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

State Capacity and Non-state Service Provision in Fragile and Conflict-affected States

How can governments effectively engage with non-state providers (NSPs) of basic services where capacity is weak? This paper examines whether and how fragile and conflict affected states can co-ordinate, finance, and set and apply standards for the provision of basic services by NSPs. It explores ways of incrementally engaging the state, beginning with activities that are least likely to do harm to non-state provision. Through the ‘indirect’ roles of setting the policy environment and engaging in policy dialogue, regulating and facilitating, contracting, and entering into mutual and informal agreements with NSPs, the state can in principle assume responsibility for the provision of basic services without necessarily being involved in direct provision. But government capacity to perform these roles is constrained by the state’s weak legitimacy, coverage and competence, lack of basic information about the non-state sector, and lack of basic organisational capacity to form and maintain relationships with NSPs. The experience of the exercise of the indirect roles in fragile settings suggests: * Governments may be more willing to engage with NSPs where there is recognition that government cannot alone deliver all services, where public and private services are not in competition, and where there is evidence that successful collaboration is possible (demonstrated through small-scale pilots). * The extent to which engagements are ‘pro-service’may be influenced by government motives for engagement and the extent to which the providers that are most important to poor people are engaged. * Formal policy dialogue between government and NSPs may be imperfect, unrepresentative and at times unhelpful in fragile settings. Informal dialogue - at the operational level - could more likely be where synergies can be found. * Regulation is more likely to be ‘pro-service’ where it offers incentives for compliance, and where it focuses on standards in terms of outputs and outcomes rather than inputs and entry controls. * Wide scale, performance-based contracting has been successful in delivering services in some cases, but the sustainability of this approach is often questioned. Some successful contractual agreements have a strong informal, relational element and grow out of earlier informal connections. * Informal and mutual agreements can avoid the capacity problems and tensions implicit in formal contracting but may present problems of non-transparency and exclusion of competition. Paradoxically, the need for large-scale approaches and quick co-ordination of services in fragile and conflict-affected settings may require ‘prematurely high’ levels of state-NSP engagement, before the development of the underlying institutional structures that would support them. When considering strategies to support the capacity of government to engagement with NSPs, donors should: * Recognise non-state service provision and adopt the ‘do no harm’ principle: It would be wrong to set the ambition of 'managing ‘ non-state provision in its entirety, and it can be very harmful for low-capacity states to seek to regulate all NSP or to draw it into clumsy contracts. * Beware of generalisation: Non-state provision takes many forms in response to different histories and to political and economic change. The possibilities and case for state engagement have to be assessed not assumed. The particular identities of NGOs and enterprises should be considered. * Recognise that state building can occur through any of the types of engagement with NSPs: Types of engagement should therefore be selected on the basis of their likely effectiveness in improving service delivery. * Begin with less risky/small scale forms of engagement where possible: State interventions that imply a direct controlling role for the state and which impose obligations on NSPs (i.e. contracting and regulation) require greater capacity (on both sides) and present greater risk of harm if performed badly than the roles of policy dialogue and entering into mutual agreements. * Adopt mixed approaches: The choice between forms of engagement does not have to be absolute. Rather than adopting a uniform plan of engagement in a particular country, it may be better to try different approaches in different regions or sectors