Measuring the impact of educational interventions on the academic performance of academic development students in second-year microeconomics

This is the accepted version of the following article: Smith, L. & Ranchhod, V. 2012. Measuring the impact of educational interventions on the academic performance of academic development students in second-year microeconomics. South African Journal of Economics. 80(3): 431-448., which has been published in final form at: http://dx.doi.org/10.1111/j.1813-6982.2011.01287.x.This paper analyses the impact of educational interventions made in the first- and second-year microeconomics courses on academic development students' final mark in the second-year course. It also addresses issues of methodology, specification, and statistical analysis with respect to other studies in the field. The results suggest that the educational interventions in the first year had a positive impact on the academic performance of the academic development cohort, relative to the mainstream cohort for the first period (2000-2002). The results also suggest that the educational interventions introduced in the second period (2003-2005), in the form of voluntary workshops, improved the academic performance of the academic development and mainstream cohorts

Measuring the success of an academic development programme: a statistical analysis

This article uses statistical analysis to estimate the impact of first-year academic development courses in microeconomics, statistics, accountancy, and information systems, offered by the University of Cape Town's Commerce Academic Development Programme, on students' graduation performance relative to that achieved by mainstream students. The data for four cohorts, covering the years 1999–2002 is pooled. The results suggest that membership of the academic development programme enables students to out-perform their peers on the mainstream controlling for a number of independent variables, and that the positive effect of the first-year courses on graduation performance is particularly pronounced for African students. The implications of these findings for higher education in South Africa are considered

An analysis of the impact of pedagogic interventions in first-year academic development and mainstream courses in microeconomics

This is the accepted version of the following article: Smith, L. C. 2009. An analysis of the impact of pedagogic interventions in first-year academic development and mainstream courses in microeconomics. South African Journal of Economics. 77(1): 162-178., which has been published in final form at: http://dx.doi.org/10.1111/j.1813-6982.2009.01195.x.This paper analyses the impact of pedagogic interventions in first-year academic development and mainstream courses in microeconomics on students' performance in the final examination. The data for six cohorts, covering the years 1999 and 2001-2005, are pooled, and the Heckman two-part procedure is used to account for those students who started the course but did not write the final examination. The results suggest that the pedagogic interventions have a positive impact on the performance of academic development students relative to the mainstream cohort and on the performance of mainstream students

Multiwavelength Observations of GX 339-4 in 1996; 3, Keck Spectroscopy

As part of our multiwavelength campaign of observations of GX 339-4 in 1996 we present our Keck spectroscopy performed on May 12 UT. At this time, neither the ASM on the RXTE nor BATSE on the CGRO detected the source. The optical emission was still dominated by the accretion disk with V approximately 17 mag. The dominant emission line is H alpha, and for the first time we are able to resolve a double peaked profile. The peak separation Delta v = 370 +/- 40 km/s. Double peaked H alpha emission lines have been seen in the quiescent optical counterparts of many black hole X-ray novae. However, we find that the peak separation is significantly smaller in GX 339-4, implying that the optical emission comes from a larger radius than in the novae. The H alpha emission line may be more akin to the one in Cygnus X-1, where it is very difficult to determine if the line is intrinsically double peaked because absorption and emission lines from the companion star dominate

Interstellar Polarization and the Position Angle Orientations of Seyfert 1 Galaxies

We comment on recent spectropolarimetric studies that compare the observed polarization position angles (PAs) of Seyfert 1 galaxies near H alpha with the observed orientations of their radio source axes on the sky. For a Seyfert galaxy in which scattering occurs mainly in an equatorial scattering region, one expects the polarization PA to be parallel to the radio axis, while in a case in which light scatters predominantly in the polar regions, the H alpha polarization PA should be perpendicular to the radio axis. In practice, these correlations are difficult to establish because a Galactic interstellar polarization contribution can introduce a significant uncertainty into the polarization PA determination, even when the magnitude of interstellar polarization is small. We show how such uncertainties may affect the analysis of PA alignments and present spectropolarimetric observations of a probe star along the line of sight to the Seyfert 1 galaxy Mrk 871 that allow us to assess the intrinsic H alpha polarization and PA of Mrk 871. These results suggest that spectropolarimetric observations of such probe stars should form an integral part of future Seyfert galaxy polarization studies.Comment: 15 pages, 3 figures, accepted by MNRAS; made small corrections to the derived ISP of Mrk 871 and other minor revisions in response to the referee's recommendation

The Application of Ultrasonics in Non-Destructive Testing: A Review of Some of the Research at University College London

This paper presents a review of some of the research projects at University College London which use ultrasonic waves in non-destructive testing. The projects covered include a low-frequency scanning acoustic microscope, a new dark-field acoustic microscope, an update on finite difference model studies of wave propagation and scattering, developments in mode-conversion techniques for defect characterisation, a new high-resolution acoustic field sampling probe and a resume of the work on Zn0 transducers

A Massive Progenitor of the Luminous Type IIn Supernova 2010jl

The bright, nearby, recently discovered supernova SN2010jl is a member of the rare class of relatively luminous Type~IIn events. Here we report archival HST observations of its host galaxy UGC5189A taken roughly 10yr prior to explosion, as well as early-time optical spectra of the SN. The HST images reveal a bright, blue point source at the position of the SN, with an absolute magnitude of -12.0 in the F300W filter. If it is not just a chance alignment, the source at the SN position could be (1) a massive young (less than 6 Myr) star cluster in which the SN resided, (2) a quiescent, luminous blue star with an apparent temperature around 14,000K, (3) a star caught during a bright outburst akin to those of LBVs, or (4) a combination of option 1 and options 2 or 3. Although we cannot confidently choose between these possibilities with the present data, any of them imply that the progenitor of SN2010jl had an initial mass above 30Msun. This reinforces mounting evidence that many SNe IIn result from very massive stars, that massive stars can produce visible SNe without collapsing quietly to black holes, and that massive stars can retain their H envelopes until shortly before explosion. Standard stellar evolution models fail to account for these observed properties.Comment: 6 pages, 4 figures, submitted to Ap

Noninfectious retrovirus particles drive the APOBEC3/Rfv3 dependent neutralizing antibody response.

Members of the APOBEC3 family of deoxycytidine deaminases counteract a broad range of retroviruses in vitro through an indirect mechanism that requires virion incorporation and inhibition of reverse transcription and/or hypermutation of minus strand transcripts in the next target cell. The selective advantage to the host of this indirect restriction mechanism remains unclear, but valuable insights may be gained by studying APOBEC3 function in vivo. Apobec3 was previously shown to encode Rfv3, a classical resistance gene that controls the recovery of mice from pathogenic Friend retrovirus (FV) infection by promoting a more potent neutralizing antibody (NAb) response. The underlying mechanism does not involve a direct effect of Apobec3 on B cell function. Here we show that while Apobec3 decreased titers of infectious virus during acute FV infection, plasma viral RNA loads were maintained, indicating substantial release of noninfectious particles in vivo. The lack of plasma virion infectivity was associated with a significant post-entry block during early reverse transcription rather than G-to-A hypermutation. The Apobec3-dependent NAb response correlated with IgG binding titers against native, but not detergent-lysed virions. These findings indicate that innate Apobec3 restriction promotes NAb responses by maintaining high concentrations of virions with native B cell epitopes, but in the context of low virion infectivity. Finally, Apobec3 restriction was found to be saturable in vivo, since increasing FV inoculum doses resulted in decreased Apobec3 inhibition. By analogy, maximizing the release of noninfectious particles by modulating APOBEC3 expression may improve humoral immunity against pathogenic human retroviral infections