The ASCA Spectrum of the Vela Pulsar Jet

ROSAT observations of the Vela pulsar and its surroundings revealed a collimated X-ray feature almost 45' in length (Markwardt & Ogelman 1995), interpreted as the signature ``cocoon'' of a one-sided jet from the Vela pulsar. We report on a new ASCA observation of the Vela pulsar jet at its head, the point where the jet is believed to interact with the supernova remnant. The head is clearly detected, and its X-ray spectrum is remarkably similar to the surrounding supernova remnant spectrum, extending to X-ray energies of at least 7 keV. A ROSAT+ASCA spectrum can be fit by two-component emission models but not standard one-component models. The lower energy component is thermal and has a temperature of 0.29+/-0.03 keV (1 sigma); the higher energy component can be fit by either a thermal component of temperature ~4 keV or a power law with photon index ~2.0. Compared to the ROSAT-only results, the mechanical properties of the jet and its cocoon do not change much. If the observed spectrum is that of a hot jet cocoon, then the speed of the jet is at least 800 km s^-1, depending on the angle of inclination. The mechanical power driving the jet is >10^36 erg s^-1, and the mass flow rate at the head is > 10^-6 M_sun yr^-1. We conclude that the jet must be entraining material all along its length in order to generate such a large mass flow rate. We also explore the possibility that the cocoon emission is synchrotron radiation instead of thermal.Comment: 12 pages, LaTeX in AAS v4.0 preprint style, two PS figures, accepted for publication in the ApJ Letter

Searching for annihilation radiation from SN 1006 with SPI on INTEGRAL

Historical Type Ia supernovae are a leading candidate for the source of positrons observed through their diffuse annihilation emission in the Galaxy. However, search for annihilation emission from individual Type Ia supernovae has not been possible before the improved sensitivity of \integral. The total 511 keV annihilation flux from individual SNe Ia, as well as their contribution to the overall diffuse emission, depends critically on the escape fraction of positrons produced in $^{56}$Co decays. Late optical light curves suggest that this fraction may be as high as 5%. We searched for positron annihilation radiation from the historical Type Ia supernova SN 1006 using the SPI instrument on \integral. We did not detect significant 511 keV line emission, with a 3$\sigma$ flux upper limit of 0.59 x 10$^{-4}$ ergs cm^-2 s^-1 for \wsim 1 Msec exposure time, assuming a FWHM of 2.5 keV. This upper limit corresponds to a 7.5% escape fraction, 50% higher than the expected 5% escape scenario, and rules out the possibility that Type Ia supernovae produce all of the positrons in the Galaxy (~ 12% escape fraction), if the mean positron lifetime is less than 10$^{5}$ years. Future observations with \integral will provide stronger limits on the escape fraction of positrons, the mean positron lifetime, and the contribution of Type Ia supernovae to the overall positron content of the Galaxy.Comment: 3 pages, 2 figures, accepted for publication in ApJ

Radio Emission from the Composite Supernova Remnant G326.3-1.8 (MSH15-56)

High resolution radio observations of the composite supernova remnant (SNR) G326.3-1.8 or MSH 15-56 with the Australia Telescope Compact Array show details of both the shell and the bright plerion which is offset about 1/3 of the distance from the center of the SNR to the shell. The shell appears to be composed of thin filaments, typical of older shell SNRs. The central part of the elongated plerion is composed of a bundle of parallel ridges which bulge out at the ends and form a distinct ring structure on the northwestern end. The magnetic field with a strength of order 45 microGauss, is directed along the axis of the ridges but circles around the northwestern ring. This plerion is large and bright in the radio but is not detected in x-ray or optical wavelengths. There is, however, a faint hard x-ray feature closer to the shell outside the plerion. Perhaps if the supernova explosion left a rapidly moving magnetar with large energy input but initially rapid decay of both relativistic particles and magnetic field, the observed differences with wavelength could be explained.Comment: 15 pages, 10 figures, accepted by Ap

The reliability and validity of a field hockey skill test

High test retest reliability is essential in tests used for both scientific research and to monitor athletic performance. Thirty-nine (20 male and 19 female) well-trained university field hockey players volunteered to participate in the study. The reliability of the in house designed test was determined by repeating the test (3-14 days later) following full familiarisation. The validity was assessed by comparing coaches ranks of players with ranked performance on the skill test. The mean difference and confidence limits in overall skill test performance was 0.0 ± 1.0% and the standard error (confidence limits) was 2.1% (1.7 to 2.8%). The mean difference and confidence limits for the ‘decision making’ time was 0.0 ± 1.0% and the standard error (confidence limits) was 4.5% (3.6 to 6.2%). The validity correlation (Pearson) was r = 0.83 and r= 0.73 for female players and r = 0.61 and r = 0.70 for male players for overall time and ‘decision making’ time respectively. We conclude that the field hockey skill test is a reliable measure of skill performance and that it is valid as a predictor of coach assessed hockey performance, but the validity is greater for female players

Criminalising neonaticide: reflections on law and practice in England and Wales

This chapter considers the unusual case where a woman is suspected of killing her newborn baby following a secret pregnancy and birth. The research on what we know about the circumstances and incidence of what has been termed ‘neonaticide’ is explored. The complexities of these cases in terms of their circumstances and the vulnerability of women who conceal their pregnancies are highlighted. Following this, the difficulties, from a legal perspective, that arise when seeking to prosecute women for homicide when their babies die following an unassisted concealed birth are considered. What we know about current criminal justice practice in these cases is also explored. Unfortunately, there is limited research on current criminal justice practice in these cases, and little is therefore known about the approach taken by the police, prosecutors and the courts in cases involving suspected homicides of newborns. The need for further research on the criminal justice response is highlighted, and the appropriateness of criminalising women and girls in these cases, particularly given their unique circumstances of vulnerability, is questioned

