4,378 research outputs found
Predicting subjective refraction with dynamic retinal image quality analysis
The aim of this work is to evaluate the performance of a novel algorithm that combines dynamic
wavefront aberrometry data and descriptors of the retinal image quality from objective autorefractor
measurements to predict subjective refraction. We conducted a retrospective study of the prediction
accuracy and precision of the novel algorithm compared to standard search-based retinal image
quality optimization algorithms. Dynamic measurements from 34 adult patients were taken with a
handheld wavefront autorefractor and static data was obtained with a high-end desktop wavefront
aberrometer. The search-based algorithms did not signifcantly improve the results of the desktop
system, while the dynamic approach was able to simultaneously reduce the standard deviation (up
to a 15% for reduction of spherical equivalent power) and the mean bias error of the predictions (up
to 80% reduction of spherical equivalent power) for the handheld aberrometer. These results suggest
that dynamic retinal image analysis can substantially improve the accuracy and precision of the
portable wavefront autorefractor relative to subjective refraction.The authors thanks to Dr. David Friedman (Wilmer Eye Institute, Johns Hopkins University School of Medicine)
and his team for their help with study defnition and data acquisition. Eduardo Lage is funded by the Ramon y
Cajal program from the Spanish Ministry of Economy, Industry and Competitivity (RYC-2016-21125). Carlos
S. Hernandez, and Andrea Gil are funded by the Madrid Regional Government through IND2019/TIC-17116
and IND2020/TIC-17340 grants. Research relating to the autorefractor reported in this publication was partially
support by the National Institute of Biomedical Imaging & Bioengineering and National Eye Institute of the
National Institutes of Health under Award Numbers R43EB024299 and R44EY025452, respectivel
The engine reformer: Syngas production in an engine for compact gas-to-liquids synthesis
Methane (CH[subscript 4]) reforming was carried out in an internal combustion engine (an “engine reformer”). We successfully produced syngas from the partial oxidation of natural gas in the cylinder of a diesel engine that was reconfigured to perform spark ignition. Performing the reaction in an engine cylinder allows some of the exothermicity to be captured as useful work. Intake conditions of 110 kPa and up to 480 °C allowed low cycle-to-cycle variability (COV[subscript nimep] 2.4, but < 1 mg/L below these equivalence ratios. These results demonstrate that the engine reformer could be a key component of a compact gas-to-liquids synthesis plant by highlighting the operating conditions under which high gas conversion, high H[subscript 2]-to-CO ratios close to 2.0, and low soot production are possible.United States. Advanced Research Projects Agency-Energy (Award DE-AR0000506)Research Triangle InitiativeMIT Energy InitiativeMassachusetts Institute of Technology. Tata Center for Technology and Desig
Electrocardiogram of the Mixmaster Universe
The Mixmaster dynamics is revisited in a new light as revealing a series of
transitions in the complex scale invariant scalar invariant of the Weyl
curvature tensor best represented by the speciality index , which
gives a 4-dimensional measure of the evolution of the spacetime independent of
all the 3-dimensional gauge-dependent variables except for the time used to
parametrize it. Its graph versus time characterized by correlated isolated
pulses in its real and imaginary parts corresponding to curvature wall
collisions serves as a sort of electrocardiogram of the Mixmaster universe,
with each such pulse pair arising from a single circuit or ``complex pulse''
around the origin in the complex plane. These pulses in the speciality index
and their limiting points on the real axis seem to invariantly characterize
some of the so called spike solutions in inhomogeneous cosmology and should
play an important role as a gauge invariant lens through which to view current
investigations of inhomogeneous Mixmaster dynamics.Comment: version 3: 20 pages iopart style, 19 eps figure files for 8 latex
figures; added example of a transient true spike to contrast with the
permanent true spike example from the Lim family of true spike solutions;
remarks in introduction and conclusion adjusted and toned down; minor
adjustments to the remaining tex
Learning deficit in cognitively normal apoe ε4 carriers with low β-amyloid
