1,720,962 research outputs found
Isothiazoles. Part 12: Isothiazolylphosphonates, a new class of isothiazoles dioxides
No full textWe describe a mild and efficient method to prepare 3-amino-4,5-dihydro-5-isothiazolylphosphonates from 3-amino-5-unsubstituted isothiazole dioxides. Starting from 3-amino-5-bromo-isothiazole dioxides either 3-amino-5-isothiazolylphosphonates or 5-diethoxyphosphoryl-4,5-dihydro-4-isothiazolylphosphonates were prepared. Isothiazolylphosphonates represent a new class of isothiazole dioxides. Some preliminary investigations on the reactivity with 1,3-dipoles were reported
Structural elucidation of the Rifaximin Ph. Eur. Impurity H
No full textRifaximin, a semisynthetic, rifamycin-based non-systemic antibiotic is used in the treatment of acute and chronic gastrointestinal disorders. The aim of this study was the elucidation of the molecular structure of the 802 Dalton impurity which was found in Rifaximin industrial batches and reported with an erroneous structure in European Pharmacopoeia 6.5 (2009) [7] monograph as Rifaximin Impurity H. This impurity was isolated from Rifaximin by preparative HPLC and purified by column chromatography. The molecular structure was evidenced by means of 1H and 13C NMR spectroscopy, mass spectrometry and FT-IR
Direct conversion of polyconjugated compounds into their corresponding carboxylic acids by Acetobacter aceti
Full text linkThe conversion of polyconjugated aldehydes or alcohols into their corresponding acids was carried out using Acetobacter aceti. The analytical results were compared with those of the acids chemically obtained using a Horner-Wittig reaction
Enhancing topical delivery of resveratrol through a nanozing approach
No full textResveratrol is a naturally occurring polyphenol with strong antioxidant and free radical scavenging properties, recently proposed as a therapeutic agent for skin diseases. In this study, we investigated the possibility of improving the dermal bioavailability of the poorly water-soluble drug resveratrol by nanocrystal technology. To this purpose, nanosuspensions were prepared by the wet media milling technique, using Poloxamer 188 or Tween 80 as stabilizers, and characterized by means of both solid state and morphological and dimensional studies. All analytical data demonstrated that neither a modification of the drug crystalline pattern nor the isomerization of the trans double bond were observed after the wet media milling particle size reduction process, which produced rounded and smooth nanocrystals with a mean diameter ranging between 0.2–0.3 μm. Resveratrol skin delivery from nanosuspension formulations was evaluated by the pig ear skin model via tape stripping. Results of the experiments showed that after application of nanosuspension formulations, higher amounts of resveratrol could penetrate the skin at deeper levels compared to drug coarse suspensions. The antioxidant activity of resveratrol in nanocrystals was assessed by the DPPH assay, which demonstrated that the size reduction process as well as the formulation compositions did not modify the drug antioxidant activity
Pyrrolyl-silicon compounds with different alkyl spacer lengths : synthesis, electrochemical behavior and binding properties
No full textThis work reports a joint experimental-theoretical investigation of pyrrolyl-silicon compounds with different alkyl spacers, namely propyl, butyl and hexyl side chains carrying silicon-based end groups. For the electrochemical study, the monomers with methoxysilyl end groups spaced through butyl and hexyl chains were ad-hoc synthesized. Structurally different oligomeric domains are promoted during electropolymerization as a result of irreversible hydrolysis of methoxy end groups by acid intermediate σ-oligomers. The onset of OH-π stabilizing interactions and the charge pinning action of silanol promotes mixed n-p doping behavior of the hybrid films. The more important charge trapping in the case of propyl spacer is attributed to effective (through bond) inductive effects and conformational restrictions. MD simulations of chemisorption of hydrolyzed oligo-pyrroles onto γ-Al2O3 surface confirmed the propyl spacer as the optimum alkyl chain length for stratification and interpenetration of adsorbed hybrid layers
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
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