Coupling the COST reference plasma jet to a microfluidic device: a computational study

ABSTRACT: The use of microfluidic devices in the field of plasma-liquid interaction can unlock unique possibilities to investigate the effects of plasma-generated reactive species for environmental and biomedical applications. So far, very little simulation work has been performed on microfluidic devices in contact with a plasma source. We report on the modelling and computational simulation of physical and chemical processes taking place in a novel plasma-microfluidic platform. The main production and transport pathways of reactive species both in plasma and liquid are modelled by a novel modelling approach that combines 0D chemical kinetics and 2D transport mechanisms. This combined approach, applicable to systems where the transport of chemical species occurs in unidirectional flows at high Péclet numbers, decreases calculation times considerably compared to regular 2D simulations. It takes advantage of the low computational time of the 0D reaction models while providing spatial information through multiple plug-flow simulations to yield a quasi-2D model. The gas and liquid flow profiles are simulated entirely in 2D, together with the chemical reactions and transport of key chemical species. The model correctly predicts increased transport of hydrogen peroxide into the liquid when the microfluidic opening is placed inside the plasma effluent region, as opposed to inside the plasma region itself. Furthermore, the modelled hydrogen peroxide production and transport in the microfluidic liquid differs by less than 50% compared with experimental results. To explain this discrepancy, the limits of the 0D–2D combined approach are discussed

3D Cohort Study : The Integrated Research Network in Perinatology of Quebec and Eastern Ontario

Background: The 3D Cohort Study (Design, Develop, Discover) was established to help bridge knowledge gaps about the links between various adverse exposures during pregnancy with birth outcomes and later health outcomes in children. Methods: Pregnant women and their partners were recruited during the first trimester from nine sites in Quebec and followed along with their children through to 2 years of age. Questionnaires were administered during pregnancy and post-delivery to collect information on demographics, mental health and life style, medical history, psychosocial measures, diet, infant growth, and neurodevelopment. Information on the delivery and newborn outcomes were abstracted from medical charts. Biological specimens were collected from mothers during each trimester, fathers (once during the pregnancy), and infants (at delivery and 2 years of age) for storage in a biological specimen bank. Results: Of the 9864 women screened, 6348 met the eligibility criteria and 2366 women participated in the study (37% of eligible women). Among women in the 3D cohort, 1721 of their partners (1704 biological fathers) agreed to participate (73%). Two thousand two hundred and nineteen participants had a live singleton birth (94%). Prenatal blood and urine samples as well as vaginal secretions were collected for ≥98% of participants, cord blood for 81% of livebirths, and placental tissue for 89% of livebirths. Conclusions: The 3D Cohort Study combines a rich bank of multiple biological specimens with extensive clinical, life style, and psychosocial data. This data set is a valuable resource for studying the developmental etiology of birth and early childhood neurodevelopmental outcomes

Proceedings from the 2018 Canadian Association for the Study of the Liver Single Topic Conference—Decompensated Cirrhosis : from clinic to transplant

Actes publiés dans le Canadian Liver Journal; vol. 2, no. 4, Fall 2019, p. 137-170

Développement de méthodes d'échantillonnage de particules de poudre modifiées lors d'impressions par FSL de l'alliage de titane Ti64

RÉSUMÉ: La fusion de lit de poudre par laser (FSL) est une méthode de fabrication additive (FA), souvent appelée impression 3D, qui offre plusieurs avantages comparativement à des méthodes plus conventionnelles telles que la coulée et l'usinage. Notamment, les pièces imprimées peuvent avoir des géométries plus complexes qui permettent l'optimisation des propriétés des pièces tout en minimisant la masse de celles-ci. Un autre avantage de taille est la minimisation des retailles de fabrication par rapport à ce qui se produit avec des méthodes conventionnelles. En effet, à la suite de la fusion du lit de poudre lors de la fabrication de la pièce, une grande partie de la poudre n'ayant pas été fondue peut être récupérée pour des impressions subséquentes. Cependant, la poudre récupérée et recyclée peut avoir été modifiée durant l'impression par FSL. En effet, le passage du laser sur le lit de poudre engendre la génération de particules projetées ailleurs sur le lit de poudre. L'élévation de la température localement près du laser peut aussi affecter thermiquement les particules de telle sorte que leur état soit modifié. L'effet des différentes particules modifiées lors d'une impression sur les propriétés des pièces imprimées n'est pas très bien connu. Il est important de bien caractériser chaque type de particules modifiées (nombre, forme, taille, couleur, composition chimique) pour pouvoir ensuite établir un lien avec des effets sur les pièces imprimées. Dans le cadre de cette étude, deux méthodes d'échantillonnage des projections et des particules affectées thermiquement près des zones du lit de poudre fusionnée ont été développées en collaboration avec Safran Tech et Tekna. La poudre utilisée est de la poudre de Ti-6Al-4V ELI (Extra Low Interstitial) de grade 23. Les échantillons recueillis permettent la caractérisation d'un grand nombre de particules. Quatre types de projections et un type de particules affectées thermiquement ont été identifiés. Parmi les types de projections, on trouve les particules soufflées et non affectées, les particules oxydées et colorées, les particules sphériques de grande taille et les agrégats. ABSTRACT: Selective Laser Melting (SLM) is an Additive Manufacturing (AM) or 3D printing method that offers a variety of advantages compared to more conventional fabrication methods such as casting and machining. In fact, the printed parts can reach higher geometric complexity that allows to optimize the properties of the parts while minimizing their weight. Another advantage is the minimisation of the disposal of material compared to conventional methods. Indeed, after the SLM process, a large proportion of the powder that was not melted can be recycled for subsequent printings. However, the recycled powder can be modified during the SLM printing. Indeed, the scanning of the laser on the powder bed causes the generation of projected particles, or spatters, elsewhere on the powder bed. The local temperature elevation can also heat affect surrounding particles and modify their state. The effect of the various types of modified particles on the properties of the printed parts is not well known. It is important to thoroughly characterize each type of modified particles (amount, shape, size, color, chemical composition) in order to establish a relation between those particles and the effects on the properties of the printed parts. In this study, two sampling methods of spatters and heat affected particles near areas of the powder bed that was melted were developed in collaboration with Safran Tech and Tekna. The powder that was used during those printings is a Ti-6Al-4V ELI (grade 23) powder. The gathered samples allow the characterization of a large number of particles. Four types of spatters and one type of heat affected particle were identified. Among the spatter types, there is the unaffected and blown, the oxidized and colored, the large and spherical and the aggregates. The oxidized and colored spatters have an oxygen concentration at their surface (for an electron penetration depth of about 220 nm under the surface) of more than 8 wt% whereas the large and spherical spatters have an oxygen concentration at their surface of more than 5 wt%. The unaffected and blown spatters are oxidized similarly to the particles from the virgin powder and the oxygen concentration at the surface of the aggregates depend on the particles of the powder bed that contributed to the formation of the aggregate