Introduction: In cognitively normal (CN) adults, increased rates of amyloid beta (Aβ) accumulation can be detected in low Aβ (Aβ–) apolipoprotein E (APOE) ε4 carriers. We aimed to determine the effect of ε4 on the ability to benefit from experience (ie, learn) in Aβ–CNs. Methods: Aβ– CNs(n= 333) underwent episodic memory assessments every 18 months for 108 months. A subset (n = 48) completed the Online Repeatable Cognitive Assessment-Language Learning Test (ORCA-LLT) over 6 days. Results: Aβ– ε4 carriers showed significantly lower rates of improvement on episodic memory over 108 months compared to non-carriers (d = 0.3). Rates of learning on the ORCA-LLT were significantly slower in Aβ– ε4 carriers compared to non-carriers (d = 1.2). Discussion: In Aβ– CNs,ε4 is associated with a reduced ability to benefit from experience. This manifested as reduced practice effects (small to moderate in magnitude) over 108 months on the episodic memory composite, and a learning deficit (large in magnitude) over 6 days on the ORCA-LLT. Alzheimer’s disease (AD)–related cognitive abnormalities can manifest before preclinical AD thresholds
Ametropia detection using a novel, compact wavefront autorefractor
Introduction: Despite the well-known reproducibility issues of subjective refraction, most studies evaluating autorefractors compared differences between the
device and subjective refraction. This work evaluated the performance of a novel
handheld Hartmann–Shack-based autorefractor using an alternative protocol,
which considered the inherent variability of subjective refraction.
Methods: Participants underwent an initial measurement with a desktop autorefractor, two subjective refractions (SR1 and SR2) and a final measurement with the
QuickSee Free (QSFree) portable autorefractor. Autorefractor performance was
evaluated by comparing the differences between the QSFree and each of the subjective refractions with the difference between the subjective refractions (SR1 vs.
SR2) using Bland–Altman analysis and percentage of agreement.
Results: A total of 75 subjects (53±14years) were enrolled in the study. The average difference in the absolute spherical equivalent (M) between the QSFree and
the SR1 and SR2 was ±0.24 and ±0.02D, respectively, that is, very similar or smaller
than the SR1 versus SR2 difference (±0.26D). Average differences in astigmatic
components were found to be negligible. The results demonstrate that differences
between QSFree and both subjective refractions in J0 and J45 were within ±0.50 D
for at least 96% of the measurements. The limits of agreement (LOAs) of the differences between QSFree and SR1, as well as QSFree and SR2, were higher than those
observed between SR1 and SR2 for M, J0 and J45.
Conclusions: A protocol was designed and validated for the evaluation of a refractive device to account for the variability of subjective refraction. This protocol was
used to evaluate a novel portable autorefractor and observed a smaller difference
between the device and subjective refractions than the difference between the
two subjective refraction measurements in terms of mean bias error, although the
standard deviation was higherComunidad de Madrid, Grant/Award
Number: IND-15478, IND2019/TIC-17116 and
IND2020/TIC-17340; Ministerio de Economía
y Competitividad, Grant/Award Number:
RYC-2016-21125; National Eye Institute, Grant/
Award Number: R44EY025452; Translational
Research Institute for Space Health, Grant/
Award Number: NASA NNX16AO69
Pacritinib to inhibit JAK/STAT signaling in refractory metastatic colon and rectal cancer
Background: Treatment options for patients with refractory colorectal cancer are limited and typically provide a chance of only modest benefit. The goal of this study was to evaluate the benefit of inhibiting the JAK/STAT inflammatory pathway with single agent pacritinib in patients with metastatic refractory colorectal adenocarcinoma.
Methods: A single arm institutional trial was initiated and enrolled patients with metastatic colorectal cancer refractory to at least two standard lines of treatment. Pacritinib 400 mg daily was administered orally continuously in 28 day cycles.
Results: The trial was discontinued prior to reaching the planned accrual due to an FDA hold on pacritinib and a lack of treatment benefit. Eleven patients were enrolled and seven were evaluated for response. Median baseline C-reactive protein level was 12.1 (2.1-147) mg/L. One patient had stable disease at eight weeks by RECIST criteria and six progressed. There were no grade 4 or 5 adverse events while patients were on study. The grade 2 and lower AE events experienced were consistent with prior pacritinib trials.
