1,721,124 research outputs found
The kinetics and mechanisms of destabilisation and aggregation of microcolloidal iron and associated phosphate during simulated estuarine mixing
No full textThe removal of iron from the <0.45µm fraction of Tamar River water on addition of both calcium chloride solution and sea water was studied using a continuous autoanalytical system. The addition of increasing concentrations of either calcium ions or sea water caused increased iron removal, but at all of the concentrations studied a fraction of iron was found to remain within the <0.45µm fraction (termed the residualor unreactive fraction). Storage time was shown to have a marked effect on the residual concentration. Kinetic analysis of the experimental results showed that when a residual fraction was taken into account, the data could be described by either a first or second order kinetic model. The first order model gave an approximately linear increase in rate constant with increasing concentrations of calcium ions or sea water, ranging from 1.02 x 10-3 to 6.14 x 10-3 s-1 for the addition of calcium ions and from 3.97 x 10-3 to 6.95 x 10-3 s-1 for the addition of seawater. The second order rate constant also showed an increase with increasing calcium concentration, from 3.95 x 10-5 to 3.02 x 10-4 l mol-1 s-1 . When the first and second order profiles were studied and the fit of the model to the experimental residual values was considered, the first order was shown to be a better descriptor ofthe observed removal of microcolloidal iron. A comparative study was made of iron removal under different conditions of simulated estuarine mixing, following the procedures of Fox & Wofsy (Geochim. Cosmochim. Acta, 1983, vol 47 p211), Mayer (Geochim. Cosmochim. Acta, 1982, vol 46 p2527), Hunter & Leonard (Geochim. Cosmochim. Acta, 1988, vol 52 pi 123) - all using 'discrete sampling during mixing and Duffy (PhD Thesis, University of Southampton) - using continuous sampling with more rapid mixing. Variations among the 'discrete' methods are small relative to those between them and the method of Duffy (1985) e.g. 65 % for the 'continuous' method as compared with 36%, at a salinity of 5, and the first order rate constant was seen to be about an order of magnitude greater for the 'continuous' method e.g. 3.97 x 10-3 s-1 as compared with 1.97 x 10-4 s-1, at a salinity of 5. Further experiments looking specifically at the effect of stirring rate on a 'discrete' sampling method concurred with these observations. In experiments carried out at a salinity of 8, the iron removal increased from 44% to 55% and the first order rate constant increased from 2.96 x 10-3 to 3.58 x 10-3 s-1 as a result of a relative increase in stirring rate from 1 to 5. The fact that the first order rate constant for iron removal varied with the energy of the system, even in the least energetic system studied, and that under all conditions the first order model provided the best descriptor of the observed process, showed that the mechanism of microcolloidal aggregation under all these conditions could not be accounted for by Brownian Motion. Shear must therefore be a significant factor and it was concluded that none of the systems studied could afford a test of kinetic order under conditions where Brownian Motion dominantly accounts for particle collisions. The experiments, however, are still of relevance to environmental conditions, since estuarine mixing is greatly influenced by turbulence due to tidal energy and wind stress. Phosphate behaviour was studied concurrently with that of iron and both the percentage removal and kinetic rate constants showed comparable dependence on calcium ion / sea water concentration, although the percentage phosphate removal was consistently lower than that observed for iron. Kinetic rate constants ranged from 0.0019 to 0.0179 s-1 for the first order model and 0.29 x 10-4 to 5.3 x 10-4 1 mol-1 s-1 for second order. When the removal profiles were studied and the fit of the first and second order models to the experimental residual values was considered, the first order model was again shown to be a better descriptor of the observed removal. Phosphate behaviour remained essentially unaffected by changes in experimental methodologies or stirring rate. The factor which most affected iron (stirring) had no major systematic effect on phosphate and therefore it must be concluded that the results indicate a co-removal of phosphate during iron colloid aggregation rather than removal of a common colloidal population containing both constituents
An investigation into the use of pyridine-cored molecular pincers for asymmetric resolution and catalysis
No full textEThOS - Electronic Theses Online ServiceGBUnited Kingdo
The synthesis of novel phospholipids
No full textSIGLEAvailable from British Library Document Supply Centre- DSC:DX186462 / BLDSC - British Library Document Supply CentreGBUnited Kingdo
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
Approaches and frameworks for management and research in small-scale fisheries
No full text[Extract] There is general agreement that commonly
adopted approaches to managing small-scale fisheries (SSFs) in developing countries have been less effective than they need to be to ensure sustainability (Garcia and Grainger,
1997; Mahon, 1997; Cochrane, 2000; Welcomme, 2001; FAO, 2003; Béné et al., 2004; Cochrane and Doulman, 2005). Given the importance of SSFs in the social and economic
fabric of many least developed countries, it is essential that new management approaches are developed and adopted. This is complicated because SSFs present particular challenges to managers in terms of their diversity
and complexity (Berkes et al., 2001; Berkes, 2003; Jentoft, 2006, 2007)
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
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