1,721,394 research outputs found
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
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
Systematics of identified particle production in proton-proton, deuteron-gold and gold+gold collisions at RHIC energies
No full textIdentified mid-rapidity particle spectra and freeze-out properties are presented for 200 GeV pp, 200 GeV dAu and 62.4 GeV Au-Au collisions, measured in the STAR-TPC. The STAR-TPC is a unique tool to investigate identified bulk particle production from elementary pp to large multiplicity Au-Au collisions. Results are contrasted to previous experiments to provide an overview of bulk properties in heavy-ion collisions. Evolution of the identified particle spectra (π±, K±, p and p¯) with charged particle multiplicity and event centrality is investigated in detail. Significant hardening of the spectrum of heavy particles (kaons and protons/antiprotons) is found in central Au-Au collisions. The average transverse momentum of kaons and protons/antiprotons in high multiplicity pp and central dAu collisions is larger than in peripheral Au-Au collisions at the same energy. The average transverse momentum in 62.4 GeV and 200 GeV Au-Au collisions seem to only depend on event multiplicity. Particle production examined through particle-antiparticle ratios (π +/π−, K+/ K−, p¯/p) and unlike particle ratios (K−/π−, p¯/π−) show smooth evolution from pp to dAu to Au-Au collisions. Significant net baryon is present in the central collision zone in 62.4 GeV collisions and 200 GeV collisions. Strangeness production increases with centrality in peripheral collisions and saturates in medium-central to central collisions in heavy-ion collisions at 62.4 and 200 GeV, in contrast to lower SPS and AGS energies. Chemical freeze-out properties of the collision systems are obtained from particle ratios and the kinetic freeze-out properties from the shapes of particle spectra. Thermal model fits to the measured particle ratios yield a chemical freeze-out temperature ∼ 155 MeV in 200 GeV pp; 200 GeV dAu and 62.4 GeV Au-Au collisions. The extracted chemical freeze-out temperature is close to the critical phase transition temperature predicted by lattice QCD calculations. The kinetic freeze-out temperature extracted from hydrodynamically motivated blast-wave models shows a continuous drop from pp, dAu and peripheral to central Au-Au collisions, while the transverse flow velocity increases from ∼ 0.2 in pp to ∼ 0.6 in central 200 GeV Au-Au collisions. The kinetic freeze-out parameters in 62.4 GeV and 200 GeV Au-Au collisions seem to be governed only by event multiplicity/centrality. The kinetic freeze-out results are obtained from blast-wave fit to spectra data treating all particles as primordial ones. However, resonance decays may modify the spectral shapes significantly, and therefore may affect the extrapolated kinetic freeze-out parameters. In order to study this possible effect the data are fitted with the blast-wave model including resonances. It is found that the thus extracted parameters are consistent with those obtained without including resonances. This is because the resonance decays do not modify the spectral shapes significantly in the measured pT, region in STAR
Two-particle correlation studies in heavy ion collisions at the Large Hadron Collider
Full text linkResults on two-particle angular correlations in pPb at [square root sNN] =5.02 TeV and PbPb collisions at [square root sNN] =2.76 TeV are reported. The long-range correlations in pseudorapidity (“ridge\u27\u27) has been seen in various systems, including PbPb, pPb and pp systems. In this thesis, two-particle correlations in pPb collisions at nucleon-nucleon center-of-mass energy of 5.02 TeV are studied as a function of the pseudorapidity separation (Δ η) of the particle pair at small azimuthal angle separation (:Δ&phis;: \u3c π/3). The correlations are decomposed into a jet component that dominates the short-range correlations (:Δη: \u3c 1), and a component that persists at large Δη, which is the ridge. The ridge may be associated with collective behavior of the produced system, well described by hydrodynamics. The azimuthal correlations, after subtraction of the jet component, are characterized by the V 2 and V3 coefficient. The single-particle anisotropy parameters v2 and v 3 are extracted and normalized by their mid-rapidity value. The normalized v2(ηcm)/v 2(ηcm=-0.465) distribution as a function of the