Preoperative magnetic resonance imaging of anal fistulas with scrotal extension: a retrospective study

IntroductionThis study aimed to elucidate the magnetic resonance (MR) characteristics of anal fistulas extending to the scrotum, and the applicable rules, and to correlate MR features with surgical findings.MethodsWe conducted a retrospective study in 150 consecutive patients with anal fistulas extending into the scrotum, who were diagnosed and underwent surgery at University Medical Center Ho Chi Minh City between January 2017 and April 2022. MR findings were evaluated and compared with surgical findings using Cohens kappa coefficient (k) with a 95% confidence interval.Results150 patients (mean age 37.6 ± 10.9 years) with 166 fistulas, including 150 anal fistulas with scrotal extension. Most fistulas were low transsphincteric (80.0%, 120/150 patients). There was a strong agreement for primary tract classification and detecting the location of internal openings between MRI and surgical findings with k = 0.83 (0.780.87) and k = 0.89 (0.85 0.93) (p<0.001), respectively. There is a significant correlation between the location of internal openings and the type of fistula (p<0.05). Low transsphincteric fistulas were predominant in the anterior group (103/122 patients vs. 10/19 patients), while in the posterior group, it was more common in the high transsphincteric fistulas (7/19 patients vs. 14/122 patients), and the intersphincteric fistulas (1/19 patients vs. 5/122 patients); and the suprasphincteric fistulas were only seen in the posterior group (1 patient).ConclusionAnal fistulas with scrotal extension are exceptions to Goodsalls rule. Albeit long-tract fistulas, most are low transsphincteric and have anterior internal openings

Spatiotemporal evolution of SARS-CoV-2 Alpha and Delta variants during large nationwide outbreak of COVID-19, Vietnam, 2021

We analyzed 1,303 SARS-CoV-2 whole-genome sequences from Vietnam, and found the Alpha and Delta variants were responsible for a large nationwide outbreak of COVID-19 in 2021. The Delta variant was confined to the AY.57 lineage and caused >1.7 million infections and >32,000 deaths. Viral transmission was strongly affected by nonpharmaceutical interventions

Mousses acoustiques à distributions de tailles de pores et interconnexions contrôlées: Relations structures, propriétés, fabrication