Conclusions: In seven evaluable patients there were no objective responses. The trial was discontinued prior to completing planned accrual based on a low likelihood that the progression free survival goal of 4 months would be met
Assesment of the QuickSee wavefront autorefractor for characterizing refractive errors in school-age children
Purpose
To assess the performance of an open-view binocular handheld aberrometer (QuickSee) for
diagnosing refractive errors in children.
Methods
123 school-age children (9.9 ± 3.3 years) with moderate refractive error underwent autorefraction
(AR) with a standard desktop device and subjective refraction (SR), with or without
cycloplegia to determine their eyeglass prescription. Measurements with QuickSee (QS)
were taken in 62 of these patients without cycloplegia (NC), and in 61 under cycloplegia (C).
Differences in refraction values (AR vs SR vs QS) as well as the visual acuity (VA) achieved
by the patients with each method (QS vs SR) were used to evaluate the performance of the
device in measuring refractive error.
Results
The spherical equivalent refraction obtained by QS agreed within 0.5 D of the SR in 71% (NC) and
70% (C) of the cases. Agreement between the desktop autorefractor and SR for the same threshold
was of 61% (NC) and 77% (C). VA resulting from QS refractions was equal to or better than
that achieved by SR procedure in 77% (NC) and 74% (C) of the patients. Average improvement in
VA with the QS refractions was of 8.6 and 13.4 optotypes for the NC and C groups respectively,
while the SR procedure provided average improvements of 8.9 (NC) and 14.8 (C) optotypes.
Conclusions
The high level of agreement between QuickSee and subjective refraction together with the
VA improvement achieved in both study groups using QuickSee refractions suggest that the device is a useful autorefraction tool for school-age children.Eduardo Lage is funded by the Ramon y
Cajal program from the Spanish Ministry of
Economy, Industry and Competitivity (RYC-2016-
21125). Pablo Perez-Merino was funded by the
Juan de la Cierva program from the same Ministry
(FJCI-2015-27101). Carlos S. Hernandez and
Andrea Gil are funded by the Madrid Regional
Government through IND2019/TIC-17116 grant
PlenOptika Inc. provided support in the form of
salaries for authors AG, MR, CSH, IC, SD, and DL,
but did not have any additional role in the study
design, data collection and decision to publish
International Veterinary Epilepsy Task Force recommendations for a veterinary epilepsy-specific MRI protocol
Epilepsy is one of the most common chronic neurological diseases in veterinary practice. Magnetic resonance imaging (MRI) is regarded as an important diagnostic test to reach the diagnosis of idiopathic epilepsy. However, given that the diagnosis requires the exclusion of other differentials for seizures, the parameters for MRI examination should allow the detection of subtle lesions which may not be obvious with existing techniques. In addition, there are several differentials for idiopathic epilepsy in humans, for example some focal cortical dysplasias, which may only apparent with special sequences, imaging planes and/or particular techniques used in performing the MRI scan. As a result, there is a need to standardize MRI examination in veterinary patients with techniques that reliably diagnose subtle lesions, identify post-seizure changes, and which will allow for future identification of underlying causes of seizures not yet apparent in the veterinary literature.
There is a need for a standardized veterinary epilepsy-specific MRI protocol which will facilitate more detailed examination of areas susceptible to generating and perpetuating seizures, is cost efficient, simple to perform and can be adapted for both low and high field scanners. Standardisation of imaging will improve clinical communication and uniformity of case definition between research studies. A 6–7 sequence epilepsy-specific MRI protocol for veterinary patients is proposed and further advanced MR and functional imaging is reviewed
Increased Sleep Fragmentation Leads to Impaired Off-Line Consolidation of Motor Memories in Humans
A growing literature supports a role for sleep after training in long-term memory consolidation and enhancement. Consequently, interrupted sleep should result in cognitive deficits. Recent evidence from an animal study indeed showed that optimal memory consolidation during sleep requires a certain amount of uninterrupted sleep
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