770,721 research outputs found
Factorial Structure and Measurement Invariance of the Acceptance and Action Questionnaire-Stigma (AAQ-S) in Spain
The objective of the present study was to validate and adapt the Acceptance and Action Questionnaire-Stigma (AAQ-S) to the Spanish context. Method: The study included the participation of 1212 subjects, with an average age of 17.12 years old. Results: The confirmatory factorial analysis revealed a number of adequate fit indices for the new version of the scale χ2/df = 3.24; Comparative Fit Index = 0.96; Incremental Fit Index = 0.96; Root Mean Square Error of Approximation = 0.060; Standardized Root Mean Square Residual = 0.035, in which the factorial structures displayed gender invariance. The two factors comprise the scale both exhibited high internal consistency (+0.90) and temporal stability. Conclusion: The Spanish version of the AAQ-S proved to be a robust and adequate psychometric instrument. In this sense, future lines of research focused on determining the role of psychological flexibility in stigma and the processes of change at the base of interventions could benefit substantially from the use of AAQ-S
Parameter Estimation for Fractional Ornstein-Uhlenbeck Processes: Non-ergodic Case
We consider the parameter estimation problem for the non-ergodic fractional
Ornstein-Uhlenbeck process defined as , with a
parameter , where is a fractional Brownian motion of Hurst index
. We study the consistency and the asymptotic distributions of the
least squares estimator of based on the observation
as .Comment: 13 page
The Prediction value
We introduce the prediction value (PV) as a measure of players' informational
importance in probabilistic TU games. The latter combine a standard TU game and
a probability distribution over the set of coalitions. Player 's prediction
value equals the difference between the conditional expectations of when
cooperates or not. We characterize the prediction value as a special member
of the class of (extended) values which satisfy anonymity, linearity and a
consistency property. Every -player binomial semivalue coincides with the PV
for a particular family of probability distributions over coalitions. The PV
can thus be regarded as a power index in specific cases. Conversely, some
semivalues -- including the Banzhaf but not the Shapley value -- can be
interpreted in terms of informational importance.Comment: 26 pages, 2 table
Synchrotron Cooling in Energetic Gamma-Ray Bursts Observed by the Fermi Gamma-Ray Burst Monitor
We study the time-resolved spectra of eight GRBs observed by Fermi GBM in its
first five years of mission, with 1 keV - 1 MeV fluence
erg cm and signal-to-noise level above 900 keV. We
aim to constrain in detail the spectral properties of GRB prompt emission on a
time-resolved basis and to discuss the theoretical implications of the fitting
results in the context of various prompt emission models. We perform
time-resolved spectral analysis using a variable temporal binning technique
according to optimal S/N criteria, resulting in a total of 299 time-resolved
spectra. We fit the Band function to all spectra and obtain the distributions
for the low-energy power-law index , the high-energy power-law index
, the peak energy in the observed spectrum , and
the difference between the low- and high-energy power-law indices . Using the distributions of and , the
electron population index is found to be consistent with the "moderately
fast" scenario which fast- and slow-cooling scenarios cannot be distinguished.
We also apply a physically motivated synchrotron model, which is a triple
power-law with constrained power-law indices and a blackbody component, to test
for consistency with a synchrotron origin for the prompt emission and obtain
the distributions for the two break energies and ,
the middle segment power-law index , and the Planck function temperature
. A synchrotron model is found consistent with the majority of
time-resolved spectra for these eight energetic Fermi GBM bursts with good
high-energy photon statistics, as long as both the cooling and injection break
are included and the leftmost spectral slope is lifted either by inclusion of a
thermal component or when an evolving magnetic field is accounted for.Comment: 20 pages, 7 figures, 8 tables, accepted for publication in A&
A Nonparametric Bayesian Approach to Copula Estimation
We propose a novel Dirichlet-based P\'olya tree (D-P tree) prior on the
copula and based on the D-P tree prior, a nonparametric Bayesian inference
procedure. Through theoretical analysis and simulations, we are able to show
that the flexibility of the D-P tree prior ensures its consistency in copula
estimation, thus able to detect more subtle and complex copula structures than
earlier nonparametric Bayesian models, such as a Gaussian copula mixture.
