Modelling forest–savanna mosaic dynamics in man-influenced environments: effects of fire, climate and soil heterogeneity

Forests and savannas are the major ecotypes in humid tropical regions. Under present climatic conditions, forest is in a phase of natural expansion over savanna, but traditional human activities, especially fires, have strongly influenced the succession. We here present a new model, FORSAT, dedicated to the forest–savanna mosaic on a landscape scale and based on stochastic modelling of key processes (fire and succession cycle) and consistent with common field data. The model is validated by comparison between the qualitative emergent behaviour of the model and results of biogeographical field studies. Three types of forest succession are shown: progression of the forest edge, formation and coalescence of clumps in savanna and global afforestation of savanna. The parameters (frequency of savanna fires, climate and soil fertility) appear to have comparable effects and there is a sharp threshold between a forest edge progression scenario and the cluster formation one. Moreover, pioneer seed dispersal pattern and recruitment are determinant: peaked curves near a seed source and far dispersal combine to increase the fitness of the pioneers

Preparation of multi-allylic dendronized polymers via atom-transfer radical polymerization

International audienceAtom-transfer radical polymerization (ATRP) was investigated to polymerize a styrene monomer carrying carbosilane dendrons with 6 terminal allyl branches. Polymers with a monomodal molar mass distribution and low polydispersity have been produced, while by comparison the free-radical polymerization technique led to chain transfer early in the polymerization. Steric effect brought by the dendrons result in a slow polymerization rate, leading to an apparent saturation of the degree of polymerization. By pushing up the polymerization conditions (eg. increase of temperature or concentration), interchain couplings started to take place, most likely from reactions at the allyl branches. These results are very similar to the ones previously reported for the anionic polymerization of this same multi-allylic dendronized monomer. § present addresses: P.O. Schwartz, Alsachim SAS

Symmetric microwave potentials for interferometry with thermal atoms on a chip

International audienceA trapped atom interferometer involving state-selective adiabatic potentials with two microwave frequencies on a chip is proposed. We show that this configuration provides a way to achieve a high degree of symmetry between the two arms of the interferometer, which is necessary for coherent splitting and recombination of thermal (i.e., noncondensed) atoms. The resulting interferometer holds promise to achieve high contrast and long coherence time, while avoiding the mean-field interaction issues of interferometers based on trapped Bose-Einstein condensates

190: In how many patients with Wolff-Parkinson-White syndrome-related adverse presentation isoproterenol infusion was required to reproduce the arrhythmia?

Electrophysiological study is the main method for the detection of patients with a Wolff-Parkinson-White syndrome (WPW) at risk of adverse presentation (resuscitated ventricular fibrillation (VF), documented life-threatening arrhythmia): the protocol is debated. The purpose of the study was to look in how many patients with WPW-related adverse presentation, atrial fibrillation (AF) or atrial tachycardia with the shortest RR cycle length (CL) with 1/1 conduction over accessory pathway (AP)<250msec was induced in control state (CS) and when isoproterenol was required.Methods63 patients, mean age 38±18, were referred for WPW-related adverse presentation (VF 6, other 56). EPS included in CS atrial pacing and measurement of the shortest CL with 1/1 conduction over AP and programmed stimulation with 1 and 2 extrastimuli. AP effective refractory period (ERP) was determined. In absence of induction of a tachycardia with a CL <250msec, isoproterenol (0.02 to 1μg. min-1) was infused to increase sinus rate to 130bpm; the protocol was repeated.ResultsMean shortest CL conducted over AP was 223±30msec in CS, 192±25msec after isoproterenol. APERP was 225±29msec in CS, 191±19msec after isoproterenol. Atrioventricular orthodromic tachycardia (AVRT) was induced in 34 patients (54%), antidromic tachycardia (ATD) in 13 (21%), AF in 43 (68%). Criteria for a malignant form (induction of AF or ATD with a shortest CL <250mesc) were noted in 42 patients (67%) in CS and were obtained after isoproterenol in remaining 21 patients (33%). Among these patients, 12 had inducible tachycardia in CS (AVRT (n=6), ATD (n=3), AF (n=3) but the shortest CL was >240msec. A tachycardia was only induced after isoproterenol in 9 patients (14%).ConclusionsInfusion of isoproterenol should be systematic when WPW is evaluated. EPS performed only in CS missed at least 14% of patients at risk of life-threatening arrhythmias who had no inducible supraventricular tachyarrhythmia and 33% of patients with a WPW without the classical criteria for a malignant form. Isoproterenol increased the sensitivity of EPS for the detection of malignant form from 67 to 100%

Relationship between ozone and temperature during the 2003 heat wave in France: consequences for health data analysis

BACKGROUND: PAPRICA is a research program designed to estimate the impact on the health of patients with chronic respiratory insufficiency of a prevention strategy based on notification of ozone pollution. The first year of this study was conducted during the 2003 heat wave, and high temperatures were therefore considered as a confounding factor in the data analysis. The aim of the present study was to assess the relationship between ozone and temperature in order to propose a methodology to distinguish between the effects of ozone and temperature on the impact of a prevention strategy with regard to ozone pollution. METHODS: Multivariate analyses were used to identify associated climate and ozone pollution profiles. This descriptive method is of great value to highlight the complexity of interactions between these parameters. RESULTS: Ozone concentration and temperature were strongly correlated, but the health impact of ozone pollution alone will be evaluated by focusing on situations characterized by ozone concentrations above 110 μg/m(3)/8h (air quality guidelines to protect human health defined by the French legislation) and temperatures lower than 26°C, below the discomfort threshold. CONCLUSION: The precise relationship between ambient ozone concentration and temperature identified during the PAPRICA 2003 study period will be used in analysing the PAPRICA health data

