Fronts from complex two-dimensional dispersal kernels: theory and application to Reid's paradox

Bimodal dispersal probability distributions with characteristic distances differing by several orders of magnitude have been derived and favorably compared to observations by Nathan [Nature (London) 418, 409 (2002)]. For such bimodal kernels, we show that two-dimensional molecular dynamics computer simulations are unable to yield accurate front speeds. Analytically, the usual continuous-space random walks (CSRWs) are applied to two dimensions. We also introduce discrete-space random walks and use them to check the CSRW results (because of the inefficiency of the numerical simulations). The physical results reported are shown to predict front speeds high enough to possibly explain Reid's paradox of rapid tree migration. We also show that, for a time-ordered evolution equation, fronts are always slower in two dimensions than in one dimension and that this difference is important both for unimodal and for bimodal kernels

Rational Partisan Theory with fiscal policy and an independent central bank

The empirical evidence testing the validity of the rational partisan theory (RPT) has been mixed. In this article, we argue that the inclusion of other macroeconomic policies and the presence of an independent central bank can partly contribute to explain this inconclusiveness. This article expands Alesina s (1987) RPT model to include an extra policy and an independent central bank. With these extensions, the implications of RPT are altered signi ficantly. In particular, when the central bank is more concerned about output than public spending (an assumption made by many papers in this literature), then the direct relationship between in flation and output derived in Alesina (1987) never holds. Keywords: central bank, conservativeness, political uncertainty. JEL Classi fication: E58, E63.

The Big Band Theory : català col·loquial i humor científic. Proposta de traducció del capítol pilot

Aquest treball elabora una proposta de traducció per al doblatge del capítol pilot de The Big Bang Theory, que combina llenguatge col•loquial i llenguatge científic.L’objectiu és doble: elaborar un llenguatge col•loquial creïble però a la vegada genuí i emprar els equivalents catalans adequats per als termes científics originals.

Variations publicitaires sur le genre : une analyse linguistique des représentations publicitaires du féminin et du masculin

Résumé:¦Sur le plan économique, le système de genre est une pierre angulaire du discours publicitaire. Il intervient dans la segmentation des marchés, la sélection des médias et des supports, l'apparence extérieure des produits, le ton des campagnes, le choix des arguments de vente et, bien sûr, les scripts des annonces. En contrepartie, sur le plan symbolique, le discours publicitaire est un dépositaire privilégié des imaginaires de genre qui circulent dans son contexte de diffusion. En cette qualité, confronté à un marché toujours plus concurrentiel, à l'instabilité croissante des consommateurs ainsi qu'à une critique médiatique, académique et publique à l'affût des stéréotypes, le discours publicitaire est amené à proposer des représentations des hommes et des femmes de plus en plus diversifiées. Le présent ouvrage, qui relève de l'analyse linguistique des discours, rentre dans la complexité de ces variations publicitaires sur le féminin et le masculin et déchiffre les imaginaires de genre dont elles relèvent. Il soulève par ailleurs la question de la dimension politique des recherches académiques.

Capital, Wages, and Growth: Theory and Evidence

Returns to scale to capital and the strength of capital externalities play a key role for the empirical predictions and policy implications of different growth theories. We show that both can be identified with individual wage data and implement our approach at the city-level using US Census data on individuals in 173 cities for 1970, 1980, and 1990. Estimation takes into account fixed effects, endogeneity of capital accumulation, and measurement error. We find no evidence for human or physical capital externalities and decreasing aggregate returns to capital. Returns to scale to physical and human capital are around 80 percent. We also find strong complementarities between human capital and labor and substantial total employment externalities.

Measurement with Some Theory: a New Approach to Evaluate Business Cycle Models

We propose a method to evaluate cyclical models which does not require knowledge of the DGP and the exact empirical specification of the aggregate decision rules. We derive robust restrictions in a class of models; use some to identify structural shocks and others to evaluate the model or contrast sub-models. The approach has good size and excellent power properties, even in small samples. We show how to examine the validity of a class of models, sort out the relevance of certain frictions, evaluate the importance of an added feature, and indirectly estimate structural parameters.