1,720,963 research outputs found
Determination of Brain Extracted Lipids by Thin-Layer Chromatography – Imaging Desorption Electrospray Ionization (TLC-Imaging DESI).
No full textDesorption electrospray ionization mass spectrometry analysis of lipids after two-dimensional high-performance thin-layer chromatography partial separation.
Full text linkMolecular imaging of separate but still incompletely resolved spots on high-performance thin-layer chromatography (HPTLC) plates is used for the direct analysis of porcine brain lipids by desorption electrospray ionization mass spectrometry (DESI-MS). Eight class-specific spots were imaged in the negative ion mode and shown to contain more than fifty lipids. A low lateral resolution of 400 × 400 μm allowed simple, rapid, and incomplete separation to be combined with DESI imaging for the identification of many components of these extremely complex mixtures. In this work, tandem mass spectrometry (MS/MS) was also employed to confirm the identity of particular lipids directly on HPTLC plates
Determination of RSD921 in human plasma by high-performance liquid chromatography-tandem mass spectrometry using tri-deuterated RSD921 as internal standard: application to a phase I clinical trial.
No full textA fast, sensitive and specific method is presented for the quantification of RSD921 in human plasma by liquid chromatography coupled with tandem mass spectrometry using tri-deuterated RSD921 (3d-RSD921) as an internal standard. A single-step liquid/liquid extraction was performed with diethyl ether/hexane (80:20, v/v) using 0.5 ml of plasma. The plasma calibration curves were linear from 0.1 to 20 ng ml-1 (r > 0.999). Between-run precision, based on the percent relative deviation for replicate (n = 40) quality controls, was ≤7.27% (0.5 ng ml-1), ≤7.39% (5.0 ng ml-1), and ≤5.06% (20.0 ng ml-1). Between-run accuracies, based on the relative error, were ±2.59%, ±1.23% and ±1.64% respectively. The method was developed to evaluate the pharmacokinetic profile after 15 min of intravenous stepwise-ascending infusion dose of RSD921 in 18 healthy volunteers. A dissociation study of protonated RSD921 and 3d-RSD921 by collision-induced dissociation using in-source fragmentation and tandem mass spectrometry is also presented. Copyright © 2001 John Wiley & Sons, Ltd
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
Toxin IV-5 accounts for the relaxing activity of Tityus serrulatus venom in the rabbitcorpus cavernosum
No full textSequence and structure-activity relationship of a scorpion venom toxin with nitrergic activity in rabbit corpus cavernosum.
No full textAn alpha-toxin responsible for nitric oxide (NO) release in rabbit corpus cavernosum (RbCC) was isolated from Tityus serrulatus venom (TSV). The isolated peptide (molecular mass of 7427.66+/-0.15 Da) was identified as Ts3 after determination of Cys residues, N-terminal amino acid analysis, and proteolytic peptide mapping. Ts3 (30 nM) markedly relaxed the RbCC; this response was blocked by the NO synthesis inhibitor N(omega)-nitro-L-arginine methyl ester (100 microM) and the Na+ channel blocker tetrodotoxin (100 nM). Synthetic peptides based on either Ts3 (P1-16, P17-32, P33-48, P49-64, P9-24, P25-40, P41-56, YGLPDKVPTKT) or Bukatoxin (isolated from Buthus martensi Karsch scorpion venom) sequence (Buka11, Buka11-B, PDKVP, PDSEP) were assayed. These peptides slightly relaxed the RbCC, and such an effect was independent of Na+ channel activation or NO release. Our results indicate that Ts3 exerts nitrergic actions and contributes to the relaxing activity of TSV in RbCC, thus providing a valuable tool to investigate the mechanisms underlying nerve activation in erectile tissues, because NO released from nitrergic fibers plays a key role in the erectile process. Our findings revealed the key importance of the Ts3 structure three-dimensional conformation maintenance for biological activity, because linear peptide sequences neither presented substantial relaxations nor was this effect related to nitrergic activity
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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