1,720,957 research outputs found
Using Raman Spectroscopy for Nanoscale Material Detection and Chemical Reaction Kinetics Study
No full text拉曼光譜學是用來研究分子與晶格的振動及旋轉模式的分析技術. 拉曼散射,一種光的非彈性散射, 是由觀察者C.V.Raman的名字來命名. 自從這位印度科學家在1928年利用太陽光觀察到此現象, 科學家們便逐漸的開始對拉曼散射產生興趣. 有別於其他分析技術, 拉曼光譜學有著以下特點.
第一點, 由於拉曼光譜學是一種光學分析技術, 所以是一種非侵入式且非破壞的分析方法. 第二點, 不同的分子其化學結構與鍵結必定有所不同, 使得他們擁有獨一無二的振動模式. 若利用拉曼光譜學來進行分析, 就可以獲得高專一性的分子指紋. 這項特點讓拉曼光譜學可以輕易的分辨出同分異構物的差異, 這是其他分析方法如質譜儀無法辦到的.第三點, 樣品製備的條件門檻相對簡單. 無論是固態, 液態或氣態, 有機物或無機物都可以進行分析. 樣品本身也不需經過特殊處理, 這是紅外線吸收光譜等分析技術無法相比的. 另外由於只有雷射光源照射到的部分才會產生拉曼散射, 所以樣品的體積可以十分微小 (雷射光點大小約 2 微米). 如果是玻璃或石英包裝樣品, 甚至可以透過包裝直接進行分析而不需拆封. 最後一點, 現在市面上已經有許多商業化的拉曼光譜分析儀器, 使用起來相當簡單, 只需幾秒鐘就可以得到所需的資料. 綜合上述優點, 拉曼光譜分析學已經成為現今相當有力的化學分析方法. 為了進一步改善, 而其他相關的拉曼光譜技術也被後人陸續發展出來. 例如表面增強拉曼光譜學 (可增強拉曼訊號強度), 顯微拉曼光譜學 (可改善空間解析度)以及共振拉曼光譜學 (可取得特殊資訊).
此論文可以概分為兩大研究主軸. 在第一部分中, 我們親自架設了一套探針增強式拉曼光譜系統. 並利用此系統當作分析工具, 藉由其同時擁有表面增強式拉曼光譜的訊號加強以及原子力顯微鏡的高空間解析度的優點, 進一步觀察石墨表面上的奈米尺度缺陷. 同時, 根據實驗的數據結果, 我們也提出一方法來評估此探針增強式拉曼光譜系統在量測如石墨這類非均相物質時的訊號增強係數. 在第二部分, 我們試著利用拉曼光譜技術進一步探討醣類分子在進行水解反應時的反應機制與動力學. 醣水解反應在中性以及弱酸環境被認為是一種由於質子濃度增加以至於溶液酸鹼度降低的自催化反應, 但是卻缺乏直接的證據證明真正的催化物為何. 在此, 我們藉由在不同的反應溫度(80~100℃)與溶液酸鹼度(pH1~pH5)進行兩種雙醣系統(雙果醣以及纖維二醣)的水解反應, 來觀察醣類水解時自催化反應的真正催化物為何, 並且推論出一反應機制來解釋此現象. 這項重大的發現或許可以使得纖維素等多醣體的水解反應效率大幅提升.Raman spectroscopy is a method to observe the vibration behavior of molecules when they are excited by photons. Since C.V. Raman discovered the Raman scattering effect in 1928, people have gradually paid their attention on this interesting subject. Compare with other analytical techniques, Raman spectroscopy has several distinguishing features.
First, this is an optical methodology thus no destructive damage or invasive behavior will take place. Second, each molecule has its own chemical structure so their vibration modes are highly specific like a chemical fingerprint. Isomers can be distinguished easily even they have identical chemical structure formula and molecular weight. Third, the demands for sample preparation are relative simple. It could be organic or inorganic; solids, liquids or gas. And because the laser spot size is only 1~
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
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