1,720,965 research outputs found
Mineralogy of marine sediment systems:A geochemical framework
No full textSediments are a major component of the ocean system and the composition of, and chemical processes acting upon, these sediments are controlled by many factors. In this chapter we outline the major types of marine sediment (lithogenous, biogenic, hydrogeneous and authigenic), discuss the sources of these and their chemical and mineral characteristics. The most abundant minerals are (oxyhydr)oxides, clay minerals, sulfides and carbonates, and all of these have been studied extensively, using a range of mineralogical techniques. A major aim of this chapter is to provide a framework by which the mineral transformations that take place upon, or just below, the sea-floor can be understood. There are significant thermodynamic, kinetic and biological controls on these transformations, and the interaction of these plays a major role in element cycling between the oceans and the lithosphere, and trace element-enrichment on the sea-floor and carbon burial and remineralization. Further, we conclude that more research is required on the interactions between minerals and bacteria within marine sediments, and on the role of amorphous oxide minerals delivered from land in early burial reactions and mineral precipitations.Oceans cover ∼70% of the Earthâ∈™s surface so that the processes operating within the marine realm and upon ocean floors play a marked role in element and nutrient cycling, biological productivity, ultimately exerting an important influence on global climate. This chapter will focus on the distribution, composition and mineralogy of sediments that are actively accumulating on the sea floor, both in the shallow marine and deep ocean realms. Further, it will describe the geochemical and mineralogical processes operating in these sediments
The nature and scope of environmental mineralogy
No full textMinerals, as the inorganic solids that comprise the rocks, sediments and soils of the Earth, are an essential part of our environment. So, in a sense, all mineralogy is ‘environmental mineralogy’. However, the term ‘environmental’ has come to be employed (particularly in combination with terms such as ‘science’, ‘issue’ or ‘problem’) to refer to those systems at or near the surface of the Earth where the geosphere comes into contact with the hydrosphere, atmosphere and biosphere. This is, of course, the ‘environment’ upon which the human race depends for survival and, hence, is now sometimes referred to as the ‘critical zone’. It can be subject to disruptions due to human activity, particularly activity associated with the exploitation and utilization of Earth’s resources. This is the sense in which we use the term ‘environmental’ in this book. Thus, we consider here those systems containing minerals that constitute the most important or key environments: soils, modern sediments, atmospheric aerosols, and the interior or exterior parts of certain micro- and macro-organisms. Particularly important are the roles that minerals play in processes that act over time to control or influence the environment at various scales of observation. Both pure systems and those contaminated as a result of human activity are considered. We also focus on certain specific problems that arise from resource exploitation or utilization and that involve minerals in some way; either, or both, in creating the problem or ameliorating it. These include problems associated with the waste generated by mining, particularly mining of metals, industrial and domestic wastes, and those wastes produced by the nuclear industry. Particular problems can arise from use of minerals and rocks in buildings and monuments and other cultural artefacts. The relationship between minerals and human health constitutes a special case where the environment includes the human body itself
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
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