3,140 research outputs found

    The Entrepreneurial State Goes to Europe

    Get PDF
    This article investigates state-level export programs in response to the emerging new economic and political regime of Europe 1992. Little related export promotion activity is found, even in states reputed to have the most active entrepreneurial policies. The authors conclude that states have few resources to invest in export promotion and are inappropriate jurisdictions around which to organize such policy, despite the much touted entrepreneurial state

    Design of a compliant wheel for a miniature rover to be used on Mars

    Get PDF
    The Jet Propulsion Laboratory has identified the need for a compliant wheel for a miniature martian rover vehicle. This wheel must meet requirements of minimum mass, linear radial deflection, and reliability in cryogenic conditions over a five year lifespan. Additionally, axial and tangential deflections must be no more than 10 percent of the radial value. The team designed a wheel by use of finite element and dimensionless parameter analysis. Due to the complex geometry of the wheel, a finite element model describing its behavior was constructed to investigate different wheel configurations. Axial and tangential deflections were greatly reduced but did not meet design criteria. A composite material was selected for its high strength, toughness, fatigue resistance, and damping characteristics. The team chose a Kevlar fiber filled thermoplastic composite. This report is divided into four primary sections. First, the introduction section gives background information, defines the task, and discusses the scope and limitations of the project. Second, the alternative designs section introduces alternative design solutions, addresses advantages and disadvantages of each, and identifies the parameters used to determine the best design. Third, the design solution section introduces the methods used to evaluate the alternates, and gives a description of the design process used. Finally, the conclusion and recommendations section evaluates the wheel design, and offers recommendations pertaining to improvement of the design solution

    Imprints of a Primordial Preferred Direction on the Microwave Background

    Get PDF
    Rotational invariance is a well-established feature of low-energy physics. Violations of this symmetry must be extremely small today, but could have been larger in earlier epochs. In this paper we examine the consequences of a small breaking of rotational invariance during the inflationary era when the primordial density fluctuations were generated. Assuming that a fixed-norm vector picked out a preferred direction during the inflationary era, we explore the imprint it would leave on the cosmic microwave background anisotropy, and provide explicit formulas for the expected amplitudes of the spherical-harmonic coefficients. We suggest that it is natural to expect that the imprint on the primordial power spectrum of a preferred spatial direction is approximately scale-invariant, and examine a simple model in which this is true.Comment: 7 pages, no figures; v5: Corrections, as well as use of more standard convention, in section I

    Physical activity and cardiovascular mortality risk: possible protective mechanisms?

    Get PDF
    INTRODUCTION: The biological mechanisms through which increased physical activity or structured exercise training lowers the risk of recurrent cardiac events are incompletely understood. We examined the extent to which modification of primary risk markers explains the association between physical activity and cardiovascular death in participants with diagnosed cardiovascular disease (CVD). METHODS AND RESULTS: In a prospective study of 1429 participants with physician-diagnosed CVD living in England and Scotland (age = 66.5 ± 11.1 yr (mean ± SD), 54.2% men), we measured physical activity and several risk markers (body mass index, total-to-HDL cholesterol ratio, diagnosed diabetes, systolic blood pressure, resting heart rate, C-reactive protein) at baseline. The main outcome was CVD death. There were a total of 446 all-cause deaths during an average of 7.0 ± 3.1 yr of follow-up, of which 213 were attributed to cardiovascular causes. Participation in moderate to vigorous physical activity at least three sessions per week was associated with lower risk of CVD death (hazard ratio = 0.61, 95% confidence interval = 0.38-0.98). Physically active participants demonstrated significantly lower levels of body mass index, diabetes, and inflammatory risk (C-reactive protein). Metabolic (body mass index, total-to-HDL cholesterol ratio, and physician-diagnosed diabetes) and inflammatory risk factors explained an estimated 12.8% and 15.4%, respectively, of the association between physical activity and CVD death. CONCLUSIONS: Physical activity may reduce the risk of secondary CVD events, in part, by improving metabolic and inflammatory risk markers

    Preparation of charge transfer salt/polymer composites, and characterisation by saturable absorption

    Get PDF
    This thesis describes the preparation of microcrystalline dispersions of a series of organic semiconductors (the alkali metal salts of tetracyanoquinodimethane) within a host polymer. The linear optical properties of these composites are found to be dependent on the method of preparation. Their third order nonlinear optical properties are then investigated by measurement of the intensity dependence of their transmision. Close to the low energy, local excitation band saturable absorption is observed. In the region of the charge transfer band reverse saturable absorption is observed. The results are discussed in terms of a two level model
    corecore