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The Electrochemical and Spectral Characteristics of N, N’-di-p-Anisylamino-Substitued Phenyl Derivatives and Their Effects on Chemiluminescence
No full text透過電化學、光譜電化學及理論計算，對所合成的三苯胺衍生物進行研究，期望了解取代基效應對氧化電位、光譜性質、動力學及活化能等物化性質所造成的影響。當取代基提供電子能力越強，氧化反應所需的電位越低。在光譜電化學的研究中，這些化合物在中性態吸收峰及正一價陽離子自由基的最大吸收峰，均為紅位移。但是在二價陽離子的光譜位置上，則沒有明顯的變化。將化合物1至6的中性態及正一價陽離子自由基的最大吸收峰的波數對Hammet常數做圖，均可以得到線性關係。
在動力學的實驗裡，我們研究化合物1及化合物6以正一價陽離子自由基的特性峰之消長為計算第一階段（k1及k2）及第二階段氧化過程反應速率常數（k-1及k-2）的依據。從log k對Eappl..作圖發現，化合物1的第一階段氧化較快；但第二階段的氧化反應則為化合物6較快。
透過理論計算了解三苯胺在氧化過程中電子轉移情形及分子結構變化，我們發現無論是化合物1或6，在中性態時，中心氮原子及接在苯環上的甲氧基的密度最大。對化合物1而言，從中性態至正一價陽離子自由基的過程中，氮及甲氧基團的電子密度減少，苯環上的密度卻增加，透過苯環的共振，氧化過程中，甲氧基團會傳遞電子至苯環上。從1˙＋至12+的過程，氮原子幾乎沒有失去電子，電子則由苯環及三個甲氧基團提供。從化合物結構來看，隨著氧化的進行，雙面角角度越來越小，表示共平面的情形持續增加，分子共振越明顯。
化合物6由中性態至正一價陽離子自由基的過程中，電子轉移如同化合物1一般，反而是接上硝基的苯環，則因具有強去活化的傾向，使得電子往nitro-phenyl基團方向移動。而化合物6的C-N-nitrophenyl在氧化的過程中，其鍵長增加，雙面角角度也增大。Nitrophenyl基和NCCC的共平面變差了，且隨著氧化持續發生，和C-N-anisyl的結構差異越來越大。
我們將化合物1-6應用於光化學的研究中。我們發現因KIO4-Mn2+-Luminol 系統中，存有氧化劑，可以氧化化合物1、2、6，形成陽離子自由基。因此，化合物1-6會和系統競爭KIO4，造成第一根峰的下降，所產生的自由基，又和系統中活氧物質，如‧OH、O2-等作用，使得第二根峰強度增強，而此變化又以化合物1最為明顯。
加入自由基抑制劑1,4-diazabicyclo﹝2, 2, 2﹞octane (1,4-DO)，會抑制第一根峰、增強第二根峰的放光；在同樣的條件下再加入化合物1，則抑制第一根峰，而第二根峰也抑制。所以，1,4-DO抑制了化合物1的陽離子自由基，使得和活氧物質作用減少，因此，沒有增強第二根峰的放光；加入化合物2、6對放光系統沒有產生的變化。
將化合物1-6應用於檢測dopamine、(+)-epinephrine、catechol及其異構物以及flavones等多酚類物質。大多數物質會抑制兩根訊號的放光強度，這是因為多酚類物質扮演自由基消除劑的角色，它們和三苯胺陽離子自由基反應，影響化合物1-6增強第二根訊號的效應。值得住意的是，實驗中(+)-epinephrine 及7,8-flavone與其它多酚類展現截然不同的效應，部分實驗條件下，兩者皆對第二根訊號有加強的作用，推測可能的原因為兩者結構接有能與金屬形成錯合物的螯合位置，能形成更有效率的催化錯合物增強第二根發光強度。We have investigated the electrochemical, spectral, and kinetic properties of the synthesized triarylamines and their cation radicals and dications. The UV/Vis spectral changes for the formation of cation radicals and dication species of these compounds were successfully observed by repeated scan of the absorption spectra at fixed voltages below their half-wave potentials. The spectral changes for the regeneration of the cation radical and then the neutral species could be observed by resetting the voltage to 0.0 V (vs. Ag/AgCl) after the dicationic species was formed. These observations allowed us to investigate the kinetics of the whole redox processes for some triarylamines. We also found that the rates for the formation of radical cations and dicationic species of these compounds increased exponentially with increasing applied voltages. The kinetic data indicate that the rate constants (k) for the conversion are strongly dependent on the individual step, the applied potential, and the identity of the substituents. Moreover, linear Hammet plots were observed for the half-wave potentials of first redox couples and the absorption maxima (both neutral and cationic species) against the substituent constant (3)Theoretical calculations have revealed that the removal of the first and second electrons from these compounds comes mostly from the nitrogen atom and the phenyl rings, respectively.
Dual chemiluminescence (CL) from the KIO4-luminol-Mn2+ system was originated from different CL pathways participated by various reactive oxygen species (ROS) such as O2-, •OH, and 1O2. It is interesting to examine how the cation radicals generated from derivatives of triarylamine affect the dual CL emission. In the presence of a strong oxidant KIO4 and a catalyst Mn2+, the formation of radical cations of triarylamines inhibited the first peak, but further enhanced the second peak. The resulting CL emission was used to determine the phenolic compounds such as dopamine, (+)-enpinephrine and flavones. These compounds are capable of reacting with ROS and radicals efficiently
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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