7,459 research outputs found
Supplemental vision screening tests: The mean values for an adult population
The adult population has been neglected as to the standardization and quantification of supplemental screening tests. A population of subjects ages 18 to 35 was tested with specific instructions for seven optometric tests: accommodative rock, prism rock, Groffman Visual Tracing Test modified for ten feet, Groffman Visial Tracing Test, Stern Fixation Test, Percon Saccadic Fixation Test and the Pierce Saccade Test. A statistical analysis was performed and the means are presented . These means can be used in patient evaluation decisions by the optometric profession
HexPak and GradPak: variable-pitch dual-head IFUs for the WIYN 3.5m Telescope Bench Spectrograph
We describe the design, construction, and expected performance of two new
fiber integral field units (IFUs) --- HexPak and GradPak --- for the WIYN 3.5m
Telescope Nasmyth focus and Bench Spectrograph. These are the first IFUs to
provide formatted fiber integral field spectroscopy with simultaneous sampling
of varying angular scales. HexPak and GradPak are in a single cable with a
dual-head design, permitting easy switching between the two different IFU heads
on the telescope without changing the spectrograph feed: the two heads feed a
variable-width double-slit. Each IFU head is comprised of a fixed arrangement
of fibers with a range of fiber diameters. The layout and diameters of the
fibers within each array are scientifically-driven for observations of
galaxies: HexPak is designed to observe face-on spiral or spheroidal galaxies
while GradPak is optimized for edge-on studies of galaxy disks. HexPak is a
hexagonal array of 2.9 arcsec fibers subtending a 40.9 arcsec diameter, with a
high-resolution circular core of 0.94 arcsec fibers subtending 6 arcsec
diameter. GradPak is a 39 by 55 arcsec rectangular array with rows of fibers of
increasing diameter from angular scales of 1.9 arcsec to 5.6 arcsec across the
array. The variable pitch of these IFU heads allows for adequate sampling of
light profile gradients while maintaining the photon limit at different scales.Comment: 10 pages, 4 figures, presented at SPIE, Astronomical Telescopes and
Instrumentation, 1 - 6 July 2012, Amsterdam, Netherland
A survey of physician receptivity to molecular diagnostic testing and readiness to act on results for early-stage colon cancer patients.
BACKGROUND: We sought to assess physician interest in molecular prognosic testing for patients with early stage colon cancer, and identify factors associated with the likelihood of test adoption.
METHODS: We identified physicians who care for patients with early-stage (pN0) colon cancer patients, mailed them a survey, and analyzed survey responses to assess clinician receptivity to the use of a new molecular test (GUCY2C) that identifies patients at risk for recurrence, and clinician readiness to act on abnormal test results.
RESULTS: Of 104 eligible potential respondents, 41 completed and returned the survey. Among responding physicians, 56 % were receptive to using the new prognostic test. Multivariable analyses showed that physicians in academic medical centers were significantly more receptive to molecular test use than those in non-academic settings. Forty-one percent of respondents were ready to act on abnormal molecular test results. Physicians who viewed current staging methods as inaccurate and were confident in their capacity to incorporate molecular testing in practice were more likely to say they would act on abnormal test results.
CONCLUSIONS: Physician receptivity to molecular diagnostic testing for early-stage colon cancer patients is likely to be influenced by practice setting and perceptions related to delivering quality care to patients.
TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT01972737
Performance of the PROMIS in Patients After Anterior Cruciate Ligament Reconstruction
Background: The Patient-Reported Outcomes Measurement Information System (PROMIS) is designed to advance patient-reported outcome (PRO) instruments by utilizing question banks for major health domains.
Purpose: To compare the responsiveness and construct validity of the PROMIS physical function computer adaptive test (PF CAT) with current PRO instruments for patients before and up to 2 years after anterior cruciate ligament (ACL) reconstruction.
Study Design: Cohort study (diagnosis); Level of evidence, 2.
Methods: Initially, 157 patients completed the PROMIS PF CAT, Short Form-36 Health Survey (SF-36 physical function [PF] and general health [GH]), Marx Activity Rating Scale (MARS), Knee injury and Osteoarthritis Outcome Score (KOOS activities of daily living [ADL], sport, and quality of life [QOL]), and EuroQol-5 dimensions questionnaire (EQ-5D) at 6 weeks, 6 months, and 2 years after ACL reconstruction. Correlations between instruments, ceiling and floor effects, effect sizes (Cohen d), and standardized response means to describe responsiveness were evaluated. Subgroup analyses compared participants with and without additional arthroscopic procedures using linear mixed models.
