1,929 research outputs found
Sleep duration and incidence of obesity in infants, children and adolescents : a systematic review and meta-analysis of prospective studies
Study Objective:
To assess the prospective relationship between sleep and obesity in a paediatric population.
Methods:
We performed a systematic search using PubMed, Embase, Web of Science and Cochrane (up to 25th September 2017). Included studies were prospective, had follow-up >1 year, had duration of sleep at baseline, and measures of incidence of overweight or obesity and/or changes in body mass index (BMI) z-score and BMI during follow-up. We extracted relative risks or changes in BMI z-score or BMI and 95% confidence intervals (CI) and pooled them using a random effect model. Results: Forty-two studies were included but, as there was significant heterogeneity, results are presented by age strata. Short sleep was associated with a greater risk of developing overweight or obesity in infancy (7 Studies, 14 738 participants, RR: 1.40; 95% CI 1.19 to 1.65; p<0.001), early childhood (8 Studies, 31 104 participants, RR: 1.57; 1.40 to 1.76; p<0.001), middle childhood (3 studies, 3 005 participants, RR: 2.23; 2.18 to 2.27; p<0.001) and adolescence (3 studies, 26 652 participants, RR: 1.30; 1.11 to 1.53; p<0.002). Sleep duration was also associated with a significant change in BMI z-score (14 studies, 18 cohorts, 31 665 participants) (mean difference -0.03; -0.04 to -0.01 per h sleep; P=0.001) and in BMI (16 studies, 24 cohorts, 24 894 participants) (mean difference -0.03 kg/m2; -0.04 to -0.01 for every h of increase in sleep; P=0.001).
Conclusions:
Short sleep duration is a risk factor or marker of the development of obesity in infants, children and adolescents
Effect of Pulse Shaping on Subharmonic Aided Pressure Estimation In Vitro and In Vivo.
OBJECTIVES: Subharmonic imaging (SHI) is a technique that uses the nonlinear oscillations of microbubbles when exposed to ultrasound at high pressures transmitting at the fundamental frequency ie, f
METHODS: Eight waveforms with different envelopes were optimized with respect to acoustic power at which the SHAPE study is most sensitive. The study was run with four input transmit cycles, first in vitro and then in vivo in three canines to select the waveform that achieved the best sensitivity for detecting changes in portal pressures using SHAPE. A Logiq 9 scanner with a 4C curvi-linear array was used to acquire 2.5 MHz radio-frequency data. Scanning was performed in dual imaging mode with B-mode imaging at 4 MHz and a SHI contrast mode transmitting at 2.5 MHz and receiving at 1.25 MHz. Sonazoid, which is a lipid stabilized gas filled bubble of perfluorobutane, was used as the contrast agent in this study.
RESULTS: A linear decrease in subharmonic amplitude with increased pressure was observed for all waveforms (r from -0.77 to -0.93; P \u3c .001) in vitro. There was a significantly higher correlation of the SHAPE gradient with changing pressures for the broadband pulses as compared to the narrowband pulses in both in vitro and in vivo results. The highest correlation was achieved with a Gaussian windowed binomial filtered square wave with an r-value of -0.95. One of the three canines was eliminated for technical reasons, while the other two produced very similar results to those obtained in vitro (r from -0.72 to -0.98; P
CONCLUSIONS: Using this waveform is an improvement to the existing SHAPE technique (where a square wave was used) and should make SHAPE more sensitive for noninvasively determining portal hypertension
On the assessment of passive devices for structural control via real-time dynamic substructuring
In this work, the applicability of a dynamic testing technique known as real-time dynamic substructuring (RTDS) for the assessment of passive vibration suppression systems in seismic protection of buildings is analysed. RTDS is an efficient method for the assessment of dynamic and rate-dependent behaviour of systems subjected to dynamic excitation at real scale and in real scenarios. The actuators used in RTDS test introduce additional undesirable dynamics into the system, which are often not fully compensated for in the actuator controller—these dynamics are commonly approximated as a feedback delay. To guarantee the validity and accuracy of an RTDS simulation, a stability analysis of the substructured system that includes the feedback delay should be carried out. In this paper, we present explicit analyses that provide a dynamic characterization of the delay-induced phenomena in RTDS simulations when considering passive vibration suppression systems with strong nonlinearities. We present a complete set of closed-form expressions to describe the main phenomena because of delay in terms of dynamic stability in an RTDS simulation. Through an experimental study, we confirm the existence of self-sustained oscillations caused by very small delay in the feedback loop. This lead the system to instability in the form of high-frequency oscillations. Copyright © 2011 John Wiley & Sons, Ltd
Observing Exoplanets with High-Dispersion Coronagraphy. II. Demonstration of an Active Single-Mode Fiber Injection Unit
High-dispersion coronagraphy (HDC) optimally combines high contrast imaging
techniques such as adaptive optics/wavefront control plus coronagraphy to high
spectral resolution spectroscopy. HDC is a critical pathway towards fully
characterizing exoplanet atmospheres across a broad range of masses from giant
gaseous planets down to Earth-like planets. In addition to determining the
molecular composition of exoplanet atmospheres, HDC also enables Doppler
mapping of atmosphere inhomogeneities (temperature, clouds, wind), as well as
precise measurements of exoplanet rotational velocities. Here, we demonstrate
