Un modèle de cinétique d'évolution de populations de bulles dans un fluide à seuil

International audienceThe context of this study is to predict the swelling of bitumen drums in which radioactive salts are mixed (60 wt% of bitumen and 40 wt% of salts). Radioactivity generates uniform volume production of hydrogen by radiolysis of bitumen chains. The creation of gas occurs on very large time scales (more than a hundred years), hence the need to provide model in order to predict the swelling. It has been shown that bitumen is a yield stress fluid. Therefore this work proposes to study the influence of a continuous gas generation and a yield stress on the kinetic evolution of a bubble population. Usually, when a gas is dissolved beyond its solubility limit without yield stress or gas creation, one observes a nucleation-growth-ripening scenario (growth of large bubbles to the detriment of small ones). It selects a distribution of large bubbles over long times, independently of the initial distribution of nuclei. Our work shows that in some cases the gas creation competes with the ripening kinetics and the yield stress can make the bubble population bimodal during its evolution.Le contexte de cette étude est de décrire les processus physico-chimiques élémentaires de base conduisant au gonflement d’enrobés de bitume (suspensions de sels dans une matrice bitume) dans lequel sont conditionnés des sels de coprécipitation de radionucléides. La radioactivité génère une production volumique uniforme de dihydrogène par radiolyse des chaînes de bitume. Ce taux de création de gaz perdure sur des échelles de temps très grandes (plus de cent ans), bien que décroissant au cours du temps. L’étude scientifique vise à conforter les modèles actuels de prédiction du gonflement sous radiolyse des enrobés bitume. Il a été montré que les enrobés de bitume sont des fluides à seuil. Ces travaux proposent donc d'aborder l'influence d’une génération continue de gaz (appelée terme source dans la suite de cet article) et d’un seuil d’écoulement sur la cinétique d'évolution d'une population de bulles. Classiquement, pour un gaz dissous au delà de sa limite de solubilité et en l’absence de seuil et de terme source, on observe un scénario de germination-croissance-mûrissement (croissance des grosses bulles au détriment des petites) qui sélectionne aux temps longs une distribution de grosses bulles, indépendante de la distribution initiale de germes. Nos travaux montrent qu’il existe des régimes où le terme source entre en compétition avec la cinétique de mûrissement et où le seuil d’écoulement peut étaler ou rendre bidisperse la distribution de taille de bulles au cours de son évolution

Diaphragmatic Endometriosis-A Single-Center Retrospective Analysis of the Patients' Demographics, Symptomatology, and Long-Term Treatment Outcomes

Diaphragmatic endometriosis is rare and forms 0.67-4.7% of all endometriosis cases. Evidence regarding its optimal management is lacking. In this study, we retrospectively analyzed the patient characteristics and long-term treatment outcomes of diaphragmatic endometriosis patients. Over a 4-year period, 23 patients were diagnosed with diaphragmatic endometriosis. The majority of patients had coexisting deep pelvic endometriosis. Cyclic upper abdominal pain was reported by 60.9% of patients, while cyclic chest and shoulder pain were reported by 43.5% and 34.8% of patients, respectively. Most patients were treated with laparoscopic lesion ablation, while 21.1% were treated with minimally invasive excision. The mean follow-up time was 23.7 months. Long-lasting resolution of the chest, abdominal, and shoulder pain occurred in 50%, 35.7%, and 25% of patients, respectively. Nonetheless, 78.9% of patients reported major improvement in their symptoms postoperatively. Significantly higher rates of postoperative shoulder, abdominal, and chest pain were observed in patients who received postoperative hormonal therapy compared with those who did not. All patients treated expectantly remained stable. Therefore, we recommend treating diaphragmatic endometriosis only in symptomatic patients. The risk of incomplete surgery should be minimized by a multidisciplinary diagnostic and therapeutic approach with a careful assessment of the diaphragm and the thoracic cavity

ALMA-IMF VIII -- Combination of Interferometric Continuum Images with Single-Dish Surveys and Structural Analysis of Six Protoclusters

We present the combination of ALMA-IMF and single-dish continuum images from the Mustang-2 Galactic Plane Survey (MGPS90) at 3 millimeters and the Bolocam Galactic Plane Survey (BGPS) at 1 millimeter. Six and ten out of the fiffteen ALMA-IMF fields are combined with MGPS90 and BGPS, respectively. The combination is made via the feathering technique. We used the dendrogram algorithm throughout the combined images, and performed further analysis in the six fields with combination in both bands (G012.80, W43-MM1, W43-MM2, W43-MM3, W51-E, W51-IRS2). In these fields, we calculated spectral index maps and used them to separate regions dominated by dust or free-free emission, and then performed further structural analysis. We report the basic physical parameters of the dust-dominated (column densities, masses) and ionized (emission measures, hydrogen ionization photon rates) structures. We also searched for multi-scale relations in the dust-dominated structures across the analyzed fields, finding that the fraction of mass in dendrogram leaves (which we label as "Leaf Mass Eficiency", LME) as a function of molecular gas column density follows a similar trend: a rapid, exponential-like growth, with maximum values approaching 100% in most cases. The observed behaviour of the LME with gas column is tentatively interpreted as an indicator of large star formation activity within the ALMA-IMF protoclusters. W51-E and G012.80 stand out as cases with comparatively large and reduced potential for further star formation, respectively.Comment: Accepted to The Astrophysical Journal Supplemen

