Modelling the brightness increase signature due to asteroid collisions

We have developed a model to predict the post-collision brightness increase of sub-catastrophic collisions between asteroids and to evaluate the likelihood of a survey detecting these events. It is based on the cratering scaling laws of Holsapple and Housen (2007) and models the ejecta expansion following an impact as occurring in discrete shells each with their own velocity. We estimate the magnitude change between a series of target/impactor pairs, assuming it is given by the increase in reflecting surface area within a photometric aperture due to the resulting ejecta. As expected the photometric signal increases with impactor size, but we find also that the photometric signature decreases rapidly as the target asteroid diameter increases, due to gravitational fallback. We have used the model results to make an estimate of the impactor diameter for the (596) Scheila collision of D=49-65m depending on the impactor taxonomy, which is broadly consistent with previous estimates. We varied both the strength regime (highly porous and sand/cohesive soil) and the taxonomic type (S-, C- and D-type) to examine the effect on the magnitude change, finding that it is significant at early stages but has only a small effect on the overall lifetime of the photometric signal. Combining the results of this model with the collision frequency estimates of Bottke et al. (2005), we find that low-cadence surveys of approximately one visit per lunation will be insensitive to impacts on asteroids with D<20km if relying on photometric detections

Enhancing the learning environment using classroom response systems

Classroom response systems (CRS) offer a management tool for engaging students in the classroom. These systems have been used in a variety of fields and at all levels of education. Typical goals of CRS questions are discussed, as well as the advantages to both students and instructors as a result of using them. These systems are especially valuable as a means of introducing and monitoring peer learning methods in the large lecture classroom. But the efficacy of using these systems depends strongly on the quality of the questions used. The integration of a CRS in an introductory physics module is discussed along with examples of questions used and the student assessment carried out

Interruption overload: telephones in Ford Madox Ford’s "4692 Padd", "A Call" and "A Man Could Stand Up"

Ford Madox Ford’s short story “‘4692 Padd’” (1908), his novella A Call (1910), and his novel A Man Could Stand Up— (1926) all exploit the narratological potential of the rhetorical tropes of interruption. In each text, the interruption is caused by a cutting-edge contemporary gadget: the telephone. In “‘4692 Padd’” and A Call, the phone-calls have a parenthetical nature. But by the time of A Man Could Stand Up—, Ford is experimenting with extreme interruption by telephone, or what is known in ergonomics as “interruption overload.” The narratological effect of interruption overload is both to record and recreate a specific historical moment of geo-political uncertainty: the end of the First World War

The Evolution of International Consumption Risk Sharing Over Time And Frequency

Improved consumption risk sharing is one of the fundamental predicted benefits of increased financial integration, yet the empirical evidence concerning this proposition is mixed. Using the novel empirical technique of wavelet analysis, this paper for the first time in the literature uncovers the heterogeneous evolution of consumption and output correlations over the time and frequency dimensions simultaneously. Periods of strong comovement in consumption growth rates not only occur during times of common (uninsurable) shocks to output, but also to some extent during times of increased financial integration. This evidence adds a new dimension to the consumption output correlation puzzle, which appears to only hold at certain time periods and frequencies.consumption - Output Correlation Puzzle, International Consumption Risk Sharing, Wavelet Analysis

The politics of what works in service delivery:\ud An evidence-based review

This paper examines the evidence on the forms of politics likely to promote inclusive social provisioning and enable, as opposed to constrain, improvements in service outcomes. It focuses on eight relatively successful cases of delivery in a range of country contexts and sectors (roads, agriculture, health, education) where independent evaluations demonstrate improved outcomes. The paper traces the main characteristics of the political environment for these cases, from the national political context, to the politics of sector policymaking, to the micro politics of implementation. The findings indicate that it is possible to identify connections between good performance and better outcomes at the point of delivery and the main forms of politics operating at local, sector and national levels.\ud \ud A number of common factors underpinning successful delivery emerge strongly but need to be tested through further research. In particular, the paper highlights the relationship between inclusive delivery and periods of crisis and transition;the nature of the political settlement;the types of calculations of political returns being made by political actors at all levels, and; the extent to which the state derives or seeks to enhance its legitimacy through the provision of a particular service