1,721,130 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
Calculation of linelists for Chromium Hydride (CrH) & Manganese Hydride (MnH)
Full text linkNew linelists (list of wavelengths with associated frequencies) for the open-shell transition metal diatomics Chromium Hydride (CrH) and Manganese Hydride (MnH) have been calculated. These linelists have been calculated from first principles making use of the Born-Oppenheimer approximation which decomposes the Schr\"{o}dinger equation for a molecule into an electronic equation and rovibronic equation. To solve the electronic Schr\"{o}dinger equation and thus produce Potential Energy Curves (PECs), Dipole Moment Curves (DMCs) and all relevant couplings (transition dipole, electronic angular momentum, spin-orbit) the MRCI (Multi-Reference Configuration Interaction) method as implemented in the \textit{ab initio} \texttt{MOLPRO} package was used. The electronic states considered were those up to cm as this region is of most importance to astronomers to whom we are creating the linelists for within the ExoMol project. The construction of linelists for transition metal diatomics is very much at a developmental stage due to the myriad of low-lying electronic states of high multiplicity which couple together. Hence during the calculation of \textit{ab initio} curves a systematic study of the CASSCF orbitals used for the proceeding MRCI calculations was undertaken for both CrH and MnH. Also the effect of changing the configuration space of electrons was found to have profound effects on the behaviour of the PECs obtained. Additionally, the variation in properties obtained by changing the number of states calculated within a single MRCI calculation was investigated. A choice selection of these \textit{ab initio} curves were then implemented into the in-house programme Duo to produce linelists for CrH and MnH. These linelists were refined using available experimental data. At present, the existing linelist available for CrH in literature has 2 electronic states. Our new linelist is composed from 8 low-lying electronic states of CrH. CrH is used to classify L type dwarfs under the widely accepted classification scheme of Kirkpatrick. Additionally it has been shown theoretically that CrH could be used as a sensitive probe of magnetic fields of stars and also in the so-called ``deuterium test'' to probe the evolutionary history of sub-stellar objects. Due to the limited coverage of the existing linelist, a new linelist is sought after by astronomers. At present MnH has not been discovered in outer space but due to the favourable abundance of manganese it has been speculated that it could be present in the ISM. Hence the creation of a linelist opens up the possibility of the first astronomical detection of this molecule. Since January 2016 I have been working as a teaching fellow at Aberystwyth University. Hence preliminary work has been done on creating projects for undergraduate students for the molecules of BeH, MgH and CaH. A summary of literature has also been created for FeH with a view to in future creating a new linelist for this molecule which is of considerable interest both from an astronomical and theoretical perspective
A linelist for the hydrogen sulphide molecule
Full text linkThe main aim of this study is to calculate a high temperature line list for H_2^32S. The results will form an important addition to the databases used for space applications, as well as laboratory investigations and pollution studies. The Dvr3d program suite is used to calculate the bound ro-vibrational energy levels, and dipole moment transition intensities. The most accurate available potential energy surface is empirically determined. This surface is used in our calculations after refining it by fitting to the up-to-date experimental data. For accurate line intensities, an accurate dipole moment surface (DMS) is needed. Constructing an accurate DMS for H_2S is well known to be difficult. A systematic ab initio study for the DMS has been performed. Different methods were tested in conjunctions with different basis sets taking into account the relativistic corrections and core-valence effects. The resulting (ATY2013) line list should be valid from 0 to 9000 cm^−1 and for temperature up to 2000 K. ATY2013 with cut off intensity of order 10^−31 cm^−1/(molecule×cm^−2) contains ∼36×10^6 transitions at 2000 K. In addition, the pure rotational transition frequencies of H_2S in natural abundance in its ground and first excited vibrational states have been recorded at room temperature at 0.005 cm^−1 resolution in the region 45 to 360 cm^−1 with a globar continuum source at SOLEIL synchrotron. 2400 rotational transitions are assigned to ground vibrational state of the four isotopologues H_2^32S, H_2^33S, H_2^34S and H_2^36S where 65% of them are new. 91 rotational transitions of H_2^36S were identified for the first time, as well as 406 rotational lines of H_2^32S and H_2^34S in their first excited bending vibrational state were recorded and analysed for the first time
Variational calculations of rotation-vibration spectra for small molecules of astrophysical interest
Full text linkVariational calculations of rotation-vibration spectra are presented for a range of four- and five-atom molecules of atmospheric and astrophysical importance. Using state-of-the-art electronic structure methods, new nine-dimensional potential energy and dipole moment surfaces are constructed for methyl chloride (CH3Cl), silane (SiH4), and methane (CH4). The respective surfaces are rigorously evaluated against high-resolution spectroscopic data from a variety of experimental sources. The ab initio potential energy surfaces represent some of the most accurate to date, whilst intensity simulations utilizing the dipole moment surfaces show good agreement with experiment. A novel application of rotation-vibration computations is introduced to investigate the sensitivity of spectral lines to a possible space-time variation of the proton-to-electron mass ratio μ. The approach relies on finding the mass dependence of the computed energy levels and is only possible because of the remarkable accuracy of variational calculations. Highly sensitive transitions are uncovered for ammonia (NH3) and the hydronium cation (H3O+) which could lead to a tighter constraint on a varying μ. An advantage of the variational approach is that Einstein A coefficients can be determined to help guide future laboratory and astronomical observations. This thesis demonstrates the current capabilities of variational calculations of rotation-vibration spectra and highlights the challenges faced by the field
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
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe 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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe 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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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