A spectral difference between silicates in Comet Halley and interstellar silicates

The authors obtained an intermediate resolution (1 percent) spectrum of the 8 to 13 micron region in Comet Halley which shows a prominent silicate emission feature with structure not observed before in other comets or in interstellar silicates. They confirm the presence of a strong 11.3 micron peak reported by Bregman et al. (1987) and find evidence for additional structure in the band. The 11.3 micron peak represents the main difference between the Halley Spectrum and that of Comet Kohoutek. The Kohoutek Spectrum is similar to that of the circumstellar shell around mu Ceph. Based on a comparison with the spectra of Interplanetary Dust Particles (Sandford and Walker 1985), most of which are believed to be of cometary origin, the authors attribute the 11.3 micron peak to small crystalline olivine particles, although other minerals cannot be ruled out. Their interpretation is supported by the airborne observation of four emission peaks near 24, 28, 35 and 45 microns which can also be matched with iron-magnesium silicates including crystalline olivine. Other types of silicates (such as hydrated or amorphous) are necessary to explain the width and the 9.7 micron peak of the emission observed in Comet Halley

Italy and the Sanusiyya: Negotiating Authority in Colonial Libya, 1911-1931

In the first decade of their occupation of the former Ottoman territories of Tripolitania and Cyrenaica in current-day Libya, the Italian colonial administration established a system of indirect rule in the Cyrenaican town of Ajedabiya under the leadership of Idris al-Sanusi, a leading member of the Sufi order of the Sanusiyya and later the first monarch of the independent Kingdom of Libya after the Second World War. Post-colonial historiography of modern Libya depicted the Sanusiyya as nationalist leaders of an anti-colonial rebellion as a source of legitimacy for the Sanusi monarchy. Since Qaddafi's revolutionary coup in 1969, the Sanusiyya all but disappeared from Libyan historiography as a generation of scholars, eager to fill in the gaps left by the previous myopic focus on Sanusi elites, looked for alternative narratives of resistance to the Italian occupation and alternative origins for the Libyan nation in its colonial and pre-colonial past. Their work contributed to a wider variety of perspectives in our understanding of Libya's modern history, but the persistent focus on histories of resistance to the Italian occupation has missed an opportunity to explore the ways in which the Italian colonial framework shaped the development of a religious and political authority in Cyrenaica with lasting implications for the Libyan nation. As a latecomer to the European "Scramble for Africa", the Italian occupation of the Libyan territories has received little attention in Italian historiography or in larger works on late European imperialism. The perception that the Italian colonial project in North Africa was too short and insignificant to merit serious analysis persists in Italian intellectual and public discourses, but the Italian occupation of the Libyan territories represented a critical moment of national formation in Italy. Coming just four decades after the territorial unification of the Kingdom of Italy in 1870, the movement to invade the Libyan coast and subsequent debates concerning methods of colonial rule reflected conflicting visions of the type of nation Italy should become as it attempted to expand overseas. In the years leading up to the invasion of the Libyan coast in 1911 and for the following decade, the Italian colonial administration largely adhered to a liberal ideal of indirect rule by appealing to Muslim elites even while the Occupying Forces engaged in a frequently brutal repression of armed rebellion. The attempts of Italian administrators to negotiate a power-sharing system with Sanusi elites placed them in an international competition among imperial powers jockeying for influence in Muslim North Africa. A perception of the Sanusiyya as a highly centralized and powerful organization capable of calling on the loyalties of Muslims throughout the region inspired the Ottoman Sultan Abdulhamid II to arm the Sanusi zawāyā or religious centers at the end of the nineteenth century in the hopes that the Sanusi elite would lead local populations against European expansion. Subsequent colonial administrations in the region courted the favor of the spiritual leader of the Sufi order, Ahmad al-Sharif, despite the widespread doubts concerning the extent and nature of his political authority among the region's tribal leaders. When it became clear that the recognized head of the Sufi order, Ahmad al-Sharif, would not lend his support to pacifying the Cyrenaican interior, the Italian administration, with a strong push from British officials in Egypt, identified his cousin Idris al-Sanusi as an alternative intermediary who could generate consensus for Italian rule. From 1916 until 1923, the Italian state cultivated Idris al-Sanusi's authority by providing him with armed forces and allowing him to adopt the symbols of government in a semi-autonomous emirate in the Cyrenaican interior. An invitation from a group of Tripolitanian notables for Idris al-Sanusi to extend his emirate into the western region precipitated the decision of the fascist Ministry of Colonies, Luigi Federzoni, to denounce previous negotiations with the Sanusiyya in 1923, and he expressed concerns that the Italian state had created a political authority where one did not exist, rewarded Italy's enemies, and invested misplaced trust in a regional leader that proved unable or unwilling to generate consensus for Italian colonial rule. Idris al-Sanusi left the Libyan territories for Cairo where he remained in exile until the United Nations placed him on the throne of the independent Kingdom of Libya. With the departure of Idris al-Sanusi and the dissolution of the Sanusi emirate, Federzoni and his administration initiated a program of territorial expansion to fulfill the nationalist quest for land in the Libyan interior. In the late 1920s, Italy initiated a series of brutal military campaigns culminating in the capture and hanging of the Sanusi shaykh Omar al-Mukthar in 1931. This dissertation explores the Italian approach to colonial rule in eastern Libya as a reflection of internal national struggles over the relationship between religious and political authority and as a formative moment in the political history of the Libyan nation

