2,360 research outputs found
Effect of primordial non-Gaussianities on the far-UV luminosity function of high-redshift galaxies: implications for cosmic reionization
[Abridged] Understanding how the intergalactic medium (IGM) was reionized at
z > 6 is one of the big challenges of current high redshift astronomy. It
requires modelling the collapse of the first astrophysical objects (Pop III
stars, first galaxies) and their interaction with the IGM, while at the same
time pushing current observational facilities to their limits. The
observational and theoretical progress of the last few years have led to the
emergence of a coherent picture in which the budget of hydrogen-ionizing
photons is dominated by low-mass star-forming galaxies, with little
contribution from Pop III stars and quasars. The reionization history of the
Universe therefore critically depends on the number density of low-mass
galaxies at high redshift. In this work, we explore how changes in the
statistical properties of initial density fluctuations affect the formation of
early galaxies. Following Habouzit et al. (2014), we run 5 N-body simulations
with Gaussian and (scale-dependent) non-Gaussian initial conditions, all
consistent with Planck constraints. By appealing to a galaxy formation model
and to a population synthesis code, we compute the far-UV galaxy luminosity
function down to M_UV = -14 at redshift 7 < z < 15. We find that models with
strong primordial non-Gaussianities on < Mpc scales show a far-UV luminosity
function significantly enhanced in low-mass galaxies. We adopt a reionization
model calibrated from state-of-the-art hydrodynamical simulations and show that
such non-Gaussianities leave a clear imprint on the Universe reionization
history and electron Thomson scattering optical depth tau_E. Although current
uncertainties in the physics of reionization and on the determination of tau_E
still dominate the signatures of non-Gaussianities, our results suggest that
tau_E could ultimately be used to constrain the statistical properties of
initial density fluctuations.Comment: 18 pages, 12 figures, accepted for publication in MNRA
Foundations in Wisconsin: A Directory [27th ed. 2008]
The 2008 release of Foundations in Wisconsin marks the 27th edition of the print directory and the 8th year of the online version (www.wifoundations.org). The directory is designed as a research tool for grantseekers interested in locating information on private, corporate, and community foundations registered in Wisconsin. Each entry in this new edition has been updated or reviewed to provide the most current information available. Most of the data was drawn from IRS 990-PF tax returns filed by the foundations. However, additional information was obtained from surveys, foundation Web sites, annual reports, and newsletters.
Wisconsin foundations have shown continued growth in key areas. The number of active grantmaking foundations has risen to an all-time high of 1,275, with 70 new foundations identified since last year’s publication. While the total grants remained stable at 7.2 billion.https://epublications.marquette.edu/lib_fiw/1002/thumbnail.jp
ZETA - Zero-Trust Authentication: Relying on Innate Human Ability, not Technology
Reliable authentication requires the devices and
channels involved in the process to be trustworthy; otherwise
authentication secrets can easily be compromised. Given the
unceasing efforts of attackers worldwide such trustworthiness
is increasingly not a given. A variety of technical solutions,
such as utilising multiple devices/channels and verification
protocols, has the potential to mitigate the threat of untrusted
communications to a certain extent. Yet such technical solutions
make two assumptions: (1) users have access to multiple
devices and (2) attackers will not resort to hacking the human,
using social engineering techniques. In this paper, we propose
and explore the potential of using human-based computation
instead of solely technical solutions to mitigate the threat of
untrusted devices and channels. ZeTA (Zero Trust Authentication
on untrusted channels) has the potential to allow people to
authenticate despite compromised channels or communications
and easily observed usage. Our contributions are threefold:
(1) We propose the ZeTA protocol with a formal definition
and security analysis that utilises semantics and human-based
computation to ameliorate the problem of untrusted devices
and channels. (2) We outline a security analysis to assess
the envisaged performance of the proposed authentication
protocol. (3) We report on a usability study that explores the
viability of relying on human computation in this context
Mary\u27s Flowers: A Matching Game
Matching game using images of flowers named for the Blessed Virgin Mary. Illustrations by Brother A. Joseph Barrish, S.M
Clarinet, Flute and String Ensembles
Kennesaw State University School of Music presents Clarinet, Flute and String Ensembles.https://digitalcommons.kennesaw.edu/musicprograms/1727/thumbnail.jp
Intraspeaker Comparisons of Acoustic and Articulatory Variability in American English /r/ Productions
The purpose of this report is to test the hypothesis that speakers utilize an acoustic, rather than articulatory, planning space for speech production. It has been well-documented that many speakers of American English use different tongue configurations to produce /r/ in different phonetic contexts. The acoustic planning hypothesis suggests that although the /r/ configuration varies widely in different contexts, the primary acoustic cue for /r/, a dip in the F3 trajectory, will be less variable due to tradeoffs in articulatory variability, or trading relations, that help maintain a relatively constant F3 trajectory across phonetic contexts. Acoustic data and EMMA articulatory data from seven speakers producing /r/ in different phonetic contexts were analyzed. Visual inspection of the EMMA data at the point of F3 minimum revealed that each speaker appeared to use at least two of three trading relation strategies that would be expected to reduce F3 variability. Articulatory covariance measures confirmed that all seven speakers utilized a trading relation between tongue back height and tongue back horizontal position, six speakers utilized a trading relation between tongue tip height and tongue back height, and the speaker who did not use this latter strategy instead utilized a trading relation between tongue tip height and tongue back horizontal position. Estimates of F3 variability with and without the articulatory covariances indicated that F3 would be much higher for all speakers if the articulatory covariances were not utilized. These conclusions were further supported by a comparison of measured F3 variability to F3 variabilities estimated from the pellet data with and without articulatory covariances. In all subjects, the actual F3 variance was significantly lower than the F3 variance estimated without articulatory covariances, further supporting the conclusion that the articulatory trading relations were being used to reduce F3 variability. Together, these results strongly suggest that the neural control mechanisms underlying speech production make elegant use of trading relations between articulators to maintain a relatively invariant acoustic trace for /r/ across phonetic contexts
Factor Structure of the Psychopathic Personality Inventory (PPI): Findings From a Large Incarcerated Sample
Exploratory factor analysis (EFA) of the Psychopathic Personality Inventory (PPI; S. O. Lilienfeld, 1990; S. O. Lilienfeld & B. P. Andrews, 1996) with a community sample has suggested that the PPI subscales may comprise 2 higher order factors (S. D. Benning, C. J. Patrick, B. M. Hicks, D. M. Blonigen, & R. F. Krueger, 2003). However, substantive and structural evidence raises concerns about the viability of this 2-factor model, particularly in offender populations. The authors attempted to replicate the S. D. Benning et al. 2-factor solution using a large (N= 1,224) incarcerated male sample. Confirmatory factor analysis of this model resulted in poor model fit. Similarly, using the same EFA procedures as did S. D. Benning et al., the authors found little evidence for a 2-factor model. When they followed the recommendations of J.-W. van Prooijen and W. A. van der Kloot (2001) for recovering EFA solutions, model fit results provided some evidence that a 3-factor EFA solution could be recovered via confirmatory factor analysis
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