Detonation Physics-Based Modelling & Design of a Rotating Detonation Engine

A rotating detonation engine (RDE) is a new, more thermodynamically efficient, propulsion concept that replaces the traditional constant pressure combustion mechanism found in all currently used rockets and power generation devices. The constant pressure combustion is replaced by a detonation wave: a coupled shock-flame complex propagating at speeds of up to 2-3 km/s and generating combustion products at pressures 5-10 times the initial reactant pressure. This pressure gain through the combustion process leads to more compact, simpler devices that no longer require (or depend less upon) initial reactant precompression. Detonation-based cycles also have the added advantage of being theoretically more thermodynamically efficient than their constant pressure combustion counterparts. As such, RDEs have become increasingly popular in the propulsion research community, although there is still a lack of understanding in the underlying physics which govern their operability, though the existence of a minimum mass flow rate limit for stable operation has been observed. To help engineers and researchers design an RDE, a model was developed which combines geometric properties, 1D isentropic flow, and detonation physics to predict the stable operating bounds of an RDE. An engine testing facility was also constructed in collaboration with McGill University to test RDEs and confirm the performance of the prediction model developed

Spatio-temporal analyses of impacts of multiple climatic hazards in a savannah ecosystem of Ghana

Ghana’s savannah ecosystem has been subjected to a number of climatic hazards of varying severity. This paper presents a spatial, time-series analysis of the impacts of multiple hazards on the ecosystem and human livelihoods over the period 1983-2012, using the Upper East Region of Ghana as a case study. Our aim is to understand the nature of hazards (their frequency, magnitude and duration) and how they cumulatively affect humans. Primary data were collected using questionnaires, focus group discussions, in-depth interviews and personal observations. Secondary data were collected from documents and reports. Calculations of the standard precipitation index (SPI) and crop failure index used rainfall data from 4 weather stations (Manga, Binduri, Vea and Navrongo) and crop yield data of 5 major crops (maize, sorghum, millet, rice and groundnuts) respectively. Temperature and windstorms were analysed from the observed weather data. We found that temperatures were consistently high and increasing. From the SPI, drought frequency varied spatially from 9 at Binduri to 13 occurrences at Vea; dry spells occurred at least twice every year and floods occurred about 6 times on average, with slight spatial variations, during 1988-2012, a period with consistent data from all stations. Impacts from each hazard varied spatio-temporally. Within the study period, more 70% of years recorded severe crop losses with greater impacts when droughts and floods occur in the same year, especially in low lying areas. The effects of crop losses were higher in districts with no/little irrigation (Talensi, Nabdam, Garu-Tempane, Kassena-Nankana East). Frequency and severity of diseases and sicknesses such as cerebrospinal meningitis, heat rashes, headaches and malaria related to both dry and wet conditions have increased steadily over time. Other impacts recorded with spatio-temporal variations included destruction to housing, displacement, injury and death of people. These impacts also interacted. For example, sicknesses affected labour output; crop losses were blamed for high malnutrition; and reconstruction of properties demanded financial resources largely from sale of agricultural produce. These frequent impacts and their interactions greatly explain the persistent poverty in the area

Advancing the research agenda on food systems governance and transformation

The food systems upon which humanity depends face multiple interdependent environmental, social and economic threats in the 21st Century. Yet, the governance of these systems, which determines to a large extent the ability to adapt and transform in response to these challenges, is underresearched. This perspective piece synthesises the findings of two recent reviews of food systems governance and transformations and proposes a comprehensive research agenda for the coming years. These reviews highlight the influence of governance on food systems, methodological obstacles to explaining the effectiveness of governance in realising food sustainability, and conditions that have historically supported food system transformations. We argue that the following steps are key to improving our knowledge of the role of governance in food systems: (1) developing more comparable research designs for building generalisable explanations of the governance elements that are most effective in realising food systems goals; (2) using the lens of polycentricity to help disentangle complex governance networks; (3) giving greater attention to the conditions and pre-conditions associated with historical food system transformations; (4) identifying adaptations that strengthen or weaken path dependency; and, (5) focusing research on how transformations can be supported by institutions that facilitate collective action and stakeholder agency

Effect of angiotensin-converting enzyme inhibitor and angiotensin receptor blocker initiation on organ support-free days in patients hospitalized with COVID-19

