Neutron Charge Radius: Relativistic Effects and the Foldy Term

The neutron charge radius is studied within a light-front model with different spin coupling schemes and wave functions. The cancellation of the contributions from the Foldy term and Dirac form factor to the neutron charge form factor is verified for large nucleon sizes and it is independent of the detailed form of quark spin coupling and wave function. For the physical nucleon our results for the contribution of the Dirac form factor to the neutron radius are insensitive to the form of the wave function while they strongly depend on the quark spin coupling scheme.Comment: 12 pages, 5 figures, Latex, Int. J. Mod. Phys.

Collaboration networks from a large CV database: dynamics, topology and bonus impact

Understanding the dynamics of research production and collaboration may reveal better strategies for scientific careers, academic institutions and funding agencies. Here we propose the use of a large and multidisciplinar database of scientific curricula in Brazil, namely, the Lattes Platform, to study patterns of scientific production and collaboration. In this database, detailed information about publications and researchers are made available by themselves so that coauthorship is unambiguous and individuals can be evaluated by scientific productivity, geographical location and field of expertise. Our results show that the collaboration network is growing exponentially for the last three decades, with a distribution of number of collaborators per researcher that approaches a power-law as the network gets older. Moreover, both the distributions of number of collaborators and production per researcher obey power-law behaviors, regardless of the geographical location or field, suggesting that the same universal mechanism might be responsible for network growth and productivity.We also show that the collaboration network under investigation displays a typical assortative mixing behavior, where teeming researchers (i.e., with high degree) tend to collaborate with others alike. Finally, our analysis reveals that the distinctive collaboration profile of researchers awarded with governmental scholarships suggests a strong bonus impact on their productivity.Comment: 8 pages, 8 figure

First-order transitions and triple point on a random p-spin interaction model

The effects of competing quadrupolar- and spin-glass orderings are investigated on a spin-1 Ising model with infinite-range random $p$-spin interactions. The model is studied through the replica approach and a phase diagram is obtained in the limit $p\to\infty$. The phase diagram, obtained within replica-symmetry breaking, exhibits a very unusual feature in magnetic models: three first-order transition lines meeting at a commom triple point, where all phases of the model coexist.Comment: 9 pages, 2 ps figures include

Uso da trifluralina para controle de intrusão de radicelas de cana-de-açúcar em gotejadores enterrados.

Um dos fatores que limitam a aplicação e utilização da irrigação subsuperficial por gotejamento são os problemas devido à intrusão dos emissores por radicelas e/ou partículas minerais do solo. O dimensionamento e o manejo do sistema de irrigação adequado pode evitar que isso ocorra, proporcionando que a irrigação por gotejamento subsuperficial seja um método de irrigação viável. A injeção de Trifluralina no sistema de irrigação é um dos manejos adotados para prevenir a ocorrência de obstrução nos emissores pelas radicelas. O objetivo desta pesquisa foi avaliar o efeito da Trifluralina no controle de intrusão de radicelas de cana-de-açúcar em um tubo gotejador enterrado. Notou-se que com o desenvolvimento da cana-de-açúcar do oitavo ao décimo segundo mês, os emissores que não estiveram sujeitos à aplicação do herbicida apresentaram redução na vazão, bem como, no coeficiente de uniformidade estatística

Diagnóstico agroambiental do Município de Jatobá, Estado de Pernambuco.

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Gas exchenge in upland cotton cultivars under water deficit strategies.

Upland cotton crop in Brazilian semiarid zones has a favorable factor, the duration of the mean solar day. On the other hand, cotton is frequently subjected to soil water deficit. Several physiological indexes are related to the use of water by plants. Among them, photosynthesis and stomatal conductance stand out, as osmotic adjustment, such as stomatal closure, allows plants to escape dehydration and loss of turgor through the maintenance of the water content in the cells. Therefore, the efficiency of water use for irrigated production systems need to be optimized, especially in the cotton crop, as it is a species of great economic and social importance. Aiming to evaluate the gas exchange of upland cotton cultivars cultivated in the Brazilian semiarid, subject to water deficit periods on the phenological stages, an experiment was carried out at the Campina Grande Federal University, Pombal county campus, Paraíba, between June and December 2015