40 research outputs found
Cosmological test using the high-redshift detection rate of FSRQs with the Square Kilometer Array
We present a phenomenological method for predicting the number of Flat
Spectrum Radio Quasars (FSRQs) that should be detected by upcoming Square
Kilometer Array (SKA) SKA1-MID Wide Band 1 and Medium-Deep band 2 surveys. We
use the Fermi Blazar Sequence and mass estimates of Fermi FSRQs, and gamma-ray
emitting Narrow Line Seyfert 1 galaxies, to model the radio emission of FSRQs
as a function of mass alone, assuming a near-Eddington accretion rate, which is
suggested by current quasar surveys at z > 6. This is used to determine the
smallest visible black hole mass as a function of redshift in two competing
cosmologies we compare in this paper: the standard LCDM model and the R_h=ct
universe. We then apply lockstep growth to the observed black-hole mass
function at in order to devolve that population to higher redshifts and
determine the number of FSRQs detectable by the SKA surveys as a function of z.
We find that at the redshifts for which this method is most valid, LCDM
predicts ~30 times more FSRQs than R_h=ct for the Wide survey, and ~100 times
more in the Medium-Deep survey. These stark differences will allow the SKA
surveys to strongly differentiate between these two models, possibly rejecting
one in comparison with the other at a high level of confidence.Comment: 8 pages, 5 figures, 3 tables. Accepted for publication in MNRA
A Two-point Diagnostic for the HII Galaxy Hubble Diagram
A previous analysis of starburst-dominated HII Galaxies and HII regions has
demonstrated a statistically significant preference for the
Friedmann-Robertson-Walker cosmology with zero active mass, known as the R_h=ct
universe, over LCDM and its related dark-matter parametrizations. In this
paper, we employ a 2-point diagnostic with these data to present a
complementary statistical comparison of R_h=ct with Planck LCDM. Our 2-point
diagnostic compares---in a pairwise fashion---the difference between the
distance modulus measured at two redshifts with that predicted by each
cosmology. Our results support the conclusion drawn by a previous comparative
analysis demonstrating that R_h=ct is statistically preferred over Planck LCDM.
But we also find that the reported errors in the HII measurements may not be
purely Gaussian, perhaps due to a partial contamination by non-Gaussian
systematic effects. The use of HII Galaxies and HII regions as standard candles
may be improved even further with a better handling of the systematics in these
sources.Comment: 7 pages, 6 figures, 2 tables. Accepted for publication in MNRA
Analyzing H(z) Data using Two-point Diagnostics
Measurements of the Hubble constant H(z) are increasingly being used to test
the expansion rate predicted by various cosmological models. But the recent
application of 2-point diagnostics, such as Om(z_i,z_j) and Omh^2(z_i,z_j), has
produced considerable tension between LCDM's predictions and several
observations, with other models faring even worse. Part of this problem is
attributable to the continued mixing of truly model-independent measurements
using the cosmic-chronomter approach, and model-dependent data extracted from
BAOs. In this paper, we advance the use of 2-point diagnostics beyond their
current status, and introduce new variations, which we call Delta h(z_i,z_j),
that are more useful for model comparisons. But we restrict our analysis
exclusively to cosmic-chronometer data, which are truly model independent. Even
for these measurements, however, we confirm the conclusions drawn by earlier
workers that the data have strongly non-Gaussian uncertainties, requiring the
use of both "median" and "mean" statistical approaches. Our results reveal that
previous analyses using 2-point diagnostics greatly underestimated the errors,
thereby misinterpreting the level of tension between theoretical predictions
and H(z) data. Instead, we demonstrate that as of today, only Einstein-de
Sitter is ruled out by the 2-point diagnostics at a level of significance
exceeding ~ 3 sigma. The R_h=ct universe is slightly favoured over the
remaining models, including LCDM and Chevalier-Polarski-Linder, though all of
them (other than Einstein-de Sitter) are consistent to within 1 sigma with the
measured mean of the Delta h(z_i,z_j) diagnostics.Comment: 17 pages, 6 figures. Accepted for publication in MNRA
Model Selection with Strong-lensing Systems
In this paper, we use an unprecedentedly large sample (158) of confirmed
strong lens systems for model selection, comparing five well studied
Friedmann-Robertson-Walker cosmologies: LCDM, wCDM (the standard model with a
variable dark-energy equation of state), the R_h=ct universe, the (empty) Milne
cosmology, and the classical Einstein-de Sitter (matter dominated) universe. We
first use these sources to optimize the parameters in the standard model and
show that they are consistent with Planck, though the quality of the best fit
is not satisfactory. We demonstrate that this is likely due to under-reported
errors, or to errors yet to be included in this kind of analysis. We suggest
