1,720,962 research outputs found
METODE ISOLASI YANG MUDAH DALAM ISOLASI SENYAWA β-KAROTEN DARI LABU KUNING (Cucurbita moschata Duch ex Poiret)
Full text linkABSTRACTPumpkin (Cucurbita moschata Duch ex Poiret), a fruit that contains several compounds, has activities to protect the human body from free radicals. Provitamin A is recognized as an antioxidant compound. Antioxidants can protect the body’s damage caused by free radicals. The purpose of this study was to isolate beta carotene compounds and test the purity of beta carotene isolates obtained using DR-UV and infrared spectrophotometry. Pumpkin is extracted using acetone: petroleum ether with a ratio (1: 1). Identification of beta carotene from extracts was carried out using TLC with the mobile phase of ethanol: acetone: n-hexane with a ratio (2: 1: 1) and scan spectrum using a UV-Vis spectrophotometer. Beta carotene was identified as the result of TLC elution on UV 254 and 366 nm which showed 2 spots. Detection of beta carotene spectra was carried out in the range of 350 to 550 nm and obtained beta carotene peaks at wavelength x nm. The extract purification process was carried out using Preparative TLC with the mobile phase of ethanol: acetone: n-hexane with a ratio (2: 1: 1) and obtained isolates cleaned first using chloroform: methanol ratio of 1: 1. The isolates were dried and tested using DR-UV and infrared spectrophotometry. Isolates from Cucurbita moschataDuch ex Poiret extract) contain beta carotene, zeaxanthin.Keywords: pumpkin; beta carotene; isolatio
Reduksi Katalitik 4-Nitrofenol dengan Katalis Nanopartikel Perak Terkonjugasi L-Lisine
Full text linkNanopartikel perak berpotensi menjadi katalis homogen dalam reduksi 4-nitrofenol menjadi 4-aminofenol. Berbagai penelitian menunjukan L-lisine berpotensi bertindak sebagai agen penstabil nanopartikel perak sehingga mempengaruhi sifat katalitik nanopartikel perak. Pada penelitian ini dilakukan reduksi 4-nitrofenol menggunakan katalis nanopartikel perak yang terkonjugasi dengan L-lisini dengan reduktor NaBH4. Dari hasil reduksi didapatkan nanopartikel perak dengan dosis 50 ?L mampu mengubah 99,99% 4-nitrofenol menjadi 4-aminofenol dengan tetapan laju reaksi 0,1130 menit-1
Novel Scanometric Assay for Charantin in Bitter Melon (Momordica charantia) Extract Based on Immobilized Silver Nitrate and Methylene Blue as Colorimetric Paper
Full text linkBitter melon (Momordica charantia) contains charantin that responsible for
the antidiabetic activity. Therefore, it is important to determine charantin in
the extracts for the purposed of its formulation or quality control. Herein, we
proposed a novel scanometric assay for charantin determination in the bitter
melon extracts based on immobilized silver nitrate and methylene blue as a
colorimetric paper. The presence of charantin can be detected simply via the color
change from blue to green and can be quantified using a scanner via the ImageJ
software. The proposed charantin sensor has a response time of 8 mins with the
linear range of 300 to 1000 μg/mL and the detection limit was 216.25 μg/mL.
The sensor has good reproducibility (RSD = 2.86%) with the stability up-to 5
months. The sensor was applied to determine charantin in the sample extracts,
and the result shown in a good agreement with TLC method
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
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