1,720,953 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
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
Reaktivitätsverhalten subvalenter Hauptgruppenmetallorganyle gegenüber Verbindungen der fünften Hauptgruppe: Neue Wege zur Darstellung von Dipnictenen
No full textGegenstand dieser Arbeit waren Reaktivitätsstudien subvalenter Magnesiumorganyle gegenüber verschiedenen Antimonalkylen sowie vergleichende Reaktionen subvalenter Aluminium- und Galliumorganyle gegenüber des Antimon-, Arsen- und Phosphorsamiden und -halogeniden.
In situ 1H-NMR-Reaktionsstudien der Reaktionen von [ddpMg]2 1 mit SbMe3 5, SbEt3 6, SbnBu3 7 und SbiBu3 8 sowie entsprechende Reaktionen von [ttpMg]2 2 mit 5 und 6 zeigten bei Reaktionstemperaturen von 120 °C jeweils die Aktivierung der Antimon-Kohlenstoff-Bindungen, wobei die Reaktionszeiten mit Zunahme des sterischen Einflusses der am Antimonatom gebundenen Alkylreste anstiegen. In allen Reaktionen zeigte sich ein vergleichbarer Reaktionsverlauf, der jeweils zu zwei verschiedenen Reaktionsprodukten führte. In allen Reaktionen wurden die homoleptischen Magnesiumkomplexe ddp2Mg (1 + 5 – 8) bzw. ttp2Mg (2 + 5, 6), welche bereits literaturbekannt sind, gebildet und eindeutig identifiziert. Im Falle der Reaktion zwischen 2 und 5 konnte zudem die alkylverbrückte Magnesiumverbindung [ttpMg(µ Me)]2 16 isoliert und strukturell charakterisiert werden.
Die Analogie der Reaktionsverläufe und der resultierenden 1H-NMR-Spektren der Reaktionen von 1 mit 5 – 8 sowie 2 mit 5 und 6 legt die Bildung entsprechender alkylverbrückter Magnesiumspezies des Typs [LMg(µ-R)]2 (L = ddp, ttp; R = Me, Et, nBu, iBu) nahe, konnten aber im Rahmen dieser Arbeit nicht strukturell bewiesen werden. Mit [ddpMg(µ-Me)]2 und [ddpMg(µ-nBu)]2 sind zwei Produkte bereits literaturbekannt. Diese wurden in den 1H-NMR-Reaktionsspektren zwischen 1 und 5 sowie zwischen 1 und 7 neben ddp2Mg als weitere Reaktionsprodukte eindeutig nachgewiesen. Das Auftreten antimonhaltiger Reaktionsprodukte mit direkten Mg Sb-Bindungen konnte im Gegensatz zu den bereits von Schulz et al. publizierten Sb8 Clustern aus Reaktionen zwischen 1 und 2 mit Sb2Me4 und Sb2Et4 nicht beobachtet werden. Stattdessen wurde die Bildung metallischer Niederschläge beobachtet, die EDX-Analysen zufolge aus Magnesium und Antimon bestehen.
Reaktionen der subvalenten Gruppe 13-Diyle ddpAl 3 und ddpGa 4 mit Antimon-, Arsen- und Phosphoramiden und -halogeniden zeigten klare Trends bezüglich der Reaktivität sowie der Reaktionsverläufe. Während Reaktionen von 4 mit SbCl3 und AsCl3 bereits bei Raumtemperatur unter Eliminierung von ddpGaCl2 zur Bildung der Dipnictene [ddp(Cl)Ga]2Sb2 19 und [ddp(Cl)Ga]2As2 25 führte, zeigte sich bei analogen Reaktionen mit PCl3 und PBr3 keine Bildung entsprechender Diphosphene. Die Reaktionen endeten jeweils mit der Bildung der doppelten Insertionsprodukte [ddp(Cl)Ga]2PCl 26 und [ddp(Br)Ga]2PBr 27. Diese sind offenkundig deutlich stabiler als die im Verlaufe der analogen Reaktionen mit AsCl3 und SbCl3 gebildeten Doppelinsertionsprodukte, die als Reaktionsintermediate postuliert werden.
