202,356 research outputs found
Seeing and Exploring the Universe Resource Guide
This guide provides an overview of 16 NASA missions studying the structure and evolution of the Universe. A description of the science and educational programs for each mission is provided, along with a list of other relevant resources and websites. The following missions are described in the guide: Advanced Composition Explorer (ACE), Astro-E2, Chandra, Cosmic Hot Interstellar Plasma Spectrometer (CHIPS), Constellation X-ray Mission (CON-X), Galaxy Evolution Explorer (GALEX) Gamma-Ray Large Area Space Telescope (GLAST) Gravity Probe-B (GP-B), High Energy Transient Explorer 2 (HETE-2), International Gamma-Ray Astrophysics Laboratory (INTEGRAL), Laser Interferometer Space Antenna (LISA), Microwave Anisotropy Probe (MAP), Rossi X-ray Timing Explorer (RXTE), Submillimeter Wave Astronomy Satellite (SWAS), Swift, and X-ray Multi-Mirror-Newton Mission (XMM-Newton). Educational levels: Primary elementary, Intermediate elementary, Middle school, High school
Spartan Daily, March 3, 1981
Volume 76, Issue 25https://scholarworks.sjsu.edu/spartandaily/6729/thumbnail.jp
Spartan Daily, March 3, 1981
Volume 76, Issue 25https://scholarworks.sjsu.edu/spartandaily/6729/thumbnail.jp
Spartan Daily, March 3, 1981
Volume 76, Issue 25https://scholarworks.sjsu.edu/spartandaily/6729/thumbnail.jp
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Identifying factors likely to influence compliance with diagnostic imaging guideline recommendations for spine disorders among chiropractors in North America: a focus group study using the Theoretical Domains Framework
Background: The Theoretical Domains Framework (TDF) was developed to investigate determinants of specific clinical behaviors and inform the design of interventions to change professional behavior. This framework was used to explore the beliefs of chiropractors in an American Provider Network and two Canadian provinces about their adherence to evidence-based recommendations for spine radiography for uncomplicated back pain. The primary objective of the study was to identify chiropractors’ beliefs about managing uncomplicated back pain without xrays and to explore barriers and facilitators to implementing evidence-based recommendations on lumbar spine xrays. A secondary objective was to compare chiropractors in the United States and Canada on their beliefs regarding the use of spine x-rays.
Methods: Six focus groups exploring beliefs about managing back pain without x-rays were conducted with a purposive sample. The interview guide was based upon the TDF. Focus groups were digitally recorded, transcribed verbatim, and analyzed by two independent assessors using thematic content analysis based on the TDF.
Results: Five domains were identified as likely relevant. Key beliefs within these domains included the following: conflicting comments about the potential consequences of not ordering x-rays (risk of missing a pathology, avoiding adverse treatment effects, risks of litigation, determining the treatment plan, and using x-ray-driven techniques contrasted with perceived benefits of minimizing patient radiation exposure and reducing costs; beliefs about consequences); beliefs regarding professional autonomy, professional credibility, lack of standardization, and agreement with guidelines widely varied (social/professional role & identity); the influence of formal training, colleagues, and patients also appeared to be important factors (social influences); conflicting comments regarding levels of confidence and comfort in managing patients without x-rays (belief about capabilities); and guideline awareness and agreements (knowledge).
Conclusions: Chiropractors’ use of diagnostic imaging appears to be influenced by a number of factors. Five key domains may be important considering the presence of conflicting beliefs, evidence of strong beliefs likely to impact the behavior of interest, and high frequency of beliefs. The results will inform the development of a theorybased survey to help identify potential targets for behavioral-change strategies
Use of Gas Electron Multiplier (GEM) Detectors for an Advanced X-ray Monitor
We describe a concept for a NASA SMEX Mission in which Gas Electron
Multiplier (GEM) detectors, developed at CERN, are adapted for use in X-ray
astronomy. These detectors can be used to obtain moderately large detector area
and two-dimensional photon positions with sub mm accuracy in the range of 1.5
to 15 keV. We describe an application of GEMs with xenon gas, coded mask
cameras, and simple circuits for measuring event positions and for
anticoincidence rejection of particle events. The cameras are arranged to cover
most of the celestial sphere, providing high sensitivity and throughput for a
wide variety of cosmic explosions. At longer timescales, persistent X-ray
sources would be monitored with unprecedented levels of coverage. The
sensitivity to faint X-ray sources on a one-day timescale would be improved by
a factor of 6 over the capability of the RXTE All Sky Monitor.Comment: 10 pages, 5 figs., in X-Ray and Gamma Ray Instrumentation for
Astronomy XI, SPIE conference, San Diego, Aug. 200
Observation of enhanced X-ray emission from the CTTS AA Tau during a transit of an accretion funnel
AA Tau was observed for about 5h per XMM orbit (2 days) over 8 successive
orbits, which covers two optical eclipse periods (8.2 days). The XMM optical/UV
monitor simultaneously provided UV photometry with a ~15 min sampling rate.
Some V-band photometry was also obtained from the ground during this period in
order to determine the dates of the eclipses. Two X-ray and UV measurements
were secured close to the center of the eclipse. The UV flux is the highest
just before the eclipse starts and the lowest towards the end of it. We model
the UV flux variations with a weekly modulation (inner disk eclipse), plus a
daily modulation, which suggests a non-steady accretion. No eclipses are
detected in X-rays. For one measurement, the X-ray count rate was nearly 50
times stronger than the minimum observed level, and the plasma temperature
reached 60 MK, i.e., a factor of 2-3 higher than in the other observations.
This X-ray event, observed close to the center of the optical eclipse, is
interpreted as an X-ray flare. We identify the variable column density with the
low-density accretion funnel flows blanketing the magnetosphere. The lack of
X-ray eclipses indicates that X-ray emitting regions are located at high
latitudes. Furthermore, the occurrence of a strong X-ray flare near the center
of the optical eclipse suggests that the magnetically active areas are closely
associated with the base of the high-density accretion funnel flow. We
speculate that the impact of this free falling accretion flow onto the strong
magnetic field of the stellar corona may boost the X-ray emission (abridged).Comment: 17 pages and 9 Figures. Accepted by A&
The Global 21-cm Signal in the Context of the High-z Galaxy Luminosity Function
Motivated by recent progress in studies of the high- Universe, we build a
new model for the global 21-cm signal that is explicitly calibrated to
measurements of the galaxy luminosity function (LF) and further tuned to match
the Thomson scattering optical depth of the cosmic microwave background,
. Assuming that the galaxy population can be smoothly
extrapolated to higher redshifts, the recent decline in best-fit values of
and the inefficient heating induced by X-ray binaries (HMXBs; the
presumptive sources of the X-ray background at high-) imply that the
entirety of cosmic reionization and reheating occurs at redshifts . In contrast to past global 21-cm models, whose (
MHz) absorption features and strong mK emission features were driven
largely by the assumption of efficient early star-formation and X-ray heating,
our new fiducial model peaks in absorption at MHz at a depth of
mK and has a negligible emission component. As a result, a strong
emission signal would provide convincing evidence that HMXBs are not the only
drivers of cosmic reheating. Shallow absorption troughs should accompany strong
heating scenarios, but could also be caused by a low escape fraction of
Lyman-Werner photons. Generating signals with troughs at MHz
requires a floor in the star-formation efficiency in halos below , which is equivalent to steepening the faint-end of the galaxy LF.
These findings demonstrate that the global 21-cm signal is a powerful
complement to current and future galaxy surveys and efforts to better
understand the interstellar medium in high- galaxies.Comment: 17 pages, 9 figures, in pres
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