31 research outputs found
GABAergic System in Action: Connection to Gastrointestinal Stress-related Disorders
No full textBackground: Currently, treatment of stress-related gastrointestinal disorders, such as inflammatory bowel disease (IBD) and irritable bowel syndrome (IBS), is mainly symptomatic since there is no drug on the market that solves effectively diverse disease symptoms and comorbid states. Recently GABA receptors have been identified within gastrointestinal system and it has been recognized that among various GABAergic drugs some of them influence gastrointestinal stress-related diseases. Among them benzodiazepines have been investigated due to their diverse effects: neuroimmunomodulatory, relief of visceral pain and anxiolytic action.Conclusion: The present review brings findings on the expression of GABA receptors in the gastrointestinal tract and the role of GABA within it. We also present knowledge on the role of neurotransmitter GABA and various GABAergic ligands on diverse physiologic gastrointestinal functions with special emphasize to stress-related disorders. The rationale for therapeutic use and further identification of a potential GABAergic treatment of stress-related disorders has been critically discussed
Runaway electron beam stability and decay in COMPASS
No full textThis paper presents two scenarios used for generation of a runaway electron (RE) beam in the COMPASS tokamak with a focus on the decay phase and control of the beam. The first scenario consists of massive gas injection of argon into the current ramp-up phase, leading to a disruption accompanied by runaway plateau generation. In the second scenario, injection of a smaller amount of gas is used in order to isolate the RE beam from high-temperature plasma. The performances of current control and radial and vertical position feedback control in the second scenario were experimentally studied and analysed. The role of RE energy in the radial position stability of the RE beam seems to be crucial. A comparison of the decay phase of the RE beam in various amounts of Ar or Ne was studied using absolute extreme ultraviolet (AXUV) tomography and hard x-ray (HXR) intensity measurement. Argon clearly leads to higher HXR fluxes for the same current decay rate than neon, while radiated power based on AXUV measurements is larger for Ne in the same set of discharges
Runaway electron experiments at COMPASS in support of the EUROfusion ITER physics research
No full textKinetic modelling of runaway electron avalanches in tokamak plasmas
No full textRunaway electrons can be generated in tokamak plasmas if the accelerating force from the toroidal electric field exceeds the collisional drag force owing to Coulomb collisions with the background plasma. In ITER, disruptions are expected to generate runaway electrons mainly through knock-on collisions (Hender et al 2007 Nucl. Fusion 47 S128-202), where enough momentum can be transferred from existing runaways to slow electrons to transport the latter beyond a critical momentum, setting off an avalanche of runaway electrons. Since knock-on runaways are usually scattered off with a significant perpendicular component of the momentum with respect to the local magnetic field direction, these particles are highly magnetized. Consequently, the momentum dynamics require a full 3D kinetic description, since these electrons are highly sensitive to the magnetic non-uniformity of a toroidal configuration. For this purpose, a bounce-averaged knock-on source term is derived. The generation of runaway electrons from the combined effect of Dreicer mechanism and knock-on collision process is studied with the code LUKE, a solver of the 3D linearized bounce-averaged relativistic electron Fokker-Planck equation (Decker and Peysson 2004 DKE: a fast numerical solver for the 3D drift kinetic equation Report EUR-CEA-FC-1736, Euratom-CEA), through the calculation of the response of the electron distribution function to a constant parallel electric field. The model, which has been successfully benchmarked against the standard Dreicer runaway theory now describes the runaway generation by knock-on collisions as proposed by Rosenbluth (Rosenbluth and Putvinski 1997 Nucl. Fusion 37 1355-62). This paper shows that the avalanche effect can be important even in non-disruptive scenarios. Runaway formation through knock-on collisions is found to be strongly reduced when taking place off the magnetic axis, since trapped electrons can not contribute to the runaway electron population. Finally, the relative importance of the avalanche mechanism is investigated as a function of the key parameters for runaway electron formation, namely the plasma temperature and the electric field strength. In agreement with theoretical predictions, the LUKE simulations show that in low temperature and electric field the knock-on collisions becomes the dominant source of runaway electrons and can play a significant role for runaway electron generation, including in non-disruptive tokamak scenarios.SP
Asymmetric Primaquine and Halogenaniline Fumardiamides as Novel Biologically Active Michael Acceptors
