1,721,049 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
A determination of H-0 with the class gravitational lens B1608+656. II. Mass models and the Hubble constant from lensing
No full textWe present mass models of the four-image gravitational lens system B1608 + 656, based on information obtained through VLBA imaging, VLA monitoring, and Hubble Space Telescope (HST) WFPC2 and NICMOS imaging. We have determined a mass model for the lens galaxies that reproduces (1) all image positions within the observational errors, (2) two out of three flux-density ratios within about 10% from the observed ratios, and (3) the model time delays within 1% from their observed values, given our best estimate of the Hubble parameter. Using the time delays determined in a companion paper, we also find that the best isothermal mass model gives H-0 = 59(-6)(+7) km s(-1) Mpc(-1) for Omega(m) = 1 and Omega(Lambda) = 0.0, or H-0 = (65-63)(-6)(+7) km s(-1) Mpc(-1) for Omega(m) = 0.3 and Omega(Lambda) = 0.0-0.7. The statistical errors indicate the 95.4% (2 sigma) confidence interval. A systematic error of +/-15 km s(-1) Mpc(-1) is estimated from a 20% (1 sigma) uncertainty in the steepness of radial mass profile. This cosmological determination of H-0 agrees well with determinations from three other gravitational lens systems (i.e., B0218 + 357, Q0957 + 561, and PKS 1830-211), Type Ia supernovae, the Sunyaev-Zeldovich effect and local determinations. The current agreement on H-0-within the 1 sigma statistical errors-from four of five gravitational lens systems (1) emphasizes the reliability of its determination from isolated gravitational lens systems and (2) suggests that a close-to-isothermal mass profile can describe disk galaxies (e.g., B0218 + 357 and possibly PKS 1830-211), ellipticals (e.g., B1608 +/- 656), and central cluster ellipticals (e.g., 00957 + 561). The average of H-0 from B0218 + 357, Q0957 + 561, B1608 + 656, and PKS 1830-211, gives H-0(GL) = 69 +/- 7 km s(-1) Mpc(-1) for a flat universe with Omega(m) = 1 or H-0(GL) = 74 +/- 8 km s(-1) Mpc(-1) for Omega(m) = 0.3 and Omega(Lambda) = 0.0-0.7. When including PG 1115 + 080, these values decrease to 64 +/- 11 km s(-1) Mpc(-1) and 68 +/- 13 km s(-1) Mpc(-1), respectively. The errors are the estimated 2 a errors on the average. The Hubble parameter from gravitational lenses seems to agree best with local determinations of H-0 for a low-density universe, under the assumption that all lenses are nearly isothermal
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
A determination of H-0 with the class gravitational lens B1608+656. II. Mass models and the Hubble constant from lensing
No full textWe present mass models of the four-image gravitational lens system B1608 + 656, based on information obtained through VLBA imaging, VLA monitoring, and Hubble Space Telescope (HST) WFPC2 and NICMOS imaging. We have determined a mass model for the lens galaxies that reproduces (1) all image positions within the observational errors, (2) two out of three flux-density ratios within about 10% from the observed ratios, and (3) the model time delays within 1% from their observed values, given our best estimate of the Hubble parameter. Using the time delays determined in a companion paper, we also find that the best isothermal mass model gives H-0 = 59(-6)(+7) km s(-1) Mpc(-1) for Omega(m) = 1 and Omega(Lambda) = 0.0, or H-0 = (65-63)(-6)(+7) km s(-1) Mpc(-1) for Omega(m) = 0.3 and Omega(Lambda) = 0.0-0.7. The statistical errors indicate the 95.4% (2 sigma) confidence interval. A systematic error of +/-15 km s(-1) Mpc(-1) is estimated from a 20% (1 sigma) uncertainty in the steepness of radial mass profile. This cosmological determination of H-0 agrees well with determinations from three other gravitational lens systems (i.e., B0218 + 357, Q0957 + 561, and PKS 1830-211), Type Ia supernovae, the Sunyaev-Zeldovich effect and local determinations. The current agreement on H-0-within the 1 sigma statistical errors-from four of five gravitational lens systems (1) emphasizes the reliability of its determination from isolated