IMPORTANCE Overactivation of the renin-angiotensin system (RAS) may contribute to poor clinical outcomes in patients with COVID-19. Objective To determine whether angiotensin-converting enzyme (ACE) inhibitor or angiotensin receptor blocker (ARB) initiation improves outcomes in patients hospitalized for COVID-19. DESIGN, SETTING, AND PARTICIPANTS In an ongoing, adaptive platform randomized clinical trial, 721 critically ill and 58 non–critically ill hospitalized adults were randomized to receive an RAS inhibitor or control between March 16, 2021, and February 25, 2022, at 69 sites in 7 countries (final follow-up on June 1, 2022). INTERVENTIONS Patients were randomized to receive open-label initiation of an ACE inhibitor (n = 257), ARB (n = 248), ARB in combination with DMX-200 (a chemokine receptor-2 inhibitor; n = 10), or no RAS inhibitor (control; n = 264) for up to 10 days. MAIN OUTCOMES AND MEASURES The primary outcome was organ support–free days, a composite of hospital survival and days alive without cardiovascular or respiratory organ support through 21 days. The primary analysis was a bayesian cumulative logistic model. Odds ratios (ORs) greater than 1 represent improved outcomes. RESULTS On February 25, 2022, enrollment was discontinued due to safety concerns. Among 679 critically ill patients with available primary outcome data, the median age was 56 years and 239 participants (35.2%) were women. Median (IQR) organ support–free days among critically ill patients was 10 (–1 to 16) in the ACE inhibitor group (n = 231), 8 (–1 to 17) in the ARB group (n = 217), and 12 (0 to 17) in the control group (n = 231) (median adjusted odds ratios of 0.77 [95% bayesian credible interval, 0.58-1.06] for improvement for ACE inhibitor and 0.76 [95% credible interval, 0.56-1.05] for ARB compared with control). The posterior probabilities that ACE inhibitors and ARBs worsened organ support–free days compared with control were 94.9% and 95.4%, respectively. Hospital survival occurred in 166 of 231 critically ill participants (71.9%) in the ACE inhibitor group, 152 of 217 (70.0%) in the ARB group, and 182 of 231 (78.8%) in the control group (posterior probabilities that ACE inhibitor and ARB worsened hospital survival compared with control were 95.3% and 98.1%, respectively). CONCLUSIONS AND RELEVANCE In this trial, among critically ill adults with COVID-19, initiation of an ACE inhibitor or ARB did not improve, and likely worsened, clinical outcomes. TRIAL REGISTRATION ClinicalTrials.gov Identifier: NCT0273570

Potential for cold storage of horticultural commodities in tropical countries

An evaluation of the use of short-term cold storage of tomatoes to tide over the cyclical market glut of horticultural products was conducted in Coimbatore, Tamil Nadu, India. Farmers stored their harvest at a rental commercial cold-storage facility in the city and at an experimental cold store at the Tamil Nadu Agricultural University in Coimbatore. The goal was to study the storage characteristics of the produce as well as to assess the economic benefits of adopting such an intervention. The temperature and relative humidity conditions at both locations and the fate of the produce were monitored. The proportion of marketable produce diminished significantly as the storage period increased, with major losses occurring due to microbial damage. Differences in the air conditions at the locations did not have a significant effect on the storage-related losses of produce. Economic analysis showed that short-term cold storage would not aid farmers unless measures were taken to reduce the microbiological losses during postharvest handling.Une évaluation d'entreposage de tomates à court terme a été effectuée à Coimbatore, dans l'état du Tamil Nadu en Inde, dans le but d'aider les fermiers à pallier la saturation cyclique du marché des fruits et légumes frais. Des fermiers ont entreposé leur récolte de tomates dans un entrepôt frigorifique commercial situé dans la ville, ainsi que dans un entrepôt frigorifique expérimental situé dans le Tamil Nadu Agricultural University dans la même ville indienne. Le but de l'expérience était d'étudier les caractéristiques d'entreposage du produit, ainsi que d'évaluer les bénéfices économiques liés à l'adoption d'une telle intervention. La température, l'humidité relative et le sort des produits horticoles ont été surveillés. Avec l'augmentation des temps d'entreposage, la proportion des fruits frais ayant une valeur marchande a baissé considérablement; la plupart des pertes était due à des infections microbiennes. Les différences dans les conditions ambiantes des deux entrepôts n'ont pas eu d'effet considérable sur les pertes de fruits frais dues à l'entreposage. Une analyse économique a démontré que l'entreposage à court terme n'aidera pas les fermiers à moins que des mesures supplémentaires soient adoptées afin de réduire les pertes microbiennes durant les manipulations post-récoltes