1,721,040 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
Untersuchungen zur Synthese und biochemischen Charakterisierung von subtypselektiven Inhibitoren der humanen Histondeacetylasen HDAC8 und 10
Full text linkKrebs ist eine Krankheit deren Therapie mit Nebenwirkungen und schlechten Prognosen verbunden ist. Somit ist die Erforschung neuer Therapien wichtig. Diese Arbeit leistet ihren Beitrag auf diesem Gebiet, durch die Entwicklung potenter Inhibitoren gegen die Histondeacetylasen HDAC8 & 10. HDACs spielen bei der Entstehung und dem Lebenszyklus verschiedener Krebszellen eine Rolle. Studien haben gezeigt, dass eine HDAC-Inhibition ein vielversprechender Ansatz zur Therapie diverser Tumorerkrankungen ist. In dieser Arbeit wurden potente und selektive Inhibitoren gegen HDAC8 & 10 synthetisiert, biochemisch charakterisiert und hinsichtlich ihrer Struktur-Wirkungs-Beziehungen untersucht. Die aktivsten und selektivsten Derivate wurden an ausgewählten Neuroblastom- (HDAC8) und Leukämiezellen (HDAC10) getestet und stellten sich hier als vielversprechende Kandidaten heraus. Ebenso wurden die synthetisierten Inhibitoren in Zytotoxizitätsassays an humanen HEK293 Zellen als nicht-toxisch klassifiziert.Cancer is a disease that affects more and more people, and the treatment is associated with side effects and partially poor prognoses. Therefore, it is important that new therapies are researched. This work contributes to this field by developing potent inhibitors for the histone deacetyases HDAC8 & 10. HDACs play a significant role in the development and life cycle of several cancer cells. Previous studies have shown that the inhibition of distinct HDACs is a promising approach for chemotherapy of various types of tumor diseases. In this work potent and selective HDAC8 and HDAC10 inhibitors were synthesized, biochemically characterized and examined concerning to their structure-activity relationships. The most active and selective derivatives were tested on selected neuroblastoma (HDAC8) and leukemia (HDAC10) cells and turned out to be potent and promising candidates. In addition, the synthesized inhibitors were classified as nontoxic in cytotoxicity assays using human HEK293 cells
New insights into the allosteric regulation of Arabidopsis PI4Kβ1 and effects of phosphorylation on protein function
Full text linkPhosphatidylinositol 4-kinase β1 (PI4Kβ1) is a key enzyme in plant phosphoinositide biosynthesis and mediates the ATP-dependent conversion of phosphatidylinositol (PI) to PI 4-phosphate (PI4P). The aim of this study was to describe the biochemical properties of PI4Kβ1, to clarify its orientation towards the membrane, and to characterize the effects of previously described phosphorylation events. In vitro activity tests with purified MBP-PI4Kβ1 protein showed a sigmoidal kinetic profile with increasing concentration of the substrate PI, indicating allosteric regulation of the enzyme. For the cosubstrate ATP, on the other hand, a hyperbolic kinetic behavior of PI4Kβ1 was determined. Using a 3D model, a C-terminal helix of the protein may interact with membrane lipids. The influence of this helix on the kinetic behavior of PI4Kβ1 as well as that of various MAP-kinase-mediated phosphorylation sites is also described
Kombination chemischer und enzymatischer Methoden zur regiospezifischen Modifizierung von Proteinen
Full text linkDie vorliegende Dissertationsschrift beschäftigt sich mit der Etablierung eines chemo-enzymatischen Verfahrens zur regiospezifischen und chemoselektiven C- und N-terminalen Modifizierung von Proteinen. Hierbei wurde die bereits etablierte Trypsiligase verwendet, um chemisch weiter modifizierbare Funktionalitäten auf enzymatischem Wege in Proteine einzubringen. Als Funktionalitäten dienten hierbei Azid-, Alkin-, Alken- oder Tetrazinderivate, die im Zuge einer bioorthogonalen Cycloadditionsreaktion entsprechend derivatisiert werden konnten. Somit konnte im Rahmen einer C-terminalen Modifikation ein Antikörperfragment mit Mertansin, einem Cytostatikum, versehen werden. Darüber hinaus konnte die Prolyl-cis-trans Isomerase Cyclophilin mit Hilfe dieses Verfahrens N-terminal mit einem Dansylfarbstoff versehen werden.The present thesis deals with the establishment of a chemo-enzymatic method for the regiospecific and chemoselective C- and N-terminal modification of proteins. Here, the already established trypsiligase was used to introduce further chemically modifiable functionalities into proteins by enzymatic means. The functionalities used here were azide, alkyne, alkene or tetrazine derivatives which could be correspondingly derivatized in the course of a bioorthogonal cycloaddition reaction. Thus, in the context of a C-terminal modification, an antibody fragment could be provided with mertansine, a cytostatic agent. The prolyl cis-trans isomerase cyclophilin could be provided with a dansyl dye at the N-terminus using this method
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