837 research outputs found

    Toward an Improved Analytical Description of Lagrangian Bias

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    We carry out a detailed numerical investigation of the spatial correlation function of the initial positions of cosmological dark matter halos. In this Lagrangian coordinate system, which is especially useful for analytic studies of cosmological feedback, we are able to construct cross-correlation functions of objects with varying masses and formation redshifts and compare them with a variety of analytical approaches. For the case in which both formation redshifts are equal, we find good agreement between our numerical results and the bivariate model of Scannapieco & Barkana (2002; SB02) at all masses, redshifts, and separations, while the model of Porciani et al. (1998) does well for all parameters except for objects with different masses at small separations. We find that the standard mapping between Lagrangian and Eulerian bias performs well for rare objects at all separations, but fails if the objects are highly-nonlinear (low-sigma) peaks. In the Lagrangian case in which the formation redshifts differ, the SB02 model does well for all separations and combinations of masses, apart from a discrepancy at small separations in situations in which the smaller object is formed earlier and the difference between redshifts or masses is large. As this same limitation arises in the standard approach to the single-point progenitor distribution developed by Lacey & Cole (1993), we conclude that a more complete understanding of the progenitor distribution is the most important outstanding issue in the analytic modeling of Lagrangian bias.Comment: 22 pages, 8 figures, ApJ, in pres

    The management of public expenditures : an evolving Bank approach

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    World Bank lending and advice to support institutional and policy reform of public expenditure management is of recent and limited, but rapidly expanding scope. The paper begins with a brief overview of the Bank's recent work on public expenditures. The analysis indicates the lack of a consistent approach to the institutional and procedural aspects of public expenditure management. The paper goes on to discuss the Bank's changing approach towards public expenditures, starting with concepts of economic planning and public investment programs. It describes how the Bank's concerns have pushed beyond the confines of investment programming into the wider area of the planning and management of public expenditure. The paper then discusses some of the difficulties and issues involved in this process. The paper attempts to offer some tentative operational guidelines based partly on recent experience, and partly on"state of the art"in some industrialized and developing countries. These are summarized in annexes II and III, while annex IV distils some of the main sequential features of the budgetary decision-making process.National Governance,Poverty Assessment,Public Sector Economics&Finance,ICT Policy and Strategies,Business in Development

    Right Reason in Edmund Spenser\u27s \u27Faerie Queene.\u27.

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    High Sensitivity DNA Detection Using Gold Nanoparticle Functionalised Polyaniline Nanofibres

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    Polyaniline (PANI) nanofibres (PANI-NF) have been modified with chemically grown gold nanoparticles to give a nanocomposite material (PANI-NF–AuNP) and deposited on gold electrodes. Single stranded capture DNA was then bound to the gold nanoparticles and the underlying gold electrode and allowed to hybridise with a complementary target strand that is uniquely associated with the pathogen, Staphylococcus aureus (S. aureus), that causes mastitis. Significantly, cyclic voltammetry demonstrates that deposition of the gold nanoparticles increases the area available for DNA immobilisation by a factor of approximately 4. EPR reveals that the addition of the Au nanoparticles efficiently decreases the interactions between adjacent PANI chains and/or motional broadening. Finally, a second horseradish peroxidase (HRP) labelled DNA strand hybridises with the target allowing the concentration of the target DNA to be detected by monitoring the reduction of a hydroquinone mediator in solution. The sensors have a wide dynamic range, excellent ability to discriminate DNA mismatches and a high sensitivity. Semi-log plots of the pathogen DNA concentration vs. faradaic current were linear from 150 × 10−12 to 1 × 10−6 mol L−1 and pM concentrations could be detected without the need for molecular, e.g., PCR or NASBA, amplification

    Road safety education for older drivers : evaluation of a classroom-based training initiative

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    Around the world, a growing proportion of drivers are aged 70 or over. Although accident rates for older drivers are lower than for young or novice drivers, increased frailty and slowed reactions mean that older drivers are at higher risk of death or serious injury when involved in a road collision. The objectives of this study were to: (a) identify driving knowledge and self-regulatory strategies among a group of older drivers with a view to planning future on-road training; (b) measure driver self-assessments of ability and confidence before and after classroom training delivered by driving instructors; (c) evaluate the utility and acceptability of training courses for older drivers using questionnaires and focus groups; d) examine the characteristics of course participants. 142 drivers aged ≥75 completed a two-hour classroom-based driving course and took part in the evaluation: 94 aged 75–79, 48 aged ≥80, 68% male. Main reasons for taking part were to update knowledge, improve driving and check they were safe to drive. Results showed that females were more likely than males to avoid driving in difficult conditions (at night, in bad weather, unfamiliar roads). More drivers aged 75–79 said they did not restrict their driving (52, 57%) compared to drivers aged ≥80 (19, 43%). Pre-course, males rated their driving confidence and ability significantly higher than females. Post-course, self-ratings of confidence and ability were unchanged for 76 (60%) drivers. However, two-thirds reported improved knowledge and 80% said they would change their driving behaviour as a result of the course. Focus group results suggest that competent drivers are more likely to attend educational courses than unsafe drivers. This study provides preliminary evidence that classroom-based training can initiate behaviour change among older drivers. Future research will examine the effectiveness of on-road training in this age group

    Perceptual learning, talker specificity, and sound change

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    Perceptual learning is when listeners hear novel speech input and shift their subsequent perceptual behavior. In this paper we consider the relationship between sound change and perceptual learning. We spell out the connections we see between perceptual learning and different approaches to sound change and explain how a deeper empirical understanding of the properties of perceptual learning might benefit sound change models. We propose that questions about when listeners generalize their perceptual learning to new talkers might be of of particular interest to theories of sound change. We review the relevant literature, noting that studies of perceptual learning generalization across talkers of the same gender are lacking. Finally, we present new experimental data aimed at filling that gap by comparing cross-talker generalization of fricative boundary perceptual learning in same-gender and different-gender pairs. We find that listeners are much more likely to generalize what they have learned across same-gender pairs, even when the different-gender pairs have more similar fricatives. We discuss implications for sound change
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