WATER QUALITY ISSUES FACING AGRICULTURE AND RURAL COMMUNITIES

Resource /Energy Economics and Policy,

ACCOUNTING FOR SPATIAL CHARACTERISTICS OF WATERSHEDS IN EVALUATING WATER POLLUTION ABATEMENT POLICIES

This study evaluates three agricultural nonpoint pollution abatement policies: regulating the spatial pattern of agricultural activities, ambient tax, and abatement tax/subsidy. All three policies incorporate spatial characteristics of agricultural emission loading and movement for an agricultural watershed in the Midwest. The effects of spatial variation in natural conditions and landscape features on agricultural emissions and crop yield are evaluated using a newly developed biophysical simulation model and experimental data. While the policies are equally cost effective in reducing agricultural nonpoint source pollution, their implementation feasibility is quite different.atrazine, environmental policy, nonpoint pollution, simulation, watershed management, water quality, Environmental Economics and Policy,

AN ANALYSIS OF NUTRIENT INTAKE FOR SELECTED FAMILIES IN FLORIDA'S EXPANDED NUTRITION PROGRAM

Food Consumption/Nutrition/Food Safety,

Bulk Mediated Surface Diffusion: The Infinite System Case

An analytical soluble model based on a Continuous Time Random Walk (CTRW) scheme for the adsorption-desorption processes at interfaces, called bulk-mediated surface diffusion, is presented. The time evolution of the effective probability distribution width on the surface is calculated and analyzed within an anomalous diffusion framework. The asymptotic behavior for large times shows a sub-diffusive regime for the effective surface diffusion but, depending on the observed range of time, other regimes may be obtained. Montecarlo simulations show excellent agreement with analytical results. As an important byproduct of the indicated approach, we present the evaluation of the time for the first visit to the surface.Comment: 15 pages, 7 figure

Bulk Mediated Surface Diffusion: Finite System Case

We address the dynamics of adsorbed molecules (a fundamental issue in surface physics) within the framework of a Master Equation scheme, and study the diffusion of particles in a finite cubic lattice whose boundaries are at the $z=1$ and the $z=L$ planes where $L = 2,3,4,...$, while the $x$ and $y$ directions are unbounded. As we are interested in the effective diffusion process at the interface $z = 1$, we calculate analytically the conditional probability for finding the system on the $z=1$ plane as well as the surface dispersion as a function of time and compare these results with Monte Carlo simulations finding an excellent agreement.Comment: 19 pages, 8 figure

The GL 569 Multiple System

We report the results of high spectral and angular resolution infrared observations of the multiple system GL 569 A and B that were intended to measure the dynamical masses of the brown dwarf binary believed to comprise GL 569 B. Our analysis did not yield this result but, instead, revealed two surprises. First, at age ~100 Myr, the system is younger than had been reported earlier. Second, our spectroscopic and photometric results provide support for earlier indications that GL 569 B is actually a hierarchical brown dwarf triple rather than a binary. Our results suggest that the three components of GL 569 B have roughly equal mass, ~0.04 Msun.Comment: 29 pages, 10 figures, accepted for publication in the Astrophysical Journal; minor corrections to Section 5.1; changed typo in 6.

MULTIPLE-OBJECTIVE DECISION MAKING FOR AGROECOSYSTEM MANAGEMENT

Multiple-objective decision making (MODEM) provides an effective framework for integrated resource assessment of agroecosystems. Two elements of integrated assessment are discussed and illustrated: (1) adding noneconomic objectives as constraints in an optimization problem; and (2) evaluating tradeoffs among competing objectives using the efficiency frontier for objectives. These elements are illustrated for a crop farm and watershed in northern Missouri. An interactive, spatial decision support system (ISDSS) makes the MODEM framework accessible to unsophisticated users. A conceptual ISDSS is presented that assesses the socioeconomic, environmental, and ecological consequences of alternative management plans for reducing soil erosion and nonpoint source pollution in agroecosystems. A watershed decision support system based on the ISDSS is discussed.Agribusiness,

Inestabilidad de placas plegadas prismáticas. Por el método de bandas finitas

El método de bandas finitas se emplea para determinar cargas de bifurcación de láminas plegadas prismáticas apoyadas en diafragmas en sus extremos. La formulación de estabilidad es de tipo energético y permite tratar tanto cargas sólidas como líquidas, incluyendo la influencia del movimiento de un líquido en modos de inestabilidad torsional. Se presentan ejemplos numéricos para evaluar convergencia de la solución y aplicaciones a problemas de inestabilidad torsional de vigas de pared delgada. Estudios paramétricos realizados sobre un ejemplo permiten comparar distintas formas de sección transversal en su comportamiento en pandeo.Peer Reviewe