3,309 research outputs found
Further evidence for the planet around 51 Pegasi
The discovery of the planet around the solar-type star 51 Pegasi marked a
watershed in the search for extrasolar planets. Since then seven other
solar-type stars have been discovered, of which several have surprisingly short
orbital periods, like the planet around 51 Peg. These planets were detected
using the indirect technique of measuring variations in the Doppler shifts of
lines in the spectra of the primary stars. But it is possible that oscillations
of the stars themselves (or other effects) could mimic the signature of the
planets, particularly around the short-period planets. The apparent lack of
spectral and brightness variations, however, led to widespread acceptance that
there is a planet around 51 Peg. This conclusion was challenged by the
observation of systematic variations in the line profile shapes of 51 Peg,
which suggested stellar oscillations. If these observations are correct, then
there is no need to invoke a planet around 51 Peg to explain the data. Here we
report observations of 51 Peg at a much higher spectral resolution than those
in ref.9, in which we find no evidence for systematic changes in the line
shapes. The data are most consistent with a planetary companion to 51 Peg.Comment: LaTeX, 6 pages, 2 figures. To appear in 8 January 1998 issue of
Natur
A prospective study of stroke sub-type from within an incident population in Tanzania
Objectives. We aimed to establish the pathological types of stroke in two incident populations in Tanzania, one rural and one urban, and to examine the clinical utility of the Siriraj and Allen scores in identifying stroke sub-types. Design. This prospective community-based study identified cases as part of a stroke incidence study. Each patient underwent a full assessment including recording demographic information, taking a medical and drug history, and physical examination. A computed tomography (CT) head scan was used to classify strokes as resulting from a cerebral haemorrhage or ischaemia. The results were compared with the Siriraj and Allen scores, obtained from clinical findings. Results. One hundred and thirty-two incident stroke cases were identified in the rural Hai demographic surveillance site (DSS) and 69 in the urban Dar-es-Salaam DSS; 63 patients with stroke due to ischaemia or cerebral haemorrhage from Hai and 17 from Dar-es-Salaam had a CT scan within 15 days of the stroke. Stroke was identified as due to ischaemia in 52 cases (82.5%) and to cerebral haemorrhage in 11 (17.5%) in Hai, and as due to ischaemia in 14 cases (82.4%) and to cerebral haemorrhage in 3 (17.6%) in Dar-es-Salaam. In both sites Siriraj and Allen scores were found to be of little value in predicting stroke sub-type. Conclusions. The ratio of ischaemic to haemorrhagic stroke is much higher in our cohort than previously reported in sub-Saharan Africa, and is closer to that in high-income countries
Correlates of short- and long-term case fatality within an incident stroke population in Tanzania
Background. This study aimed to identify correlates of case fatality within an incident stroke population in rural Tanzania.Methods. Stroke patients, identified by the Tanzanian Stroke Incidence Project, underwent a full examination and assessment around the time of incident stroke. Records were made of demographic data, blood pressure, pulse rate and rhythm, physical function (Barthel index), neurological status (communication, swallowing, vision, muscle activity, sensation), echocardiogram, chest X-ray and computed tomography (CT) head scan. Cases were followed up over the next 3 - 6 years.Results. In 130 incident cases included in this study, speech, language and swallowing problems, reduced muscle power, and reduced physical function were all significantly correlated with case fatality at 28 days and 3 years. Age was significantly correlated with case fatality at 3 years, but not at 28 days post-stroke. Smoking history was the only significant correlate of case fatality at 28 days that pre-dated the incident stroke. All other significant correlates were measures of neurological recovery from stroke.Conclusions. This is the first published study of the correlates of post-stroke case fatality in sub-Saharan Africa (SSA) from an incidentstroke population. Case fatality was correlated with the various motor impairments resulting from the incident stroke. Improving poststrokecare may help to reduce stroke case fatality in SSA
Visualising spatial and social media
In this chapter, we begin by surveying the development of computer graphics as it has influenced the development of the spatial representation of social and economic data, charting the history of computer cartography and geographic information systems (GIS) which have broadened into a wide array of forms for scientific visualisation. With the advent of the World Wide Web and the widespread adoption of graphical user interfaces (GUIs) to most kinds of computer device, visualisation has become central to most sciences and to the dissemination of many kinds of data and information. We divide our treatment of this domain according to three themes. First we examine how the 2-‐dimensional map has become key to many kinds of spatial representation, showing how this software has moved from the desktop to the web as well as how 2-‐d has moved to 3-‐d in terms of the visualisation of maps. Second, we explore how social data is being augmented by space-‐time series generated in real time and show how such real-‐time streaming of data presents problems and opportunities in which visualisation is key. We illustrate these new data for basic feeds from cities but then move to examine data from transit systems, social media, and data that is pulled from the crowd – crowdsourcing. Finally we note the development of visual analytics showing how 2d and 3d spatial representations are essential to interpreting the outputs and the workings of more complex models and simulations. We conclude with the notion that much of what we develop in this chapter for the space-time domain is generic to the future representation of all kinds of social data
Are there gender differences in the geography of alcohol-related mortality in Scotland? An ecological study
<b>Background</b>
There is growing concern about alcohol-related harm, particularly within Scotland which has some of the highest rates of alcohol-related death in western Europe. There are large gender differences in alcohol-related mortality rates in Scotland and in other countries, but the reasons for these differences are not clearly understood. In this paper, we aimed to address calls in the literature for further research on gender differences in the causes, contexts and consequences of alcohol-related harm. Our primary research question was whether the kind of social environment which tends to produce higher or lower rates of alcohol-related mortality is the same for both men and women across Scotland.
