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The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the basis of race, color, national origin, age, disability, and, where applicable, sex, marital status, familial status, parental status, religion, sexual orientation, genetic information, political beliefs, reprisal, or because all or a part of an individual's income is derived from any public assistance program. (Not all prohibited bases apply to all programs.) Persons with disabilities who require alternative means for communication of program information (Braille, large print, audiotape, etc.

Fluid substitution is an important part of seismic attribute work, because it provides the interpreter with a tool for modeling and quantifying the various fluid scenarios which might give rise to an observed amplitude variation with offset (AVO) or 4D response. The most commonly used technique for doing this involves the application of Gassmann's equations. Modeling the changes from one fluid type to another requires that the effects of the starting fluid first be removed prior to modeling the new fluid. In practice, the rock is drained of its initial pore fluid, and the moduli (bulk and shear) and bulk density of the porous frame are calculated. Once the porous frame properties are properly determined, the rock is saturated with the new pore fluid, and the new effective bulk modulus and density are calculated. A direct result of Gassmann's equations is that the shear modulus for an isotropic material is independent of pore fluid, and therefore remains constant during the fluid substitution process. In the case of disconnected or cracklike pores, however, this assumption may be violated. Once the values for the new effective bulk modulus and bulk density are calculated, it is possible to calculate the compressional and shear velocities for the new fluid conditions. There are other approaches to fluid substitution (empirical and heuristic) which avoid the porous frame calculations but, as described in this tutorial, often do not yield reliable results. This tutorial provides the reader with a recipe for performing fluid substitutions, as well as insight into why and when the approach may fail.

This study analyzes consumer purchasing behavior of organic fresh fruits and vegetables using the 2006 Nielsen Homescan panel. An ordered logit model was estimated to quantify the impacts of economic and socio-demographic factors on the probability of a household belonging to a specific organic user group-devoted, casual, or nonuser. Results suggest that price and income, to some extent, affect consumer purchases of organic produce. Additionally, the profile of an organic produce user is most likely to consist of an Hispanic household residing in the Western United States with children under 6 years old and a household head older than 54 years with at least a college degree.

This paper estimates the impact of U.S. school food programs on the distribution of child dietary quality during 2005−10. The distributional approach allows one to better understand how school food impacts children prone to low‐quality diets separately from those prone to higher‐quality diets. Using a fixed‐effects quantile estimator, I find notable heterogeneity in the general population—school food has positive impacts below the median of the dietary‐quality distribution, and negative but insignificant impacts at upper quantiles. Children demonstrating substantial nutritional needs (i.e., food insecure or receiving free/reduced price meals) exhibit positive impacts at all levels of diet quality with especially high benefits at low quantiles. Although school food programs may not benefit the “above‐average” child, they do improve the diets of the most nutritionally disadvantaged.