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Photochemistry: Volume 44
No full textThe E-Z photoisomerization of azobenzene - owing to its high efficiency, excellent reversibility and significant physico-chemical differences between the two forms - is highly interesting for the construction of photocontrollable molecular systems and materials. In this chapter we illustrate how this outstanding photoreactivity can be utilized to develop (supra)molecular systems and materials with valuable light-induced functionalities by presenting some investigations carried out in our laboratory
Set photochemical reactions between 1,4-naphthalenedicarbonitrile and benzylic donors. Medium effects
No full textThe electron transfer induced photochemical reactions of 1,4-naphthalenedicarbonitrile (NDN) with
toluene (la),d iphenylmethane (lb),p-methoxytoluene( IC)a, nd benzyltrimethylsilane (Id) in MeOHMeCN
and 0.1 M KOH-MeOH-MeCN were examined. The results were compared with those of
reactions occurring in neat MeCN. Under the former conditions, the cation radical derived from
la undergoes deprotonation after diffusion from (rather than within) the geminate ion pair (as in
MeCN). The formed benzyl radical abstracts a hydrogen from MeOH leading to hydroxymethylation
of NDN competitively with its benzylation. Under basic conditions MeO- adds to la+' yielding IC.
Thereaction of lb in MeOH-MeCN and 0.1 M KOH-MeOH-MeCN is similar to that of la. However,
in the reaction of IC under these conditions, the arene cation radical undergoes deprotonation out
of cage. Finally, desilylation of the cation radical from Id is a fast process occurring from the
geminate pair in all the media explore
TOMATO KNOTTIN TCMP-1 PLAYS A ROLE IN CADMIUM TOLERANCE
No full textKnottins or cystine-knot miniproteins (CMPs) are a class of cysteine (Cys)-rich proteins identified in eukaryotes. They are characterized by a very small size and by the presence of a C-terminal knot domain with six conserved Cys forming three disulfide bonds, conferring stability and resistance to high temperatures, proteolysis and chemical chaotropic agents. In plants, members of the knottin family participate in defense against pathogens and herbivores acting as inhibitors of proteases or amylases or displaying antimicrobial and insecticidal properties (Daly & Craik, 2011). Moreover, knottins have been found as associated with nickel (Ni) tolerance in a Ni-hyperaccumulator ecotype of Noccaea caerulescens (Halimaa et al., 2014) and with cadmium (Cd) accumulation in tobacco (Harada et al., 2010). Due to their biological activity, knottins have been considered for their potential application for therapeutical purposes: in particular, two tomato CMPs, TCMP-1 and TCMP-2, are able to inhibit angiogenesis without affecting endothelial cell proliferation and viability, both in vitro and in vivo, and to reduce cell migration (Treggiari et al., 2015). In tomato plants, TCMP-1 and TCMP-2 expression is strictly regulated and associated with flower buds before anthesis and ripe fruits, respectively. This evidence, as well as the earlier fruit setting observed when perturbing TCMP-1 expression, indicate a role in fruit development (Molesini et al., 2018)
Photochemical reaction between 1,4-naphthalenedicarbonitrile and a-substituted benzylic derivatives
No full textThe photochemical reaction of 1,4-naphthaIenedicarbonitrile (NDN) with benzylic derivatives of the general formula
PhCHRX (R = H, Ph; X = H, C, 0, S, Si, Sn-bonded substituents) has been investigated. The competition between C-H
and C-X bond cleavage in the photochemically created radical cation PhCHRX" is revealed by the different chemical products
formed, viz. 5,1l-methanodibenzo[a,e]cyclooctenes (2), from proton transfer and coupling of the radicals within the cage,
and 2-benzyl- (3) and 1-benzyl-I ,2-dihydronaphthalenes (4), as well as 4-benzyl-1-naphthalenenitriles (5), from the reaction
between the radical anion NDN'- and the neutral radicals PhCHR' or PhCRX'. With the alcohols, the hydroxylic proton
is easily transferred. Measurement of reaction quantum yield and fluorescence quenching and thermochemical calculations
support the mechanism propose
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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