092: Prognosis value of QRS duration in patients with heart disease and syncope

BackgroundPatients with heart disease (HD) and syncope are at high risk of sudden death. Implantable defibrillator (ICD) is recommended in patients with unexplained syncope and left ventricular ejection fraction (LVEF) < 30% or in patients with LVEF >30% and inducible ventricular tachycardia (VT).AimThe purpose of the study was to evaluate the prognostic significance of QRS duration measurement in patients with HD and syncope.Methods528 patients, 89 women and 439 men, mean age 65±12 years, were admitted for syncope. All of them had an HD, either ischemic HD (n=382) or left ventricular impairment of other origin (n=115). Holter monitoring, electrophysiological study and head-up tilt test were systematic. Filtered QRS duration was measured at signal-averaged ECG (Fidelity 2000 of Cardionics) (filter 40 Hz, noise level < 0.6 μV). The patients were followed from 3 months up to 18 years (mean 5 ±4 years).ResultsMean LVEF was 40±14%. Cardiac defibrillator was implanted in 73 patients. 30 patients died suddenly, 75 died from heart failure or were transplanted (n=9). Remaining patients are alive or died from non cardiac death (n= 8). The last group differed from group who died suddenly by an higher LVEF (42±14% vs 32±13) (p< 0.00001) and a shorter QRS duration (125±34 msec vs 144±31) (p< 0.026). They tended to be older (65±12 years vs 61±13) (p<0.09). The alive group differed also from group who died from heart failure by an higher LVEF (42±14% vs 33±13) (p< 0.001) and a shorter QRS duration (125±34 msec vs 141±31) (p< 0.0033). They tended to be younger (65±12 years vs 67±10) (p<0.08). Patients who died suddenly and those who died from heart failure had similar LVEF and QRS duration but patients who died suddenly are younger than patients who died from heart failure (p<0.01).ConclusionsLow LVEF is a classical risk of worse prognosis in patients with HD and syncope. A longer QRS duration is also a noninvasive and simple test of worse prognosis. A QRS duration more than 125 msec had a sensitivity of 73% and a specificity of 64% to predict cardiac mortality

Testing and Assessment in an International Context: Cross- and Multi-cultural Issues

Globalisation, increase of migration flows, and the concurrent worldwide competitiveness impose rethinking of testing and assessment procedures and practices in an international and multicultural context. This chapter reviews the methodological and practical implications for psychological assessment in the field of career guidance. The methodological implications are numerous and several aspects have to be considered, such as cross-cultural equivalence or construct, method, and item bias. Moreover, the construct of culture by itself is difficult to define and difficult to measure. In order to provide non-discriminatory assessment, counsellors should develop their clinical cross-cultural competencies, develop more specific intervention strategies, and respect cultural differences. Several suggestions are given concerning translation and adaptation of psychological instruments, developing culture specific measures, and the use of these instruments. More research in this field should use mixed methods, multi-centric designs, and consider emic and etic psychological variables. A multidisciplinary approach might also allow identifying culture specific and ecological meaningful constructs. Non-discriminatory assessment implies considering the influence and interaction of personal characteristics and environmental factors

Phylo: A Citizen Science Approach for Improving Multiple Sequence Alignment

BACKGROUND: Comparative genomics, or the study of the relationships of genome structure and function across different species, offers a powerful tool for studying evolution, annotating genomes, and understanding the causes of various genetic disorders. However, aligning multiple sequences of DNA, an essential intermediate step for most types of analyses, is a difficult computational task. In parallel, citizen science, an approach that takes advantage of the fact that the human brain is exquisitely tuned to solving specific types of problems, is becoming increasingly popular. There, instances of hard computational problems are dispatched to a crowd of non-expert human game players and solutions are sent back to a central server. METHODOLOGY/PRINCIPAL FINDINGS: We introduce Phylo, a human-based computing framework applying "crowd sourcing" techniques to solve the Multiple Sequence Alignment (MSA) problem. The key idea of Phylo is to convert the MSA problem into a casual game that can be played by ordinary web users with a minimal prior knowledge of the biological context. We applied this strategy to improve the alignment of the promoters of disease-related genes from up to 44 vertebrate species. Since the launch in November 2010, we received more than 350,000 solutions submitted from more than 12,000 registered users. Our results show that solutions submitted contributed to improving the accuracy of up to 70% of the alignment blocks considered. CONCLUSIONS/SIGNIFICANCE: We demonstrate that, combined with classical algorithms, crowd computing techniques can be successfully used to help improving the accuracy of MSA. More importantly, we show that an NP-hard computational problem can be embedded in casual game that can be easily played by people without significant scientific training. This suggests that citizen science approaches can be used to exploit the billions of "human-brain peta-flops" of computation that are spent every day playing games. Phylo is available at: http://phylo.cs.mcgill.ca