Surveying the Creative Use of Vacant Space in London, c.1945-95

This paper draws on a Leverhulme-funded research project entitled ‘Interim spaces and creative use’ (2012-2014). The project investigated five present-day temporary projects sited on vacant land in London. Conscious of the long history of creative temporary occupations, the project pushes against the ephemeral nature of interim projects of the past, strategically documenting the five case studies through interviews, film, site surveys and photographs. The specific purpose of this paper is to contextualise this recent fieldwork against the wider historical background of the creative temporary uses of vacant urban space, therefore negotiating between definitions of ‘vacant’ and ‘empty’. Vacant spaces have been historically associated with dereliction or abandonment, ‘lost space’ (Trancik 1986), ‘urban voids’ and ‘cracks in the city’ (Loukaitou-Sideris 1996). Against the perception of vacancy as waste and emptiness, a more positive reading has been promoted through the notion of the ‘terrain vague’ (de Sola-Morales 1995). Although the present-day case studies emerged out of a very particular political, economic and cultural context, that of the late-2000s recession, this is not the first time that temporary uses have emerged in the history of London. Some of the case studies of the research project are located on sites with legacies of use that stretch back far beyond the 20th century and such histories complicate our readings of these short-term projects. The paper is however primarily concerned with the post-war context of London, up to the present day. Using the case studies as a spur for reflection, it provides an overview of the key moments in the evolution of creative temporary projects developed in vacant spaces. The discussion also highlights links between past and present projects. Setting out from the post-war reconstruction years, the paper explores the 1960s countercultural projects as well as the 1970s post-countercultural community garden movement and the urban ecology turn. It then considers the impact of an increasingly global environmental awareness in the 1980s, leading up to the 1990s regeneration boom. This broad survey is supported by specific historical examples of creative use - some of which have proved to be truly temporary whilst others have managed to endure - explored through published material, interviews with initiators and archival photographic records. Through this historical review the paper links London projects to wider movements worldwide, with particular references to US and Europe where a direct influence can be established. Key themes emerging that provide insights into practices and ideologies relating to ‘emptiness’ are discussed and their legacies for contemporary urban projects identified. The paper observes that there has been a historical evolution in how ‘empty space’ has been discovered, made visible and reimagined in 20th century London, and highlights its relevance for today’s vacant urban spaces

Requirements Engineering as Creative Problem Solving: A Research Agenda for Idea Finding

This vision paper frames requirements engineering as a creative problem solving process. Its purpose is to enable requirements researchers and practitioners to recruit relevant theories, models, techniques and tools from creative problem solving to understand and support requirements processes more effectively. It uses 4 drivers to motivate the case for requirements engineering as a creative problem solving process. It then maps established requirements activities onto one of the longest-established creative problem solving processes, and uses these mappings to locate opportunities for the application of creative problem solving in requirements engineering. The second half of the paper describes selected creativity theories, techniques, software tools and training that can be adopted to improve requirements engineering research and practice. The focus is on support for problem and idea finding - two creative problem solving processes that our investigation revealed are poorly supported in requirements engineering. The paper ends with a research agenda to incorporate creative processes, techniques, training and tools in requirements projects

Tensor products of banach spaces

Chapter one consists of a general discussion of tensor products. Chapter two is concerned with the relationship between tensor products and the approximation property. In Theorem 2.1 we give an equivalent condition to the approximation property which is due to Grothendieck. In Theorem 2.5 we prove that every complex Banach space is isometrically isomorphic to a complemented subspace of a uniform algebra. From this, we prove in Theorem 2.6 that there exists a uniform algebra not having the approximation property. Tomiyama has shown that if A and B are semi-simple commutative Banach algebras, and either A or B has the approximation property, then A ⊗^ B is semi -simple. In Theorem 2.8 we establish a converse to this result, namely that if A is a commutative Banach algebra not having the approximation property, then there is a uniform algebra B such that A ⊗^0 B is not semi -simple. We next discuss the c- product and the slice product, and their relationships with the injective tensor product and with the approximation property. Then, in Theorem 2.11, we prove that a uniform algebra A has the approximation property if and only if A ⊗^ B = A # B for all uniform algebras B. In chapter three we consider injective algebras. Using techniques similar to those used in the proof of Theorem 2.5, we give a proof in Theorem 3.2 of Varopoulos's characterisation of injective commutative Banach-algebras. This states that a commutative Banachalgebra A is injective if and only if there exists a uniform algebra B, a bounded algebra homomorphism h of B onto A, and a bounded linear operator j of A into B such that hₒj = Iₐ. In Theorem 3.4 we prove a sharpening of Varopoulos's result that a normed-algebra is injective if and only if its injective tensor product with any normed-algebra is a normed-algebra. Chapter four is concerned with the question, also considered in chapter three, of whether the injective tensor product of two normed-algebras is a normed-algebra. We show that this is the case for the tensor product 1ₚ ⊗ᵛ lq (where p or q ≤ 2), and for the tensor product of two Banach- algebras which are ℓ₁ spaces. In chapter five we consider measures orthogonal to injective tensor products of uniform algebras, and we obtain an analogue of Cole's decomposition theorem for orthogonal measures to the bidisc algebra. Through a general study of bands, we set up the decomposition in Lemma 5.4, and prove that this decomposition is of the form we want in Theorem 5.7. This then gives us our main result in Theorem 5.8