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Magnetophoresis Of Poly (SODIUM 4-STYRENESULFONATE) Fe3O4 Clusters The Influence of Colloidal Stability
Get PDFKajian ini didedikasikan untuk mendedahkan pengaruh kestabilan berkoloid
terhadap magnetoforesis zarah-zarah Fe3O4. Pertama sekali, kestabilan berkoloid
Fe3O4 terdedah telah berjaya dipertingkatkan selepas permukaanya disalut dengan
polimer anionik yang kuat, poli(natrium 4-stirenasulfonat) berberat molekul 70K Da
(PSS 70K), melalui teknik pascasalutan diaruh oleh elektrostatik yang dilakukan pada
pH ~ 3.50. Peningkatan kestabilan berkoloid yang dicapai oleh kelompok-kelompok
PSS 70K/Fe3O4 tersebut sebahagian besarnya disumbangkan daripada tolakan
elektrostatik dan tolakan sterik yang masing-masingnya mengatasi tarikan dwikutubdwikutub
magnet apabila jarak antara zarah adalah < 97 nm dan < 50 nm. Namun
begitu, kajian permisahan magnet menunjukkan bahawa semakin stabil berkoloid
Fe3O4 itu, semakin sukar untuk memisahkannya dengan magnet. Dengan mengesani
profil magnetoforesis bawah kecerunan medan magnet dengan purata magnitud 40.55
T/m, didapati bahawa Fe3O4 terdedah mencapai 100 % permisahan dalam masa 8 minit;
manakala kelompok-kelompok PSS 70K/ Fe3O4 tidak dapat dipisahkan sepenuhya
walaupun masa bagi permisahan magnet tersebut dilanjutkan sehingga satu jam.
Dalam erti kata yang lain, salutan polimer yang pada mulanya digunakan untuk
menstabilkan Fe3O4 itu secara elektrosterik justerunya menjejaskan kebersambutan
mereka terhadap magnet. Berlainan daripada Fe3O4 terdedah yang menjalani
magnetoforesis secara berkerjasama, didapati bahawa kelompok-kelompok PSS
70K/Fe3O4 mengalami magnetoforesis berdasarkan pemeringkatan mengikut saiz di
mana pemisahan magnetnya dikawal oleh kehadiran taburan saiz hidrodinamik di
dalam ampaian tersebut. Selain daripada itu, kajian mikroskopik seterusnya
mendedahkan perbezaan di antara kedua-dua entiti di mana kelompok-kelompok PSS
70K/Fe3O4 cenderung untuk terhala sesama sendiri menjadi struktur seperti benang;
manakala Fe3O4 terdedah cenderung untuk agregat sesama sendiri menjadi struktur
fraktal yang berpelbagai dimensi. Pendekatan perhimpunan pengantara elektrostatik
yang mudah telah dicadangkan dalam kajian ini untuk menghasilkan kelompokkelompok
PSS 70K/Fe3O4 yang berpelbagai saiz (~ 200 nm hingga ~ 700 nm ). Di sini,
didapati bahawa kelompok-kelompok PSS 70K/Fe3O4 dengan purata saiz kelompok
459 nm bukan sahaja mempunyai kestabilan berkoloid yang baik, malahan
menawarkan kebolehpisahan magnet yang tinggi (> 98 % kecekapan pemisahan
dicapai apabila didedahkan kepada kecerunan medan magnet yang sama untuk 5 minit
sahaja). Penemuan ini menunjukkan bahawa memanipulasi saiz kelompok bagi
kelompok-kelompok PSS 70K/Fe3O4 boleh digunakan sebagai penyelesaian untuk
kebimbangan keseimbangan antara peningkatan kestabilan berkoloid dan
kebolehpisahan magnet. Dalam bahagian akhir kajian ini, kestabilan berkoloid bagi
kelompok-kelompok PSS 70K/Fe3O4 didapati telah merosot selepas penambahan ionion
logam (e.g., Ag+, Cu2+, Cr3+, Ca2+, Mg2+). Keputusan menunjukkan bahawa
kepekatan kation logam memainkan peranan yang lebih penting daripada kekuatan ion
yang lazimnya dipercayai dalam meningkatkan proses pengagregatan tersebut. Di
samping itu, dengan kehadiran ion Cu2+, bahan-bahan organic terlarut seperti asid
humik dan natrium alginat didapati membentuk kompleks dengan kelompokkelompok
PSS 70K/Fe3O4. Pembentukan kompleks ini kemudiannya juga akan
mempengaruhi kestabilan berkoloid dan justerusnya kelakuan magnetoforesis
kelompok-kelompok PSS 70K/Fe3O4.
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The present work is dedicated to reveal the influence of colloidal stability
towards magnetophoresis of Fe3O4 particles. First of all, colloidal stability of bare
Fe3O4 was successfully enhanced after surface coating with a strong anionic polymer,
poly(sodium 4-styrenesulfonate) of molecular weight 70K Da (PSS 70K), through
electrostatic-induced post-coating technique conducted at pH ~3.50. Enhanced
colloidal stability attained by the resultant PSS 70K/Fe3O4 clusters is mainly
contributed from the electrostatic and the steric repulsion, which overwhelm the
magnetic dipole-dipole attraction, when the interparticle distance is < 97 nm and < 50
nm, respectively. However, magnetic separation study showed that the more
colloidally stable the Fe3O4 is, the harder it is to be magnetically separated. By
carefully tracking on the magnetophoresis profiles under magnetic field gradient of
average magnitude 40.55 T/m, it was found that bare Fe3O4 attained ~ 100 %
separation within 8 minutes; while there was no complete separation for PSS
70K/Fe3O4 clusters even the magnetic separation time was extended to 1 hour. In
another words, the polymer coating that was initially employed to electrosterically
stabilize the Fe3O4 in turn compromises their magnetic responsiveness. Unlike the bare
Fe3O4 which undergo a typical cooperative magnetophoresis, it was found that the PSS
70K/Fe3O4 clusters experienced a size-fractionation based magnetophoresis in which
the magnetic separation was controlled by the presence of distribution of
hydrodynamic sizes in the suspension. Besides that, microscopic study further
revealed the differences between both entities in which PSS 70K/Fe3O4 clusters tend
to self-oriented into thread-like structures; while bare Fe3O4 tend to self-aggregate into
fractal structures of various dimensions. A simple electrostatic-mediated assembly
approach was proposed in this study to produce PSS 70K/Fe3O4 clusters of various
sizes (~200 nm up to ~ 700 nm). Here, it was found that PSS 70K/Fe3O4 clusters of
average cluster size 459 nm not only possess good colloidal stability, but also offer
high magnetic separability (> 98 % separation efficiency was attained when exposed
to the same magnetic field gradient for just 5 minutes). This finding indicates that
manipulating the cluster sizes of the PSS 70K/Fe3O4 clusters can be used as the
solution for the trade-off concern between enhanced colloidal stability and magnetic
separability. In the last part of this study, it was revealed that the colloidal stability of
PSS 70K/Fe3O4 clusters being deteriorated after addition of metal ions (e.g., Ag+, Cu2+,
Cr3+, Ca2+, Mg2+). Results showed that it is the concentration of the metal cation,
instead of the conventionally believed ionic strength, plays a more decisive role in
enhancing the aggregation process. In addition, with the presence of Cu2+ ion, dissolve
organic matters such as humic acid and sodium alginate was found to form complexes
with the PSS 70K/Fe3O4 clusters. This formation of complexes can later on influence
the colloidal stability and thus magnetophoresis behavior of the PSS 70K/Fe3O4
clusters
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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