1,720,988 research outputs found
Redox processes of Ruthenium(II) Polypyridine complexes induced by Fast Atom Bombardment Mass Spectrometry
No full textIdentification of caffeine and its metabolites in human urine extracts by electron ionization tandem spectrometry
No full textElectron impact ionized purine bases such as caffeine and its metabolites (theophylline, theobromine, paraxanthine, 1-methylxanthine, 3-methylxanthine and 7-methylxanthine) were characterized by tandem mass spectrometry. The direct analysis of human urinary extracts by tandem mass spectrometry allows the unambiguous identification of caffeine and its metabolites present simultaneously in the urin
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
Self-assembling of Cytosine Nucleoside into Triply-bound Dimers in Acid Media. A Comprehensive Evaluation of Proton-bound Pyrimidine Nucleosides by Electrospray Tandem Mass Spectrometry, X-rays Diffrattometry and Theoretical Calculations
No full textElectrospray tandem mass spectrometry (ESI-MS/MS) is used to evaluate the assembling of cytosine and thymine nucleosides in the gas phase, through the formation of hydrogen bonded supermolecules. Mixtures of cytidine analogues and homologues deliver in the gas phase proton-bound heterodimers stabilized by multiple interactions, as proven by the kinetics of their dissociation into the corresponding protonated monomers. Theoretical calculations, performed on initial structures of methylcytosine homodimers available in the literature, converged to a minimized structure whereby the two pyrimidine rings interact through the formation of three hydrogen bonds of similar energy. The crystallographic data here reported show the equivalency of the two interacting pyrimidines which is attributable to the presence of an inversion center. Thymine and uracil pyrimidyl nucleosides form, by ESI, gaseous proton-bound dimers. The kinetic of their dissociation into the related protonated monomers shows that the nucleobases are weekly interacting through a single hydrogen bond. The minimized structure of the protonated heterodimer formed by thymine and N-1-methylthymine confirmed the existence of mainly one hydrogen bond which links the two nucleobases through the O4 oxygens. No crystallographic data exists on thymine proton-bound species, nor have we been able to obtain these aggregates in the solid phase. The gaseous phase, under high vacuum conditions, seems therefore a suitable environment where vanishing structures produced by ESI can be studied with a good degree of approximation
Monitoring of human exposure to environmental xenobiotics by isotope dilution mass spectrometry
No full textVariations 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
Synthesis, biological evaluation, and molecular modeling of oleuropein and its semisynthetic derivatives as cyclooxygenase inhibitors
No full textOleuropein, the main phenolic compound in virgin olive oil, and several of its derivatives such as
oleuropein aglycone, hydroxytyrosol, and their respective acetylated lipophilic forms were obtained
by simple and environmentally friendly semisynthetic protocols. The same molecules were then
tested in vitro and in vivo, comparing their intriguing anti-COX-1 and anti-COX-2 properties to those
of well-known anti-inflammatory drugs such as ibuprofen and celecoxib. Finally, molecular modeling
experiments displaying the most probable binding modes within the classical binding clefts of the
enzymes suggest the heme moiety as a potential alternative target
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