The Effect of Market Entry on Innovation: Evidence from UK University Incubators

This paper investigates the effect of market entry of new firms on incumbent firms' innovative activity measured as patent applications. The basic assumption is that the effect of entry varies by geographical distance between entrants and incumbents due to the presence of localized unobserved spillovers. In order to avoid endogeneity problems commonly associated with the timing of entry and entrants' location choice, I analyze entry induced by the establishment of university business incubators, which are usefully exogenous in time and space. The results show that entry has a statistically and economically significantly positive strategic effect on incumbent patenting which is attenuated by the geographical distance between entrant and incumbent.Patents, market entry, incubators, spillover

Interface dynamics in discrete forward-backward diffusion equations

We study the motion of phase interfaces in a diffusive lattice equation with bistable nonlinearity and derive a free boundary problem with hysteresis to describe the macroscopic evolution in the parabolic scaling limit. The first part of the paper deals with general bistable nonlinearities and is restricted to numerical experiments and heuristic arguments. We discuss the formation of macroscopic data and present numerical evidence for pinning, depinning, and annihilation of interfaces. Afterwards we identify a generalized Stefan condition along with a hysteretic flow rule that characterize the dynamics of both standing and moving interfaces. In the second part, we rigorously justify the limit dynamics for single-interface data and a special piecewise affine nonlinearity. We prove persistence of such data, derive upper bounds for the macroscopic interface speed, and show that the macroscopic limit can indeed be described by the free boundary problem. The fundamental ingredient to our proofs is a representation formula that links the solutions of the nonlinear lattice to the discrete heat kernel and enables us to derive macroscopic compactness results in the space of continuous functions.Comment: 34 pages, several figure

STRIPS: Science-Based Trials of Row Crops Integrated with Prairie Strips

Growing demand for agricultural products to supply food, feed, fiber, and fuel comes at a time of intensified pressure by the public as well as by local and federal government agencies to reduce the impacts of agricultural production on water quality and biodiversity. Midwest land under heavy agricultural production has been identified as a major contributor to nitrogen and phosphorus losses to downstream water systems and to hypoxia in the Gulf of Mexico

Second Order Approximations for Slightly Trimmed Sums

We investigate the second order asymptotic behavior of trimmed sums T_n=\frac 1n \sum_{i=\kn+1}^{n-\mn}\xin, where \kn, \mn are sequences of integers, 0\le \kn < n-\mn \le n, such that \min(\kn, \mn) \to \infty, as \nty, the \xin's denote the order statistics corresponding to a sample $X_1,...,X_n$ of $n$ i.i.d. random variables. In particular, we focus on the case of slightly trimmed sums with vanishing trimming percentages, i.e. we assume that \max(\kn,\mn)/n\to 0, as \nty, and heavy tailed distribution $F$, i.e. the common distribution of the observations $F$ is supposed to have an infinite variance. We derive optimal bounds of Berry -- Esseen type of the order $O\bigl(r_n^{-1/2}\bigr)$, r_n=\min(\kn,\mn), for the normal approximation to $T_n$ and, in addition, establish one-term expansions of the Edgeworth type for slightly trimmed sums and their studentized versions. Our results supplement previous work on first order approximations for slightly trimmed sums by Csorgo, Haeusler and Mason (1988) and on second order approximations for (Studentized) trimmed sums with fixed trimming percentages by Gribkova and Helmers (2006, 2007).Comment: 37 pages, to appear in Theory Probab. App

Extending field scale 4R nutrient management and wetland performance to watershed scale outcomes

Much of the U.S. Corn Belt is characterized by relative flat, poorly-drained areas which with extensive subsurface drainage, have become some of the most valuable and productive agricultural land in the world. However, this is not without consequences. Nitrate-N loss from these systems is of particular concern due to its potential adverse impacts on both public health and ecosystem function. In addition to the potential local impacts on receiving waters in the Corn Belt, nitrogen loads from the region are suspected as a primary contributor to hypoxia in the Gulf of Mexico. Iowa has long been a leader in balancing agricultural production and water quality concerns and in 2013 the Iowa Department of Agriculture and Land Stewardship released a nutrient reduction strategy in response the 2008 Gulf of Mexico Hypoxia Task Force Action Plan