Permeability of a bubble assembly: From the very dry to the wet limit

We measure the permeability of a fluidized bed of monodispersed bubbles with soap solution characteristic of mobile and non-mobile interfaces. These experimental data extend the permeability curves previously published for foam in the dry limit. In the wet limit, these data join the permeability curves of a hard sphere suspension at porosity equal to 0.4 and 0.6 in the cases of mobile and non-mobile interfaces respectively. We show that the model of permeability proposed by Kozeny and Carman and originally validated for packed beds of spheres (with porosity around 0.4) can be successfully applied with no adjustable parameters to liquid fractions from 0.001 up to 0.85 for systems made of monodisperse and deformable entities with non-mobile interfaces

Effect of oral calcium carbonate on aortic calcification in apolipoprotein E-deficient (apoE−/−) mice with chronic renal failure

Background. In chronic kidney disease (CKD) patients, the intake of calcium-based phosphate binders is associated with a marked progression of coronary artery and aortic calcification, in contrast to patients receiving calcium-free phosphate binders. The aim of this study was to reexamine the role of calcium carbonate in vascular calcification and to analyse its effect on aortic calcification-related gene expression in chronic renal failure (CRF). Methods. Mice deficient in apolipoprotein E underwent either sham operation or subtotal nephrectomy to create CRF. They were then randomly assigned to one of the three following groups: a control non-CRF group and a CRF group fed on standard diet, and a CRF group fed on calcium carbonate enriched diet, for a period of 8 weeks. Aortic atherosclerotic plaque and calcification were evaluated using quantitative morphologic image processing. Aortic gene and protein expression was examined using immunohistochemistry and Q-PCR methods. Results. Calcium carbonate supplementation was effective in decreasing serum phosphorus but was associated with a higher serum calcium concentration. Compared with standard diet, calcium carbonate enriched diet unexpectedly induced a significant decrease of both plaque (p < 0.05) and non-plaque-associated calcification surface (p < 0.05) in CRF mice. It also increased osteopontin (OPN) protein expression in atherosclerotic lesion areas of aortic root. There was also a numerical increase in OPN and osteoprotegerin gene expression in total thoracic aorta but the difference did not reach the level of significance. Finally, calcium carbonate did not change the severity of atherosclerotic lesions. Conclusion. In this experimental model of CRF, calcium carbonate supplementation did not accelerate but instead decreased vascular calcification. If our observation can be extrapolated to humans, it appears to question the contention that calcium carbonate supplementation, at least when given in moderate amounts, necessarily enhances vascular calcification. It is also compatible with the hypothesis of a preponderant role of phosphorus over that of calcium in promoting vascular calcification in CR

Natalizumab treatment shows low cumulative probabilities of confirmed disability worsening to EDSS milestones in the long-term setting.