that the missing dispersion may be due to scatter about a pure single
isothermal sphere (SIS) model that is often assumed for the mass distribution
in these lenses. We then use the Bayes information criterion, with the
inclusion of a suggested SIS dispersion, to calculate the relative likelihoods
and ranking of these models, showing that Milne and Einstein-de Sitter are
completely ruled out, while R_h=ct is preferred over LCDM/wCDM with a relative
probability of ~73% versus ~24%. The recently reported sample of new strong
lens candidates by the Dark Energy Survey, if confirmed, may be able to
demonstrate which of these two models is favoured over the other at a level
exceeding 3 sigma.Comment: 19 pages, 2 figures, 2 tables. Accepted for publication in MNRA
UNLV College of Education Multicultural & Diversity Newsletter
Each morning I wound my way up the steep hill along the deeply rutted dirt path, exchanging daily maaa\u27s with five bleating sheep and shouting out, ÂĄHola! in response to the children who gleefully identified me as ÂĄGringa! Women and children, colorful bowls of cooked maize balanced atop their heads, sauntered to and from Maria Elena\u27s where their maize would be ground; at home the dough would be shaped and flattened into tortillas, the mainstay of every meal in the small Guatemalan village of San Juan
UNLV College of Education Multicultural & Diversity Newsletter
The workshop sponsored by the College of Education Multicultural & Diversity Committee on Friday January 16, 1998 was attended by approximately 40 faculty members and students from the College of Education. Dr. Gary Howard from the REACH Center (Respecting Ethnic And Cultural Heritage) located in Seattle, Washington provided an excellent three-hour workshop that asked attendees to ponder various dimensions of multicultural and global education. Dr. Howard provided information designed to facilitate the development of positive leadership skills for the implementation of cultural awareness and valuing diversity strategies in the classes in which the attendees teach---whether that be at a university or in a school distric
Proceedings from the Ice Hockey Summit III: Action on Concussion
The Ice Hockey Summit III provided updated scientific evidence on concussions in hockey to inform these five objectives: 1) describe sport-related concussion (SRC) epidemiology, 2) classify prevention strategies, 3) define objective, diagnostic tests, 4) identify treatment, and 5) integrate science and clinical care into prioritized action plans and policy. Our action plan evolved from 40 scientific presentations. The 155 attendees (physicians, athletic trainers, physical therapists, nurses, neuropsychologists, scientists, engineers, coaches, and officials) voted to prioritize these action items in the final Summit session. 1) Establish a national and international hockey data base for SRC at all levels, 2) eliminate body checking in Bantam youth hockey games, 3) expand a behavior modification program (Fair Play) to all youth hockey levels, 4) enforce game ejection penalties for fighting in Junior A and professional hockey leagues, 5) establish objective tests to diagnose concussion at point of care (POC), and 6) mandate baseline testing to improve concussion diagnosis for all age groups. Expedient implementation of the Summit III prioritized action items is necessary to reduce the risk, severity, and consequences of concussion in the sport of ice hockey
Proceedings from the Ice Hockey Summit III: Action on Concussion
Objectives The Ice Hockey Summit III provided updated scientific evidence on concussions in hockey to inform these five objectives: (1) describe sport related concussion (SRC) epidemiology, (2) classify prevention strategies, (3) define objective, diagnostic tests, (4) identify treatment and (5) integrate science and clinical care into prioritized action plans and policy. Methods Our action plan evolved from 40 scientific presentations. The 155 attendees (physicians, athletic trainers, physical therapists, nurses, neuropsychologists, scientists, engineers, coaches and officials) voted to prioritize these action items in the final Summit session. Results (1) establish a national and international hockey data base for SRCs at all levels; (2) eliminate body checking in Bantam youth hockey games; (3) expand a behavior modification program (Fair Play) to all youth hockey levels; (4) enforce game ejection penalties for fighting in Junior A and professional hockey leagues; (5) establish objective tests to diagnose concussion at point of care (POC); and (6) mandate baseline testing to improve concussion diagnosis for all age groups. Conclusions Expedient implementation of the Summit III prioritized action items is necessary to reduce the risk, severity and consequences of concussion in the sport of ice hockey
Effect of angiotensin-converting enzyme inhibitor and angiotensin receptor blocker initiation on organ support-free days in patients hospitalized with COVID-19
IMPORTANCE Overactivation of the renin-angiotensin system (RAS) may contribute to poor clinical outcomes in patients with COVID-19.
