Micro-bias and macro-performance

We use agent-based modeling to investigate the effect of conservatism and partisanship on the efficiency with which large populations solve the density classification task--a paradigmatic problem for information aggregation and consensus building. We find that conservative agents enhance the populations' ability to efficiently solve the density classification task despite large levels of noise in the system. In contrast, we find that the presence of even a small fraction of partisans holding the minority position will result in deadlock or a consensus on an incorrect answer. Our results provide a possible explanation for the emergence of conservatism and suggest that even low levels of partisanship can lead to significant social costs.Comment: 11 pages, 5 figure

Sampling system for wheat (Triticum aestivum L) area estimation using digital LANDSAT MSS data and aerial photographs

A procedure to estimate wheat (Triticum aestivum L) area using sampling technique based on aerial photographs and digital LANDSAT MSS data is developed. Aerial photographs covering 720 square km are visually analyzed. To estimate wheat area, a regression approach is applied using different sample sizes and various sampling units. As the size of sampling unit decreased, the percentage of sampled area required to obtain similar estimation performance also decreased. The lowest percentage of the area sampled for wheat estimation with relatively high precision and accuracy through regression estimation is 13.90% using 10 square km as the sampling unit. Wheat area estimation using only aerial photographs is less precise and accurate than those obtained by regression estimation

Irrigated rice area estimation using remote sensing techniques: Project's proposal and preliminary results

The development of a methodology for annual estimates of irrigated rice crop in the State of Rio Grande do Sul, Brazil, using remote sensing techniques is proposed. The project involves interpretation, digital analysis, and sampling techniques of LANDSAT imagery. Results are discussed from a preliminary phase for identifying and evaluating irrigated rice crop areas in four counties of the State, for the crop year 1982/1983. This first phase involved just visual interpretation techniques of MSS/LANDSAT images

Transport on exploding percolation clusters

We propose a simple generalization of the explosive percolation process [Achlioptas et al., Science 323, 1453 (2009)], and investigate its structural and transport properties. In this model, at each step, a set of q unoccupied bonds is randomly chosen. Each of these bonds is then associated with a weight given by the product of the cluster sizes that they would potentially connect, and only that bond among the q-set which has the smallest weight becomes occupied. Our results indicate that, at criticality, all finite-size scaling exponents for the spanning cluster, the conducting backbone, the cutting bonds, and the global conductance of the system, change continuously and significantly with q. Surprisingly, we also observe that systems with intermediate values of q display the worst conductive performance. This is explained by the strong inhibition of loops in the spanning cluster, resulting in a substantially smaller associated conducting backbone.Comment: 4 pages, 4 figure

Universal reduction of pressure between charged surfaces by long-wavelength surface charge modulation

We predict theoretically that long-wavelength surface charge modulations universally reduce the pressure between the charged surfaces with counterions compared with the case of uniformly charged surfaces with the same average surface charge density. The physical origin of this effect is the fact that surface charge modulations always lead to enhanced counterion localization near the surfaces, and hence, fewer charges at the midplane. We confirm the last prediction with Monte Carlo simulations.Comment: 8 pages 1 figure, Europhys. Lett., in pres

A sampling system for estimating the cultivation of wheat (Triticum aestivum L) from LANDSAT data

Using digitally processed MSS/LANDSAT data as auxiliary variable, a methodology to estimate wheat (Triticum aestivum L) area by means of sampling techniques was developed. To perform this research, aerial photographs covering 720 sq km in Cruz Alta test site at the NW of Rio Grande do Sul State, were visually analyzed. LANDSAT digital data were analyzed using non-supervised and supervised classification algorithms; as post-processing the classification was submitted to spatial filtering. To estimate wheat area, the regression estimation method was applied and different sample sizes and various sampling units (10, 20, 30, 40 and 60 sq km) were tested. Based on the four decision criteria established for this research, it was concluded that: (1) as the size of sampling units decreased the percentage of sampled area required to obtain similar estimation performance also decreased; (2) the lowest percentage of the area sampled for wheat estimation with relatively high precision and accuracy through regression estimation was 90% using 10 sq km s the sampling unit; and (3) wheat area estimation by direct expansion (using only aerial photographs) was less precise and accurate when compared to those obtained by means of regression estimation

Avaliação das sementes do nim (Azadirachta indica) no controle de nematódeos gastrintestinais de caprinos criados em sistema de base agroecológica: resultados preliminares.

O objetivo desse trabalho foi avaliar a eficácia das sementes do nim (Azadiracht indica A. Juss) no controle das verminoses gastrintestinais de caprinos criados no sistema de produção do Cabrito Ecológico da Embrapa Semi-Árido. O trabalho foi realizado durante a época chuvosa (fevereiro a março), utilizando 18 caprinos ser padrão racial definido, divididos em três grupos homogêneos de acordo com os seguintes tratamentos: T1 controle (água); T2 (1,0 glkg) e T3 (3,0 glkg). Foram realizadas três aplicações com intervalo de 13 dias. Para avaliar a eficácia dos tratamentos, foi realizada a contagem do número de ovos de nematódeos pc gramas de fezes (OPG) antes e sete dias após as dosificações. Foi observado aumento do OPG em quase todos os tratamentos. Nas condições desse trabalho, a sementes do nim não foram eficazes no controle de nematódeos gastrintestinais de caprinos

Avaliação de plantas medicinais no controle de nematódeos gastrintestinais de caprinos criados em sistema de base agroecológica.

Este trabalho objetivou avaliar a eficácia de plantas medicinais no controle de nematódeos gastrintestinais. Foram utilizados 36 caprinos distribuídos em seis grupos de seis animais, nos seguintes tratamentos: T1 água (50 mL/animal); T2 closantel (10 mg/kg); T3 Curcubita sp. (3 g/kg); T4 Operculina sp. (8 g/kg); T5 Azadirachta indica (1 g/kg) e T6 Azadirachta indica (3 g/kg). As dosagens foram administradas após 12 horas de jejum, sob a forma de suco, por via oral. A eficácia dos tratamentos foi obtida pela contagem do OPG antes e sete dias após os tratamentos. A média do número de OPG antes dos tratamentos em todas as avaliações foi de 2.500 ovos. Apesar da discreta redução do OPG causada pelo T3 (41,0%) e T4 (34,9%) após a primeira administração, o OPG ainda permaneceu bastante elevado. Nos tratamentos T1, T5 e T6 foi observado aumento do OPG. A eficiência do closantel (T2) foi de 75,9%. Portanto, as dosagens utilizadas não apresentaram eficácia na redução do OPG