6,355 research outputs found
Submanifolds in five-dimensional pseudo-Euclidean spaces and four-dimensional FRW universes
Equations for submanifolds, which correspond to embeddings of the
four-dimensional FRW universes in five-dimensional pseudo-Euclidean spaces, are
presented in convenient form in general case. Several specific examples are
considered.Comment: 7 pages, LaTeX, the mathematical part of this paper is based on the
withdrawn preprint arXiv:1012.0320 [gr-qc
A national survey of services for the prevention and management of falls in the UK
Background: The National Health Service (NHS) was tasked in 2001 with developing service provision to prevent falls in older people. We carried out a national survey to provide a description of health and social care funded UK fallers services, and to benchmark progress against current
practice guidelines.
Methods: Cascade approach to sampling, followed by telephone survey with senior member of the fall service. Characteristics of the service were assessed using an internationally agreed taxonomy. Reported service provision was compared against benchmarks set by the National
Institute for Health and Clinical Excellence (NICE).
Results: We identified 303 clinics across the UK. 231 (76%) were willing to participate. The majority of services were based in acute or community hospitals, with only a few in primary care or emergency departments. Access to services was, in the majority of cases, by health professional
referral. Most services undertook a multi-factorial assessment. The content and quality of these assessments varied substantially. Services varied extensively in the way that interventions were delivered, and particular concern is raised about interventions for vision, home hazard modification, medication review and bone health.
Conclusion: The most common type of service provision was a multi-factorial assessment and intervention. There were a wide range of service models, but for a substantial number of services, delivery appears to fall below recommended NICE guidance
Planar Disjoint-Paths Completion
We introduce Planar Disjoint Paths Completion, a completion counterpart of the Disjoint Paths problem, and study its parameterized complexity. The problem can be stated as follows: given a, not necessarily connected, plane graph G, k pairs of terminals, and a face F of G, find a minimum-size set of edges, if one exists, to be added inside F so that the embedding remains planar and the pairs become connected by k disjoint paths in the augmented network. Our results are twofold: first, we give an upper bound on the number of necessary additional edges when a solution exists. This bound is a function of k, independent of the size of G. Second, we show that the problem is fixed-parameter tractable, in particular, it can be solved in time f(k) ¡ n2
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Nitrogen stable isotopic composition of leaves and soil: Tropical versus temperate forests
Several lines of evidence suggest that nitrogen in most tropical forests is relatively more available than N in most temperate forests, and even that it may function as an excess nutrient in many tropical forests. If this is correct, tropical forests should have more open N cycles than temperate forests, with both inputs and outputs of N large relative to N cycling within systems. Consequent differences in both the magnitude and the pathways of N loss imply that tropical forests should in general he more 15N enriched than are most temperate forests. In order to test this hypothesis, we compared the nitrogen stable isotopic composition of tree leaves and soils from a variety of tropical and temperate forests. Foliar δ15N values from tropical forests averaged 6.5Ⱐhigher than from temperate forests. Within the tropics, ecosystems with relatively low N availability (montane forests, forests on sandy soils) were significantly more depleted in 15N than other tropical forests. The average δ15N values for tropical forest soils, either for surface or for depth samples, were almost 8Ⱐhigher than temperate forest soils. These results provide another line of evidence that N is relatively abundant in many tropical forest ecosystems
Dissecting the Red Sequence--II. Star Formation Histories of Early-Type Galaxies Throughout the Fundamental Plane
This analysis uses spectra of ~16,000 nearby SDSS quiescent galaxies to track
variations in galaxy star formation histories along and perpendicular to the
Fundamental Plane (FP). We sort galaxies by their FP properties (sigma, R_e,
and I_e) and construct high S/N mean galaxy spectra that span the breadth and
thickness of the FP. From these spectra, we determine mean luminosity-weighted
ages, [Fe/H], [Mg/H], and [Mg/Fe] based on single stellar population models
using the method described in Graves & Schiavon (2008). In agreement with
previous work, the star formation histories of early-type galaxies are found to
form a two-parameter family. The major trend is that mean age, [Fe/H], [Mg/H],
and [Mg/Fe] all increase with sigma. However, no stellar population property
shows any dependence on R_e at fixed sigma, suggesting that sigma and not
dynamical mass (M_dyn ~ sigma^2 R_e) is the better predictor of past star
formation history. In addition to the main trend with sigma, galaxies also show
a range of population properties at fixed sigma that are strongly correlated
with surface brightness residuals from the FP, such that higher surface
brightness galaxies have younger mean ages, higher [Fe/H], higher [Mg/H], and
lower [Mg/Fe] than lower-surface brightness galaxies. These latter trends are a
major new constraint on star-formation histories.Comment: 23 pages, 14 figures. Accepted to Ap
Terahertz emission mechanism and laser excitation position dependence of nano-grating electrode photomixers
The emission mechanism of continuous wave (CW) terahertz (THz) photomixers that make use of nanostructured gratings (NSGs) is studied. Two different photomixer designs, based on a single-sided NSG and a double-sided NSG, embedded in the same antenna design and fabricated on an Fe doped InGaAsP substrate, are characterized with âź1550 nm excitation. They are shown to exhibit similar performance in terms of spectral bandwidth and emitted power. The emission is mapped in terms of the laser excitation position, from which the emission mechanism is assigned to an enhanced optical electric field at the tips of the NSGs
Terahertz generation mechanism in nano-grating electrode photomixers on Fe-doped InGaAsP
We report the generation mechanism associated with nano-grating electrode photomixers fabricated on Fe-doped InGaAsP substrates. Two different emitter designs incorporating nano-gratings coupled to the same broadband antenna were characterized in a continuous-wave terahertz (THz) frequency system employing telecommunications wavelength lasers for generation and coherent detection. The current-voltage characteristics and THz emission bandwidth of the emitters is compared for different bias polarities and optical polarisations. The THz output from the emitters is also mapped as a function of the position of the laser excitation spot for both continuous-wave and pulsed excitation. This mapping, together with full-wave simulations of the structures, confirms the generation mechanism to be due to an enhanced optical electric field at the grating tips resulting in increased optical absorption, coinciding with a concentration of the electrostatic field
Wake Up and Smell the Coffee: Yet Another No Go for Cardiac Patients?: Editorial to âCaffeinated Coffee Blunts the Myocardial Protective Effects of Statins Against Ischemiaâreperfusion Injury in the Ratâ by Ye et al.
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Reduction of low- and high-grade cervical abnormalities associated with high uptake of the HPV bivalent vaccine in Scotland
In Scotland, a national HPV immunisation programme began in 2008 for 12-13 year olds, with a catch-up campaign from 2008-2011 for those under the age of 18. To monitor the impact of HPV immunisation on cervical disease at the population level, a programme of national surveillance was established. We analysed colposcopy data from a cohort of women born between 1988-1992 who entered the Scottish Cervical Screening Programme (SCSP) and were aged 20-21 in 2008-2012. By linking datasets from the SCSP and colposcopy services, we observed a significant reduction in diagnoses of cervical intraepithelial neoplasia 1 (CIN 1) (RR 0.71, 95% CI 0.58 to 0.87, p=0.0008), CIN 2 (RR 0.5, 95% CI 0.4, 0.63, p<0.0001) and CIN 3 (RR 0.45, 95% CI 0.35 to 0.58, p< 0.0001) for women who received 3 doses of vaccine compared with unvaccinated women. To our knowledge, this is one of the first studies to show a reduction of low and high grade cervical intraepithelial neoplasia associated with high uptake of the HPV bivalent vaccine at the population level. These data are very encouraging for countries that have achieved high HPV vaccine uptake
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