Foam materials are frequently used in engineering applications, due to their absorption and sound insulation properties. At the same time, the evolution of CO2 emission goals, together with new standards for acoustic, thermal, and fire resistance performance, calls for further developments that seek to reduce the impact of acoustic treatments---while maintaining, or even improving, global performance. Fine particles are usually introduced during the foaming process to improve fire resistance. By disrupting the nucleation sites, this procedure leads to disordered microstructures where cells of very different sizes coexist locally. This thesis work deals with the construction and experimental validation of a computational multi-scale-informed framework for modeling the acoustic behavior of polydisperse foams. The main objective is to model the relationships between the local foam geometry and the acoustic behavior exhibited at macroscale, with a view towards devising foam manufacturing conditions under acoustic performance targets. Here, we restrict our attention to the case of foams which present strong local heterogeneities in terms of pore sizes and therefore cannot be described by a deterministic unit cell. Advanced imaging techniques (namely, axial X-ray microtomography and scanning electron microscopy) are first deployed to identify relevant morphological characteristics on the studied microstructures. The geometrical properties thus obtained are then used in order to reconstruct spatial partitions consistent with the observations. The viscous permeability, which is a key parameter for the determination of acoustic properties, is estimated through "Pore-Network" simulations. The numerical predictions show that the permeability of a foam is strongly influenced, not only by the presence of membranes, but also by the variation of pore sizes. The effect of membrane thickness on viscous parameters (i.e., the viscous characteristic length and the tortuosity) describing the asymptotic behavior at high frequencies is also thoroughly studied. For the calculation of the viscous characteristic length, the results show that the effect of thin-membrane thickness can equivalently be modeled by virtual membranes without thickness. Finally, the acoustic properties of a real foam sample presenting a wide pore size distribution are modeled. Good agreement with experimental data obtained from an impedance tube is observed, which supports the relevance of the proposed approach.Les mousses sont utilisées fréquemment notamment en raison de leurs propriétés d'absorption et d'isolation sonore. Les exigences accrues en matière de réductions d'émissions de CO2 combinées à des exigences de performances acoustiques, thermiques, et de tenue au feu impliquent un effort significatif tourné vers l'allègement des traitements acoustiques---à performances égales ou supérieures. L'introduction de particules fines lors du processus de moussage, réalisée afin d’améliorer la tenue au feu, perturbe les sites de nucléation, ce qui conduit à la production de microstructures désordonnées où coexistent localement des cellules de tailles très contrastées. Ce travail de thèse traite de la construction d'outils numériques pour la modélisation du comportement acoustique de mousses polydisperses à partir d’une démarche multi-échelle et multi-physique. L'objectif principal est de pouvoir développer des relations entre la géométrie locale et le macro-comportement acoustique, afin de pouvoir guider la fabrication de mousses dans le but d'optimiser leurs performances acoustiques. Nous nous intéressons plus particulièrement au cas de mousses qui, présentant une forte hétérogénéité locale de tailles de pores, ne peuvent être décrites par une cellule périodique idéalisée (modèle déterministe). Des techniques d'imagerie avancées (microtomographie axiale à rayons-X et microscopie électronique à balayage) sont utilisées, dans un premier temps, pour identifier les caractéristiques morphologiques des microstructures étudiées. Les caractéristiques géométriques obtenues sont ensuite modélisées afin de reconstruire des partitions spatiales proches de celles mesurées. La perméabilité visqueuse, paramètre clé au regard de la détermination des propriétés acoustiques, est estimée par une simulation de type "pore-network". Nous quantifions, au travers de telles simulations, que la perméabilité d'une mousse est fortement influencée, non seulement par la présence des membranes, mais aussi par la variation de la taille des pores. L'effet de l'épaisseur de membrane sur les paramètres visqueux (longueur caractéristique visqueuse et tortuosité) décrivant le comportement asymptotique haute fréquence est, de plus, finement étudié. Les résultats obtenus montrent, en particulier, qu'il est possible de modéliser l'effet de l'épaisseur de membranes minces par des membranes virtuelles sans épaisseur pour le calcul de la longueur caractéristique visqueuse. Enfin, les propriétés acoustiques d'un échantillon réel de mousse ayant une distribution étendue de tailles de pores sont modélisées. Une bonne concordance avec les données expérimentales obtenues à partir d'un tube d'impédance confirme la validité de la méthode proposée

Mousses acoustiques à distributions de tailles de pores et interconnexions contrôlées : relations structures, propriétés, fabrication

