1,721,030 research outputs found
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
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
Synthesis and bioanalytical characterization of new halogenated N-heterocyclic carbene gold(I) organometallic complexes as potential anticancer drugs and antibiotics
Full text linkIm Rahmen dieser Arbeit wurden neue NHC-Gold(I)komplexe mit den allgemeinen Strukturen NHC-Au-Cl und [NHC-Au-NHC]+I- erfolgreich synthetisiert und bezüglich ihres Potentials als neue Zytostatika und antibiotisch wirksame Arzneistoffe bioanalytisch untersucht.
Es konnten neue potente Gold(I)verbindungen in den möglichen Anwendungsgebieten der neoplastischen und antibiotischen Chemotherapie gefunden werden.
Die mono-NHC Gold(I)komplexe (NHC-Au-Cl) zeigten vor allem gegenüber grampositiven Bakterienstämmen im Mikroboullion-Verdünnungstest und im Enzyminihibitionstest der Thioredoxinreduktase von E.coli sehr gute selektive wachstumshemmende Effekte.
Die bis-NHC Gold(I)komplexe [NHC-Au-NHC]+I- wiesen dagegen eine stärkere antiproliferative Wirkung in den Zytotoxizitätstests an humanen Tumorzellen, als auch einen unterschiedlichen Wirkmechanismus auf.
Weiterhin wurde eine Korrelation zwischen der antiproliferativen Aktivität gegenüber verschiedenen Tumorzellen, der Lipophilie der Komplexe, der Affinität zu Serumalbumin und der Zellaufnahme aufgezeigt. Detaillierte Experimente zeigten, dass die mono- und bis-NHC Gold(I)komplexe unterschiedlich stabil sind und Zersetzungs- und Umlagerungsprozesse während der Zellaufnahme wahrscheinlich sind. Strukturwirkungsbeziehungen konnten im Anwendungsgebiet der neuen Zytostatika abgeleitet werden.
In beiden Anwendungsgebieten konnten die neuen Gold(I)-Organometallkomplexe die Aktivität der Leitstrukturen, als auch der Referenzsubstanzen (Auranofin und die Antibiotika Amikacin, Linezolid und Ciprofloxacin) übertreffen.Within the framework of this work, new NHC gold(I) complexes with the general structures NHC-Au-Cl and [NHC-Au-NHC]+I- were successfully synthesized and bioanalytically examined in terms of their potential as new anticancer drugs and antibiotics.
New potent gold(I) compounds for possible applications in neoplastic and antibiotic chemotherapy were identified.
Particularly the mono-NHC gold(I) complexes (NHC-Au-Cl) showed remarkable growth-inhibiting effects against Gram-positive bacterial strains in broth dilutions tests and enzyme inhibition studies of thioredoxin reductase from E. coli.
The bis-NHC gold(I) complexes [NHC-Au-NHC]+I- revealed stronger antiproliferative effects in human tumor cell lines and a different mode of action.
Furthermore, the correlation between the antiproliferative activity against various tumor cells, the lipophilicity of the complexes, the affinity to serum albumin and cellular uptake was demonstrated. More detailed experiments showed that the mono-NHC gold(I) complexes in comparison to the bis-NHC gold(I) complexes were not stable and that decompositions as well as structural rearrangements during the uptake processes are plausible. Structure-activity relationships in the field of anticancer drugs were derived.
In both application areas, the new gold(I) organometallic complexes surpassed the activities of the lead structures as well as the references (Auranofin and the antibiotics Amikacin, Linezolid and Ciprofloxacin)
Analytical and Biological Investigation of Novel Titanium(IV) and Platinum(II) Complexes as Potential Anticancer Agents
Full text linkNach Herz-Kreislauferkrankungen sind Krebserkankungen die zweithäufigste Todesursache in Deutschland. Trotz der guten medikamentösen Behandlungsmöglichkeit, besteht nach wie vor ein hoher Bedarf nach der Entwicklung alternativer Arzneistoffe mit einem andersartigen Wirkmechanismus.
Eine vielversprechende Alternative stellen antitumoraktive Titan(IV)-Komplexe mit Cyclopentadienyl- bzw. Salan-Liganden sowie neuartige Platin(II)-Komplexe mit Phenacetylid-Liganden dar. Über die biologischen Eigenschaften und das Target dieser neuen Substanzfamilien ist nur wenig bekannt, was im Hinblick auf deren möglichen Einsatz in der Tumortherapie zwingend notwendig ist. Deshalb wurden biochemische Untersuchungen zur Aufklärung des bisher unbekannten Wirkmechanismus der neuen Substanzfamilien durchgeführt. Dazu wurde eine auf der hochauflösenden Atomabsorptionsspektrometrie beruhende Analysemethode zur sensitiven Metallquantifizierung in biologischem Material entwickelt.
