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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
Synthesis and reactivity of subvalent zinc compounds
No full textIn der vorliegenden Dissertation konnte gezeigt werden, dass niedervalente Zinkverbindungen zur Durchführung von Redoxreaktionen fähig sind und den Vorteil besitzen, dass die Reaktionen bereits bei sehr milden Bedingungen durchgeführt werden können und die Zn(I)-Verbindungen sehr selektiv gegenüber organischen Gruppen sind. Des Weiteren wurden Syntheserouten für bereits bekannte Verbindungen optimiert bzw. durch neue Synthesewege ersetzt.
Die bereits bekannte Verbindung Dippnacnac2Zn2 konnte nicht über Cp*H-Eliminierung synthetisiert werden, da die Azidität des Liganden DippnacnacH nicht hoch genug war, um den Cp*-Rest zu protonieren. Allerdings konnte dieses Problem durch Salzeliminierung von Cp*K umgangen werden und Dippnacnac2Zn2 wurde mit höheren Ausbeuten dargestellt (Schema 73). Offenkundig ist die Eliminierung von Cp*K energetisch bevorzugt, so dass dieser Reaktionsweg bei der Synthese bislang unbekannter Zn(I)-Verbindungen besonders geeignet erscheint.
Schema 73: Neue Syntheseroute von Dippnacnac2Zn2.
Mittels Cp*H- bzw. Cp*K-Eliminierung konnten die neuen heteroleptischen niedervalenten Zinkverbindungen 8 und 9 synthetisiert werden.
Bei Reaktionen von Decamethyldizinkocen mit sauren Metallhydriden (Cp2ReH, CpCr(CO)3H, CpMo(CO)3H) wurde stets eine Disproportionierung beobachtet, die auf die Bildung eines instabilen Zwischenproduktes hinweist (Schema 74).
Schema 74: Disproportionierungsreaktion von Cp*2Zn2 mit Cp2ReH.
Durch die Reaktion von Decamethyldizinkocen mit etherischer HCl bzw. mit dem dmap-Hydrochlorid wurde möglicherweise Zn2Cl2 bzw. das basenstabilisierte Addukt 10 synthetisiert (Schema 75).
Schema 75: Synthese von 10.
Es wurden verschiedene Analysemethoden angewandt, um 10 eindeutig nachzuweisen, was allerdings nicht gelungen ist. Die Synthese von Zn2Cl2 würde die Chemie der niedervalenten Zinkverbindungen enorm weiter bringen, da dadurch weitere vielversprechende Reaktionsmöglichkeiten zustande kommen könnten.
Cyclovoltametriemessungen von Zn(I)-Verbindungen haben gezeigt, dass Redox-reaktionen mit niedervalenten Zinkverbindungen prinzipiell möglich sind. Daraufhin wurden Reaktionen von Mesnacnac2Zn2 mit unterschiedlichen organischen Molekülen durchgeführt. Bei Reaktionen mit Gruppe-14-Aziden wurden zwei Reaktionsprodukte beobachtet. Mit Me3SiN3 und Me3SnN3 erhielt man unter M-M-Kopplung das bereits bekannte dimere Zinkazid [MesnacnacZn-N3]2 (Schema 76).
Schema 76: Synthese von [MesnacnacZn-N3]2.
Im Gegensatz dazu wurde mit Ph-N3 erstmals der Zink-Hexazenkomplex 12 synthetisiert. Von dieser Verbindung konnten Kristalle erhalten werden, mit denen die Molekülstruktur mittels Röntgenstrukturanalyse bestimmt werden konnte (Abbildung 27).
Abbildung 27: Kristallstruktur von 12.
12 ist der erste strukturell charakterisierte Zink-Hexazenkomplex. Im Rahmen dieser Arbeit wurden Untersuchungen zur Reaktivität von 12 durchgeführt. 12 reagiert mit AlMe3, ZnMe2 und MeLi unter Freisetzung von MesnacnacZnMe bzw. MesnacnacLi und Bildung der heteroleptischen bzw. heterobimetallischen Hexazenkomplexe. Die Li-Hexazenkomplexe wurden mit Metallchloridkomplexen unter LiCl-Eliminierung zu Metallhexazenkomplexen umgesetzt (Schema 77).
Schema 77: Reaktionsschema der Hexazenkomplexe.
