27,800 research outputs found
Unconstrained video monitoring of breathing behavior and application to diagnosis of sleep apnea
This paper presents a new real-time automated infrared video monitoring technique for detection of breathing anomalies, and its application in the diagnosis of obstructive sleep apnea. We introduce a novel motion model to detect subtle, cyclical breathing signals from video, a new 3-D unsupervised self-adaptive breathing template to learn individuals' normal breathing patterns online, and a robust action classification method to recognize abnormal breathing activities and limb movements. This technique avoids imposing positional constraints on the patient, allowing patients to sleep on their back or side, with or without facing the camera, fully or partially occluded by the bed clothes. Moreover, shallow and abdominal breathing patterns do not adversely affect the performance of the method, and it is insensitive to environmental settings such as infrared lighting levels and camera view angles. The experimental results show that the technique achieves high accuracy (94% for the clinical data) in recognizing apnea episodes and body movements and is robust to various occlusion levels, body poses, body movements (i.e., minor head movement, limb movement, body rotation, and slight torso movement), and breathing behavior (e.g., shallow versus heavy breathing, mouth breathing, chest breathing, and abdominal breathing). Ă© 2013 IEEE
Disabled peopleâs experiences of anti-social behaviour and harassment in social housing: a critical review
Kinetic Theory of Collisionless Self-Gravitating Gases: II. Relativistic Corrections in Galactic Dynamics
In this paper we study the kinetic theory of many-particle astrophysical
systems imposing axial symmetry and extending our previous analysis in Phys.
Rev. D 83, 123007 (2011). Starting from a Newtonian model describing a
collisionless self-gravitating gas, we develop a framework to include
systematically the first general relativistic corrections to the matter
distribution and gravitational potentials for general stationary systems. Then,
we use our method to obtain particular solutions for the case of the Morgan &
Morgan disks. The models obtained are fully analytical and correspond to the
post-Newtonian generalizations of classical ones. We explore some properties of
the models in order to estimate the importance of post-Newtonian corrections
and we find that, contrary to the expectations, the main modifications appear
far from the galaxy cores. As a by-product of this investigation we derive the
corrected version of the tensor virial theorem. For stationary systems we
recover the same result as in the Newtonian theory. However, for time dependent
backgrounds we find that there is an extra piece that contributes to the
variation of the inertia tensor.Comment: 30 pages, 8 figures. v2: Minor corrections and references added.
Conclusions unchanged. v3: Version published in PR
Optical frequency combs from high-order sideband generation
We report on the generation of frequency combs from the recently-discovered
phenomenon of high-order sideband generation (HSG). A near-band gap
continuous-wave (cw) laser with frequency was transmitted
through an epitaxial layer containing GaAs/AlGaAs quantum wells that were
driven by quasi-cw in-plane electric fields between 4 and 50
kV/cm oscillating at frequencies between 240 and 640 GHz.
Frequency combs with teeth at
( even) were produced, with maximum reported , corresponding to a
maximum comb span THz. Comb spectra with the identical product
were found to have similar spans and shapes
in most cases, as expected from the picture of HSG as a scattering-limited
electron-hole recollision phenomenon. The HSG combs were used to measure the
frequency and linewidth of our THz source as a demonstration of potential
applications
The development and application of water management sustainability indicators in Brazil and Scotland
Recommended from our members
Effect of Brief Biofeedback via a Smartphone App on Stress Recovery: Randomized Experimental Study.
