Temporal Analysis of Activity Patterns of Editors in Collaborative Mapping Project of OpenStreetMap

In the recent years Wikis have become an attractive platform for social studies of the human behaviour. Containing millions records of edits across the globe, collaborative systems such as Wikipedia have allowed researchers to gain a better understanding of editors participation and their activity patterns. However, contributions made to Geo-wikis_wiki-based collaborative mapping projects_ differ from systems such as Wikipedia in a fundamental way due to spatial dimension of the content that limits the contributors to a set of those who posses local knowledge about a specific area and therefore cross-platform studies and comparisons are required to build a comprehensive image of online open collaboration phenomena. In this work, we study the temporal behavioural pattern of OpenStreetMap editors, a successful example of geo-wiki, for two European capital cities. We categorise different type of temporal patterns and report on the historical trend within a period of 7 years of the project age. We also draw a comparison with the previously observed editing activity patterns of Wikipedia.Comment: Submitte

Uso do Glyphosate no controle da ferrugem da soja e sua interação com o ácido chiquímico.

RESUMO: Estudos preliminares tem constatado o efeito do glyphosate no desenvolvimento do fungo Phakopsora pachyrhizi entretanto, mais pesquisas são necessárias para se confirmar esse efeito, sua interação com o fungo bem como a fisiologia da infecção. O objetivo do trabalho foi verificar se a interação de glyphosate e P. pachyrhizi poderia induzir a formação de ácido chiquímico na soja RR. Plantas inoculadas e não inoculadas foram tratadas com glyphosate aos 3, 6, 9 e 12 dias após inoculação determinando-se o ácido chiquímico 3 dias após aplicação do herbicida por cromatografia líquida. O ensaio foi conduzido no delineamento inteiramente casualizado com 3 repetições com as médias comparadas a 5% pelo teste de Tukey. Apesar de ter sido observado um aumento nas concentrações de ácido chiquímico em todos os tratamentos aplicados 12 dias após a inoculação (ou não) do fungo P. pachyrizi, esse aumento não é conseqüência do efeito do glyphosate sobre as plantas nem da ação elicitora do fungo ou da interação entre ambos

Magnetic phases evolution in the LaMn1-xFexO3+y system

We have investigated the crystal structure and magnetic properties for polycrystalline samples of LaMn1-xFexO3+y, in the whole range x=0.0 to x=1.0, prepared by solid state reaction in air. All samples show the ORT-2 orthorhombic structure that suppresses the Jahn-Teller distortion, thus favoring a ferromagnetic (FM) superexchange (SE) interaction between Mn^{3+}-O-Mn^{3+}. For x=0.0 the oxygen excess (y ~ 0.09) produces vacancies in the La and Mn sites and generates a fraction around 18% of Mn^{4+} ions and 82% of the usual Mn^{3+} ions, with possible double exchange interaction between them. The Fe doping in this system is known to produce only stable Fe^{3+} ions. We find an evolution from a fairly strong FM phase with a Curie temperature T_{C} ~ 160 K, for x=0.0, to an antiferromagnetic (AFM) phase with T_{N} = 790 K, for x=1.0, accompanied by clear signatures of a cluster-glass behavior. For intermediate Fe contents a mixed-phase state occurs, with a gradual decrease (increase) of the FM (AFM) phase, accompanied by a systematic transition broadening for 0.2 < x < 0.7. A model based on the expected exchange interaction among the various magnetic-ion types, accounts very well for the saturation-magnetization dependence on Fe doping.Comment: 27 pages, 9 figure

Monitoramento do ácido chiquímico em plantas de citrus sob diferentes sistemas de manejo de plantas daninhas.

Glifosato; Planta daninha

Recomendações para o controle de plantas daninhas na cultura da soja.

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Analytical solution of a generalized Penna model

In 1995 T.J.Penna introduced a simple model of biological aging. A modified Penna model has been demonstrated to exhibit behaviour of real-life systems including catastrophic senescence in salmon and a mortality plateau at advanced ages. We present a general steady-state, analytic solution to the Penna model, able to deal with arbitrary birth and survivability functions. This solution is employed to solve standard variant Penna models studied by simulation. Different Verhulst factors regulating both the birth rate and external death rate are considered.Comment: 6 figure

Common Representation of Information Flows for Dynamic Coalitions

We propose a formal foundation for reasoning about access control policies within a Dynamic Coalition, defining an abstraction over existing access control models and providing mechanisms for translation of those models into information-flow domain. The abstracted information-flow domain model, called a Common Representation, can then be used for defining a way to control the evolution of Dynamic Coalitions with respect to information flow