Die Synthese der Lithium-Hexazenkomplexe stellt die Grundlage zur Eingliederung weiterer Metalle und Bildung neuartiger Hexazenkomplexe unter sehr milden Bedingungen dar. Gegebenenfalls können diese Komplexe als Precursoren für Metallnitridsynthese verwendet werden.
Mit elementaren Chalkogenen, wie Selen und Tellur, wurden keine Reaktionen beobachtet. Mit elementarem Schwefel wurde nicht die erwartete Insertionsreaktion in die Zn-Zn-Bindung beobachtet, sondern eine Oxidation des γ-C-Atom durch den Schwefel. Von dieser Verbindung konnten Kristalle erhalten werden, mit denen die Molekülstruktur mittels Röntgenstrukturanalyse bestimmt werden konnte (Abbildung 28).
Abbildung 28: Kristallstruktur von 13.
Durch Reaktionen von Mesnacnac2Zn2 mit Diphenyl-Dichalkogeniden konnten die bislang unbekannten dimeren Zinkchalkogenid [MesnacnacZn-SePh]2 16, [MesnacnacZn-TePh]2 17 und [MesnacnacZn-SPh]2 18 synthetisiert werden (Schema 78).
Schema 78: Reaktionen von Mesnacnac2Zn2 mit Diphenyl-Dichalkogeniden.
Mit diesen Umsetzungen konnte im Rahmen dieser Doktorarbeit eine bislang völlig unbekannte Reaktivität von Zn(I)-Verbindungen gezeigt werden. Durch Oxidation der Zinkatome und Reduktion der Chalkogenatome konnte 16 synthetisiert und mittels Röntgenstrukturanalyse strukturell charakterisiert werden (Abbildung 29).
Abbildung 29: Kristallstruktur von 16.
Im Rahmen dieser Arbeit wurden Untersuchungen zur Reaktivität von 16 sowie 17 durchgeführt, bei denen 16 und 17 mit H-aciden Substanzen, wie EtOH und H2O, und auch O2 umgesetzt wurden. Diese Reaktionen könnte man auf die Gruppe-14 Elemente aus-weiten und niedervalente Zinkverbindungen mit z.B. Digermanen oder auch Distannanen umsetzen, um die jeweiligen Zinkgermide bzw. Zinkstannide zu erhalten. Möglicherweise könnte man auf diesem Weg neue Precursor für die Nanopartikelsynthese erhalten oder auch neuartige Clusterverbindungen synthetisieren.
Die Umsetzungen mit H-aziden Substanzen H2O/EtOH verläuft unter Abspaltung von PhTe-H bzw. PhSe-H und Bildung von [MesnacnacZn-OH]2 19 und [MesnacnacZn-OEt]2 20. 19 und 20 wurden mittels Röntgenstrukturanalyse strukturell charakterisiert (Abbildung 30).
Abbildung 30: Kristallstrukturen von 19 (links) und 20 (rechts).
Mit elementarem Sauerstoff konnten die metallierten chalkogenigen Säuren [MesnacnacZn-SePh(O)2]2 21 und [MesnacnacZn-TePh(O)2]2 22 synthetisiert und strukturell charakterisiert werden (Abbildung 31).
Abbildung 31: Kristallstrukturen von 21 (rechts) und 22 (links).
Dies ist ein sehr seltenes Beispiel einer metallierten tellurigen Säure, die strukturell charakterisiert werden konnte. Alle Versuche, ausgehend von 21 die freie tellurige Säure darzustellen, scheiterten.
Setzt man 17 mit elementarem Schwefel um, entsteht nicht die erwartete metallierte tellurige Thiosäure, sondern es wird Te2Ph2 abgespalten und man erhält 13 (Schema 79).
Schema 79: Reaktion von 17 mit elementarem Schwefel zu 13.This PhD thesis proved, that subvalent zinc compounds can be used in redox reactions. They have the advantage, that these reactions can already be performed under mild conditions and the Zn(I) compounds have a high selectivity against organic groups. Furthermore, the synthesis of known Zn(I) compounds were optimized.
Dippnacnac2Zn2 could not be synthesized by Cp*H elimination, because the basicity of the DippnacnacH ligand was not high enough to protonate the Cp* group. In contrast the salt elimination of Cp*K gave Dippnacnac2Zn2 in high yields (Scheme 1).
Scheme 1: New synthesis route of Dippnacnac2Zn2.
