Surface magnon-polaritons at a dielectric/graphene/gyromagnetic interface in a perpendicular applied magnetic field.

We present a theoretical study of the surface magnon-polaritons at an interface formed by vacuum and a gyromagnetic medium (that can be either ferromagnetic or antiferromagnetic), when there is a graphene layer deposited between the media at the interface and a magnetic field is applied perpendicular to the interface. The retarded-mode dispersion relations are calculated by considering a superposition of transverse magnetic and transversal electric electromagnetic waves in both media. Our results reveal the appearance of the surface magnon-polariton modes (with frequencies typically of a few GHz) that do not exist in the absence of graphene at the interface. Also, a typical magnon-polariton dispersion relation with damping is revealed, including a resonant frequency that depends on the applied magnetic field. The effects of varying the doping levels, which modify the Fermi energies in the graphene, and varying the perpendicular applied magnetic field are presented, revealing a strong influence exerted by the presence of graphene on the surface magnon-polariton modes. Other effects include the control of the slope of the dispersion curves (with respect to the in-plane wave vector) for the modes as the Fermi energies of the graphene sheet are changed and the distinctive localization properties for the emerging surface modes.

Magnon-polaritons in ferromagnetic magnonic crystals with graphene at the interfaces.

We present a theoretical study for the surface and bulk magnon-polaritons in magnonic crystals (or semi-infinite layered superlattices), which are formed from an array of ferromagnetic materials and nonmagnetic spacers with graphene sheets interposed between them. The external medium is taken to be vacuum. The Fermi energies in the graphene can be varied by employing different electronic doping levels, resulting in a strong influence exerted by the presence of graphene on the surface magnon-polariton modes. These effects include localization of the modes and control of the group velocities of the modes as the Fermi energies of the graphene sheets are varied, along with an important role for the phenomenological damping in the graphene sheets.

Magnon-polaritons in graphene/gyromagnetic slab heterostructures.

We present a theoretical study for the surface magnon-polaritons in structures formed by graphene layer(s) on an insulating gyromagnetic medium (that can be either ferromagnetic or antiferromagnetic) surrounded by vacuum. We consider different doping levels to vary the Fermi energies in the graphene, including both semi-infinite and slab magnetic samples. Our results reveal a strong influence, exerted by the presence of graphene, on the surface magnon-polariton modes. The effects include control of the group velocities for the modes as the Fermi energies of the graphene sheet are varied, modified nonreciprocal and reciprocal mode propagation properties depending on the type of magnetic material, and distinct localization properties for the emerging surface modes.

Phononic topological states in 1D quasicrystals.

In this work, we address the study of phonons propagating on a one-dimensional quasiperiodic lattice, where the atoms are considered bounded by springs whose strength are modulated by equivalent Aubry-André hoppings. As an example, from the equations of motion, we obtained the equivalent phonon spectrum of the well known Hofstadter butterfly. We have also obtained extended, critical, and localized regimes in this spectrum. By introducing the equivalent Aubry-André model through the variation of the initial phase [Formula: see text], we have shown that border states for phonons are allowed to exist. These states can be classified as topologically protected states (topological states). By calculating the inverse participation rate, we describe the localization of phonons and verify a phase transition, characterized by the critical value of [Formula: see text], where the states of the system change from extended to localized, precisely like in a metal-insulator phase transition.

Erratum: Critical properties of a two-dimensional Ising magnet with quasiperiodic interactions [Phys. Rev. E 93, 042111 (2016)].

This corrects the article DOI: 10.1103/PhysRevE.93.042111.

Erratum: Critical properties of a two-dimensional Ising magnet with quasiperiodic interactions [Phys. Rev. E 93, 042111 (2016)].

This corrects the article DOI: 10.1103/PhysRevE.93.042111.

Critical properties of a two-dimensional Ising magnet with quasiperiodic interactions.

We address the study of quasiperiodic interactions on a square lattice by using an Ising model with ferromagnetic and antiferromagnetic exchange interactions following a quasiperiodic Fibonacci sequence in both directions of a square lattice. We applied the Monte Carlo method, together with the Metropolis algorithm, to calculate the thermodynamic quantities of the system. We obtained the Edwards-Anderson order parameter q_{EA}, the magnetic susceptibility χ, and the specific heat c in order to characterize the universality class of the phase transition. We also use the finite size scaling method to obtain the critical temperature of the system and the critical exponents ß,γ, and ν. In the low-temperature limit we obtained a spin-glass phase with critical temperature around T_{c}≈2.274, and the critical exponents ß,γ, and ν, indicating that the quasiperiodic order induces a change in the universality class of the system. Also, we discovered a spin-glass ordering in a two-dimensional system which is rare and, as far as we know, the unique example is an under-frustrated Ising model.

Band gaps and transmission spectra in generalized Fibonacci σ(p,q) one-dimensional magnonic quasicrystals.