Les mousses sont utilisées fréquemment notamment en raison de leurs propriétés d'absorption et d'isolation sonore. Les exigences accrues en matière de réductions d'émissions de CO2 combinées à des exigences de performances acoustiques, thermiques, et de tenue au feu impliquent un effort significatif tourné vers l'allègement des traitements acoustiques---à performances égales ou supérieures. L'introduction de particules fines lors du processus de moussage, réalisée afin d’améliorer la tenue au feu, perturbe les sites de nucléation, ce qui conduit à la production de microstructures désordonnées où coexistent localement des cellules de tailles très contrastées. Ce travail de thèse traite de la construction d'outils numériques pour la modélisation du comportement acoustique de mousses polydisperses à partir d’une démarche multi-échelle et multi-physique. L'objectif principal est de pouvoir développer des relations entre la géométrie locale et le macro-comportement acoustique, afin de pouvoir guider la fabrication de mousses dans le but d'optimiser leurs performances acoustiques. Nous nous intéressons plus particulièrement au cas de mousses qui, présentant une forte hétérogénéité locale de tailles de pores, ne peuvent être décrites par une cellule périodique idéalisée (modèle déterministe). Des techniques d'imagerie avancées (microtomographie axiale à rayons-X et microscopie électronique à balayage) sont utilisées, dans un premier temps, pour identifier les caractéristiques morphologiques des microstructures étudiées. Les caractéristiques géométriques obtenues sont ensuite modélisées afin de reconstruire des partitions spatiales proches de celles mesurées. La perméabilité visqueuse, paramètre clé au regard de la détermination des propriétés acoustiques, est estimée par une simulation de type "pore-network". Nous quantifions, au travers de telles simulations, que la perméabilité d'une mousse est fortement influencée, non seulement par la présence des membranes, mais aussi par la variation de la taille des pores. L'effet de l'épaisseur de membrane sur les paramètres visqueux (longueur caractéristique visqueuse et tortuosité) décrivant le comportement asymptotique haute fréquence est, de plus, finement étudié. Les résultats obtenus montrent, en particulier, qu'il est possible de modéliser l'effet de l'épaisseur de membranes minces par des membranes virtuelles sans épaisseur pour le calcul de la longueur caractéristique visqueuse. Enfin, les propriétés acoustiques d'un échantillon réel de mousse ayant une distribution étendue de tailles de pores sont modélisées. Une bonne concordance avec les données expérimentales obtenues à partir d'un tube d'impédance confirme la validité de la méthode proposéeFoam materials are frequently used in engineering applications, due to their absorption and sound insulation properties. At the same time, the evolution of CO2 emission goals, together with new standards for acoustic, thermal, and fire resistance performance, calls for further developments that seek to reduce the impact of acoustic treatments---while maintaining, or even improving, global performance. Fine particles are usually introduced during the foaming process to improve fire resistance. By disrupting the nucleation sites, this procedure leads to disordered microstructures where cells of very different sizes coexist locally. This thesis work deals with the construction and experimental validation of a computational multi-scale-informed framework for modeling the acoustic behavior of polydisperse foams. The main objective is to model the relationships between the local foam geometry and the acoustic behavior exhibited at macroscale, with a view towards devising foam manufacturing conditions under acoustic performance targets. Here, we restrict our attention to the case of foams which present strong local heterogeneities in terms of pore sizes and therefore cannot be described by a deterministic unit cell. Advanced imaging techniques (namely, axial X-ray microtomography and scanning electron microscopy) are first deployed to identify relevant morphological characteristics on the studied microstructures. The geometrical properties thus obtained are then used in order to reconstruct spatial partitions consistent with the observations. The viscous permeability, which is a key parameter for the determination of acoustic properties, is estimated through a "Pore-Network" simulations. The numerical predictions show that the permeability of a foam is strongly influenced, not only by the presence of membranes, but also by the variation of pore sizes. The effect of membrane thickness on viscous parameters (i.e., the viscous characteristic length and the tortuosity) describing the asymptotic behavior at high frequencies is also thoroughly studied. For the calculation of the viscous characteristic length, the results show that the effect of thin-membrane thickness can equivalently be modeled by virtual membranes without thickness. Finally, the acoustic properties of a real foam sample presenting a wide pore size distribution are modeled. Good agreement with experimental data obtained from an impedance tube is observed, which supports the relevance of the proposed approac

Dually cationic and anionic pH/temperature-sensitive injectable hydrogels and potential application as a protein carrier

Novel copolymers containing both anionic and cationic pH-sensitive moieties were reported. These amphoteric copolymers exhibited special closed-loop reversible sol-gel-sol phase transitions in response to both pH and temperature

Étude numérique multi-échelle des relations structure-propriétés acoustiques d'une mousse à distribution étendue de tailles de pores

