1,720,997 research outputs found
Erratum: Force constants of the metaborate ion in alkali halides
Full text linkErratum for the article: Decius, J. C. ; Becker, Charles R. ; Fredericks, W. J. : Force constants of the metaborate ion in alkali halides, In: THE JOURNAL OF CHEMICAL PHYSICS (1972), 56, 10, 5189-5190.Hierbei handelt es sich um eine Korrektur zum Artikel: Decius, J. C. ; Becker, Charles R. ; Fredericks, W. J. : Force constants of the metaborate ion in alkali halides, In: THE JOURNAL OF CHEMICAL PHYSICS (1972), 56, 10, 5189-5190
Relaxation Times for Vibrational Absorption
No full textAuthor Institution: Oregon State CollegePresentations without an abstract printed in the proceedings do not have an abstract (image or text) in the Knowledge Bank record
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
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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Optical diffraction study of ultrasonic sound velocity in nitrous oxide and ammonia gases
Full text linkThe velocity of sound in gases was measured, using an ultrasonic wave train as a diffraction grating. The fundamental problems involved in the optical technique are discussed. An apparatus utilizing an objective lens of focal length 1.5 m and aperture f/20 was constructed and used at an ultrasonic frequency close to one Mc sec⁻¹ to photograph the diffraction of the Hg 5461 A line in argon, nitrogen, nitrous oxide, and ammonia at pressures from 0.23 to 10 atm, with exposures between 0.02 and 1100 seconds. In later work, optics based on the Lyot coronagraph were added to the apparatus, causing a reduction in background light. The intensity of the first-order diffraction image was found to be proportional to the square of pressure. By superimposing the diffraction image produced by a non-dispersive gas used as a standard on the image produced in the unknown gas, it was possible to measure V² with an error of ± 0.2 percent. Sources of this error are discussed. A well-defined dispersion curve was found for nitrous oxide, from which a relaxation time at one atm and 300° K of T = 0.99 x 10⁻⁶ sec was obtained, in excellent agreement with the results of workers using ultrasonic absorption or interferometry. Sound velocity measurements in ammonia at pressures up to six atm yielded V₀² = 19.122 x 10⁴m²sec⁻², in excellent agreement with the theoretical value. A correction for the non-ideality of ammonia, V²[subscript exp] = V[subscript i]² (1 - 13.9 x 10⁻³p), was determined. No dispersion was observed in ammonia at f/p values up to 2.15 Mc sec⁻¹atm⁻¹. When the results of other workers are critically evaluated, applying the correction formula determined here, all but one previously reported dispersions in ammonia disappear. The dispersion reported by Petralia for rotational relaxation is found to fit the V² limits predicted for vibrational relaxation and gives a relaxation time of about 0.6 x 10⁻⁸sec. The factors contributing to the width of the diffracted lines are discussed, and a method for using the line width to determine the maximum in the absorption curve is suggested
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A spectrophone study of vibrational relaxation in methane
Full text linkThe spectrophone method for the study of vibrational relaxation has been claimed to possess a distinct advantage over the more commonly used ultrasonic techniques in that it permits the relaxation of the various infrared-active vibrational modes in a polyatomic molecule to be studied separately. A discussion of the rate equations governing the exchange of energy between several degrees of freedom in polyatomic gases is given which shows that the characteristic relaxation frequencies for such a system are completely independent of the method of excitation, indicating that the information which can be obtained using the spectrophone is essentially the same as that to be found from ultrasonic measurements. An expression is derived for the spectrophone frequency response to be expected from a polyatomic gas which predicts that at sufficiently high light-chopping frequencies an increased loss in the spectrophone signal due to relaxation phenomena should be observed. A study of the spectrophone response in the frequency range where this increased signal loss occurs should-thus afford a means for determining the effective vibrational relaxation time of the gas in the spectrophone cell. An apparatus is described which was used to measure spectrophone signal amplitudes over a range of chopping frequencies from 200 to 1600 cps, at gas pressures from one atmosphere down to a few millimeters. Response curves obtained for methane gas at pressures of one atmosphere and one-half atmosphere exhibit the behavior predicted by the theory, but show no increased signal loss at the higher chopping frequencies. However, the response curves for methane at pressures of 5 mm, 10 mm, and 20 mm do exhibit such a high frequency loss; from these response data a vibrational relaxation time of T= 1.1 microseconds at one atmosphere has been assigned to methane. This value agrees within a factor of two with all similar results reported by other workers. Studies of the spectrophone frequency response obtained for mixtures of methane and carbon dioxide, with carbon dioxide concentrations of one percent and five percent, indicate that the presence of carbon dioxide serves to decrease the vibrational relaxation time in methane. Studies of the spectrophone frequency response obtained for three deuterated methanes, CH₃D, CH₂D₂, and CHD₃, yield values of T= 0.87 microseconds for CH₃D, T= 0.99 microseconds for CH₂D₂, and T= 1.45 microseconds for CHD₃, all at one atmosphere pressure. The longer time for CHD₃ is interpreted in terms of the decreased rotational velocity of the deuterium atoms in this molecule, which reduces the probability of vibrational- rotational energy transfer during molecular collisions
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
CO BOND MOMENT IN THE CARBONATE ION
No full textAuthor Institution: Department of Chemistry, Oregon State CollegeVaritation of the ratio in carbonates of the aragonite lattice leads to fine structure in the 12 region whose spacing and qualitative intensity can be fitted satisfactorily by the introduction of a nearest neighbor coupling constant in the potential energy. The coupling constant is believed to arise from dipole-dipole forces. From the coupling constant the value of the CO bond moment is found to be debyes in , debyes in . The coupling is so large in (on account of the inverse cube dependence upon interdipole distance) that the perturbation theory cannot be applied without modification
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
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