Zero phase sequence voltage injection for the alternate arm converter

The Alternate Arm Converter (AAC) is a voltage source converter being developed as an alternative to the Modular Multilevel Converter (MMC) for HVDC power transmission and reactive power compensation. Each Arm of the converter contains high voltage series IGBT Director Switches and full-bridge cells, which enables the VSC to ride through AC and DC network faults. This paper describes how the AAC can be optimised by modulating the converter terminal voltages with zerophase sequence triplen harmonic components. The optimisation reduces the ratio of the number of the full-bridge cells compared to the simpler Director Switches which offers a valuable improvement in footprint and efficiency

The variety, popularity and nutritional quality of tuck shop items available for sale to primary school learners in Pietermaritzburg, South Africa

Objectives: To determine the variety, popularity and nutritional quality of the food and beverages sold to primary school pupils. Method: A cross-sectional tuck shop survey. Nutritional analyses were conducted using the South African Medical Research Council Foodfinder 3 for Windows® software. Eleven mixed-race, well-resourced, government primary schools were studied in Pietermaritzburg, South Africa. Subjects included tuck shop managers from each school. Results: Savoury pies were the most popular lunch item for all learners for both breaks (n = 5, 45%, and n = 3, 27.3%), selling the most number of units (43) per day at eight schools (72.7%). Iced popsicles were sold at almost every school, ranked as the cheapest beverage, and also sold the most number of units (40.7). Healthy beverages sold included canned fruit juice and water, while healthy snacks consisted of dried fruit, fruit salad, bananas, yoghurt and health muffins. The average healthy snack contained almost half the kilojoules of the unhealthy counterpart (465 kJ vs. 806 kJ). Nutritional analyses of the healthy lunch options revealed total fat contents that exceeded the Dietary Reference Intake and South African recommended limits. Perceived barriers to stocking healthy items included cost and refrigeration restrictions. Conclusion: School tucks shops are selling products that encourage an unhealthy lifestyle, thereby promoting the obesity epidemic. Extensive consultation is required among dietitians, school principals and privatised tuck shop managers to overcome barriers to stocking healthy food in tuck shops.Keywords: school feeding, tuck shop, Pietermaritzburg, South Afric

Tuck-shop purchasing practices of Grade 4 learners in Pietermaritzburg and childhood overweight and obesity

Objectives: To determine the anthropometric characteristics of Grade 4 learners in relation to their tuck-shop purchasing practices.Design: A cross-sectional research design using a questionnaire that was administered to Grade 4 learners.Setting and subjects: Four well-resourced primary schools in Pietermaritzburg. The study included 311 Grade 4 learners.Outcome measures: Body mass index interpreted in relation to tuck-shop purchasing practices.Results: Fifty-six per cent of the sample were female (n = 173) and 44% were male (n = 138) learners. Twenty-seven per cent of the study sample was overweight (n = 83) and 27% was obese (n = 85). Eighty-six per cent of the learners (n = 266) made purchases from their school tuck shop. Twenty-two per cent did so at least three times per week (n = 58). Learners who bought from the tuck shop had a significantly higher body mass index compared to those who did not (p-value < 0.020). Learners who purchased from the tuck shop spent an average of R8.38 per day, a minimum of R1 and a maximum of R40 (± R5.39). The most popular reasons for visiting the tuck shop included: “This is my favourite thing to eat or drink” (66.5%, n = 177), and “I only have enough money to buy this item” (47%, n = 125). Conclusion: Poor tuck-shop purchasing practices may contribute to the development of childhood overweight and obesity in learners. Successful preventative strategies should focus on restricting the amount of unhealthy items that are available for sale, imposing spending limits and motivating learners to prioritise healthy food and beverage purchases.Keywords: childhood obesity, overweight, tuck-shop practices, body mass inde

An automated online instrument to quantify aerosol-bound reactive oxygen species (ROS) for ambient measurement and health-relevant aerosol studies

