1,721,201 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
Production des bosons Z et du double charme avec ALICE auprès du LHC
No full textIn Nature, free quarks and gluons cannot be observed due to the confinement properties of quantum chromodynamics (QCD). However, in extreme conditions, a state of matter called the Quark-Gluon Plasma (QGP) is formed in which quarks and gluons are deconfined. The QGP can be created and studied by colliding ultrarelativistic heavy nuclei. At the Large Hadron Collider (LHC), collisions between lead (Pb) nuclei take place and are studied at the various experiments. In this thesis we present measurements on Z bosons and J/ψ, reconstructed in the muon spectrometer of the ALICE detector. Observations from PbPb collisions are subject to effects unrelated to the QGP, and it is important to disentangle these from QGP effects. In particular, parton distributions are different in heavy nuclei than in unbound protons and neutrons. In order to describe the production of probes with large transverse momentum, special objects called nuclear parton distribution functions (nPDFs) are necessary. They are a crucial ingredient of calculations of cross sections in heavy ion collisions, but cannot be obtained from first principles calculations in QCD. Instead, they are instead obtained from fits to data which include, among others, measurements of electroweak bosons. The latter can therefore be used to constrain or verify the accuracy of the nPDFs. In this thesis, the production of Z bosons in PbPb collisions at a center-of-mass energy per nucleon pair of 5.02 TeV with the ALICE detector is reported. The results strongly show a preference for models that take nuclear modifications to PDFs into account. This indicates that parton distributions in nucleiare not a simple superposition of protons and neutrons.In the near future, proton-oxygen and oxygen-oxygen collisions will take place at the LHC. We detail projections of Z boson production in these collisions, obtained by extrapolating existing cross sections from the ALICE and LHCb experiments. With the expected integrated luminosities for the two collision systems, measurements are found to be unfeasible.In proton-proton collisions, heavy particles such as the J/ψ are produced from a single partonic scatter-ing (SPS). It is possible to create a pair of J/ψ from such a process, as opposed to a single J/ψ. However, J/ψ pairs can also be created through another mech-anism. Because the densities of partons increase rapidly at high energies, it becomes possible for two parton scatterings to occur during a single pp colli-sion. This is referred to as double parton scattering (DPS). J/ψ pairs can therefore be used as a tool to study relative contributions of SPS and DPS. In this thesis, a measurement of the production cross section of J/ψ pairs in proton-proton collisions at sqrt(s) = 13 TeV is presented. The measurement serves as a first of its kind in ALICE. It shows good agreement the cross section obtained by LHCb collaboration, al-though experimental uncertainties are large. Future LHC data taking periods will provide a larger data sample, which will allow for a measurement with bet-ter experimental precision. This could enable a mea-surement in which SPS and DPS contributions can be separated.Dans la nature, les propriétés de con-finement du chromodynamique quantique (QCD) interdisent l’observation de quarks et de gluons libres. Cependant, dans des conditions extrêmes, un état de matière appelé le plasma de quarks et gluons (QGP) dans lequel les quarks et gluons sont déconfinés peut exister. Ce QGP peut être créé et étudié grâce à des collisions entre des noyaux lourds ultra-relativistes. Au Large Hadron Collider (LHC), des collisions entre des noyaux de plomb (Pb) prennent place et sont étudiées dans plusieurs expériences. Cette thèse présente les mesures de la production de bosons Z et de J/ψ reconstruits dans le spectromètre à muons du détecteur ALICE.Certaines observables dans les collisions PbPb sont impactées par des effets non liés au QGP, effets qu’il est important de décorréler de ceux liés au QGP. Les distributions des partons dans les noyaux (nPDF) qui jouent un rôle important dans de nombreux processus en sont un très bon exemple. Les nPDF constituent un ingrédient crucial pour les calculs des sections efficaces dans des collisions d’ions lourds et elles ne peuvent pas être obtenues par des calculs QCD. Les nPDF sont obtenues par des ajustements aux don-nées de certaines mesures incluant, parmi d’autres, celle des bosons électrofaibles. Ces dernières peu-vent donc être utilisées pour contraindre ou vérifier la justesse des nPDFs. Dans cette thèse, la production des bosons Z dans des collisions PbPb à une énergie de 5.02 TeV par paire de nucléons dans le centre de masse avec le détecteur ALICE est détaillée. Les résultats montrent une forte préférence pour les modèles qui incluent des modifications nucléaires dans les PDF. Cela indique que les distributions des partons dans les noyaux ne sont pas des superposi-tions simples des protons et neutrons.Dans un avenir proche, des collisions proton-oxygène et oxygène-oxygène prendront place au LHC. Les estimations de la production du boson Z dans ces col-lisions, obtenues par l’extrapolation des sections efficaces actuelles des expériences ALICE et LHCb sont calculées. Avec la luminosité intégrée attendue pour ces deux systèmes de collision, le mesure apparaît comme impossible.Dans une collision proton-proton, les particules lourdes comme le J/ψ sont produites dans une collision parton-parton dure et unique (SPS). Il est également possible de créer une paire de J/ψ via ce même processus. La