Applications of control theory

Applications of control theory are considered in the areas of decoupling and wake steering control of submersibles, a method of electrohydraulic conversion with no moving parts, and socio-economic system modelling

Electrochemical Solutions for Advanced Life Support

The Oxygen Generating Assembly (OGA) on-board the International Space Station (ISS) employs a polymer electrolyte membrane (PEM) water electrolysis cell stack to electrochemically dissociate water into its two components oxygen and hydrogen. Oxygen is provided to the cabin atmosphere for crew respiration while the hydrogen is delivered to a carbon dioxide reduction system to recover oxygen as water. The design of the OGA evolved over a number of years to arrive at the system solution that is currently operational on ISS. Future manned missions to space will require advanced technologies that eliminate the need for resupply from earth and feature in-situ resource utilization to sustain crew life and to provide useful materials to the crew. The architects planning such missions should consider all potential solutions at their disposal to arrive at an optimal vehicle solution that minimizes crew maintenance time, launch weight, installed volume and energy consumption demands. Skyre is developing new technologies through funding from NASA, the Department of Energy, and internal investment based on PEM technology that could become an integral part of these new vehicle solutions. At varying stages of Technology Readiness Level (TRL) are: an oxygen concentrator and compressor that can separate oxygen from an air stream and provide an enriched oxygen resource for crew medical use and space suit recharge without any moving parts in the pure oxygen stream; a regenerative carbon dioxide removal system featuring a PEM-based sorbent regenerator; a carbon dioxide reduction system that electrochemically produces organic compounds that could serve as fuels or as a useful intermediary to more beneficial compounds; and an electrochemical hydrogen separator and compressor for hydrogen recycle. The technical maturity of these projects is presented along with pertinent performance test data that could be beneficial in future study efforts

The prevalence of smoking and the knowledge of smoking hazards and smoking cessation strategies among hiv positive patients in johannesburg, south africa

Background: While the detrimental effects of smoking among HIV positive patients have been well documented, there is a paucity of data regarding cigarette smoking prevalence among these patients in South Africa. Objectives: To establish the frequency, demographics, and knowledge of harmful effects and of smoking cessation strategies among HIV-positive patients in Johannesburg, South Africa. Methods: A prospective cross-sectional survey, using a structured questionnaire interview, of HIV-positive patients attending the HIV Clinic at the Charlotte Maxeke Johannesburg Academic Hospital between 1 July 2011 and 31 October 2011. Results: Of 207 HIV positive patients attending an ARV roll-out clinic, 31 (15%) were current smokers (23% of the males and 7.5% of the females) and a further 45 (21.7%) were ex-smokers. Most of the current smokers (30/31 patients) indicated their wish to quit smoking, and among the group as a whole most patients were aware of the general (82.5%) and HIV-related (77.8%) risks of smoking and of methods of quitting smoking. Despite this, however, most (61.8%) were not aware of whom they could approach for assistance and advice. Conclusions: Given the relatively high prevalence of current and ex-smokers amongst HIV positive patients there is a need for the introduction of smoking cessation strategies and assistance at HIV-rollout clinics in South Africa

Amplitude dependent frequency, desynchronization, and stabilization in noisy metapopulation dynamics

The enigmatic stability of population oscillations within ecological systems is analyzed. The underlying mechanism is presented in the framework of two interacting species free to migrate between two spatial patches. It is shown that that the combined effects of migration and noise cannot account for the stabilization. The missing ingredient is the dependence of the oscillations' frequency upon their amplitude; with that, noise-induced differences between patches are amplified due to the frequency gradient. Migration among desynchronized regions then stabilizes a "soft" limit cycle in the vicinity of the homogenous manifold. A simple model of diffusively coupled oscillators allows the derivation of quantitative results, like the functional dependence of the desynchronization upon diffusion strength and frequency differences. The oscillations' amplitude is shown to be (almost) noise independent. The results are compared with a numerical integration of the marginally stable Lotka-Volterra equations. An unstable system is extinction-prone for small noise, but stabilizes at larger noise intensity

Research on the Geography of Agricultural Change: Redundant or Revitalized?

Future research directions for agricultural geography were the subject of debate in Area in the late 1980s. The subsequent application of political economy ideas undoubtedly revived interest in agricultural research. This paper argues that agricultural geography contains greater diversity than the dominant political economy discourse would suggest. It reviews ‘other’ areas of agricultural research on policy, post-productivism, people, culture and animals, presenting future suggestions for research. They should ensure that agricultural research continues revitalized rather than redundant into the next millennium

A combined in vitro/in silico approach to identifying off-target receptor toxicity

Many xenobiotics can bind to off-target receptors and cause toxicity via the dysregulation of downstream transcription factors. Identification of subsequent off-target toxicity in these chemicals has often required extensive chemical testing in animal models. An alternative, integrated in vitro/in silico approach for predicting toxic off-target functional responses is presented to refine in vitro receptor identification and reduce the burden on in vivo testing. As part of the methodology, mathematical modelling is used to mechanistically describe processes that regulate transcriptional activity following receptor-ligand binding informed by transcription factor signalling assays. Critical reactions in the signalling cascade are identified to highlight potential perturbation points in the biochemical network that can guide and optimise additional in vitro testing. A physiologically-based pharmacokinetic model provides information on the timing and localisation of different levels of receptor activation informing whole-body toxic potential resulting from off-target binding

Dietary strategies for remission of type 2 diabetes: A narrative review

Type 2 diabetes (T2DM) is a growing health issue globally, which, until recently, was considered to be both chronic and progressive. Although having lifestyle and dietary changes as core components, treatments have focused on optimising glycaemic control using pharmaceutical agents. With data from bariatric surgery and, more recently, total diet replacement (TDR) studies that have set out to achieve remission, remission of T2DM has emerged as a treatment goal. A group of specialist dietitians and medical practitioners was convened, supported by the British Dietetic Association and Diabetes UK, to discuss dietary approaches to T2DM and consequently undertook a review of the available clinical trial and practice audit data regarding dietary approaches to remission of T2DM. Current available evidence suggests that a range of dietary approaches, including low energy diets (mostly using TDR) and low carbohydrate diets, can be used to support the achievement of euglycaemia and potentially remission. The most significant predictor of remission is weight loss and, although euglycaemia may occur on a low carbohydrate diet without weight loss, which does not meet some definitions of remission, it may rather constitute a ‘state of mitigation’ of T2DM. This technical point may not be considered as important for people living with T2DM, aside from that it may only last as long as the carbohydrate restriction is maintained. The possibility of actively treating T2DM along with the possibility of achieving remission should be discussed by healthcare professionals with people living with T2DM, along with a range of different dietary approaches that can help to achieve this