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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
Messung der polarisierten Strukturfunktion g1(x, Q 2) des Protons mit dem HERMES-Experiment
No full textDie vorliegende Arbeit beschreibt die Messung der polarisierten Strukturfunktion g1p des Protons in der polarisationsabh"angigen tief inelastischen Positron-Proton-Streuung bei einer Schwerpunktenergie von 7.5 GeV. Die Analyse umfasst die 1997 mit dem Hermes-Experiment am Hera-Positronring aufgezeichneten Daten der Streuung polarisierter Positronen der Energie 27.6 GeV an einem polarisierten Wasserstofftarget. Aus den Z"ahlraten der inklusiv nachgewiesenen, selektierten Positronen f"ur die parallele und die antiparallele Ausrichtung der Spinvektoren von Strahlteilchen und Targetatomen wurde die Streuquerschnitts- Asymmetrie der Positron-Proton-Streuung bestimmt. In verschiedenen Korrekturverfahren wurden Untergrundprozesse, Spektrometereinfl"usse sowie Strahlungskorrekturen ber"ucksichtigt. Die Untergrundkorrekturen wurden aus den Daten, die Spektrometerkorrekturen aus einer Monte-Carlo- Simulation ermittelt. Die Abh"angigkeit der Monte-Carlo- und Strahlungskorrekturen von der gew"ahlten Modell-Asymmetrie zur Beschreibung der polarisationsabh"angigen Effekte wurde durch die Anwendung eines iterativen Verfahrens minimiert. Aus der vollst"andig korrigierten Streuquerschnitts-Asymmetrie wurde die Asymmetrie g1/F1 im kinematischen Bereich 0.021 0.8 GeV^2 mit einer systematischen Unsicherheit von etwa 8% bei einer statistischen Genauigkeit von 6% bis 20%, ansteigend f"ur abnehmende x-Werte, bestimmt. Die aus g1/F1 berechnete polarisierte Strukturfunktion g1p(x,Q2) wird, unter der Annahme einer von q2 unabh"angigen Asymmetry g1/F1, zu einem festen Wert Q2_0 entwickelt. Ihr erstes Moment im gemessenen x-Bereich betr"agt int_{0.021}^{0.85} dx g1p(x,Q2_0) = 0.122 =- 0.003 (stat) =- 0.010 (sys) at Q2_0 = 2.5 GeV^2. Der Vergleich mit den Werten des SMC-Experimentes am CERN und des E143-Experimentes am SLAC f"ur das erste Moment von g1p wurde unter Anwendung des gleichen Integrationsschemas f"ur den jeweils gemeinsam gemessenen x-Bereich sowie f"ur gleiche Q2_0 Werte durchgef"uhrt. Das Ergebnis der vorliegenden Analyse befindet sich, bezogen auf die statistische Genauigkeit der Messungen, in "Ubereinstimmung innerhalb von 0.6 bzw. 1.2 Standardabweichungen mit den Resultaten des E143- bzw. SMC-Experimentes. Durch Extrapolation der Strukturfunktion auf den gesamten x-Bereich [0,1] wird das erste Moment zu \int_{0}^{1} dx g1p(x,Q2_0) = 0.132 +- 0.003 (stat) +- 0.010 (sys) +- 0.006 (extr) bestimmt, wobei der zus"atzliche Fehler die Unsicherheit in der Extrapolation x -> 0 wiedergibt. Die Interpretation der vorliegenden Messung im Rahmen des Quark-Parton-Modells unter Ber"ucksichtigung von QCD-Korrekturen der Ordnung O(alphaS^3) ergibt einen Beitrag der Quarks zum Gesamtspin des Nukleons von (30 +- 10)% f"ur Q2_0 = 2.5 GeV^2. Dieses Ergebnis entspricht einer Abweichung von der Ellis-Jaffe-Vorhersage um 2.5 Standardabweichungen, bezogen auf den angegebenen Gesamtfehler, und f"uhrt im Kontext des Quark-Parton-Modells zur Interpretation negativ polarisierter Strange-Seequarks mit einem Beitrag von (-9 +- 4)% f"ur Q2_0 = 2.5 GeV^2. Von verschiedenen Gruppen werden aus QCD-Analysen unterschiedlicher Datens"atze Beitr"age der Quarks zum Nukleonspin von 19% bis 44% angegeben. Unter Hinzunahme der Hermes-Messung der polarisierten Neutronstrukturfunktion g1n wurde der Wert der fundamentalen Bjorken-Summenregel f"ur Q2_0 = 2.5 GeV^2 bestimmt. Dieser Wert befindet sich, bei einer auf den Gesamtfehler bezogenen