1,721,029 research outputs found
Three-dimensional imaging of xylem at cell wall level through near field nano holotomography
No full textAbstract Detailed imaging of the three-dimensionally complex architecture of xylary plants is important for studying biological and mechanical functions of woody plants. Apart from common two-dimensional microscopy, X-ray micro-computed tomography has been established as a three-dimensional (3D) imaging method for studying the hydraulic function of wooden plants. However, this X-ray imaging method can barely reach the resolution needed to see the minute structures (e.g. pit membrane). To complement the xylem structure with 3D views at the nanoscale level, X-ray near-field nano-holotomography (NFH) was applied to analyze the wood species Pinus sylvestris and Fagus sylvatica . The demanded small specimens required focused ion beam (FIB) application. The FIB milling, however, influenced the image quality through gallium implantation on the cell-wall surfaces. The measurements indicated that NFH is appropriate for imaging wood at nanometric resolution. With a 26 nm voxel pitch, the structure of the cell-wall surface in Pinus sylvestris could be visualized in genuine detail. In wood of Fagus sylvatica , the structure of a pit pair, including the pit membrane, between two neighboring fibrous cells could be traced tomographically
Structural analysis of silk proteins using x–ray and neutron scattering
Full text linkThe silk fibres spun by insects and spiders have intrigued scientists for many years. Their mechanical performance is remarkable when one considers that the fibres are spun under ambient conditions from aqueous protein solutions without requiring many of the harsh processing conditions used in the production of man-made fibres. Yet, despite this interest, very little is known about the initial structure of the precursor proteins prior to spinning. One reason for this lies in the difficulty of handling the native proteins without accidental aggregation. Therefore in this thesis a novel sample preparation protocol for native silk is developed and small angle scattering (SAS) techniques are combined with circular dichroism (CD) and atomic force microscopy (AFM) to examine the structure and morphology of the proteins with different mechanical properties and thus biological function in nature. This work highlights the importance of studying native, functional proteins, at close to in vivo conditions, since clear differences in the structure and interaction of native and reconstituted silks can be attributed to the additional processing which reconstituted silks have undergone in order to be solubilised. Indeed native silk proteins are found to be more inherently non-interacting at quite high protein concentrations than reconstituted silk. Upon dilution, inter-chain interactions can be observed by SAS and CD as the protein is driven from its equilibrium conformation. This interaction and the shear-induced assembly of these proteins are also followed by AFM. Interestingly, native silk proteins from spider and silkworms retain a semiflexible conformation in solution. Indeed by comparing the silks from the major and minor ampullate, flagelliform and cylindriform glands of Nephila edulis with the cocoon silk of Bombyx mori silkworms, important insights are gained into how their flexibility suggests similarities in the local environment of the protein chains thereby dictating the hierarchical structure of silk fibres
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
Structural analysis of silk proteins using x–ray and neutron scattering
No full textThe silk fibres spun by insects and spiders have intrigued scientists for many years. Their mechanical performance is remarkable when one considers that the fibres are spun under ambient conditions from aqueous protein solutions without requiring many of the harsh processing conditions used in the production of man-made fibres. Yet, despite this interest, very little is known about the initial structure of the precursor proteins prior to spinning. One reason for this lies in the difficulty of handling the native proteins without accidental aggregation. Therefore in this thesis a novel sample preparation protocol for native silk is developed and small angle scattering (SAS) techniques are combined with circular dichroism (CD) and atomic force microscopy (AFM) to examine the structure and morphology of the proteins with different mechanical properties and thus biological function in nature. This work highlights the importance of studying native, functional proteins, at close to in vivo conditions, since clear differences in the structure and interaction of native and reconstituted silks can be attributed to the additional processing which reconstituted silks have undergone in order to be solubilised. Indeed native silk proteins are found to be more inherently non-interacting at quite high protein concentrations than reconstituted silk. Upon dilution, inter-chain interactions can be observed by SAS and CD as the protein is driven from its equilibrium conformation. This interaction and the shear-induced assembly of these proteins are also followed by AFM. Interestingly, native silk proteins from spider and silkworms retain a semiflexible conformation in solution. Indeed by comparing the silks from the major and minor ampullate, flagelliform and cylindriform glands of Nephila edulis with the cocoon silk of Bombyx mori silkworms, important insights are gained into how their flexibility suggests similarities in the local environment of the protein chains thereby dictating the hierarchical structure of silk fibres.EThOS - Electronic Theses Online ServiceGBUnited Kingdo
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
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