Entsprechende Reaktionen von ddpGa 4 Antimon-, Arsen- und Phosphoramiden benötigten deutlich harschere Reaktionsbedingungen. Während die Reaktion von 4 mit Sb(NMe2)3 9, die unter Eliminierung von ddpGa(NMe2)2 und anschließender Bildung des Distibens [ddp(Me2N)Ga]2Sb2 17 verläuft bei einer Reaktionstemperatur 80 °C innerhalb von 24 Stunden abgeschlossen ist, benötigte es für die entsprechende Reaktion mit dem sterisch anspruchsvolleren Amid Sb(NMeEt)3 13 eine Reaktionszeit von fünf Tagen bei 60 °C unter solvensfreien Bedingungen, um das analoge Distiben [ddp(EtMeN)Ga]2Sb2 18 darzustellen. Hier zeigte sich deutlich eine Korrelation der Reduktionsstärke von 4 mit dem sterischen Anspruch des Reaktionspartners, Reaktionen von 4 mit Sb(NEt2)3 10, Sb(NiPr2)3 11 und Sb(NTMS2)3 12 konnten dagegen selbst bei langen Reaktionszeiten und hohen Reaktionstemperaturen nicht beobachtet werden.
Reaktivitätsstudien von ddpGa 4 mit den leichteren Elementamiden As(NMe2)3 14 und P(NMe2)3 zeigten im Vergleich zu der Reaktion von 4 mit Sb(NMe2)3 9 einen Anstieg der E-N-Bindungsstärke (E = Sb, As, P) in Richtung von Antimon zu Phosphor. Während 4 die Sb-N-Bindung in 9 bereits bei 80 °C innerhalb von 24 Stunden unter Eliminierung von ddpGa(NMe2)2 und der Bildung des Distibens [ddp(Me2N)Ga]2Sb2 17 aktiviert, benötigt die entsprechende Reaktion mit 14 Temperaturen von 160 °C bei einer Reaktionszeit von fünf Tagen, bis die Bildung des analogen Diarsens [ddp(Me2N)Ga]2As2 22 abgeschlossen ist. Eine Aktivierung der P-N-Bindung von P(NMe2)3 durch 4 konnte dagegen nicht mehr beobachtet werden. Die Reaktion von ddpAl 3 mit As(NMe2)3 14 hingegen führte bereits bei einer Reaktionstemperatur von 80 °C nach 24 Stunden zur Bildung des Aluminium-koordinierten Diarsen [ddp(Me2N)Al]2As2 24. Dieser Befund belegt das stärkere Reduktionspotential von ddpAl 3 im Vergleich zu ddpGa 4. Der Versuch, dass Diarsen [ddp(Me2N)Ga]2As2 22 durch Reaktion von 4 mit AsCl2NMe2 15 unter Eliminierung von ddpGaCl2 darzustellen, gelang nicht. Stattdessen wurde das unsymmetrisch-substituierte Diarsen [ddp(Me2N)Ga]As2[Ga(Cl)ddp] 23 unter Eliminierung von ddpGaCl2 und ddpGa(Cl)NMe2 erhalten.
Die Thermolyse der Distibene [ddp(Me2N)Ga]2Sb2 17 und [ddp(Cl)Ga]2Sb2 19 führte unter Eliminierung von ddpGa 4 und ddpGa(NMe2)2 bzw. ddpGaCl2 selektiv zur Darstellung der ersten beiden Sb-Analoga von Bicyclo[1.1.0]butan [ddp(Me2N)Ga2(µ,η1:1-Sb4)] 20 und [ddp(Cl)Ga2(µ,η1:1-Sb4)] 21. Diese Verbindungen sind präzedenzlos in der Antimonchemie.
