Wavelet methods for spike detection in mouse renal sympathetic nerve activity

Abnormal autonomic nerve traffic has been associated with a number of peripheral neuropathies and cardiovascular disorders prompting the development of genetically altered mice to study the genetic and molecular components of these diseases. Autonomic function in mice can be assessed by directly recording sympathetic nerve activity. However, murine sympathetic spikes are typically detected using a manually adjusted voltage threshold and no unsupervised detection methods have been developed for the mouse. Therefore, we tested the performance of several unsupervised spike detection algorithms on simulated murine renal sympathetic nerve recordings, including an automated amplitude discriminator and wavelet-based detection methods which used both the discrete wavelet transform (DWT) and the stationary wavelet transform (SWT) and several wavelet threshold rules. The parameters of the wavelet methods were optimized by comparing basal sympathetic activity to postmortem recordings and recordings made during pharmacological suppression and enhancement of sympathetic activity. In general, SWT methods were found to outperform amplitude discriminators and DWT methods with similar wavelet coefficient thresholding algorithms when presented with simulations with varied mean spike rates and signal-to-noise ratios. A SWT method which estimates the noise level using a "noise-only" wavelet scale and then selectively thresholds scales containing the physiologically important signal information was found to have the most robust spike detection. The proposed noise-level estimation method was also successfully validated during pharmacological interventions.     

Carbon dioxide capture using solid sorbents in a fluidized bed with reduced pressure regeneration in a downer

The most common technology for postcombustion CO₂ capture for existing power plants is the amine solvent scrubber. The energy consumption for capturing CO₂ from flue gases using amine solvent technology is 15 to 30% of the power plant electricity production. Hence, there is a need to develop more efficient methods of removing CO₂. Here, we show a novel design, obtained using multiphase CFD, and of a fluidized‐bed reduced pressure regenerator, coupled with a fluidized‐bed sorber, which has the potential to reduce the energy consumption. The undesirable core‐annular flow regime in the riser‐sorber is eliminated using multiple jet inlets and large particles leading to a shorter height. Up to 88% of the heat liberated in the riser‐sorber is recovered in the downer‐regenerator. © 2013 American Institute of Chemical Engineers AIChE J, 59: 4519–4537, 2013