1,881 research outputs found
Hypertext learning environments, cognitive flexibility, and the transfer of complex knowledge : an empirical investigation
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A continuously updated, geospatially rectified database of utility-scale wind turbines in the United States.
Over 60,000 utility-scale wind turbines are installed in the United States as of October, 2019, representing over 97 gigawatts of electric power capacity; US wind turbine installations continue to grow at a rapid pace. Yet, until April 2018, no publicly-available, regularly updated data source existed to describe those turbines and their locations. Under a cooperative research and development agreement, analysts from three organizations collaborated to develop and release the United States Wind Turbine Database (USWTDB) - a publicly available, continuously updated, spatially rectified data source of locations and attributes of utility-scale wind turbines in the United States. Technical specifications and wind facility data, incorporated from five sources, undergo rigorous quality control. The location of each turbine is visually verified using high-resolution aerial imagery. The quarterly-updated data are available in a variety of formats, including an interactive web application, comma-separated values (CSV), shapefile, and application programming interface (API). The data are used widely by academic researchers, engineers and developers from wind energy companies, government agencies, planners, educators, and the general public
Memento Mori: The development and validation of the Death Reflection Scale
Despite its potential for advancing organizational behavior (OB) research, the topic of death awareness has been vastly understudied. Moreover, research on death awareness has predominantly focused on the anxiety‐provoking aspect of death‐related cognitions, thus overlooking the positive aspect of death awareness, death reflection. This gap is exacerbated by the lack of a valid research instrument to measure death reflection. To address this issue, we offer a systematic conceptualization of death reflection, develop the Death Reflection Scale, and assess its psychometric properties across four studies. Further, using a sample of 268 firefighters, we examine whether death reflection buffers the detrimental impact of mortality cues at work on employee well‐being and safety performance. Results provide strong support for the psychometric properties of the Death Reflection Scale. Further, moderation analysis indicates death reflection weakens the negative effect of mortality cues on firefighters' safety performance. Overall, these findings suggest the newly developed Death Reflection Scale will prove useful in future research on death‐related cognitions
Trends in Poverty and Inequality in Seven African Countries
This paper aims to analyse trends in poverty and inequality in seven African countries using an asset index constructed from comparable, nationally representative surveys using multiple correspondence analysis. Improvements in the asset index are largely driven by progress in the accumulation of private assets, while access to public services has deteriorated. Continued efforts at the expansion of access to public services such as waterborne sanitation and piped water, particularly in rural areas, are thus required. Overall poverty has declined in five of the seven countries. The trends in urban and rural poverty for the most part mirror these trends in overall poverty. Five of the seven countries experienced an improvement in overall inequality. Only in Zambia has overall inequality increased. Experiences in regards to trends in urban and rural inequality are mixed. These results, however, should be interpreted with caution, given the various conceptual and methodological limitations of the asset index approach to poverty analysis.Poverty, inequality, asset index, multiple correspondence analysis, Africa
Uncovering the Origins of Spiral Structure by Measuring Radial Variation in Pattern Speeds
Current theories of spiral and bar structure predict a variety of pattern
speed behaviors, calling for detailed, direct measurement of the radial
variation of pattern speeds. Our recently developed Radial Tremaine-Weinberg
(TWR) method allows this goal to be achieved for the first time. Here we
present TWR spiral pattern speed estimates for M101, IC 342, NGC 3938 and NGC
3344 in order to investigate whether spiral structure is steady or winding,
whether spirals are described by multiple pattern speeds, and the relation
between bar and spiral speeds. Where possible, we interpret our pattern speeds
estimates according to the resonance radii associated with each (established
with the disk angular rotation), and compare these to previous determinations.
By analyzing the high-quality HI and CO data cubes available for these
galaxies, we show that it is possible to determine directly multiple pattern
speeds within these systems, and hence identify the characteristic signatures
of the processes that drive the spiral structure. Even this small sample of
galaxies reveals a surprisingly complex taxonomy, with the first direct
evidence for the presence of resonant coupling of multiple patterns found in
some systems, and the measurement of a simple single pattern speed in others.
Overall, this study demonstrates that we are now in a position to uncover more
of the apparently complex physics that lies behind spiral structure.Comment: 15 pages in emulateapj format, 12 figures, accepted for publication
in Ap
Radial Dependence of the Pattern Speed of M51
The grand-design spiral galaxy M51 has long been a crucial target for
theories of spiral structure. Studies of this iconic spiral can address the
question of whether strong spiral structure is transient (e.g.
interaction-driven) or long-lasting. As a clue to the origin of the structure
in M51, we investigate evidence for radial variation in the spiral pattern
speed using the radial Tremaine-Weinberg (TWR) method. We implement the method
on CO observations tracing the ISM-dominant molecular component. Results from
the method's numerical implementation--combined with regularization, which
smooths intrinsically noisy solutions--indicate two distinct patterns speeds
inside 4 kpc at our derived major axis PA=170 deg., both ending at corotation
and both significantly higher than the conventionally adopted global value.
Inspection of the rotation curve suggests that the pattern speed interior to 2
kpc lacks an ILR, consistent with the leading structure seen in HST near-IR
observations. We also find tentative evidence for a lower pattern speed between
4 and 5.3 kpc measured by extending the regularized zone. As with the original
TW method, uncertainty in major axis position angle (PA) is the largest source
of error in the calculation; in this study, where \delta PA=+/-5 deg. a ~20%
error is introduced to the parameters of the speeds at PA=170 deg. Accessory to
this standard uncertainty, solutions with PA=175 deg. (also admitted by the
data) exhibit only one pattern speed inside 4 kpc, and we consider this
circumstance under the semblance of a radially varying PA.Comment: 14 pages in emulateapj format, 12 figures, accepted for publication
in Ap
Predictors of paralysis in the rheumatoid cervical spine in patients undergoing total joint arthroplasty.
BACKGROUND: Rheumatoid arthritis is sometimes associated with radiographic evidence of instability of the cervical spine, most commonly an abnormal subluxation between vertebrae. When this instability compromises the space that is available for the spinal cord, it may be predictive of paralysis. However, the prevalence of radiographic signs of instability that are predictive of paralysis among patients with nonspinal orthopaedic manifestations of rheumatoid arthritis is unknown.
METHODS: Radiographs of the cervical spine of patients with rheumatoid arthritis who had undergone total joint arthroplasty over a five-year period were retrospectively reviewed. The radiographs were evaluated for predictors of paralysis (a posterior atlantodental interval of\u3c14 \u3emm) and were compared with traditional parameters of instability (an anterior atlantodental interval of \u3e3 mm or subaxial subluxation of \u3e3 mm).
RESULTS: Forty-nine of the sixty-five patients who were identified had flexion and extension lateral radiographs available for review. Only one of these patients had a posterior atlantodental interval of \u3c14 \u3emm, and only three had a space available for the cord that measuredcomparison, twenty patients had radiographic evidence of instability on the basis of traditional parameters.
CONCLUSIONS: Although nearly one-half of the patients in the present study had radiographic evidence of cervical instability on the basis of traditional measurements, only four patients (8%) had a radiographic finding that was predictive of paralysis. Thus, while radiographic evidence of cervical instability was not infrequent in this population of patients who underwent total joint arthroplasty for rheumatoid arthritis, radiographic predictors of paralysis were much less common
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