2,530 research outputs found
Improving population-level refractive error monitoring via mixture distributions
Introduction: Sampling and describing the distribution of refractive error in populations is critical to understanding eye care needs, refractive differences between groups and factors affecting refractive development. We investigated the ability of mixture models to describe refractive error distributions. Methods: We used key informants to identify raw refractive error datasets and a systematic search strategy to identify published binned datasets of community-representative refractive error. Mixture models combine various component distributions via weighting to describe an observed distribution. We modelled raw refractive error data with a single-Gaussian (normal) distribution, mixtures of two to six Gaussian distributions and an additive model of an exponential and Gaussian (ex-Gaussian) distribution. We tested the relative fitting accuracy of each method via Bayesian Information Criterion (BIC) and then compared the ability of selected models to predict the observed prevalence of refractive error across a range of cut-points for both the raw and binned refractive data. Results: We obtained large raw refractive error datasets from the United States and Korea. The ability of our models to fit the data improved significantly from a single-Gaussian to a two-Gaussian-component additive model and then remained stable with ≥3-Gaussian-component mixture models. Means and standard deviations for BIC relative to 1 for the single-Gaussian model, where lower is better, were 0.89 ± 0.05, 0.88 ± 0.06, 0.89 ± 0.06, 0.89 ± 0.06 and 0.90 ± 0.06 for two-, three-, four-, five- and six-Gaussian-component models, respectively, tested across US and Korean raw data grouped by age decade. Means and standard deviations for the difference between observed and model-based estimates of refractive error prevalence across a range of cut-points for the raw data were −3.0% ± 6.3, 0.5% ± 1.9, 0.6% ± 1.5 and −1.8% ± 4.0 for one-, two- and three-Gaussian-component and ex-Gaussian models, respectively. Conclusions: Mixture models appear able to describe the population distribution of refractive error accurately, offering significant advantages over commonly quoted simple summary statistics such as mean, standard deviation and prevalence
Lidocaine Induces Endoplasmic Reticulum Stress-Associated Apoptosis in Vitro and in Vivo
We demonstrated that upregulation of both gene expression of endoplasmic reticulum (ER) stress chaperones (BiP, calnexin, calreticulin, and PDI) and ER stress sensors (ATF6, IRE1 and PERK) was induced by lidocaine, a local anesthetic, in PC12 cells. In addition to gene regulation, lidocaine also induced typical ER stress phenomena such as ART6 proteolytic cleavage, eIF2 alpha phosphorylation, and XBP1 mRNA splicing. In in vivo experiments, while lidocaine downregulated gene expression of antiapoptotic factors (Bcl-2 and Bcl-xl), pro-apoptotic factor (Bak and Bax) gene expression was upregulated. Furthermore, lidocaine induced apoptosis, as measured histochemically, and upregulated PARP1, a DNA damage repair enzyme. These results are the first to show that lidocaine induces apoptosis through ER stress in vitro and in vivo
Measurement of high-p_T Single Electrons from Heavy-Flavor Decays in p+p Collisions at sqrt(s) = 200 GeV
The momentum distribution of electrons from decays of heavy flavor (charm and
beauty) for midrapidity |y| < 0.35 in p+p collisions at sqrt(s) = 200 GeV has
been measured by the PHENIX experiment at the Relativistic Heavy Ion Collider
(RHIC) over the transverse momentum range 0.3 < p_T < 9 GeV/c. Two independent
methods have been used to determine the heavy flavor yields, and the results
are in good agreement with each other. A fixed-order-plus-next-to-leading-log
pQCD calculation agrees with the data within the theoretical and experimental
uncertainties, with the data/theory ratio of 1.72 +/- 0.02^stat +/- 0.19^sys
for 0.3 < p_T < 9 GeV/c. The total charm production cross section at this
energy has also been deduced to be sigma_(c c^bar) = 567 +/- 57^stat +/-
224^sys micro barns.Comment: 375 authors from 57 institutions, 6 pages, 3 figures. Submitted to
Physical Review Letters. Plain text data tables for the points plotted in
figures for this and previous PHENIX publications are (or will be) publicly
available at http://www.phenix.bnl.gov/papers.htm
High-pT pi^zero Production with Respect to the Reaction Plane in Au + Au Collisions at sqrt(s_NN) = 200 GeV
Measurements of the azimuthal anisotropy of high-\pT neutral pion neutral
pion production in Au+Au collisions at sqrt(s_NN) = 200 GeV by the PHENIX
experiment are presented. The data included in this paper were collected during
the 2004 RHIC running period and represent approximately an order of magnitude
increase in the number of analyzed events relative to previously published
results. Azimuthal angle distributions of pi^0s detected in the PHENIX
electromagnetic calorimeters are measured relative to the reaction plane
determined event-by-event using the forward and backward beam-beam counters.
Amplitudes of the second Fourier component (v_2) of the angular distributions
are presented as a function of pi^0 transverse momentum p_T for different bins
in collision centrality. Measured reaction plane dependent pi^0 yields are used
to determine the azimuthal dependence of the pi^0 suppression as a function of
p_T, R_AA (Delta phi,p_T). A jet-quenching motivated geometric analysis is
presented that attempts to simultaneously describe the centrality dependence
and reaction plane angle dependence of the pi^0 suppression in terms of the
path lengths of hypothetical parent partons in the medium. This set of results
allows for a detailed examination of the influence of geometry in the collision
region, and of the interplay between collective flow and jet-quenching effects
along the azimuthal axis.Comment: 344 authors, 35 pages text, RevTeX-4, 24 figures, 8 tables. Submitted
to Physical Review
Transverse-energy distributions at midrapidity in , Au, and AuAu collisions at --200~GeV and implications for particle-production models
Measurements of the midrapidity transverse energy distribution, d\Et/d\eta,
are presented for , Au, and AuAu collisions at
GeV and additionally for AuAu collisions at
and 130 GeV. The d\Et/d\eta distributions are first
compared with the number of nucleon participants , number of
binary collisions , and number of constituent-quark participants
calculated from a Glauber model based on the nuclear geometry. For
AuAu, \mean{d\Et/d\eta}/N_{\rm part} increases with , while
\mean{d\Et/d\eta}/N_{qp} is approximately constant for all three energies.
