1,721,407 research outputs found
Zhi shi chan quan an jian re dian wen ti yan jiu Zhishichanquan anjian redian wenti yanjiu / Feng Gang zhu
No full textRotational study of the bimolecule acetic acid-fluoroacetic acid
No full textThe rotational spectrum of the acetic acid-fluoroacetic acid bimolecule was measured by using a pulsed jet Fourier transform microwave spectrometer. One conformer, in which fluoroacetic acid is in trans form, has been observed. The rotational transitions are split into two component lines, due to the internal rotation of the methyl group of acetic acid. From these splittings, the corresponding V3 barrier has been determined. The dissociation energy of this complex has been estimated to 66 kJ/mol. An increase of the distance between the two monomers upon the OH → OD substitution (Ubbelohde effect) has been observed
Conformational equilibria and large-amplitude motions in dimers of carboxylic acids: rotational spectrum of acetic acid-difluoroacetic acid
No full textWe report the rotational spectra of two conformers of the acetic acid-difluoroacetic acid adduct (CH3COOH-CHF2COOH) and supply information on its internal dynamics. The two conformers differ from each other, depending on the trans or gauche orientation of the terminal -CHF2 group. Both conformers display splittings of the rotational transitions, due to the internal rotation of the methyl group of acetic acid. The corresponding barriers are determined to be V3(trans)=99.8(3) and V3(gauche)=90.5(9) cm(-1) (where V3 is the methyl rotation barrier height). The gauche form displays a further doubling of the rotational transitions, due to the tunneling motion of the -CHF2 group between its two equivalent conformations. The corresponding B2 barrier is estimated to be 108(2) cm(-1). The increase in the distance between the two monomers upon OH→OD deuteration (the Ubbelohde effect) is determined
The rotational spectrum of CF3Cl-Ar
No full textThe microwave spectrum of the van der Waals complex CF3Cl-Ar has been investigated by pulsed jet Fourier transform microwave spectroscopy. The observed spectra of the 35Cl and 37Cl isotopologues are typical of asymmetric tops, with rotational constants A, B, C = 3373.118(4), 988.2529(4), 879.5788(3) and 3286.66(4), 985.50(3), 871.359(8) MHz, respectively. The Ar atom is almost "L-shaped" with respect to the Cl-C bond, at a r0 distance of 3.824(2) Å from the center of mass (CM) of CF3Cl and with the angle Cl-CM-Ar = 81(2)°. The dissociation energy has been estimated to be 2.3 kJ mol-1
Unveiling the Conformations and van der Waals Interactions between Rare Gas and Bicyclic Aromatic: Rotational Spectroscopy of Benzofuran Complexes with Argon and Krypton
No full textBy integrating Fourier transform microwave spectroscopy with quantum chemical calculations, a detailed conformational and structural analysis of the benzofuran (BF) complexes with argon (BF–Ar) and krypton (BF–Kr) is conducted. The conformations of each complex are explored utilizing the Conformer-Rotamer Ensemble Sampling Tool method for conformational searches, with subsequent geometry optimizations using MP2, RI-SCS-MP2, and density functional theory methods. Experimental results corroborate that the most stable conformations for both complexes feature the rare gas (Rg) atom positioned above the BF ring. In particular, Ar and Kr atoms prefer to locate above the C5 atom, with the Rg···C5 line nearly perpendicular to the BF plane. The Ar and Kr atoms are located ≈3.491 and 3.580 Å from the center of mass of BF. The natural bond orbital analysis indicates that the second-order perturbation energy for the Rg···π interaction is about 3.1 and 3.0 kJ mol−1 in the BF–Ar and BF–Kr complexes, respectively. Symmetry-adapted perturbation theory energy decomposition analysis reveals that dispersion forces are predominant in these complexes. This study provides insights into the nature of van der Waals interactions between bicyclic heteroaromatics and Rg
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
Rotational spectrum of the tetrafluoromethane-ethylene oxide
No full textThe rotational spectrum of one conformer of the CF4–ethylene oxide complex has been measured by using a pulsed jet Fourier-transform microwave spectrometer. The observed conformer is stabilized by a CF3⋯O halogen bond, with a distance rC⋯O of ∼3.341 Å. No experimental evidence of the internal rotation of CF4 with respect to ethylene oxide has been observed, but it is expected to be almost free (V3 ∼ 14 cm−1 from ab initio calculations)
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
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