1,720,956 research outputs found
Scaffolding with Nonalternant Hydrocarbons: From Covalent Organic Frameworks to Strained Macrocycles
No full textAufgrund ihrer einzigartigen elektronischen Struktur besitzen nicht-alternierende Kohlenwasserstoffe faszinierende optoelektronische Eigenschaften. Viele zeigen kleine Bandlücken, niedrige LUMO-Niveaus, permanente Dipolmomente oder Redoxaktivität. Dibenzopentalen und Azulen vereinen interessante Eigenschaften mit hoher Stabilität. Trotz ihres Potenzials bleiben ihre Anwendungen in funktionellen Materialien begrenzt, was oft an synthetischen Herausforderungen und Stabilitätsproblemen liegt. Kovalent-organische Gerüstverbindungen (COFs) bieten eine Plattform, um molekulare Eigenschaften auf poröse, geordnete Materialien zu übertragen. Diese Arbeit untersucht nicht-alternierende Kohlenwasserstoffe im Kontext organischer Materialien – von der Synthese funktionalisierter Bausteine bis zur Untersuchung ihrer Eigenschaften in Molekülen und größeren Strukturen. Für COFs auf Basis nicht-alternierender Kohlenwasserstoffe wurde die Synthesestrategie erweitert. Benzophenonimine ersetzen Amine in der Imin-Verknüpfung und ermöglichen durch ihre Funktionalisierbarkeit die Herstellung instabiler COF-Monomere. Drei Dibenzopentalen-basierte Bausteine wurden mit dreiwertigen Aldehyden zu antiaromatischen COFs und POPs verknüpft. Diese Materialien sind porös, kristallin und im dotierten Zustand photoleitend. Die Redoxeigenschaften wurden auf das Bulk-Material übertragen, und Dibenzopentalen-COFs wurden erfolgreich als Kathoden in Li-organischen Batterien eingesetzt. Azulen wurde entlang der Rotationsachse funktionalisiert, um es als Baustein für größere Strukturen zu nutzen. Eine C–H-Aktivierung mit Thianthren-S-oxid ermöglichte regioselektive Thianthrenierung, bestätigt durch DFT-Berechnungen. Eine lineare Funktionalisierung führte zur Synthese eines gespannten Azulen-Makrozyklus sowie eines linearen Linkers für COFs. DFT-Berechnungen zeigen, dass Biegung die optischen und elektronischen Eigenschaften stark beeinflusst. Erste Ergebnisse deuten auf vielversprechendes Potenzial Azulen-basierter COFs als Photokatalysatoren für Wasserstoffentwicklung hin.By virtue of their unique electronic structure, nonalternant hydrocarbons possess intriguing optoelectronic properties. Many show small band gaps, low LUMO levels, permanent dipole moments or redox-activity. Dibenzopentalene and azulene are two such hydrocarbons combining interesting properties with stability. Despite their advantages, their use in functional materials remains limited, often due to synthetic challenges and stability issues. Covalent organic frameworks (COFs) offer a platform to translate molecular properties into porous, ordered materials. This thesis explores nonalternant hydrocarbons in the context of organic materials, including synthesis of functionalized building blocks, their integration into architectures, and the study of their properties. To construct COFs from nonalternant hydrocarbons, synthetic methods were expanded. In imine-linked COFs, benzophenone imines replace amines and allow for attachment of diverse functional groups, enabling otherwise unstable COF monomers. Three dibenzopentalene-based building blocks were linked with trivalent aldehydes to form antiaromatic DBP-based COFs and POPs. These materials are porous, crystalline, and photoconductive when doped. Their redox properties translate to bulk materials, and DBP-COFs were used as cathodes in Li-organic batteries. Azulene was linearly functionalized along its rotational axis to serve as a versatile building block. Functionalization at the 2,6-positions, although challenging, allows for optimal electronic delocalization. A site-selective C–H activation using thianthrene-S-oxide was developed. Thianthrenation was rationalized via DFT and enabled bis-functionalization for material precursors. A strained azulene macrocycle and a linear linker were synthesized. DFT calculations showed strong influence of bending on optical and electronic properties. A size-selective, 6-membered azulene macrocycle was formed via a triangular Au(I)-metallacycle, though with low stability. Preliminary data suggest azulene-based COFs have potential as photocatalysts for hydrogen evolution.
Constructing functional materials from nonalternant hydrocarbons remains a challenge. Further development in small molecule and materials synthesis is essential for advancing this field
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
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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