Irreversibility line and low-field grain-boundary pinning in electron-doped superconducting thin films

AC magnetic susceptibilities of electron-doped Pr_{1.85}Ce_{0.15}CuO_4 (PCCO) and Sm_{1.85}Ce_{0.15}CuO_4 (SCCO) granular thin films have been measured as a function of temperature and magnetic-field strength. Depending on the level of homogeneity of our films, two different types of the irreversibility line (IL) defined as the intergrain-loss peak temperature in the imaginary part of susceptibility have been found. The obtained results are described via the critical-state model taking into account the low-field grain-boundary pinning. The extracted pinning-force densities in more granular SCCO films turn out to be four times larger than their counterparts in less granular PCCO films

Possible manifestation of spin fluctuations in the temperature behavior of resistivity in Sm_{1.85}Ce_{0.15}CuO_4 thin films

A pronounced step-like (kink) behavior in the temperature dependence of resistivity $\rho (T)$ is observed in the optimally-doped $Sm_{1.85}Ce_{0.15}CuO_4$ thin films around $T_{sf}=87K$ and attributed to manifestation of strong spin fluctuations induced by $Sm^{3+}$ moments with the energy $\hbar \omega_{sf}=k_BT_{sf}\simeq 7meV$. In addition to fluctuation induced contribution $\rho_{sf}(T)$ due to thermal broadening effects (of the width $\omega_{sf}$), the experimental data are found to be well fitted accounting for residual (zero-temperature) $\rho_{res}$, electron-phonon $\rho _{e-ph}(T)=AT$ and electron-electron $\rho_{e-e}(T)=BT^2$ contributions. The best fits produced $\omega_p=2.1meV$, $\tau_0^{-1}=9.5\times 10^{-14}s^{-1}$, $\lambda =1.2$, and $E_F=0.2eV$ for estimates of the plasmon frequency, the impurity scattering rate, electron-phonon coupling constant, and the Fermi energy, respectively.Comment: 6 pages (REVTEX4), 2 EPS figures; accepted for publication in JETP Letter

Portuguese sprayers inspections: issues to overcome

The EN 13790 and agricultural products certification standards stimulated the sprayers inspections in a yearly basis in Portugal. Since 2006 Centro Operativo e Tecnológico Hortofrutícola Nacional (COTHN) inspected almost 3000 sprayers throughout the all country, including field crops sprayers, air assisted sprayers for bush and tree crops and a few hand held sprayers for greenhouse crops. In 2009 and 2010, Ambi3Q and A.CANO began with sprayers inspections in the north and south of Portugal, respectively. The implementation of the article 8 of the European Directive CE 128/09 in all member states is an important step to minimize environmental impacts, protect human health and improve plant protection efficacy. However it is not an easy task due to the characteristics of agriculture and sprayers in use of each country.The actual legislation concerning the construction and inspection of sprayers was published in the last 3 years. According to the article 8 of the European Directive, the Official Service Direcção-Geral de Agricultura e Desenvolvimento Rural (DGADR) of the Agriculture Ministry, developed the Portuguese law Decreto-Lei n.º 86/2010 de 15 de Julho, in 2010, to impose that mounted sprayers, trailed sprayers and self-propelled sprayers must be inspected and approved before 26 November, 2016.The sprayers inspections carried out in Portugal should be an important tool to assess the sprayers in use and decide the best action plan to implement the article 8. Despite the sprayers inspections had been done mostly as a consequence of the European and National market rules, and so, the data collected are a rough sample of the real Portuguese situation, it is possible to observe that only one-third, of the sprayers inspected until now, have less than 5 years old. This means that the majority of the sprayers may not be in accordance with the standards and the article 8 of the European Directive

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)

Infrared phonon dynamics of multiferroic BiFeO3 single crystal

We discuss the first infrared reflectivity measurement on a BiFeO3 single crystal between 5 K and room temperature. The 9 predicted ab-plane E phonon modes are fully and unambiguously determined. The frequencies of the 4 A1 c-axis phonons are found. These results settle issues between theory and data on ceramics. Our findings show that the softening of the lowest frequency E mode is responsible for the temperature dependence of the dielectric constant, indicating that the ferroelectric transition in BiFeO3 is soft-mode driven.Comment: 5 pages (figures included

Physical activity habits of the ESPN pupils and its relation with health pointers

This study intends to characterize habits and preferences concerned with physical activity of the Secondary School Pedro Nunes students. Moreover, we intended to understand the relation between some aspects of physical activity (volume: number of hours/week) and practice type (formal and informal practice) and health indicators: body composition, aerobic and muscular ability. With this study we also wish to promote among the scholar field the discussion on the role of the school and the physical education in the development and maintenance of the physical aptitude of the young people and the adoption of healthful habits of life.FCT (Fundação para a Ciência e a Tecnologia), IDP (Instituto do Desporto de Portugal), AIESEP World Congres