8,549 research outputs found
Origin and evolution of recent Leonid meteor showers
The four most prominent returns of the Leonid shower in the past decade fall into two broad classes. The 1966 and 1969 showers were of short duration, had a high proportion of small particles, and occured with the longest apparent delay after the perihelion passage of the parent comet Temple-Tuttle. By contrast, the 1961 and 1965 returns were of long duration, and had more large particles. The 1961 return preceded the comet. There are three major influences on particle orbits: ejection velocity, radiation pressure, and close encounters with planets. The observations are explainable in a qualitative way on the basis of the first two. But some speculation concerning the results of planetary perturbations are invoked
The Impact of New EUV Diagnostics on CME-Related Kinematics
We present the application of novel diagnostics to the spectroscopic
observation of a Coronal Mass Ejection (CME) on disk by the Extreme Ultraviolet
Imaging Spectrometer (EIS) on the Hinode spacecraft. We apply a recently
developed line profile asymmetry analysis to the spectroscopic observation of
NOAA AR 10930 on 14-15 December 2006 to three raster observations before and
during the eruption of a 1000km/s CME. We see the impact that the observer's
line-of-sight and magnetic field geometry have on the diagnostics used.
Further, and more importantly, we identify the on-disk signature of a
high-speed outflow behind the CME in the dimming region arising as a result of
the eruption. Supported by recent coronal observations of the STEREO
spacecraft, we speculate about the momentum flux resulting from this outflow as
a secondary momentum source to the CME. The results presented highlight the
importance of spectroscopic measurements in relation to CME kinematics, and the
need for full-disk synoptic spectroscopic observations of the coronal and
chromospheric plasmas to capture the signature of such explosive energy release
as a way of providing better constraints of CME propagation times to L1, or any
other point of interest in the heliosphere.Comment: Accepted to appear in Solar Physics Topical Issue titled "Remote
Sensing of the Inner Heliosphere". Manuscript has 14 pages, 5 color figures.
Movies supporting the figures can be found in
http://download.hao.ucar.edu/pub/mscott/papers/Weathe
Examining the Influence of Environmental Opportunities and Exposures on Children\u27s Sleep Duration
This research aims to fill a void in knowledge on how certain characteristics of the built and natural environments may impact childrenâs sleep duration. Data was collected on a sample of 614 children (aged 9-14 years) drawn from 22 elementary schools throughout the City of London, Ontario, Canada. Participants completed the STEAM (Spatial Temporal Environmental Activity Monitoring) protocol which involved completion of a survey, daily activity diary, and tracking the time they spent in different environments with a portable Global Position System. This thesis incorporates an innovative analytical approach which uses two Geographic Information System techniques to examine if and how different neighbourhood level environmental opportunities and exposures have an influence on childrenâs sleep duration.
Hierarchical multiple linear regressions were used to explore the relationship between childrenâs sleep duration and neighbourhood level environmental features. Analysis found that green space opportunity positively impacted childrenâs average sleep duration when measured by Normalized Difference Vegetation Index. Additionally, with each percent increase in amount of time spent around park spaces each day, childrenâs sleep duration increased by 13 minutes. From these findings, policy makers, educators, and parents can help in promoting a greater amount of time to be spent in parks for healthier sleep durations in children
Temperature dependent carrier lifetime studies of Mo in crystalline silicon
The capture cross sections of both electronsĎn and holes Ďp were determined for interstitialmolybdenum in crystalline silicon over the temperature range of â110 to 150â°C. Carrier lifetimemeasurements were performed on molybdenum-contaminated silicon using a temperature controlled photoconductance instrument. Injection dependent lifetime spectroscopy was applied at each temperature to calculate Ďp and Ďn. This analysis involved a novel approach that independently determined the capture cross sections at each temperature assuming a known defect density and thermal velocity. Since the energy state is in the lower half of the bandgap, the determination of Ďp is unaffected by the defect energy at all temperatures, and Ďp is found to decrease with temperature in a fashion consistent with excitonic Auger capture. At temperatures below 0â°C, the determination of Ďn is also unaffected by the defect energy due to the suppression of thermal emission, and Ďn decreases with temperature as well. It is shown that a projection of Ďn to higher temperature suggests the defect has an energy of 0.375 eV above the valance band edge of silicon.D.M. likes to thank the Australian Research Council for
fellowship and G.C. likes to thank âCrystalClear Integrated
Projectâ Contract No. SES6-CT_2003-502583 funded by
the European Commission
Optimizing diagnostic imaging through skills mix: costs and opportunities
YesIncreasing diagnostic capacity is a national priority to expedite the timeliness and appropriateness of patient treatment interventions. Imaging, encompassing a range of technologies including X-ray, Computer Tomography, Magnetic Resonance Imaging and ultrasound, is a key diagnostic service and central to decision making in most, if not all, disease pathways. However, imaging is an expensive discipline accounting for an estimated 3-5% of the annual NHS budget. As a result, it is imperative that we maximize service efficiency while optimizing patient outcomes
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Entrepreneurship â an undiscovered country
yesThe Body Shopâs business has been an entrepreneurial enterprise of remarkable success. Its core lies on the principle, pioneered by founder Anita Roddick, that â(âŚ) the business of business should not be just about money, it should be about responsibility.â The company is the symbol of the 1970âs corporate social responsibility (CSR) revolution
Partnership is alive and underpinning healthcare delivery
YesBryan McIntosh, senior lecturer in health management and organisational behaviour at the University of Bradford, explores the role of partnerships in the health service
Largest Mesh Deployable Antenna Technology
Preliminary assessments by both government and industry indicate that applications exist in the areas of communications, radio astronomy, and Earth observations requiring large, space based antennas. The mesh deployable antenna, based on its demonstrated success in the smaller aperture range, provides a promising near term capability for satisfying a significant number of these space-based applications. In this article the technology status of mesh deployable antennas is reviewed and design concepts applicable to very large mesh deployable reflectors are discussed. The present state-of-the-art performance is presented along with projections of potential performance improvement. These are compared with identified focus missions from the NASA Large Space Structures Technology (LSST) Program
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