an innovative concept for injecting the directly-imaged planet light into a
single-mode fiber, linking a high-contrast adaptively-corrected coronagraph to
a high-resolution spectrograph (diffraction-limited or not). Our laboratory
demonstration includes three key milestones: close-to-theoretical injection
efficiency, accurate pointing and tracking, on-fiber coherent modulation and
speckle nulling of spurious starlight signal coupling into the fiber. Using the
extreme modal selectivity of single-mode fibers, we also demonstrated speckle
suppression gains that outperform conventional image-based speckle nulling by
at least two orders of magnitude.Comment: 10 pages, 7 figures, accepted by Ap
Is There an Association of Physical Activity with Brain Volume, Behavior, and Day-to-day Functioning? A Cross Sectional Design in Prodromal and Early Huntington Disease
Background: Huntington disease (HD) is a genetic neurodegenerative disease leading to progressive motor, cognitive, and behavioral decline. Subtle changes in these domains are detectable up to 15 years before a definitive motor diagnosis is made. This period, called prodromal HD, provides an opportunity to examine lifestyle behaviors that may impact disease progression. Theoretical Framework: Physical activity relates to decreased rates of brain atrophy and improved cognitive and day-to-day functioning in Alzheimer disease and healthy aging populations. Previous research has yielded mixed results regarding the impact of physical activity on disease progression in HD and paid little attention to the prodromal phase.
Methods: We conducted analyses of associations among current physical activity level, current and retrospective rate of change for hippocampus and striatum volume, and cognitive, motor, and day-to-day functioning variables. Participants were 48 gene-expanded cases with prodromal and early-diagnosed HD and 27 nongene-expanded control participants. Participants wore Fitbit Ultra activity monitors for three days and completed the self-reported International Physical Activity Questionnaire (IPAQ). Hippocampal and striatal white matter volumes were measured using magnetic resonance imaging. Cognitive tests included the Stroop Color and Word Test, and the Symbol Digit Modalities Test (SDMT). Motor function was assessed using the Unified Huntington’s Disease Rating Scale total motor score (TMS). Day-to-day functioning was measured using the World Health Organization Disability Assessment Schedule (WHODAS) version 2.0.
Results: Higher Fitbit activity scores were significantly related to better scores on the SDMT and WHODAS in case participants but not in controls. Fitbit activity scores tracked better with TMS scores in the group as a whole, though the association did not reach statistical significance in the case participants. Higher Fitbit activity scores related to less day-to-day functioning decline in retrospective slope analyses. Fitbit activity scores did not differ significantly between cases and controls.
Conclusions: This is the first known study examining the associations between activity level and imaging, motor, cognitive, and day-to-day functioning outcomes in prodromal and early HD. Preliminary results suggest physical activity positively correlates with improved cognitive and day-to-day functioning and possibly motor function in individuals in the prodromal and early phase of the condition
New ultrahigh pressure phases of H2O ice predicted using an adaptive genetic algorithm
We propose three new phases of H2O under ultrahigh pressure. Our structural
search was performed using an adaptive genetic algorithm which allows an
extensive exploration of crystal structure. The new sequence of
pressure-induced transitions beyond ice X at 0 K should be ice X - Pbcm - Pbca
- Pmc21 - P21 - P21/c phases. Across the Pmc21 - P21 transition, the
coordination number of oxygen increases from 4 to 5 with a significant increase
of density. All stable crystalline phases have nonmetallic band structures up
to 7 TPa
A Land Plant-Specific Transcription Factor Directly Enhances Transcription of a Pathogenic Noncoding RNA Template by DNA-Dependent RNA Polymerase II
Phase transitions in MgSiO3 post-perovskite in super-Earth mantles
The highest pressure form of the major Earth-forming mantle silicate is
MgSiO3 post-perovskite (PPv). Understanding the fate of PPv at TPa pressures is
the first step for understanding the mineralogy of super-Earths-type
exoplanets, arguably the most interesting for their similarities with Earth.
Modeling their internal structure requires knowledge of stable mineral phases,
their properties under compression, and major element abundances. Several
studies of PPv under extreme pressures support the notion that a sequence of
pressure induced dissociation transitions produce the elementary oxides SiO2
and MgO as the ultimate aggregation form at ~3 TPa. However, none of these
studies have addressed the problem of mantle composition, particularly major
element abundances usually expressed in terms of three main variables, the
Mg/Si and Fe/Si ratios and the Mg#, as in the Earth. Here we show that the
critical compositional parameter, the Mg/Si ratio, whose value in the Earth's
mantle is still debated, is a vital ingredient for modeling phase transitions
and internal structure of super-Earth mantles. Specifically, we have identified
new sequences of phase transformations, including new recombination reactions
that depend decisively on this ratio. This is a new level of complexity that
has not been previously addressed, but proves essential for modeling the nature
and number of internal layers in these rocky mantles.Comment: Submitted to Earth Planet. Sci. Lett., 28 pages, 6 figure
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