Neurons in early visual cortex respond to both luminance- (1st order) and contrast-modulated (2nd order) local features in the visual field. In later extra-striate areas neurons with larger receptive fields integrate information across the visual field. For example, local luminance-defined features can be integrated into contours and shapes. Evidence for the global integration of features defin...

background one of the requirements of the osun state smoke-free legislation is to ensure smoke-free enclosed and partially enclosed workplaces. this survey was conducted to assess the knowledge and attitude of workers in indoor bars, beer parlors and discotheques to smoke-free legislation in general and the osun state smoke-free law in particular.   methods a convenience sampling of 36 hospital...

We study two novel decoupled energy-law preserving numerical schemes for solving the CahnHilliard-Darcy (CHD) system which models two-phase flow in porous medium or in a Hele-Shaw cell. In the first scheme, the velocity in the Cahn-Hilliard equation is treated explicitly so that the Darcy equation is completely decoupled from the Cahn-Hilliard equation. In the second scheme, an intermediate vel...

Abstract We construct a tractable neoclassical growth model that generates Pareto’s law of income distribution and Zipf’s law of firm size distribution from idiosyncratic, firm-level productivity shocks. CEOs invest in risk-free assets as well as their own firms’ risky stocks, through which their assets and incomes depend on firm-level shocks. Using the model, we evaluate how changes in tax rat...

There is a famous, or perhaps infamous would be more accurate, book by Zipf (1949) called Human Behavior and the Principle of Least Effort which offers a vast panoply of examples of the applicability of the Pareto law, including examples in linguistics, music and demography. Hill (1974) offers an interpretation in terms of the so-called Bose-Einstein model in which balls are allocated to cells ...

Several authors (Berry 1970, Krugman 1996 or Eaton and Eckstein 1997, among many others) have experienced amazement about the accurate functioning of the law of “least effort” established by Zipf (1949) in most places. Cities, ranked by population, seem to follow almost exactly a log/log function, in which the logarithm of the "mass" (population, density, number of employees, etc.) correlates a...

We extend the basic Schumpeterian endogenous growth model by allowing incumbents to undertake innovations to improve their products, while entrants engage in more “radical” innovations to replace incumbents. Our model provides a tractable framework for the analysis of growth driven by both entry of new firms and productivity improvements by continuing firms. The model generates a non-degenerate...

Existing explanations of Zipf’s law (Pareto exponent approximately equal to 1) in size distributions require strong assumptions on growth rates or the minimum size. I show that Zipf’s law naturally arises in general equilibrium when individual units solve a homogeneous problem (e.g., homothetic preferences, constant-returns-to-scale technology), the units appear and disappear at a small constan...

Two classical hypotheses are examined about the population growth in a system of cities : Hypothesis 1 pertains to Gibrat’s and Zipf’s theory which states that the city growth-decay process is size independent; Hypothesis 2 pertains to the so called Yule process which states that the growth of populations in cities happens when (i) the distribution of the city population initial size obeys a lo...