Die Ergebnisse dieser Arbeit zeigen zusammenfassend in beeindruckender Weise einen generellen Trend zur Bildung von Dipnictenen durch Reaktionen von ddpAl und ddpGa mit Halogeniden- und Amiden der schwereren Elementhomologen des Phosphors, und belegen das herausragende synthetische Potential von subvalenten Hauptgruppen-metallorganylen. Die Darstellung der Dipnictene durch Insertions Reduktions-reaktionen von ddpAl und ddpGa zeigt einen klaren Vorteil gegenüber der klassischen Darstellungsweise von Diarsenen und Distibenen. Es bedarf im Vorfeld keiner gezielten Synthese sterisch anspruchsvoller Arsen- und Antimonprecursoren, in welchen die Reste nach anschließender Reduktion eine mögliche As=As- oder Sb=Sb-Doppelbindung stabilisieren sollen. ddpAl und ddpGa wirken gleichzeitig als Reduktionsmittel sowie als koordinierende, sterisch anspruchsvolle Liganden, welche eine hinreichende kinetische Stabilisierung der in dieser Arbeit dargestellten Dipnictene erlauben. Dibismutene bestätigen diesen Trend durch Bildung von Element-Element-Doppelbindungen innerhalb der Reihe, welche bereits ausgehend von Reaktionen zwischen ddpGa und Bi(NEt2)3 und den Bismutalkoxiden Bi(OR3)3 (R = OSO2CF3, OC6F5) dargestellt werden konnten. Entsprechende Reaktionen mit Phosphorhalogeniden verliefen unter Bildung von Gallium-disubstituierten Phosphanen des Typs [ddp(X)Ga]2PX2 (X = Cl, Br), in welchen ddpGa in zwei PX-Bindungen von PX3 (X = Cl, Br) insertiert.This work is focused on reactivity studies of low valent magnesium compounds towards various antimony alkyls as well as low valent aluminum and gallium compounds toward antimony-, arsenic- and phosphorus halides and -amides.
In situ 1H-NMR-spectroscopic studies on the reactions of [ddpMg]2 1 with SbMe3 5, SbEt3 6, SbnBu3 7, and SbiBu3 8 and reactions of [ttpMg]2 2 with 5 and 6 showed, that the antimony-carbon bonds are activated at reaction temperatures of 120 °C. The necessary reaction times increased with increasing steric demand of the alkyl groups attached to the antimony atom. All reactions showed a comparable reaction pathway with two different reaction products, including the homoleptic magnesium complexes ddp2Mg (1 + 5 – 8) and ttp2Mg (2 + 5, 6), which are already known in the literature. In the case of the reaction between 2 and 5, it was possible to isolate and structurally characterize the Me-bridged magnesium compound [ttpMg(μ Me)]2 16. According to the analogy of all reactions between 1 with 5 – 8 and 2 with 5 and 6, we propose the formation of alkyl-bridged magnesium species of the type [LMg(μ-R)]2 (L = ddp, ttp; R = Me, Et, nBu , iBu) in addition to the formation of ddp2Mg and ttp2Mg. [ddpMg(μ-Me)]2 and [ddpMg(μ-nBu)]2 are already known in the literature and were identified by 1H-NMR-Spectroscopy as another reaction product in the reactions between 1 and 5 as well as 1 and 7. Antimony-containing reaction products with direct Mg-Sb bonds were neither observed nor characterized, in contrast to published Sb8-clusters from by Schulz et al. from reactions between 1 and 2 with Sb2Me4 and Sb2Et4.
Reactions of the low valent group 13 diyls ddpAl 3 and ddpGa 4 with antimony-, arsenic- and phosphorus halides and -amides showed clear trends in reactivity and reaction pathways. While reactions of 4 with SbCl3 and AsCl3 occured at room temperature with elimination of ddpGaCl2 and subsequent formation of the dipnictenes [ddp(Cl)Ga]2Sb2 19 and [ddp(Cl)Ga]2As2 25, analogous reactions of 4 with PCl3 and PBr3 did not result in formation of corresponding diphosphenes. Both reactions occurred with twofold insertion of ddpGa into the P-X bond (X = Cl, Br) and formation of [ddp(Cl)Ga]2PCl 26 and [ddp(Br)Ga]2PBr 27.
In contrast, reactions of ddpGa 4 with antimony-, arsenic- and phosphorus amides required significantly harsher reaction conditions compared to the corresponding halides. While 4 reacts with Sb(NMe2)3 9 at 80 °C within 24 hours with elimination of ddpGa(NMe2)2 and subsequent formation of the distibene [ddp(Me2N)Ga]2Sb2 17, the reaction of 4 with the sterically more demanding amide Sb(NMeEt)3 13 required a reaction time of five days at 60 °C under solvent-free conditions for the formation of the analogous distibene [ddp(EtMeN)Ga]2Sb2 18. A strong correlation of the reduction strength of 4 with the steric demand of the reaction partner is seen and as a consequence, reactions of 4 with sterically more demanding stibanes Sb(NEt2)3 10, Sb(NiPr2)3 11, and Sb(NTMS2)3 12 were not observed, even after long reaction times and high reaction temperatures.