center-of-mass pseudorapidity ηcm is found to be asymmetric about ηcm = 0, with smaller values observed at forward proton direction pseudorapidity, and smaller value at backward Pb direction, but the decreasing trend towards the two sides is different. The normalized v3(η cm)/v3(η cm=-0.465) distribution has no significant pseudorapidity dependence within the statistical uncertainties. The underlying physics for the η dependence of the v2 parameter is under extensive research at the time of this thesis writing. The two-particle correlation method is widely used also in jet-like correlation studies. The jet axis direction can be identified effectively by a high pT particle. The away-side partner jet is quenched in heavy ion collisions due to medium interactions. The biggest challenge in jet correlation studies is the subtraction of the large underlying anisotropy flow backgroud. In previous studies, the flow background is calculated from the measured Fourier coefficients, which results in large uncertainties. In this thesis, the away-side jet shape of PbPb collisions at [square root sNN] =2.76 TeV is studied utilizing a novel method of subtracting flow background using the data itself. The away-side is enhanced by a relatively large recoil transverse momentum in a given η range. The two-particle correlation function is constructed from different η regions, one is close and the other far away from the away-side jet. These two η regions are symmetric about η=0, so the flow background is the same. The correlation function difference between these two regions, therefore, measures the away-side jet shape. The jet width is studied as a function of multiplicity and pT. It is found that the jet width increases with multiplicity, indicating jet broadening in medium
Measurement Of D0 Directed Flow and Elliptic Flow in Au+au Collisions at √SNN = 200 GEV
No full textA strongly interacting Quark Gluon Plasma (QGP) is created in relativistic heavy ion collisions at the Relativistic Heavy Ion Collider (RHIC). Owning to their large mass, charm quarks are produced by initial parton-parton hard scatterings and experience the entire evolution of the QGP medium created in heavy ion collisions. They can therefore be a valuable tool to study the early time dynamics and the properties of the QGP. Many experimental observables are exploited to extract the information of QGP. This thesis analyzes the directed flow (v1) and the elliptic flow (v2) of D0 mesons (carrying a charm quark) using data collected by the Heavy Flavor Tracker in the STAR experiment in 2014 and 2016 RHIC runs. The v1 and v2 are measured by the first and second order Fourier coefficients of the D0 azimuthal distribution relative to the reaction plane. The measurements help constrain the parameters in theoretical models to describe heavy quark dynamics in the QGP. The measurements are compared to the v1(2) of light flavors to shed additional insights on the QGP
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
Event-By-Event Correlations Between Lambda Hyperon and the Chiral Magnetic Effect Observables in Au+Au Collisions at 27 Gev from
No full textSpin-orbit interactions cause a global polarization (P) of Λ (Λ¯) with the vorticity (or total angular momentum) in the participant collision zone. The strong magnetic field mainly created by the spectator protons would split the Λ and Λ¯ global polarization (∆P = PΛ −PΛ¯ \u3c 0). Quantum chromodynamics (QCD) predicts topological charge fluctuation in vacuum, resulting in a chirality imbalance, or parity violation in a local domain. This would give rise to an imbalanced left- and right-handed Λ (Λ¯), ∆n = NL−NR /‹NL+NR› 6≠ 0, as well as a charge separation along the magnetic field, referred to as the chiral magnetic effect (CME). The latter can be characterized by the parity-even ∆γ and parity-odd ∆a1 observables. While measurements of the individual ∆P [1, 2], ∆γ, and ∆a1 have not led to affirmative conclusions on the CME or the magnetic field, correlations among these observables may reveal new insights [3, 4]. We report exploratory measurements of event-by-event correlations between ∆P and ∆γ, and between ∆n and ∆a1, by the STAR experiment in Au+Au collisions at √ snn= 27 GeV. No correlations have been observed beyond statistical fluctuations. Future endeavor would be to extract an upper limit from the data as well as to apply the correlation analysis to other data samples
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