Abstract Background Though the Expanded Disability Status Scale (EDSS) is commonly used to assess disability level in relapsing-remitting multiple sclerosis (RRMS), the criteria defining disability progression are used for patients with a wide range of baseline levels of disability in relatively short-term trials. As a result, not all EDSS changes carry the same weight in terms of future disability, and treatment benefits such as decreased risk of reaching particular disability milestones may not be reliably captured. The objectives of this analysis are to assess the probability of confirmed disability worsening to specific EDSS milestones (i.e., EDSS scores ≥3.0, ≥4.0, or ≥6.0) at 288 weeks in the Tysabri Observational Program (TOP) and to examine the impact of relapses occurring during natalizumab therapy in TOP patients who had received natalizumab for ≥24 months. Methods TOP is an ongoing, open-label, observational, prospective study of patients with RRMS in clinical practice. Enrolled patients were naive to natalizumab at treatment initiation or had received ≤3 doses at the time of enrollment. Intravenous natalizumab (300 mg) infusions were given every 4 weeks, and the EDSS was assessed at baseline and every 24 weeks during treatment. Results Of the 4161 patients enrolled in TOP with follow-up of at least 24 months, 3253 patients with available baseline EDSS scores had continued natalizumab treatment and 908 had discontinued (5.4% due to a reported lack of efficacy and 16.4% for other reasons) at the 24-month time point. Those who discontinued due to lack of efficacy had higher baseline EDSS scores (median 4.5 vs. 3.5), higher on-treatment relapse rates (0.82 vs. 0.23), and higher cumulative probabilities of EDSS worsening (16% vs. 9%) at 24 months than those completing therapy. Among 24-month completers, after approximately 5.5 years of natalizumab treatment, the cumulative probabilities of confirmed EDSS worsening by 1.0 and 2.0 points were 18.5% and 7.9%, respectively (24-week confirmation), and 13.5% and 5.3%, respectively (48-week confirmation). The risks of 24- and 48-week confirmed EDSS worsening were significantly higher in patients with on-treatment relapses than in those without relapses. An analysis of time to specific EDSS milestones showed that the probabilities of 48-week confirmed transition from EDSS scores of 0.0–2.0 to ≥3.0, 2.0–3.0 to ≥4.0, and 4.0–5.0 to ≥6.0 at week 288 in TOP were 11.1%, 11.8%, and 9.5%, respectively, with lower probabilities observed among patients without on-treatment relapses (8.1%, 8.4%, and 5.7%, respectively). Conclusions In TOP patients with a median (range) baseline EDSS score of 3.5 (0.0–9.5) who completed 24 months of natalizumab treatment, the rate of 48-week confirmed disability worsening events was below 15%; after approximately 5.5 years of natalizumab treatment, 86.5% and 94.7% of patients did not have EDSS score increases of ≥1.0 or ≥2.0 points, respectively. The presence of relapses was associated with higher rates of overall disability worsening. These results were confirmed by assessing transition to EDSS milestones. Lower rates of overall 48-week confirmed EDSS worsening and of transitioning from EDSS score 4.0–5.0 to ≥6.0 in the absence of relapses suggest that relapses remain a significant driver of disability worsening and that on-treatment relapses in natalizumab-treated patients are of prognostic importance

Early liver transplantation for severe alcohol-related hepatitis not responding to medical treatment: a prospective controlled study

peer reviewedBackground: Early liver transplantation for severe alcohol-related hepatitis is an emerging treatment option. We aimed to assess the risk of alcohol relapse 2 years after early liver transplantation for alcohol-related hepatitis compared with liver transplantation for alcohol-related cirrhosis after at least 6 months of abstinence. Methods: We conducted a multicentre, non-randomised, non-inferiority, controlled study in 19 French and Belgian hospitals. All participants were aged 18 years or older. There were three groups of patients recruited prospectively: patients with severe alcohol-related hepatitis who did not respond to medical treatment and were eligible for early liver transplantation according to a new selection scoring system based on social and addiction items that can be quantified in points (early transplantation group); patients with alcohol-related cirrhosis listed for liver transplantation after at least 6 months of abstinence (standard transplantation group); patients with severe alcohol-related hepatitis not responding to medical treatment not eligible for early liver transplantation according to the selection score (not eligible for early transplantation group), this group did not enter any further liver transplantation processes. We also defined a historical control group of patients with severe alcohol-related hepatitis unresponsive to medical therapy and non-transplanted. The primary outcome was the non-inferiority of 2-year rate of alcohol relapse after transplantation in the early transplantation group compared with the standard transplantation group using the alcohol timeline follow back (TLFB) method and a prespecified non-inferiority margin of 10%. Secondary outcomes were the pattern of alcohol relapse, 2-year survival rate post-transplant in the early transplantation group compared with the standard transplantation group, and 2-year overall survival in the early transplantation group compared with patients in the not eligible for early transplantation group and historical controls. This trial is registered with ClinicalTrials.gov, NCT01756794. Findings: Between Dec 5, 2012, and June 30, 2016, we included 149 patients with severe alcohol-related hepatitis: 102 in the early transplantation group and 47 in the not eligible for early transplantation group. 129 patients were included in the standard transplantation group. 68 patients in the early transplantation group and 93 patients in the standard transplantation group received a liver transplant. 23 (34%) patients relapsed in the early transplantation group, and 23 (25%) patients relapsed in the standard transplantation group; therefore, the non-inferiority of early transplantation versus standard transplantation was not demonstrated (absolute difference 9·1% [95% CI –∞ to 21·1]; p=0·45). The 2-year rate of high alcohol intake was greater in the early transplantation group than the standard transplantation group (absolute difference 16·7% [95% CI 5·8–27·6]) The time spent drinking alcohol was not different between the two groups (standardised difference 0·24 [95% CI −0·07 to 0·55]), but the time spent drinking a large quantity of alcohol was higher in the early transplantation group than the standard transplantation group (standardised difference 0·50 [95% CI 0·17–0·82]). 2-year post-transplant survival was similar between the early transplantation group and the standard transplantation group (hazard ratio [HR] 0·87 [95% CI 0·33–2·26]); 2-year overall survival was higher in the early transplantation group than the not eligible for early transplantation group and historical controls (HR 0·27 [95% CI 0·16–0·47] and 0·21 [0·13–0·32]). Interpretation: We cannot conclude non-inferiority in terms of rate of alcohol relapse post-transplant between early liver transplantation and standard transplantation. High alcohol intake is more frequent after early liver transplantation. This prospective controlled study confirms the important survival benefit related to early liver transplantation for severe alcohol-related hepatitis; and this study provides objective data on survival and alcohol relapse to tailor the management of patients with severe alcohol-related hepatitis. Funding: The present study has been granted by the French Ministry of Health—Programme Hospitalier de Recherche Clinique 2010

