Vortex dynamos

We investigate the kinematic dynamo properties of interacting vortex tubes. These flows are of great importance in geophysical and astrophysical fluid dynamics: for a large range of systems, turbulence is dominated by such coherent structures. We obtain a dynamically consistent 2(2)-(1)-dimensional velocity field of the form (u(x, y, t), upsilon(x, y, t), w(x, y, t)) by solving the z-independent Navier-Stokes equations in the presence of helical forcing. This system naturally forms vortex tubes via an inverse cascade. It has chaotic Lagrangian properties and is therefore a candidate for fast dynamo action. The kinematic dynamo properties of the flow are calculated by determining the growth rate of a small-scale seed field. The growth rate is found to have a complicated dependence on Reynolds number Re and magnetic Reynolds number Rm, but the flow continues to act as a dynamo for large Re and Rm. Moreover the dynamo is still efficient even in the limit Re much greater than Rm, providing Rm is large enough, because of the formation of coherent structures

Insect parasitoids : a Canadian perspective on their use for biological control of forest insect pests

Nous présentons un survol des programmes de lutte biologique envers les insectes forestiers en mettant l'accent sur des cas canadiens. Ces travaux de recherche sont examinés dans le contexte de la conservation, de l'introduction et de l'augmentation (par manipulation de l'environnement et lâchers inoculants et massifs) des ennemis naturels, et plus spécifiquement des parasitoïdes. Historiquement les études ont porté sur l'introduction de parasitoïdes exotiques pour la lutte aux insectes nuisibles introduits, un certain nombre de ces travaux ayant été fructueux. Des travaux plus récents ont consisté en des lâchers inoculants et massifs de parasitoïdes contre des insectes indigènes afin d'établir de nouvelles relations hôte-parasitoïde dans le but de réduire les populations d'insectes indésirables. Ces nouvelles techniques n'ont démontré que des résultats limités et les recherches se poursuivent dans cette voie. Les stratégies actuelles d'utilisation d'ennemis naturels sont le lâcher massif d'espèces indigènes contre des espèces nuisibles indigènes et la conservation des parasitoides indigènes par des applications sélectives d'herbicides et la gestion des forêts. Les prochaines avenues pour les programmes de lutte biologique incluront ces approches en plaçant l'accent sur les biotechnologies et la sélection génétique ou la manipulation de lignées recherchées pour les lâchers. Des études écologiques continues seront essentielles à l'obtention d'une meilleure compréhension des interactions entre ces parasitoïdes sélectionnés et les données forêt-arbre qui influenceront leur succès (interaction tritrophique). Ces données, à savoir la vigueur de l'arbre (résistance aux insectes), distribution spatiale et diversité, seront aussi visées pour la sélection afin d'améliorer l'impact des ennemis naturels des parasites dans l'environnement forestier.An overview of biological control programs against forest insect pests is presented with emphasis on Canadian case histories. The work is examined in the context of conservation, introduction, and augmentation (environmental manipulation and inoculative and inundative release) of insect natural enemies, specifically parasitoids. Historically, studies have concentrated on introductions of exotic parasitoids for control of introduced pests where a number of successes have been recorded. More recent work has entailed inoculative and inundative releases of parasitoids against native pests in an attempt to establish new host-parasitoid relationships to reduce pest populations. These have had limited success and are still being explored by Canadian researchers. Current strategies for using natural enemies are inundative release of native species against native pests and conservation of native parasitoids through selective insecticide timing and forest manipulation. Future directions in biological control programs will include these approaches with increased emphasis on biotechnology and the genetic selection or manipulation of 'desired strains' for release. Continued ecological studies will be essential to ensure a more complete understanding of the interaction between these 'selected parasitoids' and the forest/tree parameters which will influence their success (tri-trophic interactions). These parameters, such as tree vigour (pest resistance), spatial distribution and diversity, will also be targeted for selection to improve the effect of insect natural enemies in the forest environment

Postgerminative growth and lipid catabolism in oilseeds lacking the glyoxylate cycle

The glyoxylate cycle is regarded as essential for postgerminative growth and seedling establishment in oilseed plants. We have identified two allelic Arabidopsis mutants, icl-1 and icl-2, which lack the glyoxylate cycle because of the absence of the key enzyme isocitrate lyase. These mutants demonstrate that the glyoxylate cycle is not essential for germination. Furthermore, photosynthesis can compensate for the absence of the glyoxylate cycle during postgerminative growth, and only when light intensity or day length is decreased does seedling establishment become compromised. The provision of exogenous sugars can overcome this growth deficiency. The icl mutants also demonstrate that the glyoxylate cycle is important for seedling survival and recovery after prolonged dark conditions that approximate growth in nature. Surprisingly, despite their inability to catalyze the net conversion of acetate to carbohydrate, mutant seedlings are able to break down storage lipids. Results suggest that lipids can be used as a source of carbon for respiration in germinating oilseeds and that products of fatty acid catabolism can pass from the peroxisome to the mitochondrion independently of the glyoxylate cycle. However, an additional anaplerotic source of carbon is required for lipid breakdown and seedling establishment. This source can be provided by the glyoxylate cycle or, in its absence, by exogenous sucrose or photosynthesis