gravitational lens systems and (2) suggests that a close-to-isothermal mass profile can describe disk galaxies (e.g., B0218 + 357 and possibly PKS 1830-211), ellipticals (e.g., B1608 +/- 656), and central cluster ellipticals (e.g., 00957 + 561). The average of H-0 from B0218 + 357, Q0957 + 561, B1608 + 656, and PKS 1830-211, gives H-0(GL) = 69 +/- 7 km s(-1) Mpc(-1) for a flat universe with Omega(m) = 1 or H-0(GL) = 74 +/- 8 km s(-1) Mpc(-1) for Omega(m) = 0.3 and Omega(Lambda) = 0.0-0.7. When including PG 1115 + 080, these values decrease to 64 +/- 11 km s(-1) Mpc(-1) and 68 +/- 13 km s(-1) Mpc(-1), respectively. The errors are the estimated 2 a errors on the average. The Hubble parameter from gravitational lenses seems to agree best with local determinations of H-0 for a low-density universe, under the assumption that all lenses are nearly isothermal.</p
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
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
Microlensing of multiply-imaged compact radio sources - Evidence for compact halo objects in the disk galaxy of B1600+434
No full textWe present the first unambiguous case of external variability of a radio gravitational lens, CLASS B1600+434. The Very Lai-ge Array (VLA) 8.5-GHz difference light curve of the lensed images, taking the proper time-delay into account, shows the presence of external variability with 14.6-sigma confidence.We investigate two plausible causes of this external variability: scattering by the ionized component of the Galactic interstellar medium and microlensing by massive compact objects in the bulge/disk and halo of the lens galaxy. Based on the tight relation between the modulation-index (fractional rms variability) and variability time scale and the quantitative difference between the light curves of both lensed images, we conclude that the observed short-term variability characteristics of the lensed images are incompatible with scintillation in our Galaxy. This conclusion is strongly supported by multi-frequency Westerbork Synthesis Radio Telescope (WSRT) observations at 1.4 and 5 Gi;z, which are in disagreement with predictions based on the scintillation hypothesis. Several arguments against scintillation might need to be reevaluated if evidence is found for significant scatter-broadening of lensed image B seen through the lens galaxy. However, the frequency-dependence and time scale of variability from image A are not affected by this and remain strong arguments against scintillation.On the other hand, a single superluminal jet-component in the source, having an apparent velocity 9 less than or similar to(nu(app)/c)less than or similar to 26, a radius of 2-5 mu as and containing 5-11 % of the observed 8.5-GHz source flux density, can reproduce the observed modulation-indices and variability time scale at 8.5 GHz, when it is microlensed by compact objects in the lens galaxy. It also reproduces the frequency-dependence of the modulation-indices, determined from the independent WSRT 1.4 and 5-GHz observations. The difference between the modulation-indices of the lensed images (i.e. 2.8% and 1.6% at 8.5 GHz in 1998 for images A and B, respectively), if not affected by scatter-broadening of image B by the ionized ISM of the lens galaxy, can be explained through a different mass-function for the compact objects in the bulge/disk and halo of the lens galaxy. Comparing the observations with microlensing simulations, we place a tentative lower limit of greater than or similar to 0.5 M. on the average mass of compact objects in the halo line-of-sight. The above-mentioned set of mass-function and source parameters is consistent, although not unique, and should only be regarded as indicative.The only conclusion fully consistent with the data gathered thus far is that we have indeed detected radio microlensing. The far reaching consequence of this statement is that a significant fraction of the mass in the dark-matter halo at similar to 6kpc (h=0.65) above the lens-galaxy disk in B1600+434 consists of massive compact objects.</p
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