11 research outputs found
Predictors of web-based follow-up response in the Prevention of Low Back Pain in the Military Trial (POLM)
<p>Abstract</p> <p>Background</p> <p>Achieving adequate follow-up in clinical trials is essential to establish the validity of the findings. Achieving adequate response rates reduces bias and increases probability that the findings can be generalized to the population of interest. Therefore, the purpose of this study was to determine the influence of attention, demographic, psychological, and health status factors on web-based response rates in the ongoing Prevention of Low Back Pain in the Military (POLM) trial.</p> <p>Methods</p> <p>Twenty companies of Soldiers (n = 4,325) were cluster randomized to complete a traditional exercise program including sit-ups (TEP) with or without a psychosocial educational program (PSEP) or a core stabilization exercise program (CSEP) with or without PSEP. A subgroup of Soldiers (n = 371) was randomized to receive an additional physical and ultrasound imaging (USI) examination of key trunk musculature. As part of the surveillance program, all Soldiers were encouraged to complete monthly surveys via email during the first year. Descriptive statistics of the predictor variables were obtained and compared between responders and non-responders using two sample t-tests or chi-square test, as appropriate. Generalized linear mixed models were subsequently fitted for the dichotomous outcomes to estimate the effects of the predictor variables. The significance level was set at .05 a priori.</p> <p>Results</p> <p>The overall response rate was 18.9% (811 subjects) for the first year. Responders were more likely to be older, Caucasian, have higher levels of education and income, reservist military status, non smoker, lower BMI, and have received individualized attention via the physical/USI examination (p < .05). Age, race/ethnicity, education, military status, smoking history, BMI, and whether a Soldier received the physical/USI examination remained statistically significant (p < .05) when considered in a full multivariate model.</p> <p>Conclusion</p> <p>The overall web based response rate during the first year of the POLM trial was consistent with studies that used similar methodology, but lower when compared to rates expected for standard clinical trials. One year response rate was significantly associated with demographic characteristics, health status, and individualized attention via additional testing. These data may assist for planning of future trials that use web based response systems.</p> <p>Trial Registration</p> <p>This study has been registered at reports at <url>http://clinicaltrials.gov</url> (<a href="http://www.clinicaltrials.gov/ct2/show/NCT00373009">NCT00373009</a>).</p
Direct Optimal Mapping for 21cm Cosmology: A Demonstration with the Hydrogen Epoch of Reionization Array
Motivated by the desire for wide-field images with well-defined statistical
properties for 21cm cosmology, we implement an optimal mapping pipeline that
computes a maximum likelihood estimator for the sky using the interferometric
measurement equation. We demonstrate this direct optimal mapping with data from
the Hydrogen Epoch of Reionization (HERA) Phase I observations. After
validating the pipeline with simulated data, we develop a maximum likelihood
figure-of-merit for comparing four sky models at 166MHz with a bandwidth of
100kHz. The HERA data agree with the GLEAM catalogs to <10%. After subtracting
the GLEAM point sources, the HERA data discriminate between the different
continuum sky models, providing most support for the model of Byrne et al.
2021. We report the computation cost for mapping the HERA Phase I data and
project the computation for the HERA 320-antenna data; both are feasible with a
modern server. The algorithm is broadly applicable to other interferometers and
is valid for wide-field and non-coplanar arrays.Comment: 16 pages, 10 figures, 2 tables, published on Ap
What does an interferometer really measure? Including instrument and data characteristics in the reconstruction of the 21cm power spectrum
Combining the visibilities measured by an interferometer to form a
cosmological power spectrum is a complicated process in which the window
functions play a crucial role. In a delay-based analysis, the mapping between
instrumental space, made of per-baseline delay spectra, and cosmological space
is not a one-to-one relation. Instead, neighbouring modes contribute to the
power measured at one point, with their respective contributions encoded in the
window functions. To better understand the power spectrum measured by an
interferometer, we assess the impact of instrument characteristics and analysis
choices on the estimator by deriving its exact window functions, outside of the
delay approximation. Focusing on HERA as a case study, we find that
observations made with long baselines tend to correspond to enhanced low-k
tails of the window functions, which facilitate foreground leakage outside the
wedge, whilst the choice of bandwidth and frequency taper can help narrow them
down. With the help of simple test cases and more realistic visibility
simulations, we show that, apart from tracing mode mixing, the window functions
can accurately reconstruct the power spectrum estimator of simulated
visibilities. We note that the window functions depend strongly on the
chromaticity of the beam, and less on its spatial structure - a Gaussian
approximation, ignoring side lobes, is sufficient. Finally, we investigate the
potential of asymmetric window functions, down-weighting the contribution of
low-k power to avoid foreground leakage. The window functions presented in this
work correspond to the latest HERA upper limits for the full Phase I data. They
allow an accurate reconstruction of the power spectrum measured by the
instrument and can be used in future analyses to confront theoretical models
and data directly in cylindrical space.Comment: 18 pages, 18 figures, submitted to MNRAS. Comments welcome
Characterization Of Inpaint Residuals In Interferometric Measurements of the Epoch Of Reionization
Radio Frequency Interference (RFI) is one of the systematic challenges
preventing 21cm interferometric instruments from detecting the Epoch of
Reionization. To mitigate the effects of RFI on data analysis pipelines,
numerous inpaint techniques have been developed to restore RFI corrupted data.
