Taxes in a simple wealth distribution model by inelastically scattering particles

In this work we use an inelastic scattering process of particles to propose a model able to reproduce the salient features of the wealth distribution in an economy by including taxes to each trading process and redistributing that collected among the population according to a given criterion. Additionally, we show that different optimal levels of taxes may exist depending on the redistribution criterion.Comment: 7 pages, 7 figure

An Experimental Study of Conventions and Norms

Although it is now recognized that norms play an important role in many economic decisions, compliance with conventions is generally considered to be driven by rational self-interest only. We report instead experimental data showing that (1) ‘external’ norms of fairness sustain social conventions that have emerged from repeated play of simple coordination games; and (2) with repetition such conventions acquire an ‘intrinsic’ normative power of their own. This creates pressure towards conformity, and patterns of regular behaviour that are far stronger and more stable than those that would be generated by mere self-interest and rationality.

Costless Discrimination and Unequal Achievements in a Labour Market Experiment

We investigate the emergence of discrimination in an experiment where individuals affiliated to different groups compete for a monetary prize, submitting independent bids to an auctioneer. The auctioneer receives perfect information about the bids (i.e. there is no statistical discrimination), and she has no monetary incentive to favour the members of her own group (the bidders are symmetric). We observe nonetheless some discrimination by auctioneers, who tend to assign the prize more frequently to a member of their own group when two or more players put forward the highest bid. Out-group bidders react to this bias and reduce significantly their bids, causing an average decay of their earnings throughout the game, with cumulative effects that generate strongly unequal outcomes. Because the initial bias is costless, such mechanism can survive even in competitive market, providing a rationale for a well-known puzzle in the literature, i.e. the long-run persistence of discrimination.discrimination, tournament, groups, experiment

Interactions within the turbulent boundary layer at high Reynolds number

Simultaneous streamwise velocity measurements across the vertical direction obtained in the atmospheric surface layer (Re_τ ≃ 5 × 10^5) under near thermally neutral conditions are used to outline and quantify interactions between the scales of turbulence, from the very-large-scale motions to the dissipative scales. Results from conditioned spectra, joint probability density functions and conditional averages show that the signature of very-large-scale oscillations can be found across the whole wall region and that these scales interact with the near-wall turbulence from the energy-containing eddies to the dissipative scales, most strongly in a layer close to the wall, z^+ ≲ 10^3. The scale separation achievable in the atmospheric surface layer appears to be a key difference from the low-Reynolds-number picture, in which structures attached to the wall are known to extend through the full wall-normal extent of the boundary layer. A phenomenological picture of very-large-scale motions coexisting and interacting with structures from the hairpin paradigm is provided here for the high-Reynolds-number case. In particular, it is inferred that the hairpin-packet conceptual model may not be exhaustively representative of the whole wall region, but only of a near-wall layer of z^+ = O(10^3), where scale interactions are mostly confined

Impact of atrial fibrillation on the cardiovascular system through a lumped-parameter approach

Atrial fibrillation (AF) is the most common arrhythmia affecting millions of people in the Western countries and, due to the widespread impact on the population and its medical relevance, is largely investigated in both clinical and bioengineering sciences. However, some important feedback mechanisms are still not clearly established. The present study aims at understanding the global response of the cardiovascular system during paroxysmal AF through a lumped-parameter approach, which is here performed paying particular attention to the stochastic modeling of the irregular heartbeats and the reduced contractility of the heart. AF can be here analyzed by means of a wide number of hemodynamic parameters and avoiding the presence of other pathologies, which usually accompany AF. Reduced cardiac output with correlated drop of ejection fraction and decreased amount of energy converted to work by the heart during blood pumping, as well as higher left atrial volumes and pressures are some of the most representative results aligned with the existing clinical literature and here emerging during acute AF. The present modeling, providing new insights on cardiovascular variables which are difficult to measure and rarely reported in literature, turns out to be an efficient and powerful tool for a deeper comprehension and prediction of the arrythmia impact on the whole cardiovascular system.Comment: 16 pages, 8 figures, 2 tables, Medical & Biological Engineering & Computing, 2014, Print ISSN: 0140-0118, Online ISSN: 1741-044

Mathematical modelling of cardiovascular fluid mechanics: physiology, pathology and clinical practice

The cardiovascular apparatus is a complex dynamical system that carries oxygen and nutrients to cells, removes carbon dioxide and wastes and performs several other tasks essential for life. The physically-based modelling of the cardiovascular system has a long history, which begins with the simple lumped Windkessel model by O. Frank in 1899. Since then, the development has been impressive and a great variety of mathematical models have been proposed. The purpose of this Thesis is to analyse and develop two different mathematical models of the cardiovascular system able to (i) shed new light into cardiovascular ageing and atrial fibrillation and to (ii) be used in clinical practice. To this aim, in-house codes have been implemented to describe a lumped model of the complete circulation and a multi-scale (1D/0D) model of the left ventricle and the arterial system. We then validate each model. The former is validated against literature data, while the latter against both literature data and numerous in-vivo non-invasive pressure measurements on a population of six healthy young subjects. Afterwards, the confirmed effectiveness of the models has been exploited. The lumped model has been used to analyse the effect of atrial fibrillation. The multi-scale one has been used to analyse the effect of ageing and to test the feasibility of clinical use by means of central-pressure blind validation of a parameter setting unambiguously defined with only non-invasive measurements on a population of 52 healthy young men. All the applications have been successful, confirming the effectiveness of this approach. Pathophysiology studies could include mathematical model in their setting, and clinical use of multi-scale mathematical model is feasible