This indicates that the two component ansatz, , which has been used to represent
distributions, is simply a proxy for , and that the term
does not represent a hard-scattering component in distributions. The
distributions of AuAu and Au are then calculated from
the measured distribution using two models that both reproduce
the AuAu data. However, while the number-of-constituent-quark-participant
model agrees well with the Au data, the additive-quark model does not.Comment: 391 authors, 24 pages, 19 figures, and 15 Tables. Submitted to Phys.
Rev. C. Plain text data tables for the points plotted in figures for this and
previous PHENIX publications are publicly available at
http://www.phenix.bnl.gov/papers.htm
Identified charged hadron production in p+p collisions at sqrt(s)=200 and 62.4 GeV
Transverse momentum distributions and yields for , ,
and in collisions at =200 and 62.4 GeV at midrapidity
are measured by the PHENIX experiment at the Relativistic Heavy Ion Collider
(RHIC). These data provide important baseline spectra for comparisons with
identified particle spectra in heavy ion collisions at RHIC. We present the
inverse slope parameter , mean transverse momentum and
yield per unit rapidity at each energy, and compare them to other
measurements at different in and collisions. We
also present the scaling properties such as scaling, scaling on the
spectra between different energies. To discuss the mechanism of the
particle production in collisions, the measured spectra are compared to
next-to-leading-order or next-to-leading-logarithmic perturbative quantum
chromodynamics calculations.Comment: 431 authors from 62 institutions, 32 pages, 23 figures, and 18
tables. Submitted to Physical Review C. Plain text data tables for the points
plotted in figures for this and previous PHENIX publications are (or will be)
publicly available at http://www.phenix.bnl.gov/papers.htm
Cross section and double helicity asymmetry for eta mesons and their comparison to neutral pion production in p+p collisions at sqrt(s)=200 GeV
Measurements of double-helicity asymmetries for inclusive hadron production
in polarized p+p collisions are sensitive to helicity--dependent parton
distribution functions, in particular to the gluon helicity distribution,
Delta(g). This study focuses on the extraction of the double-helicity asymmetry
in eta production: polarized p+p --> eta + X, the eta cross section, and the
eta/pi^0 cross section ratio. The cross section and ratio measurements provide
essential input for the extraction of fragmentation functions that are needed
to access the helicity-dependent parton distribution functions.Comment: 432 authors from 62 institutions, 13 pages, 5 figures, and 3 tables.
Submitted to Physical Review D. v2 has minor changes only to update
references and reposition figures and tables. All data points plotted in
Figs. 2, 4, and 5 are given in Tables I, II, and III, respectivel
Deuteron and antideuteron production in Au+Au collisions at sqrt(s_NN)=200 GeV
The production of deuterons and antideuterons in the transverse momentum
range 1.1 < p_T < 4.3 GeV/c at mid-rapidity in Au + Au collisions at
sqrt(s_NN)=200 GeV has been studied by the PHENIX experiment at RHIC. A
coalescence analysis comparing the deuteron and antideuteron spectra with those
of protons and antiprotons, has been performed. The coalescence probability is
equal for both deuterons and antideuterons and increases as a function of p_T,
which is consistent with an expanding collision zone. Comparing (anti)proton
yields p_bar/p = 0.73 +/- 0.01, with (anti)deuteron yields: d_bar/d = 0.47 +/-
0.03, we estimate that n_bar/n = 0.64 +/- 0.04.Comment: 326 authors, 6 pages text, 5 figures, 1 Table. Submitted to PRL.
Plain text data tables for the points plotted in figures for this and
previous PHENIX publications are (or will be) publicly available at
http://www.phenix.bnl.gov/papers.htm
Quantitative Constraints on the Transport Properties of Hot Partonic Matter from Semi-Inclusive Single High Transverse Momentum Pion Suppression in Au+Au collisions at sqrt(s_NN) = 200 GeV
The PHENIX experiment has measured the suppression of semi-inclusive single
high transverse momentum pi^0's in Au+Au collisions at sqrt(s_NN) = 200 GeV.
The present understanding of this suppression is in terms of energy-loss of the
parent (fragmenting) parton in a dense color-charge medium. We have performed a
quantitative comparison between various parton energy-loss models and our
experimental data. The statistical point-to-point uncorrelated as well as
correlated systematic uncertainties are taken into account in the comparison.
We detail this methodology and the resulting constraint on the model
parameters, such as the initial color-charge density dN^g/dy, the medium
transport coefficient , or the initial energy-loss parameter epsilon_0.
We find that high transverse momentum pi^0 suppression in Au+Au collisions has
sufficient precision to constrain these model dependent parameters at the +/1
20%-25% (one standard deviation) level. These constraints include only the
experimental uncertainties, and further studies are needed to compute the
corresponding theoretical uncertainties.Comment: 422 authors, 13 pages text, RevTeX-4, 9 figures, 2 tables. This
version is updated with changes made during the review process and is now the
same as what was published in Physical Review C. Plain text data tables for
the points plotted in figures for this and previous PHENIX publications are
publicly available at http://www.phenix.bnl.gov/papers.htm
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