Fluctuation effects in metapopulation models: percolation and pandemic threshold

Metapopulation models provide the theoretical framework for describing disease spread between different populations connected by a network. In particular, these models are at the basis of most simulations of pandemic spread. They are usually studied at the mean-field level by neglecting fluctuations. Here we include fluctuations in the models by adopting fully stochastic descriptions of the corresponding processes. This level of description allows to address analytically, in the SIS and SIR cases, problems such as the existence and the calculation of an effective threshold for the spread of a disease at a global level. We show that the possibility of the spread at the global level is described in terms of (bond) percolation on the network. This mapping enables us to give an estimate (lower bound) for the pandemic threshold in the SIR case for all values of the model parameters and for all possible networks.Comment: 14 pages, 13 figures, final versio

Prédiction de la performance en natation par les mesures d'activité du Système Nerveux Autonome (modélisation mathématique)

Durant ces 20 dernières années, de nombreuses études réalisées chez l homme ont mis en évidence l utilité de la Variabilité de la Fréquence Cardiaque (VFC) comme outil d investigation de l activité du Système Nerveux Autonome (SNA). Des études longitudinales et transversales ont par ailleurs démontré des relations fortes entre SNA, entrainement et performance. La recherche d indicateurs biologiques permettant au mieux de paramétrer la charge d entraînement a conduit à l étude de différents paramètres parmi lesquels la VFC. L objectif de l ensemble de ce travail de thèse a été, à la fois, l étude de la prédiction de la performance en natation ainsi que la modélisation des effets de l entraînement sur le SNA. L étude I modélise les effets de l entraînement sur l activité parasympathique au travers du modèle de Banister, initialement conçu pour représenter les effets de l entraînement sur la performance. Une relation significative de type logarithmique est démontrée, également, entre l activité parasympathique et la performance. L étude II démontre la pertinence de la VFC dans le pilotage et l optimisation de la charge d entraînement. Cette étude a utilisé les paramètres issus des modèles linéaire et non-linéaire des 10 nageurs pour analyser l influence sur la performance et l activité parasympathique de la charge d entraînement. Cette étude rend compte de l application pratique de la modélisation mathématique et des simulations informatiques dans la prédiction de la performance et l optimisation de la charge d entraînement en vue de maximiser à la fois les gains de performance et d activité parasympathique. L ensemble de ce travail démontre, au travers de la modélisation mathématique des réponses à l entraînement de l activité parasympathique et sa confrontation aux réponses de la performance, que la puissance spectrale en HF est un outil non invasif et facilement utilisable en routine pour optimiser l entraînement. Au-delà de la démonstration d une relation significative, c est la mise en évidence d une évolution en phase de ce paramètre physiologique et de la performance qui a été démontréeOver the past 20 years, numerous studies in humans have demonstrated the usefulness of Heart Rate Variability (HRV) as a tool for investigating the activity of Autonomic Nervous System (ANS). Longitudinal and transversal studies have also shown a strong relationship between ANS activity, training load and performance. Monitoring of the training load has led to the study of various physiological parameters including the HRV. The goal of all this work was the study of the abilities of ANS parameters to predict the level of performance in swimming, as well as, modeling the effects of training load on the parameters of ANS. Study I models the effects of training on parasympathetic activity through the Banister model, originally designed to represent the effects of training on performance. A significant logarithmic relationship was demonstrated between parasympathetic activity and performance. Study II demonstrates the relevance of HRV and mathematical modeling to drive and optimize the training load. This study, using model parameters calculated from linear and non-linear mathematical formulation for 10 swimmers, analyzes the ability of computer simulation to predict performance and parasympathetic activity in response to the training load. The results demonstrate the practical application of mathematical modeling and computer simulations in predicting the performance and optimization of the training load to maximize both performance gains and parasympathetic activity All this work demonstrates, through mathematical modeling, the relevance of HF spectral power of HRV as a non-invasive tool, easy to use in routine, to optimize the training load and predict the performance in swimming. Beyond the demonstration of a significant relationship between parasympathetic activity and performance, it was an evolution in phase of these two parameters that was highlightedST ETIENNE-Bib. électronique (422189901) / SudocSudocFranceF

Sex-related differences in endothelial function and blood viscosity in the elderly population

