Access to telecommunications networks

telecommunication;telecommunication industry;networks;access to market;policy;allocation;microeconomics

Selecting children for head CT following head injury

OBJECTIVE: Indicators for head CT scan defined by the 2007 National Institute for Health and Care Excellence (NICE) guidelines were analysed to identify CT uptake, influential variables and yield. DESIGN: Cross-sectional study. SETTING: Hospital inpatient units: England, Wales, Northern Ireland and the Channel Islands. PATIENTS: Children (3 years were much more likely to have CT than those <3 years (OR 2.35 (95% CI 2.08 to 2.65)). CONCLUSION: Compliance with guidelines and diagnostic yield was variable across age groups, the type of hospital and region where children were admitted. With this pattern of clinical practice the risks of both missing intracranial injury and overuse of CT are considerable

The Rapidly Fading Optical Afterglow of GRB 980519

GRB 980519 had the most rapidly fading of the well-documented GRB afterglows, consistent with t^{-2.05 +/- 0.04} in BVRI as well as in X-rays during the two days in which observations were made. We report VRI observations from the MDM 1.3m and WIYN 3.5m telescopes, and we synthesize an optical spectrum from all of the available photometry. The optical spectrum alone is well fitted by a power law of the form nu^{-1.20 +/- 0.25}, with some of the uncertainty due to the significant Galactic reddening in this direction. The optical and X-ray spectra together are adequately fitted by a single power law nu^{-1.05 +/- 0.10}. This combination of steep temporal decay and flat broad-band spectrum places a severe strain on the simplest afterglow models involving spherical blast waves in a homogeneous medium. Instead, the rapid observed temporal decay is more consistent with models of expansion into a medium of density n(r) proportional to r^{-2}, or with predictions of the evolution of a jet after it slows down and spreads laterally. The jet model would relax the energy requirements on some of the more extreme GRBs, of which GRB 980519 is likely to be an example because of its large gamma-ray fluence and faint host galaxy.Comment: 13 pages, submitted to ApJ Letter

Evolutionary Theorising on Technological Change and Sustainable Development

This paper examines the significance of evolutionary theorising on technological change for (technology) policies aiming to move society into a more ecologically sustainable direction. It is argued that fundamental changes in production processes and consumption patterns underpinned by alternative technological trajectories are required for achieving environmental sustainability. Such changes, which go beyond the control of particular pollutants and eco-efficiency improvements, are referred to as technological regime shifts. Technological regime shift changes do not refer so much to the diffusion of environmental technologies but rather to system changes producing environmental benefits because the new regimes or trajectories are inherently more environmentally benign. An example of such a shift is found in the use of gas turbine for (co)generating electricity and heat. An important question is: how do technological regime shifts occur, and how can environmentally beneficial regime shifts be stimulated? Evolutionary theory, which emphasises the non-linear, branched nature of sociotechnical change, offers a useful framework for understanding and managing regime shifts. It draws attention to the lock-in phenomenon and also suggests a way in which it can be escaped: through the development of niches for new technologies. It appears that evolutionary perspectives have something to offer here, but they need to be further developed to be of practical use

Laser-heated rocket studies

CW laser heated rocket propulsion was investigated in both the flowing core and stationary core configurations. The laser radiation considered was 10.6 micrometers, and the working gas was unseeded hydrogen. The areas investigated included initiation of a hydrogen plasma capable of absorbing laser radiation, the radiation emission properties of hot, ionized hydrogen, the flow of hot hydrogen while absorbing and radiating, the heat losses from the gas and the rocket performance. The stationary core configuration was investigated qualitatively and semi-quantitatively. It was found that the flowing core rockets can have specific impulses between 1,500 and 3,300 sec. They are small devices, whose heating zone is only a millimeter to a few centimeters long, and millimeters to centimeters in radius, for laser power levels varying from 10 to 5,000 kW, and pressure levels of 3 to 10 atm. Heat protection of the walls is a vital necessity, though the fraction of laser power lost to the walls can be as low as 10% for larger powers, making the rockets thermally efficient

The magnetoelectrochemical switch

In the field of spintronics, the archetype solid-state two-terminal device is the spin valve, where the resistance is controlled by the magnetization configuration. We show here how this concept of spin-dependent switch can be extended to magnetic electrodes in solution, by magnetic control of their chemical environment. Appropriate nanoscale design allows a huge enhancement of the magnetic force field experienced by paramagnetic molecular species in solutions, which changes between repulsive and attractive on changing the electrodes' magnetic orientations. Specifically, the field gradient force created within a sub-100-nm-sized nanogap separating two magnetic electrodes can be reversed by changing the orientation of the electrodes' magnetization relative to the current flowing between the electrodes. This can result in a breaking or making of an electric nanocontact, with a change of resistance by a factor of up to 103. The results reveal how an external field can impact chemical equilibrium in the vicinity of nanoscale magnetic circuits

Valuing the Pasture Resource - Importance of Perennials in Higher Rainfall Regions of South Eastern Australia

The premature decline of perennial grass based pastures in southern temperate Australia results in poor productivity and unstable pastures that allow invasion by less desirable weedy species and the potential for soil degradation. The loss of perennial species is attributed to overgrazing arising from an undervaluation of the pasture resource. Resowing pastures is largely uneconomic so maintenance of, or increasing the perennial, is dependent on improved grazing and pasture management practices. A key to changing perceptions is valuing the true worth of the perennial component. Results are presented from a model that takes into account the seasonality of production of pastures of different composition. The model uses specific metabolically energy values for the different functional groups that are typically within pastures (perennial grasses, annual grasses, legumes, broadleaf species) and livestock demand, to estimate animal performance and then gross margins for different pasture types. The results show that the value of perennial grasses is much greater than any other component and the more perennial grass, the greater the returns. The potential use of this approach to provide more useful information to landholders, permitting more appropriate management decisions to be made, is described