Sand transverse dune aerodynamics: 3D Coherent Flow Structures from a computational study

The engineering interest about dune fields is dictated by the their interaction with a number of human infrastructures in arid environments. Sand dunes dynamics is dictated by wind and its ability to induce sand erosion, transport and deposition. A deep understanding of dune aerodynamics serves then to ground effective strategies for the protection of human infrastructures from sand, the so-called sand mitigation. Because of their simple geometry and their frequent occurrence in desert area, transverse sand dunes are usually adopted in literature as a benchmark to investigate dune aerodynamics by means of both computational or experimental approaches, usually in nominally 2D setups. The present study aims at evaluating 3D flow features in the wake of a idealised transverse dune, if any, under different nominally 2D setup conditions by means of computational simulations and to compare the obtained results with experimental measurements available in literature

Rule of Law, Institutional Quality and Information

The focus of this paper is the analysis of the persistent lawlessness attitude observed in some transition and developing countries where an overall increase in the quality of institutions is recorded. The mechanism of information diffusion on institutional quality is explored using a model where the state confronts a continuum of agents prone to either strip assets or to invest. The model predicts that high uncertainty and potential sunk costs in a situation of rule of law enforcement push the economy towards anarchy, a Pareto-dominated equilibrium. Vice versa, if the assets' value and the cost of asset-stripping are high, this is instrumental to a rule of law enforcement, a Pareto-dominant equilibrium. High institutional quality can increase the likelihood of rule of law enforcement if there is enough information about the strength of institutions. On the other hand, if good institutions and good information about institutions do not come together, there is scope for the puzzled co-existence of advancement in reforms and poor property rights protection.rule of law, institutions, global games

Labor Market and Globalization: A Comparison of the Latin American and the East Asian Experiences in the 1980s and 1990s

In this paper we analyse the labor market and its relationship with globalization in two groups of countries similar in their GDP per capita levels at the beginning of the 1980s but otherwise significantly different in their economic and social structures. On the one hand we look at Argentina, Brazil and Chile, on the other hand we analyse South Korea, Taiwan and Thailand. It is argued that the Latin American group adopted pro-globalization policies too quickly and without an adequate social safety net, and that the East Asian group was particularly vulnerable to the 1997 crisis in connection with an ill-designed financial markets liberalisation and poor labor market policies. We suggest that the high social costs of labor market imbalances generated throughout the 1980s and 1990s in these two groups of countries should have been tackled within an encompassing development strategy, with an eye at social safety nets and labor supply policies – such as active and passive labor market institutions – designed for each country specifically.globalization, labor market, Latin America, East Asia

Unique Equilibrium in a Model of Rule of Law

This paper presents a model of Rule of Law in which a continuum of agents plays against the State for the appropriation of the economic assets of a stylised economy. The model shows how each agent can either challenge the State or acquiesce, with the latter having the choice of either protecting property rights or abandoning the economy to anarchy. Players' payoffs are affected by strategic complementarities, not only between State and agents but also among agents themselves. As a consequence of this, a Coordination Failure is generated. The solution of the game is given by two Pareto-ranked Nash equilibria emerging from the context. Introducing idiosyncratic information and sequential play generates a unique equilibrium, according to the global game approach. On the one hand, this model predicts that high uncertainty and sunk costs in law enforcement have a negative effect, pushing the economy towards a Pareto-dominated equilibrium. On the other hand, the high value given to the economy's assets (embedded social norms) has a positive influence, leading to a Pareto-dominant equilibrium.Rule of Law, Coordination Failure, Global Games

Speed of Transition, Unemployment Dynamics and Nonemployment Policies: Evidence from the Visegrad Countries

