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When enough is not enough: information overload and metacognitive decisions to stop studying information
People are often exposed to more information than they can actually remember. Despite this frequent form of information overload, little is known about how much information people choose to remember. Using a novel âstopâ paradigm, the current research examined whether and how people choose to stop receiving newâpossibly overwhelmingâinformation with the intent to maximize memory performance. Participants were presented with a long list of items and were rewarded for the number of correctly remembered words in a following free recall test. Critically, participants in a stop condition were provided with the option to stop the presentation of the remaining words at any time during the list, whereas participants in a control condition were presented with all items. Across five experiments, we found that participants tended to stop the presentation of the items to maximize the number of recalled items, but this decision ironically led to decreased memory performance relative to the control group. This pattern was consistent even after controlling for possible confounding factors (e.g., task demands). The results indicated a general, false belief that we can remember a larger number of items if we restrict the quantity of learning materials. These findings suggest people have an incomplete understanding of how we remember excessive amounts of information
Testing Dark Energy with the Advanced Liquid-Mirror Probe of Asteroids, Cosmology and Astrophysics
The Advanced Liquid-Mirror Probe of Asteroids, Cosmology and Astrophysics
(ALPACA) is a proposed 8-meter liquid mirror telescope surveying 1000 square
degree of the southern-hemisphere sky. It will be a remarkably simple and
inexpensive telescope, that nonetheless will deliver a powerful sample of
optical data for studying dark energy. The bulk of the cosmological data
consists of nightly, high signal-to-noise, multiband light curves of SN Ia. At
the end of the three-years run ALPACA is expected to collect 100,000 SNe Ia up
to z~1. This will allow us to reduce present systematic uncertainties affecting
the standard-candle relation. The survey will also provide several other
datasets such as the detection of baryon acoustic oscillations in the matter
power spectrum and shear weak lensing measurements. In this preliminary
analysis we forecast constraints on dark energy parameters from SN Ia and
baryon acoustic oscillations. The combination of these two datasets will
provide competitive constraints on the dark energy parameters under minimal
prior assumptions. Further studies are needed to address the accuracy of weak
lensing measurements.Comment: 8 pages, 1 figure. Added extended discussion on SN Ia systematics,
matches MNRAS accepted versio
Clustering of Photometric Luminous Red Galaxies II: Cosmological Implications from the Baryon Acoustic Scale
A new determination of the sound horizon scale in angular coordinates is
presented. It makes use of ~ 0.6 x 10^6 Luminous Red Galaxies, selected from
the Sloan Digital Sky Survey imaging data, with photometric redshifts. The
analysis covers a redshift interval that goes from z=0.5 to z=0.6. We find
evidence of the Baryon Acoustic Oscillations (BAO) signal at the ~ 2.3 sigma
confidence level, with a value of theta_{BAO} (z=0.55) = (3.90 \pm 0.38)
degrees, including systematic errors. To our understanding, this is the first
direct measurement of the angular BAO scale in the galaxy distribution, and it
is in agreement with previous BAO measurements. We also show how radial
determinations of the BAO scale can break the degeneracy in the measurement of
cosmological parameters when they are combined with BAO angular measurements.