The adverse health effects associated with ambient aerosol particles have been well documented, but it is still unclear which aerosol properties are most important for their negative health impact. Some studies suggest the oxidative effects of particle-bound reactive oxygen species (ROS) are potential major contributors to the toxicity of particles. Traditional ROS measurement techniques are labour-intensive, give poor temporal resolution and generally have significant delays between aerosol sampling and ROS analysis. However, many oxidising particle components are reactive and thus potentially short-lived. Thus, a technique to quantify particle-bound ROS online would be beneficial to quantify also the short-lived ROS components. We introduce a new portable instrument to allow online, continuous measurement of particle-bound ROS using a chemical assay of 2$^\prime$7$^\prime$-dichlorofluorescein (DCFH) with horseradish peroxidase (HRP), via fluorescence spectroscopy. All components of the new instrument are attached to a containing shell, resulting in a compact system capable of automated continuous field deployment over many hours or days. From laboratory measurements, the instrument was found to have a detection limit of ~4 nmol [H$_2$O$_2$] equivalents per cubic metre (m$^3$) air, a dynamic range up to at least ~2000 nmol [H$_2$O$_2$] equivalents per m$^3$ air and a time resolution of ≤ 12 min. The instrument allows for ~16 h automated measurement if unattended and shows a fast response to changes in concentrations of laboratory-generated oxidised organic aerosol. The instrument was deployed at an urban site in London, and particulate ROS levels of up to 24 nmol [H$_2$O$_2$] equivalents per m$^3$ air were detected with PM$_{2.5}$ concentrations up to 28 µg m$^{−3}$. The new and portable Online Particle-bound ROS Instrument (OPROSI) allows fast-response quantification; this is important due to the potentially short-lived nature of particle-bound ROS as well as fast-changing atmospheric conditions, especially in urban environments. The instrument design allows for automated operation and extended field operation with twice-daily presence of an operator. As well as having sensitivity suitable for ambient level measurement, the instrument is also suitable at concentrations such as those required for laboratory and chamber toxicological studies.The authors would like to thank ERC (the European Research Council, grant no. 279405) for their funding of this study. Infrastructure at Marylebone Road was supported by NERC (the Natural Environment Research Council, Clearflo grant no. NE/H003231/1) and Defra (Department of Environment Food and Rural Affairs, contract AQ0643 Automatic London Network (2010-14) RMP 5442)

Measures for assessing practice change in medical practitioners

BACKGROUND: There are increasing numbers of randomised trials and systematic reviews examining the efficacy of interventions designed to bring about a change in clinical practice. The findings of this research are being used to guide strategies to increase the uptake of evidence into clinical practice. Knowledge of the outcomes measured by these trials is vital not only for the interpretation and application of the work done to date, but also to inform future research in this expanding area of endeavour and to assist in collation of results in systematic reviews and meta-analyses. METHODS: The objective of this review was to identify methods used to measure change in the clinical practices of health professionals following an intervention aimed at increasing the uptake of evidence into practice. All published trials included in a recent, comprehensive Health Technology Assessment of interventions to implement clinical practice guidelines and change clinical practice (n = 228) formed the sample for this study. Using a standardised data extraction form, one reviewer (SH), extracted the relevant information from the methods and/or results sections of the trials. RESULTS: Measures of a change of health practitioner behaviour were the most common, with 88.8% of trials using these as outcome measures. Measures that assessed change at a patient level, either actual measures of change or surrogate measures of change, were used in 28.8% and 36.7% of studies (respectively). Health practitioners' knowledge and attitudes were assessed in 22.8% of the studies and changes at an organisational level were assessed in 17.6%. CONCLUSION: Most trials of interventions aimed at changing clinical practice measured the effect of the intervention at the level of the practitioner, i.e. did the practitioner change what they do, or has their knowledge of and/or attitude toward that practice changed? Less than one-third of the trials measured, whether or not any change in practice, resulted in a change in the ultimate end-point of patient health status

Geometric invariant theory of syzygies, with applications to moduli spaces

We define syzygy points of projective schemes, and introduce a program of studying their GIT stability. Then we describe two cases where we have managed to make some progress in this program, that of polarized K3 surfaces of odd genus, and of genus six canonical curves. Applications of our results include effectivity statements for divisor classes on the moduli space of odd genus K3 surfaces, and a new construction in the Hassett-Keel program for the moduli space of genus six curves.Comment: v1: 23 pages, submitted to the Proceedings of the Abel Symposium 2017, v2: final version, corrects a sign error and resulting divisor class calculations on the moduli space of K3 surfaces in Section 5, other minor changes, In: Christophersen J., Ranestad K. (eds) Geometry of Moduli. Abelsymposium 2017. Abel Symposia, vol 14. Springer, Cha

The evolution of democratic peace in animal societies

\ua9 The Author(s) 2024.A major goal in evolutionary biology is to elucidate common principles that drive human and other animal societies to adopt either a warlike or peaceful nature. One proposed explanation for the variation in aggression between human societies is the democratic peace hypothesis. According to this theory, autocracies are more warlike than democracies because autocratic leaders can pursue fights for private gain. However, autocratic and democratic decision-making processes are not unique to humans and are widely observed across a diverse range of non-human animal societies. We use evolutionary game theory to evaluate whether the logic of democratic peace may apply across taxa; specifically adapting the classic Hawk-Dove model to consider conflict decisions made by groups rather than individuals. We find support for the democratic peace hypothesis without mechanisms involving complex human institutions and discuss how these findings might be relevant to non-human animal societies. We suggest that the degree to which collective decisions are shared may explain variation in the intensity of intergroup conflict in nature

An E7 Surprise

We explore some curious implications of Seiberg duality for an SU(2) four-dimensional gauge theory with eight chiral doublets. We argue that two copies of the theory can be deformed by an exactly marginal quartic superpotential so that they acquire an enhanced E7 flavor symmetry. We argue that a single copy of the theory can be used to define an E7-invariant superconformal boundary condition for a theory of 28 five-dimensional free hypermultiplets. Finally, we derive similar statements for three-dimensional gauge theories such as an SU(2) gauge theory with six chiral doublets or Nf=4 SQED.Comment: 27 page