17,892 research outputs found

    Testing conformal mapping with kitchen aluminum foil

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    We report an experimental verification of conformal mapping with kitchen aluminum foil. This experiment can be reproduced in any laboratory by undergraduate students and it is therefore an ideal experiment to introduce the concept of conformal mapping. The original problem was the distribution of the electric potential in a very long plate. The correct theoretical prediction was recently derived by A. Czarnecki (Can. J. Phys. 92, 1297 (2014))

    Opthalmic impairment at 7 years of age in children born very preterm

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    Aims: To determine the prevalence of ophthalmic impairments in very preterm compared with term infants, the relation between impairments and cerebral ultrasound appearances and retinopathy, and the correlation with visual perception and motor and cognitive measures. Subjects: 279 children at 7 years of age born before 32 weeks gestation within Liverpool during 1991–92 and attending mainstream schools, and 210 term controls. Methods: Visual acuity was assessed by Snellen chart, and strabismus by the cover test. Stereopsis was determined using the TNO random dot test, and contrast sensitivity using the Cambridge low contrast gratings. Visual and motor abilities were assessed using the Developmental test of motor integration (VMI) and the Movement ABC. Intelligence was measured with the Wechsler intelligence scale for children UK. Perinatal cranial ultrasound and retinopathy data were extracted from clinical records. Results: Children born preterm were significantly more likely to wear glasses, to have poor visual acuity, reduced stereopsis, and strabismus than term controls, but they showed no significant decrease in contrast sensitivity. Ophthalmic impairments were significantly related to poorer scores on the VMI, Movement ABC, and Wechsler IQ tests, but were not significantly related to neonatal cranial ultrasound appearances. Stage 3 retinopathy was related to poorer subsequent acuity. Conclusions: Children born very preterm and without major neurodevelopmental sequelae have an increased prevalence of ophthalmic impairments at primary school age which are associated with visual perceptional, motor, and cognitive defects. The cause may be a generalised abnormality of cortical development rather than perinatally acquired focal lesions of the brain

    A cross sectional study investigating the association between exposure to food outlets and childhood obesity in Leeds, UK.

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    Background: Current UK policy in relation to the influence of the ‘food environment’ on childhood obesity appears to be driven largely on assumptions or speculations because empirical evidence is lacking and findings from studies are inconsistent. The aim of this study was to investigate the number of food outlets and the proximity of food outlets in the same sample of children, without solely focusing on fast food. Methods: Cross sectional study over 3 years (n = 13,291 data aggregated). Body mass index (BMI) was calculated for each participant, overweight and obesity were defined as having a BMI >85th (sBMI 1.04) and 95th (sBMI 1.64) percentiles respectively (UK90 growth charts). Home and school neighbourhoods were defined as circular buffers with a 2 km Euclidean radius, centred on these locations. Commuting routes were calculated using the shortest straight line distance, with a 2 km buffer to capture varying routes. Data on food outlet locations was sourced from Leeds City Council covering the study area and mapped against postcode. Food outlets were categorised into three groups, supermarkets, takeaway and retail. Proximity to the nearest food outlet in the home and school environmental domain was also investigated. Age, gender, ethnicity and deprivation (IDACI) were included as covariates in all models. Results: There is no evidence of an association between the number of food outlets and childhood obesity in any of these environments; Home Q4 vs. Q1 OR = 1.11 (95% CI = 0.95-1.30); School Q4 vs. Q1 OR = 1.00 (95% CI 0.87 – 1.16); commute Q4 vs. Q1 OR = 0.1.00 (95% CI 0.83 – 1.20). Similarly there is no evidence of an association between the proximity to the nearest food outlet and childhood obesity in the home (OR = 0.77 [95% CI = 0.61 – 0.98]) or the school (OR = 1.01 [95% CI 0.84 – 1.23]) environment. Conclusions: This study provides little support for the notion that exposure to food outlets in the home, school and commuting neighbourhoods increase the risk of obesity in children. It seems that the evidence is not well placed to support Governmental interventions/recommendations currently being proposed and that policy makers should approach policies designed to limit food outlets with caution

    On classification of Poisson vertex algebras

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    We describe a conjectural classification of Poisson vertex algebras of CFT type and of Poisson vertex algebras in one differential variable (= scalar Hamiltonian operators)

    Characterization of the Noise in Secondary Ion Mass Spectrometry Depth Profiles

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    The noise in the depth profiles of secondary ion mass spectrometry (SIMS) is studied using different samples under various experimental conditions. Despite the noise contributions from various parts of the dynamic SIMS process, its overall character agrees very well with the Poissonian rather than the Gaussian distribution in all circumstances. The Poissonian relation between the measured mean-square error (MSE) and mean can be used to describe our data in the range of four orders. The departure from this relation at high counts is analyzed and found to be due to the saturation of the channeltron used. Once saturated, the detector was found to exhibit hysteresis between rising and falling input flux and output counts.Comment: 14 pages, 4 postscript figures, to appear on J. Appl. Phy

