8,477 research outputs found
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
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