1,720,972 research outputs found
2,2,3,3,3-Pentafluoro-1-propanol and its dimer: structural diversity, conformational conversion, and tunnelling motion
No full textRotational spectra of 2,2,3,3,3-pentafluoro-1-propanol (PFP) were measured using cavity and chirped pulse Fourier transform microwave spectrometers. Of the nine possible PFP configurations which include four mirror-imaged pairs and an achiral conformer, the two most stable monomeric PFP imaged pairs, i.e., PFPG+g+/G−g− and PFPTg+/Tg− were observed and assigned, along with the 13C, 18O and deuterated isotopologues of PFPG+g+/G−g−. The rotational transitions of PFPTg+/Tg− exhibit large tunnelling splittings and were analyzed in detail. CREST, a recently developed conformational search tool that was used for systematic conformational searches of possible binary PFP conformers and the subsequent DFT calculations at the B3LYP-D3(BJ)/def2-QZVP level produced nearly 80 stable, binary PFP geometries, where ten of them are within a narrow energy window of ∼1 kJ mol−1, highlighting the structural diversity of the system. Rotational spectra of five (PFP)2 conformers were assigned and were identified as the five most stable binary conformers predicted. A closer examination reveals that the assigned binary conformers are made exclusively of the two most stable PFP monomeric subunits observed experimentally. A combined kinetic and thermodynamic model was proposed to explain the observation or non-observation of low energy conformers, and the analysis was further verified by the ‘argon test’. The non-covalent intermolecular interactions of PFP and its binary conformers are also discussed with the aid of quantum theory of atoms in molecules (QTAIM) and non-covalent interaction (NCI) analyses, as well as the effects of fluorination by comparing with 1-propanol and its dimers.This work was funded by the Natural Sciences and Engineering Research Council of Canada and the University of Alberta. A. I. acknowledge the support of a H. E. Gunning Research Fellowship, and a research award through the Mobility Program: Egonlabur 2020–2021, the University of the Basque Country UPV/EHU and a predoctoral fellowship from the Basque Government, Spain, respectively. S. O. thanks the Fonds der Chemischen Industrie for financial support.Peer reviewe
Higher-Energy Hexafluoroisopropanol···Water Isomer and Its Large Amplitude Motions: Rotational Spectra and DFT Calculations
No full textRotational Spectroscopy of the 2,2,3,3,3‐Pentafluoropropanol⋅⋅⋅Water Complex: Conformations and Large Amplitude Motions
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Rotational Spectrum and Molecular Structures of the Binary Aggregates of 1,1,1,3,3,3-Hexafluoro-2-propanol with Ne and Ar
No full textGoing 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
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
Rotational and vibrational spectroscopy of a weakly bound hexafluoroisopropanol⋯dinitrogen complex: 14 N hyperfine splittings, molecular geometry, and experimental benchmarks
No full textStructure and internal dynamics of hexafluoroisopropanol⋯N 2 were uncovered by rotational spectroscopy, aided by spin statistics analyses and ab initio calculations. The data from rotational and vibrational spectra serve as benchmarks for theory.The rotational spectrum of a weakly bound binary complex of hexafluoroisopropanol (HFIP) with molecular nitrogen was measured using chirped-pulse and cavity-based Fourier transform microwave spectrometers. In addition, its infrared spectrum was measured in the OH stretching region. An extensive conformational search identified multiple binding sites on HFIP, with the global minimum structure featuring a trans -HFIP conformation and nitrogen weakly bound at the acidic proton (H t N H ). Good agreement between the experimentally determined rotational constants and the relative intensity patterns of a -, b -, and c -type transitions with theoretical predictions conclusively identified the H t N H conformer. This assignment is further corroborated by an analysis of the 14 N nuclear quadrupole hyperfine structure. The non-equivalence of the two 14 N nuclei in H t N H is confirmed through a detailed molecular symmetry group analysis, as well as the 14 N nuclear quadrupole hyperfine analysis. Examination of the experimental nuclear quadrupole coupling constants offers additional insights into the orientation and large-amplitude vibrational motions of the N 2 subunit. Furthermore, the experimentally derived rotational constants and the OH stretching band position of the complex, compared with previously known values for the isolated monomer, serve as complementary benchmarks for evaluating the systematic quality of predictions from electronic structure calculations across several levels of theory. This combined examination of vibrational energy levels and structural parameters aids in distinguishing fortuitously accurate predictions of individual properties.Structure and internal dynamics of hexafluoroisopropanol⋯N 2 were uncovered by rotational spectroscopy, aided by spin statistics analyses and ab initio calculations. The data from rotational and vibrational spectra serve as benchmarks for theory.The rotational spectrum of a weakly bound binary complex of hexafluoroisopropanol (HFIP) with molecular nitrogen was measured using chirped-pulse and cavity-based Fourier transform microwave spectrometers. In addition, its infrared spectrum was measured in the OH stretching region. An extensive conformational search identified multiple binding sites on HFIP, with the global minimum structure featuring a trans -HFIP conformation and nitrogen weakly bound at the acidic proton (H t N H ). Good agreement between the experimentally determined rotational constants and the relative intensity patterns of a -, b -, and c -type transitions with theoretical predictions conclusively identified the H t N H conformer. This assignment is further corroborated by an analysis of the 14 N nuclear quadrupole hyperfine structure. The non-equivalence of the two 14 N nuclei in H t N H is confirmed through a detailed molecular symmetry group analysis, as well as the 14 N nuclear quadrupole hyperfine analysis. Examination of the experimental nuclear quadrupole coupling constants offers additional insights into the orientation and large-amplitude vibrational motions of the N 2 subunit. Furthermore, the experimentally derived rotational constants and the OH stretching band position of the complex, compared with previously known values for the isolated monomer, serve as complementary benchmarks for evaluating the systematic quality of predictions from electronic structure calculations across several levels of theory. This combined examination of vibrational energy levels and structural parameters aids in distinguishing fortuitously accurate predictions of individual properties.Natural Sciences and Engineering Research Council of Canada https://doi.org/10.13039/501100000038University of Alberta https://doi.org/10.13039/501100000190Canada Research Chairs https://doi.org/10.13039/501100001804Fonds der Chemischen Industrie https://doi.org/10.13039/10001899
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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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