BACKGROUND:Smartphones are often vilified for negatively influencing well-being and contributing to stress. However, these devices may, in fact, be useful in times of stress and, in particular, aid in stress recovery. Mobile apps that deliver evidence-based techniques for stress reduction, such as heart rate variability biofeedback (HRVB) training, hold promise as convenient, accessible, and effective stress-reducing tools. Numerous mobile health apps that may potentially aid in stress recovery are available, but very few have demonstrated that they can influence health-related physiological stress parameters (eg, salivary biomarkers of stress). The ability to recover swiftly from stress and reduce physiological arousal is particularly important for long-term health, and thus, it is imperative that evidence is provided to demonstrate the effectiveness of stress-reducing mobile health apps in this context. OBJECTIVE:The purpose of this research was to investigate the physiological and psychological effects of using a smartphone app for HRVB training following a stressful experience. The efficacy of the gamified Breather component of the Happify mobile health app was examined in an experimental setting. METHODS:In this study, participants (N=140) underwent a laboratory stressor and were randomly assigned to recover in one of three ways: with no phone present, with a phone present, with the HRBV game. Those in the no phone condition had no access to their phone. Those in the phone present condition had their phone but did not use it. Those in the HRVB game condition used the serious game Breather on the Happify app. Stress recovery was assessed via repeated measures of salivary alpha amylase, cortisol, and self-reported acute stress (on a 1-100 scale). RESULTS:Participants in the HRVB game condition had significantly lower levels of salivary alpha amylase during recovery than participants in the other conditions (F2,133=3.78, P=.03). There were no significant differences among the conditions during recovery for salivary cortisol levels or self-reported stress. CONCLUSIONS:These results show that engaging in a brief HRVB training session on a smartphone reduces levels of salivary alpha amylase following a stressful experience, providing preliminary evidence for the effectiveness of Breather in improving physiological stress recovery. Given the known ties between stress recovery and future well-being, this study provides a possible mechanism by which gamified biofeedback apps may lead to better health
The Stellar and Gas Kinematics of Several Irregular Galaxies
We present long-slit spectra of three irregular galaxies from which we
determinethe stellar kinematics in two of the galaxies (NGC 1156 and NGC 4449)
and ionized-gas kinematics in all three (including NGC 2366). We compare this
to the optical morphology and to the HI kinematics of the galaxies. In the
ionized gas, we see a linear velocity gradient in all three galaxies. In NGC
1156 we also detect a weak linear velocity gradient in the stars of (5+/-1/sin
i) km/s/kpc to a radius of 1.6 kpc. The stars and gas are rotating about the
same axis, but this is different from the major axis of the stellar bar which
dominates the optical light of the galaxy. In NGC 4449 we do not detect
organized rotation of the stars and place an upper limit of (3/sin i) km/s/kpc
to a radius of 1.2 kpc. For NGC 4449, which has signs of a past interaction
with another galaxy, we develop a model to fit the observed kinematics of the
stars and gas. In this model the stellar component is in a rotating disk seen
nearly face-on while the gas is in a tilted disk with orbits whose planes
precess in the gravitational potential. This model reproduces the apparent
counter-rotation of the inner gas of the galaxy. The peculiar orbits of the gas
are presumed due to acquisition of gas in the past interaction.Comment: To be published in ApJ, November 20, 200
Attracted Diffusion-Limited Aggregation
In this paper, we present results of extensive Monte Carlo simulations of
diffusion-limited aggregation (DLA) with a seed placed on an attractive plane
as a simple model in connection with the electrical double layers. We compute
the fractal dimension of the aggregated patterns as a function of the
attraction strength \alpha. For the patterns grown in both two and three
dimensions, the fractal dimension shows a significant dependence on the
attraction strength for small values of \alpha, and approaches to that of the
ordinary two-dimensional (2D) DLA in the limit of large \alpha. For
non-attracting case with \alpha=1, our results in three dimensions reproduce
the patterns of 3D ordinary DLA, while in two dimensions our model leads to
formation of a compact cluster with dimension two. For intermediate \alpha, the
3D clusters have quasi-2D structure with a fractal dimension very close to that
of the ordinary 2D-DLA. This allows one to control morphology of a growing
cluster by tuning a single external parameter \alpha.Comment: 6 pages, 6 figures, to appear in Phys. Rev. E (2012
- âŠ