329 research outputs found

    Electrodynamics with radiation reaction

    Full text link
    The self force of electrodynamics is derived from a scalar field. The resulting equation of motion is free of all of the problems that plague the Lorentz Abraham Dirac equation. The age-old problem of a particle in a constant field is solved and the solution has intuitive appeal.Comment: 5 page

    An energy vision for a planet under pressure

    Get PDF
    Worldwide, global energy systems face an array of challenges, from access for the poor to reliability and security. Meanwhile, the provision of energy creates local human and ecological health impacts as well as dangerous global climate change. Addressing these issues simultaneously will require a fundamental transformation of the energy system. Recent assessments show that such a transformation is achievable in technological and economic terms, but it will present formidable supply- and demand-side challenges as well as problems of governance, transparency and reliability across scales. This policy brief presents a long-term vision for the energy system and describes the elements required for the transition towards this vision. To succeed, this transformation must integrate several key components, including a focus on high levels of energy efficiency and the scale up of investments in technology deployment as well as research, development and demonstration (RD&D)

    Carolina Forum: Western North Carolina: Destruction or Protection?; Computers and Cultural Resources: A Planning Perspective; A Balanced Approach to Industrial Development

    Get PDF
    This edition of Carolina Forum includes the following: WESTERN NORTH CAROLINA: DESTRUCTION OR PROTECTION? As coordinator of the Western North Carolina Mountain League and founder of the Save Joyce Kilmer League, I would like to take this opportunity to present a most interesting and pressing problem in regional planning. COMPUTERS AND CULTURAL RESOURCES: A PLANNING PERSPECTIVE: Under the auspices of the National Environmental Policy Act (NEPA) of 1969 and the National Historic Preservation Act (NHPA) of 1966, applicants for federal funds for planning or development must evaluate the effects of their activities on significant cultural resources*. When cultural resource data are not readily available to project planners, or are not incorporated into the planning process in its early stages, problems and project delays often result. A BALANCED APPROACH TO INDUSTRIAL DEVELOPMENT: Trying to plan for economic growth in a free economy is like trying to herd a covey of flushed quail. At best, you move it in a general direction. Happily, North Carolina does have strong economic growth these days, and what once was nicknamed "Tobacco Road" is now hailed the bustling "Sunbelt." The state has enjoyed a steady increase in new capital investments for the past three years, and 1978 continues the trend. Governor Jim Hunt has emphasized economic development in his administration, and he has engaged the state in an ambitious effort to develop a "balanced growth" policy

    Constraining spacetime torsion with LAGEOS

    Full text link
    We compute the corrections to the orbital Lense-Thirring effect (or frame-dragging) in the presence of spacetime torsion. We derive the equations of motion of a test body in the gravitational field of a rotating axisymmetric massive body, using the parametrized framework of Mao, Tegmark, Guth and Cabi. We calculate the secular variations of the longitudes of the node and of the pericenter. We also show how the LAser GEOdynamics Satellites (LAGEOS) can be used to constrain torsion parameters. We report the experimental constraints obtained using both the nodes and perigee measurements of the orbital Lense-Thirring effect. This makes LAGEOS and Gravity Probe B (GPB) complementary frame-dragging and torsion experiments, since they constrain three different combinations of torsion parameters

    Comparative study of density functional theories of the exchange-correlation hole and energy in silicon

    Full text link
    We present a detailed study of the exchange-correlation hole and exchange-correlation energy per particle in the Si crystal as calculated by the Variational Monte Carlo method and predicted by various density functional models. Nonlocal density averaging methods prove to be successful in correcting severe errors in the local density approximation (LDA) at low densities where the density changes dramatically over the correlation length of the LDA hole, but fail to provide systematic improvements at higher densities where the effects of density inhomogeneity are more subtle. Exchange and correlation considered separately show a sensitivity to the nonlocal semiconductor crystal environment, particularly within the Si bond, which is not predicted by the nonlocal approaches based on density averaging. The exchange hole is well described by a bonding orbital picture, while the correlation hole has a significant component due to the polarization of the nearby bonds, which partially screens out the anisotropy in the exchange hole.Comment: 16 pages, 5 figures, RevTeX, added conten

    A First Search for coincident Gravitational Waves and High Energy Neutrinos using LIGO, Virgo and ANTARES data from 2007

    Get PDF
    We present the results of the first search for gravitational wave bursts associated with high energy neutrinos. Together, these messengers could reveal new, hidden sources that are not observed by conventional photon astronomy, particularly at high energy. Our search uses neutrinos detected by the underwater neutrino telescope ANTARES in its 5 line configuration during the period January - September 2007, which coincided with the fifth and first science runs of LIGO and Virgo, respectively. The LIGO-Virgo data were analysed for candidate gravitational-wave signals coincident in time and direction with the neutrino events. No significant coincident events were observed. We place limits on the density of joint high energy neutrino - gravitational wave emission events in the local universe, and compare them with densities of merger and core-collapse events.Comment: 19 pages, 8 figures, science summary page at http://www.ligo.org/science/Publication-S5LV_ANTARES/index.php. Public access area to figures, tables at https://dcc.ligo.org/cgi-bin/DocDB/ShowDocument?docid=p120000

    Phylogenomic analysis of a 55.1 kb 19-gene dataset resolves a monophyletic Fusarium that includes the Fusarium solani Species Complex

    Get PDF
    Scientific communication is facilitated by a data-driven, scientifically sound taxonomy that considers the end-user¿s needs and established successful practice. In 2013, the Fusarium community voiced near unanimous support for a concept of Fusarium that represented a clade comprising all agriculturally and clinically important Fusarium species, including the F. solani species complex (FSSC). Subsequently, this concept was challenged in 2015 by one research group who proposed dividing the genus Fusarium into seven genera, including the FSSC described as members of the genus Neocosmospora, with subsequent justification in 2018 based on claims that the 2013 concept of Fusarium is polyphyletic. Here, we test this claim and provide a phylogeny based on exonic nucleotide sequences of 19 orthologous protein-coding genes that strongly support the monophyly of Fusarium including the FSSC. We reassert the practical and scientific argument in support of a genus Fusarium that includes the FSSC and several other basal lineages, consistent with the longstanding use of this name among plant pathologists, medical mycologists, quarantine officials, regulatory agencies, students, and researchers with a stake in its taxonomy. In recognition of this monophyly, 40 species described as genus Neocosmospora were recombined in genus Fusarium, and nine others were renamed Fusarium. Here the global Fusarium community voices strong support for the inclusion of the FSSC in Fusarium, as it remains the best scientific, nomenclatural, and practical taxonomic option availabl

    Gendering the careers of young professionals: some early findings from a longitudinal study. in Organizing/theorizing: developments in organization theory and practice

    Full text link
    Wonders whether companies actually have employees best interests at heart across physical, mental and spiritual spheres. Posits that most organizations ignore their workforce – not even, in many cases, describing workers as assets! Describes many studies to back up this claim in theis work based on the 2002 Employment Research Unit Annual Conference, in Cardiff, Wales
    corecore