1,721,102 research outputs found
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Half-sandwich Anticancer Organometallics Derived from Triazolyl-imidazolium Ligands: From Different Coordination Modes to Heterobimetallic Compounds
No full textTo overcome the adverse effects and narrow pharmacological spectrum of traditional platinum anticancer agents, a large variety of metallodrugs have been investigated in the search for the next generation cancer therapeutics. Half-sandwich metal complexes are a class of compounds that have portrayed promising anticancer activity. Imidazole is an essential building block of molecules in medicinal chemistry, which is commonly featured in many biologically active compounds. The versatile heterocyclic scaffold enables the design and development of ligand systems suitable for metal coordination. Thionation of the C2 carbon or the alkylation of the endocyclic nitrogen atoms leads to the formation of N-heterocyclic thiones (NHTs) and N-heterocyclic carbene (NHC) ligand precursors, respectively, which were both investigated for their anticancer properties upon coordination to transition metals.
An extensive series of asymmetric NHT and NHC compounds derived from an imidazolium scaffold was developed, in which one of the endocyclic nitrogen atoms was alkylated with a methyl or methylpyridyl group, while the other has a pendant triazolyl moiety functionalised with a benzyl or methylferrocene group. The heterocyclic compounds functioned as mono- or multidentate ligand systems generating half-sandwich organometallic complexes of RuII, OsII, RhIII, and IrIII. When the pro-ligands were coordinated to metal centres, the resultant complexes formed pockets that hydrogen bond with the counterion. These pockets were established by the protons of the ligand near the metal centre.
Cytotoxicity assays revealed that the ligand precursors showed only moderate to low anticancer activity. Coordination to metal centres resulted in compounds with a varied degree of improvements in cytotoxicity. NHT complexes generally displayed low to moderate cytotoxicity, with the Ir derivative being moderately cytotoxic and accumulating in the cytoplasm of cancer cells. Conversion into the analogous Ir(NHC) derivatives did not result in significant enhancement in cytotoxicity. The low potency of the Ru- and Os(NHC) derivatives was accounted for by their slow to no reactivity with biological molecules. Replacement of the benzyl group with ferrocene significantly improved the cytotoxicity of the compounds and promoted the generation of reactive oxygen species (ROS) in cancer cells. Alternative coordination modes were investigated with the methylpyridine-derived NHC precursors, which resulted in the unexpected formation of bi- and tridentately coordinated Os and Rh complexes. However, the improvement in cytotoxicity was not as pronounced compared to ferrocene-functionalisation. The investigation of various ligand modifications and coordination modes laid the foundation for the determination of structure-(re)activity relationships of these classes of complexes featuring different imidazole-derived ligands
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Conjugation Strategies of the Anticancer Ruthenium Complex Plecstatin-1 to Tumour-targeting Peptides using Cleavable and Non-cleavable Linkers
No full textPeptide-drug conjugates (PDCs) have multifaceted applications and here they were explored as
potential chemotherapeutic agents based on the plecstatin compound class. These metal complexes
feature a pyridinecarbothioamide ligand (PCA) were explored as the payload in PDCs as they exhibit
potent anticancer activity. In this doctoral thesis, derivatives of the lead Ru complex plecstatin-1 were
synthesised which contained a functional handle for conjugation to peptides and to create metal-peptide
conjugates (MPCs) which can selectively deliver the plecstatin payload to cancer cells.
To obtain the desired MPCs several strategies were explored. The monodentate chlorido ligand of
plecstatin-1 was substituted for N-heterocycle and N-heterocyclic carbene (NHC) ligands as potential
conjugation handles. However, the Ru–N-heterocycle bond was too labile and resulted in dissociation
of the Ru(arene)(PCA) moiety from the peptides and the NHC-functionalised plecstatin complexes did
not yield the desired Ru complexes.
Alternatively, the η⁶ -arene ligand of plecstatin-1 was explored for functionalisation with a handle for
peptide conjugation by substituting it with L-phenylalanine (Phe) and p-methylbenzylamine.
Incorporation of the phenylalanine-derived plecstatin complex into peptides showed reduced stability
resulting in numerous side products, low yields and poor purity of the MPCs. The p-methylbenzylamine
functionalised plecstatin complexes were successfully conjugated to TAT, neurotensin (NT) and plectintargeting peptides (PTP) via a succinyl linker. The antiproliferative activity of the MPCs was significantly
reduced compared to the unconjugated Ru complex which, however, is common for many PDCs.
In attempts to improve the anticancer activity of the MPCs, the cathepsin B-activatable ValCitPABA
cleavable linker was installed into NT- and PTP-based MPCs. Unfortunately, the incubation of the MPCs
with cathepsin B did not result in the cleavage of the linker and therefore the metal complex was not
released. Consequently, they exhibited minor antiproliferative activity in in vitro anticancer activity
assays.
The developed methodology provides the foundations towards the preparation of novel approaches
towards MPCs. It facilitates the incorporation of metal piano-stool complexes into peptides as payloads
with cleavable and non-cleavable linkers. The functionalisation of the η⁶ -arene ligand allows for
conjugation of piano-stool metal complexes to other targeting vectors or biomolecules to improve their
biological properties
Ferrocene-derived Heterobimetallic Supramolecular Architectures: Synthesis, Guest Encapsulation and Stimulus-Responsive Studies
No full textMetallosupramolecular architectures are increasing in popularity due to their range of applications and ease of self-assembly. Many are able to readily change their shape and/or function in response to external stimuli and have the ability to encapsulate guest molecules within their internal cavities. As the majority of studies into homometallic stimuli-responsive supramolecular systems has focused on total disassembly of the architecture, this provided an opportunity to explore reversible partial disassembly and reassembly by which the entire host structure remains intact. As such, this project was centred on fashioning reversible stimulus-initiated heterobimetallic supramolecular structures whereby the structures would undergo partial disassembly when an external stimulus is applied and reassemble when the stimulus is removed.
Heterobimetallic [PdmLn]x+ complexes bearing symmetrical ferrocene-derived ligands through the formation of Pd–pyridyl bonds have been designed to allow for disassembly and reassembly. The formation of a series of PdL, PdL2 or Pd2L4 structures was possible through controlling the substitution pattern of the coordinating pyridyl rings. Cleavage of the relatively labile Pd–Npyridyl donor bonds, and subsequent disassembly of the supramolecular structure, was achieved through competitive ligand binding with N,N’-dimethylaminopyridine or a Cl- source to form PdCl42-. Triggering complex reassembly was successful for several complexes upon the addition of H+ or Ag+. Guest binding studies revealed interactions with several compounds with the anionic guests p-toluenesulfonate and octyl sulfate, and their binding constants were calculated based on 1H NMR spectroscopy experiments. Alternatively, dis- and reassembling structures can be obtained by introducing heteroditopic ligand systems. A ruthenium(II) heterobimetallic supramolecular structure bearing a non-symmetrically functionalised ferrocenyl ligand was designed to respond to the exposure and removal of light. Ru(II) complexes are well known for their ability to undergo photo-induced ligand ejection, in particular Ru–N bonds. The Ru(II) moiety was attached through a stable Ru–NHC (N-heterocyclic carbene) coordination bond on one arm of the ferrocenyl ligand and a more labile coordination to a pyridyl-triazole group on the other. While the final complex proved challenging to purify for light-responsiveness and guest binding studies, the synthetic routes towards the formation of the target ferrocenyl ligands and Ru(II) complexes are described in detail
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