The result is also in good agreement with the WMAP7 best-fit cosmology. We
obtain a value of w_0 = -1.03 \pm 0.16 for the equation of state parameter of
the dark energy, Omega_M = 0.26 \pm 0.04 for the matter density, when the other
parameters are fixed. We have also tested the sensitivity of current BAO
measurements to a time varying dark energy equation of state, finding w_a =
0.06 \pm 0.22 if we fix all the other parameters to the WMAP7 best-fit
cosmology.Comment: 7 pages, 7 figures, Accepted for publication to MNRA
Distance, Growth Factor, and Dark Energy Constraints from Photometric Baryon Acoustic Oscillation and Weak Lensing Measurements
Baryon acoustic oscillations (BAOs) and weak lensing (WL) are complementary
probes of cosmology. We explore the distance and growth factor measurements
from photometric BAO and WL techniques and investigate the roles of the
distance and growth factor in constraining dark energy. We find for WL that the
growth factor has a great impact on dark energy constraints but is much less
powerful than the distance. Dark energy constraints from WL are concentrated in
considerably fewer distance eigenmodes than those from BAO, with the largest
contributions from modes that are sensitive to the absolute distance. Both
techniques have some well determined distance eigenmodes that are not very
sensitive to the dark energy equation of state parameters w_0 and w_a,
suggesting that they can accommodate additional parameters for dark energy and
for the control of systematic uncertainties. A joint analysis of BAO and WL is
far more powerful than either technique alone, and the resulting constraints on
the distance and growth factor will be useful for distinguishing dark energy
and modified gravity models. The Large Synoptic Survey Telescope (LSST) will
yield both WL and angular BAO over a sample of several billion galaxies. Joint
LSST BAO and WL can yield 0.5% level precision on ten comoving distances evenly
spaced in log(1+z) between redshift 0.3 and 3 with cosmic microwave background
priors from Planck. In addition, since the angular diameter distance, which
directly affects the observables, is linked to the comoving distance solely by
the curvature radius in the Friedmann-Robertson-Walker metric solution, LSST
can achieve a pure metric constraint of 0.017 on the mean curvature parameter
Omega_k of the universe simultaneously with the constraints on the comoving
distances.Comment: 15 pages, 9 figures, details and references added, ApJ accepte
Non-linear Galaxy Power Spectrum and Cosmological Parameters
The galaxy power spectrum is now a well-known tool of precision cosmology. In
addition to the overall shape, baryon oscillations and the small-scale
suppression of power by massive neutrinos capture complimentary information on
cosmological parameters when compared to the angular power spectrum of cosmic
microwave background anisotropies. We study both the real space and redshift
space galaxy power spectra in the context of non-linear effects and model them
based on the halo approach to large scale structure clustering. We consider
potential systematic in the cosmological parameter determination when
non-linear effects are ignored and the galaxy power spectrum is described with
the linear power spectrum scaled by a constant bias factor. We suggest that
significant improvements can be made when non-linear effects are taken into
account as a power-law contribution with two additional parameters to be
determined from the data. In addition to cosmological parameters through galaxy
clustering, such an approach allow a determination of useful information
related to astrophysics on how galaxies occupy dark matter halos.Comment: 14 pages, 6 figures; MNRAS in pres
Mock galaxy redshift catalogues from simulations: implications for Pan-STARRS1
We describe a method for constructing mock galaxy catalogues which are well
suited for use in conjunction with large photometric surveys. We use the
semi-analytic galaxy formation model of Bower et al. implemented in the
Millennium simulation. We apply our method to the specific case of the surveys
soon to commence with PS1, the first of 4 telescopes planned for the Pan-STARRS
system. PS1 has 5 photometric bands (grizy), and will carry out an all-sky 3pi
survey and a medium deep survey (MDS) over 84 sq.deg. We calculate the expected
magnitude limits for extended sources in the two surveys. We find that, after 3
years, the 3pi survey will have detected over 10^8 galaxies in all 5 bands, 10
million of which will lie at redshift z>0.9, while the MDS will have detected
over 10^7 galaxies with 0.5 million lying at z>2. These numbers at least double
if detection in the shallowest band, y is not required. We then evaluate the
accuracy of photometric redshifts estimated using an off-the-shelf photo-z
code. With the grizy bands alone it is possible to achieve an accuracy in the
3pi survey of Delta z/(1+z)~0.06 for 0.25<z<0.8, which could be reduced by
about 15% using near infrared photometry from the UKIDDS survey, but would
increase by about 25% for the deeper sample without the y band photometry. For
the MDS an accuracy of Delta z/(1+z)~0.05 is achievable for 0.02<z<1.5 using
grizy. A dramatic improvement in accuracy is possible by selecting only red
galaxies. In this case, Delta z/(1+z)~0.02-0.04 is achievable for ~100 million
galaxies at 0.4<z<1.1 in the 3pi survey and for 30 million galaxies in the MDS
at 0.4<z<2. We investigate the effect of using photo-z in the estimate of the
baryonic acoustic oscillation scale. We find that PS1 will achieve a similar
accuracy in this estimate as a spectroscopic survey of 20 million galaxies.Comment: 23 pages, 18 figures, accepted by MNRA
Stable stochastic dynamics in yeast cell cycle
Chemical reactions in cell are subject to intense stochastic fluctuations. An
important question is how the fundamental physiological behavior of cell is
kept stable against those noisy perturbations. In this paper a stochastic model
of cell cycle of budding yeast is constructed to analyze the effects of noise
on the cell cycle oscillation. The model predicts intense noise in levels of
mRNAs and proteins, and the simulated protein levels explain the observed
statistical tendency of noise in populations of synchronous and asynchronous
cells. In spite of intense noise in levels of proteins and mRNAs, cell cycle is
stable enough to bring the largely perturbed cells back to the physiological
cyclic oscillation. The model shows that consecutively appearing fixed points
are the origin of this stability of cell cycle.Comment: main text, 2 supporting texts, 3 supplementary table
Lessons Learned During the Implementation of a Cold Gas Propulsion System for the SunRISE Mission
The SunRISE mission utilizes a two-phase cold gas propulsion system, which provides several advantages over other cold gas systems but experienced challenges during assembly and testing. Since 2020, Georgia Tech Research Corporation (GTRC), Utah State University Space Dynamics Laboratory (SDL), and the Jet Propulsion Laboratory (FPL) have implemented several improvements to the SunRISE propulsion system.
