1,721,371 research outputs found
Production of 3,6-Anhydro-D-galactose from kappa-Carrageenan Using Acid Catalysts
No full textThis study describes acid-catalyzed production of 3,6-anhydro-D-galactose (D-AnG) from kappa-carrageenan, a sulfated polysaccharide with an alternating backbone consisting of D-AnG and D-galactose (D-Gal). We analyzed four hydrolysis products (D-AnG, 5-hydroxymethylfurfural (HMF), levulinic acid (LA), and D-Gal) and reducing sugar contents during acid hydrolysis. Acid screening was carried out using seven acid catalysts which have different acidity. The catalysts showing high D-AnG production and high selectivity were chosen for subsequent experiments. We selected four acid catalysts (HCOOH, CH3COOH, HNO3, and HCl), and studied the effects of catalyst acidity, hydrolysis temperature T, and reaction time t on the production of D-AnG and other hydrolysis products. The optimal condition for maximum production of D-AnG by kappa-carrageenan hydrolysis was T = 100A degrees C and t = 30 min using 0.2 M HCl. Under this condition, 2.81 g/L D-AnG (33.5% of theoretical maximum) could be obtained from 2% (w/v) kappa-carrageenan. In general, the maximum values of D-AnG, D-Gal, and the sum of two by-products (HMF and LA) increased with the acidity of catalysts. However, HNO3 was an exception in that the maximum production levels of HMF and LA were unusually low compared with other acid catalysts. D-AnG was successfully purified from acid hydrolysates using silica gel chromatography and the product was nearly 100% pure. This effective D-AnG production could facilitate future studies on the conversion of D-AnG to biofuels and biochemicals.11Nsciescopuskc
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
The effect of acidification on the bioavailability and electrochemical lability of zinc in seawater
No full text11Nsciescopu
원자층 증착법으로 형성된 박막의 단차 피복성 예측을 위한 모델링에 관한 연구
No full text학위논문(박사) - 한국과학기술원 : 신소재공학과, 2007. 8, [ ⅹ, 135 p. ]Atomic layer deposition (ALD) is one of the most promising thin film deposition techniques to enable the nano-scale device fabrication, due to its advantages over other conventional deposition techniques such as physical vapor deposition and chemical vapor deposition. The advantages include the ability to control the film thickness at atomic dimensions, the ability to produce highly conformal thin films, and wide area uniformity, as a result of surface-limited reactions between alternately dosed precursor and reactant gases. Among these, the production of highly conformal thin films on micro-features with high aspect ratios has been considered as one of the greatest advantages, especially for capacitors in semiconductor memories. However, even in ALD, as aspect ratios severely increase, it is not trivial to obtain conformal thin films on micro-features. To support this task, it is necessary to theoretically investigate the film deposition inside a micro-feature in ALD and predict the process time required to achieve reasonable film step coverage. In general, ALD of binary compound systems is performed by supplying precursor and reactant gases onto the outermost surface sequentially, with purges of an inert gas between precursor and reactant gases. The non-overlapping alternate dosing of precursor and reactant gases prohibits reactions in the gas-phase and thus leads to the film deposition that highly depends on the adsorption and surface reaction kinetics. Among these steps in one ALD cycle, the film step coverage is greatly influenced by the precursor injection step because much more reactant is supplied to the reactor than precursor. A film growth model on micro-features was proposed to evaluate the film step coverage depending on the precursor injection time in ALD. The proposed model is based on that the chemisorption rate of precursors at a certain position along the depth of a micro-feature is determined by the total flux of precursors and the sticking ...한국과학기술원 : 신소재공학과
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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