Interaction-induced chaos in a two-electron quantum-dot system

A quasi-one-dimensional quantum dot containing two interacting electrons is analyzed in search of signatures of chaos. The two-electron energy spectrum is obtained by diagonalization of the Hamiltonian including the exact Coulomb interaction. We find that the level-spacing fluctuations follow closely a Wigner-Dyson distribution, which indicates the emergence of quantum signatures of chaos due to the Coulomb interaction in an otherwise non-chaotic system. In general, the Poincar\'e maps of a classical analog of this quantum mechanical problem can exhibit a mixed classical dynamics. However, for the range of energies involved in the present system, the dynamics is strongly chaotic, aside from small regular regions. The system we study models a realistic semiconductor nanostructure, with electronic parameters typical of gallium arsenide.Comment: 4 pages, 3ps figure

Relacion de la comprension del discurso narrativo y memoria de trabajo en ninos escolares sin dificultades de lenguaje

73 p.Los niños sin dificultad en el lenguaje presentan características heterogéneas, tanto en la expresión como en la comprensión de esta, sin embargo, según distintos autores la capacidad de memoria influye en la comprensión del discurso. Existe gran controversia al momento de establecer si los sujetos escolares que no presentan dificultades de lenguaje tienen menor rendimiento en los aspectos cognitivos como en la memoria de trabajo. En este estudio se relaciona el desempeño en tareas de comprensión del discurso narrativo y tareas de memoria de trabajo en 20 niños escolares sin dificultades de lenguaje, que conformaron el grupo control, de7,0 y 7,11 años pertenecientes aprimero y segundo de enseñanza general básica, en un establecimiento de estrato socioeconómico bajo de la ciudad de Talca. Los sujetos no presentan dificultades auditivas, cognitivas, y de lenguaje, esto ultimo según la Prueba de Desarrollo Inicial de Lenguaje (PDIL). Luego de realizar la investigación y analizar los datos no se encontró diferencia significativa con lo que se determina que no existe relación entre ambas variables

Entrepreneurship: cause and consequence of financial optimism

Extant evidence that the self-employed overestimate their returns by a greater margin than employees is consistent with two mutually inclusive possibilities. Self-employment may foster optimism or intrinsic optimists may be drawn to self-employment. Previous research is generally unable to disentangle these effects because of reliance on cross-sectional data. Using longitudinal data, this paper finds that employees who will be self-employed in the future overestimate their short-term financial wellbeing by more than those who never become self-employed. Optimism is higher still when self-employed. These results suggest that the greater optimism of the self-employed reflects both psychological disposition and environmental factors. By providing greater scope for optimism, self-employment entices the intrinsically optimistic

Multi-filter transit observations of WASP-39b and WASP-43b with three San Pedro M\'artir telescopes

Three optical telescopes located at the San Pedro M\'artir National Observatory were used for the first time to obtain multi-filter defocused photometry of the transiting extrasolar planets WASP-39b and WASP-43b. We observed WASP-39b with the 2.12m telescope in the U filter for the first time, and additional observations were carried out in the R and I filters using the 0.84m telescope. WASP-43b was observed in VRI with the same instrument, and in the i filter with the robotic 1.50m telescope. We reduced the data using different pipelines and performed aperture photometry with the help of custom routines, in order to obtain the light curves. The fit of the light curves (1.5--2.5mmag rms), and of the period analysis, allowed a revision of the orbital and physical parameters, revealing for WASP-39b a period ($4.0552947 \pm 9.65 \times 10^{-7}$ days) which is $3.084 \pm 0.774$ seconds larger than previously reported. Moreover, we find for WASP-43b a planet/star radius ($0.1738 \pm 0.0033$) which is $0.01637 \pm 0.00371$ larger in the i filter with respect to previous works, and that should be confirmed with additional observations. Finally, we confirm no evidence of constant period variations in WASP-43b.Comment: 13 pages, 7 figures, accepted in PASP, scheduled for the February 1, 2015 issu

Therapeutic Hypothermia: Critical Review of the Molecular Mechanisms of Action

Therapeutic hypothermia (TH) is nowadays one of the most important methods of neuroprotection. The events that occur after an episode of ischemia are multiple and hypothermia can affect the various steps of this cascade. The mechanisms of action of TH are varied and the possible explanation for the benefits of this therapy is probably the multiple mechanisms of action blocking the cascade of ischemia on many levels. TH can affect many metabolic pathways, reactions of inflammation, apoptosis processes, and promote neuronal integrity. To know the mechanisms of action of TH will allow a better understanding about the indications for this therapy and the possibility of searching for other therapies when used in conjunction with hypothermia will provide a therapeutic synergistic effect