One-dimensional modelling of pulse wave propagation in human airway bifurcations in space-time variables

Airflow in the respiratory system is complicated as it goes through various regions with different geometries and mechanical properties. Three-dimensional (3-D) simulations are typically limited to local areas of the system because of their high computational cost. On the other hand, the one-dimensional (1-D) equations of flow in compliant tubes offer a good compromise between accuracy and computational cost when a global assessment of airflow in the system is required. The aim of the current study is to apply the 1-D formulation in space and time variables to study the propagation of a pulse wave in human airways; first in a simple system composed of just one bifurcation, trachea-main bronchi, according to the symmetrical Weibel model. Then extending the system to include a further generation, the bronchi branches. Pulse waveforms carry information about the functionality and morphology of the respiratory system and the 1-D modelling, in terms of space and time variables, represents an innovative approach for respiratory response interpretation. 1-D modelling in space-time variables has been extensively applied to simulate blood pressure and flow in the cardiovascular system. This work represents the first attempt to apply this formulation to study pulse waveforms in the human bronchial tree

Modelos no asociativos en genética de poblaciones

El objetivo de esta charla es, en primer lugar, dar una visi on general de algunos de los modelos no asociativos m as com unmente utilizados en gen etica de poblaciones para, a continuaci on, describir las llamadas co algebras con realizaci on gen etica que aparecen en el estudio de las distribuciones an- cestrales de determinadas poblaciones gen eticas. Entre las cuestiones a tratar se incluir an, entre otras, la descripci on asint otica de los sistemas gen eticos representados mediante las mencionadas co algebras gen eticas, as como los resultados que sobre su estructura alge- braica pueden obtenerse v a su representaci on mediante trigrafos orientados.Universidad de Málaga, Campus de Excelencia Internacional Andalucia Tech

Extension of the BRIEF descriptor for color images and its evaluation in robotic applications.

During the development of the project, new extensions of the BRIEF descriptor are defined based in the use of color information in different color spaces. They are evaluated against each other and the original BRIEF descriptor (that uses intensity pixel values in grayscale images) by means of a matching test of different points of two different images of the same scene. The selected extension is used to recognize objects in a real time robotic application by means of a classification method. Therefore, the target is to improve the BRIEF descriptor to be applicable in color images by defining the different color extensions and making a comparative evaluation to ensure selecting the best one that most improve the basic BRIEF descriptor with the use of color information. The speed and the recognition rate are computed for every extension and the basic BRIEF to compare the performance of each descriptor. Ones an extension is selected, it is used the Bag Of Features model to create an algorithm able to recognize objects. The BOF model detects the keypoints with the FAST algorithm, describes them by means of the selected extension of the BRIEF descriptor and classifies them using a linear Support Vector Machine. Finally, the algorithm is tested in different situations and conditions, varying illumination, a little bit rotation and background, and checking performance with occluded object

Newtonian Flow in Converging-Diverging Capillaries

The one-dimensional Navier-Stokes equations are used to derive analytical expressions for the relation between pressure and volumetric flow rate in capillaries of five different converging-diverging axisymmetric geometries for Newtonian fluids. The results are compared to previously-derived expressions for the same geometries using the lubrication approximation. The results of the one-dimensional Navier-Stokes are identical to those obtained from the lubrication approximation within a non-dimensional numerical factor. The derived flow expressions have also been validated by comparison to numerical solutions obtained from discretization with numerical integration. Moreover, they have been certified by testing the convergence of solutions as the converging-diverging geometries approach the limiting straight geometry.Comment: 23 pages, 5 figures, 1 table. This is an extended and improved version. arXiv admin note: substantial text overlap with arXiv:1006.151

Computational assessment of hemodynamics-based diagnostic tools using a database of virtual subjects: Application to three case studies

AbstractMany physiological indexes and algorithms based on pulse wave analysis have been suggested in order to better assess cardiovascular function. Because these tools are often computed from in-vivo hemodynamic measurements, their validation is time-consuming, challenging, and biased by measurement errors.Recently, a new methodology has been suggested to assess theoretically these computed tools: a database of virtual subjects generated using numerical 1D-0D modeling of arterial hemodynamics. The generated set of simulations encloses a wide selection of healthy cases that could be encountered in a clinical study.We applied this new methodology to three different case studies that demonstrate the potential of our new tool, and illustrated each of them with a clinically relevant example: (i) we assessed the accuracy of indexes estimating pulse wave velocity; (ii) we validated and refined an algorithm that computes central blood pressure; and (iii) we investigated theoretical mechanisms behind the augmentation index.Our database of virtual subjects is a new tool to assist the clinician: it provides insight into the physical mechanisms underlying the correlations observed in clinical practice

Parametric uncertainty analysis of pulse wave propagation in a model of a human arterial network

Accepted versio

Resolución aproximada de sistemas lineales con retardos puntuales usando series de Taylor

Este trabajo presenta un método aproximado -basado en la representación por series de Taylor y en la teoría de los operadores asociados de integración y retardo- para obtener soluciones analíticas de sistemas lineales con varias variables de estado y de control y múltiples retardos puntuales externos e internos. Se presentan varios ejemplos numéricos donde se muestran las mejoras en exactitud que proporciona este método frente a otros.Peer Reviewe