Biodiversity has long been a source of wonder and scientific curiosity. Theoretically, the co-occurrence of competitive species requires niche differentiation, and such differences are well known; however, the neutral theory, which assumes the equivalence of all individuals regardless of the species in a biological community, has successfully recreated observed patterns of biodiversity. In this...

Label each edge of a graph with a group element. Call the labels gains, and call the graph with this labeling a gain graph. A group expansion of an ordinary graph is an example of a gain graph. To construct one, replace each edge of a graph by several edges, one bearing as gain each possible value in a group. We introduce the concept of a group expansion of a gain graph. Then we find a formula ...

Does cutting red tape foster entrepreneurship in industries with the potential to expand? We address this question by combining the time needed to comply with government entry procedures in 45 countries with industry-level data on employment growth and growth in the number of establishments during the 1980s. Our main empirical finding is that countries where it takes less time to register new b...

Monolithically integrated four-channel distributed feedback (DFB) laser array has been fabricated by metal organic vapor phase epitaxy (MOVPE) selective area growth for 1.55μm coarsewavelength division multiplexing (CWDM) systems. Wide-stripe MOVPE selective area growth and electron-beam lithography are used to obtain wide CWDM channel spacing of 20 nm. Optical outputs from the simultaneously b...

The number of participants in the SSI program grew by 1.1 million from 1987 to 1993. This paper examines the role of Medicaid on the SSI participation decision. I use the rapid growth in average Medicaid expenditure as a proxy for its value. OLS estimates of Medicaid's effect may be biased because of omitted variables bias and measurement error. I therefore apply two-stage least squares to esti...