Experimental observation of a complex periodic window

The existence of a special periodic window in the two-dimensional parameter space of an experimental Chua's circuit is reported. One of the main reasons that makes such a window special is that the observation of one implies that other similar periodic windows must exist for other parameter values. However, such a window has never been experimentally observed, since its size in parameter space decreases exponentially with the period of the periodic attractor. This property imposes clear limitations for its experimental detection.Comment: 4.2 pages, 4 figure

Characterization in bi-parameter space of a non-ideal oscillator

The authors thank scientific agencies CAPES, CNPq (112952/2015-1), and FAPESP (2011/ 19269-11). M. S. Baptista also thanks EPSRC (EP/I03 2606/1).Peer reviewedPostprin

Resilient, Mindful, and Satisfied Educational Professionals

This study conducted confirmatory factor analysis (CFA) and exploratory factor analysis (EFA) using both the Connor-Davidson Resilience Scale (CD-RISC 25) and the Mindfulness Attention Awareness Scale (MAAS) to create a validated, synergistic, higher-order factor we call Invicti Anima based on the responses 630 teachers and building-based educational leaders in three northeastern USA states. Controlling for important contextual variables including educator sense of agency, our structural equation path model mapped the relationships between educator role, level of Invicti Anima, and Job Satisfaction, as measured by the Job Satisfaction Index (JSI). The educators in our study who were strong in Invicti Anima exhibited characteristics of both resiliency and mindfulness, and were significantly and substantially more satisfied on their jobs, even net of their sense of control (agency) in their schools. Our findings have important implications for the professional development of educators in dealing with stress, longevity in their positions, and positive outcomes for the students and others under their direction

First principle theory of correlated transport through nano-junctions

We report the inclusion of electron-electron correlation in the calculation of transport properties within an ab initio scheme. A key step is the reformulation of Landauer's approach in terms of an effective transmittance for the interacting electron system. We apply this framework to analyze the effect of short range interactions on Pt atomic wires and discuss the coherent and incoherent correction to the mean-field approach.Comment: 5 pages, 3 figure

Surface nano-patterning through styrene adsorption on Si(100)

We present an ab initio study of the structural and electronic properties of styrene molecules adsorbed on the dimerized Si(100) surface at different coverages, ranging from the single-molecule to the full monolayer. The adsorption mechanism primarily involves the vinyl group via a [2+2] cycloaddition process that leads to the formation of covalent Si-C bonds and a local surface derelaxation, while it leaves the phenyl group almost unperturbed. The investigation of the functionalized surface as a function of the coverage (e.g. 0.5 -- 1 ML) and of the substrate reconstruction reveals two major effects. The first results from Si dimer-vinyl interaction and concerns the controlled variation of the energy bandgap of the interface. The second is associated to phenyl-phenyl interactions, which gives rise to a regular pattern of electronic wires at surface, stemming from the pi-pi coupling. These findings suggest a rationale for tailoring the surface nano-patterning of the surface, in a controlled way.Comment: 19 pages (preprint), 4 figures, supplementary materia

Economics and social psychology on public goods: experiments and explorations

Economics and social psychology come from different traditions in social science, and in the past they seldom met. Their territories seemed to be well delimited. The former discipline’s mainstream focused on market mediated interactions, making sense of an asocial concept of action by referring it to “the ordinary business of life” (Marshall, 1920, I.II.1) where agent’s choices supposedly are independent from those of other parties in the transactions (Sugden, 2002); on the other hand, the second discipline descends from the more romantic view of man as a social being, and was stimulated by questions on why and how the immersion of individuals in the multitude, or the simple presence of others, appeared to transform behaviour. Lately, however, economics has started moving in a direction that reduces this gap. In a double but interrelated move, economics is adopting experimental methods familiar to those of social psychology, and is becoming more concerned with the relevance of rational choice in contexts where there is clear inter-individual dependence, raising questions to which social psychologists have already devoted considerable time and effort. As a part of this movement, social dilemmas, that is, “situations in which (a) individual group members can obtain higher outcomes (at least under some circumstances) if they pursue their individual interest while (b) the group obtains higher incomes if all group members further the group interest” (Dijk and Wilke, 1998: 110) have become the focus of shared interest of both economists and social psychologists. The motivation for the study of social dilemmas does not differ much in economics and social psychology and it arises out of two major types of challenges. The first (Fontaine, 2002) is related to the growing consciousness of the pervasiveness of market failures (combined with government failures) concerning issues of major social urgency like pollution and the use of scarce resources. The second, (Dawes, 1991) cropped up out of the finding that people both in real-life and experimental contexts fail to behave systematically in the way depicted by standard game theory, often opting for more benign strategies. Interest in social dilemmas is thus related, on the one hand, with the concern with problems that the market cannot solve, and, on the other, with understanding the reasons that may drive people to act in ways that are not in line with rational self-interest. For economics those questions are arcane questions 1 that were never ignored by the best minds in this discipline. Marshall’s sentence in epigraph is a clear instance of this concern. This essay does not intend to cover the whole scope of existing approaches to social dilemmas since it only deals with dilemma situations that somehow fit into the economist’s category of public good provision problems and with the experimental studies in economics and social psychology2. On the basis of an exploratory joint survey of experimental literature from both disciplines, it focuses on their differences in theoretical framing and their use of the experimental method. The following points will be argued: (a) Twenty five years of experimental research in both disciplines have produced an impressive accumulation of coherent results showing that in spite of the free-riding prediction, there is a tendency to voluntary contribution in “small” groups; (b) Notwithstanding the abundance of experimental studies, several interesting problems remain unexplored. In economics, the research focus has been on “are the game theoretical predictions corroborated by experimental evidence?”, whereas in social psychology it has been on “what may cause the voluntary disposition to contribute”. Questions pertaining to “what institutional contexts might hinder or foster voluntary contribution” still offer a vast domain of unexplored possibilities. (c) In spite of all efforts, the conceptual framework that may account for the contributive disposition in public good dilemma situations and help “discover how this latent social asset can be developed” remains rather sketchy