Oculomotor responses in emmetropia and myopia

It has been proposed that early-onset myopia (EOM) i.e. myopia onset before the age of 15 is primarily inherited whereas late-onset myopia (LOM) i.e. myopia onset after the age of 16 is induced by environmental factors, principally sustained near vision. No consensus exists as to which aspect of the near vision response; accommodation, vergence or their synergistic cross links promotes LOM development. Furthermore, the mechanism by which near vision could induce elongation of posterior chamber is obscure although there is evidence to show that ciliary muscle tone plays an important role. By comparing accommodation and vergence responses of emmetropes (EMMs), EOMs and LOMs under both open- and closed-loop conditions, this thesis aims to define further the oculomotor correlates of myopic development. A Canon Autoref R-1 optometer was used to measure accommodation responses while an Apple IIe controlled the flashed Maddox Rod sequence used when measuring vergence. Both techniques permitted open- and closed-loop measures to be obtained. The results presented demonstrate that it is unlikely that those individuals susceptible to LOM can be distinguished with regard to oculomotor responses or innervational characteristics of the ciliary muscle. The aetiology of LOM may be associated with ciliary muscle function but account needs to be taken of interactions between the ciliary muscle, choriod, sclera and introcular pressure and further research is necessary before those EMMs susceptible to LOM can be identified.

The clinical utility of the middle latency and 40Hz auditory evoked potentials in audiological electrodiagnosis

The two elcctrophysiological tests currently favoured in the clinical measurement of hearing threshold arc the brainstorm evoked potential (BAEP) and the slow vertex response (SVR). However, both tests possess disadvantages. The BAEP is the test of choice in younger patients as it is stable at all levels of arousal, but little information has been obtained to date at a range of frequencies. The SVR is frequency specific but is unreliable in certain adult subjects and is unstable during sleep or in young children. These deficiencies have prompted research into a third group of potentials, the middle latency response (MLR) and the 40HZ responses. This research has compared the SVR and 40HZ response in waking adults and reports that the 40HZ test can provide a viable alternative to the SVR provided that a high degree of subject relaxation is ensured. A second study examined the morphology of the MLR and 40HZ during sleep. This work suggested that these potentials arc markedly different during sleep and that methodological factors have been responsible for masking these changes in previous studies. The clinical possibilities of tone pip BAEPs were then examined as these components were proved to be the only stable responses present in sleep. It was found that threshold estimates to 5OOHz, lOOOHz and 4000Hz stimuli could be made to within 15dBSL in most cases. A final study looked more closely at methods of obtaining frequency specific information in sleeping subjects. Threshold estimates were made using established BAEP parameters and this was compared to a 40HZ procedure which recorded a series of BAEPs over a 100msec. time sweep. Results indicated that the 40mHz procedure was superior to existing techniques in estimating threshold to low frequency stimuli. This research has confirmed a role for the MLR and 40Hz response as alternative measures of hearing capability in waking subjects and proposes that the 40Hz technique is useful in measuring frequency specific thresholds although the responses recorded derive primarily from the brainstem.

Translation strategies and cross-cultural contraints : a case study of the translation of advertising texts

Since the transfer of a message between two cultures very frequently takes place through the medium of a written text qua communicative event, it would seem useful to attempt to ascertain whether there is any kind of pattern in the use of strategies for the effective interlingual transfer of this message. Awareness of potentially successful strategies, within the constraints of context, text type, intended TL function and TL reader profile will enhance quality and cost-effectiveness (time, effort, financial costs) in the production of the target text. Through contrastive analysis of pairs of advertising texts, SL and TL, French and English, this study will attempt to identify the nature of some recurring choices made by different translators in the attempt to recreate ST information in the TL in such a manner as to reproduce as closely as possible the informative, persuasive and affective functions of the text as advertising material. Whilst recurrence may be seen to be significant in terms of illustrating tendencies with regard to the solution of problems of translation, this would not necessarily be taken as confirmation of the existence of pre-determined or prescriptive rules. These tendencies could, however, be taken as a guide to potential solutions to certain kinds of context-bound and text-type specific problem. Analysis of translated text-pairs taken from the field of advertising should produce examples of constraints posed by the need to select the content, tone and form of the Target Text, in order to ensure maximum efficacy of persuasive effect and to ensure the desired outcome, as determined by the Source Text function. When evaluating the success of a translated advertising text, constraints could be defined in terms of the culture-specific references or assumptions on which a Source Text may build in order to achieve its intended communicative function within the target community.

