1,721,010 research outputs found
The effect of the 4-amino functionality on the photophysical and DNA binding properties of alkyl-pyridinium derived 1,8-naphthalimides
No full textThe synthesis and characterisation of two cationic pyridinium based 4-amino-1,8-naphthalimide derivatives ( and ) are described and compared to those of compound . The photophysical properties of and are shown to vary greatly with the solvent polarity and H-bonding ability. The dimethylamino substitution in results in a weak quantum yield of fluorescence emission due to faster non-radiative deactivation of the excited singlet state than that seen for . As with , the fluorescence of was found to be enhanced in its 1:1 complex with 5'-adenosine-monophosphate (5'-AMP) while it was partially quenched in its complex with 5'-guanosine-monophosphate (5'-GMP). In contrast, the fluorescence of was enhanced ('switched on') in the presence of both adenine and guanine rich sequences. Linear and circular dichroism studies showed that each of , and binds to double-stranded DNA by intercalation. However, and do not show the preference for AT-rich DNA observed for . Comparative fluorescence studies with double stranded DNA show that the emission of was 16 times enhanced in its DNA bound form, suggesting potential use of this structure as a spectroscopic probe for studying nucleic acid structure
Synthesis and photophysical evaluation of a pyridinium 4-amino-1,8-naphthalimide derivative that upon intercalation displays preference for AT-rich double-stranded DNA
No full textThe synthesis, characterisation and solid state crystal structure of a cationic 4-amino-1,8-naphthalimide derivative (1) are described. The photophysical properties of 1 are shown to vary with the solvent polarity and H-bonding ability. The fluorescence of 1 is enhanced and blue-shifted in its 1:1 complex with 5?-adenosine-monophosphate while it is partially quenched and red-shifted in its complex with 5?-guanosine-monophosphate. Linear and circular dichroism measurements show that 1 binds to double-stranded DNA by intercalation. Comparative UV-visible and fluorescence studies with double stranded synthetic polynucleotides poly(dA–dT)2 and poly(dG–dC)2 show that 1 binds much more strongly to the AT polymer; 1 also has a strong preference for A–T rich sequences in natural DNA. Thermal denaturation measurements also reveal a much greater stabilisation of the double-stranded poly(dA–dT)2 than of natural DNA
A DISAGGREGATED TIME-SERIES ANALYSIS OF EXPORT-BASE MODELS: A CASE STUDY ON ELKO COUNTY OF NEVADA
Full text linkAn important issue of debate in economic base literature is whether the export-base theory applies best to the short run, the long run, or both. An attempt is being made here in answering this crucial question by applying a two-step test for cointegration on quarterly employment data, and in gaining insights as to whether or not any unequivocal judgment can be made regarding the validity of the economic base hypothesis.International Relations/Trade,
Synthesis, spectroscopic and biological studies of a fluorescent Pt(ii) (terpy) based 1,8-naphthalimide conjugate as a DNA targeting agent
No full textThe bi-functional complex [PtII(terpy)(py-naphth)](NO3)2(1), incorporating both 2,2':6',2"-terpyridine and 4-N,N'-dimethylamino-1,8-naphthalimide moieties, displays a high binding affinity for DNA as well as displaying cytotoxicity towards and inducing apoptosis in malignant cell lines
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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