Dipolar plasma source modeling: a first approach

International audienceThe scaling up of conventional plasmas presents limitations in terms of plasma density, limited to the critical density, and of uniformity, due to the difficulty of achieving constant amplitude standing wave patterns along linear microwave applicators in the meter range. An alternative solution lies in the concept of distribution from one- to two-dimensional networks of elementary plasma. Each elementary plasma source consists in a permanent magnet on which microwaves are applied via an independent coaxial line [1]. The plasma is produced by the electrons accelerated at ECR (Electron Cyclotron Resonance) and trapped in the dipolar magnetic field. Large-size uniform plasmas can be obtained by assembling as many such elementary plasma sources as necessary, without any physical or technical limitations [2]. Simulation of the plasma produced by a dipolar source requires a global, self consistent, modeling of its functioning. In order to obtain results to lead a first optimization of the dipolar source, magnetostatics, microwave propagation and fast electrons trajectories (Particles in Cell (PIC) and Monte-Carlo hybrid method [3]) have been performed with Comsol Multiphysics and MatLab

Oxygenated versus non-oxygenated flush out and storage of donor livers:An experimental study

Background: During donor organ procurement and subsequent static cold storage (SCS), hepatic adenosine triphosphate (ATP) levels are progressively depleted, which contributes to ischemia-reperfusion injury (IRI). We sought to investigate a simple approach to prevent ATP depletion and IRI using a porcine donation after circulatory death (DCD) liver reperfusion model. Methods: After 30 min warm ischemia, porcine livers were flushed via the portal vein with cold (4 degrees C) non-oxygenated University of Wisconsin (UW) preservation solution (n = 6, control group) or with oxygenated UW (n = 6, OxyFlush group). Livers were then subjected to 4 h SCS in non-oxygenated (control) or oxygenated (OxyFlush) UW, followed by 4 h normothermic reperfusion using whole blood. Hepatic ATP levels were compared, and hepatobiliary function and injury were assessed. Results: At the end of SCS, ATP was higher in the OxyFlush group compared to controls (delta ATP of +0.26 vs. -0.68 mu mol/g protein, p = 0.04). All livers produced bile and metabolized lactate, and there were no differences between the groups. Grafts in the OxyFlush group had lower blood glucose levels after reperfusion (p = 0.04). Biliary pH, glucose and bicarbonate were not different between the groups. Injury markers including liver transaminases, lactate dehydrogenase, malondialdehyde, cell-free DNA and flavin mononucleotide in the SCS solution and during reperfusion were also similar. Histological assessment of the parenchyma and bile ducts did not reveal differences between the groups. Conclusion: Oxygenated flush out and storage of DCD porcine livers prevents ATP depletion during ischemia, but this does not seem sufficient to mitigate early signs of IRI

Prolonged dual hypothermic oxygenated machine preservation (DHOPE-PRO) in liver transplantation:study protocol for a stage 2, prospective, dual-arm, safety and feasibility clinical trial

INTRODUCTION: End-ischaemic preservation of a donor liver by dual hypothermic oxygenated machine perfusion (DHOPE) for 2 hours prior to transplantation is sufficient to mitigate ischaemia-reperfusion damage and fully restore cellular energy levels. Clinical studies have shown beneficial outcomes after transplantation of liver grafts preserved by DHOPE compared with static cold storage. In addition to graft reconditioning, DHOPE may also be used to prolong preservation time, which could facilitate logistics for allocation and transplantation globally. METHODS AND ANALYSIS: This is a prospective, pseudo-randomised, dual-arm, IDEAL-D (Idea, Development, Exploration, Assessment, Long term study-Framework for Devices) stage 2 clinical device trial designed to determine safety and feasibility of prolonged DHOPE (DHOPE-PRO). The end-time of the donor hepatectomy will determine whether the graft will be assigned to the intervention (16:00–3:59 hour) or to the control arm (4:00–15:59 hour). In total, 36 livers will be included in the study. Livers in the intervention group (n=18) will undergo DHOPE-PRO (≥4 hours) until implantation the following morning, whereas livers in the control group (n=18) will undergo regular DHOPE (2 hours) prior to implantation. The primary endpoint of this study is a composite of the occurrence of all (serious) adverse events during DHOPE and up to 30 days after liver transplantation. ETHICS AND DISSEMINATION: The protocol was approved by the Medical Ethical Committee of Groningen, METc2020.126 in June 2020, and the study was registered in the Netherlands National Trial Registry (https://www.trialregister.nl/) prior to initiation. TRIAL REGISTRATION NUMBER: NL8740

Analysis of soil moisture conservation techniques with dry season maize crop on hill land at Rubirizi, Rwanda

Presented at GLOBELICS 2009, 7th International Conference, 6-8 October, Dakar, Senegal.Parallel session 3: Sustainability and technology adoption in agricultureRwanda is an agriculture based country where crop production is carried out under rain fed situation with wide range of agro climatic conditions. Field experiments were conducted with in-situ soil moisture conservation techniques in bench terraces and unterraced field by using maize crop variety Kathumani from June 2007 to October 2007 by involving three land management practices viz. ridges and furrows, compartmental bunding and control. The study explores the best technical option to resolve the constraints related to water management in rainfed farming in Rwanda. Insufficient rainfall during dry season attracts the need of water harvesting and soil moisture conservation. The study is based on weekly soil moisture analysis in 90cm soil depth. Analysis of rainfall and crop water demand indicates that it is inevitable to provide supplemental irrigation and in-situ moisture conservation for successful crop. Bench terrace increased the average soil moisture content in 90cm soil depth by more than 50 per cent than that of unterraced land. Within the bench terraced field compartmental bunding increased soil moisture by 18.2 per cent higher than plain bed (control) with a coefficient of variation of 20.6 per cent and ridges & furrows increased by 27.8 per cent with coefficient of variation of 29.3 per cent. This indicates that in-situ moisture conservation measures are effective to increase soil moisture compared to plain bed. It is also found that mean soil moisture fluctuation in the soil profile is moderately more at 60cm depth compared to 30 cm irrespective of type of conservation techniques. Performance of ridges & furrows, compartmental bunding and plain land (control) was evaluated in terms of soil moisture conservation. The study reveals that Compartmental bunding performed well in both 30cm and 60cm soil depths followed by ridges & furrows because of consistent soil moisture as evidenced by less coefficient of variation. Higher moisture content in these two techniques is due to water barrier to harvest rainwater. Average soil moisture content for compartmental bunding and ridges & furrows varied between 16 to 17 per cent at both 30cm 60 cm soil depths and 13 per cent for plain bed (control). In all the three techniques, actual soil water during the entire cropping period remains below field capacity posing soil moisture stress. The maize yield was very poor in all the techniques because the soil water depleted to 60 per cent and above from the beginning of the cropping period inferring the need for supplementary irrigation. Plain bed (control) exhibited lowest degree of fluctuation of deficit water indicating poorly influenced by rain fall as compared to ridges & furrows and compartmental bunding. In terms of efficiency of moisture conservation during the cropping period, ridges & furrows performed well with 85.8% followed by compartmental bunding with 75.9 per cent in terraced field. Unterraced field with 15 per cent slope conserved moisture very poorly with 13.9% efficiency inferring importance of bench terraces for efficient soil moisture conservation. Performance of different in-situ moisture conservation practices were analyzed in terms of available water, deficit water, crop water and its effect on maize yield was discussed in this paper

Étude d'un plasma micro-onde d'hydrogène en configuration matricielle pour application potentielle au dépôt de diamant sur grande surface

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