Decoherence of quantum wavepackets due to interaction with conformal spacetime fluctuations

One of the biggest problems faced by those attempting to combine quantum theory and general relativity is the experimental inaccessibility of the unification scale. In this paper we show how incoherent conformal waves in the gravitational field, which may be produced by quantum mechanical zero-point fluctuations, interact with the wavepackets of massive particles. The result of this interaction is to produce decoherence within the wavepackets which could be accessible in experiments at the atomic scale. Using a simple model for the coherence properties of the gravitational field we derive an equation for the evolution of the density matrix of such a wavepacket. Following the primary state diffusion programme, the most promising source of spacetime fluctuations for detection are the above zero-point energy fluctuations. According to our model, the absence of intrinsic irremoveable decoherence in matter interferometry experiments puts bounds on some of the parameters of quantum gravity theories. Current experiments give \lambda > 18. , where \lambda t_{Planck} is an effective cut-off for the validity of low-energy quantum gravity theories.Comment: REVTeX forma

The Accuracy of Subhalo Detection

With the ever increasing resolution of N-body simulations, accurate subhalo detection is becoming essential in the study of the formation of structure, the production of merger trees and the seeding of semi-analytic models. To investigate the state of halo finders, we compare two different approaches to detecting subhaloes; the first based on overdensities in a halo and the second being adaptive mesh refinement. A set of stable mock NFW dark matter haloes were produced and a subhalo was placed at different radii within a larger halo. SUBFIND (a Friends-of-Friends based finder) and AHF (an adaptive mesh based finder) were employed to recover the subhalo. As expected, we found that the mass of the subhalo recovered by SUBFIND has a strong dependence on the radial position and that neither halo finder can accurately recover the subhalo when it is very near the centre of the halo. This radial dependence is shown to be related to the subhalo being truncated by the background density of the halo and originates due to the subhalo being defined as an overdensity. If the subhalo size is instead determined using the peak of the circular velocity profile, a much more stable value is recovered. The downside to this is that the maximum circular velocity is a poor measure of stripping and is affected by resolution. For future halo finders to recover all the particles in a subhalo, a search of phase space will need to be introduced.Comment: 9 pages, 7 figures, accepted for publication in MNRA

Coopetition in Fresh Food Supply Chains: The Integration Of Supply Chains and Logistical Functions amongst Competitors

This study aimed to investigate whether coopetition as a strategy could be successfully implemented within the logistical function of the Irish fresh fruit and vegetable industry as a method to improve transport costs and efficiency, as well as demand forecasting techniques, storage costs and the potential for new local and international business opportunities. Effective management of fresh food supply chains is particularly challenging due to the highly perishable nature of the product involved in the process. (Dabbene, 2008). This has an underlying effect on the final cost and quality of the product being delivered to the customer, and therefore it is imperative that the supply chain is not only efficient but accurate in terms of forecasting of orders, delivery schedules etc. The problems associated with the inaccuracy in the forecasting of orders is demonstrated by the Forrester effect or bullwhip effect whereby demand variance caused by a minor disturbance at one end of the supply chain is amplified significantly throughout the echelons of a supply chain, resulting in considerable excess produce at the consumer end. Considerable waste is frequently reported throughout these fresh food supply chains due to product deterioration. Coopetition is a strategy in which competitors cooperate with each other in order to expand their markets and increase the business pie, and compete with each other for a share of the business. Coopetition within the fresh food supply chain could be a possible solution to the problems associated with transport efficiency, and could lead to further improvements within the fresh food industry. “The term coopetition defines the modern corporate strategy that combines competition and cooperation.” (Bigliardi, 2011). The study also aimed to identify the critical success factors required for implementation of coopetition. The main research questions to be addressed by the study are as follows: • How the co-opetition theory can be applied successfully to the logistical function within a fresh food supply chain? • What factors are involved in ensuring all parties see considerable benefits from this partnership? • The impact coopetition can have on an organization in terms of forecasting, transport costs, storage, increased business opportunities? • How coopetition can be used as a strategy to improve efficiency within a short life cycle supply chain? Methodology The coopetition strategy is discussed more in depth in the Literature Review section. A conceptual framework of key variables is developed to guide the empirical part of this study. The analysis was conducted in the form of a research based case study, in which information was collected through the use of qualitative questionnaires and interviews with managing directors and logistics managers of various companies in the fresh food sector. The company involved in the case study was a typical Irish SME operating within the fresh fruit and vegetable industry, and attempts were made to identify suitable candidates to partner with the company in terms of transport sharing. Findings The results from the study highlighted the general consensus that whilst food producers and growers within Ireland do not currently utilize coopetition as a strategy within their supply chains, 60% of respondents agreed that coopetition within the logistical function of a fresh food supply chain could be applied successfully, and is a strategy they would consider implementing within their own organization. A further 20% of respondents agreed that while coopetition in terms of transport may not necessarily be ideal for their organisation, coopetition within other areas of the organisation would be of huge benefit. Organisations were receptive to the concept of coopetition, and although they rated the current efficiency of their transport system as effective, recognised that there was room for improvement within the processes governing the transport system. All respondents indicated high levels of competition within the fresh food industry, and this in addition to potential for both local and international business opportunities could be the possible driving forces behind the responsiveness to a coopetition strategy. This in conjunction with organizations positive response to coopetition implies that the strategy could be implemented successfully within this supply chain field. The findings from the study highlighted the general consensus that local produce suppliers within the Irish fresh fruit and vegetable industry were receptive to the idea of implementing coopetition within their transport departments, to improve the current efficiency of their supply chain and allow for the possibility of new business opportunities. The study showed that managers were committed to new initiatives and most organizations had the critical factors in place for successful coopetition. However, the findings raised the point that a retailer governed supply chain may have an effect on the successful implementation of coopetition within this industry.\ Contribution The results indicate a positive response to the strategy and therefore the commitment and enthusiasm to drive the strategy as clearly evident within the Irish industry. The research collected provides solid background knowledge for future researchers to further collaborate on, and with the cooperation of the Irish Food Board, it is predicted that this strategy could be used successfully within the local fresh fruit and vegetable industry to improve transport efficiency

