1,720,970 research outputs found
The development of a marine antifouling system using environmentally acceptable and naturally occurring products
No full textDue to legislative pressures and the recent ban of trybutyl tin, alternative environmentally acceptable ship hull antifouling systems are required. This thesis uses a multidisciplinary approach to combine two disparate areas of research namely marine biology and surface engineering, to develop a novel natural product (NP) based antifouling system. The overall objective of this thesis is to transfer a natural marine biological defence mechanism into an engineered antifouling coating system. By combining natural product extraction and incorporation into a trial coating an extensive test programme was able to investigate the antifouling performance and address the issues of bringing this active area of research to the next technological readiness level. By using a stepwise approach to the development of the engineered solution, a suite of techniques were used to fully characterise a NP based system. The biological and surface engineering techniques adapted and developed are described here and their future use to evaluate a novel NP based antifoulant system is critically assessed.After an extensive literature review, an ethanol extract from the red seaweed Chondrus crispus was selected as the natural product source. NP specimens were harvested locally and also purchased as industrially processed dried algae. The industrially processed algae showed good antifoulant activity ( ≤ 25 µg/mL) in laboratory bioassays and had a greater efficacy than the locally harvested samples highlighting its potential as an economically viable solution. The direct incorporation of the NP into a commercial control depletion polymer binder, allowed for the rapid development of characterisation techniques to evaluate the effects this had on the performance of the NP-binder matrix. The feasibility of a range of electrochemical techniques to measure corrosion potential, impedance, resistance and water uptake in the NP coating was critically assessed. A combination of open-circuit potential and electrochemical impedance spectroscopy provided a unique and rapid means to non-destructively measure the contribution of incorporated NPs to the degradation and water uptake of the binder film. Studies of biofilm growth were used to successfully measure community viability and structure using fluorescent staining and differential interference contrast microscopy. These techniques were found to be very informative on Southampton water marine biofilm community structure and were cross correlated by Fourier transform infrared measurements. Resistance to biofouling was determined through field trials, an important testing platform for an antifouling system, and specifically trials which test the entire coated system including any primers and substrate preparation requirements. An initial NP antifouling performance greater than the booster biocide (Chlorothalonil) control was documented for one field trial over a period of the first 6 weeks.A key aspect was to determine the potential efficacy of NPs and their viability in a coating system. To achieve this, a range of standard and non-standard techniques were used to assess this novel combination of crude NP extract and commercial binder system. This work has shown that a limited antifoulant activity is achievable. By evaluating the effect of a NP on both the fouling community and a binder system this unique approach helps define key techniques to assess future NP antifoulants and identifies the optimisation required to increase their functionality
Comparing the short and long term stability of biodegradable, ceramic and cation exchange membranes in microbial fuel cells
No full textThe long and short-term stability of two porous dependent ion exchange materials; starch-based compostable bags (BioBag) and ceramic, were compared to commercially available cation exchange membrane (CEM) in microbial fuel cells. Using bi-directional polarisation methods, CEM exhibited power overshoot during the forward sweep followed by significant power decline over the reverse sweep (38%). The porous membranes displayed no power overshoot with comparably smaller drops in power during the reverse sweep (ceramic 8%, BioBag 5.5%). The total internal resistance at maximum power increased by 64% for CEM compared to 4% (ceramic) and 6% (BioBag). Under fixed external resistive loads, CEM exhibited steeper pH reductions than the porous membranes. Despite its limited lifetime, the BioBag proved an efficient material for a stable microbial environment until failing after 8 months, due to natural degradation. These findings highlight porous separators as ideal candidates for advancing MFC technology in terms of cost and operation stability
The Power of Glove: Soft Microbial Fuel Cell for Low-Power Electronics