We examine the qualitative and quantitative errors introduced into the
visibilities and power spectrum due to inpainting. We perform our analysis on
simulated data as well as real data from the Hydrogen Epoch of Reionization
Array (HERA) Phase 1 upper limits. We also introduce a convolutional neural
network that capable of inpainting RFI corrupted data in interferometric
instruments. We train our network on simulated data and show that our network
is capable at inpainting real data without requiring to be retrained. We find
that techniques that incorporate high wavenumbers in delay space in their
modeling are best suited for inpainting over narrowband RFI. We also show that
with our fiducial parameters Discrete Prolate Spheroidal Sequences (DPSS) and
CLEAN provide the best performance for intermittent ``narrowband'' RFI while
Gaussian Progress Regression (GPR) and Least Squares Spectral Analysis (LSSA)
provide the best performance for larger RFI gaps. However we caution that these
qualitative conclusions are sensitive to the chosen hyperparameters of each
inpainting technique. We find these results to be consistent in both simulated
and real visibilities. We show that all inpainting techniques reliably
reproduce foreground dominated modes in the power spectrum. Since the
inpainting techniques should not be capable of reproducing noise realizations,
we find that the largest errors occur in the noise dominated delay modes. We
show that in the future, as the noise level of the data comes down, CLEAN and
DPSS are most capable of reproducing the fine frequency structure in the
visibilities of HERA data.Comment: 26 pages, 18 figure
Direct Optimal Mapping Image Power Spectrum and its Window Functions
The key to detecting neutral hydrogen during the epoch of reionization (EoR)
is to separate the cosmological signal from the dominating foreground
radiation. We developed direct optimal mapping (Xu et al. 2022) to map
interferometric visibilities; it contains only linear operations, with full
knowledge of point spread functions from visibilities to images. Here we
present an FFT-based image power spectrum and its window functions based on
direct optimal mapping. We use noiseless simulation, based on the Hydrogen
Epoch of Reionization Array (HERA) Phase I configuration, to study the image
power spectrum properties. The window functions show power leakage
from the foreground-dominated region into the EoR window; the 2D and 1D power
spectra also verify the separation between the foregrounds and the EoR.
Furthermore, we simulated visibilities from a -complete array and
calculated its image power spectrum. The result shows that the foreground--EoR
leakage is further suppressed below , dominated by the tapering
function sidelobes; the 2D power spectrum does not show signs of the horizon
wedge. The -complete result provides a reference case for future 21cm
cosmology array designs.Comment: Submitted to Ap
Search for the Epoch of Reionisation with HERA: Upper Limits on the Closure Phase Delay Power Spectrum
Radio interferometers aiming to measure the power spectrum of the redshifted
21 cm line during the Epoch of Reionisation (EoR) need to achieve an
unprecedented dynamic range to separate the weak signal from overwhelming
foreground emissions. Calibration inaccuracies can compromise the sensitivity
of these measurements to the effect that a detection of the EoR is precluded.
An alternative to standard analysis techniques makes use of the closure phase,
which allows one to bypass antenna-based direction-independent calibration.
