Flux thermique et coefficients de transfert global et partiel d'un échangeur à ailettes spiralées en graphite

La technique d'évaporation présentée dans ce travail consiste à faire ruisseler un liquide à évaporer à la surface d'ailettes enroulées en spirale autour d'un tube vertical, chauffé intérieurement par un fluide caloporteur. Le tube et les ailettes sont usinés dans un monobloc massif en graphite imprégné. Compte tenu de la grande complexité de la géométrie de cet échangeur et de l'écoulement sur ses ailettes, la détermination du coefficient de transfert thermique par convection externe est difficile à obtenir par un calcul direct. Il est déterminé ici par voie indirecte en suivant la méthode de Wilson basée sur deux étapes : une expérimentale et l'autre théorique. On détermine dans cet article la quantité de chaleur échangée et la conductance globale au transfert thermique de cet échangeur/évaporateur lors de l'échauffement. On détermine également les différentes résistances partielles ainsi que le coefficient de convection entre la paroi externe de l'ailette et le film de la solution à chauffer. La démarche proposée dans cet article a permis de valider la méthode indirecte

Molecular epidemiology of coxsackievirus type B1

International audienceCoxsackievirus type B1 (CVB1) has emerged globally as the predominant enterovirus serotype and is associated with epidemics of meningitis and chronic diseases. In this report, the phylogeny of CVB1 was studied based on the VP1 sequences of 11 North African isolates and 81 published sequences. All CVB1 isolates segregated into four distinct genogroups and 10 genotypes. Most of the identified genotypes of circulating CVB1 strains appear to have a strict geographical specificity. The North African strains were of a single genotype and probably evolved distinctly. Using a relaxed molecular clock model and three different population models (constant population, exponential growth and Bayesian skyline demographic models) in coalescent analysis using the BEAST program, the substitution rate in CVB1 varied between 6.95 x 10(-3) and 7.37 x 10(-3) substitutions/site/year in the VP1 region. This study permits better identification of circulating CVB1, which has become one of the most predominant enterovirus serotypes in humans

Metagenomic analysis identifies human adenovirus 31 in children with acute flaccid paralysis in Tunisia

International audienceA variety of viruses can cause acute flaccid paralysis (AFP). However, the causative agent, sometimes, remains undetermined. Metagenomics helps in identifying viruses not diagnosed by conventional methods. Stool samples from AFP (n = 104) and non-AFP (n = 114) cases that tested enterovirus-negative by WHO standard methods were investigated. A metagenomics approach, first used on five pools of four samples each, revealed the presence of adenovirus sequences. Amplification in A549 cells and full-genome sequencing were used for complete virus identification and for designing a PCR assay to screen individual related samples. Metagenomic analysis showed that adenovirus sequences that were closely to the A31 and A61 genotypes were the most abundant. Two out of the corresponding 20 individual samples were found positive by PCR, and isolates were obtained in cell culture. Phylogenetic analysis based on complete genome sequences showed that the viruses belong to HAdV-A31 genotype (98-100% nucleotide sequence identity). PCR analysis of stool samples from all AFP and non-AFP cases revealed that a larger proportion of the positive samples were from AFP cases (17.3%) than from non-AFP cases (2.4%). These results open the way to studies aiming to test a possible role of HAdV-A31 in the pathogenesis of AFP

Circulation and Molecular Epidemiology of Enteroviruses in Paralyzed, Immunodeficient and Healthy Individuals in Tunisia, a Country with a Polio-Free Status for Decades

