1,721,138 research outputs found
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Line Lists For High Resolution Studies Of Exoplanets
Get PDFThe ExoMol project (www.exomol.com) provides comprehensive line lists
for the study of exoplanets and other hot bodies. As part of the ERC-funded ExoMolHD project these line lists are being refactored to facilitate their use in characterization of exoplanets using high resolution Doppler shift spectroscopy. This technique is based the use of MARVEL (measured active rotation vibration energy level) to obtain empirical energy levels and illustrated by a recent study on formaldhyde (HCO).\footnote{A. R. {Al-Derzi}, S. N. Yurchenko, J. Tennyson, M. Melosso, Ningjing Jiang, C. Puzzarini, L. Dore, T. Furtenbacher, R. Tobias and A G. Cs\'asz\'ar, 2021, J. Quant. Spectrosc. Radiat. Transf.,
doi = {10.1016/j.jqsrt.2021.107563}}
For formaldehyde we analysed of 16\,596 non-redundant transitions from 43 experimental sources and resulted in the determination of 5029 empirical energy levels. As part of this work new measurements were performed in Bologna yielding high-accuracy rotational transitions
within the ground, \nub{3}, \nub{4} and \nub{6} vibrational states,
significantly improving the overall accuracy of the network. Eleven
artificial transitions determined from effective Hamiltonian fits were added to the network to both fix the gap between ortho and para levels, and to join free-standing networks of transitions to the main network.
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The empirical energies were used to update the AYTY ExoMol line list for formaldehyde. This yielded 367\,779 transition frequencies determined
using the empirical energy levels of which
183\,673 lie above the dynamic HITRAN intensity cutoff, see the example in the figure.
The generation of line lists which combine empirically-determined transition wavenumbers with {\it ab initio} transition dipoles is suitable for high resolution
studies of both the Earth's and exoplanetary atmospheres.
High resoltion line lists for other molecules starting with AlO, VO and the isotopologues of H are currently being prepared.Made available in DSpace on 2021-09-24T21:09:07Z (GMT). No. of bitstreams: 2
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5317.pdf: 137247 bytes, checksum: 8ac64098fec06cbe0aba9d5ed7dddd98 (MD5)
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Previous issue date: 2021-06-2
The Electric Quadrupole Spectra Of Diatomic Molecules
Get PDFOwing to their molecular symmetry, many transitions of homonuclear diatomic molecules are forbidden in the electric dipole approximation. Instead their spectra are dominated by higher order transition moments, including the magnetic dipole moment and electric quadrupole moment.
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Here we present a new implementation of electric quadrupole transition moments in \textsc{Duo}\footnote{S.~N. Yurchenko, L.~Lodi, J.~Tennyson, A.~V. Stolyarov, \emph{Comput. Phys. Commun.}, 2016, \textbf{202}, 262 -- 275; publicly available at \textit{https://github.com/Trovemaster/Duo}.}. The implementation is validated against the highly accurate linelist of Roueff et al. \footnote{The full infrared spectrum of molecular hydrogen, Astron. Astrophys, 630 (2019)} for rovibrational transitions of the hydrogen molecule.
