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Carbon-based materials for sustainable electrochemical hydrogenations
No full textThe chemical manufacturing sector is one of the most important industries of modern society. However, the processes currently employed for chemical production impact the environment considerably, accounting for a significant part of greenhouse gas emissions and energy consumption. Hydrogenations are a paramount class of reactions for the production of plastics, pharmaceuticals and food, but they require elevated temperatures, pressurized hydrogen and (noble) metal catalysts. In our continuous effort to decarbonize industrial activity, electrochemistry rises as a sustainable alternative to carry out these reactions, under ambient conditions. Nonetheless, most electrochemical processes still rely on (noble) metals and/or (per)fluorinated binder materials, thus posing sustainability limitations on their widespread employment. This dissertation aims to employ carbon-based materials as sustainable alternatives for electrochemical hydrogenations (ECHs) and assess their structure-performance relationship. The materials are also benchmarked against counterparts, either commercial, or found in literature, to elucidate their influence on the reaction and evaluate their performance.
Chapter 2 focuses on the use of N-doped carbons as hydrogenation electrocatalysts. By utilizing a salt-melt templated synthesis, nanoporous N-doped carbons are produced and employed for the electrochemical hydrogenation of maleic to succinic acid, the latter being a valuable commodity chemical. Mechanistic investigations indicate that N-doping induces specific electrode-organics adsorptive interactions, and the hydrogenation proceeds with a mechanism resembling that of metals. Additionally, the obtained yields are compared to other heterogeneous catalytic processes that utilize metals for maleic acid hydrogenation, showing that electrochemical hydrogenations can be conducted in ambient and metal-free conditions, without compromising the yield of the reaction.
In Chapter 3 non-noble metal Single Atom Catalysts (SACs) were synthesized, bearing Fe, Ni, or Co atoms, anchored on a N-doped carbon shell. The SACs were utilized for the semi-ECH of alkyne(di)ols to alkene(di)ols, exhibiting high chemoselectivity over the competing full hydrogenation to alkane(di)ols. Moreover, they exhibited distinct stereoselectivities depending on the metal, allowing for the tunable synthesis of cis- or trans-alkenediols. Finally, the SACs were compared to their nanoparticle counterparts, which did not exhibit any metal-dependent stereoselectivity. This comparison indicates that the unique reactivities discussed stem from both the metal active sites and their atomic coordination.
Chapter 4 examines the use of poly(ionic liquids) (PILs) as binders for ECH. The PIL bound electrodes outperformed electrodes using commercial fluorinated binders for the ECH of benzaldehyde to benzyl alcohol. This performance enhancement was investigated by mechanistic studies, as well as in-situ local pH electrochemical measurements. It is shown that the PIL binders’ structure and charge massively influence the electrode’s microenvironment during polarization, due to electrostatic and chemical effects. These factors enhance both the yield and Faradaic efficiency of the reaction. Finally, the versatility of PILs enhancement is assessed for further ECH reactions, over a broad range of more than 12 pH units.Die chemische Industrie ist einer der wichtigsten Wirtschaftszweige der heutigen Gesellschaft. Jedoch haben die aktuell eingesetzten Verfahren der chemischen Industrie erhebliche Auswirkungen auf die Umwelt, aufgrund der dabei entstehenden Treibhausgasemissionen und des hohen Energieverbrauchs. Hydrierungen sind für die Herstellung von Kunststoffen, Arznei- und Lebensmitteln von entscheidender Bedeutung, erfordern jedoch hohe Temperaturen, hohe Wasserstoffdrücke und (Edel)Metallkatalysatoren. In unserem kontinuierlichen Bestreben, industrielle Aktivitäten zu dekarbonisieren, bietet die Elektrochemie eine nachhaltige Alternative, um diese Reaktionen unter Umgebungsbedingungen durchzuführen. Dennoch basieren die meisten elektrochemischen Prozesse nach wie vor auf (Edel)Metallen und/oder fluorierten Bindemitteln, was ihre breite Anwendung aus Nachhaltigkeitsgründen einschränkt. Ziel dieser Dissertation ist es, kohlenstoffbasierte Materialien als nachhaltige Alternativen für die elektrochemische Hydrierung (ECHs) einzusetzen und deren Struktur-Leistungs-Beziehung zu bewerten. Die Materialien werden auch mit kommerziellen oder in der Literatur beschriebenen Gegenstücken verglichen, um ihren Einfluss auf die Reaktion aufzuklären und ihre Leistung zu bewerten.
Kapitel 2 fokussiert sich auf die Verwendung von N-dotierten Kohlenstoffen als Elektrokatalysatoren für die Hydrierung. Durch die Verwendung einer Salzschmelze-basierten Synthese werden nanoporöse N-dotierte Kohlenstoffe hergestellt und für die elektrochemische Hydrierung von Malein- zu Bernsteinsäure eingesetzt, wobei letztere ein wertvoller chemischer Rohstoff ist. Mechanistische Untersuchungen zeigen, dass die N-Dotierung spezifische adsorptive Wechselwirkungen zwischen Elektrode und organischen Verbindungen induziert und die Hydrierung nach einem Mechanismus abläuft, der dem von Metallen ähnelt. Darüber hinaus werden die erzielten Ausbeuten mit anderen heterogenen katalytischen Verfahren verglichen, bei denen Metalle für die Hydrierung von Maleinsäure verwendet werden. Dabei zeigt sich, dass elektrochemische Hydrierungen unter Umgebungsbedingungen und ohne Metalle durchgeführt werden können, ohne die Ausbeute der Reaktion zu beeinträchtigen.
In Kapitel 3 wurden nicht-edle Metall-Einzelatomkatalysatoren (SACs) synthetisiert, welche aus aus Fe-, Ni- oder Co-Atome bestehen und auf einer N-dotierten Kohlenstoffhülle verankert waren. Die SACs wurden für die semi-ECH von Alkin(di)olen zu Alken(di)olen verwendet und zeigten eine hohe Chemoselektivität gegenüber der konkurrierenden vollständigen Hydrierung zu Alkan(di)olen. Darüber hinaus zeigten sie je nach Metall unterschiedliche Stereoselektivitäten, was eine anpassbare Synthese von cis- oder trans-Alkendiolen ermöglichte. Schließlich wurden die SACs mit ihren Nanopartikel-Pendants verglichen, die keine metallabhängige Stereoselektivität aufwiesen. Dieser Vergleich zeigt, dass die diskutierten einzigartigen Reaktivitäten sowohl auf die aktiven Metallstellen als auch auf ihre atomare Koordination zurückzuführen sind.
Kapitel 4 behandelt die Verwendung von Poly(ionischen Flüssigkeiten) (PILs) als Bindemittel für ECH. Die mit PIL gebundenen Elektroden übertrafen Elektroden, die handelsübliche fluorierte Bindemittel für die ECH von Benzaldehyd zu Benzylalkohol verwendeten. Diese Leistungssteigerung wurde durch mechanistische Untersuchungen sowie durch lokale pH-elektrochemische Messungen vor Ort untersucht. Es zeigt sich, dass die Struktur und Ladung der PIL-Bindemittel aufgrund elektrostatischer und chemischer Effekte einen signifikanten Einfluss auf die Mikroumgebung der Elektrode während der Polarisation haben. Diese Faktoren verbessern sowohl die Ausbeute als auch die Faraday-Effizienz der Reaktion. Letztlich wird die Vielseitigkeit der PIL-Verbesserung für weitere ECH-Reaktionen über einen breiten Bereich von mehr als 12 pH-Einheiten bewertet
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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