244 research outputs found
Clarifying spherical collapse in coupled dark energy cosmologies
The spherical collapse model is often used to follow the evolution of
overdensities into the nonlinear regime. We describe the correct approach to be
used in coupled dark energy cosmologies, where a fifth force, different from
gravity and mediated by the dark energy scalar field, influences the collapse.
We reformulate the spherical collapse description by deriving it directly from
the set of nonlinear hydrodynamical Navier Stokes equations. By comparing with
the corresponding relativistic equations, we show how the fifth force should be
taken into account within the spherical collapse picture and clarify the
problems arising when an inhomogeneous scalar field is considered within a
spherical collapse picture. We then apply our method to the case of coupled
quintessence, where the fifth force acts among cold dark matter particles, and
to growing neutrino quintessence, where the fifth force acts between neutrinos.
Furthermore, we review this method when applied to standard cosmologies and
apply our analysis to minimally coupled quintessence and check past results for
early dark energy parametrizations.Comment: 16 pages, 13 figures, published in Physical Review D, minor changes
and correction
Black hole evaporation and semiclassicality at large D
Black holes of sufficiently large initial radius are expected to be well
described by a semiclassical analysis at least until half of their initial mass
has evaporated away. For a small number of spacetime dimensions, this holds as
long as the black hole is parametrically larger than the Planck length. In that
case, curvatures are small and backreaction onto geometry is expected to be
well described by a time-dependent classical metric. We point out that at large
, small curvature is insufficient to guarantee a valid semiclassical
description of black holes. Instead, the strongest bounds come from demanding
that the rate of change of the geometry is small and that black holes scramble
information faster than they evaporate. This is a consequence of the enormous
power of Hawking radiation in -dimensions due to the large available phase
space and the resulting minuscule evaporation times. Asymptotically, only black
holes with entropies are semiclassical. We comment on
implications for realistic quantum gravity models in as well as
relations to bounds on theories with a large number of gravitationally
interacting light species.Comment: 6 page
Spherical Collapse in Chameleon Models
We study the gravitational collapse of an overdensity of nonrelativistic
matter under the action of gravity and a chameleon scalar field. We show that
the spherical collapse model is modified by the presence of a chameleon field.
In particular, we find that even though the chameleon effects can be
potentially large at small scales, for a large enough initial size of the
inhomogeneity the collapsing region possesses a thin shell that shields the
modification of gravity induced by the chameleon field, recovering the standard
gravity results. We analyse the behaviour of a collapsing shell in a
cosmological setting in the presence of a thin shell and find that, in contrast
to the usual case, the critical density for collapse depends on the initial
comoving size of the inhomogeneity.Comment: matches printed versio
Integration of Consumer-Based Activity Monitors into Clinical Practice for Children with Type 1 Diabetes: A Feasibility Study
Current technology commonly utilized in diabetes care includes continuous glucose monitors (CGMs) and insulin pumps. One often overlooked critical component to the human glucose response is daily physical activity habits. Consumer-based activity monitors may be a valid way for clinics to collect physical activity data, but whether or not children with type 1 diabetes (T1D) would wear them or use the associated mobile application is unknown. Therefore, the purpose of this study was to test the feasibility of implementing a consumer-based accelerometer directly into ongoing care for adolescents managing T1D. Methods: Adolescents with T1D were invited to participate in this study and instructed to wear a mobile physical activity monitor while also completing a diet log for a minimum of 3 days. Clinical compliance was defined as the number of participants who were compliant with all measures while also having adequate glucose recordings using either a CGM, insulin pump, or on the diet log. Feasibility was defined as \u3e50% of the total sample reaching clinical compliance. Results: A total of 57 children and teenagers between the ages of 7 and 19 agreed to participate in this study and were included in the final analysis. Chi-square results indicated significant compliance for activity tracking (p \u3c 0.001), diet logs (p = 0.04), and overall clinical compliance (p = 0.04). Conclusion: More than half the children in this study were compliant for both activity monitoring and diet logs. This indicates that it is feasible for children with T1D to wear a consumer-based activity monitor while also recording their diet for a minimum of three days
Association between Physical Activity and Sport Participation on Hemoglobin A1c among Children and Adolescents with Type 1 Diabetes
Purpose: To determine associations between physical activity (PA) and sport participation on HbA1c levels in children with type 1 diabetes (T1D). Method: Pediatric patients with T1D were invited to complete a PA and sport participation survey. Data were linked to their medical records for demographic characteristics, diabetes treatment and monitoring plans, and HbA1c levels. Results: Participants consisted of 71 females and 81 males, were 13 +- 3 years old with an average HbA1c level of 8.75 +- 1.81. Children accumulating 60 min of activity 3 days or more a week had significantly lower HbA1c compared to those who accumulated less than 3 days (p \u3c 0.01) of 60 min of activity. However, there was no significant difference in HbA1c values based on sport participation groups. A multiple linear regression model indicated that PA, race, age, duration of diagnosis, and CGM use all significantly predicted HbA1c (p \u3c 0.05). Conclusion: This study demonstrated the significant relationship between daily PA and HbA1c. Those in this sample presented with lower HbA1c values even if accumulating less than the recommended number of days of activity. Further, it was shown that sport participation alone may not be adequate enough to impact HbA1c in a similar manner