Reactivity studies of ddpGa 4 with As(NMe2)3 14 and P(NMe2)3 showed an increase in E-N binding strength compared to the reaction of 4 with Sb(NMe2)3 9 (E = Sb, As, P) in the direction of antimony to phosphorus. Whiles 4 was found to activate the Sb-N bond in 9 already at 80 °C within 24 hours with elimination of ddpGa(NMe2)2 and subsequent formation of [ddp(Me2N)Ga]2Sb2 17, the analogues reaction of 4 with 14 required reaction temperatures of 160 °C and a reaction time of five days to form the analogous diarsene [ddp(Me2N)Ga]2As2 22, whereas the P-N-bond of P(NMe2)3 by 4 could not be activated at all. On the other hand, a reaction of ddpAl 3 with As(NMe2)3 14 led to an aluminum-coordinated diarsene [ddp(Me2N)Al]2As2 24 after 24 hours at a reaction temperature of 80 °C, clearly demonstrate the stronger reduction potential of ddpAl 3 compared to ddpGa 4. Any attempts to prepare the diarsene [ddp(Me2N)Ga]2As2 22 by reaction of 4 with AsCl2NMe2 15 with elimination of ddpGaCl2 failed, resulting in unsymmetrical substituted diarsene [ddp(Me2N)Ga]As2[Ga(Cl)ddp] 23 with elimination of ddpGaCl2 and ddpGa(Cl)NMe2.
Thermolysis of the distibenes [ddp(Me2N)Ga]2Sb2 17 and [ddp(Cl)Ga]2Sb2 19 occurred with elimination of ddpGa 4, ddpGa(NMe2)2 and ddpGaCl2 respectively, and formation of the first two Sb analogues of bicyclo[1.1.0]butane [ddp(Me2N)Ga2(μ,η1:1-Sb4)] 20 and [ddp(Cl)Ga2(μ,η1:1-Sb4)] 21.
In summary, the results of this work show in an impressive manner a general trend towards the formation of dipnictenes by reactions of ddpAl and ddpGa with halides- and amides of the heavier element homologues of phosphorus and thus the outstanding synthetic potential of low valent main-group organometallics. The synthesis of dipnictenes by insertion-reduction-reactions of ddpAl and ddpGa shows an clear advantage over the classical synthesis of diarsenes and distibenes. It requires no systematic synthesis of sterically demanding arsenic- and antimony precursors in which the bulky residues should stabilize a possible As=As or Sb=Sb double bond after subsequent reduction. ddpAl and ddpGa act as reducing agents as well as sterically demanding ligands, which allow sufficient kinetic stabilization of the dipnictenes. The formation of Dibismutenes by reactions between ddpGa and Bi(NEt2)3 and the bismuth alkoxides Bi(OR3)3 (R = OSO2CF3, C6F6) confirms this trend. In contrast, reactions of phosphorus halides PX3 (X = Cl, Br) resulted in gallium-disubstituted phosphines of the type [ddp(X)Ga]2PX2, in which ddpGa reacts with twofold insertion into PX bonds of PX3. In future investigations it would be interesting to explore the further reaction potential of the dipnictenes presented in this work. The formation of bicyclo[1.1.0]butane analogues 20 and 21 upon thermolysis reactions of 17 and 19 showed the great potential for the molecular construction of novel and larger antimony-containing clusters
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
Author Under Sail The Imagination of Jack London, 1893-1902
No full textIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Intro -- Title Page -- Copyright Page -- Dedication -- Contents -- Acknowledgments -- Introduction -- 1. Spirit Truth -- 2. From Absorption to Theatricality and Back Again -- 3. "I Will Build a New Present" -- 4. Sons as Authors -- 5. Fathers as Publishers -- 6. The Daughter as Author -- 7. Lovers as Authors -- 8. At Sea with the Family -- 9. Yellow News, Yellow Stories -- 10. The Return Home -- Notes -- Bibliography -- Index -- About Jay WilliamsIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Description based on publisher supplied metadata and other sources.Electronic reproduction. Ann Arbor, Michigan : ProQuest Ebook Central, YYYY. Available via World Wide Web. Access may be limited to ProQuest Ebook Central affiliated libraries
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