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

Manifestation of finite temperature size effects in nanogranular magnetic graphite

In addition to the double phase transition (with the Curie temperatures T_C=300K and T_{Ct}=144K), a low-temperature anomaly in the dependence of the magnetization is observed in the bulk magnetic graphite (with an average granular size of L=10nm), which is attributed to manifestation of the size effects below the quantum temperature. The best fits of the high-temperature data (using the mean-field Curie-Weiss and Bloch expressions) produced reasonable estimates for the model parameters, such as defects mediated effective spin exchange energy J=12meV (which defines the intragranular Curie temperature T_C) and proximity mediated interactions between neighboring grains (through potential barriers created by thin layers of non-magnetic graphite) with energy J_t=exp(-d/s)J=5.8meV (which defines the intergranular Curie temperature T_{Ct}) with d=1.5nm and s=2nm being the intergranular distance and characteristic length, respectively

Caracterização de acessos de mandioca silvestre para uso no pré-melhoramento de Manihot esculenta Crantz.

As mandiocas silvestres exercem um papel inquestionável por serem considerados reservatórios de alelos competitivos e de interesse para uso dos melhoristas. O presente trabalho teve por objetivo dar início à caracterização molecular de 33 acessos de espécies silvestres de Manihot com o intuito de avaliar a variabilidade genética para ser explorada dentro do programa de melhoramento genético de mandioca da Embrapa Mandioca e Fruticultura. O DNA foi extraído dos acessos e será utilizado na etapa seguinte de caracterização molecular. Os dados obtidos serão analisados e submetidos à análise multivariada de agrupamento a partir da matriz do índice de dissimilaridade de Jaccard. A susceptibilidade ou incapacidade genética da mandioca só pode ser evitada com a variabilidade, na qual a mesma depende dos recursos genéticos. As espécies silvestres de Manihot são pouco estudadas e este trabalho servirá de base para o delineamento das estratégias de cruzamentos pelos melhoristas com o intuito de transferir genes de interesse para as espécies cultivadas