Cryothermal Energy Ablation Of Cardiac Arrhythmias 2005: State Of The Art

At the time of antiarrhythmic surgery, cryothermal energy application by a hand-held probe was used to complement dissections and resections and permanently abolish the arrhythmogenic substrate. Over the last decade, significant engineering advances allowed percutaneous cryoablation based on catheters, apparently not very different from standard radiofrequency ablation catheters. Cryothermal energy has peculiar characteristics. In fact, it allows testing in a reversible way the effects of energy application at higher temperature, before producing a permanent lesion at –75°C. Moreover, slow formation of the lesion allows timely discontinuation of the application, as soon as inadvertent modifications of normal atrioventricular conduction are observed during ablation in the proximity of atrioventricular node and His bundle, avoiding its permanent damage. Over the last years, percutaneous cryothermal ablation has been widely used for a variety of cardiac arrhythmias. From the data gathered, it is unlikely that cryoablation will replace standard ablation in unselected cases. Nevertheless, for the above mentioned peculiarities, cryothermal ablation has proved very effective and safe for ablation of arrhythmogenic substrates close to the normal conduction pathways, becoming the first choice method to ablate anteroseptal and midseptal accessory pathways. It can be also the best treatment for ablation of the slow pathway to abolish atrioventricular node reentrant tachycardia in pediatrics or when particular anatomy of the Koch’s triangle is observed. Cryothermal ablation of the pulmonary veins for atrial fibrillation, although longer than radiofrequency ablation, is not associated with pulmonary vein stenosis and is expected to be less thrombogenic; new catheter designs for cryothermal ablation of this challenging arrhythmia are to be tested to assess their efficacy and clinical usefulness

Implementation, elimination of weakly dominated strategies and evolutionary dynamics

This paper is concerned with the realism of mechanisms that implement social choice functions in the traditional sense. Will agents actually play the equilibrium assumed by the analysis? As an example, we study the convergence and stability properties of Sj\"ostr\"om's (1994) mechanism, on the assumption that boundedly rational players find their way to equilibrium using monotonic learning dynamics and also with fictitious play. This mechanism implements most social choice functions in economic environments using as a solution concept the iterated elimination of weakly dominated strategies (only one round of deletion of weakly dominated strategies is needed). There are, however, many sets of Nash equilibria whose payoffs may be very different from those desired by the social choice function. With monotonic dynamics we show that many equilibria in all the sets of equilibria we describe are the limit points of trajectories that have completely mixed initial conditions. The initial conditions that lead to these equilibria need not be very close to the limiting point. Furthermore, even if the dynamics converge to the ``right'' set of equilibria, it still can converge to quite a poor outcome in welfare terms. With fictitious play, if the agents have completely mixed prior beliefs, beliefs and play converge to the outcome the planner wants to implement.Implementation, bounded rationality, evolutionary dynamics, mechanisms

The role of regulation in financing transport infrastructures in Italy

The paper discusses the present regulatory framework in Italy concerning transport infrastructures financing and provides some policy indications. The Italian situation is characterised by non homogeneity among the transport modes and insufficient, or even perverse, incentives to efficiency. Also, the norms promote the tendency to overinvestment and “gold plating” because applied within a weak planning framework. After a theoretical introduction to the financing mechanisms (public funding, PPP, price cap, etc.), the paper is structured by modes. For each infrastructure type (national roads, highways, railways, ports and airports), the most common funding practices are commented, underlining their characteristics, limits and implications. National roads and railways are financed by general budget on the basis of a planning activity usually carried by the agent itself. Conversely, highways, airports and ports are partially financed by fares under conditions of legal monopoly granted by concessions. However, the formulas for fares determination are questionable and sometimes provide incentives to overinvestment. The last section will provide recommendations for a more efficient regulation.regulation; investment; infrastructure; airports; roads; highways; railroads; price cap; ports; concession

