Wireless Medical Sensor Networks: Design Requirements and Enabling Technologies

This article analyzes wireless communication protocols that could be used in healthcare environments (e.g., hospitals and small clinics) to transfer real-time medical information obtained from noninvasive sensors. For this purpose the features of the three currently most widely used protocols—namely, Bluetooth® (IEEE 802.15.1), ZigBee (IEEE 802.15.4), and Wi-Fi (IEEE 802.11)—are evaluated and compared. The important features under consideration include data bandwidth, frequency band, maximum transmission distance, encryption and authentication methods, power consumption, and current applications. In addition, an overview of network requirements with respect to medical sensor features, patient safety and patient data privacy, quality of service, and interoperability between other sensors is briefly presented. Sensor power consumption is also discussed because it is considered one of the main obstacles for wider adoption of wireless networks in medical applications. The outcome of this assessment will be a useful tool in the hands of biomedical engineering researchers. It will provide parameters to select the most effective combination of protocols to implement a specific wireless network of noninvasive medical sensors to monitor patients remotely in the hospital or at home

Periodic orbit bifurcations and scattering time delay fluctuations

We study fluctuations of the Wigner time delay for open (scattering) systems which exhibit mixed dynamics in the classical limit. It is shown that in the semiclassical limit the time delay fluctuations have a distribution that differs markedly from those which describe fully chaotic (or strongly disordered) systems: their moments have a power law dependence on a semiclassical parameter, with exponents that are rational fractions. These exponents are obtained from bifurcating periodic orbits trapped in the system. They are universal in situations where sufficiently long orbits contribute. We illustrate the influence of bifurcations on the time delay numerically using an open quantum map.Comment: 9 pages, 3 figures, contribution to QMC200

WKB Propagation of Gaussian Wavepackets

We analyze the semiclassical evolution of Gaussian wavepackets in chaotic systems. We prove that after some short time a Gaussian wavepacket becomes a primitive WKB state. From then on, the state can be propagated using the standard TDWKB scheme. Complex trajectories are not necessary to account for the long-time propagation. The Wigner function of the evolving state develops the structure of a classical filament plus quantum oscillations, with phase and amplitude being determined by geometric properties of a classical manifold.Comment: 4 pages, 4 figures; significant improvement

On the classical-quantum correspondence for the scattering dwell time

Using results from the theory of dynamical systems, we derive a general expression for the classical average scattering dwell time, tau_av. Remarkably, tau_av depends only on a ratio of phase space volumes. We further show that, for a wide class of systems, the average classical dwell time is not in correspondence with the energy average of the quantum Wigner time delay.Comment: 5 pages, 1 figur

Statistical bounds on the dynamical production of entanglement

We present a random-matrix analysis of the entangling power of a unitary operator as a function of the number of times it is iterated. We consider unitaries belonging to the circular ensembles of random matrices (CUE or COE) applied to random (real or complex) non-entangled states. We verify numerically that the average entangling power is a monotonic decreasing function of time. The same behavior is observed for the "operator entanglement" --an alternative measure of the entangling strength of a unitary. On the analytical side we calculate the CUE operator entanglement and asymptotic values for the entangling power. We also provide a theoretical explanation of the time dependence in the CUE cases.Comment: preprint format, 14 pages, 2 figure

Semiclassical Description of Wavepacket Revival

We test the ability of semiclassical theory to describe quantitatively the revival of quantum wavepackets --a long time phenomena-- in the one dimensional quartic oscillator (a Kerr type Hamiltonian). Two semiclassical theories are considered: time-dependent WKB and Van Vleck propagation. We show that both approaches describe with impressive accuracy the autocorrelation function and wavefunction up to times longer than the revival time. Moreover, in the Van Vleck approach, we can show analytically that the range of agreement extends to arbitrary long times.Comment: 10 pages, 6 figure