densité des partons augmentant rapide-ment à hautes énergies, il devient possible que deux diffusions prennent place lors une seule collision pp. Cette double diffusion dure de parton (DPS) constitue un autre mécanisme de génération d’une paire de J/ψ. La production de paires de J/ψ peut par conséquent être utilisée pour étudier les contributions relatives des processus SPS et DPS. Dans cette thèse, une mesure de la section efficace des paires de J/ψ dans des collisions proton-protons à une énergie de 13 TeV par paire de nucléon dans le centre de masse est rapportée pour la première fois dans ALICE. Elle montre, malgré des incertitudes expérimentales importantes, un bon accord avec la section efficace obtenue par la collaboration LHCb. Les futures prises des données au LHC fourniront une statistique plus importante qui permettra de faire une mesure de meilleure précision dans laquelle les contributions SPS et DPS pourraient être séparées
Search for the Chiral Magnetic Effect with the ALICE detector
No full textInternational audienceIn non-central heavy-ion collisions, spectator protons that do not participate in the interaction create strong magnetic fields. The strength of these fields allows testing an effect based on the hypothesized properties of QCD. The presence of so-called topological configurations can give rise to domains that carry net chirality. Coupled with the aforementioned magnetic fields, they may induce a charge separation of the particles generated in the collisions. This charge separation is called the Chiral Magnetic Effect (CME) and can be measured through charged-particle angular correlations. Measurements of the γ 1,1 correlator, which is sensitive to the CME, are shown for Pb–Pb collisions at sNN=5.02TeV as well as for Xe–Xe collisions at sNN=5.44TeV . These are found to have a significant charge dependence between opposite-sign and same-sign charge pairs. This behavior is consistent with a CME-like signal. However, the δ 1 correlator, which measures charge correlations unrelated to any symmetry plane (i.e. background), was measured in Xe–Xe collisions and also shows a significant charge dependence. This prevents a clear interpretation of the γ 1,1 correlator. Novel methods to constrain the CME contribution to the γ 1,1 correlator are necessary
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
Z-boson and double charm production with ALICE at the LHC
No full textIn Nature, free quarks and gluons cannot be observed due to the confinement properties of quantum chromodynamics (QCD). However, in extreme conditions, a state of matter called the Quark-Gluon Plasma (QGP) is formed in which quarks and gluons are deconfined. The QGP can be created and studied by colliding ultrarelativistic heavy nuclei. At the Large Hadron Collider (LHC), collisions between lead (Pb) nuclei take place and are studied at the various experiments. In this thesis we present measurements on Z bosons and \jpsi, reconstructed in the muon spectrometer of the ALICE detector. Observations from PbPb collisions are subject to effects unrelated to the QGP, and it is important to disentangle these from QGP effects. In particular, parton distributions are different in heavy nuclei than in unbound protons and neutrons. In order to describe the production of probes with large transverse momentum, special objects called nuclear parton distribution functions (nPDFs) are necessary. They are a crucial ingredient of calculations of cross sections in heavy ion collisions, but cannot be obtained from first principles calculations in QCD. Instead, they are instead obtained from fits to data which include, among others, measurements of electroweak bosons. The latter can therefore be used to constrain or verify the accuracy of the nPDFs. In this thesis, the production of Z bosons in PbPb collisions at a center-of-mass energy per nucleon pair of 5.02 TeV with the ALICE detector is reported. The results strongly show a preference for models that take nuclear modifications to PDFs into account. This indicates that parton distributions in nuclei are not a simple superposition of protons and neutrons. In the near future, proton-oxygen and oxygen-oxygen collisions will take place at the LHC. We detail projections of Z boson production in these collisions, obtained by extrapolating existing cross sections from the ALICE and LHCb experiments. With the expected integrated luminosities for the two collision systems, measurements are found to be unfeasible. In proton-proton collisions, heavy particles such as the \jpsi are produced from a single partonic scattering (SPS). It is possible to create a pair of \jpsi from such a process, as opposed to a single \jpsi. However, \jpsi pairs can also be created through another mechanism. Because the densities of partons increase rapidly at high energies, it becomes possible for two parton scatterings to occur during a single pp collision. This is referred to as double parton scattering (DPS). \jpsi pairs can therefore be used as a tool to study relative contributions of SPS and DPS. In this thesis, a measurement of the production cross section of \jpsi pairs in proton-proton collisions at sqrt(s) = 13 TeV is presented. The measurement serves as a first of its kind in ALICE. It shows good agreement the cross section obtained by LHCb collaboration, although experimental uncertainties are large. Future LHC data taking periods will provide a larger data sample, which will allow for a measurement with better experimental precision. This could enable a measurement in which SPS and DPS contributions can be separated
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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