A novel binaural pitch elicited by phase-modulated noise:MEG and psychophysical observations

Binaural pitches are auditory percepts that emerge from combined inputs to the ears but that cannot be heard if the stimulus is presented to either ear alone. Here, we describe a binaural pitch that is not easily accommodated within current models of binaural processing. Convergent magnetoencephalography (MEG) and psychophysical measurements were used to characterize the pitch, heard when band-limited noise had a rapidly changing interaural phase difference. Several interesting features emerged: First, the pitch was perceptually lateralized, in agreement with the lateralization of the evoked changes in MEG spectral power, and its salience depended on dichotic binaural presentation. Second, the frequency of the pure tone that matched the binaural pitch lay within a lower spectral sideband of the phase-modulated noise and followed the frequency of that sideband when the modulation frequency or center frequency and bandwidth of the noise changed. Thus, the binaural pitch depended on the processing of binaural information in that lower sideband.

Inhibition of pyruvate kinase M2 by reactive oxygen species contributes to the development of pulmonary arterial hypertension

Aims: Pulmonary arterial hypertension [1] is a proliferative disorder associated with enhanced proliferation and suppressed apoptosis of pulmonary artery smooth muscle cells (PASMCs). Reactive oxygen species (ROS) is implicated in the development of PAH and regulates the vascular tone and functions. However, which cellular signaling mechanisms are triggered by ROS in PAH is still unknown. Hence, here we wished to characterize the signaling mechanisms triggered by ROS. Methods and Results: By Western blots, we showed that increased intracellular ROS caused inhibition of the glycolytic pyruvate kinase M2 (PKM2) activity through promoting the phosphorylation of PKM2. Monocrotaline (MCT)-induced rats developed severe PAH and right ventricular hypertrophy, with a significant increase in the P-PKM2 and decrease in pyruvate kinase activity which could be attenuated with the treatments of PKM2 activators, FBP and l-serine. The antioxidant NAC, apocynin and MnTBAP had the similar protective effects in the development of PAH. In vitro assays confirmed that inhibition of PKM2 activity could modulate the flux of glycolytic intermediates in support of cell proliferation through the increased pentose phosphate pathway (PPP). Increased ROS and decreased PKM2 activity also promoted the Cav1.2 expression and intracellular calcium. Conclusion: Our data provide new evidence that PKM2 makes a critical regulatory contribution to the PAHs for the first time. Decreased pyruvate kinase M2 activity confers additional advantages to rat PASMCs by allowing them to sustain anti-oxidant responses and thereby support cell survival in PAH. It may become a novel treatment strategy in PAH by using of PKM2 activators.

A modular holistic approach to prosody modelling for Standard Yorùbá speech synthesis

This paper presents a novel prosody model in the context of computer text-to-speech synthesis applications for tone languages. We have demonstrated its applicability using the Standard Yorùbá (SY) language. Our approach is motivated by the theory that abstract and realised forms of various prosody dimensions should be modelled within a modular and unified framework [Coleman, J.S., 1994. Polysyllabic words in the YorkTalk synthesis system. In: Keating, P.A. (Ed.), Phonological Structure and Forms: Papers in Laboratory Phonology III, Cambridge University Press, Cambridge, pp. 293–324]. We have implemented this framework using the Relational Tree (R-Tree) technique. R-Tree is a sophisticated data structure for representing a multi-dimensional waveform in the form of a tree. The underlying assumption of this research is that it is possible to develop a practical prosody model by using appropriate computational tools and techniques which combine acoustic data with an encoding of the phonological and phonetic knowledge provided by experts. To implement the intonation dimension, fuzzy logic based rules were developed using speech data from native speakers of Yorùbá. The Fuzzy Decision Tree (FDT) and the Classification and Regression Tree (CART) techniques were tested in modelling the duration dimension. For practical reasons, we have selected the FDT for implementing the duration dimension of our prosody model. To establish the effectiveness of our prosody model, we have also developed a Stem-ML prosody model for SY. We have performed both quantitative and qualitative evaluations on our implemented prosody models. The results suggest that, although the R-Tree model does not predict the numerical speech prosody data as accurately as the Stem-ML model, it produces synthetic speech prosody with better intelligibility and naturalness. The R-Tree model is particularly suitable for speech prosody modelling for languages with limited language resources and expertise, e.g. African languages. Furthermore, the R-Tree model is easy to implement, interpret and analyse.