IMPLEMENTATION, ELIMINATION OF WEAKLY DOMINATED STRATEGIES AND EVOLUTIONARY DYNAMICS

This paper studies convergence and stability properties of Sjöström's (1994) mechanism, under the assumption that boundedly rational players find their way to equilibrium using monotonic learning dynamics and best-reply dynamics. This mechanism implements most social choice functions in economic environments using as a solution concept one round of deletion of weakly dominated strategies and one round of deletion of strictly dominated strategies. However, there are other sets of Nash equilibria, whose payoffs may be very different from those desired by the social choice function. With monotonic dynamics, all these sets of equilibria contain limit points of the learning dynamics. Furthermore, even if the dynamics converge to the "right" set of equilibria (i.e. the one which contains the solution of the mechanism), it may converge to an equilibrium which is worse in welfare terms. In contrast with this result, any interior solution of the best-reply dynamics converges to the equilibrium whose outcome the planner desires.Implementation Theory, Evolutionary Dynamics

Deconstructing the eradication of new world screwworm in North America: retrospective analysis and climate warming effects.

Before its eradication from North America, the subtropical-tropical new world screwworm fly Cochliomyia hominivorax (Coquerel) invaded southwestern temperate areas of the U.S.A., where it caused myiasis in wildlife and livestock. Outbreaks of the fly occurred during years when adult migrants were carried northward on North American monsoon winds from the northern areas of Mexico and south Texas. We deconstruct, retrospectively, the biology and the effect of weather on the eradication of the fly in North America. Screwworm was found to be an ideal candidate for eradication using the sterile insect technique (SIT) because females mate only once, whereas males are polygynous, and, although it has a high reproductive potential, field population growth rates are low in tropical areas. In northern areas, eradication was enhanced by cool-cold weather, whereas eradication in tropical Mexico and Central America is explained by the SIT. Despite low average efficacy of SIT releases (approximately 1.7%), the added pressure of massive SIT releases reduced intrinsically low fly populations, leading to mate-limited extinction. Non-autochthonous cases of myiasis occur in North America and, if the fly reestablishes, climate warming by 2045-2055 will expand the area of favourability and increase the frequency and severity of outbreaks

Constraints on a strong X-ray flare in the Seyfert galaxy MCG-6-30-15

We discuss implications of a strong flare event observed in the Seyfert galaxy MCG-6-30-15 assuming that the emission is due to localized magnetic reconnection. We conduct detailed radiative transfer modeling of the reprocessed radiation for a primary source that is elevated above the disk. The model includes relativistic effects and Keplerian motion around the black hole. We show that for such a model setup the observed time-modulation must be intrinsic to the primary source. Using a simple analytical model we then investigate time delays between hard and soft X-rays during the flare. The model considers an intrinsic delay between primary and reprocessed radiation, which measures the geometrical distance of the flare source to the reprocessing sites. The observed time delays are well reproduced if one assumes that the reprocessing happens in magnetically confined, cold clouds.Comment: 4 pages, 2 figures, proceedings of a talk given at the symposium 238 at the IAU General Assembly 200

SOLOMON'S DILEMMA: AN EXPERIMENTAL STUDY ON DYNAMIC IMPLEMENTATION

This paper reports an experimental investigation on two mechanisms for the so-called King Solomon Dilemma, where one of them fails to implement the social choice rule dynamically. We compare the two mechanisms in terms of their welfare, incentive and learning properties.experiments, implementation, backward induction, bounded rationality

XMM-Newton unveils the type 2 nature of the BLRG 3C 445

We present an observation of XMM-Newton that unambiguously reveals the ``Seyfert 2'' nature of the Broad Line Radio Galaxy 3C 445. For the first time the soft excess of this source has been resolved. It consists of unobscured scattered continuum flux and emission lines, likely produced in a warm photoionized gas near the pole of an obscuring torus. The presence of circumnuclear (likely stratified) matter is supported by the complex obscuration of the nuclear region. Seventy percent of the nuclear radiation (first component) is indeed obscured by a column density ~4*10^{23} cm^{-2}, and 30 % (second component) is filtered by ~7* 10^{22} cm^{-2}. The first component is nuclear radiation directly observed by transmission through the thicker regions. The second one is of more uncertain nature. If the observer has a deep view into the nucleus but near the edge of the torus, it could be light scattered by the inner wall of the torus and/or by photoionized gas within the Broad Line Region observed through the thinner rim of the circumnuclear matter.Comment: MNRAS Letters, in pres