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Investigation of the ultra-fast structural changes in metal-organic complexes: comparison spectroscopy and time-resolved XRD
Full text linkOur aim is a detailed understanding of the ultrafast structrual dynamics and the underlying basic machanisms of molecular switches under optical excitation, which are still not fully understood in its variety. In order to monitor the occurring structural changes in molecules and alloys we are taking advantage of time-resolved x-ray diffraction measurements. but since the important electronic changes due to optical excitation take place on very short ps- and sub-ps timescales it gives rise to the necessity of faster time resolved measurements than those which are currently possible at third generation synchrotrons. Besides new attempts of directly monitoring the structural changes with shorter x-ray pulses by femtosecond FEL- an XPS-pump-probe experiments, we are currently gaining more insight in the structural dynamics by indirect measurements using our fs-time-resolved transient absorption spectroscopy. Therefore we will present our recent spectroscopic data of a metal-organic complex which will be related to certain structural changes, while the near future aim is to prove these by further x-ray experiments
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Ultrafast Dynamical Study of Pyrene- N,N -dimethylaniline (PyDMA) as an Organic Molecular Diode in Solid State
Full text linkFemtosecond optical pump probe spectroscopy has been employed for studying the directly linked electron donor acceptor system pyrene-N,N-dimethylaniline (PyDMA) in solid state. This DMA-pyrene derivative discussed is being applied as a molecular diode system switching on an ultrafast time scale. Our ultrafast solid-state studies reveal a complex photochemistry of this molecular crystal system. Strong couplings of the optically induced charge-transfer state with the radical ion pair state allow a femtosecond transition of the latter. One could see on the highest occupied molecular orbital lowest unoccupied molecular orbital (HOMO-LUMO) description that a pure optical transition switches the system from a conducting to a blocked system because the molecular orbitals (MOs) of DMA moiety lie in a node plane of the LUMO. Within 800 fs the system relaxes back to the ground state and/or forms a radical ion pair, which is the surprising result of our study; when the system was probed further, the system underwent vibrational cooling and enhanced population inversion of the radical ion pair
From Micromolecules’ to Macromolecules’ Structural Dynamics Properties: Ultrafast Chiroscopy with Synchrotron and Free Electron Laser Radiation
Full text linkVariations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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