816 research outputs found
Individual support for violent group action : why people lend support to nationalist paramilitary movements
This study is designed to analyze potential solutions to the collective action problem. The collective action problem refers to the social dilemma that individuals face when deciding between short-term individual interests and long-term group goals. The assumption is that individual interests are likely to outweigh those of the group. Thus, in order to resolve the dilemma researchers are forced to seek out solutions that identify different factors that will entice the individual to sacrifice their short-term interest in favor of group goals. This study analyzed this question within the context of nationalist rebellion, and focused on three potential explanations. The first is the Relative Deprivation Model relying on the Frustration-Aggression Hypothesis as the model of the individual. This explanation was found to be logically and empirically weak, and was hence dismissed as a useable explanation. The second explanation is the collective action model, which relies on a rational actor assumption of individual decision making. The third explanation is a modified relative deprivation theory, which relies on a prospect theory assumption of individual decision-making. Both of these explanations are logically sound, but they lack empirical evaluation. Therefore, the latter two models were subjected to empirical tests using evidence gathered from individuals in Northern Ireland and the Palestinian Occupied Territories. The data gathered from individuals regarding their decision processes provided falsifying evidence for the collective action explanation, and provided confirming evidence for the modified relative deprivation model
The Complete Calibration of the Color-Redshift Relation (C3R2) Survey: Survey Overview and Data Release 1
A key goal of the Stage IV dark energy experiments Euclid, LSST and WFIRST is
to measure the growth of structure with cosmic time from weak lensing analysis
over large regions of the sky. Weak lensing cosmology will be challenging: in
addition to highly accurate galaxy shape measurements, statistically robust and
accurate photometric redshift (photo-z) estimates for billions of faint
galaxies will be needed in order to reconstruct the three-dimensional matter
distribution. Here we present an overview of and initial results from the
Complete Calibration of the Color-Redshift Relation (C3R2) survey, designed
specifically to calibrate the empirical galaxy color-redshift relation to the
Euclid depth. These redshifts will also be important for the calibrations of
LSST and WFIRST. The C3R2 survey is obtaining multiplexed observations with
Keck (DEIMOS, LRIS, and MOSFIRE), the Gran Telescopio Canarias (GTC; OSIRIS),
and the Very Large Telescope (VLT; FORS2 and KMOS) of a targeted sample of
galaxies most important for the redshift calibration. We focus spectroscopic
efforts on under-sampled regions of galaxy color space identified in previous
work in order to minimize the number of spectroscopic redshifts needed to map
the color-redshift relation to the required accuracy. Here we present the C3R2
survey strategy and initial results, including the 1283 high confidence
redshifts obtained in the 2016A semester and released as Data Release 1.Comment: Accepted to ApJ. 11 pages, 5 figures. Redshifts can be found at
http://c3r2.ipac.caltech.edu/c3r2_DR1_mrt.tx
Exploring Photometric Redshifts as an Optimization Problem: An Ensemble MCMC and Simulated Annealing-Driven Template-Fitting Approach
Using a grid of million elements () adapted from
COSMOS photometric redshift (photo-z) searches, we investigate the general
properties of template-based photo-z likelihood surfaces. We find these
surfaces are filled with numerous local minima and large degeneracies that
generally confound rapid but "greedy" optimization schemes, even with
additional stochastic sampling methods. In order to robustly and efficiently
explore these surfaces, we develop BAD-Z [Brisk Annealing-Driven Redshifts
(Z)], which combines ensemble Markov Chain Monte Carlo (MCMC) sampling with
simulated annealing to sample arbitrarily large, pre-generated grids in
approximately constant time. Using a mock catalog of 384,662 objects, we show
BAD-Z samples times more efficiently compared to a brute-force
counterpart while maintaining similar levels of accuracy. Our results represent
first steps toward designing template-fitting photo-z approaches limited mainly
by memory constraints rather than computation time.Comment: 14 pages, 8 figures; submitted to MNRAS; comments welcom
An Empirical Approach to Cosmological Galaxy Survey Simulation: Application to SPHEREx Low-Resolution Spectroscopy
Highly accurate models of the galaxy population over cosmological volumes are
necessary in order to predict the performance of upcoming cosmological
missions. We present a data-driven model of the galaxy population constrained
by deep 0.1-8 imaging and spectroscopic data in the COSMOS survey,
with the immediate goal of simulating the spectroscopic redshift performance of
the proposed SPHEREx mission. SPHEREx will obtain over the full-sky
spectrophotometry at moderate spatial resolution () over the wavelength
range 0.75-4.18 and over the wavelength range 4.18-5
. We show that our simulation accurately reproduces a range of known
galaxy properties, encapsulating the full complexity of the galaxy population
and enables realistic, full end-to-end simulations to predict mission
performance. Finally, we discuss potential applications of the simulation
framework to future cosmology missions and give a description of released data
products
Predicting H{\alpha} emission line galaxy counts for future galaxy redshift surveys
Knowledge of the number density of H emitting galaxies is vital for
assessing the scientific impact of the Euclid and WFIRST missions. In this work
we present predictions from a galaxy formation model, Galacticus, for the
cumulative number counts of H-emitting galaxies. We couple Galacticus
to three different dust attenuation methods and examine the counts using each
method. A minimisation approach is used to compare the model
predictions to observed galaxy counts and calibrate the dust parameters. We
find that weak dust attenuation is required for the Galacticus counts to be
broadly consistent with the observations, though the optimum dust parameters
return large values for , suggesting that further calibration of
Galacticus is necessary. The model predictions are also consistent with
observed estimates for the optical depth and the H luminosity function.
Finally we present forecasts for the redshift distributions and number counts
for two Euclid-like and one WFIRST-like survey. For a Euclid-like survey with
redshift range and H blended
flux limit of we
predict a number density between 3900--4800 galaxies per square degree. For a
WFIRST-like survey with redshift range and blended
flux limit of we
predict a number density between 10400--15200 galaxies per square degree.Comment: 21 pages (including appendix), 12 figures, 6 tables. Accepted b
Successful Treatment of Stent Knot in the Proximal Ureter Using Ureteroscopy and Holmium Laser
Knotted ureteral stent is rare yet tedious complication that might represent a treatment challenge to the endourologist. Only twelve cases of knotted stent have been reported. Different management options have been reported, including simple traction, ureteroscopy, percutaneous removal, and open surgery. In this paper, we present the successful untying of the knot using ureteroscopy with holmium laser
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