25,841 research outputs found
Modelling and simulation of a biomimetic underwater vehicle
This paper describes work carried out at the
University of Glasgow investigating biomimetic
fish-like propulsion systems for underwater
vehicles. The development of a simple
mathematical model is described for a
biomimetic fish like vehicle which utilizes a
tendon drive propulsion system. This model is
then compared with a model of a vehicle of
similar size but with a propeller for main
propulsion. Simulation results for both models
are shown and compared
The psychological benefits of Special Olympic involvement
Section A is a review of the current literature on sports involvement with respect to people with learning disabilities. It begins by describing the health status of people with learning disabilities and provides a context of sport and wellbeing in the general population. It continues by describing four reviews of the literature exploring people with learning disabilities with respect to sports involvement. This section ends with a description of the Special Olympics research and suggests future research needs in this area.
Section B describes a quantitative cross-sectional study comparing two groups of sports active and non-active people with learning disabilities using several psychological measures.
Objectives. There is evidence that people with learning disabilities have poorer mental and physical wellbeing compared with that of the wider population. The aim of this study was to explore whether a group of people with learning disabilities involved in sport differed in terms of psychological well-being compared with a group not involved in sport.
Design. A cross sectional design was employed comparing two groups, sports active and non-active on the variables: Self-esteem, quality of life, stress levels and social networks.
Methods. Seventy four participants were recruited across South East England. They completed a number of psychological measures.
Results. Analysis revealed that self-esteem, quality of life, social networks and stress were all significantly correlated with Special Olympics involvement. A logistic regression analysis was used to explore whether scores on these variables were able to predict sport membership. Self-esteem was found to be a high predictor of group membership, those in the Special Olympics having higher self-esteem.
Conclusions. The findings provide further evidence of a positive association between sport involvement and increased psychological wellbeing. The implications of these findings for theory and future research into the relationship between sport and psychological wellbeing within the learning disabled population is considered.
Section C is a critical appraisal of the quantitative study that considers four aspects: research skills; amendments to the study if it were replicated; how the study may have influenced clinical practice; and finally, further research and methods relating to this area
Constraints on Neutron Star Crusts From Oscillations in Giant Flares
We show that the fundamental seismic shear mode, observed as a quasi-periodic
oscillation in giant flares emitted by highly-magnetized neutron stars, is
particularly sensitive to the nuclear physics of the crust. The identification
of an oscillation at ~ 30 Hz as the fundamental crustal shear mode requires a
nuclear symmetry energy that depends very weakly on density near saturation. If
the nuclear symmetry energy varies more strongly with density, then lower
frequency oscillations, previously identified as torsional Alfven modes of the
fluid core, could instead be associated with the crust. If this is the case,
then future observations of giant flares should detect oscillations at around
18 Hz. An accurate measurement of the neutron skin thickness of lead will also
constrain the frequencies predicted by the model.Comment: 5 pages, 3 figures; Version to appear in Phys. Rev. Let
Pre-Big Bang Scenario on Self-T-Dual Bouncing Branes
We consider a new class of 5-dimensional dilatonic actions which are
invariant under T-duality transformations along three compact coordinates,
provided that an appropriate potential is chosen. We show that the invariance
remains when we add a boundary term corresponding to a moving 3-brane, and we
study the effects of the T-duality symmetry on the brane cosmological
equations. We find that T-duality transformations in the bulk induce scale
factor duality on the brane, together with a change of sign of the pressure of
the brane cosmological matter. However, in a remarkable analogy with the
Pre-Big Bang scenario, the cosmological equations are unchanged. Finally, we
propose a model where the dual phases are connected through a scattering of the
brane induced by an effective potential. We show how this model can realise a
smooth, non-singular transition between a pre-Big Bang superinflationary
Universe and a post-Big Bang accelerating Universe.Comment: 18 pages, minor typos corrected, Sec. 2 expanded with more details on
the self-T-dual background, Sec.4 and 5 revised accordingly. Version to
appear on JCA
Immediate versus water-storage performance of Class V flowable composite restoratives
Objectives
The aims of this investigation were to clarify the effects of 24 h water-storage and finishing time on mechanical properties and marginal adaptation to a Class V cavity of eight modern flowable resin-composites.
Methods
Eight flowable composites, plus two controls (one microfilled and one hybrid composite), were investigated with specimen sub-groups (n = 10) for each property measured. The principal series of experiments was conducted in model Class V cavities with interfacial polishing either immediately (3 min) after setting or after 24 h water-storage. After the finishing procedure, each tooth was sectioned in a buccolingual direction through the center of the restoration, and the presence or absence of marginal-gaps was measured (and then summed for each cavity) at 14 points (each 0.5 mm apart) along the cavity restoration interface (n = 10 per group; total points measured = 140). The shear bond-strengths to enamel and to dentin, and flexural strengths and moduli data were also measured at 3 min and after 24 h water-storage.
Results
For all flowable composites, polished immediately after setting, 14–30 summed gaps were observed (controls: 64 and 42). For specimens polished after 24 h, a significantly (p < 0.05) reduced number of 8–17 summed gaps occurred for only 3 flowable composites; whereas for 5 flowable composites there were non-significantly-different (p > 0.05) numbers (11–17) of summed gaps (controls: 28 and 22). After 24 h storage, shear bond-strengths to enamel and to dentin, flexural strengths and moduli increased highly significantly (p < 0.001) for all materials, except Silux Plus.
