Microbial fuel cell technology for measurement of microbial respiration of lactate as an example of bioremediation amendment

Microbial fuel cell (MFC) based sensing was explored to provide for the development of an insitu bioremediation monitoring approach for substrate concentrations and microbial respiration rates. MFC systems were examined in column systems where Shewanella oneidensis MR1 used an external electron acceptor (an electrode) to metabolize lactate (a bioremediation additive) to acetate. Column systems were operated with varying influent lactate concentrations (0-41mM) and monitored for current generation (0.01-0.39mA). Biological current generation paralleled bulk phase lactate concentration both in the influent and in the bulk phase at the anode; current values were correlated to lactate concentration at the anode (R 2=0.9), The electrical signal provided real-time information for electron donor availability and biological activity. These results have practical implications for efficient and inexpensive real-time monitoring of insitu bioremediation processes where information on substrate concentrations is often difficult to obtain and where information on the rate and nature of metabolic processes is neede

Rate-dependent plasticity models derived from potential functions

The constitutive behavior of the rate dependent plasticity models derived from potential functions was discussed. The potential functions were energy function and the flow or force potential. These potentials were related through a series of Lengendre-Fenchel transformations. After the specification of the potentials, an entirely standardized procedure was adopted to derive the response. There is a transparent link between the terms that appear in the potentials, and the results in terms of constitutive response

Coupled numerical modelling of progressive failure in creeping constrained landslides under steady state and transient state conditions

ABSTRACT Creeping landslides are a threat to many mountainous communities. Some of these landslides are constraint either artificially or naturally and are slowing down. This slowing down might cause a false impression of safety even though a subsequent reacceleration of the landslide cannot be ruled out. Herein a numerical method is presented that can capture several features that have been observed in the creeping Brattas landslide which affects the ski resort town of St. Moritz. Extensive field observations and laboratory testing have revealed a variety of coupled phenomena, which are also common to other constrained landslides. A simple finite difference algorithm combined with a mechanical constitutive model is presented to simulate these phenomena along the entire slope. The model is based on the mechanism of progressive failure in a zone of intense shearing along the slip surface. Also the effect of rate dependent shear resistance is captured and two different rate dependency relations are analysed. Combining this mechanism with visco-elastic behaviour in the landslide body explains a phase of gradual slowing down of the landslide until 1991. Subsequent acceleration of the landslide can be described by visco-plastic yielding in a zone at the landslide foot where the pressure is close to passive earth pressure. Observed large differences in the velocity of the landslide between its upper and lower sections are attributed to secondary compression. The coupled numerical procedure is also capable of capturing not only the steady state behaviour but also the slope's reaction to precipitation (i.e. the transient state) by introducing a simple linear reservoir type model to relate changes in pore pressure to observed precipitation. The numerical procedure can be used for back-calculating parameters of the slope as well as for predictive purposes. These predictions indicate that further significant deformations in the constructed zone of the landslide have to be expected which makes additional observations and monitoring of sensitive structures essential. In combination with probabilistic models for exposures (e.g. development of precipitation and duration cold periods) the numerical model will also allow for proper risk analysis in the area affected by the Brattas landslide

Basin Sediments Geometry and Strength as Controls for Post-Failure Emplacement Style of Alpine Sub-Lacustrine Landslides

Predicting the evolution of underwater mass movements in their post-failure stage is vital for risk assessment of offshore structures and ensuring safety of coastal communities threatened by tsunami waves. In the absence of sedimentological and geotechnical data, variability of the post-failure behavior in a specific marine or lacustrine setting is often attributed to predisposition factors such as the slope height-drop and depth to the basal shear surface. In this paper, the contribution of other geometrical parameters such as the slope inclination and the relative thickness of the frontal basin sediments is investigated using a coupled Eulerian-Lagrangian finite element framework. An emphasis is given to the important role of the strength difference between the slope and frontal basin sediments. The suggested framework is first validated against the well-documented Zinnen slide in Lake Lucerne (Switzerland), successfully reproducing the post-failure geometry and capturing the main features observed in published seismic profiles. It is then applied in a parametric study to illustrate the decisive role of the frontal basin sediments in determining the post-failure geometry of underwater mass wasting in similar settings.ISSN:2169-9313ISSN:0148-0227ISSN:2169-935