Anodic behaviour of arsenopyrite and cathodic reduction of ferrate(VI) and oxygen in alkaline solutions

This paper presents the results of an electrochemical study of the anodic characteristics of arsenopyrite in strongly alkaline solutions and of the cathodic reduction of ferrate( VI) and of dissolved oxygen at an arsenopyrite surface at potentials which are relevant to the oxidation reactions. Cyclic voltammetry at both arsenopyrite disc and arsenopyrite disc/platinum ring electrodes has shown that arsenic(III) is the main product of the anodic process at potentials in the region of the rest potential during oxidation by either ferrate( VI) or oxygen. Evidence for partial passivation of both the anodic and cathodic reactions has been obtained from potentiostatic current - time transients. The initial stage of oxidation by ferrate( VI) has been shown to be mass-transport controlled and this is also true of the oxidation by oxygen in dilute solutions of sodium hydroxide.

Why does dissimilarity matter? Exploring self-categorization, self-enhancement, and uncertainty reduction

Although relational demographers have based their arguments on self-categorization theory, they have paid little attention to the underlying processes associated with this theory. The authors examined whether demographic dissimilarity affects individuals' identification with groups by affecting the group's prototype valence and clarity and the individual's perceptions of self-prototypicality. The data showed that the proportion of women and non-Australians in 34 work groups negatively influenced prototype valence, prototype clarity, and self-prototypicality for all members of the group. These results provide support for the continued use of self-categorization theory by relational demographers.

Suitability of acoustic perturbation measures in analysing periodic and nearly periodic voice signals

In recent years, acoustic perturbation measurement has gained clinical and research popularity due to the ease of availability of commercial acoustic analysing software packages in the market. However, because the measurement itself depends critically on the accuracy of frequency tracking from the voice signal, researchers argue that perturbation measures are not suitable for analysing dysphonic voice samples, which are aperiodic in nature. This study compares the fundamental frequency, relative amplitude perturbation, shimmer percent and noise-to-harmonic ratio between a group of dysphonic and non-dysphonic subjects. One hundred and twelve dysphonic subjects ( 93 females and 19 males) and 41 non-dysphonic subjects ( 35 females and 6 males) participated in the study. All the 153 voice samples were categorized into type I ( periodic or nearly periodic), type II ( signals with subharmonic frequencies that approach the fundamental frequency) and type III ( aperiodic) signals. Only the type I ( periodic and nearly periodic) voice signals were acoustically analysed for perturbation measures. Results revealed that the dysphonic female group presented significantly lower fundamental frequency, significantly higher relative amplitude perturbation and shimmer percent values than the non-dysphonic female group. However, none of these three perturbation measures were able to differentiate between male dysphonic and male non-dysphonic subjects. The noise-to-harmonic ratio failed to differentiate between the dysphonic and non-dysphonic voices for both gender groups. These results question the sensitivity of acoustic perturbation measures in detecting dysphonia and suggest that contemporary acoustic perturbation measures are not suitable for analysing dysphonic voice signals, which are even nearly periodic. Copyright (C) 2005 S. Karger AG, Basel.

Simplest tasks have greatest dual task interference with balance in brain injured adults

Attention difficulties and poor balance are both common sequel following a brain injury. This study aimed to determine whether brain injured adults had greater difficulty than controls in performing a basic balance task while concurrently completing several different cognitive tasks varying in visuo-spatial attentional load and complexity. Twenty brain injured adults and 20 age-, sex- and education level-matched controls performed a balance-only task (step stance held for 30s), five cognitive-only tasks (simple and complex non-spatial, visuo-spatial, and a control articulation task), and both together (dual tasks). Brain injured adults showed a greater centre of pressure (COP) excursion and velocity in all conditions than controls. Brain injured adults also demonstrated greater interference with balance when concurrently performing two cognitive tasks than control subjects. These were the control articulation and the simple non-spatial task. It is likely that distractibility during these simple tasks contributed to an increase in COP motion and interference with postural stability in stance. Performing visuo-spatial tasks concurrently with the balance task did not result in any change in COP motion. Dual task interference in this group is thus unlikely to be due to structural interference. Similarly, as the more complex tasks did not uniformly result in increased interference, a reduction in attentional capacity in the brain injured population is unlikely to be the primary cause of dual task interference in this group. (C) 2004 Elsevier B.V. All rights reserved.

