Which Fuel?

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Tractor Fuel Costs

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A geometric proof of the Kochen-Specker no-go theorem

We give a short geometric proof of the Kochen-Specker no-go theorem for non-contextual hidden variables models. Note added to this version: I understand from Jan-Aake Larsson that the construction we give here actually contains the original Kochen-Specker construction as well as many others (Bell, Conway and Kochen, Schuette, perhaps also Peres).Comment: This paper appeared some years ago, before the author was aware of quant-ph. It is relevant to recent developments concerning Kochen-Specker theorem

Assessing the cumulative environmental effects of marine renewable energy developments: establishing common ground

Assessing and managing the cumulative impacts of human activities on the environment remains a major challenge to sustainable development. This challenge is highlighted by the worldwide expansion of marine renewable energy developments (MREDs) in areas already subject to multiple activities and climate change. Cumulative effects assessments in theory provide decision makers with adequate information about how the environment will respond to the incremental effects of licensed activities and are a legal requirement in many nations. In practise, however, such assessments are beset by uncertainties resulting in substantial delays during the licensing process that reduce MRED investor confidence and limit progress towards meeting climate change targets. In light of these targets and ambitions to manage the marine environment sustainably, reducing the uncertainty surrounding MRED effects and cumulative effects assessment are timely and vital. This review investigates the origins and evolution of cumulative effects assessment to identify why the multitude of approaches and pertinent research have emerged, and discusses key considerations and challenges relevant to assessing the cumulative effects of MREDs and other activities on ecosystems. The review recommends a shift away from the current reliance on disparate environmental impact assessments and limited strategic environmental assessments, and a move towards establishing a common system of coordinated data and research relative to ecologically meaningful areas, focussed on the needs of decision makers tasked with protecting and conserving marine ecosystems and services

The effects of acceleration stress on human workload and manual control

The effects of +Gz stress on operator task performance and workload were assessed. Subjects were presented a two dimensional maze and were required to solve it as rapidly as possible (by moving a light dot through it via a trim switch on a control stick) while under G-stress at levels from +1 Gz to +6 Gz. The G-stress was provided by a human centrifuge. The effects of this stress were assessed by two techniques; (1) objective performance measures on the primary maze-solving task, and (2) subjective workload measures obtained using the subjective workload assessment technique (SWAT). It was found that while neither moderate (+3 Gz) nor high (+5 Gz and +6 Gz) levels of G-stress affected maze solving performance, the high G levels did increase significantly the subjective workload of the maze task

Editorial: In use, in situ: extending field research methods

A case for evaluating in use and in-situ Many authors have argued the need for a broader understanding of context and the situatedness of activity when approaching the evaluation of systems. However, prevailing practice often still tends towards attempting to understand the use of designed artefacts by focusing on a core set of tasks that are thought to define the system. A consequence of such focus is that other tasks are considered peripheral and outside the scope of design and evaluation activities. To illustrate the point, consider the experience, familiar to many of us, of being involved in an evaluation activity where participants provide unstructured qualitative feedback. Irrespective of whether the activity is carried out in a laboratory, in a high fidelity simulation or in a naturalistic setting, participants will frequently volunteer unsolicited feedback about tasks and goals that were not originally within the ambit of the design activity. This unprompted feedback, we suggest, is a cue for the evaluators to pay attention to the relationship between the tool and the practice in which it will be used. In other words a cue to consider the situations in which artefact will be used, the tasks and activities that may be affected by the new system, and so on. These are empirical questions that cannot be answered a priori by the development team, whether the evaluation is taking place in “artificial” or “natural” setting

‘So people know I'm a Sikh’: Narratives of Sikh masculinities in contemporary Britain

This article examines British-born Sikh men's identification to Sikhism. In particular, it focuses on the appropriation and use of Sikh symbols amongst men who define themselves as Sikh. This article suggests that whilst there are multiple ways of ‘being’ a Sikh man in contemporary post-colonial Britain, and marking belonging to the Sikh faith, there is also a collectively understood idea of what an ‘ideal’ Sikh man should be. Drawing upon Connell and Messerschmidt's discussion of locally specific hegemonic masculinities (2005. “Hegemonic Masculinity: Rethinking the Concept.” Gender and Society 19 (6): 829–859), it is suggested that an ideal Sikh masculine identity is partly informed by a Khalsa discourse, which informs a particular performance of Sikh male identity, whilst also encouraging the surveillance of young men's activities both by themselves and by others. These Sikh masculinities are complex and multiple, rotating to reaffirm, challenge and redefine contextualised notions of hegemonic masculinity within the Sikh diaspora in post-colonial Britain. Such localised Sikh masculinities may both assert male privilege and reap patriarchal dividends (Connell, W. 1995. Masculinities. Cambridge: Polity Press), resulting in particular British Sikh hegemonic masculinities which seek to shape the performance of masculinity, yet in another context these very same performances of masculinity may also signify a more marginalised masculinity vis-à-vis other dominant hegemonic forms

On the accuracy of the Perturbative Approach for Strong Lensing: Local Distortion for Pseudo-Elliptical Models

The Perturbative Approach (PA) introduced by \citet{alard07} provides analytic solutions for gravitational arcs by solving the lens equation linearized around the Einstein ring solution. This is a powerful method for lens inversion and simulations in that it can be used, in principle, for generic lens models. In this paper we aim to quantify the domain of validity of this method for three quantities derived from the linearized mapping: caustics, critical curves, and the deformation cross section (i.e. the arc cross section in the infinitesimal circular source approximation). We consider lens models with elliptical potentials, in particular the Singular Isothermal Elliptic Potential and Pseudo-Elliptical Navarro--Frenk--White models. We show that the PA is exact for this first model. For the second, we obtain constraints on the model parameter space (given by the potential ellipticity parameter $\varepsilon$ and characteristic convergence $\kappa_s$) such that the PA is accurate for the aforementioned quantities. In this process we obtain analytic expressions for several lensing functions, which are valid for the PA in general. The determination of this domain of validity could have significant implications for the use of the PA, but it still needs to be probed with extended sources.Comment: Accepted for publication in MNRA