Assessing in-class participation for EFL: considerations of effectiveness and fairness for different learning styles
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Automated quantification of posterior vitreous inflammation: optical coherence tomography scan number requirements
Quantifying intraocular inflammation is crucial in managing uveitis patients. We assessed the minimum B-scan density for reliable automated vitreous intensity (VI) assessment, using a novel approach based on optical coherence tomography (OCT). OCT volume scans centered on the macula were retrospectively collected in patients with uveitis. Nine B-scans per volume scan at fixed locations were automatically analyzed. The following B-scan selections were compared against the average score of 9 B-scans per volume scan as a reference standard: 1/3/5/7 central scans (1c/3c/5c/7c), 3 widely distributed scans (3w). Image data of 49 patients (31 females) were included. The median VI was 0.029 (IQR: 0.032). The intra-class-correlation coefficient of the VI across the 9 B-scans was 0.923. The median difference from the reference standard ranged between 0.001 (7c) and 0.006 (1c). It was significantly lower for scan selection 3w than 5c, p(adjusted) = 0.022, and lower for selection 7c than 3w, p(adjusted) = 0.003. The scan selections 7c and 3w showed the two highest areas under the receiver operating curve (0.985 and 0.965, respectively). Three widely distributed B-scans are sufficient to quantify VI reliably. Highest reliability was achieved using 7 central B-scans. Automated quantification of VI in uveitis is reliable and requires only few OCT B-scans
Comparability of automated drusen volume measurements in age-related macular degeneration: a MACUSTAR study report
Drusen are hallmarks of early and intermediate age-related macular degeneration (AMD) but their quantification remains a challenge. We compared automated drusen volume measurements between different OCT devices. We included 380 eyes from 200 individuals with bilateral intermediate (iAMD, n = 126), early (eAMD, n = 25) or no AMD (n = 49) from the MACUSTAR study. We assessed OCT scans from Cirrus (200 × 200 macular cube, 6 × 6 mm; Zeiss Meditec, CA) and Spectralis (20° × 20°, 25 B-scans; 30° × 25°, 241 B-scans; Heidelberg Engineering, Germany) devices. Sensitivity and specificity for drusen detection and differences between modalities were assessed with intra-class correlation coefficients (ICCs) and mean difference in a 5 mm diameter fovea-centered circle. Specificity was > 90% in the three modalities. In eAMD, we observed highest sensitivity in the denser Spectralis scan (68.1). The two different Spectralis modalities showed a significantly higher agreement in quantifying drusen volume in iAMD (ICC 0.993 [0.991–0.994]) than the dense Spectralis with Cirrus scan (ICC 0.807 [0.757–0.847]). Formulae for drusen volume conversion in iAMD between the two devices are provided. Automated drusen volume measures are not interchangeable between devices and softwares and need to be interpreted with the used imaging devices and software in mind. Accounting for systematic difference between methods increases comparability and conversion formulae are provided. Less dense scans did not affect drusen volume measurements in iAMD but decreased sensitivity for medium drusen in eAMD. Trial registration: ClinicalTrials.gov NCT03349801. Registered on 22 November 2017
Congenital Hypothyroidism Long‐Term Follow‐up Project: Navigating the Rough Waters of a Multi‐Center, Multi‐State Public Health Project
The Region 4 Midwest Genetics Collaborative, made up of seven regional states (Illinois, Indiana, Kentucky, Michigan, Minnesota, Ohio, and Wisconsin), brought together pediatric endocrinologists, state laboratory experts, public health follow‐up specialists, and parents of children with congenital hypothyroidism (CH) to identify the three‐year follow‐up management and education patterns of primary care clinicians and pediatric endocrinologists in the care of children diagnosed with CH by state newborn screening (NBS) programs. Among a number of challenges, each state had different NBS methods, data systems, public health laws, and institutional review board (IRB) requirements. Furthermore, the diagnosis of CH was complicated by the timing of the NBS sample, the gestational age, weight, and co‐morbidities at delivery. There were 409 children with CH identified through NBS in 2007 in the seven state region. The clinician of record and the parents of these children were invited to participate in a voluntary survey. Approximately 64 % of clinician surveys were collected with responses to questions relating to treatment, monitoring practices, educational resources, genetic counseling, and services provided to children with confirmed CH and their families. Nearly one‐quarter (24 %) of parents surveyed responded to questions relating to treatment, education, genetic counseling, resources, and services they received or would like to receive. De‐identified data from six of the seven states were compiled for analysis, with one state being unable to obtain IRB approval within the study timeline. The data from this collaborative effort will improve state follow‐up programs and aid in developing three‐year follow‐up guidelines for children diagnosed with CH. To aid in the facilitation of similar public health studies, this manuscript highlights the challenges faced, and focuses on the pathway to a successful multi‐state public health endeavor.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/147153/1/jgc40464.pd
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