Die Titan(IV)-Komplexe zeigten abhängig vom gewählten Liganden ein unterschiedliches Verhalten bezüglich ihrer Toxizität, Affinität zu Biomolekülen (DNA, Serumalbumin) und intrazellulären Bioverteilung. Eine besonders hohe serumabhängige Zellaufnahme und eine Akkumulation in den Mitochondrien konnte für den Titankomplex mit Salan-Ligand beobachtet werden. Der Titankomplex mit Cyclopentadienyl-Ligand wies eine nur geringe Zellaufnahme, aber hohe Affinität zu Biomolekülen sowie eine Lokalisation in den Zellkernen auf.
Die erstmalige biologische Charakterisierung der neu synthetisierten Platin(II)-Alkinyl-Komplexe lieferte eine hohe antiproliferative Potenz gegen Tumorzellen. Im Hinblick auf eine Targetidentifizierung konnte die DNA als ein mögliches Zielmolekül identifiziert werden. Besonders vielversprechend ist außerdem die für Platinkomplexe bisher unbekannte hohe inhibitorische Aktivität der Platin(II)-Alkinyl-Komplexe gegen das Selenoenzym Thioredoxinreduktase, die einen andersartigen Wirkmechanismus vermuten lässt.After cardiovascular diseases the second leading cause of death in Germany is cancer. Despite there are several therapeutic options available, there is still a strong need to develop new pharmaceuticals that overcome the severe side effects and resistance phenomena of nowadays used anticancer drugs.
Titanium(IV) complexes with salan or cyclopentadienyl ligands and platinum(II) compounds with alkynyl ligands have shown a promising potential. For further development of these novel compound classes a chemical-biological evaluation was strongly needed. Therefore, their reactivity against biomolecules and enzymes, their cellular accumulation and distribution as well as their in vitro- and in vivo-toxicity was studied. In addition, a method to quantify metals in biological material using high-resolution continuum-source atomic absorption spectroscopy was developed.
The investigation of cytotoxic titanium(IV) complexes with a salan or cyclopentadienyl ligand indicated a very different biological behavior. The titanium compound with salan ligand showed low binding affinities to DNA and albumin but a high and serum dependent cellular accumulation as well as high titanium levels in mitochondria. In contrast, the titanium complex with cyclopentadienyl ligand afforded a generally lower cellular uptake with increased binding efficacy to biomolecules and a nuclear accumulation.
The biological investigation of platinum(II) complexes with alkynyl ligands revealed a high antiproliferative potency of this novel compound class against cancer cells. Furthermore, the DNA was identified as potential target. With respect to their properties as selective thioredoxin reductase inhibitors a different mode of action in comparison to known platinum based drugs was found.
Overall these results clearly demonstrate the high potential of novel titanium(IV) complexes with salan or cyclopentadienyl ligands and platinum(II) complexes with alkynyl ligands as potential anticancer agents
Gold(I) N-Heterozyklisch Carben Komplexe: Eine chemische und biologische Studie über das therapeutische Potential als neue Antikrebsarzneistoffe
Full text linkThe following PhD thesis dealt with gold(I) N-heterocyclic carbene complexes as innovative anticancer agents. The initial drug design was based on the chemical properties and bioactivity of a recent potent gold phosphol inhibitor: GoPI. A first series of complexes was synthesized and intensively biological investigated. Features such as the inhibition of enzymes of the antioxidant network (e.g. thioredoxin reductase), reactive oxygen species stimulation and apoptosis induction were observed. Moreover, the gold(I) complexes demonstrated an antiproliferative potential in the range of established anticancer drugs. Based on the results of the biological investigation, other two structure activity relationship series were synthesized and tested. A rational improvement in cytotoxic activity was observed. The chemical environment at the gold atom proved to be a key feature to achieve a specific bioactivity.
Overall, the results contributed to explain and characterized the biological profile of the gold(I) N-heterocyclic carbene complexes class.Die folgende wissenschaftliche Abhandlung befasst sich mit N-heterozyklischen Carben(NHC)- Gold(I)-Komplexen als innovative Antitumorwirkstoffe. Das Drug Design dieser neuartigen Komplexe basiert auf den chemischen und biologischen Eigenschaften eines bereits bekannten antitumorwirksamen Gold-Phosphol-Komplex „GoPI“. Es wurde eine Serie von neuartigen Gold(I)-Komplexen synthetisiert und deren biologischen Eigenschaften unter Einbeziehung der Enzyminhibition im antioxidativen Netzwerk, Bildung von reaktiven Sauerstoffspezies und Induktion von Apoptose untersucht. Zudem zeigten die synthetisierten Gold(I)-Verbindungen ein interessantes zytotoxisches Potential. Basierend auf diesen Ergebnissen und den gefundenen Struktur-Wirkungs-Beziehungen wurden zwei weitere Serien von NHC-Gold(I)-Komplexen synthetisiert und charakterisiert. Diese zwei Serien zeigten eine verbesserte Aktivität, was darauf hindeutet, dass die chemische Umgebung des Gold-Zentralatoms ein wichtiges Charakteristikum ist, um eine spezifische Bioaktivität zu erzielen
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