A microbial fuel cell in contaminated ground delineated by electrical self-potential and normalized induced polarization data

There is a growing interest in the use of geophysical methods to aid investigation and monitoring of complex biogeochemical environments, for example delineation of contaminants and microbial activity related to land contamination. We combined geophysical monitoring with chemical and microbiological analysis to create a conceptual biogeochemical model of processes around a contaminant plume within a manufactured gas plant site. Self-potential, induced polarization and electrical resistivity techniques were used to monitor the plume. We propose that an exceptionally strong (>800 mV peak to peak) dipolar SP anomaly represents a microbial fuel cell operating in the subsurface. The electromagnetic and electrical geophysical data delineated a shallow aerobic perched water body containing conductive gasworks waste which acts as the abiotic cathode of microbial fuel cell. This is separated from the plume below by a thin clay layer across the site. Microbiological evidence suggests that degradation of organic contaminants in the plume is dominated by the presence of ammonium and its subsequent degradation. We propose that the degradation of contaminants by microbial communities at the edge of the plume provides a source of electrons and acts as the anode of the fuel cell. We hypothesize that ions and electrons are transferred through the clay layer that was punctured during the trial pitting phase of the investigation. This is inferred to act as an electronic conductor connecting the biologically mediated anode to the abiotic cathode. Integrated electrical geophysical techniques appear well suited to act as rapid, low cost sustainable tools to monitor biodegradation.

Jettisoning Ballast or Fuel? Caudal Autotomy and Locomotory Energetics of the Cape Dwarf Gecko Lygodactylus capensis (Gekkonidae)

Many lizard species will shed their tail as a defensive response (e.g., to escape a putative predator or aggressive conspecific). This caudal autotomy incurs a number of costs as a result of loss of the tail itself, loss of resources (i.e., stored in the tail or due to the cost of regeneration), and altered behavior. Few studies have examined the metabolic costs of caudal autotomy. A previous study demonstrated that geckos can move faster after tail loss as a result of reduced weight or friction with the substrate; however, there are no data for the effects of caudal autotomy on locomotory energetics. We examined the effect of tail loss on locomotory costs in the Cape dwarf gecko Lygodactylus capensis (similar to 0.9 g) using a novel method for collecting data on small lizards, a method previously used for arthropods. We measured CO2 production during 5-10 min of exhaustive exercise (in response to stimulus) and during a 45-min recovery period. During exercise, we measured speed (for each meter moved) as well as total distance traveled. Contrary to our expectations, tailless geckos overall expended less effort in escape running, moving both slower and for a shorter distance, compared with when they were intact. Tailless geckos also exhibited lower excess CO2 production (CO2 production in excess of normal resting metabolic rate) during exercising. This may be due to reduced metabolically active tissue (tails represent 8.7% of their initial body mass). An alternative suggestion is that a change in energy substrate use may take place after tail loss. This is an intriguing finding that warrants future biochemical investigation before we can predict the relative costs of tail loss that lizards might experience under natural conditions.

Effect of the incorporation of hydroxy-terminated liquid silicones on the cure characteristics, morphology, and release of a model protein from silicone elastomer-covered rods

Silicone elastomer systems have previously been shown to offer potential for the sustained release of protein therapeutics. However, the general requirement for the incorporation of large amounts of release enhancing solid excipients to achieve therapeutically effective release rates from these otherwise hydrophobic polymer systems can detrimentally affect the viscosity of the precure silicone elastomer mixture and its curing characteristics. The increase in viscosity necessitates the use of higher operating pressures in manufacture, resulting in higher shear stresses that are often detrimental to the structural integrity of the incorporated protein. The addition of liquid silicones increases the initial tan delta value and the tan delta values in the early stages of curing by increasing the liquid character (G '') of the silicone elastomer system and reducing its elastic character (G'), thereby reducing the shear stress placed on the formulation during manufacture and minimizing the potential for protein degradation. However, SEM analysis has demonstrated that if the liquid character of the silicone elastomer is too high, the formulation will be unable to fill the mold during manufacture. This study demonstrates that incorporation of liquid hydroxy-terminated polydimethylsiloxanes into addition-cure silicone elastomer-covered rod formulations can both effectively lower the viscosity of the precured silicone elastomer and enhance the release rate of the model therapeutic protein bovine serum albumin. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011