271 research outputs found
Deriving the respiratory sinus arrhythmia from the heartbeat time series using Empirical Mode Decomposition
Heart rate variability (HRV) is a well-known phenomenon whose characteristics
are of great clinical relevance in pathophysiologic investigations. In
particular, respiration is a powerful modulator of HRV contributing to the
oscillations at highest frequency. Like almost all natural phenomena, HRV is
the result of many nonlinearly interacting processes; therefore any linear
analysis has the potential risk of underestimating, or even missing, a great
amount of information content. Recently the technique of Empirical Mode
Decomposition (EMD) has been proposed as a new tool for the analysis of
nonlinear and nonstationary data. We applied EMD analysis to decompose the
heartbeat intervals series, derived from one electrocardiographic (ECG) signal
of 13 subjects, into their components in order to identify the modes associated
with breathing. After each decomposition the mode showing the highest frequency
and the corresponding respiratory signal were Hilbert transformed and the
instantaneous phases extracted were then compared. The results obtained
indicate a synchronization of order 1:1 between the two series proving the
existence of phase and frequency coupling between the component associated with
breathing and the respiratory signal itself in all subjects.Comment: 12 pages, 6 figures. Will be published on "Chaos, Solitons and
Fractals
Graphical calculus for Gaussian pure states
We provide a unified graphical calculus for all Gaussian pure states,
including graph transformation rules for all local and semi-local Gaussian
unitary operations, as well as local quadrature measurements. We then use this
graphical calculus to analyze continuous-variable (CV) cluster states, the
essential resource for one-way quantum computing with CV systems. Current
graphical approaches to CV cluster states are only valid in the unphysical
limit of infinite squeezing, and the associated graph transformation rules only
apply when the initial and final states are of this form. Our formalism applies
to all Gaussian pure states and subsumes these rules in a natural way. In
addition, the term "CV graph state" currently has several inequivalent
definitions in use. Using this formalism we provide a single unifying
definition that encompasses all of them. We provide many examples of how the
formalism may be used in the context of CV cluster states: defining the
"closest" CV cluster state to a given Gaussian pure state and quantifying the
error in the approximation due to finite squeezing; analyzing the optimality of
certain methods of generating CV cluster states; drawing connections between
this new graphical formalism and bosonic Hamiltonians with Gaussian ground
states, including those useful for CV one-way quantum computing; and deriving a
graphical measure of bipartite entanglement for certain classes of CV cluster
states. We mention other possible applications of this formalism and conclude
with a brief note on fault tolerance in CV one-way quantum computing.Comment: (v3) shortened title, very minor corrections (v2) minor corrections,
reference added, new figures for CZ gate and beamsplitter graph rules; (v1)
25 pages, 11 figures (made with TikZ
Ultracompact Generation of Continuous-Variable Cluster States
We propose an experimental scheme that has the potential for large-scale
realization of continuous-variable (CV) cluster states for universal quantum
computation. We do this by mapping CV cluster-state graphs onto two-mode
squeezing graphs, which can be engineered into a single optical parametric
oscillator (OPO). The desired CV cluster state is produced directly from a
joint squeezing operation on the vacuum using a multi-frequency pump beam. This
method has potential for ultracompact experimental implementation. As an
illustration, we detail an experimental proposal for creating a four-mode
square CV cluster state with a single OPO.Comment: 4 pages, 1 figure; v2 improved discussion of the implications of our
result; added discussion of finite squeezing effect
Universal Quantum Computation with Continuous-Variable Cluster States
We describe a generalization of the cluster-state model of quantum
computation to continuous-variable systems, along with a proposal for an
optical implementation using squeezed-light sources, linear optics, and
homodyne detection. For universal quantum computation, a nonlinear element is
required. This can be satisfied by adding to the toolbox any single-mode
non-Gaussian measurement, while the initial cluster state itself remains
Gaussian. Homodyne detection alone suffices to perform an arbitrary multi-mode
Gaussian transformation via the cluster state. We also propose an experiment to
demonstrate cluster-based error reduction when implementing Gaussian
operations.Comment: 4 pages, no figure
Scaling and intermittency of brain events as a manifestation of consciousness
We discuss the critical brain hypothesis and its relationship with intermittent renewal processes displaying power-law decay in the distribution of waiting times between two consecutive renewal events. In particular, studies on complex systems in a "critical" condition show that macroscopic variables, integrating the activities of many individual functional units, undergo fluctuations with an intermittent serial structure characterized by avalanches with inverse-power-law (scale-free) distribution densities of sizes and inter-event times. This condition, which is denoted as "fractal intermittency", was found in the electroencephalograms of subjects observed during a resting state wake condition. It remained unsolved whether fractal intermittency correlates with the stream of consciousness or with a non-task-driven default mode activity, also present in non-conscious states, like deep sleep. After reviewing a method of scaling analysis of intermittent systems based of event-driven random walks, we show that during deep sleep fractal intermittency breaks down, and re-establishes during REM (Rapid Eye Movement) sleep, with essentially the same anomalous scaling of the pre-sleep wake condition. From the comparison of the pre-sleep wake, deep sleep and REM conditions we argue that the scaling features of intermittent brain events are related to the level of consciousness and, consequently, could be exploited as a possible indicator of consciousness in clinical applications
