Ion heating in the presheath

A one-dimensional model of a small plasma ion source (10cm long) is studied. A hybrid simulation where ions are treated as particles and electrons as a fluid obeying the Boltzmann relation is used to investigate ion heating in the plasma presheath. At low pressure (below a few mTorr), the ion velocity distribution is Maxwellian in the bulk and becomes a drifting Maxwellian distribution while transiting the presheath. The distribution remains essentially isotropic as the ions are accelerated through the presheath to satisfy the Bohm criterion. At intermediate pressures (around 10mTorr), ion-neutral collisions scatter a significant part of the ion kinetic energy from the parallel direction to the perpendicular direction, leading to a net heating of the ions. In addition, the ion velocity distribution becomes distinctly anisotropic. At higher pressure (above a few tens of mTorr), ion heating is still observed, but yields isotropic ion velocity distributions

Spectral Mapping Reconstruction of Extended Sources

Three dimensional spectroscopy of extended sources is typically performed with dedicated integral field spectrographs. We describe a method of reconstructing full spectral cubes, with two spatial and one spectral dimension, from rastered spectral mapping observations employing a single slit in a traditional slit spectrograph. When the background and image characteristics are stable, as is often achieved in space, the use of traditional long slits for integral field spectroscopy can substantially reduce instrument complexity over dedicated integral field designs, without loss of mapping efficiency -- particularly compelling when a long slit mode for single unresolved source followup is separately required. We detail a custom flux-conserving cube reconstruction algorithm, discuss issues of extended source flux calibration, and describe CUBISM, a tool which implements these methods for spectral maps obtained with ther Spitzer Space Telescope's Infrared Spectrograph.Comment: 11 pages, 8 figures, accepted by PAS

High brightness inductively coupled plasma source for high current focused ion beam applications

A high brightnessplasmaion source has been developed to address focused ion beam(FIB) applications not satisfied by the liquid metal ion source (LMIS) based FIB. The plasmaFIB described here is capable of satisfying applications requiring high mill rates (>100μm³/s) with non-gallium ions and has demonstrated imaging capabilities with sub- 100-nm resolution. The virtual source size, angular intensity, mass spectra, and energy spread of the source have been determined with argon and xenon. This magnetically enhanced, inductively coupled plasmasource has exhibited a reduced brightness(βr) of 5.4×10³Am⁻²sr⁻¹V⁻¹, with a full width half maximum axial energy spread (ΔE) of 10eV when operated with argon. With xenon, βr=9.1×10³Am⁻²sr⁻¹V⁻¹ and ΔE=7eV. With these source parameters, an optical column with sufficient demagnification is capable of forming a sub-25-nm spot size at 30keV and 1pA. The angular intensity of this source is nominally three orders of magnitude greater than a LMIS making the source more amenable to creating high current focused beams, in the regime where spherical aberration dominates the LMIS-FIB. The source has been operated on a two lens ion column and has demonstrated a current density that exceeds that of the LMIS-FIB for current greater than 50nA. Source lifetime and current stability are excellent with inert and reactive gases. Additionally, it should be possible to improve both the brightness and energy spread of this source, such that the (βr/ΔE₂) figure-of-merit could be within an order of magnitude of a LMIS

Good images, effective messages? Working with students and educators on academic practice understanding

Work at Northumbria University has focussed on activity that extends opportunities for students to engage directly with the skills development necessary for sound academic practice. This has included highly visual campaigns on the "Plagiarism trap", providing access to Turnitin plagiarism detection software, guides and sessions to highlight use of associated referencing tools. Sessions on a variety of topics, such as supporting study skills and reading originality reports, have been provided for students on taught, undergraduate and postgraduate programmes. This provision has included students working on collaborative partners' sites and also those on research programmes. Alongside the activities with students, "designing out" approaches have been embedded in staff development within the educator community at Northumbria. Formative use of Turnitin is integrated throughout programmes and academic practice development is formally recognised within the University Learning and Teaching Strategy's focus on information literacy. This article outlines and reviews these activities in a critical institutional context and evaluates responses from a variety of students and educators to determine how effective these measures have been

The social anatomy of 'collusion'

This paper offers a conceptual analysis of collusion, the often overlooked relative of plagiarism in debates on academic integrity. Considered as an inherently social phenomenon, we present the results of a systematic effort to understand the anatomy of collusion. The term’s meanings and associated governance practices are compared for contexts outside Higher Education (HE). These are considered alongside a thematic analysis of publicly available UK university academic integrity documentation that specifies for students what counts as collusion. We indicate how current guideline practice can (1) appear incomplete by concentrating on classroom peers, (2) create blurred boundaries around useful collaboration, peer review and dishonest practice and (3) may be so unrealistic as to have unwelcome, unintended consequences for students and staff. Taking an ecological perspective on the conditions of collusion emphasises how these guidelines - by seeking to constrain social interactions around assignment work - may create an uncomfortable incoherence between their prescriptions and well-established patterns of study

The landscape of gifted and talented education in England and Wales: How are teachers implementing policy?