Influence of urban trees on noise levels in a central Chilean city

The effect of urban trees as a noise mitigating element was determined on Alameda Avenue in the city of Talca, Chile, a Mediterranean continental area. Maximum and minimum noise, especially generated from vehicles, was recorded at 13 points in four sections of the avenue for twelve days, three times a day at different distances from the edge of the street way, which generated a total of 2,080 noise records. At each point a circular plot of 201 m2 was established to determine tree and shrub coverage. The results showed significant differences of noise between the classes of coverage; however there was no relationship significant between the noise level and the increase in coverage, which can be explained by the large amplitude in the noise registers. The vegetation located at 6.5 meters from the sound source shows lower levels of noise when the coverage is increased, proving the environmental function of the vegetation in the mitigation of this pollutant agent. Regarding theses of the findings, it is necessary to implement public policies that consider urban planning, incorporating in its design greater and better availability of tree species and that certain public space are located away from sources of noise pollution.The effect of urban trees as a noise mitigating element was determined on Alameda Avenue in the city of Talca, Chile, a Mediterranean continental area. Maximum and minimum noise, especially generated from vehicles, was recorded at 13 points in four sections of the avenue for twelve days, three times a day at different distances from the edge of the street way, which generated a total of 2,080 noise records. At each point a circular plot of 201 m2 was established to determine tree and shrub coverage. The results showed significant differences of noise between the classes of coverage; however there was no relationship significant between the noise level and the increase in coverage, which can be explained by the large amplitude in the noise registers. The vegetation located at 6.5 meters from the sound source shows lower levels of noise when the coverage is increased, proving the environmental function of the vegetation in the mitigation of this pollutant agent. Regarding theses of the findings, it is necessary to implement public policies that consider urban planning, incorporating in its design greater and better availability of tree species and that certain public space are located away from sources of noise pollution

Influencia del arbolado urbano sobre los niveles de ruido en una ciudad de Chile central

The effect of urban trees as a noise mitigating element was determined on Alameda Avenue in the city of Talca, Chile, a Mediterranean continental area. Maximum and minimum noise, especially generated from vehicles, was recorded at 13 points in four sections of the avenue for twelve days, three times a day at different distances from the edge of the street way, which generated a total of 2,080 noise records. At each point a circular plot of 201 m2 was established to determine tree and shrub coverage. The results showed significant differences of noise between the classes of coverage; however there was no relationship significant between the noise level and the increase in coverage, which can be explained by the large amplitude in the noise registers. The vegetation located at 6.5 meters from the sound source shows lower levels of noise when the coverage is increased, proving the environmental function of the vegetation in the mitigation of this pollutant agent. Regarding theses of the findings, it is necessary to implement public policies that consider urban planning, incorporating in its design greater and better availability of tree species and that certain public space are located away from sources of noise pollution.Se determinó el efecto del arbolado urbano como elemento mitigador del ruido en la avenida Alameda de la ciudad de Talca, Chile, ubicada en el área continental. Se registró durante 12 doce días el ruido máximo y mínimo, especialmente proveniente del tránsito vehicular, en 13 puntos en cuatro secciones de la avenida, en tres horarios durante el día a diferentes distancias del borde de la vía, generándose un total de 2.080 registros de ruido. En cada punto se estableció una parcela circular de 201 m2 para determinar la cobertura arbórea y arbustiva. Los resultados mostraron diferencias significativas entre las clases de cobertura, sin embargo no se observó una relación significativa entre el nivel de ruido y el aumento de la cobertura, lo que se puede explicar por la gran amplitud en los registros de ruido. La vegetación ubicada a 6,5 metros de la fuente sonora muestra menores niveles de ruido cuando se incrementa la cobertura vegetal, comprobando la función ambiental de la vegetación en la mitigación de este contaminante. En consideración a los hallazgos, es necesario implementar políticas públicas que consideren una planificación urbana que incorpore en su diseño mayor y mejor disponibilidad de especies arbóreas y que ciertos espacios públicos, como el estudiado, se localice alejado de las fuentes de contaminación acústica.Fil: Calquín P., Felipe. Corporación Nacional Forestal (Chile)Fil: Ponce-Donoso, Mauricio. Universidad de Talca (Chile)Fil: Vallejos-Barra, Óscar. Universidad de Talca (Chile)Fil: Plaza T., Exequiel. Universidad de Talca (Chile

On the semiclassical theory for universal transmission fluctuations in chaotic systems: the importance of unitarity

The standard semiclassical calculation of transmission correlation functions for chaotic systems is severely influenced by unitarity problems. We show that unitarity alone imposes a set of relationships between cross sections correlation functions which go beyond the diagonal approximation. When these relationships are properly used to supplement the semiclassical scheme we obtain transmission correlation functions in full agreement with the exact statistical theory and the experiment. Our approach also provides a novel prediction for the transmission correlations in the case where time reversal symmetry is present

Lyapunov exponent of the random frequency oscillator: cumulant expansion approach

We consider a one-dimensional harmonic oscillator with a random frequency, focusing on both the standard and the generalized Lyapunov exponents, $\lambda$ and $\lambda^\star$ respectively. We discuss the numerical difficulties that arise in the numerical calculation of $\lambda^\star$ in the case of strong intermittency. When the frequency corresponds to a Ornstein-Uhlenbeck process, we compute analytically $\lambda^\star$ by using a cumulant expansion including up to the fourth order. Connections with the problem of finding an analytical estimate for the largest Lyapunov exponent of a many-body system with smooth interactions are discussed.Comment: 6 pages, 4 figures, to appear in J. Phys. Conf. Series - LAWNP0