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Atmospheric plasma discharges are finding increased applications in addressing environmental challenges including water purification, chemical synthesis and biotechnology. An effective means of interfacing the reactivity of plasma gas discharges with liquids is needed to enhance liquid phase chemical reactions. Plasma discharges in bubbles has been considered as an innovative solution for achieving this goal potentially offering electrically driven, sustainable chemistry with low energy consumption and the unique benefit of maintaining a large volume discharge under the liquid surface. Here we provide a concise review on the state-of-art for research on plasma-bubble interactions and a perspective for future research.

Trans-vaginal natural orifice transluminal endoscopic surgery (vNOTES) is a recently popularised minimally invasive surgical procedure, aimed at minimising abdominal wall scars and improving pain and patient recovery times. Although vNOTES has been studied in the context of post-operative pain and cosmesis, women’s acceptance of the technique has only been cursorily examined. In this survey-based observational study, we assessed the acceptability of this technique among a cohort of Middle Eastern women. A cohort of 175 Middle Eastern women were surveyed using a 13-item questionnaire at a single gynaecology centre. The survey used was a translated version of a questionnaire from a previous study (1) and comprised open-response, five-point Likert Scale and agree-disagree items. Among 175 Middle Eastern women participated in this study most of them holding neutral view on abdominal and gynaecological procedures via vagina. 47% of participants were unsure regarding the effect of surgery via vagina on their sexual function. Although 61% of the participants showed no preference towards vNOTES over laparoscopic cholecystectomy, more than half of them indicated preference if vNOTES shown to be as effective and safe as laparoscopic cholecystectomy. The gender of the surgeon was shown to have no influence on the perspectives of the majority of participants to undergo vNOTES. vNOTES may hold value for women who have conservative upbringing and/or value cosmesis. This study provides information regarding Middle Eastern women’s perspectives on vNOTES, which may be of considerable clinical use as the popularity of this surgical technique continues to increase.

Trans-vaginal natural orifice transluminal endoscopic surgery (vNOTES) is a recently popularised minimally invasive surgical procedure, aimed at minimising abdominal wall scars and improving pain and patient recovery times. Although vNOTES has been studied in the context of post-operative pain and cosmesis, women's acceptance of the technique has only been cursorily examined. In this survey-based observational study, we assessed the acceptability of this technique among a cohort of Middle Eastern women.A cohort of 175 Middle Eastern women were surveyed using a 13-item questionnaire at a single gynaecology centre. The survey used was a translated version of a questionnaire from a previous study (1) and comprised open-response, five-point Likert Scale and agree-disagree items.Among 175 Middle Eastern women participated in this study most of them holding neutral view on abdominal and gynaecological procedures via vagina. 47% of participants were unsure regarding the effect of surgery via vagina on their sexual function. Although 61% of the participants showed no preference towards vNOTES over laparoscopic cholecystectomy, more than half of them indicated preference if vNOTES shown to be as effective and safe as laparoscopic cholecystectomy. The gender of the surgeon was shown to have no influence on the perspectives of the majority of participants to undergo vNOTES.vNOTES may hold value for women who have conservative upbringing and/or value cosmesis. This study provides information regarding Middle Eastern women's perspectives on vNOTES, which may be of considerable clinical use as the popularity of this surgical technique continues to increase.

The synergistic effect of combining low and high radio frequency electric fields processing on Escherichia coli (E. coli) inactivation in liquid food was investigated. We show that by processing with low frequency (LF) at 12.5 kV cm−1 and 40 °C, followed by high frequency (HF) at 2.1 kV cm−1 and 65 °C, a synergistic effect on E. coli inactivation in saline water was achieved yielding approx. 5 log reduction and metabolic activity of 8.01 ± 4.34%. When similar treatment was applied to cranberry juice, an inactivation of 5.13 ± 0.21 log10 was achieved. Electron microscopy revealed that when both LF and HF treatments were applied alone, they disrupted the bacterial cell wall ultrastructure, with HF treatment additionally degrading cytoplasmic components. The sequential combination of LF and HF processes led to greater ultrastructural damage of E. coli as indicated by the observed perforation and rupture of the cell walls as well as leakage of cytoplasmic content.

