5,913 research outputs found

    Bosonization in Higher Dimensions

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    Using the recently discovered connection between bosonization and duality transformations (hep-th/9401105 and hep-th/9403173), we give an explicit path-integral representation for the bosonization of a massive fermion coupled to a U(1) gauge potential (such as electromagnetism) in d space (D=d+1 spacetime) dimensions. The bosonic theory is described by a rank d-1 antisymmetric Kalb-Ramond-type gauge potential. We construct the bosonized lagrangian explicitly in the limit of large fermion mass. We find that the resulting action is local for d=2 (and given by a Chern-Simons action), but nonlocal for d larger than 3. By coupling to a statistical Chern-Simons field for d=2, we obtain a bosonized formulation of anyons. The bosonic theory may be further dualized to a theory involving purely scalars, for any d, and we show this to be governed by a higher-derivative lagrangian for which the scalar decouples from the U(1) gauge potential.Comment: (We had omitted some references and had misspelled `aficionados') plain TeX, 11 pages, McGill-94/33, NEIP-94-006, OSLO-TP 10-9

    Developing a multi-pollutant conceptual framework for the selection and targeting of interventions in water industry catchment management schemes

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    In recent years water companies have started to adopt catchment management to reduce diffuse pollution in drinking water supply areas. The heterogeneity of catchments and the range of pollutants that must be removed to meet the EU Drinking Water Directive (98/83/EC) limits make it difficult to prioritise areas of a catchment for intervention. Thus conceptual frameworks are required that can disaggregate the components of pollutant risk and help water companies make decisions about where to target interventions in their catchments to maximum effect. This paper demonstrates the concept of generalising pollutants in the same framework by reviewing key pollutant processes within a source-mobilisation-delivery context. From this, criteria are developed (with input from water industry professionals involved in catchment management) which highlights the need for a new water industry specific conceptual framework. The new CaRPoW (Catchment Risk to Potable Water) framework uses the Source-Mobilisation-Delivery concept as modular components of risk that work at two scales, source and mobilisation at the field scale and delivery at the catchment scale. Disaggregating pollutant processes permits the main components of risk to be ascertained so that appropriate interventions can be selected. The generic structure also allows for the outputs from different pollutants to be compared so that potential multiple benefits can be identified. CaRPow provides a transferable framework that can be used by water companies to cost-effectively target interventions under current conditions or under scenarios of land use or climate change

    Can head louse repellents really work? Field studies of piperonal 2% spray

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    Background. Many families find regular checking of children’s heads for head louse infestation too onerous and would prefer to be able to prevent infestation by use of a topical application that deters lice from infesting the head. Identification in the laboratory of a repellent activity for piperonal provided the basis for developing a spray product to repel lice.Methods. A proof of principle field study in Dhaka, Bangladesh, compared the effect of using 2% piperonal spray with that of a placebo in 105 children and adults from three communities with infestation levels close to 100%. All participants were treated for infestation and subsequent incidence of reinfestation monitored daily by investigators. A second randomised, controlled, double blind, study in North London, UK, evaluated the effect of the product in normal use. One hundred and sixty-three children from schools with a high level (20–25%) of infestation were treated and confirmed louse free and randomly divided between 2% piperonal, a placebo spray, and a control group for up to 22 weeks. Parents applied the spray and monitored for infestation. Regular investigator visits confirmed the parental monitoring and replenished supplies of spray.Results. In Dhaka, over 18 days there were only 4 infestations in the piperonal group and 8 in the placebo group. This difference was not significant (p = 0.312). In North London, there were 41 cases of infestation over the course of the study. Although there were fewer infestations in the piperonal group, analysis of time to first infestation showed a no significant (p = 0.4368) difference between groups.Conclusion. Routine use of 2% piperonal spray in communities with a high prevalence of head louse infestation may provide some protection from infestation. However, the difference between use of the product and no active intervention was sufficiently small that regular checking for presence of lice is likely to be a more practical and cost effective approach to prevention of infestation

    Heritable and Experiential Effects on Boldness in a Tropical Poeciliid

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    Consistent differences in human behaviour are often explained with reference to personality traits. Recent evidence suggests that similar traits are widespread across the entire animal kingdom and that they may have substantial fitness consequences. One of the major components of personality is the shyness–boldness continuum. Little is known about the relative contributions of genes and the environment in the development of boldness in wild animal populations. Here, we bred wild-caught fish (Brachyraphis episcopi) collected from regions of highand low-predation pressure, reared their offspring in the laboratory under varying conditions and tested boldness utilising an open-field paradigm. First-generation laboratory-reared fish showed similar behaviour to their wild parents suggesting that boldness has a heritable component. In addition, repeated chasing with a net increased boldness in both high- and low-predation offspring, showing that boldness is also heavily influenced by life experiences. Differences between males and females were also sustained in the laboratory-reared generation indicating that sex differences in boldness are also heritable. We discuss these results with reference to the potential underlying genetic and hormonal mechanisms as well as the environmental influences that may be responsible for expression of boldness in wild animals

    Effective Organizational Practices for Middle and High School Grades

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    At the request of the Accountability Review Council, Research for Action identified effective organizational practices used by better performing schools serving substantial numbers of low income middle and high school students in the School District of Philadelphia. These practices are organized into three spheres: Conditions for Teaching, Student-Centered School Community, and Instructional Program. For each sphere, the report offers broad strategies and specific practices to enact the strategies. Nuanced school case studies show how the practices can work synergistically and coherently in schools to help students succeed

