1,721,003 research outputs found
Solid-phase microextraction and on-fiber derivatization for assessment of mammalian and vegetable milks with emphasis on the content of major phytoestrogens
Full text linkA new solvent-free method for the simultaneous determination of some major phytoestrogens (equol, enterodiol, daidzein, genistein, glycitein) in different commercial milks (cow, goat and soy-rice) was developed. After solid phase microextraction, performed by direct immersion of a 65 mu m-polydimethylsiloxane-divinylbenzene fiber in diluted (1:100 with 0.2% formic acid - 30% sodium chloride) milk samples (18 degrees C for 20 min under stirring), a direct on-fiber silylation with N,O-bis (trimethylsilyl) trifluoroacetamide) containing 1% trimethylchlorosilane (70 degrees C for 20 min) was performed prior to gas chromatography-mass spectrometry analysis. Since the target compounds were determined as aglycones, the hydrolytic removal of the aglycone from the glycosides was performed. The method permitted the determination of the target analytes in all the considered milk samples as well as the detection of some major amphipathic fats indicating that the approach could potentially be applied in the future for further applications, such as milk profiling
Pd-Nanoparticles-Catalyzed Ullmann-Reactions in Ionic Liquids Using Aldehydes as the Reductants: Scope and Mechanism
No full textAn efficient Ullmann-type
reductive homocoupling of aryl, vinyl
and heteroaryl halides can be promoted
by an aldehyde in tetraalkylammonium
ionic liquids under very mild reaction
conditions. This simple procedure
generates symmetrical biaryls
under relatively mild conditions. The
ionic liquid is crucial for this process
because it behaves simultaneously as a
base, ligand and reaction medium. The
role of the aldehyde is also discussed
and a general mechanism for this unusual
reaction is proposed. These results
open the way to a new efficient
method of Pd-catalysed dehydrogenation
of carbonyl compounds
Pd-Nanoparticles catalyzed one-pot sequential Heck and Suzuki couplings of bromo-chloroarenes in ionic liquids and water
No full textPd nanoparticles generated in green reaction media (viz. ionic liquids and water) catalyze the one-pot
sequential Heck and Suzuki coupling reactions of bromo-chloroarenes to afford unsymmetrically
substituted arenes in good yields
Heck Reactions with Palladium Nanoparticles in Ionic Liquids: Coupling of Aryl Chlorides with Deactivated Olefins
No full textA general method for the
Heck coupling of chloroarenes, including deactivated, electron-
rich compounds, with substituted olefins of low reactivity is presented
Palladium-Catalyzed Cross-Coupling of Styrenes with Aryl Methyl Ketones in Ionic Liquids: Direct Access to Cyclopropanes
No full textThe combined use of Pd(OAc)2, Cu(OAc)2, and dioxygen in molten tetrabutylammonium acetate (TBAA) promotes an unusual cyclopropanation reaction between aryl methyl ketones and styrenes. The process is a dehydrogenative cyclizing coupling that involves a twofold CH activation at
the a-position of the ketone. The substrate scope highlights the flexibility of the catalyst; a reaction mechanism is also proposed
Novel conjugated molecules as nanoparticle-capping agents in surface assisted laser desorption ionization mass spectrometry
No full text
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
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