A Note on Adult Overwintering of Dasymutilla Nigripes in Michigan (Hymenoptera: Mutillidae)

Excerpt: Although Dasymutilla nigripes (Fabricius) is one of the more common Michigan velvet ant species, little is known about its life cycle. In his summary of mutillid life cycles, Michel (1928) indicated that mutillids of northern latitudes probably overwinter in the prepupal stage within the subterranean cells of their hymenopterous hosts. Bohart and McSwain (1939) cited prepupal overwintering as normal for Dasymutilla sackenii (Cresson) in California. However, Potts and Smith (1944), also working in California, collected overwintering adult female Dasymutilla aureola pacifica (Cresson)

Polynomial treewidth forces a large grid-like-minor

Robertson and Seymour proved that every graph with sufficiently large treewidth contains a large grid minor. However, the best known bound on the treewidth that forces an $\ell\times\ell$ grid minor is exponential in $\ell$. It is unknown whether polynomial treewidth suffices. We prove a result in this direction. A \emph{grid-like-minor of order} $\ell$ in a graph $G$ is a set of paths in $G$ whose intersection graph is bipartite and contains a $K_{\ell}$-minor. For example, the rows and columns of the $\ell\times\ell$ grid are a grid-like-minor of order $\ell+1$. We prove that polynomial treewidth forces a large grid-like-minor. In particular, every graph with treewidth at least $c\ell^4\sqrt{\log\ell}$ has a grid-like-minor of order $\ell$. As an application of this result, we prove that the cartesian product $G\square K_2$ contains a $K_{\ell}$-minor whenever $G$ has treewidth at least $c\ell^4\sqrt{\log\ell}$.Comment: v2: The bound in the main result has been improved by using the Lovasz Local Lemma. v3: minor improvements, v4: final section rewritte

Creative Careers: The Life Cycles of Nobel Laureates in Economics

This paper studies life cycle creativity among Nobel laureate economists. We identify two distinct life cycles of scholarly creativity. Experimental innovators work inductively, accumulating knowledge from experience. Conceptual innovators work deductively, applying abstract principles. We find that conceptual innovators do their most important work earlier in their careers than experimental laureates. For instance, our estimates imply that the probability that the most conceptual laureate publishes his single best work peaks at age 25 compared to the mid-50s for the most experimental laureate. Thus while experience benefits experimental innovators, newness to a field benefits conceptual innovators.

The Effects of Direct Foreign Investment on Local Communities

The large increase in direct foreign investment (DFI) into the United States in the late 1980s has generated considerable research on why these flows occurred and where these foreign firms located. However, very little has been done to evaluate the impact these foreign firms have on the local communities in which they locate. As a first step in addressing this topic, we use detailed county-level panel data from South Carolina across 5 year intervals from 1980 through 1995 to investigate the effect of foreign manufacturing firms on local labor markets and on the level and distribution of local government budgets. We find that manufacturing employment by foreign firms has a substantial impact on industry wages and county budgets which is significantly different from domestic manufacturing employment. With respect to wages, we find that while increased manufacturing employment generally increases county wages in an average two-digit industry, this effect is more than seven times larger when the employment growth comes from a foreign firm, rather than a domestic one. On the budget side, we find that foreign employment leads to larger declines in per capita revenues and expenditures at the county level, and to significant redistribution of county expenditures away from public school funding and toward transportation and public safety.

Observing The Hidden Sector

We study the effects of renormalization due to hidden-sector dynamics on observable soft supersymmetry-breaking parameters in the minimal supersymmetric extension of the Standard Model (MSSM), under various hypotheses about their universality at a high input scale. We show that hidden-sector renormalization effects may induce the spurious appearance of unification of the scalar masses at some lower scale, as in mirage unification scenarios. We demonstrate in simple two-parameter models of the hidden-sector dynamics that the parameters may in principle be extracted from experimental measurements, rendering the hidden sector observable. We also discuss the ingredients that would be necessary to carry this programme out in practice.Comment: 38 pages, 13 figures, uses UApreprint.cls and subfigure.sty (included

Genetic Information in Agricultural Productivity and Product Development

A prominent facet of recent changes in agriculture has been the advent of precision breeding techniques. Another has been an increase in the level of information inputs and outputs associated with agricultural production. This paper identifies ways in which these features may complement in expanding the variety of processed products, the level of productivity, and the rate of change in productivity. Using a martingale concept of ﾓmore information,ﾔ we identify conditions under which more information increases the incentives to invest and engage in product differentiation. A theory on how genetic uniformity can enhance the rate of learning through process experimentation, and so the rate of technical change, is also developed.experimentation, genetics, information, martingale, sorting, uniformity, value added.