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A Comparison Of The Methods Of Studying The Spectra Of The Ash2 Radical
No full textThe first studies of the A-B electronic band system of the AsH and AsD radicals were made at Sheffield University in the period from1966 to 1968 by Dixon, Duxbury and Lamberton using flash photolysis of arsine and deuterated arsine. The bands have a complex rotational structure associated with that of an asymmetric rotor. Band centres of the 0,v,0-0,0,0 progression were identified for v'=0 tp v'=5, although only the structure of the bands from v'=1 to 3 was analysed in detail. After a long time interval in 1986 a low resolution emission spectrum of AsH was recorded by NI et al. However, it was not until 2007 that He and Clouthier studied the electronic transition of jet-cooled AsH using laser induced fluorescence and wavelength-resolved emission. Following on from this in 2009 Zhao and colleagues recorded absorption spectra of the AsH radical by cavity ringdown spectroscopy. Finally in 2012 Grimminger and Clouthier recorded the equivalent transitions in AsD and AsHD. They also carried out ab initio calculations. By comparing the recent spectroscopic results with those of Dixon et al, we wish to show the complementarity of the different methods for understanding the behaviour of AsH and AsD radicals.Made available in DSpace on 2014-09-17T16:55:15Z (GMT). No. of bitstreams: 3
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Previous issue date: 2014-06-18Made available in DSpace on 2015-04-14T18:41:30Z (GMT). No. of bitstreams: 4
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Previous issue date: 2014-06-1
Effects Of Spin-orbit Coupling On The Spin-rotation Interaction In The Ash2 Radical
No full text"The occurence of predissociation in the electronic spectrum of AsH is very dependent upon the magnitude of the spin-orbit coupling parameter of the central atom. Making use of Table 5.6 in ""The Spectra and Dynamics of Diatomic Molecules, ELSEVIER"" by H. Lefebvre-Brion and R.W. Field, it is possible to appreciate the rapid rate of increase of the spin-orbit constants associated with the heavy central atom in the di-hydrides NH, PH and AsH. The spin-orbit constants range from 42.7 cm for NH, to 191.3 cm for PH,
and 1178 cm for AsH.
The effects of spin-orbit coupling may be seen in a plot of the separation of the central Q and Q sub-bands as the value of v' increases from 0 to 5. As the value of v' increases beyond 2 the spectrum becomes more and more fuzzy as the effects of predissociation become more obvious. This means that unlike the example of the behaviour of PH, where the vibronic level pattern can be followed below and above the barrier to linearity, in AsH and AsD the absorption spectrum becomes completely diffuse below the barrier to linearity in the A A state.
The change in the magnitude of the doublet splittings as v' increases may be seen in the plots of the doublet splittings showing the spin-uncoupling as a result of the increase of overall rotation. In the absorption spectrum of SbH, recorded in 1967 by T. Barrow in the Chemistry Department at Sheffield University, all the absorption features showed the effects of predissociation, consistent with a spin-orbit constant of 2834 cm for the central atom of SbH."Made available in DSpace on 2014-09-17T16:55:15Z (GMT). No. of bitstreams: 3
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Previous issue date: 2014-06-1
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
No full text“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
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Study of transport properties of CO2 and ethanol in a hydroalcoholic solution by classical molecular dynamics : application to Champagne wines.
No full textLes travaux présentés dans ce manuscrit sont consacrés à l'étude de la diffusion du dioxyde de carbone dissous et de l'éthanol dans une solution hydroalcoolique modèle représentant le champagne. La première partie de ce travail aborde les différents formalismes de la diffusion moléculaire, ainsi que les méthodes théoriques et expérimentales utilisées pour rendre compte de ce phénomène de transport. Une attention particulière est apportée à la dynamique moléculaire en champ de forces classiques qui est utilisé dans ce travail avec le logiciel GROMACS. Cette méthode théorique procure un point de vue novateur dans la recherche sur le champagne et plus particulièrement sur le rôle de chaque espèce majoritaire dans la diffusion du CO2. La spectroscopie RMN, ainsi qu'une méthode expérimentale basée sur l'étude du taux de grossissement des bulles, ont également été utilisées. Dans la deuxième partie, les résultats théoriques et expérimentaux sont présentés et comparés entre eux afin de valider le protocole des simulations de dynamique moléculaire. Les viscosités de la solution modèle et du champagne, ainsi que les rayons hydrodynamiques du CO2 et de l'éthanol sont également étudiés. La dernière partie du manuscrit concerne le partenariat avec l'entreprise Bull et l'étude des performances du logiciel GROMACS. L'expertise des équipes de Bull, ainsi que les outils développés par l'entreprise, permettent d'étudier le passage à l'échelle (ou "scalabilité") et le comportement parallèle de GROMACS pour la modélisation du champagne.The work presented in this manuscript is devoted to the study of the diffusion of dissolved