Fractal Analysis of Cardiovascular Signals Empowering the Bioengineering Knowledge

The cardiovascular system is composed of a complex network of vessels, where highly uniform hierarchical branching structures are regulated by the anatomy and local flow requirements. Arteries bifurcate many times before they become capillaries where the scaling factor of vessel length, diameter and angle between two children branches is established at each level of recurrence. This behaviour can be easily described using a fractal scaling principle. Moreover, it was observed that the basic pattern of blood distribution is also fractal, imposed both by the anatomy of the vascular tree and the local regulation of vascular tone. In this chapter, arterial physiology was analysed, where waveform complexity of arterial pressure time series was related to arterial stiffness changes, pulse pressure variations and the presence wave reflection. Fractal dimension was used as a nonlinear measure, giving place to a ‘holistic approach of fractal dimension variations throughout the arterial network’, both in health and disease

Informational Time Causal Planes: A Tool for Chaotic Map Dynamic Visualization

In the present chapter, we made a detailed analysis of the different regimes of certain chaotic systems and their correspondence with the change in the normalized Shannon entropy, Statistical Complexity, and Fisher information measure. We construct a bidimensional plane composed of the selection of a pair of the informational tools mentioned above (a casual plane is defined), in which the different dynamical regimes appeared very clear and give more information of the underlying process. In such a way, a plane composed of the normalized Shannon entropy, statistical complexity, normalized Shannon entropy, and Fisher information measure can be applied to follow the changes in the behavior variations of the nonlinear systems

Analysis of ischaemic crisis using the informational causal entropy-complexity plane

In the present work, an ischaemic process, mainly focused on the reperfusion stage, is studied using the informational causal entropy-complexity plane. Ischaemic wall behavior under this condition was analyzed through wall thickness and ventricular pressure variations, acquired during an obstructive flow maneuver performed on left coronary arteries of surgically instrumented animals. Basically, the induction of ischaemia depends on the temporary occlusion of left circumflex coronary artery (which supplies blood to the posterior left ventricular wall) that lasts for a few seconds. Normal perfusion of the wall was then reestablished while the anterior ventricular wall remained adequately perfused during the entire maneuver. The obtained results showed that system dynamics could be effectively described by entropy-complexity loops, in both abnormally and well perfused walls. These results could contribute to making an objective indicator of the recovery heart tissues after an ischaemic process, in a way to quantify the restoration of myocardial behavior after the supply of oxygen to the ventricular wall was suppressed for a brief period.Fil: Legnani, Walter. Universidad Tecnológica Nacional. Facultad Regional Buenos Aires; Argentina. Universidad Nacional de Lanús; ArgentinaFil: Traversaro Varela, Francisco. Instituto Tecnológico de Buenos Aires; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Redelico, Francisco Oscar. Hospital Italiano; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Quilmes; ArgentinaFil: Cymberknop, Leandro Javier. Instituto Tecnologico de Buenos Aires. Departamento de Bioingenieria; Argentina. Universidad Tecnológica Nacional. Facultad Regional Buenos Aires; ArgentinaFil: Armentano, Ricardo Luis. Universidad Tecnológica Nacional. Facultad Regional Buenos Aires; Argentina. Instituto Tecnologico de Buenos Aires. Departamento de Bioingenieria; ArgentinaFil: Rosso, Osvaldo Aníbal. Universidad de los Andes; Chile. Universidade Federal de Alagoas; Brasil. Hospital Italiano; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Fundamentos y propuestas para impulsar un Programa Institucional que potencie el Impacto Social del Conocimiento en la Universidad Tecnológica Nacional