Elderly represents a growing population and cardiovascular diseases (CVD) is one of the leading causes of mortality in this population. Sex differences are involved in CVD with middle-aged males being at higher risk than females. After menopause, females are no longer protected by hormones and the role of sex on cardiovascular parameters involved in CVD, such as endothelial function and blood viscosity, is still unclear. The purpose of this study was to investigate the effect of sex on endothelial function, blood viscosity and CVD in elderly. Clinical investigation and blood analyses were performed on 182 (93 females and 89 males) elderly participants (mean age: 75.83 ± 1.22). Health status of participants were classified. Sex differences in endothelial function, blood viscosity, high density lipoprotein (HDL), hematocrit, and red blood cell (RBC) aggregation were assessed. CVD prevalence was higher in males (27.0%) than in females (5.4%) (p < 0.001). Females had higher vasoreactivity (p = 0.014) and HDL (p < 0.001) level than males. Blood viscosity was higher in males than in females at any shear rate (p < 0.001). Hematocrit was greater in males than in females (p < 0.001) while RBC aggregation did not differ between the two populations. To conclude, females have less CVD than age-matched males that might be due to their greater vascular function and lower blood viscosity

Assessing renal graft function in clinical trials: Can tests predicting glomerular filtration rate substitute for a reference method?

Assessing renal graft function in clinical trials: Can tests predicting glomerular filtration rate substitute for a reference method?BackgroundIn clinical trials, comparison of renal graft function needs a rigorous determination of glomerular filtration rate (GFR). Since reference methods to measure GFR cannot be easily implemented, a number of tests predicting GFR are usually used. However, little is known about their validity in renal transplant patients. We aimed to compare the performances of six GFR tests with inulin clearance in this population.MethodsFive hundred consecutive inulin clearances performed in 294 renal transplant recipients with stable renal function were retrospectively selected. For each of them, we computed six estimates: the 24-hour creatinine clearance, the Cockcroft-Gault, Walser, Jelliffe, Nankivell, and Levey formulas. Their respective performance was assessed by correlation (simple linear regression), accuracy (dispersion of true error), and agreement (Bland and Altman method).ResultsEach GFR test closely correlated with inulin clearance (P < 0.0001). Comparisons between pairs of GFR tests did not show any significant difference in accuracy between the Levey, Jelliffe, and Walser formulas. Conversely, each of these formulas demonstrated a significant lower dispersion (P < 0.005) than the others. Nevertheless, all GFR tests displayed considerable lack of agreement with limits of agreement over 40mL/min/1.73m2 apart. The proportion of predicted GFR differing from inulin clearance by ± 10mL/min/1.73m2, ranged from 34% for the Jelliffe formula to 53% for the Nankivell's one.ConclusionNone of these formulas seems to be able to safely substitute for inulin clearance. In clinical trials, renal graft function should be preferably assessed using a reference method of GFR measurement

Even a Previous Light-Active Physical Activity at Work Still Reduces Late Myocardial Infarction and Stroke in Retired Adults Aged>65 Years by 32%: The PROOF Cohort Study

Background: Work may contribute significantly to daily physical activity (PA) and sedentary behavior (SB). Physical inactivity and SB at work might be two major risk factors for premature morbidity. Therefore, the aim of this research was to describe self-reported past PA and SB at work and during leisure time within the PROOF cohort subjects, and to determine consequences of PA and SB on late health of these now retired workers.Material and Methods: The PROOF cohort study was used to prospectively allow assessment of the predictive value of PA and SB at work and during leisure time among a healthy retired French population, with regard to cardiovascular and cerebrovascular events. PA (MET-h/week) and SB (h/d) were assessed using the Population Physical Activity Questionnaire (POPAQ) and the modified Global Physical Activity Questionnaire (GPAQ). Odds ratios (ORs with 95% CIs) for cardiovascular and cerebrovascular events were associated with each level of PA at work: light (&lt;3 METs), moderate (3–5.9 METs), vigorous (≥6 METs) and were compared to SB at work.Results: Out of the 1011 65-year-old subjects initially included, the 15-year follow-up has been currently completed for 688 (68%) subjects; 89 deaths (all-cause mortality, 9%) and 91 fatal and non-fatal cardiovascular and cerebrovascular events (9%), were reported. An active work (light, moderate, or vigorous intensity) was associated with a 21% reduced risk of cardiovascular (myocardial infarction) and cerebrovascular events (stroke) (OR = 0.79, 95% CI: 0.32–0.91, p &lt; 0.02) compared to sedentary work. This relationship was already significant for light intensity work (32%; i.e., OR = 0.68, 95% CI: 0.31–0.87, p &lt; 0.02).Conclusion: There is strong causal evidence linking PA and SB at work with late cardiovascular and cerebrovascular disease. All in all, the risk for onset of myocardial infarction and stroke was lower among those who had a previous active work compared to those with previous sedentary work. Even previous light active work produced substantial health benefits.Clinical Trial Registration:www.ClinicalTrials.gov, identifier: NCT00759304

