Valley polarization effects on the localization in graphene Landau levels

Effects of disorder and valley polarization in graphene are investigated in the quantum Hall regime. We find anomalous localization properties for the lowest Landau level (LL), where disorder can induce wavefunction delocalization (instead of localization), both for white-noise and gaussian-correlated disorder. We quantitatively identify the contribution of each sublattice to wavefunction amplitudes. Following the valley (sublattice) polarization of states within LLs for increasing disorder we show: (i) valley mixing in the lowest LL is the main effect behind the observed anomalous localization properties, (ii) the polarization suppression with increasing disorder depends on the localization for the white-noise model, while, (iii) the disorder induces a partial polarization in the higher Landau levels for both disorder models.Comment: 5 pages, 6 figures, extended version, with 2 new figures adde

Resonant tunneling through protected quantum dots at phosphorene edges

We theoretically investigate phosphorene zigzag nanorribons as a platform for constriction engineering. In the presence of a constriction at the upper edge, quantum confinement of edge protected states reveals resonant tunnelling Breit-Wigner transmission peaks, if the upper edge is uncoupled to the lower edge. Coupling between edges in thin constrictions gives rise to Fano-like and anti-resonances in the transmission spectrum of the system.Comment: 8 pages,7 figure

À descoberta de sofware para explorar a programação linear no ensino secundário

A Programação Linear, PL, tem como objectivo a resolução de problemas de optimização com restrições em que todas as funções envolvidas são lineares. Diversos problemas da vida real podem ser formulados como problemas de PL como, por exemplo, os problemas de planeamento e de transportes. A Programação Linear é um dos temas obrigatórios de algumas disciplinas de Matemática do Ensino Secundário, sendo importante que se trabalhem com os alunos problemas que traduzam situações reais, ou suas adaptações. Como estes problemas nem sempre são fáceis e rápidos de resolver, a utilização de ferramentas tecnológicas na sua resolução reveste-se de enorme importância. Existem diversos programas de computador como o Solver do Microsoft Office Excel, o WinQSB, o Programación Lineal e o Winplot, de fácil utilização pelos alunos, que possibilitam a exploração gráfica, no caso bidimensional, ou analítica dos problemas de PL. O uso deste software permite que os alunos resolvam uma maior diversidade de problemas e se centrem mais na análise e interpretação de resultados. Neste artigo, ilustra-se, resumidamente, a forma de resolver problemas de PL com o software mencionado e discute-se as suas potencialidades e limitações

Linear programming knowledge in first stage higher education courses

In this work we will describe an experimental study with approximately fifty Portuguese students of the 2nd year of the BSc Degree of Biomedical Engineering as well as Chemical and Biological Engineering Higher Education Courses. The aims of this study are to identify which knowledge of Linear Programming (LP) taught in High School the students acquired and still remember, which tools they used in that stage of education when learning the theme of LP and their opinion about the significance of LP in daily life problem resolution. We also propose to investigate if the students are able to use WinQSB software to solve LP problems. In addition, we intend to identify not only the versatility of this software but also the opinion of the students about the resolution of LP problems with WinQSB, as well as their main difficulties during this experience

Preface of the “Symposium on numerical optimization and applications”

[Excerpt] Numerical Optimization and Applications Symposium emphasizes modeling, theory and study of numerical algorithms for optimization. Optimization is an important tool in decision science and in the analysis of physical systems. Furthermore the Optimization plays central role in a tremendous variety of application in the natural sciences, in the sectors of economy, finance, and industry operational research and in the engineering. Because of the wide and growing use of optimization, it is important to develop an understanding of optimization algorithms. Knowledge of the capabilities and limitations of these algorithms leads to a better understanding of their impact on various applications, and points the way to future research on improving and extending optimization algorithms and software. [...](undefined

Sound production in the Meagre, Argyrosomus regius (Asso, 1801): intraspecific variability associated with size, sex and context

Many fish taxa produce sound in voluntary and in disturbance contexts but information on the full acoustic repertoire is lacking for most species. Yet, this knowledge is critical to enable monitoring fish populations in nature through acoustic monitoring.Portuguese Foundation for Science and Technology: PTDC/BIA-BMA/30517/2017; SFRH/BD/115562/2016; UID/MAR/04292/2019; UID/BIA/00329/2019; PTDC/BIA-BMA/29662/2017.info:eu-repo/semantics/publishedVersio

A step for the valorization of spent yeast through production of iron–peptide complexes — a process optimization study

Given the importance of iron in human nutrition and the significance of waste and by-product valorisation in a circular economy environment, we investigated the effects of protein and iron concentration on the production yield of iron–peptide complexes from spent Saccharomyces cerevisiae. For this purpose, different amounts of protein and iron were used in the complexation process. The results have shown that higher concentrations, although permitting a faster and larger scale process, provide a significantly lower complexation yield, which deems the process less feasible. This is corroborated by fluorescence analysis, which shows a lower degree of complexation with higher protein concentration. In addition, varying the concentration of iron does not change the quality of formed complexes, as evidenced by Fourier transform infrared spectroscopy (FT-IR) analysis. The morphology of all samples was also evaluated using scanning electron microscopy (SEM). Therefore, further studies are needed to optimize the process and to evaluate the best conditions for an economically sound valorization process for iron–peptide complexes. Nonetheless, current results in the development of a new process for the valorisation of spent yeast, in the form of iron-peptide complexes, look promising.info:eu-repo/semantics/publishedVersio