1,721,011 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
Spindle Orientation Coordinates Cell Fate Decisions During Epidermal Morphogenesis
No full textAsymmetric cell divisions (ACDs) drive cell fate specification and the formation of complex tissue architecture. This often requires orienting the mitotic spindle to position daughter cells and/or segregate cell fate determinants. However, the mechanisms that properly position the mitotic spindle and link spindle orientation to cell fate specification are not fully understood. During mouse embryogenesis, oriented divisions drive epidermal morphogenesis. Disrupting oriented divisions results in differentiation defects, loss of barrier function, and lethality. ACDs have also been observed during hair follicle morphogenesis and have been suggested to produce specific populations of hair follicle cells, though this has not been directly tested. In the developing epidermis, spindle orientation requires a conserved cortical protein complex of LGN/NuMA/dynein-dynactin. This complex is thought to function by generating pulling forces on astral microtubules. However, the factors that regulate astral microtubule dynamics and their association with this cortical complex have not been well studied.
In this work, I explored the role of the microtubule catastrophe factor KIF18B in regulating microtubule dynamics to promote spindle orientation in keratinocytes. Utilizing two individually isolated control and KIF18B knockout (KIF18BKO) cell lines, I demonstrated that KIF18B is required for spindle alignment in cultured keratinocytes. Mitotic spindles in KIF18BKO cells exhibited an increase in both the length and number of astral microtubules. Microtubules more frequently touched the cortex in KO cells than in control cells. Furthermore, live-imaging revealed that loss of KIF18B dramatically altered microtubule dynamics; astral microtubules of KIF18BKO cells showed an increase in growth lifetime and growth displacement compared to controls. KIF18B’s regulation of microtubules was restricted to the astral microtubules, which is of note, as these are the microtubules that interact with the cell cortex as well as the spindle orientation machinery. I propose that KIF18B promotes astral microtubule catastrophe, which is essential to maintain proper microtubule dynamics and orient the mitotic spindle.
Unexpectedly, I discovered that KIF18B accumulates at the cell cortex during mitosis, colocalizing with the conserved spindle orientation machinery. This cortical localization has not been previously reported. KIF18B cortical localization mimicked that of NuMA. During metaphase, KIF18B polarized to one side of the cell cortex. However, during anaphase, KIF18B became bipolar and expanded along the cell cortex. This localization pattern was NuMA-dependent in both metaphase and anaphase and did not require microtubules.
In vivo I found that KIF18B was required for oriented cell divisions within the hair placode, the first stage of hair follicle morphogenesis, but was not essential in the interfollicular epidermis. Disrupting spindle orientation in the placode, using mutations in either KIF18B or NuMA, resulted in aberrant expression of Sox9, which serves as a cell fate marker of the inner region of adult hair follicle cells. Additionally, I showed that treatment of mice with Wnt inhibitors phenocopied the abnormal Sox9 expression seen in ACD mutants. These data lead me to hypothesize that asymmetric segregation of Wnt regulators plays a role in asymmetric cell division of basal placode cells.
My data functionally link spindle orientation to cell fate decisions during hair follicle morphogenesis for the first time. Taken together, my data demonstrate a role for regulated microtubule dynamics in spindle orientation in epidermal cells. My work also highlights the importance of spindle orientation during asymmetric cell division to dictate cell fate specification.
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Determining the role of Xist long noncoding RNA in hematopoiesis and hematologic malignancies
No full textX chromosome inactivation (XCI) is a mammalian dosage compensation phenomenon by which expression of X-linked genes is equalized between females and males. Initiation of XCI depends on Xist long noncoding RNA (lncRNA), which triggers transcriptional silencing of one of the two X chromosomes in female cells, except for genes that escape XCI. The inactive state of the X chromosome is maintained throughout subsequent cell divisions with continuous Xist expression. Proper maintenance of XCI in somatic cells is essential for female health, and its disruption has been observed in many diseases. However, whether Xist is required for maintaining XCI and how XCI alterations lead to diseases still remain open questions. Emerging evidence has revealed that the hematopoietic system consists of cells with variable XCI patterns and is highly sensitive to Xist depletion. This makes the hematopoietic system a good model for studying the functional role of Xist during XCI maintenance. By deleting Xist in hematopoietic stem cells (HSCs) of mice, I showed that Xist loss leads to lineage-specific cell cycle and differentiation defects in hematopoietic progenitor cells of female mice. At the molecular level, I showed that Xist loss results in upregulated expression of several X-linked genes, large proportion of which are XCI escape genes. In addition, many transcriptionally upregulated X-linked genes have been implicated in cell cycle- and immune-related functions. Furthermore, transcriptional upregulation of X-linked genes in Xist-deficient cells is accompanied with a series of epigenetic changes on the inactive X chromosome (Xi) including reduced density of repressive histone marks, increased density of active histone modifications, and enhanced chromatin accessibility which accommodates increased binding of a transcription factor, Ying Yang 1 (YY1). Collectively, these findings suggest a critical role of Xist in regulating expression level of X-linked genes with essential hematopoietic functions during XCI maintenance.</p
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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