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Dish/Stirling for Department of Defense applications final report
This report describes a Strategic Environmental Research and Development Program (SERDP) project to field a dish/Stirling system at a southwestern US military facility. This project entitled ``Dish/Stirling for DoD Applications`` was started in August 1993 and was completed in September 1996. The project`s objective was to assist military facilities to field and evaluate emerging environmentally sound and potentially economical dish/Stirling technology. Dish/Stirling technology has the potential to produce electricity at competitive costs while at the same time providing a secure and environmentally benign source of power. In accordance with the SERDP charter, this project leveraged a US Department of Energy (DOE) cost-shared project between Sandia National Laboratories and Cummins Power Generation, Inc. (CPG). CPG is a wholly owned subsidiary of Cummins Engine Company, a leading manufacturer of diesel engines. To accomplish this objective, the project called for the installation of a dish/Stirling system at a military facility to establish first-hand experience in the operation of a dish/Stirling system. To scope the potential DoD market for dish/Stirling technology and to identify the site for the demonstration, a survey of southwestern US military facilities was also conducted. This report describes the project history, the Cummins dish/Stirling system, results from the military market survey, and the field test results
Quantum Computing with Continuous-Variable Clusters
Continuous-variable cluster states offer a potentially promising method of
implementing a quantum computer. This paper extends and further refines
theoretical foundations and protocols for experimental implementation. We give
a cluster-state implementation of the cubic phase gate through photon
detection, which, together with homodyne detection, facilitates universal
quantum computation. In addition, we characterize the offline squeezed
resources required to generate an arbitrary graph state through passive linear
optics. Most significantly, we prove that there are universal states for which
the offline squeezing per mode does not increase with the size of the cluster.
Simple representations of continuous-variable graph states are introduced to
analyze graph state transformations under measurement and the existence of
universal continuous-variable resource states.Comment: 17 pages, 5 figure
Gender-based violence in Public Health: challenges and achievements
Este texto trata da violência contra mulheres (VCM) como objeto científico e prático da Saúde. É uma reflexão teórica crítica concernente a processos históricos que permitem ver tanto as convergências como os afastamentos entre a tomada dessa violência como questão e particularidades do campo da Saúde, produzindo conquistas e desafios atuais em especial para a Saúde Coletiva. O texto debate aspectos interdisciplinares desse objeto científico e suas implicações para a produção do conhecimento e para as ações em saúde. Considerando as distintas culturas científicas e práticas da Saúde e outros campos que já lidam com VCM, mostram-se tensões existentes entre a perspectiva da violência como questão da saúde e como fenômeno sociocultural, ampliadas com o acréscimo da abordagem de gênero. Produzem-se então desafios de diálogo entre esses campos em termos de paradigmas, modelos científicos e linguagens de cada qual; as necessidades de intervenção social em cada campo; e a relação distinta que cada um possui entre conhecimentos e intervenção social. De outro lado, mostram-se como convergências entre esses campos as conquistas relativas aos direitos humanos e sociais e a proposta de saúde integral. Conclui-se com algumas possíveis respostas aos desafios.This text deals with violence against women (VAW) as a scientific and practical object of Health. It is a theoretical and critical reflection related to historical processes that show convergences and distances between the approach of this violence as an issue and the health field particularities, creating contemporary conquests and challenges especially to Public Health. The text debates interdisciplinary aspects of this scientific object and some impacts to the knowledge production and to health actions. Considering the different scientific and practical cultures of Health and other fields that already deal with VAW, existing tensions between health perspective and violence as a socio-cultural phenomenon are showed, becoming critical when added the gender approach. Challenges are then created on dialogs between those fields in terms of: paradigms, scientific models and languages of each one; social intervention needs in every field; and the distinct relation between knowledge and social intervention presented in each field. On the other hand, the conquests related to human and social rights and the proposal of integral health are shown as convergences between these fields. To conclude, some possible answers to the challenges are considered
The Highly Miniaturised Radiation Monitor
We present the design and preliminary calibration results of a novel highly
miniaturised particle radiation monitor (HMRM) for spacecraft use. The HMRM
device comprises a telescopic configuration of active pixel sensors enclosed in
a titanium shield, with an estimated total mass of 52 g and volume of 15
cm. The monitor is intended to provide real-time dosimetry and
identification of energetic charged particles in fluxes of up to 10
cm s (omnidirectional). Achieving this capability with such a
small instrument could open new prospects for radiation detection in space.Comment: 17 pages, 15 figure
Towards universal quantum computation through relativistic motion
We show how to use relativistic motion to generate continuous variable Gaussian cluster states within cavity modes. Our results can be demonstrated experimentally using superconducting circuits where tuneable boundary conditions correspond to mirrors moving with velocities close to the speed of light. In particular, we propose the generation of a quadripartite square cluster state as a first example that can be readily implemented in the laboratory. Since cluster states are universal resources for universal one-way quantum computation, our results pave the way for relativistic quantum computation schemes
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