1,720,992 research outputs found
Internal motions of the rare gas atom in dimethyl ether-krypton
No full textThe free jet millimeter-wave absorption spectra of two isotopomers of the weakly bonded dimethyl ether-Kr complex have been assigned and measured. The Kr atom lies in the óV symmetry plane of dimethyl ether perpendicular to the COC plane, at a r0-distance of 3.67 Å from its center of mass (cm). The line connecting the krypton atom to cm forms an r0-angle of 70° with the O-cm line. The observed conformation is in agreement with the global minimum as found with a distributed polarizability model. Many rotational transitions are split into two component lines, due to the motion of Kr relative to dimethyl ether in the complex. The corresponding splitting has been used to determine the barrier to the internal motion. Information on the dissociation energy has been deduced from the centrifugal distortion effects
Interactions between organic molecules and water. Rotational spectrum of the 1:1 oxetane-water complex
No full textThe 1:1 molecular complex between oxetane and water has been
investigated by using free-jet millimeter-wave spectroscopy. The rotational spectra of five isotopomers (with H2O, D2O, DOH, HOD and H218O) have been assigned. Partial r0 and rs structures
of the complex have been derived. The water moiety lies in the
plane of symmetry of oxetane, with the TMfree∫ hydrogen E with respect to the ring. The oxetane ring appears to be slightly nonplanar, with the Cb carbon tilted on the opposite side of the water unity. The three atoms involved in the hydrogen bond adopt a linear arrangement with an Oring¥¥¥H distance of about 1.86 ä, and the angle between the COC bisector and the Oring¥¥¥H
bond being ffi1068. Additionally, quantum-chemical calculations for the complex were performed and were found to be in agreement with the experimental results
Tunnelling Motion of HF Between the Two Oxygen Lone Pairs in the Dimethyl Ether-Hydrogen Fluoride Complex: A Pure Rotational Study
No full textThe rotational spectrum of the dimethyl ether ± hydrogen fluoride
complex was assigned by millimetre-wave free-jet absorption
spectroscopy. Fine details of the spectrum were resolved by FT
microwave molecular-beam spectroscopy. The HF group acts as a proton donor and tunnels at a rate of 44178.2(7) MHz between the
two oxygen lone pairs, which corresponds to an inversion barrier of
0.17(1) kcal mol1. The barrier to internal rotation of the two methyl groups is about 25% lower relative to the isolated ether
Rotational Spectrum and Internal Dynamics of Tetrahydrofuran–Krypton
No full textThe rotational spectrum of the tetrahydrofuran krypton van der Waals complex has been investigated by pulsed jet Fourier transform microwave spectroscopy. The spectra of the 84Kr and 86Kr isotopologues have been assigned. The krypton atom is located nearly over the oxygen atom, almost perpendicularly to the COC plane. Each rotational transition is split into two component lines due, according to the observed Coriolis coupling term between the tunnelling states, to the residual pseudorotational effects of the ring in the complex. The splitting between the two vibrational sublevels has been determined to be 87.462(2) and 87.062(2) MHz for the 84Kr and 86Kr isotopologues, respectively. These splittings have been used to determine the barrier to inversion, B2 = 67 cm-1. The dissociation energy has been estimated to be 3.7 kJ mol-1, from centrifugal distortion effects
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
Fourier transform microwave spectrum of pyridine–neon
No full textThe rotational spectra of normal, and various 15N, 13C and 22Ne species of pyridine-neon have been investigated by molecular beam Fourier transform microwave spectroscopy. The obtained results allowed for the experimental determination of the structure and of the 14N quadrupole coupling constants of the complex. The spectroscopic parameters are compared to those of other rare gases-pyridine complexes
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
- …