Grounded Theory: A guide for a new generation of researchers

Aim/Purpose Grounded Theory (GT) has grown and developed into several strands making its application all the more problematic, argumentative and remaining potentially as a research methodology to avoid when it comes to doctoral research, early-career research. Thus, the purpose of this paper is to revisit GT as a general approach and present an evolved and more considered step-by-step guide to conduct research using this methodology. A leadership development context is applied in this paper to examine how this methodology could work for a new generation of researchers, i.e., new to doctoral research or an early career researcher. Background Since its academic inception in the seminal text in 1967 (Glaser & Strauss, 1967), GT has emerged and developed to become a popular choice for researchers contemplating qualitative data approaches amongst a variety of subject backgrounds. However, the divergent development and criticized approaches within GT families can lead researchers to avoid such a research methodology. This can especially be the case within doctoral research or other early-career research. Indeed, a specific/explicit GT guideline or framework to assist doctoral students in conducting GT research does not currently exist. Methodology There is a general review of GT approaches followed by theoretical development of a framework and an applied doctoral example. Contribution The three evolved methods in GT research and the developed supporting author-designed three-phase research framework will contribute to two aspects. Firstly, the step-by-step guideline can reduce the sense of confusion within an area where criticisms and conflicting approaches exist. This will hopefully assist the next generation of GT researchers in conducting their research through detailed processes and applications. Secondly, there is arguably a need for more GT applications and evolvements to further enrich the body of knowledge that exists in this area and further support a diversity of subject research. Findings The authors outline numerous differences and similarities within divergent GT practices. By integrating Glaser’s four core principles and three evolved methods, the authors design a three-phase research framework that presents a transparent step-by-step guide. This framework attempts to mitigate criticisms within GT approaches whilst maintaining clarity, flexibility, depth, and rigour within a study. Recommendations for Practitioners Three GT evolvements (the two-step literature review method, two-step open-coding method, and two-step theory-constitute method) provides greater clarity within a rigorous author-designed three-phase research framework that demonstrates a transparent step-by-step guide. These techniques can encourage a new generation of GT researcher through confident and structured analytical techniques. Recommendation for Researchers We hope the presented framework and concise view of GT in action will inspire other doctoral students and new GT researchers to conduct GT research following an evolved GT framework. Impact on Society The debates and innovations around GT, like in this paper, are needed within a methodological society to keep the area contemporary and constantly evolving. Future Research The framework presented will need further testing beyond the parameters set out here. We hope future research can adopt the evolved GT techniques and procedures to enforce research quality overall and inspire further GT methodological developments

How to design and evaluate interventions to improve outcomes for patients with multimorbidity

Multimorbidity is a major challenge for patients and healthcare providers. The limited evidence of the effectiveness of interventions for people with multimorbidity means that there is a need for much more research and trials of potential interventions. Here we present a consensus view from a group of international researchers working to improve care for people with multimorbidity to guide future studies of interventions. We suggest that there is a need for careful consideration of whom to include, how to target interventions that address specific problems and that do not add to treatment burden, and selecting outcomes that matter both to patients and the healthcare system. Innovative design of these interventions will be necessary as many will be introduced in service settings and it will be important to ensure methodological rigour, relevance to service delivery, and generalizability across healthcare systems

Hydrate-phobic surfaces

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2011.Cataloged from PDF version of thesis.Includes bibliographical references (p. 25-27).Clathrate hydrate formation and subsequent plugging of deep-sea oil and gas pipelines represent a significant bottleneck for ultra deep-sea production. Current methods for hydrate mitigation focus on injecting thermodynamic or kinetic inhibitors into the flow, heating the pipe walls, or managing the flow of formed hydrates. These methods are expensive and energy intensive. An alternative approach involves reducing the adhesion of hydrates to surfaces, ideally to a low enough level that the force of flow detaches them and prevents plug formation. Systematic and quantitative studies of hydrate adhesion on smooth surfaces with varying energies were conducted. Surface energies were quantified using van Oss-Chaudhury-Good analysis of advancing and receding contact angles of polar and nonpolar fluids. The strengths of hydrate adhesion to these surfaces were measured using a custom-built testing apparatus, and greater than 75% reduction in adhesion strength of Tetrahydrofuran hydrate was achieved on treated surfaces compared with bare steel. This reduction is achievable on surfaces characterized by low Lewis acid, Lewis base, and van der Waals contributions to surface free energy such that the work of adhesion is minimized. Hydrate adhesion strength was correlated with the practical work of adhesion, i.e. with [gamma]₁(1 + cos [theta]rec) , of a suitable probe fluid, that is, one with similar surface energy properties to those of the hydrate. These fundamental studies provide a framework for the development of hydrate-phobic surfaces, and may lead to passive enhancement of flow assurance and prevention of blockages in deep-sea oil and gas operations.by Jonathan David Smith.S.M