Alkaline fuel cells: contemporary advancement and limitations

ZeTek Power recently introduced mass manufacturable and cost effective alkaline fuel cells on the market. Today's research is focused on further improvement both in terms of performance increase and cost reduction. This research is classically performed using small (4 cm²) experimental electrodes in the half-cell configuration. This allows the primary electrochemical losses in an anode or cathode to be determined independently. Additional performance losses occur when one integrates large electrodes into a module of 24 cells and in a stack comprised of many modules. By comparing the performance of half-cell experiments to that of modules, these losses can be distinguished and addressed. The information thus obtained, both for the small electrodes and in up-scaling is vital if one is to identify the key areas in which improvement is possible and where to focus future research. Furthermore, the identification of the losses in a module and system allows us to predict the final performance from half-cell measurements of a new laboratory scale experimental electrode.     

Radiation induced dissolution of UO2 based nuclear fuel – A critical review of predictive modelling approaches

Radiation induced dissolution of uranium dioxide (UO₂) nuclear fuel and the consequent release of radionuclides to intruding groundwater are key-processes in the safety analysis of future deep geological repositories for spent nuclear fuel. For several decades, these processes have been studied experimentally using both spent fuel and various types of simulated spent fuels. The latter have been employed since it is difficult to draw mechanistic conclusions from real spent nuclear fuel experiments. Several predictive modelling approaches have been developed over the last two decades. These models are largely based on experimental observations. In this work we have performed a critical review of the modelling approaches developed based on the large body of chemical and electrochemical experimental data. The main conclusions are: (1) the use of measured interfacial rate constants give results in generally good agreement with experimental results compared to simulations where homogeneous rate constants are used; (2) the use of spatial dose rate distributions is particularly important when simulating the behaviour over short time periods; and (3) the steady-state approach (the rate of oxidant consumption is equal to the rate of oxidant production) provides a simple but fairly accurate alternative, but errors in the reaction mechanism and in the kinetic parameters used may not be revealed by simple benchmarking. It is essential to use experimentally determined rate constants and verified reaction mechanisms, irrespective of whether the approach is chemical or electrochemical.     

Comparison of semi-automatic and automatic data acquisition methods for studying three-dimensional distributions of large neuronal populations and axonal plexuses

Neuroanatomy is in need of high throughput methods for reliably recording the distribution of tissue elements across large brain regions. We compared two methods for recording the spatial distribution of identified neuronal elements such as tracer labelled cell bodies or axonal plexuses. The methods compared were computerized image-combining microscopy (semi-automatic method), which is a user controlled method providing feedback during digitization, and digital camera technology with image analysis software (automatic method). Both methods were applied to biotinylated dextran amine labelled axonal plexuses and FluoroRuby labelled neuronal cell bodies, in the pontine nuclei of the rat. Coordinates were assigned to the labelled elements using both methods. The ensuing distribution patterns were compared, section by section, and in three-dimensional reconstruction. The experienced investigator, using the semi-automatic method, could detect individual axons, fragments of axons, weakly labelled elements, and overlapping cell bodies, better than the automatic system. Nevertheless, both methods detected the overall distribution of the labelled axons and cells investigated. Automatic methods provide opportunities for efficient large-scale data acquisition of labelled neuronal elements.     

A MIXTURE MODEL CLASSIFIER AND ITS APPLICATION ON THE BIOMEDICAL TIME SERIES

This article presents a methodology based on the mixture model to classify the real biomedical time series. The mixture model is shown to be an efficient probabilistic density estimation scheme aimed at approximating the posterior probability distribution of a certain class of data. The approximation is conducted by employing a weighted mixture of a finite number of Gaussian kernels whose parameters and mixing coefficients are estimated iteratively through a maximum likelihood method. A database of the real electrocardiogram (ECG) time series of out-of-hospital cardiac arrest patients suffering ventricular fibrillation (VF) with known defibrillation outcomes was adopted to evaluate the performance of this model and confirm its efficiency compared with other classification methods.     

Effects of transferring glacier-fed water to a clear-water mountain river on the production and food organisms of brown trout (Salmo trutta L.) in Southern Norway

The effects of transferring glacier-fed water to a clear-water river on production and food organisms of brown trout (Salmo trutta L.) were investigated in a mountain river, in southern Norway. Production in unregulated fluvial habitat was 271.5 g 100 m^?2 yr^?1 compared with 103.1 g 100 m^?2 yr^?1 in a glacier-fed reach of the river. This difference was due to low fish density and recruitment rate. The growth rate, at least for younger fish (2+ to 4+ age groups), was significantly higher in the regulated reach of the river. The main difference in food composition was the low abundance of crustaceans Eurycercus lamellatus and Gammarus lacustris in the regulated reach. Trichopterans were the main diet component in both sites.     

Information‐driven robotic sampling in the coastal ocean

Efficient sampling of coastal ocean processes, especially mechanisms such as upwelling and internal waves and their influence on primary production, is critical for understanding our changing oceans. Coupling robotic sampling with ocean models provides an effective approach to adaptively sample such features. We present methods that capitalize on information from ocean models and in situ measurements, using Gaussian process modeling and objective functions, allowing sampling efforts to be concentrated to regions with high scientific interest. We demonstrate how to combine and correlate marine data from autonomous underwater vehicles, model forecasts, remote sensing satellite, buoy, and ship‐based measurements, as a means to cross‐validate and improve ocean model accuracy, in addition to resolving upper water‐column interactions. Our work is focused on the west coast of Mid‐Norway where significant influx of Atlantic Water produces a rich and complex physical–biological coupling, which is hard to measure and characterize due to the harsh environmental conditions. Results from both simulation and full‐scale sea trials are presented.     

Hamming weights and Betti numbers of Stanley–Reisner rings associated to matroids

To each linear code $C$ over a finite field we associate the matroid $M(C)$ of its parity check matrix. For any matroid $M$ one can define its generalized Hamming weights, and if a matroid is associated to such a parity check matrix, and thus of type $M(C)$ , these weights are the same as those of the code $C$ . In our main result we show how the weights $d_1,\ldots ,d_k$ of a matroid $M$ are determined by the $\mathbb N $ -graded Betti numbers of the Stanley–Reisner ring of the simplicial complex whose faces are the independent sets of $M$ , and derive some consequences. We also give examples which give negative results concerning other types of (global) Betti numbers, and using other examples we show that the generalized Hamming weights do not in general determine the $\mathbb N $ -graded Betti numbers of the Stanley–Reisner ring. The negative examples all come from matroids of type $M(C)$ .