Ceramic Soil Microbial Fuel Cells Sensors for Early Detection of Eutrophication

The increasing use of fertilisers rises the risk of eutrophication, a sudden algal bloom that seriously damage ecosystems due to critical oxygen depletion. Continuous monitoring of oxygen in environmental waters could improve the detection of eutrophication and prevent anoxic conditions. However, online and in situ dissolved oxygen sensors are yet to be implemented due to poor portability and power requirements. Here, we propose a ceramic soil microbial fuel cell as a self-powered sensor for algal growth detection via monitoring of dissolved oxygen in water. The sensor signal follows the characteristic photosynthetic cycle, with a maximum day current of 0.18 ± 0.2 mA and a minimum night current of 0.06 ± 0.34 mA, which correlates with dissolved oxygen (R2 = 0.85 (day); R2= 0.5 (night)) and algal concentration (R2 = 0.63). A saturated design of experiments on seven factors suggests that temperature, dissolved oxygen, nitrates, and pH are the most influential operational factors in the voltage output. Moreover, operating the system at maximum power point (Rext = 2 kΩ) improves the sensor sensitivity. To the best of our knowledge, this is the first proposed MFC-based biosensor for in-field, early detection of eutrophic events.

Construction of Super Saturated Design Using Hadamard Matrix and Its E(S2) Optimality

Supersaturated design is essentially a fractional factorial design in which the number of potential effects is greater than the number of runs. In this paper, a super-saturated design is constructed using half fraction of Hadamard matrix of order N. A Hadamard matrix of order N, can investigate up to N 2 factors in N/2 runs. Result is shown in N = 16. The extension to larger N is adaptable.

Algebraic geometry of Poisson regression

Designing experiments for generalized linear models is difficultbecause optimal designs depend on unknown parameters. Here weinvestigate local optimality. We propose to study for a given designits region of optimality in parameter space. Often these regions aresemi-algebraic and feature interesting symmetries. We demonstratethis with the Rasch Poisson counts model. For any given interactionorder between the explanatory variables we give a characterization ofthe regions of optimality of a special saturated design. This extendsknown results from the case of no interaction. We also give analgebraic and geometric perspective on optimality of experimentaldesigns for the Rasch Poisson counts model using polyhedral andspectrahedral geometry.