1,427 research outputs found
Changes in Relative Wages, 1963-1987: Supply and Demand Factors
A simple supply and demand framework is used to analyze changes in the U.S. wage structure from 1963 to 1987. Rapid secular growth in the demand for more-educated workers, 'more-skilled' workers, and females appears to be the driving force behind observed changes in the wage structure. Measured changes in the allocation of labor between industries and occupations strongly favored college graduates and females throughout the period. Movements in the college wage premium over this period appear to be strongly related to fluctuations in the rate of growth of the supply of college graduates.
A Multicenter Examination and Strategic Revisions of the Yale Global Tic Severity Scale
Objective To examine the internal consistency and distribution of the Yale Global Tic Severity Scale (YGTSS) scores to inform modification of the measure. Methods This cross-sectional study included 617 participants with a tic disorder (516 children and 101 adults), who completed an age-appropriate diagnostic interview and the YGTSS to evaluate tic symptom severity. The distributions of scores on YGTSS dimensions were evaluated for normality and skewness. For dimensions that were skewed across motor and phonic tics, a modified Delphi consensus process was used to revise selected anchor points. Results Children and adults had similar clinical characteristics, including tic symptom severity. All participants were examined together. Strong internal consistency was identified for the YGTSS Motor Tic score (α = 0.80), YGTSS Phonic Tic score (α = 0.87), and YGTSS Total Tic score (α = 0.82). The YGTSS Total Tic and Impairment scores exhibited relatively normal distributions. Several subscales and individual item scales departed from a normal distribution. Higher scores were more often used on the Motor Tic Number, Frequency, and Intensity dimensions and the Phonic Tic Frequency dimension. By contrast, lower scores were more often used on Motor Tic Complexity and Interference, and Phonic Tic Number, Intensity, Complexity, and Interference. Conclusions The YGTSS exhibits good internal consistency across children and adults. The parallel findings across Motor and Phonic Frequency, Complexity, and Interference dimensions prompted minor revisions to the anchor point description to promote use of the full range of scores in each dimension. Specific minor revisions to the YGTSS Phonic Tic Symptom Checklist were also proposed
Rapid N_H changes in NGC 4151
We have analyzed the two longest (elapsed time > 3 days) BeppoSAX
observations of the X-ray brightest Seyfert galaxy, NGC 4151, to search for
spectral variability on time-scales from a few tens of ksec to years. We found
in both cases highly significant spectral variability below ~ 6 keV down to the
shortest time-scales investigated. These variations can be naturally explained
in terms of variations in the low energy cut-off due to obscuring matter along
the line of sight. If the cut-off is modeled by two neutral absorption
components, one fully covering the source and the second covering only a
fraction of the source, the shortest time-scale of variability of a few days
constrains the location of the obscuring matter to within 3.4 X 10^4
Schwarzschild radii from the central X-ray source. This is consistent with the
distance of the Broad Emission Line Region, as inferred from reverberation
mapping, and difficult to reconcile with the parsec scale dusty molecular torus
of Krolik & Begelman (1988). We have also explored a more complex absorption
structure, namely the presence of an ionized absorber. Although the behaviour
of the ionization parameter is nicely consistent with the expectations, the
results are not completely satisfactory from the statistical point of view.
The overall absorption during the 2001 December observation is lower than in
all other historical observations with similar 2-10 keV flux. This suggests
that absorption variability plays a crucial role in the observed flux
variability of this source.Comment: Added references, corrected typos. 21 pages, 9 figures; accepted for
publication in Monthly Notices of the Royal Astronomical Society Main Journa
The Grizzly, October 18, 1985
Limerick: The Main Objective - Calm • Typesetting Equipment Offers New Experience • Letters: Ex-Rover Responds; Some Housing Needs Help; Reply for Sluggo • Financial Aid Striving to the Top • Search of Success Finds Bravo • Look Out for the Candid Cameras • Sorority Pledging Sees Light Through Tunnel • Field Hockey Battles Tough Competition • Booters Find Easier Times • Ultimate Frisbee is Here • Doleniak: Flying Higher Through the Sky • Grizzlies are Defeated • Campus Security Noteshttps://digitalcommons.ursinus.edu/grizzlynews/1148/thumbnail.jp
The X-ray spectral properties of the AGN population in the XMM-Newton bright serendipitous survey
We present here a detailed X-ray spectral analysis of the AGN belonging to
the XMM-Newton bright survey (XBS) that comprises more than 300 AGN up to
redshift ~ 2.4. We performed an X-ray analysis following two different
approaches: by analyzing individually each AGN X-ray spectrum and by
constructing average spectra for different AGN types. From the individual
analysis, we find that there seems to be an anti correlation between the
spectral index and the sources' hard X-ray luminosity, such that the average
photon index for the higher luminosity sources (> 10E44 erg/s) is significantly
flatter than the average for the lower luminosity sources. We also find that
the intrinsic column density distribution agrees with AGN unified schemes,
although a number of exceptions are found (3% of the whole sample), which are
much more common among optically classified type 2 AGN. We also find that the
so-called "soft-excess", apart from the intrinsic absorption, constitutes the
principal deviation from a power-law shape in AGN X-ray spectra and it clearly
displays different characteristics, and likely a different origin, for
unabsorbed and absorbed AGN. Regarding the shape of the average spectra, we
find that it is best reproduced by a combination of an unabsorbed (absorbed)
power law, a narrow Fe Kalpha emission line and a small (large) amount of
reflection for unabsorbed (absorbed) sources. We do not significantly detect
any relativistic contribution to the line emission and we compute an upper
limit for its equivalent width (EW) of 230 eV at the 3 sigma confidence level.
Finally, by dividing the type 1 AGN sample into high- and low-luminosity
sources, we marginally detect a decrease in the narrow Fe Kalpha line EW and in
the amount of reflection as the luminosity increases, the "so-called"
Iwasawa-Taniguchi effect.Comment: 42 pages, 15 figures, accepted for publication in Astronomy and
Astrophysic
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