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

Quantitative description of Listeria monocytogenes inactivation kinetics with temperature and water activity as the influencing factors; model prediction and methodological validation on dynamic data

International audienceThe microbial evolution in foods over time is governed by process and storage conditions, and product characteristics. Mathematical models that accommodate the effect of both process temperature and product water activity on the microbial inactivation are studied in this research. Explicitly, models based on Arrhenius, response surface and Bigelow type relationships are developed and evaluated. The Bigelow type model revealed to be the most suitable. Experiments with macerated potato inoculated with Listeria monocytogenes were used to estimate associated inactivation parameters. The inactivation parameters, Asym D60 = 1.79 min, z = 7.11° and zaw = 0.23 were estimated and could be interpreted microbiologically. The parameter estimation step of the selected model was further developed by adding to it a bias factor and incorporating more microbiological information. At a final step, the complete identified model was used to predict the inactivation kinetics of L. monocytogenes under surface dry heating conditions at holding temperatures of 90 and 100 °C and lowering aw values. The confrontation of model predictions with the corresponding dynamic experimental data worked as a validation step. In summary, the induced heat resistance of L. monocytogenes due to the decreasing aw is an important microbiological phenomenon expressed through the estimation of the inactivation parameter zaw

A Randomised Phase II Trial to Evaluate the Feasibility of Radiotherapy Dose Escalation, Facilitated by Intensity-Modulated Arc Radiotherapy Techniques, in High-Risk Neuroblastoma

BACKGROUND AND PURPOSE: For high-risk neuroblastoma, planning target volume coverage is often compromised to respect adjacent kidney tolerance. This trial investigated whether intensity-modulated arc radiotherapy techniques (IMAT) could facilitate dose escalation better than conventional techniques.MATERIALS AND METHODS: Children with high-risk abdominal neuroblastoma referred for radiotherapy to the primary tumour site and involved regional lymph nodes were randomised to receive either standard dose (21 Gy in 14 fractions) or escalated dose (36 Gy in 24 fractions) radiotherapy. Dual planning with both a conventional anterior-posterior parallel opposed pair radiotherapy technique and an IMAT technique was performed. The quality of target volume and organ-at-risk delineation, and dosimetric plans, were externally reviewed. Dosimetric parameters were used to judge the superior technique for treatment. This feasibility trial was not powered to detect improvement in outcome with dose escalation.RESULTS: Between 2017 and 2020, 50 patients were randomised and dual-planned. The IMAT technique was judged more favourable in 48 patients. In all patients randomised to receive 36 Gy, IMAT would have permitted delivery of the full dose (median D50% 36.0 Gy, inter-quartile range 36.0-36.1 Gy) to the target volume, whereas dose compromise would have been required with conventional planning (median D50% 35.6 Gy, inter-quartile range 28.7-35.9 Gy).CONCLUSION: IMAT facilitates safe dose escalation to 36 Gy in patients receiving radiotherapy for neuroblastoma. The value of dose escalation is now being evaluated in a current prospective phase III randomised trial.</p

Monitoring SARS-CoV-2 in municipal wastewater to evaluate the success of lockdown measures for controlling COVID-19 in the UK

SARS-CoV-2 and the resulting COVID-19 pandemic represents one of the greatest recent threats to human health, wellbeing and economic growth. Wastewater-based epidemiology (WBE) of human viruses can be a useful tool for population-scale monitoring of SARS-CoV-2 prevalence and epidemiology to help prevent further spread of the disease, particularly within urban centres. Here, we present a longitudinal analysis (March-July 2020) of SARS-CoV-2 RNA prevalence in sewage across six major urban centres in the UK (total population equivalent 3 million) by q(RT-)PCR and viral genome sequencing. Our results demonstrate that levels of SARS-CoV-2 RNA generally correlated with the abundance of clinical cases recorded within the community in large urban centres, with a marked decline in SARS-CoV-2 RNA abundance following the implementation of lockdown measures. The strength of this association was weaker in areas with lower confirmed COVID-19 case numbers. Further, sequence analysis of SARS-CoV-2 from wastewater suggested that multiple genetically distinct clusters were co-circulating in the local populations covered by our sample sites, and that the genetic variants observed in wastewater reflected similar SNPs observed in contemporaneous samples from cases tested in clinical diagnostic laboratories. We demonstrate how WBE can be used for both community-level detection and tracking of SARS-CoV-2 and other virus' prevalence, and can inform public health policy decisions. Although, greater understanding of the factors that affect SARS-CoV-2 RNA concentration in wastewater are needed for the full integration of WBE data into outbreak surveillance. In conclusion, our results lend support to the use of routine WBE for monitoring of SARS-CoV-2 and other human pathogenic viruses circulating in the population and assessment of the effectiveness of disease control measures