Microfluidic Devices as Diagnostic Tools for Plasma-Liquid and Plasma-Bio Interactions

RÉSUMÉ: Au cours des deux dernières décennies, les plasmas à basse température et à pression atmosphérique ont reçu un intérêt croissant de la part de chercheurs en technologies biomédicales. Ces plasmas peuvent influencer les processus biologiques naturels par le biais des photons qu’ils émettent et des espèces chimiques réactives qu’ils produisent. De nombreuses espèces chimiques produites par les plasmas en contact avec des gaz atmosphériques sont les mêmes que celles impliquées dans divers processus biologiques, dont la signalisation cellulaire. Aujourd’hui, les applications biomédicales du plasma incluent le traitement de plaies chroniques, le traitement de cellules et tissus cancéreux, la stérilisation et la décontamination. Afin d’accélérer la transition vers des traitements cliniques utilisant le plasma, les chercheurs de la communauté biomédicale sont à la recherche de modèles biologiques reproductibles, fiables et bien établis pour étudier les interactions entre des systèmes biologiques et les plasmas. À cet effet, nous croyons que l’utilisation de dispositifs microfluidiques offre des opportunités pour de telles recherches puisque leur utilisation permet déjà de reproduire efficacement et à faible coût des expériences de laboratoire dans différents domaines, dont la chimie analytique, la biochimie et la biologie. Ainsi, l’objectif central du projet est le développement d’une plateforme qui combine un dispositif microfluidique à une source de plasma afin de fournir de nouveaux outils pour l’étude des interactions plasma-liquide et pour utiliser la microfluidique dans un contexte de recherche en médecine par plasma. Pour ce faire, une nouvelle plateforme plasma-microfluidique a été développée permettant de mettre en contact un plasma d’hélium et de vapeur d’eau avec un liquide circulant dans un dispositif microfluidique. Cette plateforme combine le COST-Jet, une source de plasma de référence, avec des dispositifs microfluidiques fabriqués par impression 3D. Ces derniers ont été développés pour créer un écoulement de liquide et de gaz permettant à la fois une opération stable de la plateforme et une optimisation du transport des espèces chimiques générées par le plasma vers le liquide. La source de plasma a été caractérisée électriquement par une mesure de la dissipation de puissance de la décharge plasma. Les sources de plasma miniatures, comme le COST-Jet, ont de faibles capacitances menant facilement à de larges erreurs lors d’une mesure de puissance dissipée. Pour contrer ce problème, une méthode d’adaptation d’impédance a été adoptée permettant la mesure de la puissance dissipée par le plasma avec une incertitude de moins de 15%. ABSTRACT: In the last two decades, non-thermal and atmospheric pressure plasmas have received increas-ing interest from researchers in biomedical technologies. These plasmas can influence natural biological processes through the photons they emit and the reactive chemical species they produce. Many of the chemical species produced by plasmas in contact with atmospheric gases are the same as those involved in various biological processes including cell signaling. Today, biomedical applications of plasma include treatment of chronic wounds, treatment of cancerous cells and tissues, sterilization and decontamination. To accelerate the transition to plasma treatment in a clinical context, researchers of the plasma medicine community need reliable, reproducible and well-established biological mod-els to study the interactions between biological systems and plasmas. To this end, we believe that the use of microfluidic devices offers relevant opportunities for such research as microflu-idic devices already allow for efficient and low-cost replication of laboratory experiments in various fields of research including analytical chemistry, biochemistry and biology. Thus, the central objective of the project is the development of a platform that combines a microfluidic device with a reference plasma source to provide new tools for fundamental plasma-liquid interactions studies and to enable the use of microfluidics in the context of plasma medicine research. To this end, a new plasma-microfluidic platform has been devel-oped to couple a helium plasma source with a liquid flowing in a microfluidic device. This platform combines the COST-Jet, a reference plasma source, with 3D printed microfluidic devices. The microfluidic devices were developed to form a flow of liquid and gas that al-lows both a stable operation of the platform and an optimization of the transport of the plasma-generated reactive species to the liquid. The plasma source was electrically characterized by measuring the plasma discharge power dissipation. Miniature plasma sources, such as the COST-Jet, have small capacitances which easily lead to large uncertainties in the power dissipation measurement. To tackle this prob-lem, an impedance matching method has been adopted allowing a power measurement un-certainty of less than 15%. Moreover, the production and transport of reactive chemical species to the liquid flowing in the platform was confirmed by hydrogen peroxide concentra-tion measurements. This measured concentration varies from 0 to 25 µM depending on the experimental conditions

