Lift-and-project ranks of the stable set polytope of joined a-perfect graphs

In this paper we study lift-and-project polyhedral operators defined by Lov?asz and Schrijver and Balas, Ceria and Cornu?ejols on the clique relaxation of the stable set polytope of web graphs. We compute the disjunctive rank of all webs and consequently of antiweb graphs. We also obtain the disjunctive rank of the antiweb constraints for which the complexity of the separation problem is still unknown. Finally, we use our results to provide bounds of the disjunctive rank of larger classes of graphs as joined a-perfect graphs, where near-bipartite graphs belong

Farmland Control Decisions under Different Intertemporal Risk Behavioral Constructs

Simulation-optimization techniques are employed to analyze changes in farmland control arrangements as a result of using different constructs of intertemporal risk behavior. Risk behavior based on constant absolute risk aversion (CARA) and constant relative risk aversion (CRRA) mean-standard deviation functions are used to achieve this objective. Specfically, a multi-period programming framework for a representative grain farm is developed to explore farmland control decisions under these two behavioral assumptions. Our results suggest that the use of a CRRA behavioral construct in analyzing farmland control decisions produce predictions that are more consistent with observed farm behavior.Farm Management,

Formation of liquid menisci in flexible nanochannels

This paper describes the elasto-capillary formation of menisci at the liquid-air interface in nanochannels that are covered with flexible capping membranes. The equilibrium between the capillary pressure in the fluid and the membrane bending results in a very peculiar shape of the meniscus. We present an analytical description of these meniscus hapes and show that the protrusion length of the meniscus along the channel is an accurate measure for the deflection of the nanochannels

OPPORTUNITY COSTS, SHARE LEASING, AND PREVENTED PLANTING CLAIMS IN CROP INSURANCE

This paper determines whether the opportunity costs of share leasing and the share amounts of farmers/tenants affect the likelihood of submitting a prevented planting claim. Results from our probit analysis shows that lower opportunity costs of share leasing and higher farmer/tenant share amount can increase the probability of submitting a prevented planting. These results have potential implications for setting prevented planting buy-up rates and crop insurance compliance procedures.Risk and Uncertainty,

Elastocapillary filling of deformable nanochannels

The capillary filling speed of wetting liquids of varying viscosity and surface tension in hydrophilic nanochannels with an elastic capping layer has been analyzed. The channels, with a height just below 80 nm, are suspended by a thin flexible membrane that easily deforms due to the negative pressure which develops behind the moving meniscus. In the elastocapillary filling of the channels, two opposite effects compete: the decreased cross channel sections increase the flow resistance, while the Laplace pressure that acts as the driving force becomes more negative due to the increased meniscus curvature. Although the meniscus position shows a square root of time behavior as described by the Washburn relation, the net result of the induced bending of the membranes is a definite increase of the filling speed. We propose a relatively straightforward model for this elastocapillary process and present experimental results of the filling speed of ethanol, water, cyclohexane and acetone that are found to be in good agreement with the presented model, for membrane deflections of up to 80 percent of the original channel height

The Impact of Labor Constraints on the Farm Performance

Stricter immigration policies that affect an estimated 12 million unauthorized immigrants, 40% of whom are hired as farm workers, can potentially leave the highly labor-dependent organic farms more economically vulnerable. The displacement of unauthorized immigrants will expectedly create labor shortages. This study analyzes the impact of hiring constraints and changes in farm labor market conditions (due to stricter immigration policies) on the technical efficiency and financial performance of organic and conventional farms. A production function approach is used to analyze survey data that has a mix of organic and conventional farms in the Southeast region. Adjustment strategies to deal with labor shortage and providing workers with nonwage incentives have been determined to be an important determinant of farm income. Among the strategies, adjustment of wage and nonwage benefits were found to be the most effective but a combination of strategies is the most preferred approach to deal with labor shortage. Furthermore, we found productivity difference between farmers with labor shortage adjustment strategies and those who do not.Agricultural Finance, Production Economics, Productivity Analysis,