Search for Gravitational Waves from Primordial Black Hole Binary Coalescences in the Galactic Halo

We use data from the second science run of the LIGO gravitational-wave detectors to search for the gravitational waves from primordial black hole (PBH) binary coalescence with component masses in the range 0.2--$1.0 M_\odot$. The analysis requires a signal to be found in the data from both LIGO observatories, according to a set of coincidence criteria. No inspiral signals were found. Assuming a spherical halo with core radius 5 kpc extending to 50 kpc containing non-spinning black holes with masses in the range 0.2--$1.0 M_\odot$, we place an observational upper limit on the rate of PBH coalescence of 63 per year per Milky Way halo (MWH) with 90% confidence.Comment: 7 pages, 4 figures, to be submitted to Phys. Rev.

Restored Agricultural Wetlands in central Iowa: Habitat Quality and Amphibian Response

Amphibians are declining throughout the United States and worldwide due, partly, to habitat loss. Conservation practices on the landscape restore wetlands to denitrify tile drainage effluent and restore ecosystem services. Understanding how water quality, hydroperiod, predation, and disease affect amphibians in restored wetlands is central to maintaining healthy amphibian populations in the region. We examined the quality of amphibian habitat in restored wetlands relative to reference wetlands by comparing species richness, developmental stress, and adult leopard frog (Lithobates pipiens) survival probabilities to a suite of environmental metrics. Although measured habitat variables differed between restored and reference wetlands, differences appeared to have sub-lethal rather than lethal effects on resident amphibian populations. There were few differences in amphibian species richness and no difference in estimated survival probabilities between wetland types. Restored wetlands had more nitrate and alkaline pH, longer hydroperiods, and were deeper, whereas reference wetlands had more amphibian chytrid fungus zoospores in water samples and resident amphibians exhibited increased developmental stress. Restored and reference wetlands are both important components of the landscape in central Iowa and maintaining a complex of fish-free wetlands with a variety of hydroperiods will likely contribute to the persistence of amphibians in this landscape

The effect of railroads and price responsiveness on acreage decisions in the post-Bellum period

This study analyses the effect of farmers' price responsiveness and railroad development on acreage decisions in the late 19th century. A potential simultaneity between these determinants was mentioned in some earlier studies, but never examined. This study sheds some light on these relationships by employing a simultaneous equations model. The results show that acreage, prices and railroad mileage were jointly determined in the late nineteenth century. Furthermore, farmers were very responsive to wheat prices in their wheat acreage decisions in the eastern and northeastern regions when endogeneity effect is considered. In the western and southern regions, however, farmers were not responsive to wheat prices in their wheat acreage decisions. On the other hand, they were very responsive to corn and animal prices in their corn acreage decisions. Railroads were one important determinant that affected farmers' acreage decisions positively in every region.

On the multiplicity of solutions in generation capacity investment models with incomplete markets: a risk-averse stochastic equilibrium approach

Investment in generation capacity has traditionally been evaluated by computing the present value of cashflows accruing from new equipment in a market with globally optimized capacity mix. The competition and risk that now prevail in the sector may require a more refined analysis. We consider a competitive market with agents investing in some mix of capacities: the risk exposure of a plant and the attitude towards risk of the owner depend on the plant and the portfolio of its capacities. They may also depend on hedging contracts acquired by the investor on the market if such contracts exist. We represent these effects through equilibrium models of generation capacity in incomplete markets. The models come in different versions depending on the portfolio of physical plants and hedging contracts. These modify the long-term risk of the plants, the attitude of the owners towards risk, and hence the incentive to invest. The models involve risk-averse producers and consumers, and their behavior is represented by convex risk measures. We use degree theory to prove existence and explore multiplicity of equilibrium solutions