1,721,157 research outputs found
The effect of initial linkage disequilibrium and natural selection in pooled populations : experiments with Tribolium and simulation
No full textIn chapter 2 a number of the mechanisms are discussed through which genetic polymorphisms can be maintained in natural populations: overdominance, frequency dependent selection and neutral alleles with associative overdominance. The overdominance model is emphasized because overdominance is also the basic feature of the associative overdominance model. Different theoretical relationships between number of heterozygous loci and fitness are explored, including their implications with regard to mean population fitness and selection coefficients at individual loci in an ideal population. From these, King's threshold model for multiple gene action on fitness proved to be the most satisfactory in all respects: it accomodates fairly high selection coefficients at individual loci without implying too heavy a load; it further explains different inbreeding depressions for different organisms and for different environments, as well as genotype by environment interaction. The model of associative overdominance, with the incorporation of King's threshold model for multiple gene action, has been chosen as an operational hypothesis for explanation of my experimental results (chapter 3) and as a basis for the simulation study (chapter 4).Chapter 2 further discusses the implications of associative overdominance (which is a result of overall linkage disequilibrium in finite populations) when linkage disequilibrium is generated artificially by using a small sample to found a new population. In this situation pseudo-frequency dependent selection is expected to occur at selectively neutral loci. An experimental design is proposed which distinguishes between apparent and real frequency dependent selection.Chapter 3 presents the experiments: individuals from two laboratory stocks of Tribolium castaneum HERBST, together with their F 1 , were used to initiate a set of polymorphic populations (for the black locus) with different frequencies of the marker allele. These experiments, jointly taken, indicate that the black locus itself is selectively neutral under the current experimental conditions and rule out the possibility of real frequency dependent selection. There was however apparent selection against the mutant allele due to initial linkage disequilibrium. This linkage disequilibrium is described in terms of the different genotypic backgrounds of the components (wild type and mutant stock and F 1 ) of the founder population: in the mutant stock there is an excess of homozygosity which may be randomly distributed over the chromosomes or may be partially or wholly concentrated in a chromosome region near the marker locus. This confirms the expectation formulated in the Introduction (chapter 1). The initial linkage disequilibrium, in these experiments is not so much due to small samples from the founder stocks as to the different genotypic backgrounds of the founder stocks, and, with respect to neutral loci, implies associative dominance rather than associative overdominance. The apparent decrease in selection against the b allele is a result of the approach to linkage equilibrium.A comparison of the fitness differences among the original marker genotypes (wild type, mutant black and F 1 ) on the one hand and the marker genotypes of an F 2 population on the other band, showed that the fitness loci closely linked to the marker locus and the joint non-linked fitness loci made approximately equal contributions to the fitness contrast between the two founder stocks (i.c. a lower fitness of the mutant stock). It also showed that, under the current experimental conditions, differential viability only played a minor role, if any, in the gene frequency changes of the b allele in the pooled populations.Chapter 4 presents a computer model for (stochastic) simulation of the population experiments. This model is based on the hypothesis of overdominance at the chromosomal level and on the assumption that only the marker chromosome contributes to the fitness difference between the founder stocks. For this purpose FRASER'S technique of binary representation of genotypes was adopted.After correction for some discrepancies between the simulation model and the experiments (in the simulation only the marker chromosome is considered and selection acts through differential viability), the results of simulation proved to be in fairly good agreement with the experimentally obtained results. The simulation model can readily be adapted to other situations, e.g. both founder stocks being 'inbred', tracking the gene frequencies at more than one neutral locus, and any arbitrary function relating the number of heterozygous loci to fitness.The final conclusion from both the experiments and the simulation study is, that after introducing the relatively 'inbred' mutant stock into the wild type population, a great deal of the genetic material of the mutant stock is lost by natural selection. For practical breeding this implies a risk of losing part of the genetic material, as a result of natural selection, from small samples of (relatively) inbred populations which are introduced into a breeding stock. Of course, the breeder may artificially select in favour of a fitness-neutral character introduced by the 'fresh' genetic material; however, the effect of artificial selection may be greatly reduced when (in the initial generations) natural selection outweighs artificial selection, since natural selection 'acts' against the desired character through linkage disequilibrium with fitness loci
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
Author Under Sail The Imagination of Jack London, 1893-1902
No full textIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Intro -- Title Page -- Copyright Page -- Dedication -- Contents -- Acknowledgments -- Introduction -- 1. Spirit Truth -- 2. From Absorption to Theatricality and Back Again -- 3. "I Will Build a New Present" -- 4. Sons as Authors -- 5. Fathers as Publishers -- 6. The Daughter as Author -- 7. Lovers as Authors -- 8. At Sea with the Family -- 9. Yellow News, Yellow Stories -- 10. The Return Home -- Notes -- Bibliography -- Index -- About Jay WilliamsIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Description based on publisher supplied metadata and other sources.Electronic reproduction. Ann Arbor, Michigan : ProQuest Ebook Central, YYYY. Available via World Wide Web. Access may be limited to ProQuest Ebook Central affiliated libraries
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