1,721,063 research outputs found
Nitric Oxide Photoreleasing Multilayer Films
Full text linkIn this contribution we report the preparation and characterization of Langmuir–Schaefer (LS)
multilayer films of a mesogen-bearing cationic amphiphile able to release nitric oxide (NO) under the
exclusive control of light stimuli. The morphology and spectroscopic features of the floating films at the
water–air interface are inspected by Brewster angle microscopy and UV-Vis reflection spectroscopy,
respectively. Multilayer films are obtained by horizontal lifting deposition onto hydrophobized quartz
substrates and characterized by UV-Vis absorption spectroscopy. The capability of these films to
deliver NO is investigated by the direct monitoring of this radical species through an ultrasensitive NO
electrode. The results obtained unequivocally demonstrate that the multilayers are stable in the dark
but, in contrast, supply NO at nanomolar level upon illumination with visible light
Langmuir-Schäfer films of an ethane-bridged bis(Zn porphyrin): spectroscopic evidences of molecular organization and activity inside multilayers
No full textLangmuir-Schäfer Films of New Functional Amphiphilic Nickel(II) and Zinc(II) Schiff-Base Complexes
Full text linkThe synthesis of novel functional amphiphilic dipodal NiII (1)
and ZnII (2) Schiff base complexes and the preparation/characterization
and optical properties of Langmuir–Schäfer (LS)
multilayer films are reported. The existence of stacked 3D
aggregates is observed for all films, as established by the
combination of reflection spectroscopy and Brewster angle
microscopy. Although aggregate formation does not involve
major electronic changes, as evidenced by analysis by absorption
spectroscopy, fluorescence emission is much more sensitive to the chemical environment, and complete
quenching is observed in the multilayer LS aggregates. However,
in the limit of negligible interchromophore interactions,
achieved by means of mixed LS multilayer films the fluorescence
is restored by using arachidic acid as a spacer diluent,
and LS layers of 2 behave as related self-assembled monolayers
Bichromophoric multilayer films for the light-controlled generation of nitric oxide and singlet oxygen
Full text linkIn this contribution we report the design, preparation and characterization of bichromophoric Langmuir–Schaefer multilayer films incorporating a tailored nitric oxide (NO) photodonor (1) and an ethylene-bridged zinc porphyrin dimer (2). They are achieved by exploiting the coordination of a pyridine appendage of the NO photodonor to the metal centers of the porphyrin units. Quite uniform floating films at the water–air interface are obtained spreading a mixture of 1:2 in the molar ratio 20:1 as confirmed by Brewster angle microscopy. The floating films are successfully transferred onto quartz slides by horizontal lifting deposition and the resulting hybrid multilayers are characterized by steadystate UV-Vis absorption, fluorescence and laser flash photolysis. The high ratio between the two chromogenic centers prevents the porphyrin aggregation, leading to photoresponsive bichromophoric films able to generate NO and singlet oxygen, 1O2 (1Dg), under the exclusive control of visible light stimuli
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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