No full textNovel primaquine (PQ) and halogenaniline asymmetric fumardiamides 4a–f, potential Michael acceptors, and their reduced analogues succindiamides 5a–f were prepared by simple three-step reactions: coupling reaction between PQ and mono-ethyl fumarate (1a) or mono-methyl succinate (1b), hydrolysis of PQ-dicarboxylic acid mono-ester conjugates 2a,b to corresponding acids 3a,b, and a coupling reaction with halogenanilines. 1-[bis(Dimethylamino)methylene]-1H-1,2,3-triazolo[4,5-b]pyridinium 3-oxide hexafluorophosphate (HATU) was used as a coupling reagent along with Hünig′s base. Compounds 4 and 5 were evaluated against a panel of bacteria, several Mycobacterium strains, fungi, a set of viruses, and nine different human tumor cell lines. p-Chlorofumardiamide 4d showed significant activity against Staphylococcus aureus,Streptococcus pneumoniae and Acinetobacter baumannii, but also against Candida albicans (minimum inhibitory concentration (MIC) 6.1–12.5 µg/mL). Together with p-fluoro and p-CF3 fumardiamides 4b,f, compound 4d showed activity against Mycobacterium marinum and 4b,f against M. tuberculosis. In biofilm eradication assay, most of the bacteria, particularly S. aureus, showed susceptibility to fumardiamides. m-CF3 and m-chloroaniline fumardiamides 4e and 4c showed significant antiviral activity against reovirus-1, sindbis virus and Punta Toro virus (EC50 = 3.1–5.5 µM), while 4e was active against coxsackie virus B4 (EC50 = 3.1 µM). m-Fluoro derivative 4a exerted significant cytostatic activity (IC50 = 5.7–31.2 μM). Acute lymphoblastic leukemia cells were highly susceptible towards m-substituted derivatives 4a,c,e (IC50 = 6.7–8.9 μM). Biological evaluations revealed that fumardiamides 4 were more active than succindiamides 5 indicating importance of Michael conjugated system
First dedicated observations of runaway electrons in the COMPASS tokamak
No full textRunaway electrons present an important part of the present efforts in nuclear fusion research with respect to the potential damage of the in-vessel components. The COMPASS tokamak a suitable tool for the studies of runaway electrons, due to its relatively low vacuum safety constraints, high experimental flexibility and the possibility of reaching the H-mode D-shaped plasmas. In this work, results from the first experimental COMPASS campaign dedicated to runaway electrons are presented and discussed in preliminary way. In particular, the first observation of synchrotron radiation and rather interesting raw magnetic data are shown
Group membership affects spontaneous mental representation : Failure to represent the out-group in a joint action task
No full textPredicting others’ actions is crucial to successful social interaction. Previous research on joint action, based on a reaction-time paradigm called the Joint Simon Task, suggests that successful joint action stems from the simultaneous representation of the self with the other. Performance on this task provides a read-out of the degree of intrusion from a partner that participants experience from acting jointly compared to acting alone, which in turn is a measure of the degree to which participants mentally represent their co-actors during the task. To investigate the role of perceived group membership in this type of joint action and its influence on the representation of others, we first subjected participants to a minimal group paradigm while manipulating differences in social competition. We then asked participants to do the Joint Simon Task in pairs with an in-group or out-group member. Only participants who acted with an “in-group” partner on the joint task showed altered reaction times compared to when acting alone, presumably a change caused by the simultaneous and automatic representation of their in-group partner. In contrast, participants who acted with an out-group partner were unaffected in their reactions when doing the joint task, showing no evidence of representation of their out-group partner. This effect was present in both the high-competition and low-competition conditions, indicating that the differential effects of group membership on representation during joint action were driven by perceived group membership and independent of the effects of social competition. We concluded that participants failed to represent out-group members as socially relevant agents not based on any personality or situational characteristics, but in reaction only to their status as “other”. In this way group membership appears to affect cognition on a very immediate and subconscious level.Peer reviewe
Development of a Cherenkov-type diagnostic system to study runaway electrons within the COMPASS tokamak
No full textComparison of runaway electron generation parameters in small, medium-sized and large tokamaks-A survey of experiments in COMPASS, TCV, ASDEX-Upgrade and JET
No full textThis paper presents a survey of the experiments on runaway electrons (RE) carried out recently in frames of EUROFusion Consortium in different tokamaks: COMPASS, ASDEX-Upgrade, TCV and JET. Massive gas injection (MGI) has been used in different scenarios for RE generation in small and medium-sized tokamaks to elaborate the most efficient and reliable ones for future RE experiments. New data on RE generated at disruptions in COMPASS and ASDEX-Upgrade was collected and added to the JET database. Different accessible parameters of disruptions, such as current quench rate, conversion rate of plasma current into runaways, etc have been analysed for each tokamak and compared to JET data. It was shown, that tokamaks with larger geometrical sizes provide the wider limits for spatial and temporal variation of plasma parameters during disruptions, thus extending the parameter space for RE generation. The second part of experiments was dedicated to study of RE generation in stationary discharges in COMPASS, TCV and JET. Injection of Ne/Ar have been used to mock-up the JET MGI runaway suppression experiments. Secondary RE avalanching was identified and quantified for the first time in the TCV tokamak in RE generating discharges after massive Ne injection. Simulations of the primary RE generation and secondary avalanching dynamics in stationary discharges has demonstrated that RE current fraction created via avalanching could achieve up to 70-75% of the total plasma current in TCV. Relaxations which are reminiscent the phenomena associated to the kinetic instability driven by RE have been detected in RE discharges in TCV. Macroscopic parameters of RE dominating discharges in TCV before and after onset of the instability fit well to the empirical instability criterion, which was established in the early tokamaks and examined by results of recent numerical simulations.SP