El presente artículo refleja los fundamentos y propuestas para impulsar un Programa Institucional que potencie el impacto social del conocimiento en la Universidad Tecnológica Nacional diseñado a fin de cumplir con los requerimientos del plan de mejora en el que se ha comprometido la universidad. El artículo está organizado en cuatro apartados. En el primero se analiza la emergencia del conocimiento en la sociedad contemporánea, en el segundo se contextualiza y se da cuenta brevemente del origen de la Universidad Tecnológica Nacional y el marco y los aspectos centrales de su forma de concebir la producción de conocimiento. En una tercera sección se conceptualiza el impacto social y los abordajes teóricos que dan sustento a dicha categoría. Por último se establecen las propuestas para el fortalecimiento del impacto social en la Universidad Tecnológica Nacional.This paper discusses the concept of social impact of knowledge in the context of the management of higher education institutions. Taking into account the experience of the authors in the design of an institutional program for the National Technological University (UTN), the text addresses first the broader problem of knowledge production in contemporary society and then analyzes the concept of knowledge impact and how this notion can be incorporated in the management of universities. The article highlights the importance of learning from experiences om other countries, as well as the need to adapt them to the particularities of the local university system, and in particular to the challenges of a university focused in engineering. Finally, we describe our proposal for the creation of an institutional program that enhances the social impact of knowledge at UTN.Fil: Naidorf, Clara Judith. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Mazzola, Carlos Francisco. Universidad Nacional de San Luis; ArgentinaFil: Vasen, Federico. Universidad de Buenos Aires. Facultad de Ciencias Sociales; ArgentinaFil: Legnani, Walter. Universidad Tecnológica Nacional. Facultad Regional Buenos Aires; ArgentinaFil: Napoli, Fernando Pablo. Universidad Tecnológica Nacional. Facultad Regional Buenos Aires; Argentin

The Apidulcis study

Optimal duration of anticoagulation in patients with a first venous thromboembolism (VTE) is still uncertain. Extended anticoagulant treatment beyond the first 3 to 6 months is recommended in patients with unprovoked VTE for their high risk of recurrence, provided the risk of bleeding during anticoagulation is not high. Recent meta-analyses indicated that only one-third of these patients have a recurrence 10 years after anticoagulation is stopped, whereas the risk of major bleeding is consistent and persistent during anticoagulation. We designed the prospective, multicenter Apidulcis study to test whether serial D-dimer measurements, using commercial assays with predefined sex-specific cutoffs (350 ng/mL and 500 ng/mL for men and women, respectively, for assays expressing results as fibrinogen equivalent units), may be useful to stratify patients for the risk of recurrence. Those presenting positive D-dimer results, considered at higher risk, will receive low dose Apixaban, 2.5 mg tablets BID for 18 months, whereas those with persistently negative D-dimer results, considered at lower risk, will remain without anticoagulant treatment. Outpatients with a first VTE (unprovoked or associated with weak risk factors), aged 18 to 74 years, who have already received anticoagulation for at least 12 months are eligible for the study

Modelling of dynamic perturbations of the Austral polar vortex over Antarctica and south America

