2,445 research outputs found

    FARM-LEVEL RESPONSE TO AGRICULTURAL EFFLUENT CONTROL STRATEGIES: THE CASE OF THE WILLAMETTE VALLEY

    Get PDF
    This article examines economic incentives and other mechanisms to offset non-point source pollution from agriculture. A biophysical simulator to estimate technical relationships is linked to linear programming models for representative farms in the Willamette Valley of Oregon. The models are then optimized for profit maximization under alternative non-point pollution control policies. The results indicate that site-specific resource conditions and production possibilities greatly influence policy effectiveness and the cost of achieving pollution abatement. Nevertheless, some abatement is possible on all farms for relatively little cost.Environmental Economics and Policy,

    Landing and catalytic characterization of individual nanoparticles on electrode surfaces

    Get PDF
    We demonstrate a novel and versatile pipet-based approach to study the landing of individual nanoparticles (NPs) on various electrode materials without any need for encapsulation or fabrication of complex substrate electrode structures, providing great flexibility with respect to electrode materials. Because of the small electrode area defined by the pipet dimensions, the background current is low, allowing for the detection of minute current signals with good time resolution. This approach was used to characterize the potential-dependent activity of Au NPs and to measure the catalytic activity of a single NP on a TEM grid, combining electrochemical and physical characterization at the single NP level for the first time. Such measurements open up the possibility of studying the relation between the size, structure and activity of catalyst particles unambiguously

    Economic and agronomic evaluation of a common bean experiment Uberaba, Minas Gerais

    Get PDF
    Com a finalidade de estudar as possibilidades de aproveitamento dos cerrados da região para o cultivo do feijão, foi analisada a influência, na produção, de cinco níveis de N e P2O5 utilizando-se um fatorial 5X5 completo. A partir dêsse esquema experimental comparou-se a eficiência de quatro outros delineamentos. Um esquema central composto mais os extremos teve eficiência equivalente ao do fatorial 5x5 completo e foi utilizado na interpretação econômica. Determinou-se a superfície da resposta dos insumos e produção e as combinações de nutrientes que resultaram nos lucros máximos. Finalmente, na última parte do trabalho foram feitas considerações sobre procedimentos alternativos do uso dos insumos face a variações dos preços do produto dos insumos.An economic and agronomic evaluation of the possibilities to produce common beans in poor "cerrado" in central Brazil was made by the use of five levels of N and P2O5. The experimental portion of the paper deals with a comparison of several types of "treatment designs", some of which are specific for estimating response surfaces. The results from one of the latter designs were used to demonstrate the general principles of agronomic economics analysis. .The results have shown that central composite plus extremes design provided information equivalent to the standard 5x5 factorial with the use of fewer resources and, therefore, was used in the economic phase of the paper. The other designs studied were small and large 3x3 factorials and central composite. To evaluate the use of N and P2O5 in the production of beans, estimates were made of the economically relevant portions of the plant nutrient input-output surface. A graphic illustration of three curves of a family of isoquants for the production of beans was made. Points of equal marginal rate or substitution of successively higher isoquants were marked by the line called isocline. Output maximization and cost minimization were determined as well as profit maximization. The return per hectare after deducting costs of applied N and P2O5 vary with the price of beans per kg. In general, optimal quantities of inputs and residual return fall as factor prices increase. However, a greater percentage of decrease occurs in residual return per hectare and in yield per hectare, as the price of P2O5 increases (with the price of N held constant). It was shown that the proper anticipation of the price of beans is important to the farmer to obtain maximum returns. He will use the most profitable combination of inputs

    Análise econômica de experimentos com forragens e gado realizados no Estado de São Paulo