The effect of modifying the geometrical configuration of a co-linear chamber to improve its performance and to increase the microbial inactivation was investigated numerically and validated experimentally. In non-thermal radio frequency electric fields (RFEF) processing, co-linear chambers exhibit low tendency to dielectric breakdown and arcing, especially in liquid food products with high electrical conductivities, but they show low energy efficiency and poor uniformity of processing conditions. Accordingly, a standard co-linear chamber (C1) with 1 mm of length and 3 mm of diameter was selected. The chamber included a gap between the end of electrodes and the treatment zone, as well as a diameter contraction at that zone. The geometry of the standard co-linear chamber was modified by removing the recirculation/stagnation zones adding stainless steel tubes (C2), as well as through the additional insertion of stainless steel mesh to contain the electric field within the treatment zone (C3). These configurations were evaluated numerically using COMSOL Multiphysics modelling. The model was validated by comparing experimental measurements of outlet temperature and power consumption with the model predictions. The numerical study showed that C3 exhibited a more uniformly distributed electric field and temperature profiles as well as higher velocities and turbulent kinetic energy that were also more evenly distributed within the treatment zone, compared to other configurations. In experimental studies, C3 achieved the highest microbial inactivation at constant values of peak voltage, electric field strength, and energy levels. Furthermore, C3 showed the most energy efficiency among the three geometrical configurations. Industrial relevance As an alternative to thermal processing, radio frequency electric fields (RFEF) processing needs to ensure the microbial safety of the food products in an energy-efficient manner due to the challenges on controlling Joule heating, which can lead to arcing and the dielectric breakdown of the treatment chamber. This can be achieved by designing treatment chambers that can enclose the electric field within the treatment zone while providing a more evenly distributed electric field, hydrodynamic and temperature profiles within that zone. This study proves that the geometrical configuration of co-linear chambers can be altered to minimize the energy consumption while maximizing the microbial inactivation. The findings can be used for scaling up and advancing the industrial application of RFEF technology for food processing.

The inactivation of Escherichia coli inoculated in cranberry juice by processing with radio frequency electric fields was studied. E. coli ATCC 35218 was chosen among three non-pathogenic strains based on its ability to survive in low pH cranberry juice. Studies were conducted by measuring the survival population when changing the electric field strength between 2.2 and 13.2 kV cm−1, number of treatment stages from 1 to 6 and flow rates between 13 and 25 L h−1 at moderate temperatures of 20, 30 and 40 °C. A minimum inactivation of 5-log reduction, as requested by the Food and Drug Administration (FDA), can be achieved by increasing the number of treatment stages, temperature or both. At 40 °C and 6 treatment stages, 6.57 ± 0.02 log CFU ml−1 reduction in the initial population of E. coli (ATCC 35218) was obtained. At a constant electric field, increasing the temperature produced higher microbial inactivation, consuming lower radio frequency energy input, than increasing the number of treatment stages. Furthermore, a primary model that accounts for the combined effect of time and electric field is proposed. The model represented the sigmoidal curve composed of shoulder, log-linear and tailing sections as observed when changing electric fields. A secondary model that accounts for the effect of temperature and flow rate on the primary model constants is also proposed. The combined primary and secondary models were found to fit the data well with a high coefficient of determination (R2 = 0.965). The proposed model can be extended to kinetic models for pulsed electric fields.

Ultrasound has been investigated as a new technique for brewing coffee. A two-level factorial experimental design was conducted to identify the effects of ultra-sonication on the extraction of coffee components during ultrasonically-assisted coffee brewing. Different brews were produced by aqueous extraction from roasted ground coffee beans with sonication, and without it as a control, by varying coffee concentration (5% and 10% w/w), temperature (25 and 50 °C) and sonication time (1 and 5 min). These brews were tested for antioxidant capacity (using the ABTS assay), caffeine and triglycerides (using quantitative NMR spectroscopy) and specific aroma/flavour volatiles (using headspace SPME-GC-MS). Additional observations of colour, foaming, body and flavour were also reported. Ultrasound was found to significantly increase the extraction of caffeine, triglycerides and several of the key volatile compounds from coffee, although it did appear to decrease the concentration of antioxidants over the controls, especially with longer time and higher temperature. Furthermore, all the sonicated samples exhibited a lighter caramel colour and lower foam formation which were attributed to their higher triglyceride content. The increased concentration of triglycerides and volatiles were by far the most outstanding responses.