Genauigkeit von 13%, innerhalb von 0.5 Standardabweichungen in "Ubereinstimmung mit der theoretischen Vorhersage, berechnet unter Ber"ucksichtigung von QCD-Korrekturen der Ordnung O(\alphaS^3).The subject of this thesis is the measurement of the polarised structure function g1p of the proton in deeply inelastic positron-proton-scattering at a centre of mass energy of 7.5 GeV. The data used in the analysis were recorded during the 1997 running period of the Hermes experiment using a longitudinally nuclear polarised hydrogen target in the 27.6 GeV Hera polarised positron storage ring. The cross section asymmetry of positron-proton-scattering has been measured by counting the number of inclusively reconstructed and selected positrons with target spin vector parallel or antiparallel to the beam spin direction. Background processes, spectrometer effects, and radiative corrections have been taken into account by applying different correction procedures. Here background corrections were determined from data while spectrometer corrections were computed from Monte Carlo simulation. The dependence of Monte Carlo and radiative corrections on the model asymmetry chosen to describe polarisation dependent effects has been minimised by applying an iterative procedure. From the fully corrected cross section asymmetry the asymmetry g1/F1 has been computed in the kinematic region 0.021 0.8 GeV^2 with a systematic uncertainty of 8% and a statistical accuracy of 6% to 20%, raising for decreasing x values. The polarised structure function g1p(x,Q2), determined from the asymmetry g1/F1 , was evoluted to a common Q2_0 value assuming g1/F1 to be independent of Q2. Its first moment evaluated in the measured x region is int_{0.021}^{0.85} dx g1p(x,Q2_0) = 0.122 =- 0.003 (stat) =- 0.010 (sys) at Q2_0 = 2.5 GeV^2. This result has been compared with those from E143 at SLAC and from SMC at CERN, both calculated with the same integration scheme and for the kinematic range of Hermes. With respect to the statistical uncertainties the agreement is better than 0.6 and 1.2 standard deviations, respectively. Extrapolation over the entire x range [0,1] yield for the first moment\int_{0}^{1} dx g1p(x,Q2_0) = 0.132 +- 0.003 (stat) +- 0.010 (sys) +- 0.006 (extr) where the additional error gives the uncertainty in the extrapolation x -> 0. The interpretation of this measurement in the framework of the quark parton model taking QCD corrections of the order O(alphaS^3) into account results in a contribution of the quarks to the total nucleon spin of (30 +- 10)% at Q2_0 = 2.5 GeV^2. This result corresponds to a deviation from the Ellis-Jaffe prediction by 2.5 standard deviation regarding the given total uncertainty. Within the quark parton model the deviation can be interpreted as negative polarisation of the strange sea quarks with a contribution of (-9 +- 4)% at Q2_0 = 2.5 GeV^2. Different groups give contributions of the quarks to the nucleon spin of 19% to 44% which were obtained from QCD analyses of various data sets. The fundamental Bjorken sum rule has been determined at Q2_0 = 2.5 GeV^2 using the Hermes measurement of the polarised neutron structure function g1n. With respect to the experimental accuracy of 13 %, the result agrees within 0.5 standard deviation with the theoretical prediction taking QCD corrections of the order O(alphaS^3) into account
Measurement of the polarized structure function of the proton with the HERMES experiment
No full textVariations 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
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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