Moreover, the new heteroleptic Zn(I) compounds 8 and 9 were synthesized by Cp*H respectively Cp*K elimination.
Reactions of decamethyldizincocen with acidic metall hydrids (Cp2ReH, CpCr(CO)3H, CpMo(CO)3H) occurred with disproportionation, which is attributed to the unstable product (Scheme 2).
Scheme 2: Disproportionation reaction of Cp*2Zn2 with Cp2ReH.
The reaction of decamethyldizincocen with etheric HCl as well as with the HCl-dmap adduct yielded Zn2Cl2 or the basestabilized adduct 10 (Scheme 3).
Scheme 3: Synthesis of 10.
Different analytical methods were used to verify the formation of 10, but its formation is still in question.
Cyclovoltametric measurements of Zn(I) compounds demonstrated, that redox reactions with zinc(I) compounds are in principle possible. Therefore, reactions of Mesnacnac2Zn2 with different organic molecules were investigated.
Reactions of 6 with group 14 azides yielded two products. The reaction of 2 eq of the ionic azides Me3MN3 (M = Si, Sn) with Mesnacnac2Zn2 yielded hexamethyldisilane and -distannane Me6M2 as well as the previously reported zinc azido complex [MesnacnacZnN3]2 (Scheme 4).
Scheme 4: Synthesis of [MesnacnacZn-N3]2.
In contrast, reactions with covalent azides, such as Ph-N3 resulted in the formation of the first zinc hexazene complex 12. The solid state structure of 12 was determined by single crystal x-ray diffraction (Figure 1).
Figure 1: Molecule structure of 12.
12 is the first strucurally characterized zinc hexazene complex. In order to investigate the reactivity of 12, the hexazene complex was treated with AlMe3, ZnMe2 and MeLi. These reactions yield MesnacnacZnMe and MesnacnacLi, as well as several hetero bimetallic hexazene complexes. The lithium hexazene complexes react with metalchloride complexes to yield in hexazene complexes (Scheme 5).
Scheme 5: Reaction scheme of the hexazene complexes.
With the synthesis of the lithium hexazene complexes it is possible to insert every metal as metal halogenide and constitute new hexazene complexes to get very nitrogenrich compounds under mild conditions.
With elemental chalkogenes, selenium and tellurium, no reactions were observed at all. With elemental sulfur the expected insertion of sulfur did not proceed, but an oxidation of the backbone carbonatom was observed. The structure of 13 was determined by single crystal x-ray diffraction (Figure 2).
Figure 2: Molecule structure of 13.
The reactions of Mesnacnac2Zn2 with diphenyl dichalkogenides yielded zincchalkogenide dimers [MesnacnacZn-SePh]2 16, [MesnacnacZn-TePh]2 17 and [MesnacnacZn-SPh]2 18 (Scheme 6).
Scheme 6: Reactions of Mesnacnac2Zn2 with Diphenyl-Dichalkogenides.
In the framework of this thesis a completely new reactivity behaviour of zinc(I) compounds could be demonstrated with these reactions. By oxidation of the zinc atoms and reduction of the chalkogenatoms 16 was synthesized and structurally characterized via single crystal x-ray diffraction (Figure 3).
Figure 3: Molecule structure of 16.
16 and 17 were treated with H-acidic substrates, like EtOH and H2O, and elemental oxygen.
The reactions of 16 and 17 with H-acidic substrates occurred with elimination of PhTe-H and PhSe-H, respectively, as shown in the NMR spectroskopy, and subsequent formation of [MesnacnacZn-OH]2 19 and [MesnacnacZn-OEt]2 20, which were structurally characterized via single crystal x-ray diffraction (Figure 4).
Figure 4: Molecule structure of 19 (left) and 20 (right).
With elemental oxygen the metalated chalkogenic acids [MesnacnacZn-SePh(O)2]2 21 und [MesnacnacZn-TePh(O)2]2 22 were synthesized and structurally characterized (Figure 5).
Figure 5: Molecule structure of 21 (right) and 22 (left).
22 represents a rare example of a metalated tellurinic acid (RTe(O)OH), which is structurally characterized. Experiments to get the protonated form of the tellurinic acid failed.
Treating 17 with elemental sulfur did not yield the expected metalated tellurinic thioacid, but complex 13 and Te2Ph2 were separated (Scheme 7).
Scheme 7: Reaction of 17 with elemental sulfur to 13
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
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
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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