878 research outputs found
Inhibition of energy transfer reactions in spinach chloroplasts by discarine B, a new peptide alkaloid
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
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
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
Determining the driving forces to environmental change processes of La Araucanía, Chile. The "cultural landscape" as a framework
Indexación: Scopus; Scielo.El artículo propone el concepto de paisaje cultural como una perspectiva holística de análisis de procesos de transformación del paisaje. Para ello se utilizó como caso de estudio el proceso de degradación ambiental de la región de La Araucanía (Chile). Se esclarecieron las motivaciones de las actuaciones en el territorio y sus fuerzas conductoras. Estas fuerzas se relacionan a objetivos económicos externos a la población local y generaron una transformación del paisaje impactando la forma de vida de sus habitantes, quebrando el acoplamiento estructural entre población y paisaje, resultando en un paisaje cultural degradado ambientalmente.The notion of cultural landscape was deployed to analyze transformation processes of rural landscapes. As a case study, environmental degradation processes in La Araucania (Chile) region were analyzed. The goals of actions over the territory and their driving forces were determined. These actions were related to economic motives external to local inhabitants and produced deep transformations of the landscape and impacted the way of life of its inhabitants, breaking down the structural coupling between population and landscape, resulting in an environmentally degraded cultural landscape.https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0719-26812017000300051&lng=en&nrm=iso&tlng=e
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,
and respectively. We discuss the numerical difficulties that
arise in the numerical calculation of in the case of strong
intermittency. When the frequency corresponds to a Ornstein-Uhlenbeck process,
we compute analytically 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
Measuring the Lyapunov exponent using quantum mechanics
We study the time evolution of two wave packets prepared at the same initial
state, but evolving under slightly different Hamiltonians. For chaotic systems,
we determine the circumstances that lead to an exponential decay with time of
the wave packet overlap function. We show that for sufficiently weak
perturbations, the exponential decay follows a Fermi golden rule, while by
making the difference between the two Hamiltonians larger, the characteristic
exponential decay time becomes the Lyapunov exponent of the classical system.
We illustrate our theoretical findings by investigating numerically the overlap
decay function of a two-dimensional dynamical system.Comment: 9 pages, 6 figure
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