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Surface selective hydrogel grafting of ultrafiltration membranes using macromolecular initiators and the application to increase fouling resistance
No full textFouling ist eines der Hauptprobleme bei der Anwendung von Ultrafiltration in der Wasseraufbereitung. Die chemische Modifizierung bestehender Membranen mittels „grafting from“ ist eine lange bekannte Methode um die Foulingresistenz von Membranen zu erhöhen. Andererseits sind entsprechende Methoden häufig nicht wirtschaftlich, da sie entweder schwierig aufzubringen sind, oder die Membraneigenschaften zu stark beeinflussen. Das Ziel dieser Arbeit war es, eine Methode zu entwickeln welche sehr oberflächenselektiv und einfach anzuwenden ist. Dazu wurden neuartige makromolekulare Initiatorsysteme entwickelt, welche in einem ersten Schritt auf der Membranoberfläche adsorbierten. In einem zweiten Schritt wurde der Initiator verwendet um ein polymeres Hydogelnetzwerk auf der Membran aufwachsen zu lassen. Ein thermischer Initiator wurde durch polymeranaloge Modifizierung eines polystyrol-co-maleinsäureanhydrid Copolymers mit Cumyl- und ter.Butyl hydroperoxid oder einer azo-funktionalen Gruppe hergestellt. Ein redox Co-initiator wurde durch Copolymerisation von N,N-Dimethylaminoethyl methacrylate und Butylmethacrylat hergestellt. Beide Systeme wurden bezüglich ihrer kolloidalen Eigenschaften wie kritischer Mizellbildungskonzentration und kritischem Wassergehalt untersucht. Das Adsorptionsverhalten auf Modelloberflächen aus dichten Polyethersulfon (PES) filmen wurde mittels Oberflächenplasmonenresonanz, Quarzkristallmikrowaage und Ellipsometrie untersucht. Geeignete Bedingungen, welche zur Bildung einer Fest adsorbiterten Monolage führen konnten für alle Initiatorsysteme gefunden werden. Mittels In Situ Rheologie, wurde die Initiatoraktivität unterucht. Die redox Co-initiatoren zeigten eine hohe Initiatoraktivität. Bei den thermischen Initiatoren, zeigte der Azo basierte Initiator keine Aktivität, wogegen die Peroxid basierten Initiatoren bei 65 °C eine gute Leistung zeigten. Das zwitterionische [3-(methacryloylamino) propyl] dimethyl (3-sulfopropyl) ammonium hydroxid (SPP) wurde als Monomer zur Membranfunktionalisierung verwendet. N,N´-methylenebis(acrylamid) (MBAA) wurde als Vernetzer genutzt. Es konnte gezeigt warden, dass beide Initiatorsysteme generell geeignet sind um Membranen zu modifizieren. Aufgrund der besseren Anwendbarkeit, wurde der redox Co-initiator für weitere Studien verwendet. Der Effekt der Modifizierung auf die Oberflächenchemie wurde mittels Kontaktwinkel, Zeta Potential, Röntgenphotoelektronenspektroskopie und SIMS-mapping untersucht. Veränderungen in der elementaren Zusammensetzung der Oberfläche zeigten eine erfolgreiche Modifizierung.
