1,720,958 research outputs found
Dataset to support the Southampton doctoral thesis "Developing artificial biofilms for investigating the effects of physico-mechanical properties on marine biofilm-associated drag'
No full text Data supporting chapter 7 of the thesis 'The effect of surface colour on marine biofilm physico-mechanical properties' and data supporting Chpater 8 of the thesis 'studying the effect of hydrodynamics on marine biofilm associated physicomechanics and drag'</span
Developing artificial biofilms for investigating the effects of physico-mechanical properties on marine biofilm-associated drag
No full textMarine biofilms cause a significant increase in drag on ships. From the current literature it is understood that physical and mechanical (physico-mechanical) properties of biofilms influence drag, yet it remains understudied. In part, this is explicable by biofilm heterogeneity and adaptability which complicate efforts to link biofilm properties to frictional drag. As a result, rigid and homogeneous structures are typically used as the benchmark for studying biofilm-associated drag, but as they neglect natural biofilm behaviour, such as viscoelasticity, they could be causing underestimations in drag predictions. To improve drag predictions there is a need to better understand biofilm fluid-structure interactions and the role these play in drag production. In the current work, it was shown that mesoscopic structural properties: thickness, coverage, and roughness, of marine biofilms interact with viscoelasticity and therefore implicate drag. This relationship was reported using a meso-scale flow cell with an integrated pressure drop system in conjunction with Optical Coherence Tomography (OCT) which enabled deformation behaviour to be captured in-situ in real-time whilst simultaneously measuring drag (expressed as a friction coefficient). To build on rigid conventional models, a material sandpaper system with a tailored mechanical profile and surface roughness was proposed. The results showed that, over a Reynolds number range of 1.2 × 104 to 5.2 × 104, an elastomeric sandpaper system caused up to a 52 % higher drag and produced a different drag curve when compared to rigid alternatives of equivalent roughness; differences were attributed to differences in the mechanical response to increasing shear. Similar drag curves were also found for marine biofilms grown at Hartlepool Marina (UK) under hydrodynamic conditions and using OCT it was revealed that viscoelastic behaviour (such as deformation and streamer behaviour) was, in part, responsible for the deviation from rigid drag trends. From the experimental model, and from marine biofilm testing, it was concluded that viscoelasticity plays a critical role in drag production, displays a relationship with structural properties and should not be neglected when estimating biofilm-associated drag by using rigid rough models. Marine biofilms grow on different surfaces, for example on different coatings, or under varying hydrodynamic conditions which likely alter biofilm physico-mechanics and implicate drag.Despite this, marine biofilm viscoelasticity has not been previously quantified in the literature. Here, marine biofilms were cultivated across different surfaces in-field and were rheologically characterised using a parallel-plate rheometer. An OCT was utilised to capture biofilm structure and to further investigate links between biofilm structure and mechanics under different conditions. This Thesis confirmed that marine biofilms are viscoelastic, with a shear modulus ranging from 11 Pa to 7500 Pa depending on growth conditions. For example, biofilms grown under a low flow velocity were softer, thinner, experienced greater structural disruption and produced a 5.7 % higher drag (over a Reynolds number range of 1.2 × 104 to 5.2 × 104) than biofilms grown under a higher flow. In this work it has been emphasised how marine biofilms exhibit dynamic physico-mechanical behaviour when exposed to shear and how elastomeric materials could be better suited for mimicking biofilm-associated drag. The results presented offer insight into the complex and dynamic interactions between biofilm properties and how different surface or growth conditions can alter these relationships. In the long term, this data could be used to improve estimations of biofilm-associated drag and support the development of future marine coatings for targeting drag-producing properties, such as viscoelasticity
Dataset to support the journal article: "Surface properties influence marine biofilm rheology, with implications for ship drag"
No full textThe data is to support the journal article: Surface properties influence marine biofilm rheology, with implications for ship drag, published in the Soft Matter Journal. Data included are all excel spreadsheets; some present the raw data with mean +/- SD calculated and others show data that have been inputted into equations to give required results. Some figures used in the manuscripts are also included in the spreadsheets.</span
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
Dataset for to support the journal article 'Elastomeric sandpaper replicas as model systems for investigating elasticity, roughness and associated drag in a marine biofilm flow cell'
No full textDataset to support publication to Ocean Engineering: Elastomeric sandpaper replicas as model systems for investigating elasticity, roughness and associated drag in a marine biofilm flow cell.
This work was funded by a DTP ESPRC grant EP/R513325/1 to the University of Southampton with partial funding from NBIC/BBSRC 01POC18032 and AkzoNobel. </span
Surface properties influence marine biofilm rheology, with implications for ship drag
No full textMarine biofilms on ship hulls increase frictional drag, which has economic and environmental consequences. It is hypothesised that biofilm mechanics, such as viscoelasticity, play a critical role in biofilm-associated drag, yet is a poorly studied area. The current study aimed to rheologically characterise ship-relevant marine biofilms. To combat marine biofilms on ship hulls, fouling-control coatings are often applied; therefore, the effect of different surfaces on marine biofilm mechanics was also investigated. Three surfaces were tested: a non-biocidal, chemically inert foul-release coating (FRC), an inert primer (ACP) and inert PVC. Physical properties of biofilms were explored using Optical Coherence Tomography (OCT) and a parallel-plate rheometer was used for rheological testing. Image analysis revealed differences in the thickness, roughness, and percent coverage between the different biofilms. Rheological testing showed that marine biofilms, grown on FRC and ACP acted as viscoelastic materials, although there were differences. FRC biofilms had a lower shear modulus, a higher viscosity, and a higher yield stress than the ACP biofilms, suggesting that the FRC biofilms were more readily deformable but potentially more robust. The results confirmed that surface treatment influences the structural and mechanical properties of ship-relevant marine biofilms, which could have implications for drag. A better understanding of how different surface treatments affect marine biofilm rheology is required to improve our knowledge on biofilm fluid-structure interactions and to better inform the coating industry of strategies to control biofilm formation and reduce drag
Elastomeric sandpaper replicas as model systems for investigating elasticity, roughness and associated drag in a marine biofilm flow cell
No full textBiofilm heterogeneity and adaptability complicates efforts to link biofilm structural and mechanical properties to frictional drag. As a result, rigid structures are typically used as the benchmark for studying biofilm-associated drag. Elastomeric sandpaper replicas were generated to be used as model systems for investigating the effect of roughness and elasticity on drag, over the Reynolds number range of approximately 2.0 × 104 to 5.2 × 104 Re using a marine biofilm flow cell. To control for roughness parameters and surface topography the replicas were created for sandpaper grit numbers: P40, P80 and P240 with average measured roughness (Sa) of 108, 49 and 16 μm, respectively. Profilometry confirmed that there was no significant difference between the roughness of the rigid sandpaper sources and the material replicas. The marine biofilm flow cell was fitted with a clear lid, which allowed real-time visualisation of the replicas’ surface topography using Optical Coherence Tomography. Pressure drop measurements, expressed as a friction coefficient, revealed that the elastomeric sandpaper replicas had a significantly higher associated drag, of up to 52%, when compared to the rigid counterparts. From statistical analysis it was confirmed that material mechanical properties, such as elasticity, and surface roughness both significantly affect drag. Elastic model systems can be used to enhance our understanding of biofilm physico-mechanics and their role in marine drag.</p
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