10,729 research outputs found
Rocket spectrometer for investigation of the far ultraviolet solar spectrum
A rocket-borne Ebert spectrometer and telescope were used for analysis of the solar spectrum. The instrument was arranged in the high resolution line scanning mode. Selected emission lines between 1170 and 1640 A were scanned, and a complete wavelength scan was made from 1170 A to 1850 A. Accurate measurements were made of the line profiles of the He II lines at 1640 A, C IV lines at 1550 A, Si IV lines at 1400 A, C II lines at 1335 A, the N V lines at 1240 A, and the C III lines at 1175 A. Accurate intensity measurements of the quiet sun spectrum for wavelengths between 1174 A and 3220 A were obtained. Spectral resolution was better than 0.03 A over most of the range and spatial resolution was relatively low so that the observations are averaged over the chromospheric network. Plots of absolute intensity versus wave length were prepared for the full wavelength range of the observations
Open Educational Resource (OER) Adoption in Higher Education: Examining Institutional Perspectives
The costs associated with education, including tuition and learning resources, continue to rise causing affordability issues for learners. It has been reported that the cost of traditional textbooks and materials has risen by as much as 103% over the past decade (U.S. Bureau of Labor Statistics, 2018). Due to this increase, many students have opted out of purchasing required textbooks for classes. A study conducted in Florida found that 67% of students did not purchase required textbooks (Florida Virtual Campus, 2016). Institutions of Higher Education are becoming increasingly concerned with textbook affordability and the impact on academic performance, achievement, and completion (Jhangiani, Dastur, LeGrand, & Penner, 2018). These institutions have begun delving deeper into the issues associated with textbook affordability and seeking ways to reverse the negative effects experienced by learners due to rising textbook costs.
The implementation of open educational resources (OER) may be the solution, however, the impact of these resources is still undefined. OERs are being examined as cost-effective substitutions to traditional textbooks and literature suggests that OERs are equally effective and are comparable in quality to traditional textbooks (Hilton, n.d.). Current literature recommends further exploration concerning stakeholder perspectives of OER adoption and integration as well as examining the impact of OERs across educational institutions globally. A case study conducted at a state college in Florida sought to examine the perspectives of a group of four identified stakeholder groups (i.e., faculty, librarians, instructional designers, and students) in order to better understand the impact of these OERs at the institutional level (Wright, 2018)
The Energy-dependent X-ray Timing Characteristics of the Narrow Line Seyfert 1 Mkn 766
We present the energy-dependent power spectral density (PSD) and
cross-spectral properties of Mkn 766, obtained from combining data obtained
during an XMM-Newton observation spanning six revolutions in 2005 with data
obtained from an XMM-Newton long-look in 2001. The PSD shapes and rms-flux
relations are found to be consistent between the 2001 and 2005 observations,
suggesting the 2005 observation is simply a low-flux extension of the 2001
observation and permitting us to combine the two data sets. The resulting PSD
has the highest temporal frequency resolution for any AGN PSD measured to date.
Applying a broken power-law model yields break frequencies which increase in
temporal frequency with photon energy. Obtaining a good fit when assuming
energy-independent break frequencies requires the presence of a Lorentzian at
4.6+/-0.4 * 10^-4 Hz whose strength increases with photon energy, a behavior
seen in black hole X-ray binaries. The cross-spectral properties are measured;
temporal frequency-dependent soft-to-hard time lags are detected in this object
for the first time. Cross-spectral results are consistent with those for other
accreting black hole systems. The results are discussed in the context of
several variability models, including those based on inwardly-propagating
viscosity variations in the accretion disk.Comment: Accepted for publication in The Astrophysical Journal. 18 pages, 9
figures. Uses emulateapj5.st
Direct Measurement of the X-ray Time-Delay Transfer Function in Active Galactic Nuclei
The origin of the observed time lags, in nearby active galactic nuclei (AGN),
between hard and soft X-ray photons is investigated using new XMM-Newton data
for the narrow-line Seyfert I galaxy Ark 564 and existing data for 1H0707-495
and NGC 4051. These AGN have highly variable X-ray light curves that contain
frequent, high peaks of emission. The averaged light curve of the peaks is
directly measured from the time series, and it is shown that (i) peaks occur at
the same time, within the measurement uncertainties, at all X-ray energies, and
(ii) there exists a substantial tail of excess emission at hard X-ray energies,
which is delayed with respect to the time of the main peak, and is particularly
prominent in Ark 564. Observation (i) rules out that the observed lags are
caused by Comptonization time delays and disfavors a simple model of
propagating fluctuations on the accretion disk. Observation (ii) is consistent
with time lags caused by Compton-scattering reverberation from material a few
thousand light-seconds from the primary X-ray source. The power spectral
density and the frequency-dependent phase lags of the peak light curves are
consistent with those of the full time series. There is evidence for
non-stationarity in the Ark 564 time series in both the Fourier and peaks
analyses. A sharp `negative' lag (variations at hard photon energies lead soft
photon energies) observed in Ark 564 appears to be generated by the shape of
the hard-band transfer function and does not arise from soft-band reflection of
X-rays. These results reinforce the evidence for the existence of X-ray
reverberation in type I AGN, which requires that these AGN are significantly
