Spin-phonon coupling in Gd(Co1/2Mn1/2)O3 perovskite

We have investigated the temperature-dependent Raman-active phonons and the magnetic properties of Gd(Co1/2Mn1/2)O3 perovskite ceramics in the temperature range from 40 K to 300 K. The samples crystallized in an orthorhombic distorted simple perovskite, whose symmetry belongs to the Pnma space group. The data reveals spin-phonon coupling near the ferromagnetic transition occurring at around 120 K. The correlation of the Raman and magnetization data suggests that the structural order influences the magnitude of the spin-phonon coupling.Comment: 3 Figures, suplementary materia

On the appropriateness of use of a continuous formulation for the modelling of discrete multireactant systems following Michaëlis-Menten kinetics

The possibility of solving the mass balances to a multiplicity of substrates within a CSTR in the presence of a chemical reaction following Michaelis-Menten kinetics using the assumption that the discrete distribution of said substrates is well approximated by an equivalent continuous distribution on the molecular weight is explored. The applicability of such reasoning is tested with a convenient numerical example. In addition to providing the limiting behavior of the discrete formulation as the number of homologous substrates increases, the continuous formulation yields in general simpler functional forms for the final distribution of substrates than the discrete counterpart due to the recursive nature of the solution in the latter case

Efficient Video Indexing on the Web: A System that Leverages User Interactions with a Video Player

In this paper, we propose a user-based video indexing method, that automatically generates thumbnails of the most important scenes of an online video stream, by analyzing users' interactions with a web video player. As a test bench to verify our idea we have extended the YouTube video player into the VideoSkip system. In addition, VideoSkip uses a web-database (Google Application Engine) to keep a record of some important parameters, such as the timing of basic user actions (play, pause, skip). Moreover, we implemented an algorithm that selects representative thumbnails. Finally, we populated the system with data from an experiment with nine users. We found that the VideoSkip system indexes video content by leveraging implicit users interactions, such as pause and thirty seconds skip. Our early findings point toward improvements of the web video player and its thumbnail generation technique. The VideSkip system could compliment content-based algorithms, in order to achieve efficient video-indexing in difficult videos, such as lectures or sports.Comment: 9 pages, 3 figures, UCMedia 2010: 2nd International ICST Conference on User Centric Medi

O enriquecimento e a trituração da capoeira promovem a conservação da biodiversidade do solo no mosaico da agricultura familiar na Amazônia Oriental.

A paisagem fragmentada (mosaico) que resulta da agricultura familiar de corte-queima é mais amigável com o meio ambiente e a biodiversidade vegetal do que a agricultura de larga escala. No entanto, a diminuição do tempo de pousio e a redução das florestas maduras na paisagem ameaçam a sustentabilidade desse modelo de agricultura. O déficit de acumulo de biomassa leva a queda de nutrientes no solo e de produção. Nesse contexto, o enriquecimento de capoeiras e a substituição do uso do fogo pela trituração da biomassa são práticas agroflorestais que conservam os nutrientes, protegem o solo e sustentam a produção. No entanto, o potencial de conservação da diversidade do solo dessas práticas é pouco documentado. Nesse estudo, avaliou-se a diversidade de minhocas, formigas (gêneros) e grupos funcionais da macrofauna do solo em seis usos do solo: roça com queima; roça com trituração de capoeira enriquecida; pasto com queima; pasto com trituração da capoeira natural; capoeira de 20 e de 40 anos em Igarapé-Açu (Pará, Brasil). Calculou-se o índice INDVAL para identificar os táxons indicadores dos usos do solo. A roça com trituração tem uma diversidade de grupos funcionais similar a capoeira antiga e, de acordo com o INDVAL, hospeda populações especificas de gastrópodos e homópteros, conservando uma parcela exclusiva da biodiversidade do solo nessa paisagem. Esse resultado reforça a necessidade de introduzir práticas agroflorestais sem fogo na agricultura familiar e a importância de conservar capoeiras antigas na ausência de florestas primárias.Editores técnicos: Roberto Porro, Milton Kanashiro, Maria do Socorro Gonçalves Ferreira, Leila Sobral Sampaio e Gladys Ferreira de Sousa

Insights into the fracture mechanisms and strength of amorphous and nanocomposite carbon

Tight-binding molecular dynamics simulations shed light into the fracture mechanisms and the ideal strength of tetrahedral amorphous carbon and of nanocomposite carbon containing diamond crystallites, two of the hardest materials. It is found that fracture in the nanocomposites, under tensile or shear load, occurs inter-grain and so their ideal strength is similar to the pure amorphous phase. The onset of fracture takes place at weakly bonded sp^3 sites in the amorphous matrix. On the other hand, the nanodiamond inclusions significantly enhance the elastic moduli, which approach those of diamond.Comment: 6 pages, 4 figure