1,721,260 research outputs found
Light induced reactions in cryogenic matrices (highlights 2011–2012)
No full textIn this chapter, relevant studies published in 2011 and 2012 and focusing on the subject of light induced reactions in cryogenic matrices are reviewed. These studies range from conformational isomerizations to complex (bond-breaking)/(bond-forming) processes induced either by ultraviolet-visible or infrared light, and illustrate recent applications of the matrix isolation technique in these domains. Photochemical processes in which noble gas atoms participate directly, leading to formation of covalently bound noble gas containing molecules, are also addressed briefly.Fil: Gomez Zavaglia, Andrea. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigación y Desarrollo en Criotecnología de Alimentos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Criotecnología de Alimentos. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Criotecnología de Alimentos; Argentina. Universidad de Coimbra; PortugalFil: Rui, Fausto. Universidad de Coimbra; Portuga
Tautomers and UV-Induced Photoisomerization of a Strongly Intramolecularly H-Bonded Aromatic Azo-Dye: 1-(Cyclopropyl)diazo-2-naphthol
No full textAromatic azo compounds have a wide range of industrial applications as dyes in optical and color-changing materials and can also be exploited in the design of new photodynamic molecular systems. The azo derivative 1-(cyclopropyl)diazo-2-naphthol was isolated in low-temperature cryogenic matrices, and its molecular structure, tautomeric equilibrium, and photochemical transformations were characterized by infrared spectroscopy and theoretical calculations. Only azo enol forms having the OH group involved in a strong intramolecular hydrogen bond, forming a six-membered ring with the azo group, were found experimentally. Irradiation with a narrowband source in the near-UV range generates different rotameric and tautomeric azo-enol and keto-hydrazone forms that can be interconverted at different irradiation wavelengths
Evaluation of Detachment Between Layers of Ancient Plaster Renderings: Comparison Between the Traditional Technique and a New and Innovative Automated Procedure Called PICUS
No full textDuring a diagnostic campaign, most cultural heritage properties can be considered structurally as a multilayered system. The causes and phenomenology of degradation may involve the surface alone or the entire section of an ancient artifact. This includes the support, one or more preparatory layer, and the surface. An important section of diagnostics is dedicated to assessing the presence, position, and extension of separation between these layers. The results of these examinations are translated into graphic documentation of discontinuities to achieve conservative diagnosis and outline a project of maintenance/intervention. From 2018 to the present, research has been underway for the development of an acoustic–electronic procedure for the qualitative analysis of the presence of detachment and debonding in ancient artifacts. This procedure and the probe that was expressly developed in this regard are called the “PICUS” (the Latin word for “woodpecker”) system. PICUS is an automatic system for detecting and measuring detachments and nonvisible defects in general. The experimental apparatus consists of a probe made of an electromechanical percussion element that gently taps the surface producing a sound, a force sensor purposely developed to measure the impact force, and a microphone, all connected to an Arduino‐like low-cost board, to record and elaborate sounds and the force sensor signal. The probe XY position on the scene is recognized using an infrared camera system. The PICUS system has been validated by traditional vibro-acoustic measures. So far, it has been tested on various models and materials and ancient techniques, from glazed tile covers to mosaics to wood panels.This chapter is divided into four paragraphs. First, we describe the phenomenon of detachment of ancient renderings according to the lexicon in the field of conservation, normalized to define the forms of alteration. Here, we narrow the field to the detachments that occur between different layers in rendering plasters or mosaic
bedding that employ lime as a binder. Then, we describe, from an acoustic point of view, the nondestructive testing (NDT) procedure in use by conservators and restorers for detachment diagnosis, according to the well-established procedure of tapping and listening. Other NDT techniques that can be successfully conducted in situ are briefly exposed. The complete PICUS system, hardware, software, and models for qualitative analysis of in situ detachments are then presented. Finally, we compare the results of two diagnostic techniques: the tapping technique traditionally used by conservators and restorers and the PICUS cross-correlation data processing algorithm. The maps obtained are compared, providing information on the effectiveness of the treatment and confirming the validity of the proposed method
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
Infrared spectra and ultraviolet-tunable laser induced photochemistry of matrix-isolated phenol and phenol-d5
No full textMonomers of phenol and its ring-perdeuterated isotopologue phenol-d(5) were isolated in argon matrices at 15 K. The infrared (IR) spectra of these species were recorded and analyzed. In situ photochemical transformations of phenol and phenol-d(5) were induced by tunable UV laser light. The photoproducts have been characterized by IR spectroscopy supported by theoretical calculations of the infrared spectra. The primary product photogenerated from phenol was shown to be the phenoxyl radical. The analysis of the progress of the observed phototransformations led to identification of 2,5-cyclohexadienone as one of the secondary photoproducts. Spectral indications of other secondary products, such as the Dewar isomer and the open-ring ketene, were also detected. Identification of the photoproducts provided a guide for the interpretation of the mechanisms of the observed photoreactions
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
Conformational Space and Photochemistry of Tyramine Isolated in Argon and Xenon Cryomatrixes
No full textThe infrared spectra of tyramine monomers trapped in low-temperature argon and xenon matrixes were recorded. The presence of the flexible ethylamino side chain gives rise to a complex conformational surface that contains several minima of relatively low energies, some of them stabilized by a weak N-H···pi hydrogen bond interaction between the amino group and the phenyl ring. The experimental infrared spectra confirm the presence of at least two stable conformers isolated in the matrixes. Annealing experiments performed on the xenon matrix revealed a change in the relative population of the experimentally relevant conformers upon isolation in this polarizable matrix, compared to the gas phase. The general interpretation of the spectra was based on harmonic and anharmonic quantum chemical calculations, undertaken at the DFT/B3LYP and MP2 levels of theory with the 6-311++G(d,p) basis set. The photochemical behavior of the matrix-isolated compound upon narrow-band UV irradiation was also investigated. Identification of ketene species in the spectra of the irradiated matrixes suggests the occurrence of a ring-opening reaction, which in the xenon matrix occurs concomitantly with the conformational isomerization of tyramin
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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