<b>Methods</b>
Cross-sectional, ecological design. A comparison was made between spatial variation in men's and women's age-standardised alcohol-related mortality rates in Scotland using maps, Moran's Index, linear regression and spatial analyses of residuals. Directly standardised mortality rates were derived from individual level records of death registration, 2000–2005 (n = 8685).
<b>Results</b>
As expected, men's alcohol-related mortality rate substantially exceeded women's and there was substantial spatial variation in these rates for both men and women within Scotland. However, there was little spatial variation in the relationship between men's and women's alcohol-mortality rates (r2 = 0.73); areas with relatively high rates of alcohol-related mortality for men tended also to have relatively high rates for women. In a small number of areas (8 out of 144) the relationship between men's and women's alcohol-related mortality rates was significantly different.
<b>Conclusion</b>
In as far as geographic location captures exposure to social and economic environment, our results suggest that the relationship between social and economic environment and alcohol-related harm is very similar for men and women. The existence of a small number of areas in which men's and women's alcohol-related mortality had an different relationship suggests that some places may have unusual drinking cultures. These might prove useful for further investigations into the factors which influence drinking behaviour in men and women
Analysis of stellar spectra with 3D and NLTE models
Models of radiation transport in stellar atmospheres are the hinge of modern
astrophysics. Our knowledge of stars, stellar populations, and galaxies is only
as good as the theoretical models, which are used for the interpretation of
their observed spectra, photometric magnitudes, and spectral energy
distributions. I describe recent advances in the field of stellar atmosphere
modelling for late-type stars. Various aspects of radiation transport with 1D
hydrostatic, LTE, NLTE, and 3D radiative-hydrodynamical models are briefly
reviewed.Comment: 21 pages, accepted for publication as a chapter in "Determination of
Atmospheric Parameters of B, A, F and G Type Stars", Springer (2014), eds. E.
Niemczura, B. Smalley, W. Pyc
Self-reported ill health in male UK Gulf War veterans: a retrospective cohort study
BACKGROUND: Forces deployed to the first Gulf War report more ill health than veterans who did not serve there. Many studies of post-Gulf morbidity are based on relatively small sample sizes and selection bias is often a concern. In a setting where selection bias relating to the ill health of veterans may be reduced, we: i) examined self-reported adult ill health in a large sample of male UK Gulf War veterans and a demographically similar non-deployed comparison group; and ii) explored self-reported ill health among veterans who believed that they had Gulf War syndrome. METHODS: This study uses data from a retrospective cohort study of reproduction and child health in which a validated postal questionnaire was sent to all UK Gulf War veterans (GWV) and a comparison cohort of Armed Service personnel who were not deployed to the Gulf (NGWV). The cohort for analysis comprises 42,818 males who responded to the questionnaire. RESULTS: We confirmed that GWV report higher rates of general ill health. GWV were significantly more likely to have reported at least one new medical symptom or disease since 1990 than NGWV (61% versus 37%, OR 2.7, 95% CI 2.5–2.8). They were also more likely to report higher numbers of symptoms. The strongest associations were for mood swings (OR 20.9, 95%CI 16.2–27.0), memory loss/lack of concentration (OR 19.6, 95% CI 15.5–24.8), night sweats (OR 9.9, 95% CI 6.5–15.2), general fatigue (OR 9.6, 95% CI 8.3–11.1) and sexual dysfunction (OR 4.6, 95%CI 3.2–6.6). 6% of GWV believed they had Gulf War syndrome (GWS), and this was associated with the highest symptom reporting. CONCLUSIONS: Increased levels of reported ill health among GWV were confirmed. This study was the first to use a questionnaire which did not focus specifically on the veterans' symptoms themselves. Nevertheless, the results are consistent with those of other studies of post-Gulf war illness and thus strengthen overall findings in this area of research. Further examination of the mechanisms underlying the reporting of ill health is required
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