166 research outputs found
Growth Index of DGP Model and Current Growth Rate Data
Recently, some efforts focus on differentiating dark energy and modified
gravity with the growth function . In the literature, it is useful
to parameterize the growth rate
with the growth index . In this note, we consider the general DGP model
with any . We confront the growth index of DGP model with currently
available growth rate data and find that the DGP model is still consistent with
it. This implies that more and better growth rate data are required to
distinguish between dark energy and modified gravity.Comment: 12 pages, 1 table, 2 figures, Latex2e; v2: discussions added, Phys.
Lett. B in press; v3: published versio
Physician Executive Leadership: Student-Led Curriculum to Fill Gaps in Traditional Medical Education
Students at Sidney Kimmel Medical College (SKMC) have identified a gap in the traditional medical curriculum surrounding topics such as telehealth, the patient experience, health policy, medical malpractice, and health care entrepreneurship and innovation, and in response have initiated a student-centered, student-led, student-driven program called Physician Executive Leadership (PEL). PEL provides students with a variety of avenues to engage with these topics, such as lectures from leaders in each of these fields, easy access to weekly news articles on current events in health care, targeted review sessions on the US health care system, and the opportunity to voice and develop ideas through an online publication.
To identify the gaps in medical education PEL is best suited to fill, we administered a survey to 174 students at Sidney Kimmel Medical College.The survey contained 20 multiple-choice questions to assess general knowledge on health insurance and reimbursement, health care policy and reform, and care quality and patient experience. It also included a subjective self-assessment of studentsâ understanding of and interest in these topics. Overall, we found that although the traditional medical school curriculum improved students\u27 understanding of these topics from year to year, it is not sufficient on it\u27s own: on average, students failed to achieve a passing score of 70% in any of the categories tested. Further illustrating the importance of this program, students self-identified a gap between their current level of understanding and what they want to know.
Please visit our website www.physicianexecutiveleadership.com to learn more!https://jdc.jefferson.edu/pel/1000/thumbnail.jp
Effects of Three Modest Levels of Proximal Loading on Marathon Pace Running Economy
International Journal of Exercise Science 13(7): 1120-1131, 2020. This study examined the effect of modest increases in proximal body mass on running economy expressed as metabolic cost (MC). External loads of 1.6 (L), 2.4 (M), and 3.2 kg (H) were added to the anterior and posterior torso region of male (n = 18) and female (n = 18) runners using a double-layered compression garment with gel inserts. MC was evaluated using stoichiometry equations of data collected via indirect calorimetry. Data was collected during four, 5-min running bouts at marathon pace for the 3 load levels and an unloaded state (CON). When data from both sexes were combined, MC for CON (13.2 ± 2.7) was lower (p \u3c 0.05) versus L (13.5 ± 2.6), M (13.6 ± 2.6), and H (13.7 ± 2.6 kcal/min), but L did not differ from CON when data was analyzed for each sex. Male runners exhibited stepped increases in MC across loads and a weak-moderate relationship (r = 0.37; p \u3c 0.01) between percentage change in absolute MC and increased percent body mass. A prediction model for MC (â% kcal/min = 0.98(â% body mass) â 0.91; SEE = ± 2.5%) was developed. For female runners, L increased MC by ~3.5% above CON, but no differentiation was found among L, M, and H, limiting the development of a prediction equation for females. Modest increases in body mass can produce detectable and potentially important levels of running economy impairment, but the relationship between changes in body mass and RE are complex, particularly in regards to sex
The WiggleZ Dark Energy Survey: the growth rate of cosmic structure since redshift z=0.9
We present precise measurements of the growth rate of cosmic structure for
the redshift range 0.1 < z < 0.9, using redshift-space distortions in the
galaxy power spectrum of the WiggleZ Dark Energy Survey. Our results, which
have a precision of around 10% in four independent redshift bins, are well-fit
by a flat LCDM cosmological model with matter density parameter Omega_m = 0.27.
Our analysis hence indicates that this model provides a self-consistent
description of the growth of cosmic structure through large-scale perturbations
and the homogeneous cosmic expansion mapped by supernovae and baryon acoustic
oscillations. We achieve robust results by systematically comparing our data
with several different models of the quasi-linear growth of structure including
empirical models, fitting formulae calibrated to N-body simulations, and
perturbation theory techniques. We extract the first measurements of the power
spectrum of the velocity divergence field, P_vv(k), as a function of redshift
(under the assumption that P_gv(k) = -sqrt[P_gg(k) P_vv(k)] where g is the
galaxy overdensity field), and demonstrate that the WiggleZ galaxy-mass
cross-correlation is consistent with a deterministic (rather than stochastic)
scale-independent bias model for WiggleZ galaxies for scales k < 0.3 h/Mpc.
