A theoretical model of the endothelial cell morphology due to different waveforms

Endothelial cells are key units in the regulatory biological process of blood vessels. They represent an interface to transmit variations on the fluid dynamic changes. They are able to adapt its cytoskeleton, by means of microtubules reorientation and F-actin reorganization, due to new mechanical environments. Moreover, they are responsible for initiating a huge cascade of biological processes, such as the release of endothelins (ET-1), in charge of the constriction of the vessel and growth factors such as TGF-ß and PDGF. Although a huge efforts have been made in the experimental characterization and description of these two issues the computational modeling has not gained such an attention. In this work we study the 3D remodeling of endothelial cells based on the main features of blood flow. In particular we study how different oscillatory shear index and the time average wall shear stresses modify the endothelial cell shape. We found our model fitted the experimental works presented before in in vitro studies. We also include our model within a computational fluid dynamics simulation of a carotid artery to evaluate endothelial cell shape index which is a key predictor of atheroma plaque formation. Moreover, our approach can be coupled with models of collagen and smooth muscle cell growth, where remodeling and the associated release of chemical substance are involved.Peer ReviewedPostprint (author's final draft

A structural approach including the behavior of collagen cross-links to model patient-specific human carotid arteries

The final publication is available at Springer via http://dx.doi.org/10.1007/s10439-014-0995-7The objective of this work is to develop a remodeling model for biological matter coupling two different processes in a 3D framework: reorientation of the preferential direction of a given fibered structure and reorientation of the fibrils or filaments that make up such a structure. This work uses the microsphere-based approach to take into account the micro mechanics involved in biological fibered structures regarding both their passive behavior and the reorientation of their micro constituents. Moreover, the macro behavior of the material as a whole is obtained by means of homogenizing the underlying micro response. We associate the orientation space of the integration directions to the physical space of micro-fibrils. To approximate the directional distribution of the fibrils within each fiber bundle, a Bingham probability orientation density function is introduced into the Helmholtz energy function. With all these assumptions, the problem is studied from an energetic point of view, describing the dissipation inherent to remodeling processes, and the evolution equations for both reorientations (change in preferential direction of the network and change in shape of the fibril distribution) re obtained. The model is included in a finite element code which allows computing different geometries and boundary value problems. This results in a complete methodology for characterizing the reorientation evolution of different fibered biological structures, such as cells. Our results show remodeling of fibered structures in two different scales, presenting a qualitatively good agreement with experimental findings in cell mechanics. Hierarchical structures align in the direction of the maximum principal direction of the considered stimulus and narrow in the perpendicular direction. The dissipation rates follows predictable trends although there are no experimental findings to date for comparison. The incorporation of metabolic processes and an insight into cell-oriented mechano-sensing processes can help to overcome the limitations involved.Peer ReviewedPostprint (author's final draft

La adaptación de las agencias publicitarias al entorno digital : ¿Por qué hay agencias digitales? El caso del Reino Unido

Comunicaciones del IV Congreso Internacional sobre análisis fílmico celebrado en la Universitat Jaume I de Castellón 4,5 y 6 de mayo de 201

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Comunicaciones del IV Congreso Internacional sobre análisis fílmico celebrado en la Universitat Jaume I de Castellón 4,5 y 6 de mayo de 201

Health care provider choice in the case of patient-initiated contacts. An extended version of discrete choice of model demand

This paper analyzes the nature of health care provider choice in the case of patient-initiated contacts, with special reference to a National Health Service setting, where monetary prices are zero and general practitioners act as gatekeepers to publicly financed specialized care. We focus our attention on the factors that may explain the continuously increasing use of hospital emergency visits as opposed to other provider alternatives. An extended version of a discrete choice model of demand for patient-initiated contacts is presented, allowing for individual and town residence size differences in perceived quality (preferences) between alternative providers and including travel and waiting time as non-monetary costs. Results of a nested multinomial logit model of provider choice are presented. Individual choice between alternatives considers, in a repeated nested structure, self-care, primary care, hospital and clinic emergency services. Welfare implications and income effects are analyzed by computing compensating variations, and by simulating the effects of user fees by levels of income. Results indicate that compensating variation per visit is higher than the direct marginal cost of emergency visits, and consequently, emergency visits do not appear as an inefficient alternative even for non-urgent conditions.Health care demand, emergency visits, nested multinomial logit, compensating variation, time costs

Una Década de Frontex : ¿Hacia una gestión integrada de las fronteras marítimas de la Unión Europea?

Aquest treball pretén analitzar l'evolució del marc jurídic de la gestió de la cooperació i vigilància de les fronteres exteriors de la Unió Europea (UE) des de la perspectiva de les operacions a les fronteres marítimes.La pràctica de Frontex des dels seus inicis no ha estat mancada de crítiques, fet que ha comportat la necessitat de trobar nous mecanismes per aconseguir l'efectivitat de les seves operacions. És per aquest motiu que, com veurem en aquest treball, l'objectiu final de les reformes de l'Agència busquen assegurar la seguretat a l'espai interior del territori Schengen, sense deixar de banda el degut respecte als drets humans.Este trabajo pretende analizar la evolución del marco jurídico de la gestión de la cooperación y vigilancia de las fronteras exteriores de la Unión Europea (UE) desde la perspectiva de las operaciones en las fronteras marítimas.La práctica de Frontex desde sus inicios no ha estado carente de crítica, cosa que ha comportado la necesidad de encontrar nuevos mecanismos para conseguir la efectividad de sus operaciones. Es por este motivo que, como veremos en este trabajo, el objetivo final de las reformas de la Agencia busca asegurar la seguridad en el espacio interior del territorio Schengen, sin dejar de lado el debido respeto de los derechos humanos