Pain differs from non-painful attention-demanding or stressful tasks in its effect on postural control patterns of trunk muscles

Pain changes postural activation of the trunk muscles. The cause of these changes is not known but one possibility relates to the information processing requirements and the stressful nature of pain. This study investigated this possibility by evaluating electromyographic activity (EMG) of the deep and superficial trunk muscles associated with voluntary rapid arm movement. Data were collected from control trials, trials during low back pain (LBP) elicited by injection of hypertonic saline into the back muscles, trials during a non-painful attention-demanding task, and during the same task that was also stressful. Pain did not change the reaction time (RT) of the movement, had variable effects on RT of the superficial trunk muscles, but consistently increased RT of the deepest abdominal muscle. The effect of the attention-demanding task was opposite: increased RT of the movement and the superficial trunk muscles but no effect on RT of the deep trunk muscles. Thus, activation of the deep trunk muscles occurred earlier relative to the movement. When the attention-demanding task was made stressful, the RT of the movement and superficial trunk muscles was unchanged but the RT of the deep trunk muscles was increased. Thus, the temporal relationship between deep trunk muscle activation and arm movement was restored. This means that although postural activation of the deep trunk muscles is not affected when central nervous system resources are limited, it is delayed when the individual is also under stress. However, a non-painful attention-demanding task does not replicate the effect of pain on postural control of the trunk muscles even when the task is stressful.

Visual-auditory integration during speech imitation in autism

Children with autistic spectrum disorder (ASD) may have poor audio-visual integration, possibly reflecting dysfunctional 'mirror neuron' systems which have been hypothesised to be at the core of the condition. In the present study, a computer program, utilizing speech synthesizer software and a 'virtual' head (Baldi), delivered speech stimuli for identification in auditory, visual or bimodal conditions. Children with ASD were poorer than controls at recognizing stimuli in the unimodal conditions, but once performance on this measure was controlled for, no group difference was found in the bimodal condition. A group of participants with ASD were also trained to develop their speech-reading ability. Training improved visual accuracy and this also improved the children's ability to utilize visual information in their processing of speech. Overall results were compared to predictions from mathematical models based on integration and non-integration, and were most consistent with the integration model. We conclude that, whilst they are less accurate in recognizing stimuli in the unimodal condition, children with ASD show normal integration of visual and auditory speech stimuli. Given that training in recognition of visual speech was effective, children with ASD may benefit from multi-modal approaches in imitative therapy and language training. (C) 2004 Elsevier Ltd. All rights reserved.

Effects of neurosurgical management of Parkinson's disease on speech characteristics and oromotor function

The present study examined the effects of neurosurgical management of Parkinson's disease (PD), including the procedures of pallidotomy, thalamotomy, and deep-brain stimulation (DBS) on perceptual speech characteristics, speech,, intelligibility and oromotor function in a group of 22 participants with PD. The surgical participant group was compared with a group of 25 non-neurologically impaired individuals matched for age and sex. In addition, the study investigated 16 participants with PD who did not undergo neurosurgical management to control for disease progression. Results revealed that neurosurgical intervention did not significantly change the surgical participants' perceptual speech dimensions or oromotor function despite significant postoperative improvements in ratings of general motor function and disease severity. Reasons why neurosurgical intervention resulted in dissimilar outcomes with respect to participants' perceptual speech dimensions and general motor function are proposed.

Summation of semantic priming and complex sentence comprehension in Parkinson's disease

Research has suggested that the integrity of semantic processing may be compromised in Parkinson's disease (PD), which may account for difficulties in complex sentence comprehension. In order to investigate the time course and integrity of semantic activation in PD, 20 patients with PD and 23 healthy controls performed a lexical decision task based on the multi-priming paradigm. Semantic priming effects were measured across stimulus onset asynchronies of 250 ms, 600 ms, and 1200 ms. Further, PD participants performed an auditory comprehension task. The results revealed significantly different patterns of semantic priming for the PD group at the 250-ms and 1200-ms SOAs. In addition, a delayed time course of semantic activation was evident for PD patients with poor comprehension of complex sentences. These results provide further support to suggest that both automatic and controlled aspects of semantic activation may be compromised in PD. Furthermore, the results also suggest that some sentence comprehension deficits in PD may be related to a reduction in information processing speed.

