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Subthreshold-level activities in neurons play a crucial role in neuronal oscillations. These small-amplitude oscillations have been suggested to be involved in synaptic plasticity and in determining the frequency of network oscillations. Subthreshold membrane oscillations (STOs) and subthreshold resonance oscillations (SROs) are the main constituents of subthreshold-level activities in neurons. In this study, a general theoretical framework for analyzing the mechanisms underlying STOs and SROs in neurons is presented. Results showed that the resting membrane potential and the hyperpolarization-activated potassium channel ([Formula: see text]-channel) affect the subthreshold-level activities in stellate cells. The contribution of [Formula: see text]-channel on resonance is attributed to its large time constant, which produces the time lag between [Formula: see text] and the membrane potential. Conversely, the persistent sodium channels (Nap-channels) only play an amplifying role in these neurons.

The results of experimental research of acoustic emission signals at destruction of different diameter graphite cylindrical models are considered. It is stated that dependence of area under the curve of acoustic emission signals is directly proportional to the area of an appearing crack. First Published Online: 14 Oct 2010

Dye-Sensitized Solar Cells (DSSCs) are currently the leading photovoltaic device among third generation solar cells due to their low production cost, ease of manufacturing and relatively high conversion efficiency. One of the most expensive component of the DSSC is the highly efficient Platinum Counter Electrode (Pt CE) but considerable cost reductions can be achieved by changing it to carbon-based CEs. Therefore, the objective of this research is to study a type of hydrophilic carbon (HC) particle for the first time as a novel CE in DSSCs. The easy synthesis, low cost and reasonable electrocatalytic property of the HC particle may help the DSSC in commercialization by making it more environmental friendly and a less expensive device. In this research, the HC past was prepared and deposited on FTO glass as a CE with different thickness ranging from 1 to 3μm. The effects of the thickness and morphology of a HC CE on the performance of a DSSC were then investigated. The increase in the HC film gradually increase the surface roughness of the electrodes. The HC CE with 2μm thickness showed the highest catalytic activity and the lowest charge transfer resistance among other electrodes. As a result, the highest energy conversion efficiency of approximately 3% was achieved by HC CE with 2 μm thickness compare to the Pt electrode prepared at the same experimental condition, which achieved 3.5%. Thus, HC CE has the potential to replace the rare and expensive Pt CE in DSSC.

Subthreshold oscillations in combination with large-amplitude oscillations generate mixed-mode oscillations (MMOs), which mediate various spatial and temporal cognition and memory processes and behavioral motor tasks. Although many studies have shown that canard theory is a reliable method to investigate the properties underlying the MMOs phenomena, the relationship between the results obtained by applying canard theory and conductance-based models of neurons and their electrophysiological mechanisms are still not well understood. The goal of this study was to apply canard theory to the conductance-based model of pyramidal neurons in layer V of the Entorhinal Cortex to investigate the properties of MMOs under antiepileptic drug conditions (i.e., when persistent sodium current is inhibited). We investigated not only the mathematical properties of MMOs in these neurons, but also the electrophysiological mechanisms that shape spike clustering. Our results show that pyramidal neurons can display two types of MMOs and the magnitude of the slow potassium current determines whether MMOs of type I or type II would emerge. Our results also indicate that slow potassium currents with large time constant have significant impact on generating the MMOs, as opposed to fast inward currents. Our results provide complete characterization of the subthreshold activities in MMOs in pyramidal neurons and provide explanation to experimental studies that showed MMOs of type I or type II in pyramidal neurons under antiepileptic drug conditions.