Polarized Helium to Image the Lung

The main findings of the european PHIL project (Polarised Helium to Image the Lung) are reported. State of the art optical pumping techniques for polarising ^3He gas are described. MRI methodological improvements allow dynamical ventilation images with a good resolution, ultimately limited by gas diffusion. Diffusion imaging appears as a robust method of lung diagnosis. A discussion of the potential advantage of low field MRI is presented. Selected PHIL results for emphysema are given, with the perspectives that this joint work opens up for the future of respiratory medicine.Comment: To be published in Proc. ICAP 2004 (19th Int. Conf. on Atomic Physics, Rio, July 26-30 2004

Decision under Uncertainty : the Classical Models

This chapiter of a collective book is dedicated to classical decision models under uncertainty, i.e. under situations where events do not have "objective" probabilities with which the Decision Marker agrees. We present successively the two main theories, their axiomatic, the interpretation and the justification of their axioms and their main properties : first, the general model of Subjective Expected Utility due to Savage (Savage, 1954), second, the Anscombe-Aumann (1963) theory, in a different framework. Both theories enforce the universal use of a probabilistic representation. We then discuss this issue in connection with the experimental result known as the Ellsberg paradox.Uncertainty, subjective probability, Subjective Expected Utility, Savage, Anscombe and Aumann, Ellsberg paradox.

Decision under risk : The classical Expected Utility model

This chapter of a collective book aims at presenting the basics of decision making under risk. We first define notions of risk and increasing risk and recall definitions and classifications (that are valid independently of any representation) of behavior under risk. We then review the classical model of expected utility due to von Neumann and Morgenstern andd its main properties. Issues raised by this model are then discussed and two models generalizing the expected utility model are briefly discussed.Risk, risk aversion, expected utility, von Neumann and Morgenstern, Allais paradox.

Dangerosité et pratique criminologique en milieu adulte

After a brief review of the criticism leveled at the definitions and use of dangerousness, this article examines how criminol-ogists work with it on a daily basis within the adult justice system.We first describe the important place it occupies in their practice, notably in their work of evaluating and treating the clientèle. Next we analyze the process by which criminologists effect the social reconstruction of their clients' dangerousness. To do this, we ascertain how criminologists categorize the clientèle as dangerous or not dangerous, and also show the influence of the practice on the process by which criminologists define dangerousness

Primary Schools Facing Challenging Circumstances: Effective leadership and the potential contribution of complexity theory.

Abstract Schools operate in a multitude of different contexts, with some facing more difficult situations than others. The central question this research seeks to investigate is, ‘What happens in primary schools facing challenging circumstances that results in their improvement or decline?’ It reports on a study of three English primary schools either subject to an Ofsted (Office for Standards in Education) improvement category following inspection and/or coping without a permanent headteacher or with a school merger. It seeks to explore the existence of common factors across the different circumstances and examines the leadership characteristics associated with improvement or decline. Each of the case study schools is also examined more holistically through a complexity theory lens to determine the extent to which this view might add to current understanding. The study is unusual in that, in the past, researchers have found it difficult to gain access to such sensitive contexts. The researcher in this case was seconded to the leadership team within one of the case study schools for six months and used a journal as well as participant observation and interviews to gather data. Existing literature identifies circumstances deemed to be challenging and explores a range of aspects of leadership including the difficulties associated with it. This research identifies common themes in primary schools facing challenging circumstances, with a particular focus on leadership, and explores further the links between them, the networks they create and the contribution that these combinations might make to improvement or decline. The original contribution made by this research is to establish complexity theory as a useful approach in examining the nexus between school leadership and primary schools facing challenging circumstances, including a proposition for representing these complex school systems. It seeks to support identification of early indicators of a range of problematic circumstances (pressure nodes) and those factors potentially enabling improvement (building nodes), through the creation of network maps

Symmetries, Currents and Conservation Laws of Self-Dual Gravity

We describe an infinite-dimensional algebra of hidden symmetries for the self-dual gravity equations. Besides the known diffeomorphism-type symmetries (affine extension of w(infinity) algebra), this algebra contains new hidden symmetries, which are an affine extension of the Lorentz rotations. The full symmetry algebra has both Kac-Moody and Virasoro-like generators, whose exponentiation maps solutions of the field equations to other solutions. Relations to problems of string theories are briefly discussed.Comment: 14 pages, LaTeX, the paper was reformatte

Controlled release properties and final macroporosity of a pectin microspheres–calcium phosphate composite bone cement

The use of calcium phosphate cements (CPC) is restricted by their lack of macroporosity and poor drug release properties. To overcome these two limitations, incorporating degradable polymer microparticles into CPC is an attractive option, as polymer microparticles could help to control drug release and induce macroporosity after degradation. Although few authors have yet tested synthetic polymers, the potentiality of polysaccharides’ assuming this role has never been explored. Low-methoxy amidated pectins (LMAP) constitute valuable candidates because of their biocompatibility and ionic and pH sensitivity. In this study, the potentiality of a LMAP with a degree of esterification (DE) of 30 and a degree of amidation (DA) of 19 was explored. The aim of this study was to explore the influence of LMAP microspheres within the composite on the cement properties, drug release ability and final macroporosity after microspheres degradation. Three LMAP incorporation ratios, 2%, 4% and 6% w/w were tested, and ibuprofen was chosen as the model drug. In comparison with the CPC reference, the resulting composites presented reduced setting times and lowered the mechanical properties, which remained acceptable for an implantation in moderate-stress-bearing locations. Sustained release of ibuprofen was obtained on at least 45 days, and release rates were found to be controlled by the LMAP ratio, which modulated drug diffusion. After 4 months of degradation study, the resulting CPC appeared macroporous, with a maximum macroporosity of nearly 30% for the highest LMAP incorporation ratio, and interconnectivity between pores could be observed. In conclusion, LMAP appear as interesting candidates to generate macroporous bone cements with tailored release properties and macroporosity by adjusting the pectin content within the composites