1,721,168 research outputs found
Colonization strategies of lithobiontic microorganisms on carbonate rocks
No full textBiogenic weathering is caused by the action of lithobiontic organisms. Homogeneous carbonates are predominantly colonized by endolithic species that actively penetrate the rock substratum independent of already existing pores or fissures. The organisms construct a system of ducts and cavities by active dissolution of the substratum. A fresh, noncolonized surface is penetrated by algae and ascomycetes in the first and second year after exposure to the environment. The establishment of complex colonization patterns on and in the substratum by lichens takes several years. In spite of the primary deteriorative effect on their substratum by the organisms, long-term endolithic growth also involves mechanisms that stabilize and preserve the rock surface morphology. A tightly woven cellular network may strengthen the colonized stone. This feature is of importance when natural and building stone are affected by biogenic weathering phenomena
Biofilms and extracellular matrices on geomaterials
No full textMicrobial biofilms are ubiquitous in aquatic and terrestric ecosystems as well as on man-made material. They are initial colonizers on all surfaces and take part in biogenic weathering on natural rocks as well as on building stone. The structure and function of the biofilm matrix, mainly extracellular polysaccharides (EP), is documented for biofilms on stone surfaces: the hydrated gel acts as glue between the organisms and the material surface. Besides EP, living cells, cell debris and mineral particles are embedded in the matrix. These particles appear to be deposited on the surfaces of cell walls and interfaces in the biofilm matrix. As an important function of the matrix, EP stabilizes the biological activity against periodic desiccation. It was demonstrated that in several polymers (alginate, dextran, levan and others) a typical extracellular enzyme, the alpha-amylase, develops enhanced resistance against desiccation stress. Consequences of EP production and biofilm development on surfaces are discussed
Biofilms and their extracellular environment on geomaterials: methods for investigation down to nanometre scale
No full textOn solid surfaces of building material, micro-organisms form a tightly attached layer that may affect the underlying substratum. The biofilm is mainly composed of cells and extracellular polymeric substances (EPS; mostly various polysaccharides). Attachment of the mature biofilm on the substratum is mediated by the EPS. For analysis by transmission electron microscopy, the biofilm structure must be maintained by appropriate methods that stabilize the organisms and especially the EPS. Specially adapted preparation techniques allow detachment of a surface biofilm or dissolution of the substratum without affecting the biofilm structure. The cellular and extracellular structures are retained in such a way that they are detectable by various specific marker systems
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
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