1,721,046 research outputs found
Discriminating between the UV-A, UV-B and UV-C regions by novel Biologically Inspired Photochromic Fuzzy Logic (BIPFUL) systems: a detailed comparative study
No full textThis work presents the analysis of the deterministic part of human colour perception at the computational,
algorithmic and implementation levels. At the computational and algorithmic levels, we invoke
the theory of Fuzzy sets. At the implementation level, we present Biologically Inspired Photochromic
Fuzzy Logic (BIPFUL) systems that are useful to discriminate between the three regions of the UV
spectrum (UV-A, UV-B and UV-C). Such BIPFUL systems have been devised by imitation of the human
photosensitive system on retina. After transforming the absorption spectra, originated by the BIPFUL
systems under UV-A, UV-B and UV-C, in chromaticity coordinates and vectors in CIE L*a*b* spaces, we
have compared their performances through the determination of two parameters: The Colourability and
the Eucledian distance. Finally, the guiding principles for the design of new BIPFUL systems are outlined
Extending Human Perception of Electromagnetic Radiation to the UV Region through Biologically Inspired Photochromic Fuzzy Logic (BIPFUL) Systems.
No full textPhotochromic Fuzzy Logic Systems have been designed that extend human visual perception into the UV region. The systems are founded on a detailed knowledge of the activation wavelengths and quantum yields of a series of thermally reversible photochromic compounds. By appropriate matching of the photochromic behaviour unique colour signatures are generated in response differing UV activation frequencies
Ring contraction during the 6π-electrocyclisation of naphthopyran valence tautomers
No full textThe thermal and photochemical ring-opening of spiro(3H-naphtho[2,1-b]pyran-3,9′-thioxanthene-10,10-dioxide) 3 results in the facile ring-contraction to 9-(naphtho[2,1-b]furan-2-yl)-9H-thioxanthene-10,10-dioxide 6. Similar behaviour is displayed by the isomeric spiro(2H-naphtho[1,2-b]pyran-2,9′-thioxanthene-10,10-dioxide) 9 affording 9-(naphtho[1,2-b]furan-2-yl)-9H-thioxanthene-10,10-dioxide 12, though more severe reaction conditions were required. The comparative ease of this rearrangement for the isomers 3 and 9 was rationalised on the basis of the relative isomer populations of the ring-opened naphthopyrans. The rearrangement of simple mono- and bis-methylsulfonylphenyl substituted photochromic naphthopyrans 18, 20 was examined; the former failed to rearrange whereas the latter could be induced to rearrange only under prolonged UV irradiation. The photochromism of diastereoisomerically pure sulfoxides derived from the oxidation of spiro(3H-naphtho[2,1-b]pyran-3,9′-thioxanthene) 2a and spiro(2H-naphtho[1,2-b]pyran-2,9′-thioxanthene) 2b resulted in conversion to the most thermodynamically stable trans-isomer in each case
Synthesis and cycloadditions of 9H-furo [3,4-b][1]benzo(thio)pyran-9-ones: furan ring formation by a novel hydrolytically induced cycloreversion
No full textC-2 lithiation of acetals 2 followed by trapping with aldehydes gives 3. Subsequent unmasking of the acetal function provides furobenzo(thio)pyrans 4, cycloadditions of which have been investigated
Synthesis and photochromic properties of some fluorine-containing naphthopyrans
No full textA series of novel naphthopyrans containing fluorine substituents has been prepared and their behaviour following irradiation with UV light has been investigated. The colourless naphthopyrans exhibit photochromism through electrocyclic opening of the pyran ring. The spectral properties of the resulting coloured naphthalene-based dienones are discussed
Synthesis and photochromic properties of substituted 3H-naphtho [2,1-b] pyrans
No full textThe synthesis and spectroscopic properties of novel 3H-naphtho[2, 1-b]pyrans are described. Subtle variation of the colour of the photo-generated merocyanine dyes derived from these naphthopyrans can be accomplished by controlling the steric interactions between a terminal pyrrolidine donor group and a proximal substituent
Observations on the synthesis of photochromic naphthopyrans
No full text1-Naphthol reacts with 1,1-diarylprop-2-yn-1-ols 5a,b, under alumina catalysis, by two pathways to give the photochromic naphtho[1,2-b]pyrans 6a,b, together with the propenylid-enenaphthalenones 7a,b, representatives of a new class of merocyanine dyes. With 2-methyl-1-naphthol, formation of the photochrome is suppressed; the only products are merocyanines 7c,d. The cyclocondensation of 2-naphthol with 5a,b proceeds much more efficiently, to give the naphtho[2, 1 b]pyrans 14a,b. Pyran formation is not suppressed from either 1-bromo- or 1- (4-methoxyphenyl)-2-naphthol; reaction with 5a,b merely results in expulsion of the C-1 substituent. An alternative pathway supervenes in the reaction of 1-methyl-2-naphthol with 5a to give the benz[e]indanone 17, the constitution of which was determined by X-ray crystallography. Reaction of the 1,3,3-triarylpropynols 19a,b with 1-naphthol affords the naphthopyrans 20 together with merocyanines 21, whilst the isomeric pyrans 23 are efficiently produced from 2-naphthol. The configuration of merocyanines 7a and 21 a was unequivocally established by X-ray crystallography
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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