1,720,992 research outputs found
Anesthetic efficacy of an eutectic mixture of lidocaine and prilocaine (EMLA) on the oral mucosa: prospective double-blind study with a placebo]
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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
A kinetic analysis of cyanine selectivity: CCyan2 and Cyan40 intercalation into poly(dA-dT).poly(dA-dT) and poly(dG-dC).poly(dG-dC)
No full textA T-jump investigation of the binding of Cyan40 [3-methyl-2-(1,2,6-trimethyl-4(IH)pyridinylidenmethyl)-benzothiazolium ion] and CCyan2 [3-methyl-2-[2-methyl-3-(3-methyl-2(3H)-benzothiazolylidene)-1-propenyl] -benzothiazolium ion] with poly(dA-dT)(.)poly(dAdT) and poly(dG-dC)(.)poly(dG-dC) is performed at I = 0.1 M (NaCl), 25 degrees C and pH 7. Two kinetic effects are observed for both systems. The binding process is discussed in terms of the sequence D + P reversible arrow P,D reversible arrow PDI reversible arrow PDII, which leads first to fast formation of a precursor complex P,D and then to a partially intercalated complex PDI which converts to the fully intercalate complex PDII. Concerning CCyan2 the rate parameters depend on the polymer nature and their analysis shows that in the case of poly(dG-dC)-poly(dG-dC) the most stable bound form is the fully intercalated complex PDII, whereas in the case of poly(dA-dT)-poly(dA-dT) the partially intercalated complex PDI is the most stable species. Concerning Cyan40, the rate parameters remain unchanged on going from A-T to G-C indicating that this dye is unselective. (c) 2006 Elsevier Inc. All rights reserved
The two modes of binding of Ru(phen)(2)dppz(2+) to DNA: Thermodynamic evidence and kinetic studies
No full textThe binding of Ru(phen)(2)dppz(2+) (dppz = dipyrido[3,2-a:2',3'-c]phenazine) to DNA was investigated at pH 7.0 and 25 degrees C using stopped-flow and spectrophotometric methods. Equilibrium measurements show that two modes of binding, whose characteristics depend on the polymer to dye ratio (C-P/C-D), are operative. The binding mode occurring for values Of C-P/C-D higher than 3 exhibits positive cooperativity, which is confirmed by kinetic experiments. The reaction parameters are K = 2 x 10(3) M-1, omega = 550, n = 1, k(r) = (1.9 +/- 0.5) x 10(7) M-1 s(-1) and k(d) = (9.5 +/- 2.5) x 10(3) s(-1) at I = 0.012 M. The results are discussed in terms of prevailing surface interaction with DNA grooves accompanied by partial intercalation of the dppz residue. The other binding mode becomes operative for C-P/C-D < 3 and the equilibria analysis shows this is an ordinary intercalation mode (K = 1.3 x 10(6) M-1, n = 1.5 at I = 0.012 M and K = 2 x 10(5) M-1. n = 1.2 at I = 0.21 M). Similar behaviour is displayed by double-stranded poly(A). (c) 2006 Elsevier Inc. All rights reserved
Dye-induced aggregation of single stranded RNA: A mechanistic approach
No full textThe binding of proflavine (D) to single stranded poly(A) (P) was investigated at pH 7.0 and 25 degrees C using T-jump, stopped-flow and spectrophotometric methods. Equilibrium measurements show that an external complex PDI and an internal complex PDII form upon reaction between P and D and that their concentrations depend on the polymer/dye concentration ratio (C-P/C-D). For C-P/C-D < 2.5, cooperative formation of stacks external to polymer strands prevails (PDI). Equilibria and T-jump experiments, performed at I = 0.1 M and analyzed according to the Schwarz theory for cooperative binding, provide the values of site size (g = 1), equilibrium constant for the nucleation step (K* = (1.4 +/- 0.6) x 10(3) M-1), equilibrium constant for the growth step (K = (1.2 +/- 0.6) x 105 M-1), cooperativity parameter (q = 85) and rate constants for the growth step (k(r) = 1.2 x 10(7) M-1 s(-1), k(d) = 1.1 x 10(2) s(-1)). Stopped-flow experiments, performed at low ionic strength (I = 0.01 M), indicate that aggregation of stacked poly(A) strands do occur provided that C-P/C-D < 2.5. (c) 2006 Elsevier Inc. All rights reserved
Effects of micelle nature and concentration on the acid dissociation constants of the metal extractor PADA
Full text linkThe pyridine-2-azo-p-dimethylaniline (PADA) ligand presents two acid dissociation constants, being pKa1 related to the pyridinium and pKa2 related to the anilinium residue. These have been measured by spectrophotometric titrations in aqueous solutions containing either the anionic (SDS), or the non–ionic (Triton X-100) or the cationic (DTAC) surfactants. The pKai shifts of the charged systems from that of the PADA/Triton X-100 reference (∆pKai0) are compared. For PADA/DTAC ∆pKa10 = 0.05 and ∆pKa20 = 0.6. For PADA/SDS ∆pKa10 = 2.1 and ∆pKa20 = 2.1 both yielding the value of -126 mV for the surface potential (ψ) of SDS. The ψ value, lying between the calculated Stern potential and the zeta potential, indicates that the dye is located on the SDS micelles between the fixed and the shear layer. In contrast, the behaviour of PADA/DTAC is explained assuming that the positively charged deprotonation sites of PADA are forced to protrude towards the bulk solvent by the positive charges of DTAC micelles. The shifts of the apparent pKai from the aqueous values (∆pKaiw) have also been analysed. Concerning PADA/Triton X-100, the shifts ∆pKa1w = -0.1 and ∆pKa2w = -0.9 are rationalized in terms of dielectric constant reduction at the reaction sites. Concerning PADA/DTAC, ∆pKa1w= -0.05 and ∆pKa2w= -0.3 whereas, for PADA/SDS, ∆pKa1w = 2.0 and ∆pKa2w = 1.2. The pKa2w values decrease on raising the surfactant concentrations for all the investigated systems. This behaviour is explained assuming that the increase of the overall micellar surface and, by consequence, of the reaction sites number, results in a site dilution effect which disfavours proton association. The addition of NaCl induces changes of pKa1 and pKa2 which are explained in terms of (large) reduction of ψ for PADA/SDS and of (small) reduction of the dielectric constant for the other systems
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