Results: At baseline, 6 weeks, and 6 months, the PROMIS PF CAT showed excellent or excellent-good correlations with the SF-36 PF (r = 0.75-0.80, P \u3c .01), KOOS-ADL (r = 0.63-0.70, P \u3c .01), and KOOS-sport (r = 0.32-0.69, P \u3c .01); excellent-good correlation with the EQ-5D (r = 0.60-0.71, P \u3c .01); and good correlation with the KOOS-QOL (r = 0.52-0.58, P \u3c .01). As expected, there were poor correlations with the MARS (r = 0.00-0.24, P \u3c .01) and SF-36 GH (r = 0.16-0.34, P \u3c .01 ). At 2 years, the PROMIS PF CAT showed good to excellent correlations with all PRO instruments (r = 0.42-0.72, P \u3c .01), including the MARS (r = 0.42, P \u3c .01), indicating frequent return to preinjury function. The PROMIS PF CAT had the fewest ceiling or floor effects of all instruments tested, and patients answered, on average, 4 questions. There was no significant difference in baseline physical function scores between subgroups; at follow-up, all groups showed improvements in scores that were not statistically different.
Conclusion: The PROMIS PF CAT is a valid tool to assess outcomes after ACL reconstruction up to 2 years after surgery, demonstrating the highest responsiveness to change with the fewest ceiling and floor effects and a low time burden among all instruments tested. The PROMIS PF CAT is a beneficial alternative for assessing physical function in adults before and after ACL reconstruction
Theoretical current-voltage characteristics of ferroelectric tunnel junctions
We present the concept of ferroelectric tunnel junctions (FTJs). These
junctions consist of two metal electrodes separated by a nanometer-thick
ferroelectric barrier. The current-voltage characteristics of FTJs are analyzed
under the assumption that the direct electron tunneling represents the dominant
conduction mechanism. First, the influence of converse piezoelectric effect
inherent in ferroelectric materials on the tunnel current is described. The
calculations show that the lattice strains of piezoelectric origin modify the
current-voltage relationship owing to strain-induced changes of the barrier
thickness, electron effective mass, and position of the conduction-band edge.
Remarkably, the conductance minimum becomes shifted from zero voltage due to
the piezoelectric effect, and a strain-related resistive switching takes place
after the polarization reversal in a ferroelectric barrier. Second, we analyze
the influence of the internal electric field arising due to imperfect screening
of polarization charges by electrons in metal electrodes. It is shown that, for
asymmetric FTJs, this depolarizing-field effect also leads to a considerable
change of the barrier resistance after the polarization reversal. However, the
symmetry of the resulting current-voltage loop is different from that
characteristic of the strain-related resistive switching. The crossover from
one to another type of the hysteretic curve, which accompanies the increase of
FTJ asymmetry, is described taking into account both the strain and
depolarizing-field effects. It is noted that asymmetric FTJs with dissimilar
top and bottom electrodes are preferable for the non-volatile memory
applications because of a larger resistance on/off ratio.Comment: 14 pages, 8 figure
Globular Cluster Abundances from High-Resolution, Integrated-Light Spectroscopy. III. The Large Magellanic Cloud: Fe and Ages
In this paper we refine our method for the abundance analysis of high
resolution spectroscopy of the integrated light of unresolved globular clusters
(GCs). This method was previously demonstrated for the analysis of old (10
Gyr) Milky Way GCs. Here we extend the technique to young clusters using a
training set of 9 GCs in the Large Magellanic Cloud (LMC). Depending on the
signal-to-noise ratio of the data, we use 20-100 Fe lines per cluster to
successfully constrain the ages of old clusters to within a 5 Gyr range,
the ages of 2 Gyr clusters to a 1-2 Gyr range, and the ages of the
youngest clusters (0.05-1 Gyr) to a 200 Myr range. We also demonstrate
that we can measure [Fe/H] in clusters with any age less than 12 Gyrs with
similar or only slightly larger uncertainties (0.1-0.25 dex) than those
obtained for old Milky Way GCs (0.1 dex); the slightly larger uncertainties are
due to the rapid evolution in stellar populations at these ages. In this paper,
we present only Fe abundances and ages. In the next paper in this series, we
present our complete analysis of the elements for which we are able
to measure abundances. For several of the clusters in this sample, there are no
high resolution abundances in the literature from individual member stars; our
results are the first detailed chemical abundances available. The spectra used
in this paper were obtained at Las Campanas with the echelle on the du Pont
Telescope and with the MIKE spectrograph on the Magellan Clay Telescope.Comment: 34 pages, accepted for publication in Ap
