1,720,954 research outputs found
Chromosomes of the bowhead whale (Balaena mysticetus linnaeus)
Get PDFThesis (M.S.) University of Alaska Fairbanks, 1979The somatic chromosomes of the bowhead whale, Balaena mysticetus, are described for the first time using homogeneous staining and trypsin G-banding. The diploid chromosome number in all cells studied is 42. The bowhead karyotype retains many features of the general 2n = 44 cetacean karyotype from which it is derived, yet it is the first mysticete for which a chromosome number other than 2n = 44 has been reported. The advanced karyotype of the bowhead may reflect greater anatomical specialization of this whale than of other mysticetes. Cytogenetic data for cetaceans are reviewed within the framework of a model of speciation in sympatry
Cytogenetics and sex determination in collared lemmings
Get PDFDissertation (Ph.D.) University of Alaska Fairbanks, 1989Collared lemmings (Dicrostonyx groenlandicus rubricatus) from northeastern Alaska were found to have sex chromosomes that differ from those of their Siberian congeners, because of fusion to a particular pair of autosomes. But, as in Siberian lemmings, breeding experiments showed that sex determination involves an X-linked "male-repressor," which causes carriers to develop as fertile females, despite the presence of a Y chromosome. Genotypic frequencies in offspring are consistent with Mendelian expectations of such a system, hence natal sex ratios normally favor females. X-linkage of the male-repressor in Siberia and in Alaska indicates that the gene is probably located on the "original" arms of the X chromosome rather than on the fused autosomal arms, which differ on the two continents. One consequence of the autosomal fusion to the sex chromosomes is that deleterious recessive alleles on the autosome fused to the X chromosome are more resistant to selection than at truly autosomal loci. Another consequence is that, because males are heterozygous for loci fused to the sex chromosomes, they are more resistant to inbreeding depression than XX females. One inbred line produced a natal sex ratio of 67% males. The male-bias probably resulted from loss of the male-repressor and from a lethal carried on the formerly autosomal arm of the X chromosome. As inbreeding coefficients approached 0.3, the lethal would have been homozygous in half of the homogametic (female) zygotes. This phenomenon may explain the excess of males and XY females observed in earlier work. Also, if under the natural mating system, inbreeding depression limits fitness, then fusions of autosomal chromatin to the heterochromosomes could be an adaptation to reduce inbreeding depression in heterogametic individuals. Some other genetic features of collared lemmings do suggest endogamy. Female-biased sex ratios can evolve when mating occurs between neighboring individuals who are more related than if mating occurred randomly. Two proposed sources of such "viscous" gene flow in lemmings are cyclical changes in population density and mosaic habitat. Alternatively, could climate may favor winter aggregation and inhibit the dispersal of winter-born offspring, which would mature and mate with close relatives; dispersal and outbreeding would occur in summer. Thus, inbreeding would be seasonal rather than density-dependent and it is unnecessary to suppose discontinuous habitat
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
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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