Fouling tests wurden mit Inge Multibore® PES Kapillarmembranen und Flachmembranen mit ähnlichen Eigenschaften durchgeführt. Tests mit Rinderserum Albumin zeigten eine erhöhte Resistenz gegen Proteinfouling unter statischen und Filtrationsbedingungen. Tests mit Extrakten aus einem Membranbioreaktor (EPS und SMP) zeigten ebenfalls eine erhöhte Foulingresistenz. Filtrationsversuche mit einem Extrakt aus Blumenerde zeigten erhöhte Foulingresistenz sowie einen erhöhten TOC rückhalt. Darüberhinaus konnte in verschiedenen Versuchen gezeigt werden, dass die modifizierten Membranen eine hohe chemische und mechanische Stabilität aufweisen. Letztendlich wurde die Modifizierungsmethode in Moulen im Technikumsmaßstab angewendet. Insbesondere die leichte Anwendbarkeit auch in fertigen Membranmodulen, lassen eine Weiterentwicklung der gezeigten Methoden Sinnvoll erscheinen.Fouling is a major challenge when applying ultrafiltration in water treatment. Membrane grafting is a long known possibility to increase the inherent fouling resistance of polymeric ultrafiltration membranes. On the other hand, many available techniques are not widely established, because they either strongly influence the membrane performance or are not easy to apply and thus not feasible. The aim of the work presented here, was to establish a new grafting technique that is surface selective and easy to apply in ready to use membrane modules. This goal was to be achieved via a new macromolecular initiator that is adsorbed to the membrane selective layer in a first step. Due to its high molecular weight, the initiator is completely rejected by the membrane. In the second step, the initiator activity is used to graft a zwitterionic hydrogel on the membrane surface. A copolymer of butyl methacrylate as adhesive group and N,N-dimethylaminoethyl methacrylate as redox co-initiator was synthesized with varying ratios of both monomers. A thermal macroinitiator was synthesized by modifying a commercial polystyrene-co-maleic anhydride copolymer with a new azo functional group as well as the organic hydroperoxides cumyl- and tert. butylhydroperoxide. The initiator systems were characterized regarding their behaviour in solvent mixtures by measurements of critical water content and critical micelle concentration. The adsorptive behaviour to polyethersulfone (PES) model surfaces was surveyed via surface plasmon resonance, quartz crystal microbalance and ellipsometry. Suitable conditions leading to a strongly adsorbed monolayer were found for all systems. The initiator activity was surveyed by in situ rheology. A high activity was found for the redox co-initiator system. No activity was found for the azo modified copolymer, while the hydroperoxide based thermal initiators showed a good performance at 65 °C. Zwitterionic [3-(methacryloylamino) propyl] dimethyl (3-sulfopropyl) ammonium hydroxide (SPP) was used as the monomer for membrane modification and N,N´-methylenebis(acrylamide) (MBAA) was used as a cross-linker. It could be proven that both initiator systems are generally suitable for surface selective membrane modification. Since the redox co-initiator caused less unspecific polymerization in the membrane support, this system was used for further studies focusing on membrane performance. The effect of grafting on the membrane surface chemistry was surveyed on PES flat sheet membranes using contact angle, zeta potential, X-ray photospectroscopy and SIMS-mapping. It was found that the modification leads to a more neutral surface charge and higher hydrophilicity. Changes in the elemental composition of the surface indicated that these changes are correlated to successful surface modification.
Fouling tests were performed using Inge Multibore® PES capillary membranes as well as flat sheet samples produced by BASF with similar properties like the Multibore®. The capillaries were potted in filtration modules of different sizes. Fouling tests with bovine serum albumin revealed an increased resistance towards protein fouling in static adsorption tests and during filtration. Tests with extracts from membrane bioreactors (EPS and SMP) showed an increased fouling resistance for the modified membranes. Filtration tests with flower soil extract showed improved anti fouling properties and an increase in TOC rejection due to the modification. Furthermore a good chemical and mechanical stability of the grafting layer could be proven by multiple tests applying or simulating chemical enhanced back wash procedures. Finally the modification was applied in pilot scale modules which are currently surveyed in a long term test.
The developed macromolecular redox co-initiator is well applicable and can be optimized for other membrane types and materials in future work. Also it may be used to graft other polymers on membranes to further improve fouling resistance or other desired properties like MWCO or biocompatibility. Especially the good applicability in membrane modules and the high stability of the grafted layers are expected to make the presented method a versatile and feasible alternative for established techniques. Future work should focus on optimization of the grafting conditions and evaluation of other hydrogel systems to improve the benefits of the grafting
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
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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