1,720,957 research outputs found
On-water Catalyst-free Synthesis of 3-Alkenyl Oxindoles
Get PDF3-Alkenyl oxindoles are key structural motifs in organic chemistry with a wide range of applications mainly in the pharmaceutical industry, due to excellent biological activities such as anti-inflammatory, antiviral, antibacterial, and anticancer properties. With the discovery of the importance of oxindole derivatives in the pharmaceutical industry, demand for sustainable protocols for the synthesis increased as most classical methods have their limitations and flaws. In this study on-water, catalyst-free, atom-economical green approach was developed for the synthesis of 3- alkenyl oxindole derivatives using oxindole and aldehyde as starting materials. The reaction between oxindole and benzaldehyde was conducted on water under catalyst-free conditions. Interestingly, 100% conversion was observed when the reaction was carried out for 24 hours at 100° C. As the next step, the applicability of the developed approach was proven for different aldehydes. Furaldehyde, cinnamaldehyde, and vanillin were used as the aldehydes to synthesize 3- alkenyl oxindole derivatives, and the isolated yields were obtained as 77%, 54%, and 51% respectively. The desired product formation was confirmed by comparing the Rf value of the product with that of the previously synthesized well-characterized compounds; 3- benzylideneindolin-2-one, 3-(furan-3-methylene)indolin-2-one, 3-(3-phenylallylidene)indolin-2- one, and 3-(4-hydroxy-3-methoxybenzylidene)indolin-2-one using Thin Layer Chromatography. Further characterization was done by Fourier-transform infrared (FT-IR), Ultraviolet-visible (UVVis), and Nuclear Magnetic Resonance (NMR) spectroscopic techniques. In further optimization steps, the reaction was performed using surfactants as the catalyst. By adhering to the green chemistry principles different sources of biosurfactants were used including Acacia concinna pods, Sapindus emarginatus fruit pericarp, Dillenia retusa fruit pericarp, and Trigonella foenumgraecum seeds. In order to compare the effect of biosurfactants, a synthetic surfactant, sodium dodecyl sulfate (SDS) was used as the catalyst. When the reaction was carried out for 21 hours at 100 °C using fruit pericarp of Sapindus emarginatus as the source of biosurfactant, 100% conversion was observed. Using water as the solvent, readily available starting materials, higher yield, and eco-friendliness and catalyst-free conditions suggest the possible use of the developed method for large-scale preparations of 3-alkenyl oxindole derivatives.
Keywords: Green protocol, Oxindole derivatives, Surfactant, On water synthesis, Catalyst-fre
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
Green Synthesis of Biolubricant from Palm Oil Biodiesel
Get PDFLubricants are the substances used to lubricate machinery parts to reduce friction and increase their lifetimes. Producing environment-friendly lubricants from renewable feed stocks as alternatives to depleting petroleum based resources has attracted considerable attention in recent years. The lubricants prepared from renewable feed stocks exhibited excellent lubricating properties and nontoxicity. The present study was carried out to synthesise biolubricant base stock from palm oil biodiesel using a green approach. Synthesis of biodiesel and biolubricants using green approaches have attracted much attention in last decade. Synthesis is mainly based on three steps: firstly, the synthesis of palm oil biodiesel, then epoxidation of biodiesel and finally ring-opening of epoxide to yield the potential biolubricant. The trans-esterification reaction was performed to yield biodiesel from palm oil using methanol and NaOH as a catalyst. The modification of biodiesel in to epoxidised form was carried out using glacial acetic acid, H2O2 and amberlite IR-120H resin as a catalyst. The ring opening of epoxidised biodiesel was performed using 1-naphthol in the presence of magnesium silicate catalyst, which was synthesise using rice hull ash. However, the expected ring opening product was not observed. Then, epoxidised biodiesel was reacted with lauric acid in the absence of magnesium silicate and the expected product was formed. The prepared magnesium silicate catalyst was characterised by X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). Fourier Transform Infra-Red (FTIR) spectroscopy and GC-MS analysis were used to characterise the products. Both GC-MS and FTIR results indicates the formation of fatty acid methyl esters and their conversion to epoxidised form. Disappearance of epoxy characteristic band which appeared at 845 cm-1 in FTIR spectrum confirms the formation of potential biolubricant. Density and viscosity of potential biolubricant were measured in contrast to the biodiesel. The measured density values of biodiesel and biolubricant are 0.830 g/cm3, 0.937 g/cm3 respectively. The measured kinematic viscosity values of biodiesel and biolubricant at 40° C are 4.0932 cSt, 14.9087 cSt and at 100° C are 1.6009 cSt, 3.5539 cSt respectively. These results illustrate that synthesised biolubricant consist of better lubricant properties compared to the biodiesel.Keywords: Biolubricants, Green approach, Biodiese
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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