International audienceAn acoustic foam is utilized increasingly in industrial by replacing the fibrous layer because of particularly a health reason. Its acoustic properties depend heavily on its microstructures (pore size's distribution , membrane presence). The aim of this work is to study the influence of an extended of pore size's distribution on its properties acoustic and elastic. The microstructure of the acoustic foam is created in three steps. Firstly, by using the discrete element method, a random stack of sphere is generated. After that, a tessellation of Laguerre from the center and radius of the spheres is carried out to build a foam skeleton. Finally, the Plateau borders, that have a concave triangular section of a variable thickness, is obtained by a minimizing of surface energy with the help of a Surface Evolver software. A simulation with the help of the finite elements method evaluates the properties acoustic.Les mousses acoustiques sont de plus en plus utilisées dans l'industrie en remplacement des milieux fibreux pour des raisons de santé notamment. Leurs propriétés acoustiques dépendent fortement de leurs microstructures (distribution de taille de pores, présence de membranes). L'objectif de ce travail est d'étudier l'influence d'une distribution étendue de tailles de pores sur les propriétés acoustiques et élastiques. La microstructure des mousses est reconstruite en trois étapes. La première étape consiste en la génération d'un empilement aléatoire de sphères, généré par la méthode des éléments discrets. Ensuite, une tessellation de Laguerre à partir des centres et des rayons des sphères est réalisée pour construire le squelette de la mousse. Finalement, les bords de Plateau ayant une section triangulaire concave d'épaisseur variable, sont obtenus par minimisation d'énergie de surface à l'aide du logiciel Surface Evolver. Les propriétés acoustiques sont calculées à l'aide de simulations par la méthode des éléments finis

Toward group-based user-attribute policies in azure-like access control systems

Cloud resources are increasingly pooled together for collaboration among users from different administrative units. In these settings, separation of duty between resource and identity management is strongly encouraged, as it streamlines organization of resource access in cloud. Yet, this separation may hinder availability and accessibility of resources, negating access to authorized and entitled subjects. In this paper, we present an in-depth analysis of group-reachability in user attribute-based access control. Starting from a concrete instance of an Access Control supported by the Azure platform, we adopt formal verification methods to demonstrate how it is possible to mitigate access availability issues, which may arise as per-attribute criteria groups are deployed

Permeability of polydisperse solid foams

International audienceThe effect of polydispersity on foam permeability is investigated by numerical simulations. Foam structures are first generated by Laguerre tessellations via the Neper software and relaxed to minimize the surface energy via the Surface Evolver software. The fluid flow and permeability are then calculated by means of pore-network simulations, by considering either fully open-cell foams or foams with randomly selected closed windows. Different configurations of window aperture are used, including identical window aperture size, identical window aperture ratio, or random window aperture ratio. The main results are obtained for the case of foams having identical and uniform window aperture ratios. For such foams and at constant mean pore size, foam permeability is found to strongly increase with the polydispersity degree. The numerical results are employed to discuss the validity of the mean pressure field assumption used to calculate the foam permeability, the effect of small pores, and the definition of an equivalent Kelvin foam size. We show that as long as the fluctuations of the window aperture ratio remain low, foam permeability can be estimated by using the mean pressure field hypothesis. The weak effect of small pores on permeability is related to their small contribution to the overall fluid volume fraction. Finally, various estimations of the equivalent Kelvin foam size based on pore-size distribution are propose

Growth modelling and mechanical study of anisotropy of polymer spherulite aggregates

International audienc

Synthesis and characterization of poly(amino urea urethane)-based block copolymer and its potential application as injectable pH/temperature-sensitive hydrogel for protein carrier

A series of novel block copolymer comprising of poly(ethylene glycol) (PEG) and poly(amino urea urethane) (PAUU) was simply synthesized and characterized. The block copolymers were synthesized by a polyaddition reaction between isocyanate groups of 1,6-diisocyanato hexamethylene with secondary amine and hydroxyl groups of 2-hydroxyethyl piperazine and hydroxyl groups at the ends of PEG in chloroform in the presence of dibutyltin dilaurate as a catalyst and characterized by H and C NMR, FTIR and gel permeation chromatography. Copolymer aqueous solutions exhibited pH/temperature-dependent sol-gel phase transitions with a sol-to-gel and a gel-to-sol phase transition corresponding to the increasing of pH and temperature, respectively, with low concentrations. The gel regions covered the physiological condition and could be modulated by changing PAUU fraction, molecular weight of PEG and copolymer concentration. The copolymer hydrogel did not show cytotoxicity. After injecting the copolymer solution subcutaneously into SD rats, an in situ gel formed rapidly. The copolymer hydrogel was confirmed as a protein depot carrier; it showed a sustained release of FITC-BSA over 6 weeks. This novel pH/temperature-sensitive hydrogel system is a potential applicable candidate for protein carrier