Implementation of the new multichannel X-mode edge density profile reflectometer for the ICRF antenna on ASDEX Upgrade.

A new multichannel frequency modulated continuous-wave reflectometry diagnostic has been successfully installed and commissioned on ASDEX Upgrade to measure the plasma edge electron density profile evolution in front of the Ion Cyclotron Range of Frequencies (ICRF) antenna. The design of the new three-strap ICRF antenna integrates ten pairs (sending and receiving) of microwave reflectometry antennas. The multichannel reflectometer can use three of these to measure the edge electron density profiles up to 2 × 1019 m-3, at different poloidal locations, allowing the direct study of the local plasma layers in front of the ICRF antenna. ICRF power coupling, operational effects, and poloidal variations of the plasma density profile can be consistently studied for the first time. In this work the diagnostic hardware architecture is described and the obtained density profile measurements were used to track outer radial plasma position and plasma shape.

Fluorination effects on the thermodynamic, thermophysical and surface properties of ionic liquids.

This paper reports the thermal, thermodynamic, thermophysical and surface properties of eight ionic liquids with fluorinated alkyl side chain lengths equal or greater than four carbon atoms. Melting and decomposition temperatures were determined together with experimental densities, surface tensions, refractive indices, dynamic viscosities and ionic conductivities in a temperature interval ranging from 293.15 to 353.15 K. The surface properties of these fluorinated ionic liquids were discussed and several thermodynamic functions, as well as critical temperatures, were estimated. Coefficients of isobaric thermal expansion, molecular volumes and free volume effects were calculated from experimental values of density and refractive index and compared with previous data. Finally, Walden plots were used to evaluate the ionicity of the investigated ionic liquids.

Dispelling some myths about the CO2 solubility in ionic liquids.

Ionic liquids have been objects of extensive research for physical sorption of CO2 and a number of myths have been perpetuated in the literature, for lack of a critical analysis, concerning their potential for CO2 capture. This study carries a critical analysis of a number of widely accepted ideas and others not so well accepted that have been repeatedly expressed in the literature concerning the CO2 physical sorption in ionic liquids. Using the CO2 solubility in eicosane as benchmark, it will be shown that there is no evidence that ILs display a physical sorption of CO2 larger than n-alkanes when analyzed in adequate concentration units; the fluorination of the ions has no impact on the CO2 solubility and the oxygenation will marginally contribute to a decrease of the solubility. Ionic liquid-based deep eutectic systems are also shown to have a poor CO2 solubility. Although these widely used approaches to physically enhance the CO2 solubility in ILs do not seem to have any positive influence, this does not mean that other types of interaction cannot provide enhanced CO2 solubility as in the case of the anion [B(CN)4] confirmed here by a critical analysis of the published data. The mechanism of CO2 physical sorption in ionic liquids is discussed based on the results analyzed, supported by spectroscopic measurements and molecular simulations previously reported and further suggestions of possibilities for enhanced physical sorption based on fluorinated aromatic rings, other cyano based anions, mixtures with other ILs or solvents or the use of porous liquids are proposed.

Real-time plasma control based on the ISTTOK tomography diagnostic.

The presently available processing power in generic processing units (GPUs) combined with state-of-the-art programmable logic devices benefits the implementation of complex, real-time driven, data processing algorithms for plasma diagnostics. A tomographic reconstruction diagnostic has been developed for the ISTTOK tokamak, based on three linear pinhole cameras each with ten lines of sight. The plasma emissivity in a poloidal cross section is computed locally on a submillisecond time scale, using a Fourier-Bessel algorithm, allowing the use of the output signals for active plasma position control. The data acquisition and reconstruction (DAR) system is based on ATCA technology and consists of one acquisition board with integrated field programmable gate array (FPGA) capabilities and a dual-core Pentium module running real-time application interface (RTAI) Linux. In this paper, the DAR real-time firmware/software implementation is presented, based on (i) front-end digital processing in the FPGA; (ii) a device driver specially developed for the board which enables streaming data acquisition to the host GPU; and (iii) a fast reconstruction algorithm running in Linux RTAI. This system behaves as a module of the central ISTTOK control and data acquisition system (FIRESIGNAL). Preliminary results of the above experimental setup are presented and a performance benchmarking against the magnetic coil diagnostic is shown.

Lower esophageal sphincter analysis using computerized manometry in patients with chagasic megaesophagus.

Due to the introduction of computer technology into manometry laboratories, three-dimensional manometric images of the lower esophageal sphincter can be constructed based on radially oriented pressures, a method termed 'computerized axial manometry.' Calculation of the sphincter pressure vector volume using this method is superior to standard manometric techniques in assessing lower esophageal sphincter function in patients with gastroesophageal reflux disease and idiopathic achalasia. Despite similarities between idiopathic achalasia and chagasic esophagopathy found using clinical, radiological, and manometric studies, controversy around lower esophageal sphincter pressure persists. The goal of this study was to analyze esophageal motor disorders in Chagas' megaesophagus using computerized axial manometry. Twenty patients with chagasic megaesophagus (5 men, 15 women, and average age 50.1 years, range 17-64) were prospectively studied. For three-dimensional imaging construction of the lower esophageal sphincter, a low-complacency perfusion system and an eight-channel manometry probe with four radial channels placed in the same level were used. For probe traction, the continuous pull-through technique was used. Results showed that the lower esophageal sphincter of patients with chagasic megaesophagus have significantly elevated pressure, length, asymmetry, and vector volumes compared to those of normal volunteers (P < 0.05). Aperistalsis of the esophageal body waves was observed in all patients and contraction amplitude was lower than that in normal patients. We conclude that patients with chagasic megaesophagus have hypertonic lower esophageal sphincter and aperistalsis of the esophageal body.

Endoscopic sclerosis of the gastric cardia for prevention of experimental gastroesophageal reflux.

Surgical anti-reflux therapy appears to involve the muscles of the proximal gastric cardia and those of the lower esophageal sphincter. In an experimental canine reflux model, we injected sclerosant solution into the submucosa of the proximal gastric cardia, hypothesizing that the subsequent fibrotic reaction might exert an anti-reflux effect. Reflux was induced by atropine infusion, and the amount of reflux was quantitated by pH monitoring. Endoscopic sclerosis was effective in preventing reflux induced by high-dose atropine. Because the length and pressure of the lower esophageal sphincter were unaffected by endoscopic treatment, reflux prevention was possibly related to enhancement of the gastric component of the reflux barrier.

Fibrosis of gastric cardia after endoscopic sclerosis. Mechanism for control of experimental reflux?

Endoscopic sclerosis of the gastric cardia (ESGC) prevents experimental gastroesophageal reflux (GER) without changes in lower esophageal sphincter (LES) pressure and length. This study was performed to define the histologic appearance of the esophagus and stomach one year after ESGC. Four dogs were studied one year after ESGC with morrhuate sodium; ESGC had been performed at six sites, 1-3 cm distal to the esophagogastric junction. All animals had stable weight and eating habits at sacrifice. Light microscopy of the cardia and LES included morphometry of wall thickness (mm) and assessment of fibrosis (- to ). The esophagus had minimal changes; the gastric cardia had focal fibrosis, maximal on the greater curve, without any change difference in wall thickness. ESGC results in fibrosis of the gastric cardia, without significant changes in the esophagus. These changes prevent GER, possibly by preventing the initiation of a reflux event.