032: Thirty months outcomes after PCI of unprotected left main coronary artery according to the SYNTAX score

AimsTo assess middle term outcomes according to SYNTAX score and rates of delayed surgical/bleeding events after unprotected left main (LM) coronary artery (ULMCA) PCI in an unselected patients population.MethodsConsecutive patients treated by PCI for ULMCA were included among a single center 3508 PCI database within 36 months. Syntax scores were calculated, post discharge extracardiac surgery or hemorrhage were recorded during follow-up as clinical outcomes (Death, TVR, MACCE=cardiovascular death+MI+stroke+TLR).Results102 (3.6%) patients underwent PCI of the LM, including 21 protected LM. Among the 81 patients with PCI of ULMCA, mean age was 65±13, 27% had urgent PCI for AMI or cardiogenic shock, 61% had DES.SYNTAX score was 28±14 in mean and ≤22 in 30 (37%), 23 to 32 in 22 (27%) and ≥33 in 29 (36%) patients.At 30±11 months follow up (98% of the patients), death occurred in 24 patients (30%), TVR in 16 (20%) and MACCE in 35 (43%). Clinical events according to the SYNTAX score are shown in figure. No cardiovascular death occurred in patients with syntax ≤22. MACCE rates were significantly lower when DES were used (24% vs. 64%, p<0.05) and in case of non-urgent PCI (36% vs. 71%, p<0.05).During follow-up, 20 (25%) and 12 (15%) patients underwent unplanned extracardiac surgery and/or hemorrhage, leading to antiplatelet withdrawal in 31% of the cases.ConclusionsIn unselected patients treated by PCI of ULMCA with Syntax score ≤22, outcomes were found to be excellent with no cardiovascular death observed at 30 months. DES and non-urgent PCI were associated with a better prognosis. One patient out of three underwent unplanned extracardiac surgery or hemorrhage during follow up.Figure: 30-months outcomes according to SYNTAX scor

Electronic cigarettes and health with special focus on cardiovascular effects: position paper of the European Association of Preventive Cardiology (EAPC)

Background: Tobacco use is the single largest preventable risk factor for premature death of non-communicable diseases and the second leading cause of cardiovascular disease. In response to the harmful effects of tobacco smoking, the use of electronic cigarettes (e-cigarettes) has emerged and gained significant popularity over the past 15 years. E-cigarettes are promoted as safe alternatives for traditional tobacco smoking and are often suggested as a way to reduce or quit smoking. However, evidence suggests they are not harmless. Discussion: The rapid evolution of the e-cigarette market has outpaced the legislator’s regulatory capacity, leading to mixed regulations. The increasing use of e-cigarettes in adolescents and young individuals is of concern. While the long-term direct cardiovascular effects of e-cigarettes remain largely unknown, the existing evidence suggests that the e-cigarette should not be regarded as a cardiovascular safe product. The contribution of e-cigarette use to reducing conventional cigarette use and smoking cessation is complex, and the impact of e-cigarette use on long-term cessation lacks sufficient evidence. Conclusion: This position paper describes the evidence regarding the prevalence of e-cigarette smoking, uptake of e-cigarettes in the young, related legislations, cardiovascular effects of e-cigarettes and the impact of e-cigarettes on smoking cessation. Knowledge gaps in the field are also highlighted. The recommendations from the population science and public health section of the European Association of Preventive Cardiology are presented

Forward-central two-particle correlations in p-Pb collisions at root s(NN)=5.02 TeV

Two-particle angular correlations between trigger particles in the forward pseudorapidity range (2.5 2GeV/c. (C) 2015 CERN for the benefit of the ALICE Collaboration. Published by Elsevier B. V.Peer reviewe