On the generation of internal waves by tidal flow over a sill----a possible nonlinear mechanism

The generation of internal waves in a two layer tidal channel containing a sill is considered. The distorted free surface associated with the locally accelerated tidal flow in the vicinity of the sill is assumed to be the driving force for internal waves. A simplified, nonrigorous model, which incorporates this forcing mechanism, is developed and predicts that internal waves should be generated at twice the tidal frequency as well as at the tidal frequency...

Physical Electronics

Contains research objectives and reports on one research project

Disturbance and succession in early to mid-holocene northern english forests:Palaeoecological evidence for disturbance of woodland ecosystems by mesolithic hunter-gatherers

Forest succession can be monitored in the present, modelled for the future, but also reconstructed in the past on the records of forest history, including through the use of palaeo-ecological techniques. Longer-term records from pollen data can show changes over centennial and millennial timescales that are impacted by climate, migration or soil development. Having knowledge of previous phases of post-disturbance seral stages of woodland regeneration however, as after fire, can provide insights regarding successional process and function over short-term decadal timescales. The aim of this paper is to test the high-resolution pollen record as a source of new insights into processes of succession, assisted by the supplementary data of microscopic charcoal analyses. On short-term timescales, multiple phases of forest disturbance and then recovery have been identified in early to mid-Holocene peat records in northern England, many from the uplands but also from lowland areas. We identify and describe a typology of recovery patterns, including the composition and rate of recovery, and then test the processes and factors that impacted on different seral trajectories, concentrating on fire disturbance which might have had a natural origin, or might have been caused by pre-agricultural Mesolithic hunter-gatherers. Factors considered include the spatial location and intensity of the fire event, the duration of the disturbance phase, the structure and dynamics of the successional regeneration vegetation communities and the pre-disturbance tree cover. Data from examples of fire disturbance of woodland have been examined from both upland and lowland sites in northern England and indicate that they had different successional pathways after disturbance. Fire disturbances in the denser lowland forests were mostly single burn events followed by natural successions and regeneration to forest, whereas fire disturbances in the upland woods usually showed continued or repetitive fire pressure after the initial burning, arresting succession so that vegetation was maintained in a shrub phase, often dominated by Corylus, for an extended period of time until disturbance ceased. This creation of a kind of prolonged, almost plagioclimax, ‘fire-coppice’ hazel stage suggests controlled rather than natural successional pathways, and strongly suggests that Mesolithic foragers were the fire starters in the upland English woodlands where hazel was naturally common and could be maintained in abundance in later-stage successions, along with other edible plants, for human use. All post-fire seral stages would have been attractive to game animals, providing a reliable food source that would have been of great benefit to hunter-gatherer populations

A Density Matrix-based Algorithm for Solving Eigenvalue Problems

A new numerical algorithm for solving the symmetric eigenvalue problem is presented. The technique deviates fundamentally from the traditional Krylov subspace iteration based techniques (Arnoldi and Lanczos algorithms) or other Davidson-Jacobi techniques, and takes its inspiration from the contour integration and density matrix representation in quantum mechanics. It will be shown that this new algorithm - named FEAST - exhibits high efficiency, robustness, accuracy and scalability on parallel architectures. Examples from electronic structure calculations of Carbon nanotubes (CNT) are presented, and numerical performances and capabilities are discussed.Comment: 7 pages, 3 figure

Improving Co-benefits and 'Triple Win' Impacts from Climate Action: The Role of Guidance Tools

This CDI Practice Paper by L.O. Naess, M. Hagemann, B. Harvey, F. Urban, S. Hendel-Blackford and N. Höhne addresses the role of tools in supporting interventions to achieve the ‘triple wins’ of adaptation, mitigation and development. Over recent years there has been a proliferation of guidance tools to support adaptation or mitigation, increasingly in a development context, but little work on the role tools play in helping to bridge the gap between these three areas in practice. Based on a review of tools in view of ‘climate compatible development’, the paper suggests key considerations for how tools could help achieve ‘triple wins’. They include (1) the importance of understanding how tools are a way of defining and shaping a goal, not merely helping to implement actions to achieve it; (2) the value of acknowledging different starting points, and that a lot of the integration is happening – and will continue to happen – on the side of users; and (3) because tools cannot provide all the answers to complex problems they need to be complemented by analysis of actors, goals and outcomes.UK Department for International Developmen

