Fluctuations of the partial filling factors in competitive RSA from binary mixtures

Competitive random sequential adsorption on a line from a binary mix of incident particles is studied using both an analytic recursive approach and Monte Carlo simulations. We find a strong correlation between the small and the large particle distributions so that while both partial contributions to the fill factor fluctuate widely, the variance of the total fill factor remains relatively small. The variances of partial contributions themselves are quite different between the smaller and the larger particles, with the larger particle distribution being more correlated. The disparity in fluctuations of partial fill factors increases with the particle size ratio. The additional variance in the partial contribution of smaller particle originates from the fluctuations in the size of gaps between larger particles. We discuss the implications of our results to semiconductor high-energy gamma detectors where the detector energy resolution is controlled by correlations in the cascade energy branching process.Comment: 19 pages, 8 figure

Time scale of random sequential adsorption

A simple multiscale approach to the diffusion-driven adsorption from a solution to a solid surface is presented. The model combines two important features of the adsorption process: (i) the kinetics of the chemical reaction between adsorbing molecules and the surface; and (ii) geometrical constraints on the surface made by molecules which are already adsorbed. The process (i) is modelled in a diffusion-driven context, i.e. the conditional probability of adsorbing a molecule provided that the molecule hits the surface is related to the macroscopic surface reaction rate. The geometrical constraint (ii) is modelled using random sequential adsorption (RSA), which is the sequential addition of molecules at random positions on a surface; one attempt to attach a molecule is made per one RSA simulation time step. By coupling RSA with the diffusion of molecules in the solution above the surface the RSA simulation time step is related to the real physical time. The method is illustrated on a model of chemisorption of reactive polymers to a virus surface

Do regional payroll tax reductions boost employment?

Using a Difference-in-Differences approach we evaluate the effects of a 10 percentage points reduction in the payroll tax introduced in 2002 for firms in the northern part of Sweden. We find no employment effects for existing firms and can rule out that a 1 percentage point payroll tax reduction would increase employment with more than 0.2 percent. We do, however, find that tax reductions have significantly positive effects on the average wage bill per employee. These are likely to be driven by higher average wages, but might also be due to more hours worked. As a sensitivity check we investigate if reduced payroll taxes affect the likelihood of firm entry and exit, and find some support for a net firm inflow. Our attempts to assess concomitant effects on employment indicate that payroll tax reductions might yield increases in employment through the start-up of new firms.Payroll tax; Labour demand; Incidence; Firm entry/exit; Difference-in-Differences

Cell shape analysis of random tessellations based on Minkowski tensors

To which degree are shape indices of individual cells of a tessellation characteristic for the stochastic process that generates them? Within the context of stochastic geometry and the physics of disordered materials, this corresponds to the question of relationships between different stochastic models. In the context of image analysis of synthetic and biological materials, this question is central to the problem of inferring information about formation processes from spatial measurements of resulting random structures. We address this question by a theory-based simulation study of shape indices derived from Minkowski tensors for a variety of tessellation models. We focus on the relationship between two indices: an isoperimetric ratio of the empirical averages of cell volume and area and the cell elongation quantified by eigenvalue ratios of interfacial Minkowski tensors. Simulation data for these quantities, as well as for distributions thereof and for correlations of cell shape and volume, are presented for Voronoi mosaics of the Poisson point process, determinantal and permanental point processes, and Gibbs hard-core and random sequential absorption processes as well as for Laguerre tessellations of polydisperse spheres and STIT- and Poisson hyperplane tessellations. These data are complemented by mechanically stable crystalline sphere and disordered ellipsoid packings and area-minimising foam models. We find that shape indices of individual cells are not sufficient to unambiguously identify the generating process even amongst this limited set of processes. However, we identify significant differences of the shape indices between many of these tessellation models. Given a realization of a tessellation, these shape indices can narrow the choice of possible generating processes, providing a powerful tool which can be further strengthened by density-resolved volume-shape correlations.Comment: Chapter of the forthcoming book "Tensor Valuations and their Applications in Stochastic Geometry and Imaging" in Lecture Notes in Mathematics edited by Markus Kiderlen and Eva B. Vedel Jense

The Causal Effects of an Industrial Policy

Business support policies designed to raise productivity and employment are common worldwide, but rigorous micro-econometric evaluation of their causal effects is rare. We exploit multiple changes in the area-specific eligibility criteria for a major program to support manufacturing jobs ("Regional Selective Assistance"). Area eligibility is governed by pan-European state aid rules which change every seven years and we use these rule changes to construct instrumental variables for program participation. We match two decades of UK panel data on the population of firms to all program participants. IV estimates find positive program treatment effect on employment, investment and net entry but not on TFP. OLS underestimates program effects because the policy targets underperforming plants and areas. The treatment effect is confined to smaller firms with no effect for larger firms (e.g. over 150 employees). We also find the policy raises area level manufacturing employment mainly through significantly reducing unemployment. The positive program effect is not due to substitution between plants in the same area or between eligible and ineligible areas nearby. We estimate that "cost per job" of the program was only $6,300 suggesting that in some respects investment subsidies can be cost effective.industrial policy, regional policy, employment, investment, productivity

The Causal Effects of an Industrial Policy

Business support policies designed to raise productivity and employment are common worldwide, but rigorous micro-econometric evaluation of their causal effects is rare. We exploit multiple changes in the area-specific eligibility criteria for a major program to support manufacturing jobs (“Regional Selective Assistance”). Area eligibility is governed by pan-European state aid rules which change every seven years and we use these rule changes to construct instrumental variables for program participation. We match two decades of UK panel data on the population of firms to all program participants. IV estimates find positive program treatment effect on employment, investment and net entry but not on TFP. OLS underestimates program effects because the policy targets underperforming plants and areas. The treatment effect is confined to smaller firms with no effect for larger firms (e.g. over 150 employees). We also find the policy raises area level manufacturing employment mainly through significantly reducing unemployment. The positive program effect is not due to substitution between plants in the same area or between eligible and ineligible areas nearby. We estimate that “cost per job” of the program was only $6,300 suggesting that in some respects investment subsidies can be cost effective.