1,720,961 research outputs found
Sintesis Hemiterpena Turunan 1-Bromo-3-Metil-2-Butena
Full text linkMonoterpena dan seskuiterpena merupakan kelompok
terpena yang paling banyak dimanfaatkan sebagai bahan pewangi. Hemiterpena sangat berpotensi sebagai senyawa pewangi, tetapi jarang dijumpai di alam. 3-Metil-2-butena-1-il asetat merupakan hemiterpena yang terdapat dalam minyak ylang-ylang (Cananga adorata), sedangkan 3-metil-2-butena-1-ol merupakan hemiterpena yang ditemukan dalam buah jeruk, anggur, dan raspberi. Penelitian yang dilakukan berhasil mensintesis tiga hemiterpena. Sintesis dilakukan dalam dua tahap, tahap pertama adalah reaksi asam karboksilat dengan natrium bikarbonat sehingga diperoleh garam natrium 3-fenil-2-propenoat. Reaksi substitusi nukleofilik 1-bromo-3-metil-2-butena pada tahap kedua dengan nukleofil ion karboksilat yang diperoleh pada tahap pertama diperoleh hemiterpena. Reaksi-reaksi yang melibatkan asam karboksilat berupa asam 3-fenil-2-propenoat, asam 2- metilbutanoat, dan asam 2-metilpropanoat masing-masing diperoleh hemiterpena 3-metil-2-butena-1-il-3-fenil-2-propenoat dengan rendemen 91%, 3-metil-2-butena-1-il-2-metilbutanoat dengan rendemen 83%, 3-metil-2-butena-1-il-2-metilpropanoat dengan rendemen 88%. 3-Metil-2-butena-1-il-3-fenil-2-propenoat dengan dengan struktur 3-fenil-2-propenoat menunjukkan panjang gelombang maksimum (λmaks) 300 nm yang merupakan daerah serapan UV-B sehingga berpotensi sebagai bahan tabir surya.
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Monoterpene and sesquiterpene are a group of terpene
widely used as fragrance ingredient. Hemiterpene is potentially as fragrance compound, but rarely found in nature. 3-Methyl-1-yl acetate is hemiterpene on oil of ylang-ylang (Cananga adorata), while 3-methyl-2-butene-1-ol is hemiterpene found in fruits as citrus, grapes, and raspberry. This research aims to syntheses three hmiterpene. Synthesis approach with two steps, the first step was reacted between carboxylic acid 3-phenyl-2-propenoat with sodium bicarbonate obtained sodium salt of 3-phenyl-2- propenoat. The second steps nucleophilic substitution reaction of
1-bromo-3-methyl-2-butene with nucleophile of carboxylate ion obtained in the first steps was obtained hemiterpena. The
reactions of carboxylic acids as 3-phenyl-2-propenoat acid, 2-
metilbutanoat acid, and 2-methylpropanoat acid were obtained 3- methyl-2-butene-1-yl-3-phenyl-2-propenoat in 91% yield, 3- methyl-2-butene-1-yl-2-metilbutanoat in 83% yield, 3-methyl-2- butene-1-yl-2-metilpropanoat in 88% yield. 3-Methyl-2-butene-1- yl-3-phenyl-2-propenoat has 3-fenil-2-propenoat structure showed maximum wavelength (λmaks) 300 nm which is the area of UV-B has potentially as sunscreen ingredients
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
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