This is an Author's Accepted Manuscript of an article published in Research Papers in Education, 27(2), 167-186, 2012, copyright Taylor & Francis, available online at: http://www.tandfonline.com/10.1080/02671522.2010.509514.This paper explores the evidence relating to how primary schools are responding to the ‘gifted and talented’ initiative in England and Wales. A questionnaire survey which invited both closed and open-ended responses was carried out with a national sample of primary schools. The survey indicated an increasing proportion of coordinators, compared with a survey carried out in 1996, were identifying their gifted and talented children as well as having associated school policies. However, the survey also highlighted a number of issues which need addressing if the initiative is to achieve its objective of providing the best possible educational opportunities for children. For example, it was found that a significant number of practitioners were not aware of the existence of the National Quality Standards for gifted and talented education, provided by the UK government in 2007, and the subject-specific criteria provided by the UK’s Curriculum Authority for identification and provision have been largely ignored. The process of identifying children to be placed on the ‘gifted and talented’ register seems haphazard and based on pragmatic reasons. Analysis of teachers’ responses also revealed a range of views and theoretical positioning held by them, which have implications for classroom practice. As the ‘gifted and talented’ initiative in the UK is entering a second decade, and yet more significant changes in policy are introduced, pertinent questions need to be raised and given consideration

Observed Consequences of Presupernova Instability in Very Massive Stars

This chapter concentrates on the deaths of very massive stars, the events leading up to their deaths, and how mass loss affects the resulting death. The previous three chapters emphasized the theory of wind mass loss, eruptions, and core collapse physics, but here we emphasize mainly the observational properties of the resulting death throes. Mass loss through winds, eruptions, and interacting binaries largely determines the wide variety of different types of supernovae that are observed, as well as the circumstellar environments into which the supernova blast waves expand. Connecting these observed properties of the explosions to the initial masses of their progenitor stars is, however, an enduring challenge and is especially difficult for very massive stars. Superluminous supernovae, pair instability supernovae, gamma ray bursts, and "failed" supernovae are all end fates that have been proposed for very massive stars, but the range of initial masses or other conditions leading to each of these (if they actually occur) are still very certain. Extrapolating to infer the role of very massive stars in the early universe is essentially unencumbered by observational constraints and still quite dicey.Comment: 39 pages, 5 figures, to appear as chapter in the book "Very Massive Stars in the Local Universe", ed. J. Vin

Switching the stereochemical outcome of 6-endo-trig cyclizations; Synthesis of 2,6-Cis-6-substituted 4-oxopipecolic acids

A base-mediated 6-endo-trig cyclization of readily accessible enone-derived α-amino acids has been developed for the direct synthesis of novel 2,6-cis-6- substituted-4-oxo-L-pipecolic acids. A range of aliphatic and aryl side chains were tolerated by this mild procedure to give the target compounds in good overall yields. Molecular modeling of the 6-endo-trig cyclization allowed some insight as to how these compounds were formed, with the enolate intermediate generated via an equilibrium process, followed by irreversible tautomerization/neutralization providing the driving force for product formation. Stereoselective reduction and deprotection of the resulting 2,6-cis-6-substituted 4-oxo-L-pipecolic acids to the corresponding 4-hydroxy-L-pipecolic acids was also performed

Identifying the science and technology dimensions of emerging public policy issues through horizon scanning

Public policy requires public support, which in turn implies a need to enable the public not just to understand policy but also to be engaged in its development. Where complex science and technology issues are involved in policy making, this takes time, so it is important to identify emerging issues of this type and prepare engagement plans. In our horizon scanning exercise, we used a modified Delphi technique [1]. A wide group of people with interests in the science and policy interface (drawn from policy makers, policy adviser, practitioners, the private sector and academics) elicited a long list of emergent policy issues in which science and technology would feature strongly and which would also necessitate public engagement as policies are developed. This was then refined to a short list of top priorities for policy makers. Thirty issues were identified within broad areas of business and technology; energy and environment; government, politics and education; health, healthcare, population and aging; information, communication, infrastructure and transport; and public safety and national security.Public policy requires public support, which in turn implies a need to enable the public not just to understand policy but also to be engaged in its development. Where complex science and technology issues are involved in policy making, this takes time, so it is important to identify emerging issues of this type and prepare engagement plans. In our horizon scanning exercise, we used a modified Delphi technique [1]. A wide group of people with interests in the science and policy interface (drawn from policy makers, policy adviser, practitioners, the private sector and academics) elicited a long list of emergent policy issues in which science and technology would feature strongly and which would also necessitate public engagement as policies are developed. This was then refined to a short list of top priorities for policy makers. Thirty issues were identified within broad areas of business and technology; energy and environment; government, politics and education; health, healthcare, population and aging; information, communication, infrastructure and transport; and public safety and national security