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

Earthly and unearthly powers collide: Ballads of poetry and song

No abstract available

Scotland Emergent: The story of Scotland's literature, part one: from early times to Columba

No abstract available

Chopwell Township 1851-1911 : Aspects of Residency Using A Microcosmical Approach

This thesis presents the results of an exploration into aspects of the residency of the inhabitants of four County Durham mining villages over the period 1851-1911. These four villages - Chopwell, High Spen, Blackhall Mill and Victoria Garesfield - were all within a few kilometres of each other and housed the population of a region known, historically, as Chopwell Township. Miners in High Spen and Victoria Garesfield had been working coal from the middle of the nineteenth century but major developments at Chopwell from 1895 created a new colliery village of over 5000 inhabitants by 1911. This large in-migration created some unusual conditions for this inquiry into residency. The basic data for the analysis was obtained from the on-line versions of seven Censuses (1851-1911), supported by parish registers (1890-1911) and the 1910 Property Valuation Survey. Generally the ten-year Residential Persistence rates determined for three of the villages are comparable to other published figures, while the ten-year rates of Chopwell differ. It is suggested that the low values found for Chopwell, over the decade 1901-1911, were the result of the influx of workers which created a transient period of social ‘churning’ as the migrants adjusted to their new environment. A study of the inter-censal period, 1901-1911 for Chopwell and High Spen, revealed frequent short-distance migrations with residents moving between streets. Some of these migrations seem to occur for housing reasons, either up-sizing (for larger families) or down-sizing (for smaller families). A limited examination was also made of the conjecture that the presence of large numbers of children in a household restricted mobility but the results were equivocal. To untangle the web of relationships that develop in communities it was necessary to create Household Histories. This exercise revealed ‘hidden’ illegitimate’ children, frequent re-marriages with surname changes, wider kin networks and some doubtful birthplaces