Wannier-Stark ladders in one-dimensional elastic systems

The optical analogues of Bloch oscillations and their associated Wannier-Stark ladders have been recently analyzed. In this paper we propose an elastic realization of these ladders, employing for this purpose the torsional vibrations of specially designed one-dimensional elastic systems. We have measured, for the first time, the ladder wave amplitudes, which are not directly accessible either in the quantum mechanical or optical cases. The wave amplitudes are spatially localized and coincide rather well with theoretically predicted amplitudes. The rods we analyze can be used to localize different frequencies in different parts of the elastic systems and viceversa.Comment: 10 pages, 6 figures, accepted in Phys. Rev. Let

Mercury removal in wastewater by iron oxide nanoparticles

Mercury is one of the persistent pollutants in wastewater; it is becoming a severe environmental and public health problem, this is why nowadays its removal is an obligation. Iron oxide nanoparticles are receiving much attention due to their properties, such as: great biocompatibility, ease of separation, high relation of surface-area to volume, surface modifiability, reusability, excellent magnetic properties and relative low cost. In this experiment, Fe3O4 and γ-Fe2O3 nanoparticles were synthesized using iron salts and NaOH as precipitation agents, and Aloe Vera as stabilizing agent; then these nanoparticles were characterized by three different measurements: first, using a Zetasizer Nano ZS for their size estimation, secondly UV-visible spectroscopy which showed the existence of resonance of plasmon at λmax∼360 nm, and lastly by Scanning Electron Microscopy (SEM) to determine nanoparticles form. The results of this characterization showed that the obtained Iron oxides nanoparticles have a narrow size distribution (∼100nm). Mercury removal of 70% approximately was confirmed by atomic absorption spectroscopy measurements

Necessary conditions for classical super-integrability of a certain family of potentials in constant curvature spaces

We formulate the necessary conditions for the maximal super-integrability of a certain family of classical potentials defined in the constant curvature two-dimensional spaces. We give examples of homogeneous potentials of degree -2 on $E^2$ as well as their equivalents on $S^2$ and $H^2$ for which these necessary conditions are also sufficient. We show explicit forms of the additional first integrals which always can be chosen polynomial with respect to the momenta and which can be of an arbitrary high degree with respect to the momenta

Quantifying structural damage from self-irradiation in a plutonium superconductor

The 18.5 K superconductor PuCoGa5 has many unusual properties, including those due to damage induced by self-irradiation. The superconducting transition temperature decreases sharply with time, suggesting a radiation-induced Frenkel defect concentration much larger than predicted by current radiation damage theories. Extended x-ray absorption fine-structure measurements demonstrate that while the local crystal structure in fresh material is well ordered, aged material is disordered much more strongly than expected from simple defects, consistent with strong disorder throughout the damage cascade region. These data highlight the potential impact of local lattice distortions relative to defects on the properties of irradiated materials and underscore the need for more atomic-resolution structural comparisons between radiation damage experiments and theory.Comment: 7 pages, 5 figures, to be published in PR

Agrupamento não hierárquico de acessos de germoplasma de mandioca (Manihot esculenta Crantz) com base em características quantitativas.

Os recursos genéticos de mandioca (Manihot esculenta Crantz) são utilizados como fonte de variação genética para incorporação de genes de elevado interesse agronômico em novas variedades de mandioca. Muitas características importantes ainda nem foram descobertas neste germoplasma, mas de maneira geral a busca por novos alelos para características tradicionalmente importantes no sistema de produção da mandioca como aquelas relacionadas ao aumento de produtividade, teor e qualidade de amido, resistência à seca, pragas e doenças ainda continua sendo uma linha de pesquisa extremamente importante como uma etapa que antecede o seu uso nos programas de melhoramento. O conhecimento da variação fenotípica do germoplasma de mandioca permite conhecer a real variabilidade genética, e subsidiar a seleção de parentais geneticamente divergentes, que poderão ser utilizados em intercruzamentos para se obter alto efeito heterótico e aumentar assim aumentar a probabilidade de recuperação de segregantes superiores em gerações avançadas. Embora diversos métodos estejam disponíveis para analisar a variação fenotípica, alguns métodos não hierárquicos como o k-means tem se destacado no agrupamento de genótipos especialmente quando há um grande conjunto de dados. Assim, o objetivo deste trabalho foi definir agrupamentos homogêneos de acessos de germoplasma de mandioca com base em características produtivas e de qualidade da raíz

Non-hierarchical clustering of cassava germoplasm based on quantitative traits.

The knowledge of the phenotypic variation of cassava (Manihot esculenta Crantz) germplasm allows estimating the genetic variability to support the selection of contrasting genitors. Therefore, the aim of this work was to define homogeneous groups of cassava germplasm based on yield traits, disease resistance and rot quality using k-means as a non-hierarchical method