Role of the edge electric field in the resonant mode-particle interactions and the formation of transport barriers in toroidal plasmas

The impact of an edge radial electric field on the particle orbits and the orbital spectrum in an axisymmetric toroidal magnetic equilibrium is investigated using a guiding center canonical formalism. Poloidal and bounce/transit-averaged toroidal precession frequencies are calculated, highlighting the role of the radial electric field. The radial electric field is shown to drastically modify the resonance conditions between particles with certain kinetic characteristics and specific perturbative non-axisymmetric modes and to enable the formation of transport barriers. The locations of the resonances and the transport barriers, that determine the particle, energy and momentum transport are shown to be accurately pinpointed in the phase space, by employing the calculated orbital frequencies.Comment: 23 pages, 8 figure

Kinetic versus Magnetic Chaos in Toroidal Plasmas: A systematic quantitative comparison

Magnetic field line chaos occurs under the presence of non-axisymmetric perturbations of an axisymmetric equilibrium and is manifested by the destruction of smooth flux surfaces formed by the field lines. These perturbations also render the particle motion, as described by the guiding center dynamics, non-integrable and, therefore, chaotic. However, the chaoticities of the magnetic field lines and the particle orbits significantly differ both in strength and radial location in a toroidal configuration, except for the case of very low-energy particles whose orbits closely follow the magnetic field lines. The chaoticity of more energetic particles, undergoing large drifts with respect to the magnetic field lines, crucially determines the confinement properties of a toroidal device but cannot be inferred from that of the underlying magnetic field. In this work, we implement the Smaller ALignment Index (SALI) method for detecting and quantifying chaos, allowing for a systematic comparison between magnetic and kinetic chaos. The efficient quantification of chaos enables the assignment of a value characterizing the chaoticity of each orbit in the space of the three constants of the motion, namely energy, magnetic moment and toroidal momentum. The respective diagrams provide a unique overview of the different effects of a specific set of perturbations on the entire range of trapped and passing particles, as well as the radial location of the chaotic regions, offering a valuable tool for the study of particle energy and momentum transport and confinement properties of a toroidal fusion device.Comment: 27 pages, 7 figure

Lactate serum concentrations during treatment with nucleos(t)ide analogues in hepatitis B with or without cirrhosis

Objective The aim of this study is to evaluate the clinical implications of lactate concentrations in patients with hepatitis B with or without cirrhosis during treatment with nucleos(t)ide analogues. Patients and methods One hundred and seven consecutive patients with chronic hepatitis B and median age 57(24-85) years were prospectively included. Lactate concentrations were measured at baseline and at 12, 24, 36, 48, and 60 months following the baseline measurements. Eight (n=8, 7.5%) patients received lamivudine, 38 (n=38, 35.5%) patients received tenofovir, 34 (n=34, 31.8%) patients received entecavir, and 27 (n=27, 25.2%) patients received combined therapy. Results None of the patients developed lactic acidosis during follow-up [median: 58 (6-155) months]. Overall, no trends of the lactic acid evolution were observed over time; however, there was a nonsignificant increasing trend in patients with cirrhosis up to 24 months of treatment. This increasing trend was significant in female patients with cirrhosis (P=0.016). The age of the patients, the presence of cirrhosis, and hepatocellular carcinoma were strongly associated with the survival of all patients. In the group of cirrhotic patients, the only independent prognostic factor that was associated with patients’ survival was the Child-Pugh class. Conclusion None of the patients developed lactic acidosis. There is an indication of an increasing trend of lactic acid levels up to 24 months of therapy in female cirrhotic patients. Copyright (C) 2017 Wolters Kluwer Health, Inc. All rights reserved