Significance
A post-cure interval of 24 h resulted in enhanced mechanical and adhesive properties of flowable dental composites. In a minority of cases there was also a reduced incidence of marginal-gap formation. However the latter effect may be partly attributed to 24 h delayed polishing, even though such a delay is not usual clinical practice.</p
Type I X-ray bursts and burst oscillations in the accreting millisecond X-ray pulsar IGR J17511-3057
We report the discovery of burst oscillations at the spin frequency in ten
thermonuclear bursts from the accreting millisecond X-ray pulsar (AMXP) IGR
J17511-3057. The burst oscillation properties are, like those from the
persistent AMXPs SAX J1808.4-3658 and XTE J1814-338, anomalous compared to
burst oscillations from intermittent pulsars or non-pulsing LMXBs. Like SAX
J1808.4-3658 they show frequency drifts in the rising phase rather than the
tail. There is also evidence for harmonic content. Where IGR J17511-3057 is
unusual compared to the other two persistent pulsars is that oscillations are
not detected throughout all bursts. As accretion rate drops the bursts get
brighter and their rise/decay time scales become shorter, while the oscillation
amplitude falls below the detection threshold: first in the burst peak and then
also in the rise. None of the bursts from IGR J17511-3057 show evidence for
photospheric radius expansion (which might be expected to suppress oscillation
amplitude) which allow us to set an upper limit to the distance of 6.9 kpc. We
discuss the implications of our results for models of the burst oscillation
mechanism.Comment: 11 pages, 5 figures, MNRAS in pres
Spatial clusters of gonorrhoea in England with particular reference to the outcome of partner notification: 2012 and 2013
Background: This study explored spatial-temporal variation in diagnoses of gonorrhoea to identify and quantify endemic areas and clusters in relation to patient characteristics and outcomes of partner notification (PN) across England, UK. Methods: Endemic areas and clusters were identified using a two-stage analysis with Kulldorff’s scan statistics (SaTScan). Results Of 2,571,838 tests, 53,547 diagnoses were gonorrhoea positive (positivity = 2.08%). The proportion of diagnoses in heterosexual males was 1.5 times that in heterosexual females. Among index cases, men who have sex with men (MSM) were 8 times more likely to be diagnosed with gonorrhoea than heterosexual males (p<0.0001). After controlling for age, gender, ethnicity and deprivation rank, 4 endemic areas were identified including 11,047 diagnoses, 86% of which occurred in London. 33 clusters included 17,629 diagnoses (34% of total diagnoses in 2012 and 2013) and spanned 21 locations, some of which were dominated by heterosexually acquired infection, whilst others were MSM focused. Of the 53,547 diagnoses, 14.5% (7,775) were the result of PN. The proportion of patients who attended services as a result of PN varied from 0% to 61% within different age, gender and sexual orientation cohorts. A third of tests resulting from PN were positive for gonorrhoea. 25% of Local Authorities (n = 81, 95% CI: 20.2, 29.5) had a higher than expected proportion for female PN diagnoses as compared to 16% for males (n = 52, 95% CI: 12.0, 19.9). Conclusions: The English gonorrhoea epidemic is characterised by spatial-temporal variation. PN success varied between endemic areas and clusters. Greater emphasis should be placed on the role of PN in the control of gonorrhoea to reduce the risk of onward transmission, re-infection, and complications of infection
Space shuttle: Aerodynamic characteristics of a composite booster/040A orbiter launch configuration with fin and booster body configuration effect contribution
An investigation was made of the fin configuration and booster body configuration effects on a composite booster/040A orbiter launch configuration. Aerodynamic performance and stability characteristics in pitch and yaw were obtained. Configurations tested included two stepped cylindrical bodies of different lengths with a conical nose, four fin shapes of various sizes and aspect ratios mounted in different positions around the base of the bodies, two base flare angles and three 040A orbiter configurations. The orbiter variations included a tailless configuration and two tail sizes. A tailless booster launch configuration with deflected petals (expanded flare sectors) was also tested. The model scale was 0.003366. Data were converted to coefficient form in near real time, punched on cards, and tabulated. The cards used in conjunction with a Benson-Lehner plotter were used to provide plotted data. At the end of the test, tabulated input forms were completed for the SADSAC computer program to aid in publishing the final test data report
Magnetar giant flare high-energy emission
High energy ( keV) emission has been detected persisting for several
tens of seconds after the initial spike of magnetar giant flares. It has been
conjectured that this emission might arise via inverse Compton scattering in a
highly extended corona generated by super-Eddington outflows high up in the
magnetosphere. In this paper we undertake a detailed examination of this model.
We investigate the properties of the required scatterers, and whether the
mechanism is consistent with the degree of pulsed emission observed in the tail
of the giant flare. We conclude that the mechanism is consistent with current
data, although the origin of the scattering population remains an open
question. We propose an alternative picture in which the emission is closer to
that star and is dominated by synchrotron radiation. The observations
of the December 2004 flare modestly favor this latter picture. We assess the
prospects for the Fermi Gamma-Ray Space Telescope to detect and characterize a
similar high energy component in a future giant flare. Such a detection should
help to resolve some of the outstanding issues.Comment: 20 pages, 14 figure
- …