GravityCam: higher resolution visible wide-field imaging

The limits to the angular resolution has, during the latest 70 years, been obtainable from the ground only through extremely expensive adaptive optics facilities at large telescopes, and covering extremely small spatial areas per exposure. Atmospheric turbulence therefore limits image quality to typically 1 arcsec in practice. We have developed a new concept of ground-based imaging instrument called GravityCam capable of delivering significantly sharper images from the ground than is normally possible without adaptive optics. The acquisition of visible images at high speed without significant noise penalty has been made possible by advances in optical and near IR imaging technologies. Images recorded at high speed can be aligned before combination and can yield a 3-5 fold improvement in image resolution, or be used separately for high-cadence photometry. Very wide survey fields are possible with widefield telescope optics. GravityCam is proposed to be installed at the 3.6m New Technology Telescope (NTT) at the ESO La Silla Observatory in Chile, where it will greatly accelerate the rate of detection of Earth sized planets by gravitational microlensing. GravityCam will also improve substantially the quality of weak shear studies of dark matter distribution in distant clusters of galaxies and provide a vast dataset for asteroseismology studies. In addition, GravityCam promises to generate a unique data set that will help us understand of the population of the Kuiper belt and possibly the Oort cloud

The vocational-guidance movement in the United States

Thesis (M.A.)--Boston Universit

Electron beam standby absorber system

Electron beam energy is absorbed by deflectors which allow beam distribution over an absorber located between the deflectors and workpiece. The undeflected beam passes through a hole in the absorber when the deflection is de-energized, when energized, the beam is kept to a minimum power level by deflection rate change

A class of exactly solvable models for the Schrodinger equation

We present a class of confining potentials which allow one to reduce the one-dimensional Schroodinger equation to a named equation of mathematical physics, namely either Bessel's or Whittaker's differential equation. In all cases, we provide closed form expressions for both the symmetric and antisymmetric wavefunction solutions, each along with an associated transcendental equation for allowed eigenvalues. The class of potentials considered contains an example of both cusp-like single wells and a double-well.Comment: 5 pages, 7 figure

The marginal costs of climate changing emissions

This paper presents the marginal costs of the emissions of a selected number of radiatively-active gases, three uniformly-mixed gases – carbon dioxide, methane, nitrous oxide – and two region-specific gases – nitrogen (from aircraft) and sulphur, which influence ozone and sulphate aerosol concentrations, respectively. The paper complements earlier research by adding a third model (FUND2.0), adding region-specific gases, and by presenting an alternative accounting framework. The discounting and valuation procedures for marginal cost estimation were refined, but the estimates for the three greenhouse gases do not substantially differ from those in earlier research. It should be noted that with the inclusion of new insights into the impacts of climate change, it can no longer be excluded that marginal costs are negative, particularly for methane. The sign of the costs is model and region dependent. Despite their short life-time, the marginal costs of nitrogen and sulphur emissions are relatively large, primarily because they are not much discounted. The results presented should not be taken as final estimates. The impacts covered by the models used are only a fraction (of unknown size) of all climate change impacts. Particularly, large scale disruptions, such as a breakdown of North Atlantic Deep Water formation or a collapse of the West-Antarctic Ice Sheet, are excluded from the analysis

Creating interaction in online learning: a case study

This paper uses the case‐study method to examine detailed data related to student and tutor usage of an asynchronous discussion board as an interactive communication forum during a first‐semester associate degree course in applied psychology at the City University of Hong Kong. The paper identifies ‘what works’ in relation to discussion board use, demonstrating how students might gradually create an online community of their own, but only if prompted in a timely and appropriate way by the course structure. It also identifies three distinct phases in online interaction and suggests these might, to some extent, be mediated by assessment tasks