1,721,030 research outputs found
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
Variations 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
Laser Spectroscopy of 1,2,3,4-Tetrahydro-1-naphthol·ROH (R=H, CH3) Clusters
No full textWavelength and mass selected resonant enhanced multi-photon ionization (REMPI) spectroscopy is an excellent tool for characterizing mol. clusters. Mass selected resonant two photon ionization (R2PI) spectra of the S1 S0 transition of 1,2,3,4-tetrahydro-1-naphthol (TR) and their complexes with solvent mols. such as water (W) and methanol (MeOH) have been recorded after a supersonic mol. beam expansion. Spectra have been analyzed with the aid of ab initio MO calcns. conducted at the B3LYP/6-31G** level of the theory
Laser Production of Metal Clusters in Supersonic Beam and Studies of their Reactivity towards Biological and Inorganic Systems
No full textThe study of neutral and ionized clusters has developed rapidly due to the unique capability of this state of matter to bridge the gap between isolated gas and condensed phase. Recently, a considerable interest was developed in prodn. of metal atoms pure and complexed with different systems to study the formation of nanostructures. The results of spectroscopic studies of clusters of metals with l-amino acids are here reported. The formation of stable L-tyrosine-Al cluster in a supersonic beam expansion of a laser ablated L-tyrosine and Al target was obsd
Chiral Discrimination of 2.3-Butanediols by Laser Spectroscopy
No full textThe resonance enhanced two-photon ionization time-of-flight (R2PI-TOF) excitation spectra of supersonically expanded complexes of isomeric 2,3-butanediols with a suitable chromophore, i.e. R-(+)-1-phenyl-1-propanol, represent powerful means for structurally discriminating the diol moiety and for investigating the nature of the intra- and intermol. interactions involved in the complexes
Laser R2PI spectroscopic and mass spectrometric studies of chiral neurotransmitters
No full textOne color, mass selected resonant two-photon ionization (IcR2PI) spectra of supersonically expanded bare neurotransmitter, (I S,2S)-(+)-N-methyl pseudoephedrine (MPE), and its complexes with chiral and achiral molecules have been investigated. The excitation spectrum of bare MPE has been analyzed and discussed on the basis of theoretical predictions at the B3LYP/6-31G** level of theory. The results allowed to get information on the possible conformers of MPE molecule and on the intermolecular forces on its cluster formed with a variety of solvent molecules, including chiral alcohols, lactates and water. Further information on intermolecular interactions have been obtained with ESI-CID-MS2 technique, applied to chiral biomolecules linked through a metal ion to the neurotransmitter. The experimental results are compared with theoretical predictions. (c) 2007 Elsevier B.V. All rights reserved
Monosolvation effects in chiral fluoroorganic compounds: a R2PI study
No full textWavelength- and mass-selected resonant-enhanced two-photon ionization (R2PI) spectra of supersonically expanded (R)-1-phenyl-2,2,2-trifluoroethanol (FER) and its complexes with water, R- and S-2-aminobutane (AR/S) and R- and S-2-butanol (BR/S) are reported and discussed in the light of ab initio calcns. The effects of the fluorine atoms in these systems have been evaluated by comparing the results with the vibronic and mass spectra of their nonfluorinated analogs, i.e. adducts with (R)-phenyl-1-ethanol (ER)
Mass Resolved Laser Spectroscopy of Microsolvated R-(+)-1-Phenyl-1-propanol: A Chiral Molecule of Biological Interest.
No full textThe effects of micro-solvation on the radical cation of R-(+)-1-phenyl-1-propanol, have been investigated. The energy thresholds of the homolytic C.alpha.-C.beta. bond breaking of R-(+)-1-phenyl-1-propanol radical cation, its mono-hydrated cluster, and its clusters with (2R,3R)-(-)-2,3-butanediol and (2S,3S)-(+)-2,3-butanediol have been studied by two color resonant two photon ionization and photodissocn. The barrier of the C.alpha.-C.beta. fragmentation is appreciably higher for the unsolvated mol. ion than for its adducts with solvent mols. Marked differences in the Et loss fragmentation energy are obsd. for clusters with water and with the two diols. In particular, the homochiral cluster with (2R,3R)-(-)-2,3-butanediol exhibits a fragmentation barrier higher than that of the corresponding heterochiral adduct with (2S,3S)-(+)-2,3-butanediol. At variance with the water adduct, the fragmentation of the covalent C.alpha.-C.beta. bond in the diol-clusters is energetically preferred to the loss of solvent
Chiral Aggregates of Indan-1-ol with Secondary Alcohols and Water: Laser Spectroscopy in Supersonic Beams
No full textOne color, mass selected resonant two-photon ionization (1cR2PI) spectra of supersonically expanded bare (R)-(-)indan-1-ol (IR) and its complexes with chiral and achiral mols. (solvent) have been investigated. The excitation spectrum of bare IR has been analyzed and discussed on the basis of theor. predictions at the B3LYP/6-31G** level of theory. The excitation spectra of its diastereomeric complexes with (R)-(-)-and (S)-(+)hexan-2-ol (XR or XS, resp.) and water (W) are characterized by significant shifts of their S0 S1 band origin relative to that of bare IR. The extent and the direction of these shifts are found to depend upon the structure and the configuration of solvent and are attributed to different short-range interactions in the ground and excited [IRsolvent] complexes. In particular the [IRW]n complexes display band origins blue-shifted relative to that of bare IR, attributed to the presence of an O-H.pi. electrostatic interaction between IR and W in [IRW]n. The [IRXR] and [IRXS] equil. structures have been calcd. by a mol. dynamical (MM3) sampling and PM3 semiempirical local optimization
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