Comment les docteurs deviennent-ils directeurs de thèse ?

Dans cet article, nous étudions l’accès des docteurs à la direction de thèse. Le premier apport est d’abord méthodologique. Il montre comment on peut exploiter un fichier administratif, le fichier des thèses soutenues en France de 1970 à 2002, relativement pauvre en informations individuelles, mais quasi exhaustif pour reconstituer des carrières. Il est alors possible de calculer les temps d’attente entre l’obtention d’un doctorat et la soutenance de la première thèse dirigée. Le second apport est théorique et empirique. Nous souhaitons revenir sur la question de la force des liens sociaux et nuancer l’idée qui s’est imposée avec les travaux de Granovetter selon laquelle elle tient surtout au contenu informationnel diffusé par le réseau. Les réseaux comptent dans le monde académique parce qu’ils engendrent aussi du soutien (en particulier le soutien des directeurs de thèse pour leur docteur), lequel prend une forme beaucoup plus exclusive que la circulation de l’information.Pour tester l’importance des contacts, nous mettons en relation les phénomènes de recrutement avec le réseau constitué par les mobilités des directeurs de thèse. En changeant d’université, les directeurs étendent pour un temps leur nombre de contacts et peuvent en faire profiter leurs docteurs ou ceux de leurs collègues. Nous estimons l’impact de ce réseau à l’aide des calculs des Mantel Haenszel odds ratios d’une part et de modèles semi-paramétriques de Cox d’autre part. Nous utilisons la technique des « effets fixes » pour contrôler l’hétérogénéité inobservée. Ces modèles conduisent tout d’abord à souligner l’influence très importante des conditions locales de compétition sur la reproduction de la population académique, notamment lors des processus de recrutement sous-jacents à nos observations. Nous confirmons par nos données le phénomène bien connu du « localisme académique », qui traduit plus une préférence pour la proximité institutionnelle que pour la proximité géographique. Nous montrons aussi l’existence d’un phénomène de files d’attente locales, avec des aînés faisant de l’ombre à leurs cadets. Mais les contacts ne jouent pas seulement au niveau local. Ils fonctionnent également à distance pour favoriser le recrutement de candidats extérieurs liés par des intermédiaires, en particulier les docteurs d’un directeur de thèse qui vient de quitter le département. Dans un univers très compétitif, les relations ne se transforment toutefois pas systématiquement en appuis dans le processus de recrutement. Elles ne le deviennent que dans la mesure où celles-ci sont disponibles, c’est-à-dire où celles-ci n’ont pas à défendre leurs propres intérêts et à soutenir leurs propres candidats.In this paper we study how doctors become PhD advisors. The first contribution of this paper is methodological. We show how we can use administrative data, the French PhD database (1970-2002), that is relatively poor and lacks of individual information, but that is quasi-exhaustive and can help in order to reconstruct academic careers. It is therefore possible to calculate the time separating a researcher’s own PhD defense and that of his first doctoral student. The second contribution is theoretical and empirical. We would like to return to the question of the strength of social ties and to nuance Granovetter’s conclusion concerning the fact that this strength is due to information diffused through the network. Networks count in academic world because they generate also some support (especially support of the adviser for his PhD student). This support is much more exclusive than just the spread of information.In order to test the importance of contacts, we link the recruitment process with the mobility network of advisors. When they change universities, advisors increase for a while their number of contacts and make them profitable for their PhD students or those of their colleagues. We estimate the impact of network with Mantel Haenszel odds ratios in the one hand and Cox survival model in the other hand. We use the fixed effects techniques in order to control for unobserved heterogeneity. Those models show that the reproduction of faculty highly depends on the local conditions of competition, especially during the recruitment process underlying our observations. We confirm by our research the importance in France of an academic inbreeding due more to a preference for institutional proximity than to a preference for geographic proximity. We show also the importance of informal queuing lines, with the eldest shading the chance of the youngest. But contacts do not solely have a role locally but also at distance, through networks. Outside candidates linked to the recruiting department by intermediates are more likely than other outside candidates to be hired and to have an academic career. We show however that in this very competitive universe, contacts do not act systematically as supporters. They do so if they are available, if they do not have their own interest to defend and their own candidates to support

