Photoinduced Energy Transfer in Linear Guest-Host Chromophores: A Computational Study.

Polymer-based guest-host systems represent a promising class of materials for efficient light-emitting diodes. The energy transfer from the polymer host to the guest is the key process in light generation. Therefore, microscopic descriptions of the different mechanisms involved in the energy transfer can contribute to enlighten the basis of the highly efficient light harvesting observed in this kind of materials. Herein, the nature of intramolecular energy transfer in a dye-end-capped conjugated polymer is explored by using atomistic nonadiabatic excited-state molecular dynamics. Linear perylene end-capped (PEC) polyindenofluorenes (PIF), consisting of n (n = 2, 4, and 6) repeat units, i.e., PEC-PIFn oligomers, are considered as model systems. After photoexcitation at the oligomer absorption maximum, an initial exciton becomes self-trapped on one of the monomer units (donors). Thereafter, an efficient ultrafast through-space energy transfer from this unit to the perylene acceptor takes place. We observe that this energy transfer occurs equally well from any monomer unit on the chain. Effective specific vibronic couplings between each monomer and the acceptor are identified. These oligomer → end-cap energy transfer steps do not match with the rates predicted by Förster-type energy transfer. The through-space and through-bond mechanisms are two distinct channels of energy transfer. The former dominates the overall process, whereas the through-bond energy transfer between indenofluorene monomer units along the oligomer backbone only makes a minor contribution.

Vibrational energy redistribution during donor-acceptor electronic energy transfer: criteria to identify subsets of active normal modes.

Photoinduced electronic energy transfer in conjugated donor-acceptor systems is naturally accompanied by intramolecular vibrational energy redistributions accepting an excess of electronic energy. Herein, we simulate these processes in a covalently linked donor-acceptor molecular dyad system by using nonadiabatic excited state molecular dynamics simulations. We analyze different complementary criteria to systematically identify the subset of vibrational normal modes that actively participate on the donor → acceptor (S2→ S1) electronic relaxation. We analyze energy transfer coordinates in terms of state-specific normal modes defined according to the different potential energy surfaces (PESs) involved. On one hand, we identify those vibrations that contribute the most to the direction of the main driving force on the nuclei during electronic transitions, represented by the non-adiabatic derivative coupling vector between donor and acceptor electronic states. On the other hand, we monitor normal mode transient accumulations of excess energy and their intramolecular energy redistribution fluxes. We observe that the subset of active modes varies according to the PES on which they belong and these modes experience the most significant rearrangements and mixing. Whereas the nuclear motions that promote donor → acceptor energy funneling can be localized mainly on one or two normal modes of the S2 state, they become spread out across multiple normal modes of the S1 state following the energy transfer event.

Bienestar psicológico y ansiedad rasgo-estado en miembros de parejas con infertilidad primaria / Psychological wellbeing and trait-state anxiety in members of couples with primary infertility

Introducción: el problema de la infertilidad cobra mayor dimensión y trascendencia, a nivel mundial, siendo cada vez más evidentes las complejas relaciones existentes entre los factores psicológicos y la fertilidad. Objetivo: caracterizar la relación del bienestar psicológico con los niveles de ansiedad rasgo- estado en los miembros de las parejas infértiles que asistieron al Centro de Reproducción Asistida de Baja Tecnología de la provincia Mayabeque; en el periodo de noviembre del 2016- abril del 2017. Métodos: se realizó un estudio descriptivo, correlacional y transversal. La muestra quedó conformada por 80 miembros de parejas con infertilidad primaria, seleccionándose por criterios. Para la recogida de la información se aplicó el CAVIAR y el IDARE. En el procesamiento estadístico se utilizó la dócima X2 y la dócima de Duncan.Resultados: preponderó el nivel moderado de bienestar psicológico en el 75por ciento de la muestra; el nivel alto de ansiedad de estado en 92,5 por ciento de los hombres y el 95 por ciento de las mujeres, el nivel alto de ansiedad como rasgo en 52,5 por ciento de los hombres y el 65 por ciento en mujeres. El 92.5 por ciento en hombres y el 95por ciento de las féminas presentaron niveles alto de ansiedad de estado y bienestar psicológico moderado; el 62.5 por ciento de las mujeres y 47.5 por ciento de los varones presentaron niveles altos de ansiedad como rasgo y bienestar psicológico moderado. Conclusiones: se evidenció una relación significativa entre el bienestar psicológico y la ansiedad como rasgo en los miembros de las parejas infértiles(AU)

Introduction: the problem of infertility has a high dimension and transcendence, worldwide, being the complex relations between psychological factors and infertility more evident every time. Objective: to characterize the relation of the psychological wellbeing with the levels of trait-state anxiety in members of infertile couples who attended the Assisted Reproduction Center of Low technology in Mayabeque province; from November, 2016 to April, 2017. Methods: a descriptive, correlational and transversal study was performed in the Assisted Reproduction Center of Low technology in Mayabeque province. The sample was formed by 80membersof couples with primary infertility, selected by criteria. For collecting the information CAVIAR and IDARE were applied. In the statistical processing, X2 and dócima Duncan were used as a feature in members of infertile couples.Results: moderate level of psychological wellbeing prevailed with a 75 percent of the sample; the high level of state-anxiety in a 92,5 per cent of men and in a 95 percent of women, the high level of men and the 95 percent of females presented high levels state-anxiety moderate psychological wellbeing; the 62.5 per cent of women and the 47.5 percent of males presented high levels of trait-anxiety and moderate psychological wellbeing. Conclusions: a significant relation between psychological wellbeing and anxiety as a feature in the members of infertile couples was evident (AU)