1,721,013 research outputs found
Synthesis of cyclobutane-fused chromanones via gold-mediated photocatalysis
Full text linkEnergy transfer (EnT) photocatalysis has emerged as a valuable tool for constructing complex organic scaffolds via [2 + 2]-cycloaddition reactions. Herein, we present the use of [Au(SIPr)(Cbz)] as a sensitizer for the [2 + 2]-cycloaddition of coumarins and unactivated alkenes. Widely used in EnT catalysis, iridium and organic sensitizers proved less efficient under the examined catalytic conditions. The developed protocol permits the synthesis of cyclobutane-fused chromanones from readily available starting materials. A wide range of alkenes and substituted coumarins, including naturally occurring compounds, were reacted under mild conditions leading to structurally complex products with good functional group tolerance. Mechanistic studies reveal a previously overlooked reaction pathway for energy transfer catalysis involving coumarins
A simple synthetic entryway into new families of NHC-gold-amido complexes and their in vitro antitumor activity
No full textA simple synthetic pathway to Au-NHC amido complexes is described. Syntheses and isolation of [Au(NHC)((NRR2)-R-1)] complexes, bearing various NHC ligands and NH-containing heterocycles under mild conditions are reported. The in vitro anticancer activity of these gold-complexes was investigated on three human cancer cell lines. A number of these show comparable or even better antiproliferative activity than cisplatin. Noteworthy is the non-toxicity of most of the complexes on normal cells
Novel dinuclear NHC–gold(i)-amido complexes and their application in energy transfer photocatalysis
Full text linkThe development of efficient and operationally simple synthetic routes to dinuclear gold(i)-amido complexes bearing aromatic/aliphatic-bridges are reported. This family of complexes was prepared utilizing environmentally friendly and sustainable reagents under mild conditions, resulting in 68-92% yields of the targeted compounds. These novel dinuclear gold(i)-amido complexes were structurally and spectroscopically characterized. Their photophysical properties were also studied. This series of gold complexes are phosphorescent with lifetimes in the hundreds of microseconds range. They exhibit high catalytic activity as photosensitizers in intramolecular cycloaddition and cyclization reactions at catalyst loadings ranging from 0.5 to 2 mol%
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
Collective Countermeasures in Response to Cyber Operations under International Law
No full textThe paper examines the application of collective countermeasures — i.e., measures taken by non-injured states — as a means of cooperative non-institutionalized response to malicious cyber-enabled activities undertaken or controlled by a state. Particularly, the paper investigates: the right of the state not injured by a cyber operation to take countermeasures against the perpetrating state under current international law; and state positions towards collective countermeasures and possible grounds for the development of a more supportive attitude within states to this form of collective reaction. General research and special legal methods, as well as game theory, are employed to test the hypothesis the concept of collective countermeasures has been gaining nascent and fragmented support by states in terms of its applicability in the context of cyber operations. The author concludes this emerging trend reflects the general tendency of states to join forces to halt malicious activities in cyberspace and impose political and economic costs upon the perpetrators. This allows one to assume that collective countermeasures in response to cyber operations might become an expectable means of reaction by ‘like-minded’ states. Their legitimation might, therefore, be determined not only (or not so much) by the development of international law due to the practical difficulty in harmonizing positions among states on this issue at the current stage, but rather as a part of the general political trend of uniting the efforts of states to bring wrongdoers in cyberspace to responsibility.The paper examines the application of collective countermeasures — i.e., measures taken by non-injured states — as a means of cooperative non-institutionalized response to malicious cyber-enabled activities undertaken or controlled by a state. Particularly, the paper investigates: the right of the state not injured by a cyber operation to take countermeasures against the perpetrating state under current international law; and state positions towards collective countermeasures and possible grounds for the development of a more supportive attitude within states to this form of collective reaction. General research and special legal methods, as well as game theory, are employed to test the hypothesis the concept of collective countermeasures has been gaining nascent and fragmented support by states in terms of its applicability in the context of cyber operations. The author concludes this emerging trend reflects the general tendency of states to join forces to halt malicious activities in cyberspace and impose political and economic costs upon the perpetrators. This allows one to assume that collective countermeasures in response to cyber operations might become an expectable means of reaction by ‘like-minded’ states. Their legitimation might, therefore, be determined not only (or not so much) by the development of international law due to the practical difficulty in harmonizing positions among states on this issue at the current stage, but rather as a part of the general political trend of uniting the efforts of states to bring wrongdoers in cyberspace to responsibility
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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