We also perform ab initio calculations for potential energy curves (PECs), electric quadrupole moment curves (EQCs), and spin-orbit coupling curves (SOCs) and demonstrate rovibronic linestrength calculations for the three lowest lying states (, and ) of molecular oxygen. Further demonstrations are provided for various other molecules of interest, including CO and HF as part of the ExoMol project \footnote{J.~Tennyson et al. \emph{J. Quant. Spectrosc. Radiat. Transf.}, 2020, \textbf{255}, 107228; \textit{www.exomol.com}.}. Absorption cross-sections are calculated using the \textsc{ExoCross} program\footnote{S.~N. {Yurchenko}, A.~F. {Al-Refaie}, J.~{Tennyson}, \emph{Astron. Astrophys};,
2018, \textbf{614}, A131; publicly available at \textit{https://github.com/Trovemaster/ExoCross}.}.Made available in DSpace on 2021-09-24T21:09:46Z (GMT). No. of bitstreams: 2
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Previous issue date: 2021-06-2
A Theoretical Ro-vibrational Line List Of H2cs Using A New Approach To Construct The Exact Kinetic Energy Operator
Get PDFA procedure to generate the exact kinetic energy operator in valence coordinates, based on S{\o}rensen's method for constructing non-rigid Hamiltonians, is presented. This method is currently being applied to the thioformaldehyde (HCS) molecule, where the TROVE program is used to compute ro-vibrational energy levels and transition intensities. Moreover, the \textit{ab initio} PES is refined with the MARVEL approach. The exact kinetic energy operator itself is produced using the symbolic computation program \textit{Mathematica} and acts as TROVE input.Made available in DSpace on 2021-09-24T21:09:59Z (GMT). No. of bitstreams: 2
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Previous issue date: 2021-06-2
A variationally computed T=300 K line list for the methyl radical CH3
Get PDFMade available in DSpace on 2019-07-15T22:17:04Z (GMT). No. of bitstreams: 2
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Previous issue date: 2019-06-21Made available in DSpace on 2020-01-25T19:30:52Z (GMT). No. of bitstreams: 4
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Previous issue date: 2019-06-21We present the first variational calculation of a room temperature \textit{ab initio} line list for
the CH radical. It is based on a high level {\it ab initio} potential energy surface and dipole
moment surface of CH in the ground electronic state. The ro-vibrational energy levels and Einstein
coefficients were calculated using the general-molecule variational approach implemented in the computer program
TROVE. Vibrational energies and vibrational intensities are found to be in very good agreement with
the available experimental data
Variations on the Author
Get PDF“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
Get PDFWe 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
Exomolhd: Photodissociation Of Diatomic Molecules
Get PDF\begin{wrapfigure}{r}{0pt}
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The destruction of molecules by photodissociation influences the composition and dynamics of exoplanets, particularly in the presence of a UV-rich stellar environments, where molecules are hot. Current photodissociation calculations generally assume K,
appropriate for the cold interstellar medium but inadequate for hot (exo)planets and stars.
We compute temperature-dependent photodissociation cross sections for molecules found in these atmospheres. The cross sections are calculated by solving the nuclear-motion Schrödinger equation as part of the ExoMol project using codes Duo and Exocross\footnote{Yurchenko \textit{et al} Comput Phys Commun 2016 \textbf{202} 262–275;Yurchenko \textit{et al} A\&A 2018 \textbf{614} A131 }, and averaging results obtained as discrete spectra.
We benchmark our results for three systems. The general validity of the methodology is tested considering the A X transition of HCl at low . Our cross sections and rates agree with published results\footnote{Dishoeck \textit{et al} J. Chem. Phys. 1982 \textbf{77} 3693} (2.31*10 s versus 2.10*10 s respectively ). We also reproduce calculated photodissociation cross section of BeH at T=1800 K.\footnote{Yang \textit{et al} J Quant Spectrosc Radiat Transf 2020 \textbf{254} 107203} We performed the simulations considering the three excited states, A, B and C, see figure. The photodissociation spectrum of NaCl varies consistently with : at K, there two peaks at 240 nm and 260 nm; while at K the peaks merge.Made available in DSpace on 2021-09-24T21:09:20Z (GMT). No. of bitstreams: 2
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Previous issue date: 2021-06-2
Non-resonant Raman spectra of the methyl radical 12CH3 simulated in variational calculations
Get PDFMade available in DSpace on 2019-07-15T22:17:04Z (GMT). No. of bitstreams: 2
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Previous issue date: 2019-06-21Made available in DSpace on 2020-01-25T19:30:52Z (GMT). No. of bitstreams: 4
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Previous issue date: 2019-06-21We report first-principles variational simulation of the non-resonant Raman spectrum for methyl radical (CH) in the electronic ground state. Calculations are based on a high level \emph{ab initio} potential energy and polarizability tensor surfaces of CH and employ accurate variational treatment of the ro-vibrational dynamics implemented in the general code TROVE [S. N. Yurchenko, W. Thiel, and P. Jensen, {\it J. Mol. Spectrosc.} {\bf 245}, 126--140 (2007); A. Yachmenev and S. N. Yurchenko, {\it J. Chem. Phys.} {\bf 143}, 014105 (2015)]. We extend the capabilities of TROVE towards simulations of the Raman spectra, which can in be applied to arbitrary molecule of moderate size. The simulations for CH are found to be in a good agreement with the available experimental data
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