8 research outputs found
A Biophysical Model of the Inner Hair Cell: The Contribution of Potassium Currents to Peripheral Auditory Compression
The term peripheral auditory compression refers to the fact that the whole range of audible sound pressure levels is mapped into a narrower range of auditory nerve responses. Peripheral compression is the by-product of independent compressive processes occurring at the level of the basilar membrane, the inner hair cell (IHC), and the auditory nerve synapse. Here, an electrical-circuit equivalent of an IHC is used to look into the compression contributed by the IHC. The model includes a mechanically driven transducer potassium (K+) conductance and two time- and voltage-dependent basolateral K+ conductances: one with fast and one with slow kinetics. Special attention is paid to faithfully implement the activation kinetics of these basolateral conductances. Optimum model parameters are provided to account for previously reported in vitro observations that demonstrate the compression associated with the gating of the transducer and of the basolateral channels. Without having to readjust its parameters, the model also accounts for the in vivo nonlinear IHC transfer characteristics. Model simulations are then used to investigate the relative contribution of the transducer and basolateral K+ currents to the nonlinear IHC input/output functions in vivo. The simulations suggest that the voltage-dependent activation of the basolateral currents compresses the DC potential for stereocilia displacements above approximately 5Â nm. The degree of compression exceeds 2-to-1 and is similar for all stimulation frequencies. The AC potential is compressed in a similar way, but only for frequencies below 800Â Hz. The simulations further suggest that the nonlinear gating of the transducer current is responsible for the expansive growth of the DC potential with increasing sound level (slope of 2Â dB/dB) at low sound pressure levels
Lower ototoxicity and absence of hidden hearing loss point to gentamicin C1a and apramycin as promising antibiotics for clinical use
Conducting Polymer Nanomaterials and Their Applications
A paradigm shift takes place in the fabrication of conducting polymers from
bulky features with microsize to ultrafine features with nanometer range. Novel conducting
polymer nanomaterials require the potential to control synthetic approaches
of conducting polymer on molecular and atomic levels. In this article, the synthetic
methodology of conducting polymer has been briefly considered with chemical oxidation
polymerization and electrochemical polymerization. The recent achievements in the
fabrication of conducting polymer nanomaterials have been extensively reviewed with
respect to soft template method, hard template method and template-free method. It
also details the morphological spectrum of conducting polymer nanomaterials such as
nanoparticle, core-shell nanomaterial, hollow nanosphere, nanofiber/nanorod, nanotube,
thin film and nanopattern and nanocomposite. In addition, their applications are discussed
under nanometer-sized dimension.This work has been financially supported by the Brain Korea 21 program
of the Korean Ministry of Education and the Hyperstructured Organic Materials
Research Center supported by Korea Science and Engineering Foundation