Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto

About: Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto is a based out in . It is known for research contribution in the topics: Population & Catalysis. The organization has 2143 authors who have published 3674 publications receiving 71071 citations. The organization is also known as: FFCLRP & FFCLRP-USP.

Antioxidant Activity of an Aqueous Leaf Extract from Uncaria tomentosa and Its Major Alkaloids Mitraphylline and Isomitraphylline in Caenorhabditis elegans.

Abstract: Uncaria tomentosa (Rubiaceae) has a recognized therapeutic potential against various diseases associated with oxidative stress. The aim of this research was to evaluate the antioxidant potential of an aqueous leaf extract (ALE) from U. tomentosa, and its major alkaloids mitraphylline and isomitraphylline. The antioxidant activity of ALE was investigated in vitro using standard assays (DPPH, ABTS and FRAP), while the in vivo activity and mode of action were studied using Caenorhabditis elegans as a model organism. The purified alkaloids did not exhibit antioxidant effects in vivo. ALE reduced the accumulation of reactive oxygen species (ROS) in wild-type worms, and was able to rescue the worms from a lethal dose of the pro-oxidant juglone. The ALE treatment led to a decreased expression of the oxidative stress response related genes sod-3, gst-4, and hsp-16.2. The treatment of mutant worms lacking the DAF-16 transcription factor with ALE resulted in a significant reduction of ROS levels. Contrarily, the extract had a pro-oxidant effect in the worms lacking the SKN-1 transcription factor. Our results suggest that the antioxidant activity of ALE in C. elegans is independent of its alkaloid content, and that SKN-1 is required for ALE-mediated stress resistance.

Unconventional Fano effect and off-resonance field enhancement in plasmonic coated spheres

Abstract: We investigate light scattering by coated spheres composed of a dispersive plasmonic core and a dielectric shell. By writing the absorption cross section in terms of the internal electromagnetic fields, we demonstrate it is an observable sensitive to interferences that ultimately lead to the Fano effect. In particular, we show that unconventional Fano resonances, recently discovered for homogeneous spheres with large dielectric permittivities, can also occur for metallic spheres coated with single dielectric layers. These resonances arise from the interference between two electromagnetic modes with the same multipole moment inside the shell and not from interactions between the various plasmon modes of different layers of the particle. In contrast to the case of homogeneous spheres, unconventional Fano resonances in coated spheres exist even in the Rayleigh limit. These resonances can induce an off-resonance field enhancement, which is approximately 1 order of magnitude larger than the one achieved with conventional Fano resonances. We find that unconventional and conventional Fano resonances can occur at the same input frequency provided the dispersive core has a negative refraction index. This leads to an optimal field enhancement inside the particle, a result that could be useful for potential applications in plasmonics.

The Yukagua model of water

Abstract: Using the Invariant Expansion technique we show that the Multi-Yukawa closure of the Ornstein Zernike equation has an analytical solution for a model that reproduces well the known structure of water as measured by neutron diffraction. The model is an extension of earlier models based on the BBL model [1] , [2] : the analytical sticky octupolar potential and the soft version of that potential. In the present work the soft short-ranged effective potential is represented by a sum of Yukawa potentials. The models is tested by Monte Carlo computer simulation The atom–atom pair correlation functions for oxygen–oxygen, oxygen–hydrogen and hydrogen–hydrogen obtained for this new potential are in good agreement with the neutron scattering experiments. Because of its analyticity this model is especially suited for the investigation of the percolation transition for the hydrogen bonds, proposed by Stanley and collaborators [3] , [4] , [39] , [40] . The convergence in the simulations is very fast because the weakly directional octupolar potential have little trouble connecting to the tetrahedral first nearest neighbors. The observation made in the computer simulations is that small changes in the strength of the potential seem to lock in or lock out of the tetrahedral structure. This is interpreted as changes in temperature producing the percolation transition.

Nest architecture and distribution of the primitive stingless bee, Mourella caerulea (hymenoptera, apidae, meliponinae): Evidence for the origin of plebeia (s. lat.) on the gondwana continent∗

Abstract: The stingless bee Mourella caerulea is distributed in the subtropical parts of Brazil, Argentina and Paraguai. In the Serra do Sudeste of Rio Grande do Sul, on the southern part of the Brazilian shield, this species is one of the most abundant meliponine bees. Nests of M. caerulea are built in the soil and exhibit architectural characters typical to all other genera of obligatory ground nesting species, like Schwarziana, and the African genera Meliple‐beia, Plebeiella and Plebeina. The possibility that the similar solutions for the construction of subterranean nests in these genera did not evolve by convergence or parallelism is discussed. The occurence of Mourella together with other more primitive representatives of the Plebeia group on the southern parts of the Brazilian Shield cannot be explained by biogeographic models proposed by some authors. Adopting an alternative model we suggest that, during the lower Cretaceous, ancestor populations of the Pleibeia‐ line inhabiting the meridional shields of We...