Pitch shifts on mistuned harmonics in the presence and absence of corresponding in-tune components

Mistuning a harmonic produces an exaggerated change in its pitch, a component-pitch shift. The origin of these pitch shifts was explored by manipulations intended to alter the grouping status of a mistuned target component in a periodic complex tone. In experiment 1, which used diotic presentation, reinstating the corresponding harmonic (in-tune counterpart) caused the pitch shifts on the mistuned target largely to disappear for components 3 and 4, although they remained for component 2. A computational model of component-pitch shifts, based on harmonic cancellation, was unable to explain the near-complete loss of pitch shifts when the counterpart was present; only small changes occurred. In experiment 2, the complex tone and mistuned component 4 were presented in the left ear and the in-tune counterpart was presented in the right. The in-tune counterpart again reduced component-pitch shifts, but they were restored when a captor complex into which the counterpart fitted as harmonic 3 was added in the right ear; presumably by providing an alternative grouping possibility for the counterpart. It is proposed that component-pitch shifts occur only if the mistuned component is selected to contribute to the complex-tone percept; these shifts are eliminated if it is displaced by a better candidate.

Quantum-dot mode-locked lasers with dual-mode optical injection

Quantum-dot mode-locked lasers are injection-locked by coherent two-tone master sources. Spectral tuning, significantly improved time-bandwidth product, and low jitter are demonstrated without deterioration of the pulse properties.

Mode-locked semiconductor lasers with optical injection

We perform characterization of the pulse shape and noise properties of quantum dot passively mode-locked lasers (PMLLs). We propose a novel method to determine the RF linewidth and timing jitter, applicable to high repetition rate PMLLs, through the dependence of modal linewidth on the mode number. Complex electric field measurements show asymmetric pulses with parabolic phase close to threshold, with the appearance of waveform instabilities at higher currents. We demonstrate that the waveform instabilities can be overcome through optical injection-locking to the continues wave (CW) master laser, leading to time-bandwidth product (TBP) improvement, spectral narrowing, and spectral tunability. We discuss the benefits of single- and dual-tone master sources and demonstrate that dual-tone optical injection can additionally improve the noise properties of the slave laser with RF linewidth reduction below instrument limits (1 kHz) and integrated timing jitter values below 300 fs. Dual-tone injection allowed slave laser repetition rate control over a 25 MHz range with reduction of all modal optical linewidths to the master source linewidth, demonstrating phase-locking of all slave modes and coherence improvement.