affected by scattering from circumnuclear material a few tens or hundreds of
gravitational radii in extent.Comment: Accepted for publication in Ap
Low-Altitude Reconnection Inflow-Outflow Observations during a 2010 November 3 Solar Eruption
For a solar flare occurring on 2010 November 3, we present observations using
several SDO/AIA extreme-ultraviolet (EUV) passbands of an erupting flux rope
followed by inflows sweeping into a current sheet region. The inflows are soon
followed by outflows appearing to originate from near the termination point of
the inflowing motion - an observation in line with standard magnetic
reconnection models. We measure average inflow plane-of-sky speeds to range
from ~150-690 km/s with the initial, high-temperature inflows being the
fastest. Using the inflow speeds and a range of Alfven speeds, we estimate the
Alfvenic Mach number which appears to decrease with time. We also provide
inflow and outflow times with respect to RHESSI count rates and find that the
fast, high-temperature inflows occur simultaneously with a peak in the RHESSI
thermal lightcurve. Five candidate inflow-outflow pairs are identified with no
more than a minute delay between detections. The inflow speeds of these pairs
are measured to be 10^2 km/s with outflow speeds ranging from 10^2-10^3 km/s -
indicating acceleration during the reconnection process. The fastest of these
outflows are in the form of apparently traveling density enhancements along the
legs of the loops rather than the loop apexes themselves. These flows could
either be accelerated plasma, shocks, or waves prompted by reconnection. The
measurements presented here show an order of magnitude difference between the
retraction speeds of the loops and the speed of the density enhancements within
the loops - presumably exiting the reconnection site.Comment: 31 pages, 13 figures, 1 table, Accepted to ApJ (expected publication
~July 2012
Absorption line series and autoionization resonance structure analysis in the ultraviolet spectrum of Sr I
Photoelectric spectrometer to measure absorption line series and autoionization resonance in ultraviolet spectrum of strontium vapo
Reconnection Outflows and Current Sheet Observed with Hinode/XRT in the 2008 April 9 "Cartwheel CME" Flare
Supra-arcade downflows (SADs) have been observed with Yohkoh/SXT (soft X-rays
(SXR)), TRACE (extreme ultra-violet (EUV)), SoHO/LASCO (white light),
SoHO/SUMER (EUV spectra), and Hinode/XRT (SXR). Characteristics such as low
emissivity and trajectories which slow as they reach the top of the arcade are
consistent with post-reconnection magnetic flux tubes retracting from a
reconnection site high in the corona until they reach a lower-energy magnetic
configuration. Viewed from a perpendicular angle, SADs should appear as
shrinking loops rather than downflowing voids. We present XRT observations of
supra-arcade downflowing loops (SADLs) following a coronal mass ejection (CME)
on 2008 April 9 and show that their speeds and decelerations are consistent
with those determined for SADs. We also present evidence for a possible current
sheet observed during this flare that extends between the flare arcade and the
CME. Additionally, we show a correlation between reconnection outflows observed
with XRT and outgoing flows observed with LASCO.Comment: 32 pages, 23 figures, Accepted for publication by the Astrophysical
Journal (Oct. 2010
Patient reported frequency of lupus flare: associations with foundation makeup and sunscreen use
Objective: To test the hypothesis that usage of foundation makeup (FM) and sunscreen lotion (SS), used individually or in combination, is associated with significant changes in the likelihood of lupus symptom exacerbation. Methods: Self-reported flare days (SRF) and use of FM and SS products, were retrospectively examined in 80 Caucasian Australian women with ACR classified SLE for a year. Negative binomial regression modelled SRF days (outcome) against independent FMSS variable and covariates: age; diagnosis years; outdoor hours; BMI; stress; immune therapy medication (ITM) use. Results: Statistically significant inverse associations between SRF days and FMSS use were found. Protective effects were statistically significant (p < 0.05) for combined FMSS exposure days (OR 0.998, CI 0.997 - 1.0) and FM alone (OR 0.603, CI 0.363 - 1.0). Significant associations consistent with increased SRF risk were seen in sub-analysis models for participants taking ITM: univariate model (OR 1.968, p = 0.03); multivariate model for FMSS (OR 2.11, CI 1.161 - 3.835); FM days (OR 1.855, CI 1.023 - 3.364). Results show SRF day reduction of 0.15% for each day of product exposure. Conclusion: Study results highlight protective effects of wearing FM with or without SS. This reduction in flare days ultimately has potential to improve quality of life in SLE patients
Quantifying the radiation belt seed population in the 17 March 2013 electron acceleration event
Abstract We present phase space density (PSD) observations using data from the Magnetic Electron Ion Spectrometer instrument on the Van Allen Probes for the 17 March 2013 electron acceleration event. We confirm previous results and quantify how PSD gradients depend on the first adiabatic invariant. We find a systematic difference between the lower-energy electrons (1-MeV with a source region within the radiation belts. Our observations show that the source process begins with enhancements to the 10s-100s-keV energy seed population, followed by enhancements to the \u3e1-MeV population and eventually leading to enhancements in the multi-MeV electron population these observations provide the clearest evidence to date of the timing and nature of the radial transport of a 100s keV electron seed population into the heart of the outer belt and subsequent local acceleration of those electrons to higher radiation belt energies. Key Points Quantification of phase space density gradients inside geostationary orbit Clear differences between the source of low energy and relativistic electrons Clear observations of how the acceleration process evolves in energy
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