    Get PDF
    The purpose of this paper is to bring together in one place much of the pasture and livestock research experience of IRI in the State of São Paulo and to analyze it from an economic standpoint. To do so, many assumptions had to be made. Attempts were made to keep the assumptions realistic for the area in which the experiments were conducted. They undoubtedly are not, however, generally applicable to Brazil or even to many parts of the State of São Paulo. Rather, it is hoped that the procedure is sufficiently clear that decision makers may follow similar procedures, making their own assumptions, and thus answer questions covered in this report under conditions specific to their localities. From the data and assumptions made, it appears that: a) Common Pangola (Digitaria decumbens) has the highest annual rate of return of the six grasses tested. It affectively repelled the invasion of Bahia grass and maintained a relatively constant yield over time. Colonial Guinea was its nearest competitor, but it failed to maintain production over time. b) As a general statement, the use of 100 kilos of available nitrogen per hectare on Colonial Guinea grass appears to be profitable. The use of 200 kilos appears to be approximately the point where the marginal cost equals the marginal return and thus is the point of no profit. c) Both the use of stilbestrol and molasses appear to be profitable. d) Supplemental feeding ground corn meal or a low protein meal may be profitable on low quality forage if the weight advantage can be maintained during later periods. At present it is not known if it can. Additional research needs to be conducted to test this point.O propósito dêste manuscrito é reunir em um só trabalho a experiência do Instituto de Pesquisas IRI em pastagens e pecuária, no Estado de São Paulo, e analisá-lo sob o ponto de vista econômico. Para êste fim, tiveram que ser fitas muitas pressuposições. Tais pressuposições são baseadas nas condições da área onde os experimentos foram realizados, podendo não ser aplicáveis, de modo geral, para todo o Brasil ou mesmo para outras áreas do Estado de São Paulo. Espera-se que os métodos usados sejam suficientemente claros para que os interessados possam utilizá-lo fazendo suas próprias pressuposições, e assim possam responder às questões dêste trabalho, sob condições específicas de suas localidades. Como resultado dos dados e pressuposições feitas, parece que: a) O capim Pangola comum (Digitaria decumbens) é, das seis gramíneas examinadas, a que dá maior lucro anual. Isto acontece por controlar eficientemente a invasão da grama Batatais e por manter uma produção relativamente constante no decorrer do ano. O competidor mais aproximado foi o Colonião, porém não conseguiu manter produção constante durante as diferentes épocas do ano. b) Pode-se dizer, de modo geral, que a utilização de 100 kg de nitrogênio disponível por hectare de pastagens de capim Colonião parece ser lucrativa. O uso de 200 kg parece ser aproximadamente o ponto onde o custo marginal iguala a renda marginal e assim é o ponto onde o lucro desaparece. c) A utilização, tanto do estilbestrol como do melaço, parece ser lucrativa. d) O uso de farelo de milho ou de uma ração com baixo teor de proteína pode ser lucrativo em pastagens de baixa qualidade, se o aumento do pêso puder ser mantido posteriormente. No momento, não há certeza quanto a essa possibilidade. Há necessidade de maiores estudos para verificação dêsse ponto

    Análise econômica de experimentos com forragens e gado realizados no Estado de São Paulo

