1,721,033 research outputs found
Robustness of solutions to the capacitated facility location problem with uncertain demand
Full text linkWe investigate the properties of robust solutions of the Capacitated Facility Location Problem with uncertain demand. We show that the monotonic behavior of the price of robustness is not guaranteed, and therefore that one cannot discriminate among alternative robust solutions by simply relying on the trade-off price-vs-robustness. Furthermore, we report a computational study on benchmark instances from the literature and on instances derived from a real-world application, which demonstrates the validity in practice of our findings
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
Chromatin Structure of the Human NK Cells Perforin Gene Promoter
No full textInnate immunity plays a vital role in host defense against viral infection and tumor development. Natural Killer (NK)cells are important for the earliest stage of immuneresponse, which occurs without prior sensitization. NK cells have the ability to kill malignant or infected cellsby releasing cytotoxic proteins contained in their cytoplasmic granules. . One of these proteins is the perforin which is responsible for forming pores in the target cell membrane. Although it is believed that the control of perforin expression occurs at the transcriptional level, the molecular mechanisms responsible for that control have not been completely characterized. Our aim is to understand whether this control is somehow related to the chromatin organization of its promoter. We started defining the chromatin organization of perforin promoter using NK cells derived from peripheral blood of healthy individuals: preliminary results indicate that the promoter region spanning the gamma-interferron responsive element is occupied by a positioned nucleosome particle. We are currently analyzing the chromatin structure of the perforin promoter following activation by cytokines treatment of the in vitro cultured cells. Moreover, a similar study has been undertaken on the promoter of the gamma-interferon gene
DNA topoisomerase I controls the kinetics of promoter activation and DNA topology in Saccharomyces cerevisiae.
No full textInactivation of the nonessential TOP1 gene, which codes for Saccharomyces cerevisiae DNA topoisomerase I, affects the rate of transcription starting at the ADH2 promoter. For both the chromosomal gene and the plasmid-borne promoter, mRNA accumulation is kinetically favored in the mutant relative to a wild-type isogenic strain. The addition of ethanol causes in wild-type yeast strains a substantial increase in linking number both on the ADH2-containing plasmid and on the resident 2 microns DNA. Evidence has been obtained that such an in vivo increase in linking number depends on (i) the activity of DNA topoisomerase I and of no other enzyme and (ii) ethanol addition, not on the release from glucose repression. A direct cause-effect relationship between the change in supercoiling and alteration of transcription cannot be defined. However, the hypothesis that a metabolism-induced modification of DNA topology in a eukaryotic cell plays a role in regulating gene expression is discussed
H4 acetylation does not replace H3 acetylation in chromatin remodeling and transcription activation of Adr1-dependent genes
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Chromatin remodelling during S. cerevisiae ADH2 gene activation
No full textWe have analyzed at both low and high resolution the distribution of nucleosomes over the Saccharomyces cerevisiae ADH2 promoter region in its chromosomal location, both under repressing (high-glucose) conditions and during derepression. Enzymatic treatments (micrococcal nuclease and restriction endonucleases) were used to probe the in vivo chromatin structure during ADH2 gene activation. Under glucose-repressed conditions, the ADH2 promoter was bound by a precise array of nucleosomes, the principal ones positioned at the RNA initiation sites (nucleosome +1), at the TATA box (nucleosome -1), and upstream of the ADR1-binding site (UAS1) (nucleosome -2). The UAS1 sequence and the adjacent UAS2 sequence constituted a nucleosome-free region. Nucleosomes -1 and +1 were destabilized soon after depletion of glucose and had become so before the appearance of ADH2 mRNA. When the transcription rate was high, nucleosomes -2 and +2 also underwent rearrangement. When spheroplasts were prepared from cells grown in minimal medium, detection of this chromatin remodeling required the addition of a small amount of glucose. Cells lacking the ADR1 protein did not display any of these chromatin modifications upon glucose depletion. Since the UAS1 sequence to which Adr1p binds is located immediately upstream of nucleosome -1, Adr1p is presumably required for destabilization of this nucleosome and for aiding the TATA-box accessibility to the transcription machinery
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