El objetivo de esta tesis es mostrar la influencia de perturbaciones de escala sinóptica (de longitudes o escalas menores a 5000 km. aproximadamente) sobre el vórtice polar austral y sobre el agujero de ozono antártico. Estas perturbaciones se propagan desde la tropósfera y alcanzan la estratósfera inferior. Por este motivo se realizó un estudio de la presencia de perturbaciones sinópticas y sus características a distintas alturas para comprender su estructura vertical. Para realizar este análisis se diseñaron filtros espectrales bidimensionales en el espacio cuya función fue permitir el estudio por separado de los efectos de las diferentes perturbaciones en función de sus propiedades de onda. En este sentido se trabajó con valores diarios de forma tal de retener las posibles contribuciones no lineales en el tiempo. Se evaluaron las condiciones de penetración / propagación en la estratósfera inferior de los sistemas sinópticos y se estudió su impacto sobre la dinámica del vórtice polar y el agujero de ozono. Para ello se empleó un seguimiento de la dinámica del agujero de ozono en base a la evolución dinámica de la altura geopotencial y su participación en la deformación del sistema en análisis. Para completar el estudio se implementó un modelo de aguas poco profundas cuasitrídimensional que integra en forma espectral, mediante armónicos de Hough, las ecuaciones de movimiento, escritas en coordenadas isentrópicas. Esta metodología de integración numérica proveyó al modelo de un elevado rendimiento computacional, ya que la base espectral seleccionada fue la de autofunciones del operador de aguas poco profundas, de tal forma que no se hizo necesario el mapeo de la esfera para la resolución del sistema de ecuaciones. Este modelo posee una frontera inferior dada por la posición de la tropopausa y una superior libre, es decir, que constituye un problema clásico de aguas poco profundas con fondo móvil. El modelo es de tipo mecanístico y es forzado (mediante el ingreso de condiciones de contorno) por los valores de la temperatura de tropopausa, extraídos a partir de datos del ECMWF (European Centre for Medium Range Weather Forecasting). Este proceso requirió técnicas precisas de interpolación y de procesado de bases de datos para acoplar con el debido tiempo de integración el resto del modelo. Para establecer las condiciones iniciales del modelo al momento de realizar las integraciones de estudio se diseñó una integración previa de “warm up” hasta alcanzar condiciones dinámicas y termodinámicas de la atmósfera, apropiadas con la fecha del inicio de la integración propuesta en el experimento. También fue necesario ajustar el diseño de una capa de esponja en el contorno superior del modelo para evitar que se inestabilizara. A su vez se le añadió difusividad selectiva en la horizontal y la vertical para evitar que las perturbaciones de menor escala fuesen amortiguadas numéricamente. Para validar el modelo se tomó un caso de estudio comprendido entre los meses de octubre y noviembre de 1990 comparando los resultados del mismo con datos independientes del Goddard Space Flight Center de NASA (vorticidad potencial), y del National Oceanic and Atmospheríc Administration (NOAA), E.E.U.U. (vientos y temperatura). El modelo reprodujo estas condiciones con alta fidelidad. Los resultados del modelo convalidan los resultados observacionales sobre la contribución de los procesos de escala sinóptica en la deformación y evolución del vórtice polar y del agujero de ozono. En síntesis, la confirmación del aporte de perturbaciones de escala sinóptica en la deformación del vórtice polar constituye un novedoso aporte en el conocimiento de los mecanismos que participan en la evolución dinámica de este último. Dicho resultado es consolidado por un extenso estudio observacional y un modelo teórico, que incluye importantes implementaciones en modelado fisico-computacional, que lo respaldan.The aim of this thesis is to demonstrate the influence of synoptic scale disturbances (with scale under 5000 km approximately), upon the southern polar vortex and the Antarctic ozone hole. These perturbations propagate from the troposphere and reach the lower stratosphere. In order to verify this a study was carried on to determine the presence and characterisation of synoptic perturbations at different heights so as to understand their vertical structure. Such an analysis required the design of bidimensional spectral filters in space. Their function was to separate the perturbations as a function of their wave properties and thus allow their separate study. Daily values were used so as to preserve the non-linear time relationships. The conditions for penetration/propagation of these system into the lower stratosphere were evaluated. The impact of such synoptic systems upon the vortex and ozone hole dynamics was then analysed. Geopotential height dynamics was used to follow the ozone hole dynamics. In order to complete the study, a quasi 3-dimensional shallow water model was implemented. The model integrates spectrally, with Hough's harmonics, the motion equations, written in isentropic coordinates. This numeric integration methodology provided the model with a high computational performance, since the selected spectral base corresponded to the shallow water eigenfuntions. Thus it was not necessary to generate a special grid for the equation system resolution. This model has a lower boundary determined by the tropopause and a free upper boundary. It thus constitutes a classic shallow water problem with mobile bed. It is a mechanistic model and is forced by the boundary conditions given by the tropopause temperature, obtained from the ECWMF (European Centre for Medium Range Weather Forecasting) . This process required precise interpolation and data processing techniques to couple the boundary conditions to the model with the appropriate timing. A "warm-up" integration was implemented to establish the model dynamic and thermodynamic initial conditions for a given date. It was also necessary to calibrate the design of a sponge layer for the upper boundary so as to avoid model instabilities. Furthermore selective horizontal and vertical diffusitivity were added to avoid the numerical damping of the lower scale perturbations. A case study covering the months of October and November 1990 was chosen to validate the model, by comparing model outputs with independent data from NASA's Goddard Space Flight Center (potential vorticity) and NOAA (wind and temperatures). The model was able to faithfully reproduce these observations. The model results agree with the observational results on the contribution of synoptic scale processes to the polar vortex and ozone hole evolution and deformation. Summing up, the confirmation of the synotic scale perturbation contribution to the polar vortex deformation is itself a new result towards the understanding of the mechanisms involved in the dynamics of this phenomenon. Such result is supported by a detailed observational analysis and a theortetical model that includes important contributions towards the improvement of physical computational modelling.Fil:Legnani, Walter E.. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina

Influence of the signal to noise ratio for the estimation of Permutation Entropy

In this paper, the influence of signal to noise ratio in the estimation of Permutation Entropy was studied upon signals obtained by simulations of a chaoticdeterministic system. Then, using a bootstrap scheme, we applied hypothesistests to detect noise in a signal computing the Permutation Entropy. Similarly to recent publications, we found that as the content of noise increases (i.e. the signal to noise ratio decreases), three clearly different dynamics appear: dominant deterministic, deterministic noisy and dominant noisy. To discriminate the limits of these zones, another hypothesis test was applied. Finally, we also show that if a hypothesis test detects changes in the value of Permutation Entropy, it is due to changes in the actual dynamics of the system and not due to thepresence of noise in the signal.Fil: Traversaro Varela, Francisco. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Oficina de Coordinacion Administrativa Houssay. Instituto de Medicina Traslacional E Ingenieria Biomedica. - Hospital Italiano. Instituto de Medicina Traslacional E Ingenieria Biomedica. - Instituto Universitario Hospital Italiano de Buenos Aires. Instituto de Medicina Traslacional E Ingenieria Biomedica.; ArgentinaFil: Legnani, Walter. Universidad Tecnológica Nacional; ArgentinaFil: Redelico, Francisco Oscar. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Oficina de Coordinacion Administrativa Houssay. Instituto de Medicina Traslacional E Ingenieria Biomedica. - Hospital Italiano. Instituto de Medicina Traslacional E Ingenieria Biomedica. - Instituto Universitario Hospital Italiano de Buenos Aires. Instituto de Medicina Traslacional E Ingenieria Biomedica.; Argentin

100 years of surface weather observations at Orcadas Antartic Station: a look at variability and change in the Antartic Peninsula

100 years of surface temperature, pressure and precipitation at Argentine Antartic Station Orcadas (60\ub045'S / 44\ub043'W) on Laurie Island (Orcadas del Sur Archipelago) located off the tip of the Antarctic Peninsula are studied in order to determine variability and change in the region.spanning the period 1905-2003, i.e. the longest Antartic climatic timeseries available. The timeseries were deseasonalized, using an additive timeseries model. The annual mean cycle was thus obtained and subtracted from the data tus obtaining the anomaly series. Then using wavelet filters the variability and trends of the anomaly time series were calculated. Orthogonal and iorthogonal wavelets, which compose a filter bank with minimal phase change, were used. The trend results thus obtained are iindependent of the wavelet base considered. Furthermore this approach does not make any hypothesis on the stationality of the timeseries . The overall trends obtained agree well with other trend estimates made by NOAA and IPCC/WMO. A temperature increase of the order of 2°C is found for the overall simple. It is interesting to note the seasonality of trends and as well as the onset of a significant warming at Orcadas since the 1970s. Variability in the temperature timeseries shows interannual and interdecadic changes. Precipitation analysis yields a positive trend of about 2.1%. These results will be discussed under the light of the possible influences of GHG and ozone depletion.Pages: 195-19

A Novel Interpretation for Arterial Pulse Pressure Amplification in Health and Disease

International audienceArterial pressure waves have been described in one dimension using several approaches, such as lumped (Windkessel) or distributed (using Navier-Stokes equations) models. An alternative approach consists of modeling blood pressure waves using a Korteweg-de Vries (KdV) equation and representing pressure waves as combinations of solitons. This model captures many key features of wave propagation in the systemic network and, in particular, pulse pressure amplification (PPA), which is a mechanical biomarker of cardiovascular risk. The main objective of this work is to compare the propagation dynamics described by a KdV equation in a human-like arterial tree using acquired pressure waves. Furthermore, we analyzed the ability of our model to reproduce induced elastic changes in PPA due to different pathological conditions. To this end, numerical simulations were performed using acquired central pressure signals from different subject groups (young, adults, and hypertensive) as input and then comparing the output of the model with measured radial artery pressure waveforms. Pathological conditions were modeled as changes in arterial elasticity (E). Numerical results showed that the model was able to propagate acquired pressure waveforms and to reproduce PPA variations as a consequence of elastic changes. Calculated elasticity for each group was in accordance with the existing literature