The limits of the rotating wave approximation in the electromagnetic field propagation in a cavity

We consider three two-level atoms inside a one-dimensional cavity, interacting with the electromagnetic field in the rotating wave approximation (RWA), commonly used in the atom-radiation interaction. One of the three atoms is initially excited, and the other two are in their ground state. We numerically calculate the propagation of the field spontaneously emitted by the excited atom and scattered by the second atom, as well as the excitation probability of the second and third atom. The results obtained are analyzed from the point of view of relativistic causality in the atom-field interaction. We show that, when the RWA is used, relativistic causality is obtained only if the integrations over the field frequencies are extended to $-\infty$; on the contrary, noncausal tails remain even if the number of field modes is increased. This clearly shows the limit of the RWA in dealing with subtle problems such as relativistic causality in the atom-field interaction.Comment: 13 pages, 6 figure

Gulfs of Expectation: Eliciting and Verifying Differences in Trust Expectations using Personas

Personas are a common tool used in Human Computer Interaction to represent the needs and expectations of a system’s stakeholders, but they are also grounded in large amounts of qualitative data. Our aim is to make use of this data to anticipate the differences between a user persona’s expectations of a system, and the expectations held by its developers. This paper introduces the idea of gulfs of expectation – the gap between the expectations held by a user about a system and its developers, and the expectations held by a developer about the system and its users. By evaluating these differences in expectation against a formal representation of a system, we demonstrate how differences between the anticipated user and developer mental models of the system can be verified. We illustrate this using a case study where persona characteristics were analysed to identify divergent behaviour and potential security breaches as a result of differing trust expectations

Patient-reported outcomes following flexible sigmoidoscopy screening for colorectal cancer in a demonstration screening programme in the UK

<p>OBJECTIVES: Flexible sigmoidoscopy (FS) screening for colorectal cancer will be introduced into the National Cancer Screening Programmes in England in 2013. Patient-reported outcome measures (PROMs) from trial participants indicate high acceptability and no adverse physical or psychological consequences, but this may not generalize to routine screening in the community. This study examined PROMs in a community-based FS screening programme.</p> <p>METHODS: Eligible adults aged 58-59 (n = 2016) registered at 34 London general practices were mailed a National Health Service-endorsed invitation to attend FS screening. Pain and side-effects were assessed in a 'morning-after' questionnaire, and satisfaction was assessed in a three-month follow-up questionnaire. Anxiety, self-rated health and colorectal symptoms were assessed at prescreening and follow-up.</p> <p>RESULTS: In total, 1020 people attended screening and were included in the current analyses, of whom 913 (90%) returned the morning-after questionnaire, and 674 (66%) the follow-up questionnaire. The prescreening questionnaire had been completed by 751 (74%) of those who attended. The majority (87%) of respondents reported no pain or mild pain, and the most frequent side-effect (wind) was only experienced more than mildly by 16%. Satisfaction was extremely high, with 98% glad they had the test; 97% would encourage a friend to have it. From prescreening to follow-up there were no changes in anxiety or self-rated health, and the number of colorectal symptoms declined. Satisfaction and changes in wellbeing were not moderated by gender, deprivation, ethnicity or screening outcome.</p> <p>CONCLUSIONS: PROMs indicate high acceptability of FS screening in 58-59 year olds, with no adverse effects on colorectal symptoms, health status or psychological wellbeing.</p&gt