6,364 research outputs found

    FARM LEVEL DYNAMIC ANALYSIS OF SOIL CONSERVATION: AN APPLICATION TO THE PIEDMONT AREA OF VIRGINIA

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    A conceptual optimal control theory model which considers farm level decision making with respect to soil management is developed. A simplified version of the theoretical model is applied to the Piedmont area of Virginia. The model includes the productivity impacts of both soil erosion and technological progress. Both the theoretical model and its empirical application are improvements over previous efforts. Results suggest that farmers in the study area can achieve substantial reductions in soil erosion by adopting alternative farming practices.Farm Management,

    THE INFLUENCE OF TECHNOLOGICAL PROGRESS ON THE LONG RUN FARM LEVEL ECONOMICS OF SOIL CONSERVATION

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    The complementary interaction between topsoil depth and technical progress for winter wheat in the Palouse region was found to strengthen the long run payoff to conservation tillage. Nonetheless, conservation tillage was found to be competitive with conventional tillage only if its current yield disadvantages were eliminated. Conservation tillage was relatively more competitive on shallower topsoils and for longer planning horizons. Short-term subsidies coupled with research directed towards reducing the cost and yield disadvantages of conservation tillage in the Palouse were advocated to maintain long-term soil productivity.Land Economics/Use, Research and Development/Tech Change/Emerging Technologies,

    Health and Environmental Benefits of Reduced Pesticide Use in Uganda: An Experimental Economics Analysis

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    Two experimental procedures were employed to value both health and environmental benefits from reducing pesticide use in Uganda. The first experiment, an incentive compatible auction involved subjects with incomplete information placing bids to avoid consuming potentially contaminated groundnuts/water in a framed field experimental procedure. Three experimental treatments (information, proxy good, and group treatments) were used. Subjects were endowed with a monetary amount (starting capital) equivalent to half the country’s per capita daily income (in small denominations). Two hundred and fifty seven respondents were involved in a total of 35 experimental sessions in Kampala and Iganga districts. The Kampala sample consisted of urban (professional) residents while the Iganga sample consisted of rural (groundnut farmer) residents. Analyses with Tobit models indicated that subjects are willing to pay significant amounts to avoid ill health outcomes, although these values vary by region, by treatment and by socio-economic characteristics. Gender differences were important in explaining bid behavior, with male respondents in both study areas bidding higher to avoid ill health outcomes than females. Consistent with a priori expectation, rural population’s average willingness to pay to avoid ill health outcomes was lower (by 11.4 percent) than the urban population’s willingness to pay perhaps reflecting the poverty level/low incomes in the rural areas and how it translates into reduced regard for health and environmental improvements. Salaried respondents in Kampala were willing to pay more than those on hourly wages. Tests of hypotheses suggested: (i) providing brief information to subjects just prior to the valuation exercise does not influence bid behavior, (ii) subjects are indifferent to the source of contamination: willingness to pay to avoid health outcomes from potentially contaminated water versus groundnuts are not significantly different, and (iii) the classical tendency to free-ride in public goods provision was observed in both urban and rural areas, and this phenomenon was more pronounced in the urban than the rural area. The second experimental procedure, choice experiments, involved 132 urban respondents making repeated choices from a set of scenarios described by attributes of water quality, an environmental good. Water quality was represented by profiles of water safety levels at varying costs. Analysis using a conditional (fixed effects) logit model showed that urban subjects highly discount unsafe drinking water, and were willing to pay less for safe agricultural water, a result not unexpected considering that the urban population is not directly involved in agricultural activities and thus may not value agricultural water quality as much as drinking water quality. It was also found that subjects’ utility increased with the cost of a water sample (inconsistent with a downward sloping demand curve), suggesting perhaps that they perceived higher cost water to be associated with higher quality water. Advertisements for bottled water in Uganda would have consumers believe that higher cost bottled water is higher quality.Experimental auctions, Choice experiments, Crop Production/Industries, Environmental Economics and Policy, Health Economics and Policy,

    A Limited Dependent Variable Analysis of Integrated Pest Management Adoption in Uganda

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    In Uganda overall crop loss due to pests exceeds that caused by drought, soil infertility, or poor planting material. Integrated Pest Management (IPM) technologies can reduce pest damage to crops by emphasizing non-chemical control methods thereby reducing potential negative effects of chemicals on the environment while preserving profitability. This study investigates the adoption of eight IPM practices including intercropping, crop rotation, two improved varieties, incorporating an 'exotic weed chaser', optimal planting dates, optimal planting density and fertilizer use. Variables include market forces, social factors, management factors, and technology delivery mechanisms. Results were consistent across the multivariate logit and ordered logit analyses. The single most important category of influential factors across all crops and technologies is economic/market forces, including labor availability, technology resource requirements, technology complexity, and the level of expected benefits. Social factors are generally less associated with IPM technology adoption than either market or institutional factors. Management factors are not important for adoption of the IPM technologies evaluated for the cowpea crop, while with groundnut IPM practices, no social or institutional factors are found to be important. High expected/potential benefits from the groundnut IPM technologies increase the probability of their adoption, as does the availability of off-farm income and farmers' membership in farm organizations. Generally high levels of adoption (>75%) were observed with crop rotation, and improved varieties. Other technologies registered low levels of adoption (<25%), the least popular being the application of fertilizer on sorghum fields.Research and Development/Tech Change/Emerging Technologies,

