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Diffuse absorption bands and the 2175 A feature - Results from a sample of galactic stars
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On the Diffuse Interstellar Bands Around 6200-a
No full textThe system of three diffuse bands situated near 6200 angstrom is discussed on the basis of high resolution, high signal-to-noise spectra. The intensity ratios of the 3 bands change from one line of sight to another suggesting the existence of a different carrier for each of them
Anomalous Extinction and Diffuse Interstellar Bands In the Direction of 2 Be Stars
No full textThe Be stars HD 44458 and HD 63462, characterized by peculiar extinction curves, were observed spectroscopically in the range of well-known diffuse interstellar bands - DIBs - (5780, 5797, 6196 and 6203 angstrom). The lack of some of the diffuse features in the observed spectra (or their extreme weakness) may be due to the fact that these bands originate only in diffuse interstellar clouds, whereas a substantial amount of the reddening observed in the spectra of Be stars originates in the circumstellar shell - a medium differing strongly in optical properties from typical interstellar clouds
The 5780-diffuse Band In Peculiar Interstellar Clouds
No full textThis paper presents the spectra of a sample of galactic stars in which the broad diffuse interstellar band at 5780 angstrom is strongly attenuated in relation to their colour excess and the neighbour feature at 5797 angstrom is absent. The unusually large width of the 5780 band which is found in the direction of the Orion Trapezium stars is discussed in terms of intrinsic and Doppler broadening. The same clouds (apparently fragments of the Orion parent cloud) are known to produce peculiar extinction. It is suggested that the high density of collapsing clouds facilitates sticking of the diffuse band carriers to grain surfaces where they loose their identity reacting with the bulk of grain material. The process of sticking also alters the optical properties of grains
Diffuse interstellar bands: Resolved rotational band structure at 5850 angstrom
No full textThe only candidate of what may be a resolved rotational vibrational band in the DIB Survey of Jenniskens & Desert (1994), the tripler of bands at 5844, 5850 and 5852 Angstrom, is examined in detail in order to establish the nature of these DIBs. We find that superposed on the broad lambda 5844 are four weak features, reminiscent of substructure found on top of the broad lambda 5778. The relative band strength of DIBs lambda 5844 and lambda 5850 correlates with the rotational temperature in the J = 0 and J = 1 levels of molecular hydrogen. However, we do not find variations in band shape that are consistent with substructure of a resolved rotational band profile. Instead, the narrow lambda 5850 is found to have a shoulder on the red and blue side of the main band, which can imply that this band itself is an unresolved rovib band with P,Q and R branches
Diffuse interstellar bands near 9600 angstrom: not due to C60(+) yet
No full textHigh spectral resolution studies of the two Diffuse Interstellar Bands (DIB) previously assigned to C60(+) (lambda 9577 and lambda 9632) confirm that these DIBs have the same full-width-at-half-maximum and behave similarly in dense cloud environments where the DIBs are weakened relative to the diffuse interstellar medium. Their relative strength, however, is less than previously reported and differs from the relative intensities measured from matrix isolation spectroscopy. A simultaneous search for the two laboratory derived vibronic tranistions of C60(+) at about 9366 and 9419 Angstrom has not lead to the detection of the two weak counterparts stronger than 15% of lambda 9577. We conclude that for the diffuse band spectrum to be consistent with C60(+), not only the measured band positions have to be slightly different in the gas-phase, but also the relative intensity of the two main lines has to differ significantly from that of the known laboratory data
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
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
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