    Polar orbit electrostatic charging of objects in shuttle wake

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    A survey of DMSP data has uncovered several cases where precipitating auroral electron fluxes are both sufficiently intense and energetic to charge spacecraft materials such as teflon to very large potentials in the absence of ambient ion currents. Analytical bounds are provided which show that these measured environments can cause surface potentials in excess of several hundred volts to develop on objects in the orbiter wake for particular vehicle orientations

    Spacecraft-plasma interaction codes: NASCAP/GEO, NASCAP/LEO, POLAR, DynaPAC, and EPSAT

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    Development of a computer code to simulate interactions between the surfaces of a geometrically complex spacecraft and the space plasma environment involves: (1) defining the relevant physical phenomena and formulating them in appropriate levels of approximation; (2) defining a representation for the 3-D space external to the spacecraft and a means for defining the spacecraft surface geometry and embedding it in the surrounding space; (3) packaging the code so that it is easy and practical to use, interpret, and present the results; and (4) validating the code by continual comparison with theoretical models, ground test data, and spaceflight experiments. The physical content, geometrical capabilities, and application of five S-CUBED developed spacecraft plasma interaction codes are discussed. The NASA Charging Analyzer Program/geosynchronous earth orbit (NASCAP/GEO) is used to illustrate the role of electrostatic barrier formation in daylight spacecraft charging. NASCAP/low Earth orbit (LEO) applications to the CHARGE-2 and Space Power Experiment Aboard Rockets (SPEAR)-1 rocket payloads are shown. DynaPAC application to the SPEAR-2 rocket payloads is described. Environment Power System Analysis Tool (EPSAT) is illustrated by application to Tethered Satellite System 1 (TSS-1), SPEAR-3, and Sundance. A detailed description and application of the Potentials of Large Objects in the Auroral Region (POLAR) Code are presented

    Developing a robust tool: advancing the multiple mini interview in pre-registration student midwife selection in a UK setting

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    Background: Published research has shown the multiple mini interview (MMI) to be a reliable assessment instrument in medical and nursing student selection internationally. Objectives: To develop, pilot and examine the reliability of MMIs in pre-registration student midwife selection in one Higher Education Institution a UK setting. Design and setting: BSc (Hons) Midwifery Studies students at a Higher Education Institution in the UK volunteered to participate in ‘mock’ MMI circuits during the first week of their programme. DeVellis’s framework for questionnaire development underpinned the generation of interview scenarios. Participants’ responses to scenario questions were rated on a 7 point scale. Internal consistency was calculated for each station. Results: An eight station model was piloted. Communication skills were assessed at each station as a generic attribute. Station specific attributes assessed included compassion and empathy, respect for difference and diversity, honesty and integrity, intellectual curiosity and reflective nature, advocacy, respect for privacy and dignity, team working and initiative, the role of the midwife and motivation to become a midwife. Cronbach’s alpha scores for each station ranged from 0.91 – 0.97. Conclusion: The systematic development of the MMI model and scenarios resulted in ‘excellent’ reliability across all stations. These findings endorse the MMI technique as a reliable alternative to the personal interview in informing final decisions in pre-registration student midwife selection

    Value-based recruitment in midwifery: do the values align with what women say is important to them?

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    Aim: To discuss theoretical conceptualisation and definition of values and values-based recruitment in the context of women’s views about what they would like from their midwife. Background: Values-based recruitment received headline status in the UK government’s response to pervasive deficiencies in compassionate care identified in the health service. Core values which aim to inform service user’s experience are defined in the National Health Service Constitution but clarity about whether these encompass all that women say is important to them is needed. Design: Discussion paper Data Sources: A literature search included published papers written in English relating to values, VBR and women’s views of a ‘good’ midwife with no date limiters. Discussion: Definitions of values and values-based recruitment are examined. Congruence is explored between what women say is important to them and key government and professional regulatory documentation. The importance of a ‘sustainable emotional’ dimension in the midwife-mother relationship is suggested. Conclusion: Inconsistencies are identified between women’s views, government, professional documentation and what women say they want. An omission of any reference to emotions or emotionality in values-based recruitment policy, professional recruitment and selection guidance documentation is identified. Implications: A review of key professional documentation, in relation to selection for ‘values’, is proposed. We argue for clarity and revision so that values embedded in values-based recruitment are consistent with health service users’ views. An enhancement of the ‘values’ in the values-based recruitment framework is recommended to include the emotionality that women state is a fundamental part of their relationship with their midwife
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