Further, the continuity of the imposed D-P tree prior leads to a more favorable
smoothing effect in copula estimation over classic frequentist methods,
especially with small sets of observations. We also apply our method to the
copula prediction between the S\&P 500 index and the IBM stock prices during
the 2007-08 financial crisis, finding that D-P tree-based methods enjoy strong
robustness and flexibility over classic methods under such irregular market
behaviors
Massive Scattering Amplitudes in Six Dimensions
We show that a natural spinor-helicity formalism that can describe massive
scattering amplitudes exists in dimensions. This is arranged by having
helicity spinors carry an index in the Dirac spinor {\bf 4} of the massive
little group, . In the high energy limit, two separate kinds
of massless helicity spinors emerge as required for consistency with
arXiv:0902.0981, with indices in the two 's of the massless little group
. The tensors of lead to particles with arbitrary spin, and
using these and demanding consistent factorization, we can fix and
point tree amplitudes of arbitrary masses and spins: we provide examples.
We discuss the high energy limit of scattering amplitudes and the Higgs
mechanism in this language, and make some preliminary observations about
massive BCFW recursion.Comment: 37 pages; v2: minor improvements, JHEP versio
Swift XRT Observations of the Afterglow of XRF 050416A
Swift discovered XRF 050416A with the BAT and began observing it with its
narrow field instruments only 64.5 s after the burst onset. Its very soft
spectrum classifies this event as an X-ray flash. The afterglow X-ray emission
was monitored up to 74 days after the burst. The X-ray light curve initially
decays very fast, subsequently flattens and eventually steepens again, similar
to many X-ray afterglows. The first and second phases end about 172 and 1450 s
after the burst onset, respectively. We find evidence of spectral evolution
from a softer emission with photon index Gamma ~ 3.0 during the initial steep
decay, to a harder emission with Gamma ~ 2.0 during the following evolutionary
phases. The spectra show intrinsic absorption in the host galaxy. The
consistency of the initial photon index with the high energy BAT photon index
suggests that the initial phase of the X-ray light curve may be the low-energy
tail of the prompt emission. The lack of jet break signatures in the X-ray
afterglow light curve is not consistent with empirical relations between the
source rest-frame peak energy and the collimation-corrected energy of the
burst. The standard uniform jet model can give a possible description of the
XRF 050416A X-ray afterglow for an opening angle larger than a few tens of
degrees, although numerical simulations show that the late time decay is
slightly flatter than expected from on-axis viewing of a uniform jet. A
structured Gaussian-type jet model with uniform Lorentz factor distribution and
viewing angle outside the Gaussian core is another possibility, although a full
agreement with data is not achieved with the numerical models explored.Comment: Accepted for publication on ApJ; replaced with revised version: part
of the discussion moved in an appendix; 11 pages, 6 figures; abstract
shortened for posting on astro-p
How well can we measure supermassive black hole spin?
Being one of only two fundamental properties black holes possess, the spin of
supermassive black holes (SMBHs) is of great interest for understanding
accretion processes and galaxy evolution. However, in these early days of spin
measurements, consistency and reproducibility of spin constraints have been a
challenge. Here we focus on X-ray spectral modelling of active galactic nuclei
(AGN), examining how well we can truly return known reflection parameters such
as spin under standard conditions. We have created and fit over 4000 simulated
Seyfert 1 spectra each with 3751k counts. We assess the fits with
reflection fraction of = 1 as well as reflection-dominated AGN with =
5. We also examine the consequence of permitting fits to search for retrograde
spin. In general, we discover that most parameters are over-estimated when
spectroscopy is restricted to the 2.5 - 10.0 keV regime and that models are
insensitive to inner emissivity index and ionization. When the bandpass is
extended out to 70keV, parameters are more accurately estimated. Repeating the
process for = 5 reduces our ability to measure photon index (3 to 8
per cent error and overestimated), but increases precision in all other
parameters -- most notably ionization, which becomes better constrained
(45 erg cm ) for low ionization parameters (200 erg
cm ). In all cases, we find the spin parameter is only well
measured for the most rapidly rotating supermassive black holes (i.e.
0.8 to about 0.10) and that inner emissivity index is never well
constrained. Allowing our model to search for retrograde spin did not improve
the results.Comment: Accepted for publication in MNRAS. 13 pages, 7 figure
- …