Differential motor speech outcomes in children treated for mid-line cerebellar tumour

Primary objective: To investigate the nature of the motor speech impairments and dysarthria that can arise subsequent to treatment for childhood mid-line cerebellar tumours (CMCT). Research design: The motor speech ability of six cases of children with CMCT was analysed using perceptual and physiological measures and compared with that of a group of non-neurologically impaired children matched for age and sex. Main outcome and results: Three of the children with CMCT were perceived to exhibit dysarthric speech, while the remaining three were judged to have normal speech. The speech disorder in three of the children with CMCT was marked by deviances in prosody, articulation and phonation. The underlying pathophysiology was linked to cerebellar damage and expressed as difficulty in co-ordinating the motor speech musculature as required for speech production. These deficits were not identified in the three non-dysarthric children with CMCT. Conclusion: Differential motor speech outcomes occur for children treated for CMCT and these are discussed within the realm of possible mechanisms responsible for these differences. The need for further investigation of the risk factors for development of motor speech impairment in children treated for CMCT is also highlighted.

First clinical experience with a new non-indwelling voice prosthesis (Provox (R) NID (TM)) for voice rehabilitation after total laryngectomy

Conclusion. The new Provox(R) NID (TM) non- indwelling voice prosthesis investigated in this study provides a good option for laryngectomized patients using non- indwelling voice prostheses and can potentially improve safety and increase patients' satisfaction with their voice and speech. Objective. To investigate the feasibility of and patient satisfaction with the Provox NID non- indwelling voice prosthesis. Material and methods. Pre- and post- study questionnaires were used to evaluate the patients' former voice prosthesis and the Provox NID voice prosthesis. In addition, measurements of pull- out force, maximum phonation time and loudness were made for both voice prostheses. In vitro measurements of airflow characteristics were also made. Following a 6- week trial, all patients provided feedback on the new voice prosthesis and the results were used to further improve the Provox NID. This final version of the new voice prosthesis was subsequently trialled and evaluated by 10 patients 6 months later. Results. Overall results showed that patient satisfaction with the Provox NID non- indwelling voice prosthesis was favourable. The pull- out force for the new prosthesis was significantly higher than that for the formerly used prosthesis and its aerodynamic characteristics were better.

Articulatory function following traumatic brain injury in childhood: A perceptual and instrumental analysis

Primary objective: To investigate the articulatory function of a group of children with traumatic brain injury (TBI), using both perceptual and instrumental techniques. Research design: The performance of 24 children with TBI was assessed on a battery of perceptual (Frenchay Dysarthria Assessment, Assessment of Intelligibility of Dysarthric Speech and speech sample analysis) and instrumental ( lip and tongue pressure transduction systems) assessments and compared with that of 24 non-neurologically impaired children matched for age and sex. Main outcomes: Perceptual assessment identified consonant and vowel imprecision, increased length of phonemes and overall reduction in speech intelligibility, while instrumental assessment revealed significant impairment in lip and tongue function in the TBI group, with rate and pressure in repetitive lip and tongue tasks particularly impaired. Significant negative correlations were identified between the degree of deviance of perceptual articulatory features and decreased function on many non-speech measures of lip function, as well as maximum tongue pressure and fine force tongue control at 20% of maximum tongue pressure. Additionally, sub-clinical articulatory deficits were identified in the children with TBI who were non-dysarthric. Conclusion: The results of the instrumental assessment of lip and tongue function support the finding of substantial articulatory dysfunction in this group of children following TBI. Hence, remediation of articulatory function should be a therapeutic priority in these children.

Measuring the ability of school children with a history of otitis media to understand everyday speech

The present study compared the ability of school-aged children with and without a history of otitis media (OM) to understand everyday speech in noise using the University of Queensland Understanding of Everyday Speech Test (UQUEST). Participants were 484 children (246 boys, 238 girls) attending Grade 3 (272, mean age = 8.25 yr., SD = 0.43) and Grade 4 (212, mean age = 9.28 yr., SD = 0.41) at 19 primary schools in Brisbane metropolitan and Sunshine Coast schools. Children selected for inclusion were native speakers of English with normal hearing on the day of testing and had no reported physical or behavioral impairments. The children were divided into three groups according to the number of episodes of OM since birth. The results showed no significant differences in speech scores across the participant groups. However, a significant difference in mean speech scores was found across the grades and the noise conditions. Although children with a history of OM performed equally well at a group level when compared to the controls, they exhibited a large range of abilities in speech comprehension within the same group.