Continuum modeling of catastrophic collisions

A two dimensional hydrocode based on 2-D SALE was modified to include strength effects and fragmentation equations for fracture resulting from tensile stress in one dimension. Output from this code includes a complete fragmentation summary for each cell of the modeled object: fragment size (mass) distribution, vector velocities of particles, peak values of pressure and tensile stress, and peak strain rates associated with fragmentation. Contour plots showing pressure and temperature at given times within the object are also produced. By invoking axial symmetry, three dimensional events can be modeled such as zero impact parameter collisions between asteroids. The code was tested against the one dimensional model and the analytical solution for a linearly increasing tensile stress under constant strain rate

Understanding asteroid collisional history through experimental and numerical studies

Asteroids can lose angular momentum due to so called splash effect, the analog to the drain effect for cratering impacts. Numerical code with the splash effect incorporated was applied to study the simultaneous evolution of asteroid sized and spins. Results are presented on the spin changes of asteroids due to various physical effects that are incorporated in the described model. The goal was to understand the interplay between the evolution of sizes and spins over a wide and plausible range of model parameters. A single starting population was used both for size distribution and the spin distribution of asteroids and the changes in the spins were calculated over solar system history for different model parameters. It is shown that there is a strong coupling between the size and spin evolution, that the observed relative spindown of asteroids approximately 100 km diameter is likely to be the result of the angular momentum splash effect

Surveys, Astrometric Follow-up & Population Statistics

Asteroid surveys are the backbone of asteroid science, and with this in mind we begin with a broad review of the impact of asteroid surveys on our field. We then provide a brief history of asteroid discoveries so as to place contemporary and future surveys in perspective. Surveys in the United States have discovered the vast majority of the asteroids and this dominance has been consolidated since the publication of Asteroids III. Our descriptions of the asteroid surveys that have been operational since that time are focussed upon those that have contributed the vast majority of asteroid observations and discoveries. We also provide some insight into upcoming next-generation surveys that are sure to alter our understanding of the small bodies in the inner solar system and provide evidence to untangle their complicated dynamical and physical histories. The Minor Planet Center, the nerve center of the asteroid discovery effort, has improved its operations significantly in the past decade so that it can manage the increasing discovery rate, and ensure that it is well-placed to handle the data rates expected in the next decade. We also consider the difficulties associated with astrometric follow-up of newly identified objects. It seems clear that both of these efforts must operate in new modes in order to keep pace with expected discovery rates of next-generation ground- and space-based surveys.Comment: Chapter to appear in the book ASTEROIDS IV, (University of Arizona Press) Space Science Series, edited by P. Michel, F. DeMeo and W. Bottk

Building visual artists' resilience capabilities: current educator strategies and methods

Enrolments in higher education programs in the creative and performing arts are increasing in many countries. Yet graduates of these degrees, who enter the broad sector known as the creative industries, face particular challenges in terms of securing long-term and sustainable employment. In addition, creative and performing artists face a range of mental challenges, caused by such factors as: the solitary nature of much creative practice, critical feedback by audiences and gatekeepers, or the general pressures associated with maintaining artistic relevance or integrity. The concepts of resilience and professional wellbeing are therefore highly relevant to those who pursue a career in creative industries, and while there has been an emerging body of work in this area, to date it has focussed on the performing arts area (e.g. music, theatre). Hence, in order to expand knowledge relevant to resilience and artists, this paper sets out to explore the extent to which current educators in the Australian context specifically address these issues within higher visual arts curricula; specifically the areas of illustration, design, film and photography. This was achieved via interviews with seventeen current academics working in these areas. The findings propose that higher education providers of programs in the visual arts consider placing a stronger emphasis on the embedded development of resilience and professional wellbeing capacities

Building visual artists' resilience capabilities: current educator strategies and methods

Enrolments in higher education programs in the creative and performing arts are increasing in many countries. Yet graduates of these degrees, who enter the broad sector known as the creative industries, face particular challenges in terms of securing long-term and sustainable employment. In addition, creative and performing artists face a range of mental challenges, caused by such factors as: the solitary nature of much creative practice, critical feedback by audiences and gatekeepers, or the general pressures associated with maintaining artistic relevance or integrity. The concepts of resilience and professional wellbeing are therefore highly relevant to those who pursue a career in creative industries, and while there has been an emerging body of work in this area, to date it has focussed on the performing arts area (e.g. music, theatre). Hence, in order to expand knowledge relevant to resilience and artists, this paper sets out to explore the extent to which current educators in the Australian context specifically address these issues within higher visual arts curricula; specifically the areas of illustration, design, film and photography. This was achieved via interviews with seventeen current academics working in these areas. The findings propose that higher education providers of programs in the visual arts consider placing a stronger emphasis on the embedded development of resilience and professional wellbeing capacities