This report is an overview of enterovirus (EV) detection in Tunisian polio-suspected paralytic cases (acute flaccid paralysis (AFP) cases), healthy contacts and patients with primary immunodeficiencies (PID) during an 11-year period. A total of 2735 clinical samples were analyzed for EV isolation and type identification, according to the recommended protocols of the World Health Organization. Three poliovirus (PV) serotypes and 28 different nonpolio enteroviruses (NPEVs) were detected. The NPEV detection rate was 4.3%, 2.8% and 12.4% in AFP cases, healthy contacts and PID patients, respectively. The predominant species was EV-B, and the circulation of viruses from species EV-A was noted since 2011. All PVs detected were of Sabin origin. The PV detection rate was higher in PID patients compared to AFP cases and contacts (6.8%, 1.5% and 1.3% respectively). PV2 was not detected since 2015. Using nucleotide sequencing of the entire VP1 region, 61 strains were characterized as Sabin-like. Among them, six strains of types 1 and 3 PV were identified as pre-vaccine-derived polioviruses (VDPVs). Five type 2 PV, four strains belonging to type 1 PV and two strains belonging to type 3 PV, were classified as iVDPVs. The data presented provide a comprehensive picture of EVs circulating in Tunisia over an 11-year period, reveal changes in their epidemiology as compared to previous studies and highlight the need to set up a warning system to avoid unnoticed PVs

Circulation and Molecular Epidemiology of Enteroviruses in Paralyzed, Immunodeficient and Healthy Individuals in Tunisia, a Country with a Polio-Free Status for Decades

This report is an overview of enterovirus (EV) detection in Tunisian polio-suspected paralytic cases (acute flaccid paralysis (AFP) cases), healthy contacts and patients with primary immunodeficiencies (PID) during an 11-year period. A total of 2735 clinical samples were analyzed for EV isolation and type identification, according to the recommended protocols of the World Health Organization. Three poliovirus (PV) serotypes and 28 different nonpolio enteroviruses (NPEVs) were detected. The NPEV detection rate was 4.3%, 2.8% and 12.4% in AFP cases, healthy contacts and PID patients, respectively. The predominant species was EV-B, and the circulation of viruses from species EV-A was noted since 2011. All PVs detected were of Sabin origin. The PV detection rate was higher in PID patients compared to AFP cases and contacts (6.8%, 1.5% and 1.3% respectively). PV2 was not detected since 2015. Using nucleotide sequencing of the entire VP1 region, 61 strains were characterized as Sabin-like. Among them, six strains of types 1 and 3 PV were identified as pre-vaccine-derived polioviruses (VDPVs). Five type 2 PV, four strains belonging to type 1 PV and two strains belonging to type 3 PV, were classified as iVDPVs. The data presented provide a comprehensive picture of EVs circulating in Tunisia over an 11-year period, reveal changes in their epidemiology as compared to previous studies and highlight the need to set up a warning system to avoid unnoticed PVs

First whole genome sequences and phylogenetic analysis of SARS-CoV-2 virus isolates during COVID-19 outbreak in Tunisia, North Africa.

International audienceFull genomes sequences of six Tunisian SARS-CoV-2 strains were obtained from imported and locally transmission cases during the COVID-19 outbreak. Reported sequences were non-identical with 0.1% nucleotide divergence rate and clustered into 6 different clades with worldwide sequences. SNPs results favor the distribution of the reported Tunisian sequences into 3 major genotypes. These results indicate multiple introductions of the virus in Tunisia and add new genomic data on SARS-CoV-2 at the international level

Whole genome sequencing and phylogenetic analysis of six SARS-CoV-2 strains isolated during COVID-19 pandemic in Tunisia, North Africa

International audienceBackground: In Tunisia a first SARS-CoV-2 confirmed case was reported in March 03, 2020. Since then, an increase of cases number was observed from either imported or local cases. The aim of this preliminary study was to better understand the molecular epidemiology and genetic variability of SARS-CoV-2 viruses circulating in Tunisia and worldwide. Methods: Whole genome sequencing was performed using NGS approach on six SARS. CoV-2 highly positive samples detected during the early phase of the outbreak. Results: Full genomes sequences of six Tunisian SARS-CoV-2 strains were obtained from imported and locally transmission cases during the COVID-19 outbreak. Reported sequences were non-identical with 0.1% nucleotide divergence rate and clustered into 6 different clades with worldwide sequences. SNPs results favor the distribution of the reported Tunisian sequences into 3 major genotypes. These SNP mutations are critical for diagnosis and vaccine development. Conclusions: These results indicate multiple introductions of the virus in Tunisia and add new genomic data on SARS-CoV-2 at the international level