Feiras livres como alternativa de comercialização de produtos da agrofloresta.

Com a busca por alternativas comerciais socialmente justas como maneira de otimizar a comercialização de produtos provenientes de agricultura familiar, destaca se a venda direta através de feiras, livres, que permite acesso direto ao consumidor sem necessidade de intermediadores. O Grupo de Produtores Agroflorestais Gralha Azul, de Morretes-PR, iniciou plantios de agroflorestas agroecológicas em 2009, sendo formado, atualmente, por 12 famílias de agricultores. Há um ano, o Gralha Azul iniciou sua participação na Matinfeira, feira semanal de produtos da agricultura familiar em Matinhos, PR. Com o objetivo de caracterização dos produtos, produtores e do processo de comercialização, foram acompanhados e sistematizados em planilha a comercialização destes produtos em 22 feiras semanais, entre maio e dezembro de 2012. Onze produtores participaram da Matinfeira, comercializando entre 13 e 29 variedades de alimentos, e proporcionando uma renda que variou de R$101,00 a R$ 386,50, por semana. Mensalmente, as feiras permitiram uma receita bruta de R$ 141,17 por produtor familiar agroflorestal. Apesar desse baixo valor, há que se considerar que o mesmo reflete os primeiros seis meses de atuação do Grupo no processo de comercialização na feira (Matinfeira). A venda direta através desta feira livre mostra potencial como alternativa comercial socialmente justa para os produtores em transição agroecológica do Grupo Gralha Azul

Diamagnetism above Tc in underdoped Bi2.2Sr1.8Ca2Cu3O10+d

Single crystals of ${\rm Bi}_{2+x}{\rm Sr}_{2-x}{\rm Ca}_{2}{\rm Cu}_{3}{\rm O}_{10+\delta}$(Bi2223) with $x=0.2$ were grown by a traveling solvent floating zone method in order to investigate the superconducting properties of highly underdoped Bi2223.Grown crystals were characterized by X-ray diffraction, DC susceptibility and resistivity measurements, confirming Bi2223 to be the main phase.The crystals were annealed under various oxygen partial pressures to adjust their carrier densities from optimally doped to highly underdoped.The fluctuation diamagnetic component above the superconducting transition temperature $T_{\rm c}$ extracted from the anisotropic normal state susceptibilities $\chi_{ab}(T)$ ($H\perp c$) and $\chi_{c}(T)$ ($H\parallel c$) was found to increase with underdoping, suggesting a decrease in the superconducting dimensionality and/or increase in the fluctuating vortex liquid region.Comment: 6 pages, 7 figures, corrected fig.4 and references, published in J. Phys. Soc. Jpn. 79, 114711 (2010

Radial distribution of the multiple stellar populations in omega Centauri

We present a detailed study of the radial distribution of the multiple populations identified in the Galactic globular cluster omega Cen. We used both space-based images (ACS/WFC and WFPC2) and ground-based images (FORS1@VLT and [email protected] ESO telescopes) to map the cluster from the inner core to the outskirts (~20 arcmin). These data sets have been used to extract high-accuracy photometry for the construction of color-magnitude diagrams and astrometric positions of ~900 000 stars. We find that in the inner ~2 core radii the blue main sequence (bMS) stars slightly dominate the red main sequence (rMS) in number. At greater distances from the cluster center, the relative numbers of bMS stars with respect to rMS drop steeply, out to ~8 arcmin, and then remain constant out to the limit of our observations. We also find that the dispersion of the Gaussian that best fits the color distribution within the bMS is significantly greater than the dispersion of the Gaussian that best fits the color distribution within the rMS. In addition, the relative number of intermediate-metallicity red-giant-branch stars which includes the progeny of the bMS) with respect to the metal-poor component (the progeny of the rMS) follows a trend similar to that of the main-sequence star-count ratio N_bMS/N_rMS. The most metal-rich component of the red-giant branch follows the same distribution as the intermediate-metallicity component. We briefly discuss the possible implications of the observed radial distribution of the different stellar components in omega Cen.Comment: 16 pages, 14 figures (6 in low resolution), 3 tables. Accepted for publication in Astronomy and Astrophysics on 23 September 200

Dependence of carrier doping on the impurity potential in transition-metal-substituted FeAs-based superconductors

In order to examine to what extent the rigid-band-like electron doping scenario is applicable to the transition metal-substituted Fe-based superconductors, we have performed angle-resolved photoemission spectroscopy studies of Ba(Fe$_{1-x}$Ni$_{x}$)$_2$As$_2$ (Ni-122) and Ba(Fe$_{1-x}$Cu$_{x}$)$_2$As$_2$ (Cu-122), and compared the results with Ba(Fe$_{1-x}$Co$_x$)$_2$As$_2$ (Co-122). We find that Ni 3$\it{d}$-derived features are formed below the Fe 3$\it{d}$ band and that Cu 3$\it{d}$-derived ones further below it. The electron and hole Fermi surface (FS) volumes are found to increase and decrease with substitution, respectively, qualitatively consistent with the rigid-band model. However, the total extra electron number estimated from the FS volumes (the total electron FS volume minus the total hole FS volume) is found to decrease in going from Co-, Ni-, to Cu-122 for a fixed nominal extra electron number, that is, the number of electrons that participate in the formation of FS decreases with increasing impurity potential. We find that the N$\acute{\rm{e}}$el temperature $T_{\rm{N}}$ and the critical temperature $T_{\it{c}}$ maximum are determined by the FS volumes rather than the nominal extra electron concentration nor the substituted atom concentration.Comment: Total: 9 pages, 10 figure

Pseudogap, Superconducting Gap, and Fermi Arc in High-Tc Cuprates Revealed by Angle-Resolved Photoemission Spectroscopy

We present an overview of angle-resolved photoemission spectroscopy (ARPES) studies of high-temperature cuprate superconductors aiming at elucidating the relationship between the superconductivity, the pseudogap, and the Fermi arc. ARPES studies of underdoped samples show a momentum dependence of the energy gap below Tc which deviates from a simple d-wave form, suggesting the coexistence of multiple energy scales in the superconducting state. Hence, two distinct energy scales have been introduced, namely, the gap near the node (characterized by Delta_0) and in the anti-nodal region (characterized by Delta^*). Dichotomy between them has been demonstrated from the material, doping, and temperature dependence of the energy gap. While Delta^* at the same doping level is approximately material independent, Delta_0 shows a strong material dependence tracking the magnitude of Tc,max. The anti-nodal gap does not close at Tc in contrast to the gap near the node which follows something closer to a BCS-like temperature dependence. An effective superconducting gap Delta_sc defined at the end point of the Fermi arc is found to be proportional to Tc's in various materials.Comment: 20 pages, 10 figures, (SPECIAL TOPICS: Recent Developments in Superconductivity, in Journal of the Physical Society of Japan