Radial Profiles of Star Formation in the Far Outer Regions of Galaxy Disks

Star formation in galaxies is triggered by a combination of processes, including gravitational instabilities, spiral wave shocks, stellar compression, and turbulence compression. Some of these persist in the far outer regions where the column density is far below the threshold for instabilities, making the outer disk cutoff somewhat gradual. We show that in a galaxy with a single exponential gas profile the star formation rate can have a double exponential with a shallow one in the inner part and a steep one in the outer part. Such double exponentials have been observed recently in the broad-band intensity profiles of spiral and dwarf Irregular galaxies. The break radius in our model occurs slightly outside the threshold for instabilities provided the Mach number for compressive motions remains of order unity to large radii. The ratio of the break radius to the inner exponential scale length increases for higher surface brightness disks because the unstable part extends further out. This is also in agreement with observations. Galaxies with extended outer gas disks that fall more slowly than a single exponential, such as 1/R, can have their star formation rate scale approximately as a single exponential with radius, even out to 10 disk scale lengths. Halpha profiles should drop much faster than the star formation rate as a result of the rapidly decreasing ambient density.Comment: To appear in ApJ. Available from ftp.lowell.edu/pub/dah/papers/sfouterdisks

Sitting and standing performance in a total population of children with cerebral palsy: a cross-sectional study

<p>Abstract</p> <p>Background</p> <p>Knowledge of sitting and standing performance in a total population of children with cerebral palsy (CP) is of interest for health care planning and for prediction of future ability in the individual child. In 1994, a register and a health care programme for children with CP in southern Sweden was initiated. In the programme information on how the child usually sits, stands, stands up and sits down, together with use of support or assistive devices, is recorded annually.</p> <p>Methods</p> <p>A cross-sectional study was performed, analysing the most recent report of all children with CP born 1990-2005 and living in southern Sweden during 2008. All 562 children (326 boys, 236 girls) aged 3-18 years were included in the study. The degree of independence, use of support or assistive devices to sit, stand, stand up and sit down was analysed in relation to the Gross Motor Function Classification System (GMFCS), CP subtype and age.</p> <p>Result</p> <p>A majority of the children used standard chairs (57%), could stand independently (62%) and could stand up (62%) and sit down (63%) without external support. Adaptive seating was used by 42%, external support to stand was used by 31%, to stand up by 19%, and to sit down by 18%. The use of adaptive seating and assistive devices increased with GMFCS levels (p < 0.001) and there was a difference between CP subtypes (p < 0.001). The use of support was more frequent in preschool children aged 3-6 (p < 0.001).</p> <p>Conclusion</p> <p>About 60% of children with CP, aged 3-18, use standard chairs, stand, stand up, and sit down without external support. Adding those using adaptive seating and external support, 99% of the children could sit, 96% could stand and 81% could stand up from a sitting position and 81% could sit down from a standing position. The GMFCS classification system is a good predictor of sitting and standing performance.</p

Reporting of harm in randomized controlled trials evaluating stents for percutaneous coronary intervention

<p>Abstract</p> <p>Background</p> <p>The aim of this study was to assess the reporting of harm in randomized controlled trials evaluating stents for percutaneous coronary intervention.</p> <p>Methods</p> <p>The study design was a methodological systematic review of randomized controlled trials. The data sources were MEDLINE and the Cochrane Central Register of Controlled Trials. All reports of randomized controlled trials assessing stent treatment for coronary disease published between January 1, 2003, and September 30, 2008 were selected.</p> <p>A standardized abstraction form was used to extract data.</p> <p>Results</p> <p>132 articles were analyzed. Major cardiac adverse events (death, cardiac death, myocardial infarction or stroke) were reported as primary or secondary outcomes in 107 reports (81%). However, 19% of the articles contained no data on cardiac events. The mode of data collection of adverse events was given in 29 reports (22%) and a definition of expected adverse events was provided in 47 (36%). The length of follow-up was reported in 95 reports (72%). Assessment of adverse events by an adjudication committee was described in 46 reports (35%), and adverse events were described as being followed up for 6 months in 24% of reports (n = 32), between 7 to 12 months in 42% (n = 55) and for more than 1 year in 4% (n = 5). In 115 reports (87%), numerical data on the nature of the adverse events were reported per treatment arm. Procedural complications were described in 30 articles (23%). The causality of adverse events was reported in only 4 articles.</p> <p>Conclusion</p> <p>Several harm-related data were not adequately accounted for in articles of randomized controlled trials assessing stents for percutaneous coronary intervention.</p> <p>Trials Registration</p> <p>Trials manuscript: 5534201182098351 (T80802P)</p

Tissue Tropism and Target Cells of NSs-Deleted Rift Valley Fever Virus in Live Immunodeficient Mice

Rift Valley fever, caused by a member of the Bunyaviridae family, has spread during recent years to most sub-Saharan African countries, in Egypt and in the Arabian peninsula. The virus can be transmitted by insect vectors or by direct contacts with infectious tissues. The analysis of virus replication and dissemination in laboratory animals has been hampered by the need to euthanize sufficient numbers of animals and to assay appropriate organs at various time points after infection to evaluate the viral replication. By following the bioluminescence and fluorescence of Rift Valley fever viruses expressing light reporters, we were able to track the real-time dissemination of the viruses in live immunodeficient mice. We showed that the first infected organs were the thymus, spleen and liver, but the liver rapidly became the main location of viral replication. Phagocytes also appeared as important targets, and their systemic depletion by use of clodronate liposomes decreased the number of viruses in the blood, delayed the viral dissemination and prolonged the survival of the infected mice