1,721,018 research outputs found
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
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
Calibration of an Ultra-High Accuracy Polarimeter at the Part-Per-Million Level
Get PDFThe ability to accurately measure polarization changes at the part-per-million (ppm) level enables a wide variety of astronomical and defense-related programs, as light reflected by any medium tends to impart polarization. For instance, multi-wavelength, optical studies of Jupiter-sized planets around other stars may probe their atmospheres and eventually surfaces, even though the measurements are contaminated by 100,000 times as many stellar photons as planetary ones. Additionally, our pilot study of resident space objects suggests that potentially game-changing results may occur if polarization is calibrated to a high degree. We have developed the POLISH2 aperture-integrated, ground-based optical polarimeter at the Lick Observatory Shane 3-m telescope using two photoelastic modulators instead of conventional, rotating waveplates. This instrument measures AC-coupled intensity variations from 10-100 kHz due to the resonant modulators. Measurements of both strongly (0.1%-1%, or 1,000-10,000 ppm) and weakly polarized calibrator stars (0.0001%-0.001%, or 1-10 ppm) are necessary to calibrate for instrumental orientation and telescope-induced polarization, respectively. Since stellar polarization is due to scattering of starlight by intervening dust particles, stellar distance is linearly proportional to stellar polarization. While strongly polarized stars abound in astronomical stellar catalogs, such catalogs are incomplete below 0.01%-0.1% polarization. This is because 1) conventional polarimeters are limited to ~0.01% accuracy due to linear to circular polarization conversion in waveplates, and 2) unpolarized stars, necessarily bright, tend to saturate on conventional waveplate / CCD instruments. POLISH2, being designed to observe Venus and the Crab Pulsar (apparent visual magnitude ranges between -4 and 16, or a factor of 108 in dynamic range) with photon-limited sensitivity, is uniquely suited to measure stellar polarization to the ppm level. We have used the Lick Observatory 1-m telescope to perform a survey of bright stars to identify nearly unpolarized calibrator stars.
Laboratory calibration of POLISH2 is quite difficult, as the linear (LP) and circular polarization (CP) of even a bare, incandescent bulb with no reimaging optics is found to be LP = 0.67520% +/- 0.00054% and CP = -0.08643 +/- 0.00028%. Propagating the bulb through two collimating and focusing lenses, we measure LP = 3.0319 +/- 0.0032% and CP = -0.36029 +/- 0.00033%. Thus, propagation of light through lenses introduces both linear and circular polarization due to static stress frozen into the lens via the annealing process. Even linear film polarizers are found to be non-ideal, as they appear to introduce circular polarization with 2-3% amplitude depending on the rotational orientation of the linear polarizer. We find that integrating spheres reduce bulb polarization to LP = 0.02%-0.05% (200-500 ppm) and CP = 0.001%-0.002% (10-20 ppm), with larger spheres producing weaker polarization. Finally, cavity blackbodies are found to present the weakest linear polarization, with LP ~ 0.01% and |CP| ~ 0.01% (100 ppm) for two separate blackbodies. These measurements show that the best sources for ultra-high accuracy polarimetric calibration are stars themselves
Unambiguous Black Hole Mass from Polarimetry and Application to Hot Jupiters
Get PDFA novel technique for detecting light scattered by extrasolar planets is presented that has the potential to constrain orbital inclination and planet mass. To develop this technique, I have commissioned a high precision polarimeter on the Hale 5-m telescope at Palomar Observatory. The high mass X-ray binary Cygnus X-1 has been observed, which is a proxy for extrasolar planet studies. The single scattering model of Brown et al. (1978), widely used in the literature, predicts an orbital inclination for Cygnus X-1 that is inconsistent with the lack of observed X-ray eclipses to 4σ - 5σ. Previous studies have hinted at this discrepancy, but data quality was such that the confidence in such a discrepancy was not statistically significant. My observations represent the highest precision study of this object, and they illustrate the overwhelming complexity of the supergiant/black hole system. They also call into question the validity of the Brown et al. (1978) formalism, widely used by the community, for inclination estimation in binary systems.
Extrasolar planet host stars have also been observed, and precision of order one part per million has been achieved on bright targets. Precision attained on fainter host stars is of order one part in 10^5 . While scattered light from extrasolar planets has not been conclusively detected, a planetary transit in the HD 189733 system may have been observed in polarized light. Such an event is observed to be 1,000 times weaker in polarized light than in photometry, and it indicates a planetary transit of the Southern Hemisphere of the host star. Such geometric information is difficult to determine by other methods.
The integrated polarization of the debris disk surrounding γ Ophiuchi has been observed to high precision, and the position angle of net polarization is aligned with the disk major axis as seen by the Spitzer Space Telescope. This indicates the disk is primarily composed of forward scattering dust grains larger than the wavelengths of visible light.
Finally, Neptune-mass extrasolar planets orbiting close to their host stars have been modeled to be far too warm for liquid water oceans to exist in their upper atmospheres.</p
Nondetection of Polarized, Scattered Light from the HD 189733b Hot Jupiter
Get PDFUsing the POLISH instrument, I am unable to reproduce the large-amplitude polarimetric observations of Berdyugina et al. to the >99.99% confidence level. I observe no significant polarimetric variability in the HD 189733 system, and the upper limit to variability from the exoplanet is ΔP < 7.9 × 10^(–5) with 99% confidence in the 400-675 nm wavelength range. Berdyugina et al. report polarized, scattered light from the atmosphere of the HD 189733b hot Jupiter with an amplitude of two parts in 10^4. Such a large amplitude is over an order of magnitude larger than expected given a geometric albedo similar to other hot Jupiters. However, my nondetection of polarimetric variability phase-locked to the orbital period of the exoplanet, and the lack of any significant variability, shows that the polarimetric modulation reported by Berdyugina et al. cannot be due to the exoplanet
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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