117,465 research outputs found

    VLA observations of a sample of galaxies with high far-infrared luminosities

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    Preliminary results are presented from a radio survey of galaxies detected by the IRAS minisurvey. It was found that the main difference between galaxies selected in the far infrared and those selected in the optical is that the former have higher radio luminosities and that the radio emission is more centrally concentrated. There is some evidence that the strong central radio sources in the galaxies selected in the infrared are due to star formation, the star formation rate divided by the volume in which the star formation is occuring is 100 to 1000 times greater in the galaxies selected in the infrared than in the disks of normal galaxies

    On direction of spontaneous magnetization in a "cubic" ferromagnet

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    The magnetic properties of anisotropic films have been studied using 3D-neutron polarization analysis. The experimental facts refer to essential distinction of the sample states, magnetized in opposite directions. For an explanation of asymmetrical effects the model is offered, in which the fundamental theoretical principles of structural phase transitions are used.Comment: 4 pages LaTeX (phbauth) and 4 figures (epsfig

    Is resilience a normative concept?

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    In this paper, we engage with the question of the normative content of the resilience concept. The issues are approached in two consecutive steps. First, we proceed from a narrow construal of the resilience concept – as the ability of a system to absorb a disturbance – and show that under an analysis of normative concepts as evaluative concepts resilience comes out as descriptive. In the second part of the paper, we argue that (1) for systems of interest (primarily social systems or system with a social component) we seem to have options with respect to how they are described and (2) that this matters for what is to be taken as a sign of resilience as opposed to a sign of the lack of resilience for such systems. We discuss the implications of this for how the concept should be applied in practice and suggest that users of the resilience concept face a choice between versions of the concept that are either ontologically or normatively charged

    Ultracold atoms in an optical lattice with dynamically variable periodicity

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    The use of a dynamic "accordion" lattice with ultracold atoms is demonstrated. Ultracold atoms of 87^{87}Rb are trapped in a two-dimensional optical lattice, and the spacing of the lattice is then increased in both directions from 2.2 to 5.5 microns. Atoms remain bound for expansion times as short as a few milliseconds, and the experimentally measured minimum ramp time is found to agree well with numerical calculations. This technique allows an experiment such as quantum simulations to be performed with a lattice spacing smaller than the resolution limit of the imaging system, while allowing imaging of the atoms at individual lattice sites by subsequent expansion of the optical lattice.Comment: 4 pages, 3 figures. Minor changes made and references update

    Observation of vortex nucleation in a rotating two-dimensional lattice of Bose-Einstein condensates

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    We report the observation of vortex nucleation in a rotating optical lattice. A 87Rb Bose-Einstein condensate was loaded into a static two-dimensional lattice and the rotation frequency of the lattice was then increased from zero. We studied how vortex nucleation depended on optical lattice depth and rotation frequency. For deep lattices above the chemical potential of the condensate we observed a linear dependence of the number of vortices created with the rotation frequency,even below the thermodynamic critical frequency required for vortex nucleation. At these lattice depths the system formed an array of Josephson-coupled condensates. The effective magnetic field produced by rotation introduced characteristic relative phases between neighbouring condensates, such that vortices were observed upon ramping down the lattice depth and recombining the condensates.Comment: 4 pages, 4 figures, accepted for publication in Phys. Rev. Let

    Guidelines for the management of the foot health problems associated with rheumatoid arthritis

