Keele University

About: Keele University is a education organization based out in Newcastle-under-Lyme, United Kingdom. It is known for research contribution in the topics: Population & Stars. The organization has 11318 authors who have published 26323 publications receiving 894671 citations. The organization is also known as: Keele University.

Enhancement of vowel coding for cochlear implants by addition of noise

Abstract: Profoundly deaf people, who gain no benefit from conventional hearing aids, can receive speech cues by direct electrical stimulation of the cochlear nerve1,2. This is achieved by an electronic device, a cochlear implant, which is surgically inserted into the ear. Here we show physiological results from the isolated sciatic nerve of the toad Xenopus laevis, used to predict the response of the human cochlear nerve to vowels coded by a cochlear implant. These results suggest that standard analogue cochlear implants do not evoke the patterns of neural excitation that are normally associated with acoustic stimulation. Adding noise to the stimulus, however, enhanced distinguishing features of the vowel encoded by the fine time structure of neural discharges. On the basis of these results, and those concerning stochastic resonance3–5, we advocate a cochlear implant coding strategy in which noise is deliberately added to cochlear implant signals.

Fundamental properties of core-collapse Supernova and GRB progenitors: predicting the look of massive stars before death

Abstract: We investigate the fundamental properties of core-collapse supernova (SN) progenitors from single stars at solar metallicity. For this purpose, we combine Geneva stellar evolutionary models with initial masses of M ini = 20−120 M ⊙ with atmospheric and wind models using the radiative transfer code CMFGEN. We provide synthetic photometry and high-resolution spectra of hot stars at the pre-SN stage. For models with M ini = 9−20 M ⊙ , we supplement our analysis using publicly available MARCS model atmospheres of RSGs to estimate their synthetic photometry. We employ well-established observational criteria of spectroscopic classification and find that, depending on their initial mass and rotation, massive stars end their lives as red supergiants (RSG), yellow hypergiants (YHG), luminous blue variables (LBV), and Wolf-Rayet (WR) stars of the WN and WO spectral types. For rotating models, we obtained the following types of SN progenitors: WO1–3 (M ini ≥ 32 M ⊙ ), WN10–11 (25 ini ⊙ ), LBV (20 ≤ M ini ≤ 25 M ⊙ ), G1 Ia+ (18 ini ⊙ ), and RSGs (9 ≤ M ini ≤ 18 M ⊙ ). For non-rotating models, we found spectral types WO1–3 (M ini > 40 M ⊙ ), WN7–8 (25 ini ≤ 40 M ⊙ ), WN11h/LBV (20 ini ≤ 25 M ⊙ ), and RSGs (9 ≤ M ini ≤ 20 M ⊙ ). Our rotating models indicate that SN IIP progenitors are all RSG, SN IIL/b progenitors are 56% LBVs and 44% YHGs, SN Ib progenitors are 96% WN10-11 and 4% WOs, and SN Ic progenitors are all WO stars. We find that the most massive and luminous SN progenitors are not necessarily the brightest ones in a given filter, since this depends on their luminosity, temperature, wind density, and the way the spectral energy distribution compares to a filter bandpass. We find that SN IIP progenitors (RSGs) are bright in the RIJHK S filters and faint in the UB filters. SN IIL/b progenitors (LBVs and YHGs), and SN Ib progenitors (WNs) are relatively bright in optical/infrared filters, while SN Ic progenitors (WOs) are faint in all optical filters. We argue that SN Ib and Ic progenitors from single stars should be undetectable in the available pre-explosion images with the current magnitude limits, in agreement with observational results.

The effects of behavioural factors in investment decision-making: a survey of institutional investors operating at the Nairobi Stock Exchange

Abstract: This study investigated the role of behavioural finance and investor psychology in investment decision-making at the Nairobi Stock Exchange with special reference to institutional investors. Using a sample of 23 institutional investors, the study established that behavioural factors such as representativeness, overconfidence, anchoring, gambler's fallacy, availability bias, loss aversion, regret aversion and mental accounting affected the decisions of the institutional investors operating at the NSE. Moreover, these investors made reference to the trading activity of the other institutional investors and often exhibited an institutional-herding behaviour in their investment decision-making.