carbon dioxide and ethanol in a hydroalcoholic solution model representing Champagne wines. The first part of this work deals with the different formalisms of molecular diffusion, as well as theoretical and experimental methods used to account for this phenomenon of transport. Particular attention is paid to the classical force field molecular dynamics that is used in this work with the GROMACS software. This theoretical approach provides a new perspective in research on champagne and particularly on the role of each of the main species in CO2 diffusion. NMR spectroscopy, and an experimental method based on the study of the bubbles growth rate, were also used. In the second part, the theoretical and experimental results are presented and compared with each other to validate the protocol of molecular dynamics simulations. The viscosities of the model solution and of the champagne, as well as the hydrodynamic radii of CO2 and ethanol, are also investigated. The last part of the manuscript focuses on the partnership with the Bull company and the study of the GROMACS software performance. The expertise of and the tools developed by the Bull company are used to study the scalability and the parallel behavior of GROMACS for modeling champagne
Description of vibrational states of ozone near the dissociation threshold
No full textLes énergies vibrationnelles de l’ozone des états proches de la limite de dissociation ont été calculées. Ces états concernent les étatsfaiblement liés en-dessous de la limite de dissociation O2 + O et les états métastables au-dessus de la limite de dissociation.Les coordonnées hypersphériques ont été utilisées pour représenter la dynamique vibrationnelle des atomes d’oxygène de l’ozone. Cescoordonnées hypersphériques permettent de représenter la symétrie du système par rapport à la permutation des noyaux et de tenir comptedes effets tunnels entre les trois puits C2V(M). L’énergie et la durée de vie des états métastables ont été calculées à l’aide de potentielsabsorbants complexes.Les énergies et les fonctions d’onde des états liés de l’isotopologue de l’ozone 16O3 avec un moment angulaire rotationnel J = 0 et 1 jusqu’auseuil de dissociation ont été calculées. Pour les niveaux liées, un bon accord avec les énergies expérimentales est trouvé : la déviation RMSentre les énergies vibrationnelles observées et celles calculées est de 1 cm −1. Les constantes rotationnelles ont été déterminées et utiliséespour une identification des modes vibrationnels des niveaux calculés. Les trois isotopologues 16O16O 16O, 16O16O18O et 16O18O16O ont étéconsidérés. Les propriétés de ces états ont été analysées. Les énergies, les largeurs et les fonctions d’onde des résonances vibrationnelles de16 O3sont déterminées pour des niveaux jusqu’à environ 3000 cm−1 au-dessus de la limite de dissociation. Les résonances prédissociées ont desdurées de vie entre 0,08 et 2 ps avec quelques niveaux de longue durée de vie. Ces états à longue durée de vie sont les niveaux hautementexcités dans les modes v1 et v2 de l’ozone.Les propriétés de symétrie des niveaux rovibrationnels permis de l’ozone (applicable à 16O3 et 18O3) aussi bien que les diagrammes decorrélation entre les états liés et les régions de dissociation ont été dérivées et discutées. Les diagrammes de corrélation ne sont pas triviauxparce que l’ozone se dissocie en (ou est formée de) l’atome d’oxygène dans l’état P et la molécule de O2 de symétrie 3 Σg−. Il est montré, pardes arguments de symétrie que les niveaux purement vibrationnels (J = 0) permis de 16O3 et de 18O3 , tous les deux faits de bosons à spinsnucléaires nuls, ne peuvent se dissocier sur la surface d’énergie potentielle fondamentale.Energies of vibrationallevelsof the ozone molecule near the dissociation threshold have been studied theoretically. Both, weakly bound -below the dissociation threshold O2 + O, and metastable levels – above the dissociation threshold, were considered.Hyperspherical coordinates were used to represent dynamics of oxygen atoms of the molecule. The hyperspherical coordinates allow us torepresent the symmetry of the system with respect to permutation of the three nuclei and take into account the tunneling between threeequivalent wells of the potential energy surface of O3. Energies and lifetimes (widths) of the metastable levels have been computed using themethod of the complex absorbing potential.Energies and wave functions of the bound levels of the symmetric ozone isotopologue 16O3 with rotational angular momentaJ = 0 and 1 up tothe dissociation threshold were calculated. For the bound levels, good agreement with experimental energies was found: the RMS deviationbetween observed vibrational energies and the present results is only 1 cm−1. Rotational constants were also computed and used for acharacterization of vibrational modes of the obtained levels. The three isotopologues 16O16O16O, 16O16O18O, and16O18O16O have beenconsidered. Properties of these states have been analyzed. Energies, widths ans wave functions of vibrational resonances of 16O3 have beendetermined for levels up to about 3000 cm−1 above the dissociation threshold. Predissociated resonances have lifetimes between 0.08 and 2 pswith a few levels of longer lifetimes. These long-lifetime levels are highly excited levels in the v1 and v2 modes of ozone
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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