The SunRISE propulsion system leverages an additively manufactured monolithic structure, commercial off-the-shelf (COTS) valves and transducers, and the benign working fluid R-236fa to provide a suitable propulsion system for the SunRise mission. While the GTRC propulsion system had been developed for other missions, the multi-organizational team found and corrected several previously undetected design issues, including filters with highly variable flow performance, solenoid valve drive circuit issues, and inconsistencies in the tank additive manufacturing process that impacted manufacturing yield, thrust consistency, and quality of seals. Leaks in metallic fittings were also identified, and process improvements were put in place to mitigate them. Solenoid valve stiction was the last issue which was mitigated through valve screening and drive circuit adjustments. In this paper, we present lessons learned from the SunRISE propulsion system effort to aid future teams in identifying and addressing similar issues
The role of mergers in driving morphological transformation over cosmic time
Accepted for publication in MNRASUnderstanding the processes that trigger morphological transformation is central to understanding how and why the Universe transitions from being disc-dominated at early epochs to having the morphological mix that is observed today. We use Horizon-AGN, a cosmological hydrodynamical simulation, to perform a comprehensive study of the processes that drive morphological change in massive (M*/M â > 10 10) galaxies over cosmic time. We show that (1) essentially all the morphological evolution in galaxies that are spheroids at z = 0 is driven by mergers with mass ratios greater than 1: 10; (2) major mergers alone cannot produce today's spheroid population - minor mergers are responsible for a third of all morphological transformation over cosmic time and are its dominant driver after z ~ 1; (3) prograde mergers trigger milder morphological transformation than retrograde mergers - while both types of event produce similar morphological changes at z > 2, the average change due to retrograde mergers is around twice that due to their prograde counterparts at z ~ 0; (4) remnant morphology depends strongly on the gas fraction of a merger, with gas-rich mergers routinely re-growing discs; and (5) at a given stellar mass, discs do not exhibit drastically different merger histories from spheroids - disc survival in mergers is driven by acquisition of cold gas (via cosmological accretion and gas-rich interactions) and a preponderance of prograde mergers in their merger histories.Peer reviewedFinal Accepted Versio
Reconstructing the history of dark energy using maximum entropy
We present a Bayesian technique based on a maximum-entropy method to reconstruct the dark energy equation of state (EOS) w(z) in a non-parametric way. This Maximum Entropy (MaxEnt) technique allows to incorporate relevant prior information while adjusting the degree of smoothing of the reconstruction in response to the structure present in the data. After demonstrating the method on synthetic data, we apply it to current cosmological data, separately analysing Type Ia supernova measurement from the HST/GOODS programme and the first-year Supernovae Legacy Survey (SNLS), complemented by cosmic microwave background and baryonic acoustic oscillation data. We find that the SNLS data are compatible with w(z) = -1 at all redshifts 0 64 z 72 1100, with error bars of the order of 20 per cent for the most-constraining choice of priors. The HST/GOODS data exhibit a slight (about 1\u3c3 significance) preference for w > -1 at z 3c 0.5 and a drift towards w > -1 at larger redshifts which, however, is not robust with respect to changes in our prior specifications. We employ both a constant EOS prior model and a slowly varying w(z) and find that our conclusions are only mildly dependent on this choice at high redshifts. Our method highlights the danger of employing parametric fits for the unknown EOS, that can potentially miss or underestimate real structure in the data. \ua9 2007 RAS
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