2,981 research outputs found
Putting theory oriented evaluation into practice
Evaluations of gaming simulations and business games as teaching devices are typically end-state driven. This emphasis fails to detect how the simulation being evaluated does or does not bring about its desired consequences. This paper advances the use of a logic model approach which possesses a holistic perspective that aims at including all elements associated with the situation created by a game. The use of the logic model approach is illustrated as applied to Simgame, a board game created for secondary school level business education in six European Union countries
A large‐scale view of Space Technology 5 magnetometer response to solar wind drivers
In this data report we discuss reprocessing of the Space Technology 5 (ST5) magnetometer database for inclusion in NASA's Coordinated Data Analysis Web (CDAWeb) virtual observatory. The mission consisted of three spacecraft flying in elliptical orbits, from 27 March to 27 June 2006. Reprocessing includes (1) transforming the data into the Modified Apex Coordinate System for projection to a common reference altitude of 110 km, (2) correcting gain jumps, and (3) validating the results. We display the averaged magnetic perturbations as a keogram, which allows direct comparison of the full‐mission data with the solar wind values and geomagnetic indices. With the data referenced to a common altitude, we find the following: (1) Magnetic perturbations that track the passage of corotating interaction regions and high‐speed solar wind; (2) unexpectedly strong dayside perturbations during a solstice magnetospheric sawtooth oscillation interval characterized by a radial interplanetary magnetic field (IMF) component that may have enhanced the accompanying modest southward IMF; and (3) intervals of reduced magnetic perturbations or “calms,” associated with periods of slow solar wind, interspersed among variable‐length episodic enhancements. These calms are most evident when the IMF is northward or projects with a northward component onto the geomagnetic dipole. The reprocessed ST5 data are in very good agreement with magnetic perturbations from the Defense Meteorological Satellite Program (DMSP) spacecraft, which we also map to 110 km. We briefly discuss the methods used to remap the ST5 data and the means of validating the results against DMSP. Our methods form the basis for future intermission comparisons of space‐based magnetometer data.Key PointsST5 Magnetic Perturbations Have Been ReprocessedReprocessed data at 100 km compare well to DMSP dataKeogram view of data show response to several solar wind driversPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/111800/1/ess222.pd
Increasing doses of fiber do not influence short-term satiety or food intake and are inconsistently linked to gut hormone levels
Background: People who eat more fiber often have a lower body weight than people who eat less fiber. The mechanism for this relationship has been explained, in part, by increased satiety, which may occur as a result of changes in appetite-suppressing gut hormone levels, and decreases in food intake at subsequent meals. Objective: We hypothesized that increasing doses of mixed fiber, consumed in muffins for breakfast, would proportionally influence satiety, gut hormone levels, and subsequent food intake. Design: This was a randomized, double-blind, crossover study. Healthy men (n=10) and women (n=10) with a BMI of 24±2 (mean±SEM) participated in this study. Fasting subjects consumed a muffin with 0, 4, 8, or 12 g of mixed fibers and approximately 500 kcal. Visual analog scales rated hunger and satiety for 3 h; blood was drawn to measure ghrelin, glucagon-like peptide-1 (GLP-1), and peptide YY3–36 (PYY3–36) at various intervals; and food intake was measured at an ad libitum lunch. Results: Responses to satiety-related questions did not differ among treatments. However, despite lack of differences in satiety, gut hormone levels differed among treatments. Ghrelin was higher after the 12 g fiber dose than after the 4 and 8 g fiber doses. GLP-1 was higher after the 0 g fiber dose than after the 12 and 4 g fiber doses, and PYY3–36 did not differ among fiber doses. Food intake was also indistinguishable among doses. Conclusion: Satiety, gut hormone response, and food intake did not change in a dose-dependent manner after subjects consumed 0, 4, 8, and 12 g of mixed fiber in muffins for breakfast
Chandra detection of extended X-ray emission from the recurrent nova RS Ophiuchi
Radio, infrared, and optical observations of the 2006 eruption of the
symbiotic recurrent nova RS Ophiuchi (RS Oph) showed that the explosion
produced non-spherical ejecta. Some of this ejected material was in the form of
bipolar jets to the east and west of the central source. Here we describe Xray
observations taken with the Chandra X-ray Observatory one and a half years
after the beginning of the outburst that reveal narrow, extended structure with
a position angle of approximately 300 degrees (east of north). Although the
orientation of the extended feature in the X-ray image is consistent with the
readout direction of the CCD detector, extensive testing suggests that the
feature is not an artifact. Assuming it is not an instrumental effect, the
extended X-ray structure shows hot plasma stretching more than 1,900 AU from
the central binary (taking a distance of 1.6 kpc). The X-ray emission is
elongated in the northwest direction - in line with the extended infrared
emission and some minor features in the published radio image. It is less
consistent with the orientation of the radio jets and the main bipolar optical
structure. Most of the photons in the extended X-ray structure have energies of
less than 0.8 keV. If the extended X-ray feature was produced when the nova
explosion occurred, then its 1".2 length as of 2007 August implies that it
expanded at an average rate of more than 2 mas/d, which corresponds to a flow
speed of greater than 6,000 km/s (d/1.6 kpc) in the plane of the sky. This
expansion rate is similar to the earliest measured expansion rates for the
radio jets.Comment: accepted in Ap
X-Atlas: An Online Archive of Chandra's Stellar High Energy Transmission Gratings Observations
The high-resolution X-ray spectroscopy made possible by the 1999 deployment
of the Chandra X-ray Observatory has revolutionized our understanding of
stellar X-ray emission. Many puzzles remain, though, particularly regarding the