Measurements of the cosmic growth rate from the WiggleZ Survey and other
current and future observations offer a powerful test of the physical nature of
dark energy that is complementary to distance-redshift measures such as
supernovae and baryon acoustic oscillations.Comment: 17 pages, 11 figures, accepted for publication by MNRA
Probing the nature of cosmic acceleration
The cosmic acceleration is one of the most significant cosmological
discoveries over the last century. The two categories of explanation are exotic
component (dark energy) and modified gravity. We constrain the two types of
model by a joint analysis with perturbation growth and direct data.
Though the minimal of the CDM is almost the same as that of
DGP, in the sense of consistency we find that the dark energy (CDM)
model is more favored through a detailed comparison with the corresponding
parameters fitted by expansion data.Comment: 10 pages, 6 figures, typo correcte
Growth factor and galaxy bias from future redshift surveys: a study on parametrizations
Many experiments in the near future will test dark energy through its effects
on the linear growth of matter perturbations. In this paper we discuss the
constraints that future large-scale redshift surveys can put on three different
parameterizations of the linear growth factor and how these constraints will
help ruling out different classes of dark energy and modified gravity models.
We show that a scale-independent bias can be estimated to a few percent per
redshift slice by combining redshift distortions with power spectrum amplitude,
without the need of an external estimation. We find that the growth rate can be
constrained to within 2-4% for each redshift slice, while the
equation of state and the index can be simultaneously estimated
both to within 0.02. We also find that a constant dimensionless coupling
between dark energy and dark matter can be constrained to be smaller than 0.14.Comment: 22 pages, 11 figure
QCD ghost f(T)-gravity model
Within the framework of modified teleparallel gravity, we reconstruct a f(T)
model corresponding to the QCD ghost dark energy scenario. For a spatially flat
FRW universe containing only the pressureless matter, we obtain the time
evolution of the torsion scalar T (or the Hubble parameter). Then, we calculate
the effective torsion equation of state parameter of the QCD ghost f(T)-gravity
model as well as the deceleration parameter of the universe. Furthermore, we
fit the model parameters by using the latest observational data including
SNeIa, CMB and BAO data. We also check the viability of our model using a
cosmographic analysis approach. Moreover, we investigate the validity of the
generalized second law (GSL) of gravitational thermodynamics for our model.
Finally, we point out the growth rate of matter density perturbation. We
conclude that in QCD ghost f(T)-gravity model, the universe begins a matter
dominated phase and approaches a de Sitter regime at late times, as expected.
Also this model is consistent with current data, passes the cosmographic test,
satisfies the GSL and fits the data of the growth factor well as the LCDM
model.Comment: 19 pages, 9 figures, 2 tables. arXiv admin note: substantial text
overlap with arXiv:1111.726
Advanced Preparation Makes Research in Emergencies and Isolation Care Possible: The Case of Novel Coronavirus Disease (COVID-19)
The optimal time to initiate research on emergencies is before they occur. However, timely initiation of high-quality research may launch during an emergency under the right conditions. These include an appropriate context, clarity in scientific aims, preexisting resources, strong operational and research structures that are facile, and good governance. Here, Nebraskan rapid research efforts early during the 2020 coronavirus disease pandemic, while participating in the first use of U.S. federal quarantine in 50 years, are described from these aspects, as the global experience with this severe emerging infection grew apace. The experience has lessons in purpose, structure, function, and performance of research in any emergency, when facing any threat
Dynamics and constraints of the dissipative Liouville cosmology
In this article we investigate the properties of the FLRW flat cosmological
models in which the cosmic expansion of the Universe is affected by a dilaton
dark energy (Liouville scenario). In particular, we perform a detailed study of
these models in the light of the latest cosmological data, which serves to
illustrate the phenomenological viability of the new dark energy paradigm as a
serious alternative to the traditional scalar field approaches. By performing a
joint likelihood analysis of the recent supernovae type Ia data (SNIa), the
differential ages of passively evolving galaxies, and the Baryonic Acoustic
Oscillations (BAOs) traced by the Sloan Digital Sky Survey (SDSS), we put tight
constraints on the main cosmological parameters. Furthermore, we study the
linear matter fluctuation field of the above Liouville cosmological models. In
this framework, we compare the observed growth rate of clustering measured with
those predicted by the current Liouville models. Performing a chi^2 statistical
test we show that the Liouville cosmological model provides growth rates that
match sufficiently well with the observed growth rate. To further test the
viability of the models under study, we use the Press-Schechter formalism to
derive their expected redshift distribution of cluster-size halos that will be
provided by future X-ray and Sunyaev-Zeldovich cluster surveys. We find that
the Hubble flow differences between the Liouville and the LambdaCDM models
provide a significantly different halo redshift distribution, suggesting that
the models can be observationally distinguished.Comment: 15 pages, 4 figures, 4 tables, matches version to appear in
Astroparticle Physic
Prevalence of Type 1 and Type 2 Diabetes Among Children and Adolescents From 2001 to 2009
Despite concern about an âepidemic,â there are limited data on trends in prevalence of either type 1 or type 2 diabetes across US race and ethnic groups
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