1,720,967 research outputs found
Synthesis and properties of polyfunctional pyridines.
No full textPyridine ring bearing compounds are found in many natural products, active pharmaceuticals and functional materials. According MDL Drug Data Report pyridine fragment is the most abundant heterocyclic fragment found in the drug molecules and is present in more than 7000 existing drugs. Bipyridine and terpyridine carcasses are well known for their chelating ability, which is exploited in many fields including enantioselective catalysis and chemotherapy. 1,4-Dihydropyridine can be used as core fragment for fluorescent sensors. Pyridine ring is also used as electron acceptor for electron transfer in organic light emitting diodes. The aim of this work is the a development of synthetic methods for 5-hydroxyomeprazole, bromocyclopropylpyridines, orelanine and terpyridine building blocks. The existing methods for each of the target system have many flaws and the 5-hydroxyomeprazole has no synthetic method at all. There was a chemical synthesis pathway for 5-hydroxyomeprazole developed. It was found that methyl 2,4-dichloro-5,6-dimethylpyridine-3-carboxylate reaction with two equivalents of sodium methoxide product distribution depends on reaction temperature. The procedure for regeneration this reaction side products to the starting compound was developed. It was found that during hydrodehalogenation reaction of 2-chloro-5,6-dimethyl-4-methoxypyridine-3-carboxylate under 80 atmospheres pressure, the hydrolysis of 4-methoxy group occurs. Non-aqueous Sandmeyer reaction conditions for bromo(chloro)cyclopropylpyridines were developed. It was found that Sandmeyer reaction of aminocyclopyridines with copper(II) bromide and alkylnitrite undergoes both cationic and radiacal pathway. 2-pyridinediazonium ion formed upon reaction of 2-amino-5-cyclopropylpyridine is apparently unstable in rather polar solvents and undergoes heterolytic cleavage. The produced highly reactive cation reacts with any available nucleophile. Unpublished formation of ω-halogenoalcoxypyridines was observed. Novel improved total synthesis of orelanine was developed. For this synthesis novel an efficient aqueous synthetic pathway for 3,4-dimethoxypyridine was applied and transition metal catalysis free 3,4-dimethoxypyridine C-C homocoupling method was developed. Synthesis of ,6''-bis(bromomethyl)-4'-(4-nitrophenyl)-2,2':6',2''-terpyridine utilizing Kröhnke pyridine synthesis method was developed
Daugiafunkcinių piridino darinių sintezė ir savybių tyrimas.
No full textPyridine ring bearing compounds are found in many natural products, active pharmaceuticals and functional materials. According MDL Drug Data Report pyridine fragment is the most abundant heterocyclic fragment found in the drug molecules and is present in more than 7000 existing drugs. Bipyridine and terpyridine carcasses are well known for their chelating ability, which is exploited in many fields including enantioselective catalysis and chemotherapy. 1,4-Dihydropyridine can be used as core fragment for fluorescent sensors. Pyridine ring is also used as electron acceptor for electron transfer in organic light emitting diodes. The aim of this work is the a development of synthetic methods for 5-hydroxyomeprazole, bromocyclopropylpyridines, orelanine and terpyridine building blocks. The existing methods for each of the target system have many flaws and the 5-hydroxyomeprazole has no synthetic method at all. There was a chemical synthesis pathway for 5-hydroxyomeprazole developed. It was found that methyl 2,4-dichloro-5,6-dimethylpyridine-3-carboxylate reaction with two equivalents of sodium methoxide product distribution depends on reaction temperature. The procedure for regeneration this reaction side products to the starting compound was developed. It was found that during hydrodehalogenation reaction of 2-chloro-5,6-dimethyl-4-methoxypyridine-3-carboxylate under 80 atmospheres pressure, the hydrolysis of 4-methoxy group occurs. Non-aqueous Sandmeyer reaction conditions for bromo(chloro)cyclopropylpyridines were developed. It was found that Sandmeyer reaction of aminocyclopyridines with copper(II) bromide and alkylnitrite undergoes both cationic and radiacal pathway. 2-pyridinediazonium ion formed upon reaction of 2-amino-5-cyclopropylpyridine is apparently unstable in rather polar solvents and undergoes heterolytic cleavage. The produced highly reactive cation reacts with any available nucleophile. Unpublished formation of ω-halogenoalcoxypyridines was observed. Novel improved total synthesis of orelanine was developed. For this synthesis novel an efficient aqueous synthetic pathway for 3,4-dimethoxypyridine was applied and transition metal catalysis free 3,4-dimethoxypyridine C-C homocoupling method was developed. Synthesis of ,6''-bis(bromomethyl)-4'-(4-nitrophenyl)-2,2':6',2''-terpyridine utilizing Kröhnke pyridine synthesis method was developed
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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