Usefulness of Endoscopic Ultrasonography in Hepatology

Endoscopic ultrasonography (EUS) is used to evaluate patients with hepatobiliary diseases. The technique is useful for the diagnosis of esogastric varices in selected cases of portal hypertension, and to evaluate the pathogenic role and prognostic value of the collateral circulation in patients with this condition. When coupled with the Doppler technique, EUS can be used to guide injection sclerotherapy and to verify the obliteration of varices (particularly fundal varices) after endoscopic treatment. Hemodynamic changes induced in the collateral circulation by vasoactive drugs can also be measured with Doppler-EUS. Fine-needle aspiration under EUS guidance is useful in the diagnosis of focal liver lesions and perihepatic adenopathy, and in the evaluation of biliary tract diseases. New indications can be developed in the future after adequate experimental validation

Coupling the COST reference plasma jet to a microfluidic device : a computational study

Abstract: The use of microfluidic devices in the field of plasma-liquid interaction can unlock unique possibilities to investigate the effects of plasma-generated reactive species for environmental and biomedical applications. So far, very little simulation work has been performed on microfluidic devices in contact with a plasma source. We report on the modelling and computational simulation of physical and chemical processes taking place in a novel plasma-microfluidic platform. The main production and transport pathways of reactive species both in plasma and liquid are modelled by a novel modelling approach that combines 0D chemical kinetics and 2D transport mechanisms. This combined approach, applicable to systems where the transport of chemical species occurs in unidirectional flows at high Peclet numbers, decreases calculation times considerably compared to regular 2D simulations. It takes advantage of the low computational time of the 0D reaction models while providing spatial information through multiple plug-flow simulations to yield a quasi-2D model. The gas and liquid flow profiles are simulated entirely in 2D, together with the chemical reactions and transport of key chemical species. The model correctly predicts increased transport of hydrogen peroxide into the liquid when the microfluidic opening is placed inside the plasma effluent region, as opposed to inside the plasma region itself. Furthermore, the modelled hydrogen peroxide production and transport in the microfluidic liquid differs by less than 50% compared with experimental results. To explain this discrepancy, the limits of the 0D-2D combined approach are discussed

Assessment of the spectrum of hepatic encephalopathy: A multicenter study

Hepatic encephalopathy (HE) is a major cause of morbidity in cirrhosis. However, its severity assessment is often subjective, which needs to be studied systematically. The aim was to determine how accurately trainee and nontrainee practitioners grade and manage HE patients throughout its severity. We performed a survey study using standardized simulated patient videos at 4 US and 3 Canadian centers. Participants were trainees (gastroenterology/hepatology fellows) and nontrainees (faculty, nurse practitioners, physician assistants). We determined the accuracy of HE severity identification and management options between grades <2 or ≥2 HE and trainees/nontrainees. In total, 108 respondents (62 trainees, 46 nontrainees) were included. For patients with grades <2 versus ≥2 HE, a higher percentage of respondents were better at correctly diagnosing grades ≥2 compared with grades <2 (91% versus 64%; P < 0.001). Specialized cognitive testing was checked significantly more often in grades <2, whereas more aggressive investigation for precipitating factors was ordered in HE grades >2. Serum ammonia levels were ordered in almost a third of grade ≥2 patients. For trainees and nontrainees, HE grades were identified similarly between groups. Trainees were less likely to order serum ammonia and low-protein diets, more likely to order rifaximin, and more likely to perform a more thorough workup for precipitating factors compared with nontrainee respondents. There was excellent concordance in the classification of grade ≥2 HE between nontrainees versus trainees, but lower grades showed discordance. Important differences were seen regarding blood ammonia, specialized testing, and nutritional management between trainees and nontrainees. These results have important implications at the patient level, interpreting multicenter clinical trials, and in the education of practitioners. Liver Transplantation 24 587-594 2018 AASLD