10,621 research outputs found
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 is observed in the optimally-doped
thin films around and attributed to
manifestation of strong spin fluctuations induced by moments with the
energy . In addition to fluctuation
induced contribution due to thermal broadening effects (of the
width ), the experimental data are found to be well fitted
accounting for residual (zero-temperature) , electron-phonon and electron-electron contributions. The
best fits produced , ,
, and 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
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