1,721,546 research outputs found
NCCALL Information Sheet
No full textDavies Graham Michael. NCCALL Information Sheet. In: Cahiers de l'APLIUT, volume 7, numéro 2, 1987. Actes du IXe Congrès – Sèvres, mai 1987 : Du Théâtre à l’ordinateur. pp. 49-57
Description of programs (présentation, utilisation et évaluation de logiciels pour l'apprentissage des langues)
No full textDavies Graham Michael, Staddon Sally. Description of programs (présentation, utilisation et évaluation de logiciels pour l'apprentissage des langues). In: Cahiers de l'APLIUT, volume 7, numéro 2, 1987. Actes du IXe Congrès – Sèvres, mai 1987 : Du Théâtre à l’ordinateur. pp. 44-48
Predation on polymorphic prey : the effects and behavioural bases of frequency-dependent and frequency-independent selection
No full textApostatic selection (frequency-dependent selection by predators) has been demonstrated in several studies and theoreticaa work indicates that it has the potential to maintain polymorphism. Although apostatic selection has been proposed as a process that may help maintain colour polymorphisms in molluscs such as Cepaea and Littorina there is little evidence to support this. The underlying behavioural basis of apostatic selection is also poorly understood. The experiments described in this thesis attempted to establish: (1) whether predators exert frequency-independent visual selection on visually polymorphic molluscs and which factors affect the degree and direction of selection, (2) whether predators could exert apostatic selection on artificial populations of Cepaea and Littorina, (3) the behavioural mechanism underlying apostatic selection. A two year field study of snail predation by song thrushes (Turdus pilomelos) revealed selection on the colour morphs of Cepaea. During the winter yellow five-banded morphs were at a selective advantage and pink unbanded at a disadvantage. Yellow five-banded morphs were also at a selective advantage in the summer as were yellow unbanded morphs, whilst morphs with fused bands were at a disadvantage. No significant changes in selection were observed in either predation period. An experiment was carried out to test whether captive song thrushes would feed in an apostatic manner on an artificial dimorphic population of Cepaea. Although the results gave some indication that selection was frequency-dependent they were not conclusive, because of the small number of replicates. Another experiment tested whether shore crabs (Carcinus maenas) exert frequency-independent visual and/or apostatic selection on an artificial dimorphic population of Lottirina mariae. The results indicated that there was no visual or apostatic selection. Some potential behavioural mechanisms causing apostatic selection were investigated using humans as `predators'. In the first series of experiments `populations' of dimorphic `prey' (at one of seven frequencies) were presented on the screen of a computer colour monitor to subjects who were asked to use a light pen to remove each prey they detected. Each subject either had the prey presented against a matching background or against a background that made them conspicuous. The results showed that apostatic selection occurred, but only when the prey were inconspicuous. The results also showed that the apostatic selection was caused by some aspect of the subjects' searching behaviour. Further experiments revealed that the overall degree of selection decreased with increasing density, although the individual effects on the frequency-dependent and frequency-independent components could not be established. A second series of computer trials explicitly tested whether humans formed search images or modified their search rate when searching for cryptic prey images. In these experiments cryptic prey were presented singly amongst a series of blank screens and the subjects only had to detect whether a prey item was present. The results showed that the subjects did modify their search rate and this improved their ability to detect the prey. However, apostatic selection occurred when the prey were presented in unequal frequencies and this suggests that search images were formed.</p
Autoantibodies and the cytoskeleton
No full textThis study describes measurement of antibodies to the cytoskeleton in man using a variety of fluorescent techniques and subsequently a radioimmunoassay. Initially indirect immunofluorescence using a rat tissue substrate was employed. This technique, though widely clinically used was found to lack both specificity and sensitivity. The subjective reporting of samples is an additional disadvantage. A study in patients with malignant disease showed no increased incidence of autoantibodies. Subsequent studies employed a fixed tissue culture cell substrate. This technique increased sensitivity but specificity remained poor. A radioimmunoassay was developed for the measurement of antibody to tubulin, a microtubule component protein. Using this highly specific technique it was possible to detect antitubulin antibody in all members of a healthy control population. Elevated antibody levels were detected in a number of diseases, but particularly in infectious mono-nucleosis. An affinity chromatography purified antitubulin antibody was produced from this source.Rabbit immunization with actin and tubulin failed to resultin detectable increases in antibody levels to these antigens. Of particular note was the finding of cytoskeletal antibodies in most animals pre-immunization. The reported incidence of autoantibodies is related predominantly to the sensitivity of the technique involved in their evaluation. Radioimmunoassay would appear to be a suitable tool for such studies in the future.</p
Molecular dynamics or: How I learned to stop worrying and love the membrane
No full textThe rise of antibiotic resistant bacterial species is an international problem. The structure, function and dynamic behaviour of the bacterial cell envelope must be thoroughly understood in order to design novel antimicrobial molecules. This thesis presents the use of molecular dynamics techniques to investigate the function of the Gram-negative outer membrane enzyme LpxR, as well as the subsequent effect of the protein on the dynamics of the outer membrane. LpxR covalently modifies a constituent of the outer membrane, lipopolysaccharide, which can modulate the immune response of the host. Simulations enabled the identification of a putative closed conformation for the protein, as well as a secondary ion binding site. These observations led to the proposition of an evaluated catalytic mechanism for the membrane enzyme.The effect of lipopolysaccharide deacylation on wider membrane properties and dynamics was also investigated. Deacylated lipopolysaccharide induced positive curvature on the membrane when in distinct patches; cardiolipin phospholipids also clustered in areas of the inner leaflet corresponding with the patches of deacylated lipopolysaccharide in the outer leaflet. The application of an electric field to these modified membranes identified structural weaknesses at the interface between deacylated and wildtype lipopolysaccharide. Electroporation of the outer membrane model with OmpA embedded was also performed, and these simulations indicated that the presence of integral proteins may cause localised weakness in the membrane. Finally, the interactions between polymyxin B1, an antimicrobial peptide, and the outer membrane were examined, to gain a further understanding of how the molecule infiltrates the Gram-negative cell envelope. The peptides were observed to permeate through both the outer and inner membrane models, resulting in phospholipid flipflopping, thereby degrading the lipid asymmetry of the outer membrane. Data presented here provide the basis for an updated self-promoted uptake mechanism of cellular infiltration for polymyxin B1
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
High temperature superconducting power cable termination
No full textSIGLEAvailable from British Library Document Supply Centre-DSC:DXN031128 / BLDSC - British Library Document Supply CentreGBUnited Kingdo
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
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