    Get PDF
    The purpose of this paper is to bring together in one place much of the pasture and livestock research experience of IRI in the State of São Paulo and to analyze it from an economic standpoint. To do so, many assumptions had to be made. Attempts were made to keep the assumptions realistic for the area in which the experiments were conducted. They undoubtedly are not, however, generally applicable to Brazil or even to many parts of the State of São Paulo. Rather, it is hoped that the procedure is sufficiently clear that decision makers may follow similar procedures, making their own assumptions, and thus answer questions covered in this report under conditions specific to their localities. From the data and assumptions made, it appears that: a) Common Pangola (Digitaria decumbens) has the highest annual rate of return of the six grasses tested. It affectively repelled the invasion of Bahia grass and maintained a relatively constant yield over time. Colonial Guinea was its nearest competitor, but it failed to maintain production over time. b) As a general statement, the use of 100 kilos of available nitrogen per hectare on Colonial Guinea grass appears to be profitable. The use of 200 kilos appears to be approximately the point where the marginal cost equals the marginal return and thus is the point of no profit. c) Both the use of stilbestrol and molasses appear to be profitable. d) Supplemental feeding ground corn meal or a low protein meal may be profitable on low quality forage if the weight advantage can be maintained during later periods. At present it is not known if it can. Additional research needs to be conducted to test this point.O propósito dêste manuscrito é reunir em um só trabalho a experiência do Instituto de Pesquisas IRI em pastagens e pecuária, no Estado de São Paulo, e analisá-lo sob o ponto de vista econômico. Para êste fim, tiveram que ser fitas muitas pressuposições. Tais pressuposições são baseadas nas condições da área onde os experimentos foram realizados, podendo não ser aplicáveis, de modo geral, para todo o Brasil ou mesmo para outras áreas do Estado de São Paulo. Espera-se que os métodos usados sejam suficientemente claros para que os interessados possam utilizá-lo fazendo suas próprias pressuposições, e assim possam responder às questões dêste trabalho, sob condições específicas de suas localidades. Como resultado dos dados e pressuposições feitas, parece que: a) O capim Pangola comum (Digitaria decumbens) é, das seis gramíneas examinadas, a que dá maior lucro anual. Isto acontece por controlar eficientemente a invasão da grama Batatais e por manter uma produção relativamente constante no decorrer do ano. O competidor mais aproximado foi o Colonião, porém não conseguiu manter produção constante durante as diferentes épocas do ano. b) Pode-se dizer, de modo geral, que a utilização de 100 kg de nitrogênio disponível por hectare de pastagens de capim Colonião parece ser lucrativa. O uso de 200 kg parece ser aproximadamente o ponto onde o custo marginal iguala a renda marginal e assim é o ponto onde o lucro desaparece. c) A utilização, tanto do estilbestrol como do melaço, parece ser lucrativa. d) O uso de farelo de milho ou de uma ração com baixo teor de proteína pode ser lucrativo em pastagens de baixa qualidade, se o aumento do pêso puder ser mantido posteriormente. No momento, não há certeza quanto a essa possibilidade. Há necessidade de maiores estudos para verificação dêsse ponto

    Ghost Images in Helioseismic Holography? Toy Models in a Uniform Medium

    Get PDF
    Helioseismic holography is a powerful technique used to probe the solar interior based on estimations of the 3D wavefield. Porter--Bojarski holography, which is a well-established method used in acoustics to recover sources and scatterers in 3D, is also an estimation of the wavefield, and hence it has the potential to be applied to helioseismology. Here we present a proof of concept study, where we compare helioseismic holography and Porter--Bojarski holography under the assumption that the waves propagate in a homogeneous medium. We consider the problem of locating a point source of wave excitation inside a sphere. Under these assumptions, we find that the two imaging methods have the same capability of locating the source, with the exception that helioseismic holography suffers from "ghost images" (i.e., artificial peaks away from the source location). We conclude that Porter--Bojarski holography may improve the current method used in helioseismology.Comment: 17 pages, 8 figure

    Modeling bursts and heavy tails in human dynamics

    Full text link
    Current models of human dynamics, used from risk assessment to communications, assume that human actions are randomly distributed in time and thus well approximated by Poisson processes. We provide direct evidence that for five human activity patterns the timing of individual human actions follow non-Poisson statistics, characterized by bursts of rapidly occurring events separated by long periods of inactivity. We show that the bursty nature of human behavior is a consequence of a decision based queuing process: when individuals execute tasks based on some perceived priority, the timing of the tasks will be heavy tailed, most tasks being rapidly executed, while a few experiencing very long waiting times. We discuss two queueing models that capture human activity. The first model assumes that there are no limitations on the number of tasks an individual can hadle at any time, predicting that the waiting time of the individual tasks follow a heavy tailed distribution with exponent alpha=3/2. The second model imposes limitations on the queue length, resulting in alpha=1. We provide empirical evidence supporting the relevance of these two models to human activity patterns. Finally, we discuss possible extension of the proposed queueing models and outline some future challenges in exploring the statistical mechanisms of human dynamics.Comment: RevTex, 19 pages, 8 figure
    corecore