In Central and Eastern Europe the restructuring process of large state enterprises had the effect of increasing unemployment. Social policy expenditure, in particular nonemployment policies, grew faster then expected due to the need of financing the \textit{out of labor force} categories. The interactions among unemployment, speed of transition and nonemployment subsidies/pensions are studied taking into account the shrinking labor force during transition. The reallocation of workers from the state to the private sector imposed a heavy burden on the budget deficit due to the increased social policy expenditure. This combination of effects is captured by a model of the speed of transition, in which a non-constant labor force is considered as well as the opposition of the insiders to restructuring is accounted for. After the reforms of the so-called Passive Labor Market Policies (PLMPs) at the beginning of 1992, there was a slowing down of the transition and this is has not been yet completely explained by the Optimal Speed of Transition (OST) literature.Unemployment, Model of Transition, Social Safety Net

On the derived category of 1-motives

This is the final version of the 2007 preprint titled "On the derived category of 1-motives, I". It has been substantially expanded to contain a motivic proof of (two thirds of) Deligne's conjecture on 1-motives with rational coefficients, hence the new title. Compared to the 2007 preprint, the additions mainly concern an abstract theory of realisations with weight filtrations; Deligne's conjecture is tackled though them by an adjunction game.Comment: 242 pages - revised before acceptatio

On the derived category of 1-motives, I

We consider the category of Deligne 1-motives over a perfect field k of exponential characteristic p and its derived category for a suitable exact structure after inverting p. As a first result, we provide a fully faithful embedding into an etale version of Voevodsky's triangulated category of geometric motives. Our second main result is that this full embedding "almost" has a left adjoint, that we call \LAlb. Applied to the motive of a variety we thus get a bounded complex of 1-motives, that we compute fully for smooth varieties and partly for singular varieties. As an application we give motivic proofs of Roitman type theorems (in characteristic 0)

A note on relative duality for Voevodsky motives

Let X be an n-dimensional smooth proper variety over a field admitting resolution of singularities, and Y,Z two disjoint closed subsets of X. We establish an isomorphism M(X-Z,Y) isomorphic to M(X-Y,Z)^*(n)[2n] in Voevodsky's triangulated category of geometric motives. Here, M(X-Z,Y) is the motive of X -Z relative to its closed subset Y

Humans and dolphins: Decline and fall of adult neurogenesis

Pre-clinical research is carried out on animal models, mostly laboratory rodents, with the ultimate aim of translating the acquired knowledge to humans. In the last decades, adult neurogenesis (AN) has been intensively studied since it is viewed as a tool for fostering brain plasticity, possibly repair. Yet, occurrence, location, and rate of AN vary among mammals: the capability for constitutive neuronal production is substantially reduced when comparing small-brained, short living (laboratory rodents) and large-brained, long-living species (humans, dolphins). Several difficulties concerning scarce availability of fresh tissues, technical limits and ethical concerns did contribute in delaying and diverting the achievement of the picture of neurogenic plasticity in large-brained mammals. Some reports appeared in the last few years, starting to shed more light on this issue. Despite technical limits, data from recent studies mostly converge to indicate that neurogenesis is vestigial, or possibly absent, in regions of the adult human brain where in rodents neuronal addition continues into adult life. Analyses carried out in dolphins, mammals devoid of olfaction, but descendant of ancestors provided with olfaction, has shown disappearance of neurogenesis in both neonatal and adult individuals. Heterogeneity in mammalian structural plasticity remains largely underestimated by scientists focusing their research in rodents. Comparative studies are the key to understand the function of AN and the possible translational significance of neuronal replacement in humans. Here, we summarize comparative studies on AN and discuss the evolutionary implications of variations on the recruitment of new neurons in different regions and different species

From individual behaviour to an evaluation of the collective evolution of crowds along footbridges

This paper proposes a crowd dynamic macroscopic model grounded on microscopic phenomenological observations which are upscaled by means of a formal mathematical procedure. The actual applicability of the model to real world problems is tested by considering the pedestrian traffic along footbridges, of interest for Structural and Transportation Engineering. The genuinely macroscopic quantitative description of the crowd flow directly matches the engineering need of bulk results. However, three issues beyond the sole modelling are of primary importance: the pedestrian inflow conditions, the numerical approximation of the equations for non trivial footbridge geometries, and the calibration of the free parameters of the model on the basis of in situ measurements currently available. These issues are discussed and a solution strategy is proposed.Comment: 23 pages, 10 figures in J. Engrg. Math., 201