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Virus Removal in Ceramic Depth Filters Based on Diatomaceous Earth
No full textCeramic filter candles, based on the natural material diatomaceous earth, are widely used to purify water at the point-of-use. Although such depth filters are known to improve drinking water quality by removing human pathogenic protozoa and bacteria, their removal regarding viruses has rarely been investigated. These filters have relatively large pore diameters compared to the physical dimension of viruses. However, viruses may be retained by adsorption mechanisms due to intermolecular and surface forces. Here, we use three types of bacteriophages to investigate their removal during filtration and batch experiments conducted at different pH values and ionic strengths. Theoretical models based on DLVO-theory are applied in order to verify experimental results and assess surface forces involved in the adsorptive process. This was done by calculation of interaction energies between the filter surface and the viruses. For two small spherically shaped viruses (MS2 and PhiX174), these filters showed no significant removal. In the case of phage PhiX174, where attractive interactions were expected, due to electrostatic attraction of oppositely charged surfaces, only little adsorption was reported in the presence of divalent ions. Thus, we postulate the existence of an additional repulsive force between PhiX174 and the filter surface. It is hypothesized that such an additional energy barrier originates from either the phage's specific knobs that protrude from the viral capsid, enabling steric interactions, or hydration forces between the two hydrophilic interfaces of virus and filter. However, a larger-sized, tailed bacteriophage of the family Siphoviridae was removed by log 2 to 3, which is explained by postulating hydrophobic interactions
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
Virus removal in ceramic depth filters: the electrostatic enhanced adsorption approach
Get PDFDiese Arbeit untersucht den Einsatz von keramischen Materialien in der Trinkwasseraufbereitung mittels Filtration und fokussiert dabei die Entfernung von Viren. Herkömmliche, auf Kieselgur basierende Tiefenfilter (Filterkerzen) mit Porengrößen im unteren Mikrometerbereich, werden hinsichtlich ihres Rückhaltevermögens gegenüber Kolloiden (Viren sowie Polystyrolpartikel) untersucht, um deren Einsatzfähigkeit in der Entfernung von Mikroorganismen im Allgemeinen abschätzen zu können. Ferner wird gezeigt, wie durch ein einfaches Verfahren solche Filter modifiziert werden können, um auch kleinste Viren mit ca. 30 nm Durchmessern aus dem Rohwasser zu entfernen. Die Zugabe von MgO während der Granulierungsstufe im Herstellungsprozess der Filterkerzen bewirkt eine erhebliche Verbesserung des Virenrückhalts bis zu über 99.9999%. Die experimentellen Ergebnisse wurden dabei mit theoretischen Modellen verglichen, um Aussagen über die Mechanismen der Virenentfernung treffen zu können.:Contents
Chapter I Introduction 1
Chapter II Removal or inactivation of microorganisms, in particular viruses, for drinking water purposes with focus on small-scale, decentralised systems: A literature review 7
II. I Physical and chemical treatments 8
II. II Filtration processes 10
II. III Conclusions 15
Chapter III Mechanisms of adsorption in depth filtration 17
III.I Surface charge and the electrical double layer 18
III.II van der Waals interactions 22
III.III DLVO theory 23
III.IV Non-DLVO forces 25
III.V Extended DLVO Theory 27
Chapter IV Virus adsorption studies 29
IV.I A literature review 30
IV.I.I Virus concentration by adsorption-elution 33
IV.I.II Improved virus adsorption in filtration 35
IV.II The electrostatic enhanced adsorption approach 37
Chapter V Viruses 39
V.I Literature review 40
V.I.I Structure and morphology 40
V.I.II The viral life cycle 41
V.I.III Human pathogenic viruses in the aquatic environment 42
V.II Experimental 46
V.II.I The choice of viruses for adsorption studies 46
V.II.II Propagation and enumeration of the bacteriophages 48
V.II.III Characterisation of bacteriophages 51
V.III Results and discussion 54
V.III.I Production of high-titre and high-purity phage stocks 54
V.III.II Characteristics of bacteriophages 59
V.III.III Detection of a viral contaminant - the ‘Siphophage’ 64
Chapter VI The diatomaceous earth-based depth filter 69
VI.I Literature review 70
VI.I.I Diatomaceous earth 70
VI.I.II Retention of microorganisms in the DE-based depth filter 71
VI.II Experimental 73
VI.II.I Manufacturing the depth filter 73
VI.II.II Physical characterisation 74
VI.II.III Performing filter retention tests 75
VI.II.IV Latex retention test 76
VI.II.V Studying adsorption kinetics in a batch experiment 79
VI.II.VI Applying (X-)DLVO theory 80
VI.III Results and discussion 83
VI.III.I Characterisation of the depth filter 83
VI.III.II Latex removal in the depth filter 86
VI.III.III Filter performance on virus removal 94
VI.III.IV Batch-sorption experiments 99
VI.IV Summary and conclusions 102
Chapter VII The magnesium oxide modified depth filter 103
VII.I Experimental 104
VII.I.I Choice of the adsorbent material 104
VII.I.II Manufacturing the MgO-modified filter and characterisation methods 105
VII.II Results and discussion 106
VII.II.I The adsorbent: Magnesium oxide powder 106
VII.II.II Physical characterisation of modified depth filters 108
VII.II.III Virus removal in depth filters containing MgO 113
VII.II.IV Ageing behaviour of MgO modified filters 118
VII.II.V Discussion on the removal mechanisms 130
VII.III Summary and conclusions 134
Chapter VIII Summary, conclusions and outlook 135
VIII.I Summary and conclusions 136
VIII.II Outlook 137
Abbreviations, symbols and physical constants 139
Reference list 14
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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