Velocity-space sensitivity of the time-of-flight neutron spectrometer at JET

The velocity-space sensitivities of fast-ion diagnostics are often described by so-called weight functions. Recently, we formulated weight functions showing the velocity-space sensitivity of the often dominant beam-target part of neutron energy spectra. These weight functions for neutron emission spectrometry (NES) are independent of the particular NES diagnostic. Here we apply these NES weight functions to the time-of-flight spectrometer TOFOR at JET. By taking the instrumental response function of TOFOR into account, we calculate time-of-flight NES weight functions that enable us to directly determine the velocity-space sensitivity of a given part of a measured time-of-flight spectrum from TOFOR

On the mechanisms governing gas penetration into a tokamak plasma during a massive gas injection

A new 1D radial fluid code, IMAGINE, is used to simulate the penetration of gas into a tokamak plasma during a massive gas injection (MGI). The main result is that the gas is in general strongly braked as it reaches the plasma, due to mechanisms related to charge exchange and (to a smaller extent) recombination. As a result, only a fraction of the gas penetrates into the plasma. Also, a shock wave is created in the gas which propagates away from the plasma, braking and compressing the incoming gas. Simulation results are quantitatively consistent, at least in terms of orders of magnitude, with experimental data for a D 2 MGI into a JET Ohmic plasma. Simulations of MGI into the background plasma surrounding a runaway electron beam show that if the background electron density is too high, the gas may not penetrate, suggesting a possible explanation for the recent results of Reux et al in JET (2015 Nucl. Fusion 55 093013)

Relationship of edge localized mode burst times with divertor flux loop signal phase in JET

A phase relationship is identified between sequential edge localized modes (ELMs) occurrence times in a set of H-mode tokamak plasmas to the voltage measured in full flux azimuthal loops in the divertor region. We focus on plasmas in the Joint European Torus where a steady H-mode is sustained over several seconds, during which ELMs are observed in the Be II emission at the divertor. The ELMs analysed arise from intrinsic ELMing, in that there is no deliberate intent to control the ELMing process by external means. We use ELM timings derived from the Be II signal to perform direct time domain analysis of the full flux loop VLD2 and VLD3 signals, which provide a high cadence global measurement proportional to the voltage induced by changes in poloidal magnetic flux. Specifically, we examine how the time interval between pairs of successive ELMs is linked to the time-evolving phase of the full flux loop signals. Each ELM produces a clear early pulse in the full flux loop signals, whose peak time is used to condition our analysis. The arrival time of the following ELM, relative to this pulse, is found to fall into one of two categories: (i) prompt ELMs, which are directly paced by the initial response seen in the flux loop signals; and (ii) all other ELMs, which occur after the initial response of the full flux loop signals has decayed in amplitude. The times at which ELMs in category (ii) occur, relative to the first ELM of the pair, are clustered at times when the instantaneous phase of the full flux loop signal is close to its value at the time of the first ELM

Biased perception and recall of reassurance in medical patients

Objectives. We tested the hypothesis that compared with patients with low health anxiety those with high health anxiety would perceive and recall reassurance given by a physician as less reassuring than the physician reported giving. Design. A quasi-experimental repeated measures design; three time periods (immediate, one month and one year pose-consultation) in three groups of patients (total N = 50) defined by a ternary split on a questionnaire. Methods. Patients' health anxiety was measured prior to gastroscopic investigation and consultation with a physician for unexplained symptoms. All the investigations were negative for serious pathology. Immediately after consultation the physician and patients rated the given and perceived reassurance message on a five-point scale describing the probability of there being something seriously wrong. Patients repeated their ratings at one month and one year. Results. Patients in the high-health anxiety group were more likely to recall the reassurance given as less certain that there was nothing seriously wrong with them than were either the low or medium groups immediately pose-consultation. This difference persisted after one month but not one year later. Conclusions. These data provide preliminary support for the hypothesis that high health anxiety may bias the perception and recall of reassurance-related information