Objective To determine whether angiotensin-converting enzyme (ACE) inhibitor or angiotensin receptor blocker (ARB) initiation improves outcomes in patients hospitalized for COVID-19.
DESIGN, SETTING, AND PARTICIPANTS In an ongoing, adaptive platform randomized clinical trial, 721 critically ill and 58 nonâcritically ill hospitalized adults were randomized to receive an RAS inhibitor or control between March 16, 2021, and February 25, 2022, at 69 sites in 7 countries (final follow-up on June 1, 2022).
INTERVENTIONS Patients were randomized to receive open-label initiation of an ACE inhibitor (nâ=â257), ARB (nâ=â248), ARB in combination with DMX-200 (a chemokine receptor-2 inhibitor; nâ=â10), or no RAS inhibitor (control; nâ=â264) for up to 10 days.
MAIN OUTCOMES AND MEASURES The primary outcome was organ supportâfree days, a composite of hospital survival and days alive without cardiovascular or respiratory organ support through 21 days. The primary analysis was a bayesian cumulative logistic model. Odds ratios (ORs) greater than 1 represent improved outcomes.
RESULTS On February 25, 2022, enrollment was discontinued due to safety concerns. Among 679 critically ill patients with available primary outcome data, the median age was 56 years and 239 participants (35.2%) were women. Median (IQR) organ supportâfree days among critically ill patients was 10 (â1 to 16) in the ACE inhibitor group (nâ=â231), 8 (â1 to 17) in the ARB group (nâ=â217), and 12 (0 to 17) in the control group (nâ=â231) (median adjusted odds ratios of 0.77 [95% bayesian credible interval, 0.58-1.06] for improvement for ACE inhibitor and 0.76 [95% credible interval, 0.56-1.05] for ARB compared with control). The posterior probabilities that ACE inhibitors and ARBs worsened organ supportâfree days compared with control were 94.9% and 95.4%, respectively. Hospital survival occurred in 166 of 231 critically ill participants (71.9%) in the ACE inhibitor group, 152 of 217 (70.0%) in the ARB group, and 182 of 231 (78.8%) in the control group (posterior probabilities that ACE inhibitor and ARB worsened hospital survival compared with control were 95.3% and 98.1%, respectively).
CONCLUSIONS AND RELEVANCE In this trial, among critically ill adults with COVID-19, initiation of an ACE inhibitor or ARB did not improve, and likely worsened, clinical outcomes.
TRIAL REGISTRATION ClinicalTrials.gov Identifier: NCT0273570
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Observational and Theoretical Cosmology with Novel Statistical Methods
The standard ÎCDM model of the universe has been shown to be consistent with a wide range of astronomical observations, including many properties of the cosmic microwave background (CMB). However, the model has significant tension with an increasing set of measurements, ranging from determinations of the Hubble Constant to the angular correlation function of the CMB. This motivates revisions to ÎCDM, or the consideration of alternative models (or even entirely new physics). The Rh=ct universe is an alternative FLRW cosmology that has thus far performed very well in describing a wide range of astronomical observations. In this dissertation, I present a sequence of tests of cosmology. These tests are designed to determine whether the Rh=ct universe performs better than the standard model in accounting for the considered data. First, I show the development of a two-point diagnostic to compare a modelâs predictions with observations. This diagnostic is applied to passively evolving elliptical galaxies (cosmic chronometers) and the Hubble diagram as constructed using HII galaxies. Second, I make use of relative likelihoods with strongly-lensed galaxies to constrain standard ÎCDM and an alternative dark matter parameterization (wCDM). These model fits are then compared with the Rh=ct universe by means of several information criteria. Each of the direct comparisons using existing data favor the Rh=ct universe over standard ÎCDM to different degrees, warranting further research to determine whether it accurately describes the Universe. Finally, I present a theoretical prediction of the number of z>6 blazars that will be detectable by upcoming surveys by the Square Kilometer Array (SKA). This prediction is entirely phenomenological, based on spectral energy distribution (SED) measurements of known blazars. The predictions for the number of blazars detectable by SKA between these models are incompatible, such that either the Rh=ct universe or ÎCDM will be strongly preferred by the surveys