A New Atomic Force Microscopy Technique for the Measurement of the Elastic Properties of Biological Materials

We developed a new technique to measure elastic properties by using the atomic force microscope (AFM) tip to press samples into grooves etched in a GaAs substrate. We measured the Young\u27s modulus of β-chitin fibres with cross-sections less than 40 nm X 20 nm to be 1-2 X 1011 N/m2. In the isotropic approximation, the Young\u27s modulus of the S-layer sheath of the archaeobacterium Methanospirillum hungatei was 1-3 X 1010 N/m2. By testing the sheath to breaking strength we estimated the bacterium can sustain an internal pressure as high as 100-200 atmospheres (1-2 x 107 N/m2)

Rethinking Peer Review: Detecting and Addressing Medical Malpractice Claims Risk

A medical center department chair has just been notified that a physician in his department, Dr. G, is being sued for the fifth time in seven years. The CEO of co-defendant hospital wants the chair to solve Dr. G\u27s claims problems. At the chair\u27s request, the hospital peer review committee evaluates Dr. G\u27s malpractice cases. While committee members note some minor concerns in the cases, they conclude that in each circumstance he has met the standard of care. They cannot identify any specific technical or educational need, nor can they supply justification for a disciplinary action. The chair is in a vexing situation. Is Dr. G. the victim of bad luck, or is something more systematic at work? Is there some failure or deficiency other than technical incompetence which is making this physician vulnerable to malpractice suits? If so, is it remediable? In this Article, we analyze the ability of peer review to recognize and reduce physicians\u27 risk of medical malpractice claims. Critics argue that peer review neither consistently identifies substandard physicians, nor ensures their removal, while it unfairly targets colleagues for reasons such as economic competition. They suggest that the solution may be to modify statutes governing privilege and immunity, or to increase penalties for healthcare institutions that violate reporting statutes. Critics\u27 concerns may be misplaced. We will argue that peer review is not deficient in its basic conception, but rather aspects of its design and implementation which often do not directly link it to an institution\u27s risk management activities. We assert that peer review can effectively identify a physician\u27s risk of generating a disproportionate share of medical malpractice claims ex ante, and present a sample methodology which allows peer review to more effectively help physicians address that risk. Part I of this Article discusses the background and authority for peer review. Part II outlines common criticisms of peer review and discusses shortcomings in these analyses. Part III describes background medical malpractice research and introduces the Patient Advocacy Reporting System ( PARSSM ) program for peer review. In Part IV we conclude with a discussion of programmatic elements which, if incorporated into the legal framework for peer review, may allow peer review committees to systematically evaluate, monitor, and, potentially reduce physicians\u27 medical malpractice claims risk

Impact and detectability of hypothetical CCS offshore seep scenarios as an aid to storage assurance and risk assessment

Carbon Capture and Storage has the potential to make a significant contribution to the mitigation of climate change, however there is a regulatory and societal obligation to demonstrate storage robustness and minimal local environmental impact. This requires an understanding of environmental impact potential and detectability of a range of hypothetical leak scenarios. In the absence of a significant body of real-world release experiments this study collates the results of 86 modelled scenarios of offshore marine releases derived from five different model systems. This synthesis demonstrates a consistent generalised relationship between leak rate, detectability and impact potential of a wide range of hypothetical releases from CO2 storage, which can be described by a power law. For example a leak of the order of 1 T per day should be detectable at, at least, 60 m distance with an environmental impact restricted to less than a 15 m radius of the release point. Small releases are likely to require bottom mounted (lander) monitoring to ensure detection. In summary this work, when coupled with a quantification of leakage risk can deliver a first order environmental impact assessment as an aid to the consenting process. Further this work demonstrates that non-catastrophic release events can be detected at thresholds well below levels which would undermine storage performance or significantly impact the environment, given an appropriate monitoring strategy