Strain Engineering of Photo-induced Topological Phases in 2D Ferromagnets

We argue that strain engineering is a powerful tool which may facilitate the experimental realization and control of topological phases in laser-driven 2D ferromagnetic systems. To this extent, we show that by applying a circularly polarized laser field to a 2D honeycomb ferromagnet which is uniaxially strained in either the zig-zag or armchair direction, it is possible to generate a synthetic Dzyaloshinskii-Moriya interaction (DMI) tunable by the intensity of the applied electric field, as well as by the magnitude of applied strain. Such deformations enable transitions to phases with opposite sign of Chern number, or to trivial phases. These are basic results that could pave the way for the development of a new field of Strain Engineered Topological Spintronics (SETS).Comment: 11 pages; enlarged version relatively to version V

Two-level systems coupled to Graphene plasmons: a Lindblad equation approach

In this paper, we review the theory of open quantum systems and macroscopic quantum electrodynamics, providing a self-contained account of many aspects of these two theories. The former is presented in the context of a qubit coupled to a electromagnetic thermal bath, the latter is presented in the context of a quantization scheme for surface-plasmon polaritons (SPPs) in graphene based on Langevin noise currents. This includes a calculation of the dyadic Green’s function (in the electrostatic limit) for a Graphene sheet between two semi-infinite linear dielectric media, and its subsequent application to the construction of SPP creation and annihilation operators. We then bring the two fields together and discuss the entanglement of two qubits in the vicinity of a graphene sheet which supports SPPs. The two qubits communicate with each other via the emission and absorption of SPPs. We find that a Schrödinger cat state involving the two qubits can be partially protected from decoherence by taking advantage of the dissipative dynamics in graphene. A comparison is also drawn between the dynamics at zero temperature, obtained via Schrödinger’s equation, and at finite temperature, obtained using the Lindblad equation

The polarizability of a confined atomic system: an application of the Dalgarno-Lewis method

In this paper we give an application of the Dalgarno–Lewis method, the latter not usually taught in quantum mechanics courses. This is very unfortunate since this method allows one to bypass the sum over states appearing in the usual perturbation theory. In this context, and as an example, we study the effect of an external field, both static and frequency-dependent, on a model atom at fixed distance from a substrate. This can happen, for instance, when some organic molecule binds from one side to the substrate and from the other side to an atom or any other polarizable system. We model the polarizable atom by a short range potential, a Dirac-δ, and find that the existence of a bound state depends on the ratio of the effective 'nuclear charge' to the distance of the atom from the substrate. Using an asymptotic analysis, previously developed in the context of a single δ-function potential in an infinite medium, we determine the ionization rate and the Stark shift of our system. Using Dalgarno–Lewis theory we find an exact expression for the static and dynamic polarizabilities of our system valid to all distances. We show that the polarizability is extremely sensitive to the distance from the substrate, creating the possibility of using this quantity as a nanometric ruler. Furthermore, the line shape of the dynamic polarizability is also extremely sensitive to the distance from the substrate, thus providing another route to measure nanometric distances. The didactic value of the δ-function potential is widely accepted in teaching activities due to its simplicity, while still keeping the essential ingredients of a given problem.The authors acknowledge João Carlos Henriques and Thomas G Pedersen for many discussions and exchanges of ideas on this topic. NMRP acknowledges support from the European Commission through the project 'Graphene-Driven Revolutions in ICT and Beyond' (Ref. No. 785219), and the Portuguese Foundation for Science and Technology (FCT) in the framework of Strategic Financing UID/FIS/04650/2019. In addition, he acknowledges COMPETE2020, PORTUGAL2020, FEDER and the Portuguese FCT through Projects POCI-01-0145-FEDER-028114, POCI-01-0145-FEDER-029265, PTDC/NAN-OPT/29265/2017, and POCI-01-0145-FEDER-02888. TVCA acknowledges the FCT for a grant given in the context of the 'Quantum Matter|Materials and Concepts Summer Training Program 2020'

OC28 - Effect of mode of delivery on early oral colonization and childhood dental caries: a systematic review

BACKGROUND:Oral colonization starts at birth by vertical transmission. OBJECTIVE:To determine whether mode of delivery influences the oral colonization of infants and contributes to the risk of childhood dental caries. METHODS:A systematic review was conducted in the electronic database Web of Science for articles published from January 1995 to December 2015 by using a set of keywords. RESULTS:From 2,644 citations identified through electronic search, ten studies met the inclusion criteria. According to the studies mode of delivery influences oral microbial density, oral microbial profile and the timing of oral colonization by cariogenic microbiota. However, there are no consistent results concerning either the prevalence of children harboring cariogenic microbiota or the prevalence of early childhood caries by mode of delivery. CONCLUSION:Mode of delivery influences early oral colonization. However, it seems that other determinants rather than mode of delivery could be major contributors to the development of early childhood caries

Upper and lower bounds for the bearing capacity of foundations on soft soils with reinforcement columns

The finite element program mechpy, developed within the authors’ team, which implements the upper and lower bound theorems of limit analysis, is applied to the calculation of the bearing capacity of foundations on soft soils improved with reinforcement columns. The problem is analysed in two and threedimensions, considering the soil and the columns responding under undrained conditions, using different replacement area ratios and different column-to-soil shear strength ratios. The upper and lower bound results are found to be in a narrow range and in good agreement with experimental results found in the literature. A simple equation is proposed to evaluate the bearing capacity of soil reinforced with columns.publishersversionpublishe

Caracterização física e química de maracujá-do-mato (Passiflora cincinnata Mast.) colhido em dois estádios de maturação.

Este trabalho teve como objetivo a caracterização física e química do maracuja-do-mato (Passiflora cincinnata Mast.) colhido em dois estádios de maturação

Utilização de revestimentos à base de alginato na conservação pós-colheita de manga Tommy Atkins.

O objetivo deste estudo foi avaliar a qualidade de mangas Tommy Atkins após a aplicação de revestimentos ‡ base de alginato e mantidas sob armazenamento refrigerado seguido de temperatura ambiente