mechanisms of X-ray emission from OB stars. Although numerous individual stars
have been observed in high-resolution, realizing the full scientific potential
of these observations will necessitate studying the high-resolution Chandra
dataset as a whole. To facilitate the rapid comparison and characterization of
stellar spectra, we have compiled a uniformly processed database of all stars
observed with the Chandra High Energy Transmission Grating (HETG). This
database, known as X-Atlas, is accessible through a web interface with
searching, data retrieval, and interactive plotting capabilities. For each
target, X-Atlas also features predictions of the low-resolution ACIS spectra
convolved from the HETG data for comparison with stellar sources in archival
ACIS images. Preliminary analyses of the hardness ratios, quantiles, and
spectral fits derived from the predicted ACIS spectra reveal systematic
differences between the high-mass and low-mass stars in the atlas and offer
evidence for at least two distinct classes of high-mass stars. A high degree of
X-ray variability is also seen in both high and low-mass stars, including
Capella, long thought to exhibit minimal variability. X-Atlas contains over 130
observations of approximately 25 high-mass stars and 40 low-mass stars and will
be updated as additional stellar HETG observations become public. The atlas has
recently expanded to non-stellar point sources, and Low Energy Transmission
Grating (LETG) observations are currently being added as well
VLT/FLAMES-ARGUS observations of stellar wind--ISM cloud interactions in NGC 6357
We present optical/near-IR IFU observations of a gas pillar in the Galactic
HII region NGC 6357 containing the young open star cluster Pismis 24. These
observations have allowed us to examined in detail the gas conditions of the
strong wind-clump interactions taking place on its surface. We identify the
presence of a narrow (~20 km/s) and broad (50-150 km/s) component to the
H_alpha emission line, where the broadest broad component widths are found in a
region that follows the shape of the eastern pillar edge. These connections
have allowed us to firmly associate the broad component with emission from
ionized gas within turbulent mixing layers on the pillar's surface set up by
the shear flows of the O-star winds from the cluster. We discuss the
implications of our findings in terms of the broad emission line component that
is increasingly found in extragalactic starburst environments. Although the
broad line widths found here are narrower, we conclude that the mechanisms
producing both must be the same. The difference in line widths may result from
the lower total mechanical wind energy produced by the O stars in Pismis 24
compared to that from a typical young massive star cluster found in a starburst
galaxy. The pillar's edge is also clearly defined by dense (<5000 cm^-3), hot
(>20000 K), and excited (via [NII]/H_a and [SII]/H_a ratios) gas conditions,
implying the presence of a D-type ionization front propagating into the pillar
surface. Although there must be both photoevaporation outflows produced by the
ionization front, and mass-loss through mechanical ablation, we see no evidence
for any significant bulk gas motions on or around the pillar. We postulate that
the evaporated/ablated gas must be rapidly heated before being entrained.Comment: 9 pages, 5 figures (3 colour). Accepted for publication in MNRA
Direct current control of three magnon scattering processes in spin-valve nanocontacts
We have investigated the generation of spin waves in the free layer of an
extended spin-valve structure with a nano-scaled point contact driven by both
microwave and direct electric current using Brillouin light scattering
microscopy. Simultaneously with the directly excited spin waves, strong
nonlinear effects are observed, namely the generation of eigenmodes with
integer multiple frequencies (2 \emph{f}, 3 \emph{f}, 4 \emph{f}) and modes
with non-integer factors (0.5 \emph{f}, 1.5 \emph{f}) with respect to the
excitation frequency \emph{f}. The origin of these nonlinear modes is traced
back to three magnon scattering processes. The direct current influence on the
generation of the fundamental mode at frequency \emph{f} can be related to the
spin-transfer torque, while the efficiency of three-magnon-scattering processes
is controlled by the Oersted field as an additional effect of the direct
current
A very luminous, highly extinguished, very fast nova - V1721 Aquilae
Fast novae are primarily located within the plane of the Galaxy, slow novae
are found within its bulge. Because of high interstellar extinction along the
line of sight many novae lying close to the plane are missed and only the
brightest seen. One nova lying very close to the Galactic plane is V1721
Aquilae, discovered in outburst on 2008 September 22. Spectra obtained 2.69
days after outburst revealed very high expansion velocities (FWHM ~6450 km/s).
In this paper we have used available pre- and post-outburst photometry and
post-outburst spectroscopy to conclude that the object is a very fast,
luminous, and highly extinguished A_V=11.6+/-0.2) nova system with an average
ejection velocity of ~3400 km/s. Pre-outburst near-IR colours from 2MASS
indicate that at quiescence the object is similar to many quiescent CNe and
appears to have a main sequence/sub-giant secondary rather than a giant. Based
on the speed of decline of the nova and its emission line profiles we
hypothesise that the axis ratio of the nova ejecta is ~1.4 and that its
inclination is such that the central binary accretion disc is face-on to the
observer. The accretion disc's blue contribution to the system's near-IR
quiescent colours may be significant. Simple models of the nova ejecta have
been constructed using the morphological modelling code XS5, and the results
support the above hypothesis. Spectral classification of this object has been
difficult owing to low S/N levels and high extinction, which has eliminated all
evidence of any He/N or FeII emission within the spectra. We suggest two
possibilities for the nature of V1721 Aql: that it is a U Sco type RN with a
sub-giant secondary or, less likely, that it is a highly energetic bright and
fast classical nova with a main sequence secondary. Future monitoring of the
object for possible RN episodes may be worthwhile, as would archival searches
for previous outbursts.Comment: 9 pages 10 figures, accepted for publication in A&A. Abstract has
been slightly shortened from published versio
- …