Psychophysiological responses to pain identify reproducible human clusters

Pain is a ubiquitous yet highly variable experience. The psychophysiological and genetic factors responsible for this variability remain unresolved. We hypothesised the existence of distinct human pain clusters (PCs) composed of distinct psychophysiological and genetic profiles coupled with differences in the perception and the brain processing of pain. We studied 120 healthy subjects in whom the baseline personality and anxiety traits and the serotonin transporter-linked polymorphic region (5-HTTLPR) genotype were measured. Real-time autonomic nervous system parameters and serum cortisol were measured at baseline and after standardised visceral and somatic pain stimuli. Brain processing reactions to visceral pain were studied in 29 subjects using functional magnetic resonance imaging (fMRI). The reproducibility of the psychophysiological responses to pain was assessed at 1 year. In group analysis, visceral and somatic pain caused an expected increase in sympathetic and cortisol responses and activated the pain matrix according to fMRI studies. However, using cluster analysis, we found 2 reproducible PCs: at baseline, PC1 had higher neuroticism/anxiety scores (P ≤ 0.01); greater sympathetic tone (P < 0.05); and higher cortisol levels (P ≤ 0.001). During pain, less stimulus was tolerated (P ≤ 0.01), and there was an increase in parasympathetic tone (P ≤ 0.05). The 5-HTTLPR short allele was over-represented (P ≤ 0.005). PC2 had the converse profile at baseline and during pain. Brain activity differed (P ≤ 0.001); greater activity occurred in the left frontal cortex in PC1, whereas PC2 showed greater activity in the right medial/frontal cortex and right anterior insula. In health, 2 distinct reproducible PCs exist in humans. In the future, PC characterization may help to identify subjects at risk for developing chronic pain and may reduce variability in brain imaging studies. © 2013 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved.

NADPH oxidase signaling and cardiac myocyte function

The NADPH oxidase family of enzymes has emerged as a major source of reactive oxygen species (ROS) that is important in diverse cellular functions including anti-microbial defence, inflammation and redox signaling. Of the five known NADPH oxidase isoforms, several are expressed in cardiovascular cells where they are involved in physiological and pathological processes such as the regulation of vascular tone, cell growth, migration, proliferation, hypertrophy, apoptosis and matrix deposition. This article reviews current knowledge regarding the role of NADPH oxidases in cardiomyocyte function in health and disease. © 2009 Elsevier Inc. All rights reserved.

Observing repetitive finger movements modulates response times of auditorily cued finger movements

Our motor and perceptual representations of actions seem to be intimately linked and the human mirror neuron system (MNS) has been proposed as the mediator. In two experiments, we presented biological or non-biological movement stimuli that were either congruent or incongruent to a required response prompted by a tone. When the tone occurred with the onset of the last movement in a series, i.e., it was perceived during the movement presentation, congruent biological stimuli resulted in faster reaction times than congruent non-biological stimuli. The opposite was observed for incongruent stimuli. When the tone was presented after visual movement stimulation, however, no such interaction was present. This implies that biological movement stimuli only affect motor behaviour during visual processing but not thereafter. These data suggest that the MNS is an “online” system; longstanding repetitive visual stimulation (Experiment 1) has no benefit in comparison to only one or two repetitions (Experiment 2).

Mode-locked semiconductor lasers with optical injection

We perform characterization of the pulse shape and noise properties of quantum dot passively mode-locked lasers (PMLLs). We propose a novel method to determine the RF linewidth and timing jitter, applicable to high repetition rate PMLLs, through the dependence of modal linewidth on the mode number. Complex electric field measurements show asymmetric pulses with parabolic phase close to threshold, with the appearance of waveform instabilities at higher currents. We demonstrate that the waveform instabilities can be overcome through optical injection-locking to the continues wave (CW) master laser, leading to time-bandwidth product (TBP) improvement, spectral narrowing, and spectral tunability. We discuss the benefits of single- and dual-tone master sources and demonstrate that dual-tone optical injection can additionally improve the noise properties of the slave laser with RF linewidth reduction below instrument limits (1 kHz) and integrated timing jitter values below 300 fs. Dual-tone injection allowed slave laser repetition rate control over a 25 MHz range with reduction of all modal optical linewidths to the master source linewidth, demonstrating phase-locking of all slave modes and coherence improvement.

Third-order intermodulation products generated on transmission through nonlinear radio-on-fibre link

Two-tone intermodulation tests were simulated for an amplitude modulated radio-on-fibre link including fibre dispersion, nonlinearity and loss. The third-order intercept results are presented for varying fibre lengths and optical transmission powers.

Quantum-dot mode-locked lasers with dual-mode optical injection

Quantum-dot mode-locked lasers are injection-locked by coherent two-tone master sources. Spectral tuning, significantly improved time-bandwidth product, and low jitter are demonstrated without deterioration of the pulse properties.