Responses of consecutive patients to reassurance after gastroscopy: results of self administered questionnaire survey

Objective: To study the time course and prediction of responses to reassurance after gastroscopy showing no serious illness. Design: Selection of consecutive patients were assessed before gastroscopy, immediately after reassurance, and at follow up at 24 hours, 1 week, 1 month, and 1 year. Responses of subgroups of patients identified as high, medium, and low health anxiety by the health anxiety questionnaire were analysed. Setting: Endoscopy clinic in a general hospital. Intervention: Oral reassurance that there was "nothing seriously wrong." Subjects: One consultant physician and 60 patients aged 18-74 referred for gastroscopy. Main outcome measures: Physician's and patients' ratings of the extent of the reassurance and patients' ratings of their anxiety about their health and of their illness belief. Results: There was good agreement between the patients and the physician about whether reassurance had been given. Health anxiety and illness belief decreased markedly after reassurance. Patients with high health anxiety showed a significant resurgence in their worry and illness belief at 24 hours and 1 week, and these levels were maintained at 1 month and 1 year later. Patients with medium levels of health anxiety showed a reduction in worry and illness belief after reassurance, and this was generally maintained during follow up. Patients with low health anxiety maintained low levels of health worry and illness belief throughout the study. Partial correlation analyses showed that the levels of worry and illness belief after reassurance were predicted by the health anxiety questionnaire. This measure also had predictive value beyond that of a measure of general anxiety. Conclusions: Medical reassurance results in a reduction of worry about health and of illness belief, but this may be very short term. Measurable individual differences in health anxiety can be used to predict the response to reassurance

Temporal evaluation of methionine synthase and related metabolites in the MAC15A mouse adenocarcinoma animal mode.l

NoMethionine dependence is unique to cancer cells and defined as the inability to grow in a methionine-deprived environment even if supplemented with the metabolic precursor homocysteine. Cobalamin-dependent methionine synthase (MS) catalyses the formation of methionine and tetrahydrofolate from homocysteine and methyltetrahydrofolate, thus linking the methionine and folate pathways. The apparent altered methionine metabolism in methionine-dependent cancer cells suggests a role for MS, although results to date are conflicting. We have analysed key metabolites of the MS-associated transmethylation, transsulphuration and folate pathways of the methionine-dependent MAC15A tumour model as a function of tumour progression over a 10-day period. MS activity increased 2-fold from day I to day 10. Cysteine, homocysteine, S-adenosylmethionine and S-adenosylhomocysteine levels in tumour cytosolic fractions decreased as a function of tumour progression. Plasma cysteine levels also decreased, whilst the distribution of folates in erythrocytes was altered, with a maximum increase in methyltetrahydrofolate observed by day 5. The increasing MS activity and decreasing cysteine levels suggest an increasing methionine requirement by the tumour, whilst the induction of enzyme activity indicates that MS is not defective in the methionine-dependent MAC15A tumour. The decrease in tumour S-adenosylmethionine and S-adenosylhomocysteine levels suggests that methionine is required for some function other than cellular methylation, e.g., incorporation into protein. Overall, the results support a theory of methionine conservation in response to tumour growth, where the methionine-dependent MAC15A tumour has a higher than normal methionine requirement

Impact of nitrogen seeding on confinement and power load control of a high-triangularity JET ELMy H-mode plasma with a metal wall

This paper reports the impact on confinement and power load of the high-shape 2.5MA ELMy H-mode scenario at JET of a change from an all carbon plasma facing components to an all metal wall. In preparation to this change, systematic studies of power load reduction and impact on confinement as a result of fuelling in combination with nitrogen seeding were carried out in JET-C and are compared to their counterpart in JET with a metallic wall. An unexpected and significant change is reported on the decrease of the pedestal confinement but is partially recovered with the injection of nitrogen.Comment: 30 pages, 16 figure