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Natural products for antifouling coatings
No full textBiofouling of marine structures and platforms results in both economical and environmental penalties. Current approaches to marine antifouling increasingly adopt strategies to minimise their environmental impact. One approach is to successfully mimic nature’s methods to control biological growth. A key biomimetic development for marine antifouling coatings is the isolation and use of marine natural products. Such chemicals are needed for secondary metabolic requirements of plants and animals, including defence chemicals. Recent work has focused on isolation and bioassaying techniques but few studies have trialed natural product compounds in a functional coating system. A recent project in our laboratories has used a multidisciplinary approach to develop an antifouling coating system using environmentally acceptable and naturally occurring products. A red algal natural product extract from Chondrus crispus has been evaluated as a potential antifoulant. The ethanol extract was successfully screened with a bioassay which included a range of biofouling organisms; marine bacteria, microalgae and macroalgae. The natural product extract was directly incorporated into a proprietary coating mixture to assess its activity through a realistic delivery mechanism and to test if its addition affected the coating matrix. The latter was tested in 3.5 % NaCl solutions using electrochemical impedance spectroscopy (EIS) and open-circuit potential (OCP) electrochemical techniques. The incorporation of the algal extract into the coating resulted in a slightly more negative corrosion potential of the coated mild steel by 30 mV (Ag/AgCl reference), and did not affect the impedance characteristics when compared to the control coating with no antifoulant. This suggests that the direct use of the natural product extract in the coating is an effective way to test antifouling activity for future compounds. The antifouling activity of the experimental coating was tested in seawater. Biofilm growth on the coating surfaces was examined using a bacterial viability nucleic acid stain and an episcopic differential interference contrast (EDIC) microscope. This proved to be a rapid tool for the examination of growth patterns and distribution of bacteria in-situ. Field trials were used in the Solent, England and showed a visual antifouling delay of 6 weeks in comparison to the negative control. The development of a functional antifouling coating should be possible using an aqueous phase solution such as a marine natural product
Biomimetic inspired marine antifouling coating system assessed using electrochemical techniques
No full textPractical aspects of developing a natural product based marine antifouling coating system
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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
How to handle constraints with evolutionary algorithms
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84516.pdf (author's version ) (Closed access
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
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