Portuguese Population in France: a snapshot 25 years after their arrival

In year 2000 Portugal is celebrating the 500th anniversary of the arrival to Brazil. The Portuguese overseas adventure is now five centuries old and more than one third of the Portuguese nationals are living outside their homeland; in France they are the largest foreign community. This paper uses the data from the French Employment Survey (Enqujte de l Emploi) 1994 and 1995 to characterise the Portuguese population and to study individual decisions taken by the Portuguese migrants concerning naturalisation, family, residence and education. As a result of the analysis it seems that the decisions of the younger Portuguese are getting closer to the decisions of their French neighbours, increasing the gap with respect to the decisions of their countrymen who stayed in Portugal. In this very sense, we can say that some assimilation by the Portuguese is occurring in France. There is an educational convergence of the Portuguese migrants in France and the French.

Rheology of fractal networks

We model the cytoskeleton as a fractal network by identifying each segment with a simple Kelvin-Voigt element, with a well defined equilibrium length. The final structure retains the elastic characteristics of a solid or a gel, which may support stress, without relaxing. By considering a very simple regular self-similar structure of segments in series and in parallel, in 1, 2 or 3 dimensions, we are able to express the viscoelasticity of the network as an effective generalised Kelvin-Voigt model with a power law spectrum of retardation times, $\cal L\sim\tau^{\alpha}$. We relate the parameter $\alpha$ with the fractal dimension of the gel. In some regimes ($0<\alpha<1$), we recover the weak power law behaviours of the elastic and viscous moduli with the angular frequencies, $G'\sim G''\sim w^\alpha$, that occur in a variety of soft materials, including living cells. In other regimes, we find different power laws for $G'$ and $G''$.Comment: 5 pages, 3 figure

Simple thermodynamics of jet engines

We use the first and second laws of thermodynamics to analyze the behavior of an ideal jet engine. Simple analytical expressions for the thermal efficiency, the overall efficiency, and the reduced thrust are derived. We show that the thermal efficiency depends only on the compression ratio r and on the velocity of the aircraft. The other two performance measures depend also on the ratio of the temperature at the turbine to the inlet temperature in the engine, T-3/T-i. An analysis of these expressions shows that it is not possible to choose an optimal set of values of r and T-3/T-i that maximize both the overall efficiency and thrust. We study how irreversibilities in the compressor and the turbine decrease the overall efficiency of jet engines and show that this effect is more pronounced for smaller T-3/T-i

Human Capital Concentration and the Place-Based Policies in Chile

Chile is one of the most concentrated country in the world. Most of the 40 percent of the population live in the capital city, Santiago, where around 45 percent of the GDP is produced. At the same time, most of the policies promoting welfare are focus on people and they are spatially blind. This paper shows how the current array keeps concentrating people, especially with potential high human capital, around Santiago, and assesses whether this happened for difference in quality of life and opportunities or difference in the quality of the universities. The data available on individuals, who end the high school and take the university admission test, that lets students applying to the university and program that they wish to go, allows identifying the region of origin of the students, the region where the university that they apply is located and where they were selected. Three programs are chosen for this study given the quantity of people that apply to them and because they are available across different cities in the country are pedagogy, engineering and physician. In addition, in Chile they are more than 60 universities, however only the traditional 25 are the one that use this selection system for the period of this study that goes from 2006 to 2009. Recently some new universities have get into the system. Assuming that most of the students end up working around the city where they got the degree, we use an aggregate discrete choice model to develop a methodology that consist in following the destination of the students who got the best scores in the university admission test. Those students can choose any university in the country, and the majority prefers to go to those in the capital city. Contrasting with these results, lower scores have an inverse pattern. When we test if it is explained by the difference in the quality of life between cities versus the differences among the quality of the universities, the former has a larger explanatory power, which bring back the discussion if the policy should be oriented to place or people. It means, that will not be enough focus on increase the quality of the universities across the territories to attract better student to universities outside Santiago. It will need and strong complementary policies making those cities more interesting for the potential high human capital applicant

The BTZ black hole as a Lorentz-flat geometry

It is shown that 2+1 dimensional anti-de Sitter spacetimes are Lorentz-flat. This means, in particular, that any simply-connected patch of the BTZ black hole solution can be endowed with a Lorentz connection that is locally pure gauge. The result can be naturally extended to a wider class of black hole geometries and point particles in three-dimensional spacetime.Comment: 2 page