2,458 research outputs found
Multiple Peril Crop Insurance
Multiple Peril Crop Insurance (MPCI) is a broad-based crop insurance program regulated by the U.S. Department of Agriculture and subsidized by the Federal Crop Insurance Corporation(FCIC). Crops eligible for MPCI coverage in Iowa include corn, sobyeans, oats, wheat, seed corn, popcorn, barley, potatoes, sweet corn, canning beans, dry beans, forages, grain sorghum, green peas, tomatoes, and nursery stocks. Not all of these crops can be insured in all counties.
Neuromechanical Simulation
The importance of the interaction between the body and the brain for the control of behavior has been recognized in recent years with the advent of neuromechanics, a field in which the coupling between neural and biomechanical processes is an explicit focus. A major tool used in neuromechanics is simulation, which connects computational models of neural circuits to models of an animal's body situated in a virtual physical world. This connection closes the feedback loop that links the brain, the body, and the world through sensory stimuli, muscle contractions, and body movement. Neuromechanical simulations enable investigators to explore the dynamical relationships between the brain, the body, and the world in ways that are difficult or impossible through experiment alone. Studies in a variety of animals have permitted the analysis of extremely complex and dynamic neuromechanical systems, they have demonstrated that the nervous system functions synergistically with the mechanical properties of the body, they have examined hypotheses that are difficult to test experimentally, and they have explored the role of sensory feedback in controlling complex mechanical systems with many degrees of freedom. Each of these studies confronts a common set of questions: (i) how to abstract key features of the body, the world and the CNS in a useful model, (ii) how to ground model parameters in experimental reality, (iii) how to optimize the model and identify points of sensitivity and insensitivity, and (iv) how to share neuromechanical models for examination, testing, and extension by others
Mutual Inhibition Among Neural Command Systems as a Possible Mechanism for Behavioral Choice in Crayfish
Mutual inhibition among behavioral command systems frequently has been suggested as a possible mechanism for switching between incompatible behaviors. Several neural circuits in crayfish that mediate incompatible behaviors have been found to interact through inhibition; this accounts for increased stimulus threshold of one behavior (e.g., escape tailflip) during performance of others (eating, walking, defense). To determine whether mutual inhibition between command systems can provide a mechanism that produces adaptive behavior, I developed a model crayfish that uses this mechanism to govern its behavioral choices in a simulated world that contains a predator, a shelter, and a food source. The crayfish uses energy that must be replaced by eating while it avoids capture by the predator. The crayfish has seven command systems (FORAGE, EAT, DEFENSE, RETREAT, ESCAPE, SWIM, HIDE) that compete through mutual inhibition for control of its behavior. The model crayfish was found to respond to changing situations by making adaptive behavioral choices at appropriate times. Choice depends on internal and external stimuli, and on recent history, which determines the pattern of those stimuli. The model’s responses are unpredictable: small changes in the initial conditions can produce unexpected patterns of behavior that are appropriate alternate responses to the stimulus conditions. Despite this sensitivity, the model is robust; it functions adaptively over a large range of internal and external parameter values
THE DEVELOPMENT OF GLOBAL EDUCATION POLICY: A CASE STUDY OF THE ORIGINS AND EVOLUTION OF EL SALVADOR'S EDUCO PROGRAM
The Education with Community Participation (EDUCO) program began in El Salvador in early 1991, near the end of the twelve-year civil war. It not only represented an extreme form of decentralization in that it transferred the responsibility for hiring, firing and supervising teachers to rural communities, but it was also the first reform of its kind in Latin America. During the ensuing 20 years, the program has received tremendous attention. Indeed, within the country it became the central program through which the education sector was rebuilt and expanded in the post-war era of the 1990s and 2000s. Internationally, the program has been widely recognized as a successful and desirable example of community-level education management decentralization. In fact, the program has become a "global education policy" in that it has been and continues to be recognized, promoted and adapted around the world.
To date, however, the majority of research on this program has been a-historical in nature and has focused narrowly on whether the program "worked" - statistically speaking and with regard to such outcomes as student achievement. In contrast, in this dissertation, I analyze the dynamics of how the policy was developed. I shed new light on the trajectory of the EDUCO program by focusing, from an international political economy framework, on how the program was developed, scaled up, and internationally promoted. In so doing, I am able to highlight relevant political economic structures that impinge on education reform, as well as the various mechanisms of transnational influence that contributed to its advancement within and beyond El Salvador. In a number of different ways, international organizations are central to the policy development process.
Methodologically, I focus not only on the process of development itself, but also on the ways in which actors and forces from multiple levels (local, national, international) interact and intersect in that process. Theoretically, by choosing to analyze EDUCO's origins, I attempt to contribute to our understanding of how (i.e., through which mechanisms of transnational influence) and why certain policies come into existence and subsequently go global
Gas Concentration Measurements in Underground Waste Storage Tanks
Currently over 100 underground tanks at the Hanford facility in eastern Washington state are being used to store high-level radioactive waste. With plans for a long-term nuclear-waste repository in Nevada in place (though not yet approved), one promising use for these underground storage tanks is as a temporary waystation for waste destined for the Nevada repository. However, without a reasonable understanding of the chemical reactions going on within the tanks, transporting waste in and out of the tanks has been deemed to be unsafe.
One hazard associated with such storage mechanisms is explosion of flammable gases produced within the tank. Within many of the storage tanks is a sludge layer. This layer, which is a mixture of liquid and solids, contains most of the radioactive material. Radioactive decay and its associated heat can produce several flammable materials within this layer. Two components of particular concern are hydrogen (H2) and nitrous oxide (N2O), since they are highly volatile in the gaseous phase. Though the tanks have either forced or natural convection systems to vent these gases, the possibility of an explosion still exists.
Measurements of these gases are taken in several ways. Continuous measurements are taken in the headspace, which is the layer between the tank ceiling and the liquid (supernatant) or sludge layer below. In tanks where a supernatant layer sits atop the sludge layer, there are often rollovers or gas release events (GREs), where a large chunk of sludge, after attaining a certain void fraction, becomes buoyant, rising through the supernatant and releasing its associated gas composition to the headspace. Such changes trigger a sensor, and thus measurements are also taken at that time.
Lastly, a retained gas sample (RGS) can be taken from either the supernatant or sludge layer. Such a core sample is quite expensive, but can yield crucial data about the way gases are being produced in the sludge and convected through the supernatant.
Unfortunately, the measurements from these three populations do not seem to match. In particular, the ratio r = [N2O]/[H2] varies from population to population. r also varies from tank to tank, but this can more readily be explained in terms of the waste composition of each tank. Since H2 is more volatile than N2O (and since there are more sources of oxygen in the headspace), lower values of r correspond to more hazardous situations.
This variance in r is troubling, since we need to be able to explain why certain values of r are lower (and hence more dangerous) in certain areas of the tank. In this report we examine the data from three tanks. We first verify that the differences in r among populations is significant. We then postulate several mechanisms which could explain such a difference
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