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    Background. Rheumatoid arthritis (RA) as a chronic systemic disease, commonly affects the feet, impacting negatively on patients' quality of life. Specialist podiatrists have a prime role to play in the assessment and management of foot and ankle problems within this patient group. However, it has been identified that in many areas there is no specialist podiatry service, with many patients being managed by non‐specialist podiatrists. Therefore, the North West Clinical Effectiveness Group for the Foot in Rheumatic Diseases (NWCEG) identified the need to develop ‘practitioner facing’ guidelines for the management of specific foot health problems associated with RA. Methods. Members of a guideline development group from the NWCEG each reviewed the evidence for specific aspects of the assessment and management of foot problems. Where evidence was lacking, ‘expert opinion’ was obtained from the members of the NWCEG and added as a consensus on current and best practice. An iterative approach was employed, with the results being reviewed and revised by all members of the group and external reviewers before the final guideline document was produced. Results. The management of specific foot problems (callus, nail pathology, ulceration) and the use of specific interventions (foot orthoses, footwear, patient education, steroid injection therapy) are detailed and standards in relation to each are provided. A diagrammatic screening pathway is presented, with the aim of guiding nonspecialist podiatrists through the complexity of assessing and managing those patients with problems requiring input from a specialist podiatrist and other members of the rheumatology multidisciplinary team. Conclusion. This pragmatic approach ensured that the guidelines were relevant and applicable to current practice as ‘best practice’, based on the available evidence from the literature and consensus expert opinion. These guidelines provide both specialist and non‐specialist podiatrists with the essential and ‘gold standard’ aspects of managing people with RA‐related foot problems

    Molecular dynamics simulations of oxide memristors: crystal field effects

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    We present molecular-dynamic simulations of memory resistors (memristors) including the crystal field effects on mobile ionic species such as oxygen vacancies appearing during operation of the device. Vacancy distributions show different patterns depending on the ratio of a spatial period of the crystal field to a characteristic radius of the vacancy-vacancy interaction. There are signatures of the orientational order and of spatial voids in the vacancy distributions for some crystal field potentials. The crystal field stabilizes the patterns after they are formed, resulting in a non-volatile switching of the simulated devices.Comment: 9 pages, 3 figure

    Molecules, ices and astronomy

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    Molecules in interstellar gas and in interstellar ices play a fundamental role in astronomy. However, the formation of the simplest molecule, molecular hydrogen, is still not fully understood. Similarly, although interstellar ice analogues have received much attention in the laboratory, the evolution of ices in the interstellar medium still requires further study. At UCL we have developed two separate experiments to address these issues and explore the following questions: How is H formed on dust-grain surfaces? What is the budget between internal, kinetic and surface energies in the formation process? What are the astronomical consequences of these results? For ices, we ask: How do molecules desorb from pure and from mixed ices in regions warmed by newly formed stars? What can molecules released from ices tell us about the star-formation process? We put our results in the context of other laboratory work and we describe their application to current problems in astronomy

    Do early-life exposures explain why more advantaged children get eczema? Findings from the U.K. Millennium Cohort Study

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    Background: Atopic dermatitis (eczema) in childhood is socially patterned, with higher incidence in more advantaged populations. However, it is unclear what factors explain the social differences. Objectives: To identify early-life risk factors for eczema, and to explore how early-life risk factors explain any differences in eczema. Methods: We estimated odds ratios (ORs) for ever having had eczema by age 5 years in 14 499 children from the U.K. Millennium Cohort Study (MCS), with a focus on maternal, antenatal and early-life risk factors and socioeconomic circumstances (SECs). Risk factors were explored to assess whether they attenuated associations between SECs and eczema. Results: Overall 35·1% of children had ever had eczema by age 5 years. Children of mothers with degree-level qualifications vs. no educational qualifications were more likely to have eczema (OR 1·52, 95% confidence interval 1·31–1·76), and there was a gradient across the socioeconomic spectrum. Maternal atopy, breastfeeding (1–6 weeks and ≥ 6 months), introduction of solids under 4 months or cow's milk under 9 months, antibiotic exposure in the first year of life and grime exposure were associated with an increased odds of having eczema. Female sex, Pakistani and Bangladeshi ethnicity, smoking during pregnancy, exposure to environmental tobacco smoke and having more siblings were associated with reduced odds for eczema. Controlling for maternal, antenatal and early-life characteristics (particularly maternal smoking during pregnancy, breastfeeding and number of siblings) reduced the OR for eczema to 1·26 (95% confidence interval 1·03–1·50) in the group with the highest educational qualifications compared with the least. Conclusions: In a representative U.K. child cohort, eczema was more common in more advantaged children. This was explained partially by early-life factors including not smoking during pregnancy, breastfeeding and having fewer siblings
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