Electronic and optical properties of electromigrated molecular junctions
Electromigrated nanoscale junctions have proven very useful for studying
electronic transport at the single-molecule scale. However, confirming that
conduction is through precisely the molecule of interest and not some
contaminant or metal nanoparticle has remained a persistent challenge,
typically requiring a statistical analysis of many devices. We review how
transport mechanisms in both purely electronic and optical measurements can be
used to infer information about the nanoscale junction configuration. The
electronic response to optical excitation is particularly revealing. We briefly
discuss surface-enhanced Raman spectroscopy on such junctions, and present new
results showing that currents due to optical rectification can provide a means
of estimating the local electric field at the junction due to illumination.Comment: 19 pages, 8 figures, invited paper for forthcoming special issue of
Journal of Physics: Condensed Matter. For other related papers, see
http://www.ruf.rice.edu/~natelson/publications.htm
Locally U(1)*U(1) Symmetric Cosmological Models: Topology and Dynamics
We show examples which reveal influences of spatial topologies to dynamics,
using a class of spatially {\it closed} inhomogeneous cosmological models. The
models, called the {\it locally U(1)U(1) symmetric models} (or the {\it
generalized Gowdy models}), are characterized by the existence of two commuting
spatial {\it local} Killing vectors. For systematic investigations we first
present a classification of possible spatial topologies in this class. We
stress the significance of the locally homogeneous limits (i.e., the Bianchi
types or the `geometric structures') of the models. In particular, we show a
method of reduction to the natural reduced manifold, and analyze the
equivalences at the reduced level of the models as dynamical models. Based on
these fundamentals, we examine the influence of spatial topologies on dynamics
by obtaining translation and reflection operators which commute with the
dynamical flow in the phase space.Comment: 32 pages, 1 figure, LaTeX2e, revised Introduction slightly. To appear
in CQ
The Glasgow-Maastricht foot model, evaluation of a 26 segment kinematic model of the foot
BACKGROUND: Accurately measuring of intrinsic foot kinematics using skin mounted markers is difficult, limited in part by the physical dimensions of the foot. Existing kinematic foot models solve this problem by combining multiple bones into idealized rigid segments. This study presents a novel foot model that allows the motion of the 26 bones to be individually estimated via a combination of partial joint constraints and coupling the motion of separate joints using kinematic rhythms. METHODS: Segmented CT data from one healthy subject was used to create a template Glasgow-Maastricht foot model (GM-model). Following this, the template was scaled to produce subject-specific models for five additional healthy participants using a surface scan of the foot and ankle. Forty-three skin mounted markers, mainly positioned around the foot and ankle, were used to capture the stance phase of the right foot of the six healthy participants during walking. The GM-model was then applied to calculate the intrinsic foot kinematics. RESULTS: Distinct motion patterns where found for all joints. The variability in outcome depended on the location of the joint, with reasonable results for sagittal plane motions and poor results for transverse plane motions. CONCLUSIONS: The results of the GM-model were comparable with existing literature, including bone pin studies, with respect to the range of motion, motion pattern and timing of the motion in the studied joints. This novel model is the most complete kinematic model to date. Further evaluation of the model is warranted
Development of a hybrid Bayesian network model for predicting acute fish toxicity using multiple lines of evidence
A hybrid Bayesian network (BN) was developed for predicting the acute toxicity of chemicals to fish, using data from fish embryo toxicity (FET) testing in combination with other information. This model can support the use of FET data in a Weight-of-Evidence (WOE) approach for replacing the use of ju-venile fish. The BN predicted correct toxicity intervals for 69%–80% of the tested substances. The model was most sensitive to components quantified by toxicity data, and least sensitive to compo-nents quantified by expert knowledge. The model is publicly available through a web interface. Fur-ther development of this model should include additional lines of evidence, refinement of the discre-tisation, and training with a larger dataset for weighting of the lines of evidence. A refined version of this model can be a useful tool for predicting acute fish toxicity, and a contribution to more quantitative WOE approaches for ecotoxicology and environmental assessment more generally.publishedVersio
- …