147 research outputs found
Developmental Factors in Visual Search: A Test of the Inhibition Deficit Hypothesis in a Feature Integration Task
Simulations of Early Baryonic Structure Formation with Stream Velocity: I. Halo Abundance
It has been recently shown that the relative velocity between the dark matter
and the baryons (vbc) at the time of recombination can affect the structure
formation in the early universe (Tseliakhovich & Hirata 2010). We statistically
quantify this effect using large cosmological simulations. We use three
different high resolution sets of simulations (with separate transfer functions
for baryons and dark matter) that vary in box size, particle number, and the
value of the relative velocity between dark matter and baryons. We show that
the total number density of halos is suppressed by ~ 20% at z = 25 for vbc =
1{\sigma}(vbc), where {\sigma}(vbc) is the variance of the relative velocity,
while for vbc = 3.4{\sigma}(vbc) the relative suppression at the same redshift
reaches 50%, remaining at or above the 30% level all the way to z = 11. We also
find high abundance of "empty halos", i.e., halos that have gas fraction below
half of the cosmic mean baryonic fraction fb. Specifically we find that for vbc
= 1{\sigma}(vbc) all halos below 10^5M\odot are empty at z \geq 19. The high
abundance of empty halos results in significant delay in the formation of gas
rich mini-halos and the first galaxies.Comment: 7 pages, 8 figures, accepted to Ap
The Football Factor: Shaping Community on Campus
Many American universities continue to invest in expensive intercollegiate football programs, and specifically cite the sport’s ability to foster a sense of community (SOC) as justification for the cost. This study sought to assess the importance of SOC and the influence of football on the cultivation thereof. A pre-post test design utilizing an online survey compared SOC levels for students (N = 886) before and after the implementation of Division I football on a large university campus. No significant differences were found in SOC levels before and after the football season (regardless of attendance). Post-test SOC perceptions differed based on game attendance (i.e., moderate and loyal attendees reported the highest levels). Finally, SOC had a moderate to strong positive influence on four outcome variables: Satisfaction, Retention, Current Support of Athletics, and Future Support for Athletics. This study suggests that while SOC is very important to students, at least in the short term the introduction of a football program does not foster a greater SOC for all students
Understanding the Predictability of Gesture Parameters from Speech and their Perceptual Importance
Gesture behavior is a natural part of human conversation. Much work has
focused on removing the need for tedious hand-animation to create embodied
conversational agents by designing speech-driven gesture generators. However,
these generators often work in a black-box manner, assuming a general
relationship between input speech and output motion. As their success remains
limited, we investigate in more detail how speech may relate to different
aspects of gesture motion. We determine a number of parameters characterizing
gesture, such as speed and gesture size, and explore their relationship to the
speech signal in a two-fold manner. First, we train multiple recurrent networks
to predict the gesture parameters from speech to understand how well gesture
attributes can be modeled from speech alone. We find that gesture parameters
can be partially predicted from speech, and some parameters, such as path
length, being predicted more accurately than others, like velocity. Second, we
design a perceptual study to assess the importance of each gesture parameter
for producing motion that people perceive as appropriate for the speech.
Results show that a degradation in any parameter was viewed negatively, but
some changes, such as hand shape, are more impactful than others. A video
summarization can be found at https://youtu.be/aw6-_5kmLjY.Comment: To be published in the Proceedings of the 20th ACM International
Conference on Intelligent Virtual Agents (IVA 20
The Football Factor: Shaping Community on Campus
Many American universities continue to invest in expensive intercollegiate football
programs, and specifically cite the sport’s ability to foster a sense of community (SOC) as justification for the cost. This study sought to assess the importance of SOC and the influence of football on the cultivation thereof. A pre-post test design utilizing an online survey compared SOC levels for students (N = 886) before and after the implementation of Division I football on a large university campus. No significant differences were found in SOC levels before and after the football season (regardless of attendance). Post-test SOC perceptions differed based on game attendance (i.e., moderate and loyal attendees reported the highest levels). Finally, SOC had a moderate to strong positive influence on four outcome variables: Satisfaction, Retention, Current Support of Athletics, and Future Support for Athletics. This study suggests that while SOC is very important to students, at least in the short term the introduction of a football program does not foster a greater SOC for all students
The Radio Signatures of the First Supernovae
Primordial stars are key to primeval structure formation as the first stellar
components of primeval galaxies, the sources of cosmic chemical enrichment and
likely cosmic reionization, and they possibly gave rise to the supermassive
black holes residing at the centres of galaxies today. While the direct
detection of individual Pop III stars will likely remain beyond reach for
decades to come, we show their supernova remnants may soon be detectable in the
radio. We calculate radio synchrotron signatures between 0.5 - 35 GHz from
hydrodynamical computations of the supernova remnants of Pop III stars in
minihaloes. We find that hypernovae yield the brightest systems, with observed
radio fluxes as high as 1 - 10 muJy. Less energetic Type II supernovae yield
remnants about a factor of 30 dimmer and pair-instability supernova remnants
are dimmer by a factor of more than 10,000. Because of the high gas densities
of the progenitor environments, synchrotron losses severely limit the maximum
emission frequencies, producing a distinctive peaked radio spectrum
distinguishable from normal galactic supernova remnant spectra. Hypernovae
radio remnants should be detectable by existing radio facilities like eVLA and
eMERLIN while Type II supernova remnants will require the Square Kilometre
Array. The number counts of hypernova remnants at z > 20 with fluxes above 1
muJy are expected to be one per hundred square degree field, increasing to a
few per square degree if they form down to z = 10. The detection of a z > 20
Type II supernova remnant brighter than 1 nJy would require a 100 - 200 square
degree field, although only a 1 - 2 square degree field for those forming down
to z = 10. Hypernova and Type II supernova remnants are easily separated from
one another by their light curves, which will enable future surveys to use them
to constrain the initial mass function of Pop III stars.Comment: 12 pages, 9 figures; major revision; to appear in MNRA
X-QUEST: A Comprehensive X-ray Study of Local ULIRGs and QSOs
We present results from the X-ray portion of a multi-wavelength study of
local ULIRGs and QSOs called QUEST (Quasar-ULIRG Evolution STudy). The data
consist of new and archival X-ray data on 40 ULIRGs and 26 PG QSOs taken with
Chandra and XMM-Newton. A combination of traditional and hardness ratio
spectral fitting methods is used to characterize the X-ray properties of these
objects. The absorption-corrected 2-10 keV to bolometric luminosity ratios of
the ULIRGs and PG QSOs suggest that the likelihood for dominant nuclear
activity increases along the merger sequence from "cool" ULIRGs, "warm" ULIRGs,
infrared-bright QSOs, and infrared-faint QSOs. The starburst dominates the
total power in ULIRGs prior to the merger, and this is followed by rapid black
hole growth during and after coalescence. These results are in general
agreement with those obtained in the mid-infrared with Spitzer and recent
numerical simulations.Comment: 63 pages preprint style including 16 figures and 11 tables; accepted
by Ap
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