Molecular Evolution of the Two-Component System BvgAS Involved in Virulence Regulation in Bordetella

The whooping cough agent Bordetella pertussis is closely related to Bordetella bronchiseptica, which is responsible for chronic respiratory infections in various mammals and is occasionally found in humans, and to Bordetella parapertussis, one lineage of which causes mild whooping cough in humans and the other ovine respiratory infections. All three species produce similar sets of virulence factors that are co-regulated by the two-component system BvgAS. We characterized the molecular diversity of BvgAS in Bordetella by sequencing the two genes from a large number of diverse isolates. The response regulator BvgA is virtually invariant, indicating strong functional constraints. In contrast, the multi-domain sensor kinase BvgS has evolved into two different types. The pertussis type is found in B. pertussis and in a lineage of essentially human-associated B. bronchiseptica, while the bronchiseptica type is associated with the majority of B. bronchiseptica and both ovine and human B. parapertussis. BvgS is monomorphic in B. pertussis, suggesting optimal adaptation or a recent population bottleneck. The degree of diversity of the bronchiseptica type BvgS is markedly different between domains, indicating distinct evolutionary pressures. Thus, absolute conservation of the putative solute-binding cavities of the two periplasmic Venus Fly Trap (VFT) domains suggests that common signals are perceived in all three species, while the external surfaces of these domains vary more extensively. Co-evolution of the surfaces of the two VFT domains in each type and domain swapping experiments indicate that signal transduction in the periplasmic region may be type-specific. The two distinct evolutionary solutions for BvgS confirm that B. pertussis has emerged from a specific B. bronchiseptica lineage. The invariant regions of BvgS point to essential parts for its molecular mechanism, while the variable regions may indicate adaptations to different lifestyles. The repertoire of BvgS sequences will pave the way for functional analyses of this prototypic system

Detection of small RNAs in Bordetella pertussis and identification of a novel repeated genetic element

Background: Small bacterial RNAs (sRNAs) have been shown to participate in the regulation of gene expression and have been identified in numerous prokaryotic species. Some of them are involved in the regulation of virulence in pathogenic bacteria. So far, little is known about sRNAs in Bordetella, and only very few sRNAs have been identified in the genome of Bordetella pertussis, the causative agent of whooping cough. Results: An in silico approach was used to predict sRNAs genes in intergenic regions of the B. pertussis genome. The genome sequences of B. pertussis, Bordetella parapertussis, Bordetella bronchiseptica and Bordetella avium were compared using a Blast, and significant hits were analyzed using RNAz. Twenty-three candidate regions were obtained, including regions encoding the already documented 6S RNA, and the GCVT and FMN riboswitches. The existence of sRNAs was verified by Northern blot analyses, and transcripts were detected for 13 out of the 20 additional candidates. These new sRNAs were named Bordetella pertussis RNAs, bpr. The expression of 4 of them differed between the early, exponential and late growth phases, and one of them, bprJ2, was found to be under the control of BvgA/BvgS two-component regulatory system of Bordetella virulence. A phylogenetic study of the bprJ sequence revealed a novel, so far undocumented repeat of ~90 bp, found in numerous copies in the Bordetella genomes and in that of other Betaproteobacteria. This repeat exhibits certain features of mobil

Photography-based taxonomy is inadequate, unnecessary, and potentially harmful for biological sciences

The question whether taxonomic descriptions naming new animal species without type specimen(s) deposited in collections should be accepted for publication by scientific journals and allowed by the Code has already been discussed in Zootaxa (Dubois & Nemésio 2007; Donegan 2008, 2009; Nemésio 2009a–b; Dubois 2009; Gentile & Snell 2009; Minelli 2009; Cianferoni & Bartolozzi 2016; Amorim et al. 2016). This question was again raised in a letter supported by 35 signatories published in the journal Nature (Pape et al. 2016) on 15 September 2016. On 25 September 2016, the following rebuttal (strictly limited to 300 words as per the editorial rules of Nature) was submitted to Nature, which on 18 October 2016 refused to publish it. As we think this problem is a very important one for zoological taxonomy, this text is published here exactly as submitted to Nature, followed by the list of the 493 taxonomists and collection-based researchers who signed it in the short time span from 20 September to 6 October 2016