients, BMI was independently associated with QUS bone mineral density (P<0.001). An association between undetectable viral load and QUS bone density was also suggested (beta = 0.48, CI: 0.02; 0.93; P = 0.04). No association between protease inhibitor or tenofovir use and QUS bone mineral density was found. Conclusion: Senegalese HIV-infected patients had reduced QUS bone mineral density in comparison with control subjects, in part related to their lower BMI. Further investigation is needed to clarify the clinical significance of these observations

Etude d'un modèle unidimensionnel pour les contacts thermiques en régime instationnaire

We show that in a cylindrical heat flux tube (which direction is Ox) including a heterogeneous layer, it is possible to define a mean temperature field T(x, t) continuous for évery value of x. The contact heterogeneous layer may be characterized by apparent thermophysical parameters in the Ox direction. Then, the one-dimensional model of contact includes three homogeneous layers in perfect contact, and may be linearized. This model is also convenient to describe the heat or mass transfer in various kinds of heterogeneous or porous média ; and its accuracy is verified by the mean of a numerical method.On montre que dans un tube de flux cylindrique de direction parallèle à Ox et comportant une couche hétérogène, il est possible de définir un champ moyen de température T(x, t) continu pour tout x. On en déduit l'expression approchée, pour la couche hétérogène, d'une conductivité λ a et d'une chaleur volumique cρa apparentes. Le modèle unidimensionnel de contact thermique consiste alors en un schéma à trois couches homogènes en contact parfait. Ce modèle s'applique également à diverses catégories de ponts thermiques, de matériaux composites ou d'écoulements en milieux poreux. Il est vérifié avec une très bonne précision dans le cas de signaux thermiques du type échelon ou créneau, et constitue une bonne approximation pour des signaux triangulaires

Etude d'un modèle unidimensionnel pour les contacts thermiques en régime instationnaire

On montre que dans un tube de flux cylindrique de direction parallèle à Ox et comportant une couche hétérogène, il est possible de définir un champ moyen de température T(x, t) continu pour tout x. On en déduit l'expression approchée, pour la couche hétérogène, d'une conductivité λ a et d'une chaleur volumique cρa apparentes. Le modèle unidimensionnel de contact thermique consiste alors en un schéma à trois couches homogènes en contact parfait. Ce modèle s'applique également à diverses catégories de ponts thermiques, de matériaux composites ou d'écoulements en milieux poreux. Il est vérifié avec une très bonne précision dans le cas de signaux thermiques du type échelon ou créneau, et constitue une bonne approximation pour des signaux triangulaires

Economic, Environmental and International Trade Effects of the EU Directive on Energy Tax Harmonization

In October 2003, the European Union introduced a Directive which widens the scope of the EU’s minimum taxation system from mineral oils to all energy products including coal, natural gas and electricity. It aims at reducing distortions that currently exist between Member States as well as between energy products. In addition, the Directive increases incentives to use energy more efficiently. This will lead to changes in the energy tax schemes in a number of countries, in particular some southern Member Countries (Greece, Spain, Portugal) and most of the Eastern European EU candidate countries. In this paper, we analyze the effects of the EU energy tax harmonization, with particular focus on the EU acceding Eastern European countries with GTAP-E, a computable general equilibrium model. We investigate the effects of the tax harmonization on overall economic growth and sectoral development. Special attention is paid to international trade in order to analyze if competitiveness concerns which have been frequently forwarded in the context of energy taxation are valid. Furthermore, the effect on energy consumption and emissions and thus the contribution to the EU’s climate change targets is analyzed