Higher Sensitivity of Human Auditory Nerve Fibers to Positive Electrical Currents

Most contemporary cochlear implants (CIs) stimulate the auditory nerve with trains of amplitude-modulated, symmetric biphasic pulses. Although both polarities of a pulse can depolarize the nerve fibers and generate action potentials, it remains unknown which of the two (positive or negative) phases has the stronger effect. Understanding the effects of pulse polarity will help to optimize the stimulation protocols and to deliver the most relevant information to the implant listeners. Animal experiments have shown that cathodic (negative) current flows are more effective than anodic (positive) ones in eliciting neural responses, and this finding has motivated the development of novel speech-processing algorithms. In this study, we show electrophysiologically and psychophysically that the human auditory system exhibits the opposite pattern, being more sensitive to anodic stimulation. We measured electrically evoked compound action potentials in CI listeners for phase-separated pulses, allowing us to tease out the responses to each of the two opposite-polarity phases. At an equal stimulus level, the anodic phase yielded the larger response. Furthermore, a measure of psychophysical masking patterns revealed that this polarity difference was still present at higher levels of the auditory system and was therefore not solely due to antidromic propagation of the neural response. This finding may relate to a particular orientation of the nerve fibers relative to the electrode or to a substantial degeneration and demyelination of the peripheral processes. Potential applications to improve CI speech-processing strategies are discussed

Dissertatio Medica Inauguralis, De Venenis Et Antidotis

Quam ... Johannis vanden Honert ... Eruditorum Examini submittit Janus Loncq ...Vorlageform des Erscheinungsvermerks: Lugduni Bat. Apud Petrum DelfosLeiden, Univ., Diss, 174

Estimating the continuous risk of accidents occurring in the mining industry in South Africa

CITATION: Van Den Honert, A. F. & Vlok, P. J. 2015. Estimating the continuous risk of accidents occurring in the mining industry in South Africa. South African Journal of Industrial Engineering, 26(3):71-85, doi:10.7166/26-3-1121.The original publication is available at http://sajie.journals.ac.zaThis study contributes to the on-going efforts to improve occupational safety in the mining industry by creating a model capable of predicting the continuous risk of occupational accidents occurring. Contributing factors were identified and their sensitivity quantified. The approach included using an Artificial Neural Network (ANN) to identify patterns between the input attributes and to predict the continuous risk of accidents occurring. The predictive Artificial Neural Network (ANN) model used in this research was created, trained, and validated in the form of a case study with data from a platinum mine near Rustenburg in South Africa. This resulted in meaningful correlation between the predicted continuous risk and actual accidents.Hierdie studie probeer ’n bydrae lewer om beroepsveiligheid in die mynbedryf te verbeter deur ’n model te skep wat in staat is daartoe om die voortdurende risiko’s van moontlike werksongelukke te voorspel. Bydraende faktore is geïdentifiseer en hulle sensitiwiteit is gekwantifiseer. Die benadering sluit in die gebruik van ’n Kunsmatige Neurale Netwerk (ANN) wat patrone identifiseer tussen die bydraende kenmerke en om die aanhoudende risiko van ongelukke te voorspel. Hierdie model was geskep, opgelei en gevalideer tydens ’n gevallestudie waar die data verkry is van ’n platinum-myn naby Rustenburg in Suid-Afrika. Die gevolgtrekking was dat ’n betekenisvolle korrelasie tussen die voorspelbare voortdurende risiko’s en werklike ongelukke bestaan.http://sajie.journals.ac.za/pub/article/view/1121Publisher's versio

The Root Zone: Soil Physics and Beyond

This special section of Vadose Zone Journal (VZJ) contains 15 contributions focusing on the physical, biological, and chemical aspects of water and solute transport into and through the soil root zone, including root water and solute uptake. The papers stem from presentations at the 2016 Kirkham Conference, “The Root Zone: Soil Physics and Beyond,” which took place at the Sede Boqer campus of Ben-Gurion University of the Negev, Israel, during 10 to 14 April (https://www.soils.org/membership/divisions/soil-physics-and-hydrology/kirkham-conferences). Much consensus existed at the conference for a special VZJ section to reflect the importance of the soil root zone from many disciplinary perspectives (soil, environmental, agricultural, hydrologic, and atmospheric) and the complexity of the basic processes involved. The contributions deal with root zone processes at different scales and from different disciplinary viewpoints, while covering a broad range of topics from the very theoretical to important practical applications. Special emphasis is on novel measurement and modeling tools at various scales and the need for interdisciplinary research