Full text linkA novel, soft microbial fuel cell (MFC) has been constructed using the finger-piece of a standard laboratory natural rubber latex glove. The natural rubber serves as structural and proton exchange material whilst untreated carbon veil is used for the anode. A soft, conductive, synthetic latex cathode is developed that coats the outside of the glove. This inexpensive, lightweight reactor can without any external power supply, start up and energise a power management system (PMS), which steps-up the MFC output (0.06–0.17 V) to practical levels for operating electronic devices (>3 V). The MFC is able to operate for up to 4 days on just 2 mL of feedstock (synthetic tryptone yeast extract) without any cathode hydration. The MFC responds immediately to changes in fuel-type when the introduction of urine accelerates the cycling times (35 vs. 50 min for charge/discharge) of the MFC and PMS. Following starvation periods of up to 60 h at 0 mV the MFC is able to cold start the PMS simply with the addition of 2 mL fresh feedstock. These findings demonstrate that cheap MFCs can be developed as sole power sources and in conjunction with advancements in ultra-low power electronics, can practically operate small electrical devices
Fade to Green: A Biodegradable Stack of Microbial Fuel Cells
Full text linkThe focus of this study is the development of biodegradable microbial fuel cells (MFCs) able to produce useful power. Reactors with an 8 mL chamber volume were designed using all biodegradable products: polylactic acid for the frames, natural rubber as the cation-exchange membrane and egg-based, open-to-air cathodes coated with a lanolin gas diffusion layer. Forty MFCs were operated in various configurations. When fed with urine, the biodegradable stack was able to power appliances and was still operational after six months. One useful application for this truly sustainable MFC technology includes onboard power supplies for biodegradable robotic systems. After operation in remote ecological locations, these could degrade harmlessly into the surroundings to leave no trace when the mission is complete
Urine-activated origami microbial fuel cells to signal proof of life
Full text linkThe adaptability and practicality of microbial fuel cells (MFCs) are highly desirable traits in the search for alternative sources of energy. An innovative application for the technology could be to power portable emergency locator transmitters (ELTs). Such devices would ideally need to be lightweight, robust and fast-in terms of response. Urine is an abundant resource, and with MFCs, could be the ideal fuel for powering ELTs, with the compelling advantage of also indicating proof of life. We developed novel origami tetrahedron MFCs (TP-MPFCs) using photocopier paper to test different urine-based inoculants. When inoculated with urine extracted from the anode chambers of working MFCs a stack of 6 abiotic MFCs produced a usable working voltage after just 3 h 15 min; enough to energise a power management system. The anodes of established TP-MFCs were then removed and air-dried for 7 days before being inserted into new paper reactors and refrigerated. After 4 weeks, these MFCs displayed an immediate response to fresh urine and achieved a functional working voltage in just 35 minutes. Two paper MFCs connected in parallel were able to transmit 85 radio signals and in a series configuration 238 broadcasts over 24 hours. These findings demonstrate that simple, inexpensive, lightweight paper MFCs can be employed as urine-activated, “proof of life” reporting systems.<br/
Towards disposable microbial fuel cells: Natural rubber glove membranes
No full text© 2014 Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved. Natural rubber from laboratory gloves (GNR) was compared to cation exchange membrane (CEM) in microbial fuel cells (MFCs). GNR-MFCs immediately generated power indicating the availability of proton transfer pathways in the material, which is contrary to previous research using condom natural rubber membranes. Under bi-directional resistance sweeps, CEM-MFCs produced higher power but were less stable than GNR. Stability proved the valuable trait over 96 h periods under fixed resistances where GNR-MFCs produced 26% higher power than CEM-MFCs and reduced COD by 88% compared to 73% achieved with CEM. Anolyte conductivity increased more significantly for CEM but at the same time pH levels were more marked, a factor that may have contributed to instability. Under composting conditions, GNR samples degraded 100% after 285 days whilst GNR-MFC membranes were still intact and operational after 493 days. This innovative research could lead the way in producing inexpensive, disposable MFCs with controllable degradation
Modern approaches to marine antifouling coatings
Full text linkMarine structures such as platforms, jetties and ship hulls are subject to diverse and severe biofouling. Methods for inhibiting both organic and inorganic growth on wetted substrates are varied but most antifouling systems take the form of protective coatings. Biofouling can negatively affect the hydrodynamics of a hull by increasing the required propulsive power and the fuel consumption. This paper reviews the development of antifouling coatings for the prevention of marine biological fouling. As a result of the 2001 International Maritime Organization (IMO) ban on tributyltin (TBT), replacement antifouling coatings have to be environmentally acceptable as well as maintain a long life. Tin-free self-polishing copolymer (SPC) and foul release technologies are current applications but many alternatives have been suggested. Modern approaches to environmentally effective antifouling systems and their performance are highlighted
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
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