Annexes électroniques de l'article « comment les docteurs deviennent-ils directeurs de thèse ? »

Annexe 1. Qualité des données La comparaison avec les données statistiques du Ministère de l’Éducation Nationale semble plutôt de bon augure (Graphique A1). Le nombre de thèses recensées est très proche dans les deux sources. L’écart absolu moyen entre les deux sources entre 1981 et 2000 est faible : 6%. En outre, il y a généralement plus de thèses recensées dans notre source que dans les données du ministère, ce qui suggère que la sous-évaluation n’est pas massive dans nos données. Nos donné..

Parametric Polymorphism for Typed Prolog and λProlog

Typed Prolog and λProlog are logic programming languages with a strict typing discipline which is based on simple types with variables. Experiments show that this discipline does not handle properly common logic programming practices used in Prolog. For instance, the usual transformation for computing the Clark completion of a Prolog program does not work well with some typed programs. We observe that the so-called head-condition is at the heart of these problems, and conclude that it should be enforced. We propose a second-order scheme which is compatible with usual practices. It allows quantifying types and terms, passing type and term parameters to goals and terms, and to express type guards for selecting goals. We give its syntax and deduction rules, and propose a solution to keep the concrete notation of programs close to the usual one

Recirculation model for liquid flow in foam channels

International audienceAlthough extensively studied in the past, drainage of aqueous foams still offers major unaddressed issues. Among them, the behaviour of foam films during drainage has great significance as the thickness of the films is known to control the Ostwald ripening in foams, which in turn impacts liquid drainage. We propose a model relating the films' behavior to the liquid flow in foam channels. It is assumed that Marangoni driven recirculation counter flows take place in the transitional region between the foam channel and the adjoining films, and the Gibbs elasticity is therefore introduced as a relevant parameter. The velocity of these counter flows is found to be proportional to the liquid velocity in the channel. The resulting channel permeability is determined and it is shown that Marangoni stresses do not contribute to rigidify the channel's surfaces, in strong contrast with the drainage of horizontal thin liquid films. New experimental data are provided and support the proposed model

Ripening of a draining foam bubble

International audienceA forced Ostwald ripening experiment is performed on a single foam bubble. The bubble size is followed as the system is wetted with a constant liquid flow rate delivered from one of the bubble Plateau borders. Obtained ripening velocities cannot be described with a model based on a constant film thickness assumption. Within these well-controlled experimental conditions, the film thickness is measured and found to depend on the imposed liquid flow rate. It is shown that the bubble growth rate is well predicted as the films thickness evolution is explicitly introduced in the ripening model. Finally, it is suggested that existing results for the coarsening of draining foams could be understood following the approach validated on the bubble scale