Similarly to standard approaches, we use a delay spectrum technique to search
for the EoR signal. Using 94 nights of data observed with Phase I of the
Hydrogen Epoch of Reionization Array (HERA), we place approximate constraints
on the 21 cm power spectrum at . We find at 95% confidence that the 21
cm EoR brightness temperature is (372) "pseudo" mK at 1.14
"pseudo" Mpc, where the "pseudo" emphasises that these limits are to
be interpreted as approximations to the actual distance scales and brightness
temperatures. Using a fiducial EoR model, we demonstrate the feasibility of
detecting the EoR with the full array. Compared to standard methods, the
closure phase processing is relatively simple, thereby providing an important
independent check on results derived using visibility intensities, or related.Comment: 16 pages, 14 figures, accepted for publication by MNRA
Improved Constraints on the 21 cm EoR Power Spectrum and the X-Ray Heating of the IGM with HERA Phase I Observations
We report the most sensitive upper limits to date on the 21 cm epoch of
reionization power spectrum using 94 nights of observing with Phase I of the
Hydrogen Epoch of Reionization Array (HERA). Using similar analysis techniques
as in previously reported limits (HERA Collaboration 2022a), we find at 95%
confidence that Mpc) mK at and that Mpc mK at , an improvement by a factor of 2.1 and 2.6 respectively. These limits are
mostly consistent with thermal noise over a wide range of after our data
quality cuts, despite performing a relatively conservative analysis designed to
minimize signal loss. Our results are validated with both statistical tests on
the data and end-to-end pipeline simulations. We also report updated
constraints on the astrophysics of reionization and the cosmic dawn. Using
multiple independent modeling and inference techniques previously employed by
HERA Collaboration (2022b), we find that the intergalactic medium must have
been heated above the adiabatic cooling limit at least as early as ,
ruling out a broad set of so-called "cold reionization" scenarios. If this
heating is due to high-mass X-ray binaries during the cosmic dawn, as is
generally believed, our result's 99% credible interval excludes the local
relationship between soft X-ray luminosity and star formation and thus requires
heating driven by evolved low-metallicity stars.Comment: 57 pages, 37 figures. Updated to match the accepted ApJ version.
Corresponding author: Joshua S. Dillo
Abdominal aortic aneurysm in a patient with low back pain
STUDY DESIGN: Resident\u27s case problem. BACKGROUND: The purpose of this report was to describe (1) the clinical reasoning that led a clinician to identify an abdominal aortic aneurysm (AAA) in a patient with low back pain requiring immediate medical referral, and (2) an evidence-based approach to clinical evaluation of patients with suspected AAA. DIAGNOSIS: The patient was unable to identify a specific mechanism of injury for his low back pain, lacked aggravating/easing factors for his symptoms, and complained of night pain and an inability to ease his symptoms with position changes. While the patient\u27s symptoms remained unchanged during physical examination of the lumbar spine and hip, abdominal palpation revealed a strong, nontender pulsation over the midline of the upper and lower abdominal quadrants. Due to concern for an AAA, the patient was immediately referred to his physician. Subsequent computed tomography imaging revealed a prominent AAA, which measured up to 5.5 cm in greatest dimension and extended from below the renal arteries to the bifurcation of the iliac arteries. The patient initially deferred surgical intervention but eventually consented 6 months later, after repeat computed tomography imaging revealed that the AAA had progressed to 6.7 cm in greatest dimension. DISCUSSION: It is essential for physical therapists to be familiar with a diagnostic pathway to help identify AAA in patients presenting with apparent musculoskeletal complaints. Knowledge of the risk factors for AAA, understanding how to screen for nonmusculoskeletal symptoms, and a basic competence in abdominal palpation and how to interpret findings will help with the clinician\u27s clinical decision making
Abdominal Aortic Aneurysm in a Patient With Low Back Pain
STUDY DESIGN: Resident\u27s case problem. BACKGROUND: The purpose of this report was to describe (1) the clinical reasoning that led a clinician to identify an abdominal aortic aneurysm (AAA) in a patient with low back pain requiring immediate medical referral, and (2) an evidence-based approach to clinical evaluation of patients with suspected AAA. DIAGNOSIS: The patient was unable to identify a specific mechanism of injury for his low back pain, lacked aggravating/easing factors for his symptoms, and complained of night pain and an inability to ease his symptoms with position changes. While the patient\u27s symptoms remained unchanged during physical examination of the lumbar spine and hip, abdominal palpation revealed a strong, nontender pulsation over the midline of the upper and lower abdominal quadrants. Due to concern for an AAA, the patient was immediately referred to his physician. Subsequent computed tomography imaging revealed a prominent AAA, which measured up to 5.5 cm in greatest dimension and extended from below the renal arteries to the bifurcation of the iliac arteries. The patient initially deferred surgical intervention but eventually consented 6 months later, after repeat computed tomography imaging revealed that the AAA had progressed to 6.7 cm in greatest dimension. DISCUSSION: It is essential for physical therapists to be familiar with a diagnostic pathway to help identify AAA in patients presenting with apparent musculoskeletal complaints. Knowledge of the risk factors for AAA, understanding how to screen for nonmusculoskeletal symptoms, and a basic competence in abdominal palpation and how to interpret findings will help with the clinician\u27s clinical decision making