    Beach Erosion and Nourishment in Gold Coast: Perceptions, Policies and Prospects

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    The combination of ongoing urban development and forecasted impacts of the changing climate are projected to place many coastal areas at risk. One of the associated risks is beach erosion, and consequently, nourishment initiatives have become a costly sustainable development issue for local and state governments. For instance, the popular Palm Beach, a nearly four kilometres stretch of sandy beach on the southern Gold Coast in Queensland, Australia has been identified as being more susceptible to serious erosion than other beaches in the city. Consequently, the local council has spent millions of dollars on beach nourishment and is seeking ways to fund the initiative. In this context of coastal management, an exploratory pilot research project was undertaken to examine the question of - “how do local residents and tourists perceive the problem of beach erosion and to what extent are they willing to support beach nourishment initiatives”? Results of quantitative analyses of 68 face to face survey responses of beach goers (local residents and tourists) are outlined in terms of Willingness to Donate (WTD) framework. Findings indicate: a) more than three-quarters of respondents perceived beach nourishment as an important issue, b) local residents were more willing to volunteer towards beach nourishment, and c) tourists were more willing to donate money to work towards resolving the problem. The financial and policy implications of these findings in the context of beach nourishment are discussed

    Asset Management and Governance – An Analysis of Fleet Management Process Issues in an Asset-Intensive Organization

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    Efficient asset management is a key performance driver for asset-intensive organizations. Achieving high utilization and return on investment on physical assets are central corporate objectives for public and private organisations alike. Current approaches on asset management include the engineering and governance perspectives. The engineering perspective on asset management concentrates on the technical and operational dimensions of asset performance, including utilization, and operation to technical specifications. However, this perspective often ignores organisational-level factors that potentially affect asset performance. By contrast, from a governance perspective, key factors influencing asset management performance include stewardship, accountability and incentive regimes. Symmetrically, the governance view often takes the operational factors for granted. In sum, both perspectives offer valuable but incomplete insights on the management of asset performance: experience demonstrates that an exclusive focus on one or the other may lead to sub-optimal asset and organizational performance. In this paper, we investigate how an integrated approach to asset management can be constructed in the context of vehicle fleets. Vehicle fleets provide a suitable context to investigate these issues as they constitute significant investments, and are observable across a range of asset-intensive industries. Beginning with an analysis of how the asset management process is operated through the asset lifecycle, we identify key engineering and organizational factors influencing asset performance. The relationships between factors are analyzed to provide an integrated fleet asset management approach

    Taste fiber responses during reinnervation of fungiform papillae

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    Crushing or transecting the chorda tympani nerve of the gerbil ( Meriones unguiculatus ) caused ipsilateral degeneration of taste buds in the fungiform papillae. In less than two weeks some taste fibers regenerated into the tongue and formed new taste buds and receptor cells. The recovery process was evaluated electrophysiologically in 53 gerbils by acute recording proximal to the nerve injury site. Initially the chorda tympani was electrically silent. In gerbils tested at later times spontaneous activity appeared. This was followed by responses to pressure on the tongue. Taste responses returned as early as dasy 11. The receptive field of regenerated taste fibers was limited to a small number of fungiform papillae. Taste responses were always associasted with the presence of one or more taste buds in the receptive field. Taste buds identified as responsive to chemicals contained some fusiform cells. We found thast the taste responses of single fiber, few-fiber and multi-unit preparations reflected the diversity of responses found in normal taste axons as determined by recording from 26 normal single fibers and 27 normal whole nerves. The early emergence of a variety of fiber types and responses to many chemicals in regeneration is inconsistent with the proposition that the relative chemical responsiveness of a receptor cell is strictly a function of its age; the response of a given young taste receptor is not necessarily limited to a few of the standard taste stimulants.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/49998/1/901720406_ftp.pd

    Flexibility within the Heads of Muscle Myosin-2 Molecules

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    We show that negative-stain electron microscopy and image processing of nucleotide-free (apo) striated muscle myosin-2 subfragment-1 (S1), possessing one light chain or both light chains, is capable of resolving significant amounts of structural detail. The overall appearance of the motor and the lever is similar in rabbit, scallop and chicken S1. Projection matching of class averages of the different S1 types to projection views of two different crystal structures of apo S1 shows that all types most commonly closely resemble the appearance of the scallop S1 structure rather than the methylated chicken S1 structure. Methylation of chicken S1 has no effect on the structure of the molecule at this resolution: it too resembles the scallop S1 crystal structure. The lever is found to vary in its angle of attachment to the motor domain, with a hinge point located in the so-called pliant region between the converter and the essential light chain. The chicken S1 crystal structure lies near one end of the range of flexion observed. The Gaussian spread of angles of flexion suggests that flexibility is driven thermally, from which a torsional spring constant of ~ 23 pN·nm/rad2 is estimated on average for all S1 types, similar to myosin-5. This translates to apparent cantilever-type stiffness at the tip of the lever of 0.37 pN/nm. Because this stiffness is lower than recent estimates from myosin-2 heads attached to actin, we suggest that binding to actin leads to an allosteric stiffening of the motor–lever junction
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