Electronic oscillations in paired polyacetylene chains

An interacting pair of polyacetylene chains are initially modeled as a couple of undimerized polymers described by a Hamiltonian based on the tight-binding model representing the electronic behavior along the linear chain, plus a Dirac's potential double well representing the interaction between the chains. A theoretical field formalism is employed, and we find that the system exhibits a gap in its energy band due to the presence of a mass-matrix term in the Dirac's Lagrangian that describes the system. The Peierls instability is introduced in the chains by coupling a scalar field to the fermions of the theory via spontaneous symmetry breaking, to obtain a kink-like soliton, which separates two vacuum regions, i.e., two spacial configurations (enantiomers) of the each molecule. Since that mass-matrix and the pseudo-spin operator do not commute in the same quantum representation, we demonstrate that there is a particle oscillation phenomenon with a periodicity equivalent to the Bloch oscillations.Comment: 4 pages, 1 figure.to appear in Solid State Communication

Parental Monitoring and Youth's Binge Behaviors: The Role of Sensation Seeking and Life Satisfaction

Framed within an ecological perspective of the onset of adolescent problem behaviors, the current study explored the joint role of parent-adolescents’ relationships and youth's individual factors in binge eating and drinking. Firstly, in line with pieces of research highlighting the beneficial impact of effective parenting on youth development, the present paper sought to enhance the knowledge about the positive influence of parental monitoring on youth's binge drinking and eating. Moreover, since literature evidenced that the explanatory mechanisms of the association between parental monitoring and binge behaviors are not fully explored, the study focused on the potential intervening role of sensation seeking and life satisfaction as mediators. The study design was cross-sectional and self-report questionnaires were administered among a population of 944 high school students (M = 16.35, SD = 1.31) living in Palermo (Italy). Path analysis showed that parental monitoring was directly and negatively related to both binge eating and binge drinking. Moreover, sensation seeking negatively mediated the relationships between parental monitoring and both binge behaviors, whereas life satisfaction only mediated between parental monitoring and binge eating. The current study provided data useful to understand the complex interrelations between intrapersonal (life satisfaction and personality trait, i.e. sensation seeking) and contextual factors (parent–child relationships) that may discourage or cause eating and alcohol use disorders among youth. Finally, implications for parents and practitioners working with youngsters were discussed

Experimental characterization of the structural response of adobe arches

Earth was one of the first construction materials used by mankind and has been used as a building material since ancient times until the present days. Its qualities related to thermal comfort, low cost or simple construction techniques have contributed to such a long tradition throughout the world with several different architectural expressions, integrating the culture and history of each region. With the wide propagation of steel and concrete structures, there has been a general loss of the traditional knowledge in earth construction. This type of construction presents important structural fragilities and requires a special maintenance to preserve its qualities. In order to understand the structural behaviour of this type of structures, the associated construction methods and processes have to be considered. Aveiro University has been developing studies on adobe constructions, with research on the material mechanical characterization, experimental study of the structural behaviour of adobe masonry walls and, more recently, in the development of a detailed survey methodology for the characterization of buildings in Aveiro district. Integrated in these studies, arches with different geometries were built using adobe blocks and traditional construction methods. These arches were tested under different types of vertical loading (distributed symmetrical, distributed non-symmetrical and point load) until collapse. The experimental tests performed reproduce the typical loading conditions of these structures during construction and use. The tests conducted, the results obtained and the main conclusions attained are described in this paper

Gravitational waves from pulsars with measured braking index

We study the putative emission of gravitational waves (GWs) in particular for pulsars with measured braking index. We show that the appropriate combination of both GW emission and magnetic dipole brakes can naturally explain the measured braking index, when the surface magnetic field and the angle between the magnetic dipole and rotation axes are time dependent. Then we discuss the detectability of these very pulsars by aLIGO and the Einstein Telescope. We call attention to the realistic possibility that aLIGO can detect the GWs generated by at least some of these pulsars, such as Vela, for example.Comment: 6 pages and 4 figure