Green's functions for far-side seismic images: a polar expansion approach

We have computed seismic images of magnetic activity on the far surface of the Sun by using a seismic-holography technique. As in previous works, the method is based on the comparison of waves going in and out of a particular point in the Sun but we have computed here the Green's functions from a spherical polar expansion of the adiabatic wave equations in the Cowling approximation instead of using the ray-path approximation previously used in the far-side holography. A comparison between the results obtained using the ray theory and the spherical polar expansion is shown. We use the gravito-acoustic wave equation in the local plane-parallel limit in both cases and for the latter we take the asymptotic approximation for the radial dependencies of the Green's function. As a result, improved images of the far-side can be obtained from the polar-expansion approximation, especially when combining the Green's functions corresponding to two and three skips. We also show that the phase corrections in the Green's functions due to the incorrect modeling of the uppermost layers of the Sun can be estimated from the eigenfrequencies of the normal modes of oscillation.Comment: 8 pages, 5 figures, Astrophysical Journal, accepted (2010

Development Communication: 1. History and Theories

This entry includes three articles, each dealing with a different aspect of the subject: History and Theories Alternative Systems Projects The first and third cover predominantly the Western (especially the U.S.) approach; the second raises some criticisms directed at both the theoretical and the practical limitations of the Western perspective and presents alternative views

Computers, the internet, and cheating among secondary school students: Some implications for educators

This article investigates in greater depth one particular aspect of cheating within secondary education and some implications for measuring academic achievement. More specifically, it examines how secondary students exploit the Internet for plagiarizing schoolwork, and looks at how a traditional method of educational assessment, namely paper-based report and essay writing, has been impacted by the growth of Internet usage and the proliferation of computer skills among secondary school students. One of the conclusions is that students’ technology fluency is forcing educators to revisit conventional assessment methods. Different options for combating Internet plagiarism are presented, and some software tools as well as non-technology solutions are evaluated in light of the problems brought about by “cyberplagiarism.

Littlest Inverse Seesaw Model

We propose a minimal predictive inverse seesaw model based on two right-handed neutrinos and two additional singlets, leading to the same low energy neutrino mass matrix as in the Littlest Seesaw (LS) (type I) model. In order to implement such a Littlest Inverse Seesaw (LIS) model, we have used an $S_{4}$ family symmetry, together with other various symmetries, flavons and driving fields. The resulting LIS model leads to an excellent fit to the low energy neutrino parameters, including the prediction of a normal neutrino mass ordering, exactly as in the usual LS model. However, unlike the LS model, the LIS model allows charged lepton flavour violating (CLFV) processes and lepton conversion in nuclei within reach of the forthcoming experiments.Comment: 17 pages, 9 figures. Published versio

Microeconomic Effects of Capital Controls: The Chilean Experience During the 1990s.

This paper studies the experience with the use of capital controls in Chile during the 1990s. Rather than revisiting previous studies, it complements previous research by providing, for the first time, empirical evidence on some of the microeconomic effects of capital controls, in particular, the unremunerated reserve requirement (URR). By looking at financial statements for a group of 73 Chilean firms during 1986-2001, the paper attempts to identify the effects of the URR on the firms’ costs and ways of financing. Chilean firms are grouped by economic sector, size and access to international capital markets. Results show that the effects of the URR are firm specific; forinstance, there are striking differences in the response to the URR among firms of different size and those with or without access to international capital markets.