We employ a microscopic theory to investigate spin wave (magnon) propagation through their dispersion and transmission spectra in magnonic crystals arranged to display deterministic disorder. In this work the quasiperiodic arrangement investigated is the well-known generalized Fibonacci sequence, which is characterized by the σ(p,q) parameter, where p and q are non-zero integers. In order to determine the bulk modes and transmission spectra of the spin waves, the calculations are carried out for the exchange dominated regime within the framework of the Heisenberg model and taking into account the random phase approximation. We have considered magnetic materials that have a ferromagnetic order, and the transfer-matrix treatment is applied to simplify the algebra. The results reveal that spin wave spectra display a rich and interesting magnonic pass- and stop-bands structures, including an almost symmetric band gap distribution around of a mid-gap frequency, which depends on the Fibonacci sequence type.

Electronic properties of Fibonacci and random Si-Ge chains.

In this paper we address a theoretical calculation of the electronic spectra of an Si-Ge atomic chain that is arranged in a Fibonacci quasi-periodic sequence, by using a semi-empirical quantum method based on the Hückel extended model. We apply the Fibonacci substitutional sequences in the atomic building blocks A(Si) and B(Ge) through the inflation rule or a recursion relation. In our ab initio calculations we use only a single point, which is sufficient for considering all the orbitals and charge distribution across the entire system. Although the calculations presented here are more complete than the models adopted in the literature which take into account the electronic interaction only up to the second and third neighbors, an interesting property remains in their electronic spectra: the fractality (which is the main signature of this kind of system). We discuss this fractality of the spectra and we compare them with the random arrangement of the Si-Ge atomic chain, and with previous results based on the tight-binding approximation of the Schrödinger equation considering up to the nearest neighbor.

Fractal spectrum of charge carriers in quasiperiodic graphene structures.

In this work we investigate the interaction of charge carriers in graphene with a series of p-n-p junctions arranged according to a deterministic quasiperiodic substitutional Fibonacci sequence. The junctions create a potential landscape with quantum wells and barriers of different widths, allowing the existence of quasi-confined states. Spectra of quasi-confined states are calculated for several generations of the Fibonacci sequence as a function of the wavevector component parallel to the barrier interfaces. The results show that, as the Fibonacci generation is increased, the dispersion branches form energy bands distributed as a Cantor-like set. Besides, for a quasiperiodic set of potential barriers, we obtain the electronic tunneling probability as a function of energy, which shows a striking self-similar behavior for different generation numbers.

Network of healthy communities of Rio de Janeiro--Brazil

Poor communities in Rio de Janeiro, which are known as favelas, suffer from various problems related to poor housing, poverty, unemployment, violence and organized crime, and lack of access to basic services, such as health care and education. In order to tackle these determinants, and inspired by WHO's international Healthy Communities/Cities movement, the etwork of Healthy Communities of Rio de Janeiro was formed in 2004. The Network is coordinated by the Center for Health Promotion (CEDAPS) and now includes more than 100 community groups and organizations in the state of Rio de Janeiro. Their aim is to promote health, community development and equity through community empowerment, participation, capacity building and advocacy. The paper describes the work that has been done since the Network's inception and the challenges which they face to reach their goals in the context of a country like Brazil. The Network represents an important landmark of how poor populations can organize themselves in a collective, participatory and constructive way to influence public policy and strive for better conditions of life in disadvantaged settings, like the favelas. (AU)

Nucleotide correlations and electronic transport of DNA sequences.

We use a tight-binding formulation to investigate the transmissivity and wave-packet dynamics of sequences of single-strand DNA molecules made up from the nucleotides guanine G , adenine A , cytosine C , and thymine T . In order to reveal the relevance of the underlying correlations in the nucleotides distribution, we compare the results for the genomic DNA sequence with those of two artificial sequences: (i) the Rudin-Shapiro one, which has long-range correlations; (ii) a random sequence, which is a kind of prototype of a short-range correlated system, presented here with the same first-neighbor pair correlations of the human DNA sequence. We found that the long-range character of the correlations is important to the persistence of resonances of finite segments. On the other hand, the wave-packet dynamics seems to be mostly influenced by the short-range correlations.

Hepatic gluconeogenesis in rats trained to eat a single meal daily. Role of eating periodicity and the amount of food ingested in the last meal.

Rats trained to eat a single daily meal (MF rats), from 8:00-10:00 a.m., increased food intake from the 1st to the 12th (125%) day of feeding training. In this work we compared the influence of the higher food ingestion in the last meal and feeding training on hepatic gluconeogenesis. Thus, rats at the 1st (MF(1st day-5g) group) and 13th day (MF(13th day-5g) group) of training, refed with a fixed amount of food (5g) were employed. In addition, a third group of MF rats, refed on day 12 with 75% (12g) of the food ingested by MF rats on the 13th day of the feeding training (MF(13th day-12g)) was included. The experiments were performed at 22 h after meal (8:00 a.m.). Our results demonstrated that feeding training had a crucial role in determining gluconeogenesis from pyruvate (5 mM). Additionally, gluconeogenesis from L-glutamine (5 mM) was influenced by periodicity of eating and the amount of food ingested in the last meal. In contrast, gluconeogenesis from L-alanine (5 mM) was not influenced by both factors. In conclusion, our findings suggested that the hepatic gluconeogenesis was influenced by food ingestion and/or feeding training depending of the substrate investigated. These effects on gluconeogenesis may have implications for use in diabetic regimens.