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

Temperature oscillations of magnetization observed in nanofluid ferromagnetic graphite

We report on unusual magnetic properties observed in the nanofluid room-temperature ferromagnetic graphite (with an average particle size of l=10nm). More precisely, the measured magnetization exhibits a low-temperature anomaly (attributed to manifestation of finite size effects below the quantum temperature) as well as pronounced temperature oscillations above T=50K (attributed to manifestation of the hard-sphere type pair correlations between ferromagnetic particles in the nanofluid)

The Highly Miniaturised Radiation Monitor

We present the design and preliminary calibration results of a novel highly miniaturised particle radiation monitor (HMRM) for spacecraft use. The HMRM device comprises a telescopic configuration of active pixel sensors enclosed in a titanium shield, with an estimated total mass of 52 g and volume of 15 cm$^3$. The monitor is intended to provide real-time dosimetry and identification of energetic charged particles in fluxes of up to 10$^8$ cm$^{-2}$ s$^{-1}$ (omnidirectional). Achieving this capability with such a small instrument could open new prospects for radiation detection in space.Comment: 17 pages, 15 figure

Watersheds are Schramm-Loewner Evolution curves

We show that in the continuum limit watersheds dividing drainage basins are Schramm-Loewner Evolution (SLE) curves, being described by one single parameter $\kappa$. Several numerical evaluations are applied to ascertain this. All calculations are consistent with SLE$_\kappa$, with $\kappa=1.734\pm0.005$, being the only known physical example of an SLE with $\kappa<2$. This lies outside the well-known duality conjecture, bringing up new questions regarding the existence and reversibility of dual models. Furthermore it constitutes a strong indication for conformal invariance in random landscapes and suggests that watersheds likely correspond to a logarithmic Conformal Field Theory (CFT) with central charge $c\approx-7/2$.Comment: 5 pages and 4 figure

Auditoria à prática profilática e incidência de náuseas e vómitos pós-operatórios (NVPO)

Introdução: As NVPO são uma das principais queixas dos doentes do pós-operatório. Este trabalho teve como objetivo registar a prática farmacológica para profilaxia de NVPO em cirurgia programada e avaliar a sua eficácia. Metodologia: Incluídos todos os doentes submetidos a cirurgia programada das especialidades de Cirurgia Geral, Urologia e Cirurgia Vascular entre 3 e 21 de Dezembro de 2012. Excluídos se alta<24horas(h), pós-operatório no Serviço Cuidados Intensivos/ Intermédios ou impossível acesso aos registos. Tendo como modelos o Score Apfel Simplificado e as recomendações para cirurgia de ambulatório(1) (Tabela 1), a profilaxia instituída foi dividida em adequada, a mais ou a menos; avaliação da ocorrência de NVPO na Unidade Cuidados Pós-Anestésicos e às 24h (registos anestésicos e entrevista). Resultados apresentados em percentagem. Aplicação teste qui quadrado com p<0,05 para significância. Resultados: Avaliados 255 doentes (excluídos 68, incluídos 187). Com 0-1 fator risco (FR) 34%, 2 FR 45%, 3-4 FR 21%. A profilaxia foi adequada em 53% dos doentes, a mais em 16% e a menos em 31%. Incidência total de NVPO - 22% (24% no grupo de doentes que fez profilaxia adequada e 20% no grupo de profilaxia inadequada (p=0.35012)). Neste último grupo 13% realizaram profilaxia a mais e 24% a menos. Resultados da incidência de NVPO por fator de risco na tabela 2. A incidência de NVPO por FR nos doentes com profilaxia adequada foi menor ou igual em todos os grupos em relação ao previsto no Score Apfel simplicado(1,2). No grupo que fez profilaxia inadequada, esta foi a menos principalmente no grupo de 2 FR, com 71% de NVPO; e foi a mais essencialmente no grupo com 1 FR (4 doentes, todos com NVPO). Incidência menor com anestesia locoregional (ALR) vs anestesia geral (AG) (13% vs 27%) (p<0.001). Discussão e Conclusões: A profilaxia foi adequada, segundo as recomendações para cirurgia de ambulatório, em cerca de metade dos doentes. Apesar da profilaxia adequada, nos grupos de FR 1 e 2 não houve redução da incidência de NVPO comparando com a prevista pelo score de Apfel, alertando para a importância de outros fatores de risco não previstos neste score e que estas recomendações poderão ser insuficientes para a profilaxia de NVPO em cirurgia em regime de internamento. A incidência de NVPO foi menor com ALR vs AG, corroborando a ALR como melhor opção em doentes de risco de NVPO (1,2). Estes resultados salientam a importância da adoção de estratégias para redução do risco basal

Theory and modeling of the magnetic field measurement in LISA PathFinder

The magnetic diagnostics subsystem of the LISA Technology Package (LTP) on board the LISA PathFinder (LPF) spacecraft includes a set of four tri-axial fluxgate magnetometers, intended to measure with high precision the magnetic field at their respective positions. However, their readouts do not provide a direct measurement of the magnetic field at the positions of the test masses, and hence an interpolation method must be designed and implemented to obtain the values of the magnetic field at these positions. However, such interpolation process faces serious difficulties. Indeed, the size of the interpolation region is excessive for a linear interpolation to be reliable while, on the other hand, the number of magnetometer channels does not provide sufficient data to go beyond the linear approximation. We describe an alternative method to address this issue, by means of neural network algorithms. The key point in this approach is the ability of neural networks to learn from suitable training data representing the behavior of the magnetic field. Despite the relatively large distance between the test masses and the magnetometers, and the insufficient number of data channels, we find that our artificial neural network algorithm is able to reduce the estimation errors of the field and gradient down to levels below 10%, a quite satisfactory result. Learning efficiency can be best improved by making use of data obtained in on-ground measurements prior to mission launch in all relevant satellite locations and in real operation conditions. Reliable information on that appears to be essential for a meaningful assessment of magnetic noise in the LTP.Comment: 10 pages, 8 figures, 2 tables, submitted to Physical Review