Experimental study of the mechanics of the intra-aortic balloon

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.This thesis deals with the mechanics of the Intra-Aortic Balloon Pump (IABP), the most widely used temporary cardiac assist device, whose beneficial action is based on the principle of counterpulsation. The investigation is carried out in vitro in increasingly more realistic setups, including a mock circulatory system with physiological distribution of peripheral resistance and compliance in which IABP counterpulsation was simulated. Pressure and flow measurements show the effect of variables such as intra-luminal pressure, angle and aortic compliance on balloon hemodynamics. These data are complemented by results on the duration of balloon inflation and deflation obtained by means of high-speed camera visualisation. Furthermore, wave intensity analysis is carried out and it is identified as a possible alternative method for the assessment of IABP performance. This work includes two prototypes of intra-aortic balloons of novel shape with the balloon chamber tapering both from and toward the balloon tip. In clinical terms, with reference to the semi-recumbent position in which patients assisted with the IABP are nursed in the intensive care unit, the results presented in this thesis indicate that operating the balloon at an angle compromises the benefit of counterpulsation when assessed in vitro

The Silent revolution : the Roman army between Polybius and Marius

Traditionally, Polybius’ description of the Roman army in Book VI of his Histories is considered the de facto image of the mid-Republican Roman legions until the major changes introduced by the reforms attributed to Gaius Marius. However, there are several elements highlighting the fact that Polybius’ description actually depicts a rather outdated military system, making it hard to accept it as an up-to-date portrait of the army by the mid-second century. By examining hints within the sources, this paper aims to proper examine the major variations that interested the Roman military system from the mid-third to the late second centuries and to highlight their overall impact

La reforma de las elecciones: cambios en el sistema y en el procedimiento

Los cambios en los sistemas electorales resultan siempre complejos, porque dichos sistemas regulan la alternancia en el poder. Son, todavía, más difíciles en nuestro caso, ya que muchos de los elementos definitorios se encuentran recogidos en la propia Constitución. Este artículo parte de estas premisas y analiza algunas propuestas de reforma del sistema y del procedimiento electoral. Mientras que cambiar el primero es más complejo, porque puede generar resultados no previstos, modificar el segundo puede resultar menos gravoso, ya que las transformaciones afectan a todos por igual. Desde estas páginas se analizan tres asuntos principales, como son el voto de los españoles que viven en el extranjero, el uso obligatorio de la cabina electoral y algunos problemas inherentes al voto electrónicoChanging electoral systems is always difficult because they rule on the alternation of power. It is even more difficult in our case, because vital decisions on elections, such as districts and the number of seats that corresponds to each district, are stated in the Constitution. This paper departs from these premises and analyzes some reforms on the electoral system and the electoral process. It is possible to improve some elements of the first one, but always taking into account that each modification can generate unintended results. Changes in electoral process are easier, since they affect all political parties in the same way. The article analyzes three main issues: the vote of Spaniards living abroad, the need to impose the use of the voting booth and some problems inherent in electronic voting system

Intervención del legislador y selección de candidatos por los partidos politicos: una perspectiva comparada

This paper addresses the limits of public intervention in the selection of candidates by political parties. The issue is analyzed from the comparative perspective, although some documents of soft law adopted by the Venice Commission, OSCE, and ODIHR have also been taken into account. The study concludes that the legislation on political parties has increased in the last decade. However, the main constraints imposed on political parties do not come from specific legislation on political parties but from electoral laws. In some cases, the electoral laws impose a method of decision making on the nomination process since these laws require political parties compliance with the basic rules of the democratic principle. In other cases, the laws do not impose a method but a result, as in the case of case of the laws which impose quotas in favor of women. In any case, such measures should meet certain conditions to be effective. Firstly, the limits must respect the freedom of association proclaimed by international treaties and ensured by the ECHR; secondly, the requirements must be compatible with the electoral system; finally, any exigency on candidate selection must be guaranteed by monitoring systems and by sanctions for non-compliance.El presente trabajo aborda la posible densidad de la intervención pública a la hora de imponer a los partidos políticos procedimientos para la selección de candidatos. La óptica con la que se analiza el problema es, fundamentalmente, el derecho comparado, si bien se han utilizado también textos de «soft law» elaborados por la Comisión de Venecia, OSCE y ODHIR. En el mismo se concluye que, aunque la legislación sobre partidos políticos se ha incrementado en los últimos años, las mayores limitaciones impuestas a los partidos políticos no provienen de esta normativa específica sino de las leyes electorales. Dichas exigencias tienen una doble vertiente. En algunas ocasiones, se regula el método para la elección de candidatos, imponiendo a los partidos los requisitos inherentes a la toma de decisiones democráticas. En otras, se impone a los partidos un resultado, esto es, la presencia de candidatos de distinto sexo en las listas electorales. Cualquiera de estas medidas, para ser legítimas, tienen que respetar la libertad que corresponde a los partidos en cuanto asociaciones. Además, han de adaptarse al resto del sistema electoral y, especialmente, prever sistemas para verificar el cumplimiento de los requisitos impuestos por la ley.This paper addresses the limits of public intervention in the selection of candidates by political parties. The issue is analyzed from the comparative perspective, although some documents of soft law adopted by the Venice Commission, OSCE, and ODIHR have also been taken into account. The study concludes that the legislation on political parties has increased in the last decade. However, the main constraints imposed on political parties do not come from specific legislation on political parties but from electoral laws. In some cases, the electoral laws impose a method of decision making on the nomination process since these laws require political parties compliance with the basic rules of the democratic principle. In other cases, the laws do not impose a method but a result, as in the case of case of the laws which impose quotas in favor of women. In any case, such measures should meet certain conditions to be effective. Firstly, the limits must respect the freedom of association proclaimed by international treaties and ensured by the ECHR; secondly, the requirements must be compatible with the electoral system; finally, any exigency on candidate selection must be guaranteed by monitoring systems and by sanctions for non-compliance

Ciudadanía europea y legitimidad democrática

Producción Científic