    Nutrition in Central Uganda - An Estimation of a Minimum Cost Healthy Diet

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    This study makes use of linear programming methodology to design a minimum cost diet for the Central Ugandan region. We used a set of constraints on recommended levels of daily nutrient intake, recommended proportions of groups of foods, as well as preferences and food availability in Central Uganda, to design a minimum cost healthy daily diet. Several models were considered, each forcing at least one of the following frequently consumed staple foods: matooke, cassava, and rice. We found that the minimum costs of the optimal diets were lowest in the planting season of March and highest in the harvesting season of December.Central Uganda, minimum cost diet, malnutrition, linear programming, Agricultural and Food Policy, Consumer/Household Economics, Food Consumption/Nutrition/Food Safety, Food Security and Poverty, Health Economics and Policy,

    LONG-RUN STRIGA CONTROL BY SUBSISTENCE FARMERS IN MALI

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    A dynamic programming model is developed to identify barriers to the adoption of long-run control programs for the parasitic weed Striga. The model is applied to Sirakorola in northwestern Mali. The ability of national and village-level institutions to overcome the barriers to adoption is explored.Community/Rural/Urban Development, Research and Development/Tech Change/Emerging Technologies,

    Differential Effects of Race and Poverty on Ambulatory Care Sensitive Conditions

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    This study is a continuation of an earlier study that examined hospitalization rates for ambulatory care sensitive (ACS) conditions, as a proxy for quality of care, and found evidence of a racial disparity among African American and White Medicare beneficiaries. The current study sought to determine whether neighborhood socioeconomic status (SES) explained this disparity. Differences in rates of ACS hospitalizations by race were assessed using Cochran-Mantel Haenszel tests and Poisson regression. Unadjusted rate ratios for ACS hospitalization for African Americans vs. Whites were found to be higher in low poverty areas (rate ratio (RR)=1.13; 95% CI (1.08, 1.17)) than in high poverty areas (RR=0.97; 95% CI (0.89, 1.05)). After controlling for various indicators of area SES in multivariate analyses race differences in ACS hospitalization rates persisted. Rural neighborhoods and those with higher percent of non-high school graduates were associated with greater risk of ACS hospitalizations

    Theory of the Three Dimensional Quantum Hall Effect in Graphite

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    We predict the existence of a three dimensional quantum Hall effect plateau in a graphite crystal subject to a magnetic field. The plateau has a Hall conductivity quantized at 4e21c0\frac{4e^2}{\hbar} \frac{1}{c_0} with c0c_0 the c-axis lattice constant. We analyze the three-dimensional Hofstadter problem of a realistic tight-binding Hamiltonian for graphite, find the gaps in the spectrum, and estimate the critical value of the magnetic field above which the Hall plateau appears. When the Fermi level is in the bulk Landau gap, Hall transport occurs through the appearance of chiral surface states. We estimate the magnetic field necessary for the appearance of the three dimensional quantum Hall Effect to be 15.415.4 T for electron carriers and 7.07.0 T for hole carriers.Comment: Several new references adde

    A variable-gain output feedback control design methodology

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    A digital control system design technique is developed in which the control system gain matrix varies with the plant operating point parameters. The design technique is obtained by formulating the problem as an optimal stochastic output feedback control law with variable gains. This approach provides a control theory framework within which the operating range of a control law can be significantly extended. Furthermore, the approach avoids the major shortcomings of the conventional gain-scheduling techniques. The optimal variable gain output feedback control problem is solved by embedding the Multi-Configuration Control (MCC) problem, previously solved at ICS. An algorithm to compute the optimal variable gain output feedback control gain matrices is developed. The algorithm is a modified version of the MCC algorithm improved so as to handle the large dimensionality which arises particularly in variable-gain control problems. The design methodology developed is applied to a reconfigurable aircraft control problem. A variable-gain output feedback control problem was formulated to design a flight control law for an AFTI F-16 aircraft which can automatically reconfigure its control strategy to accommodate failures in the horizontal tail control surface. Simulations of the closed-loop reconfigurable system show that the approach produces a control design which can accommodate such failures with relative ease. The technique can be applied to many other problems including sensor failure accommodation, mode switching control laws and super agility

    FARM ADVISORY SERVICES AND PESTICIDE TOXICITY ON COTTON AND PEANUTS IN THE ALBEMARLE-PAMLICO WATERSHED

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    According to a Virginia-North Carolina watershed survey, farmers view advisory services as having the effect of decreasing pesticide use. However, analysis of pesticide use shows that hired staff, scouting personnel, and extension agents are associated with higher pesticide toxicity applied to cotton while chemical dealers and scouting personnel are associated with higher toxicity applied to peanuts.Crop Production/Industries, Environmental Economics and Policy,
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