Maximum Phonation Time as a Predictor of Lactate Threshold during Intermittent Incremental Endurance Test.

The aim of the present study was to examine whether the exercise intensity corresponding to the lactate threshold may be predicted by the Maximum Phonation Time task (MPT). Ten Greek amateur football players (age: 18.4 ± 1.0 years), performed a graded cycling exercise test to exhaustion in order to determine lactate threshold. A number of physiological variables were measured including perceived exertion, cardiopulmonary values and blood lactate. The MPT variable was correlated with all of the physiological variables. Also, a binary logistic regression analysis was used to investigate whether MPT could predict lactate threshold. The ROC analysis showed specificity to be 0.90 and sensitivity to be 0.70 (optimal screening cutoff point for MPT 9.5 seconds). The results showed an odds ratio of 1.45 indicating a 45% increase in the probability of passing the threshold for every second there was a reduction in voice duration. MPT may be used as a simple, non-invasive, inexpensive method for monitoring exercise intensity during physical exercise. Further research is needed to measure its efficacy in bigger samples and in different sports.

Electrical, structural, and optical properties of sulfurized Sn-doped In2O 3 nanowires.

Sn-doped In2O3 nanowires have been grown on Si via the vapor-liquid-solid mechanism at 800 °C and then exposed to H2S between 300 to 600 °C. We observe the existence of cubic bixbyite In2O3 and hexagonal SnS2 after processing the Sn:In2O3 nanowires to H2S at 300 °C but also cubic bixbyite In2O3, which remains dominant, and the emergence of rhombohedral In2(SO4)3 at 400 °C. The resultant nanowires maintain their metallic-like conductivity, and exhibit photoluminescence at 3.4 eV corresponding to band edge emission from In2O3. In contrast, Sn:In2O3 nanowires grown on glass at 500 °C can be treated under H2S only below 200 °C which is important for the fabrication of Cu2S/Sn:In2O3 core-shell p-n junctions on low-cost transparent substrates such as glass suitable for quantum dot-sensitized solar cells.

Zinc oxide nanorod based photonic devices: recent progress in growth, light emitting diodes and lasers.

Zinc oxide (ZnO), with its excellent luminescent properties and the ease of growth of its nanostructures, holds promise for the development of photonic devices. The recent advances in growth of ZnO nanorods are discussed. Results from both low temperature and high temperature growth approaches are presented. The techniques which are presented include metal-organic chemical vapour deposition (MOCVD), vapour phase epitaxy (VPE), pulse laser deposition (PLD), vapour-liquid-solid (VLS), aqueous chemical growth (ACG) and finally the electrodeposition technique as an example of a selective growth approach. Results from structural as well as optical properties of a variety of ZnO nanorods are shown and analysed using different techniques, including high resolution transmission electron microscopy (HR-TEM), scanning electron microscopy (SEM), photoluminescence (PL) and cathodoluminescence (CL), for both room temperature and for low temperature performance. These results indicate that the grown ZnO nanorods possess reproducible and interesting optical properties. Results on obtaining p-type doping in ZnO micro- and nanorods are also demonstrated using PLD. Three independent indications were found for p-type conducting, phosphorus-doped ZnO nanorods: first, acceptor-related CL peaks, second, opposite transfer characteristics of back-gate field effect transistors using undoped and phosphorus doped wire channels, and finally, rectifying I-V characteristics of ZnO:P nanowire/ZnO:Ga p-n junctions. Then light emitting diodes (LEDs) based on n-ZnO nanorods combined with different technologies (hybrid technologies) are suggested and the recent electrical, as well as electro-optical, characteristics of these LEDs are shown and discussed. The hybrid LEDs reviewed and discussed here are mainly presented for two groups: those based on n-ZnO nanorods and p-type crystalline substrates, and those based on n-ZnO nanorods and p-type amorphous substrates. Promising electroluminescence characteristics aimed at the development of white LEDs are demonstrated. Although some of the presented LEDs show visible emission for applied biases in excess of 10 V, optimized structures are expected to provide the same emission at much lower voltage. Finally, lasing from ZnO nanorods is briefly reviewed. An example of a recent whispering gallery mode (WGM) lasing from ZnO is demonstrated as a way to enhance the stimulated emission from small size structures.

Homogeneous core/shell ZnO/ZnMgO quantum well heterostructures on vertical ZnO nanowires.

Low-area density ZnO nanowire arrays, growing perpendicularly to the substrate, are synthesized with high-pressure pulsed laser deposition. The introduction of a ZnO buffer layer enables us to fabricate individual nanowires several micrometres apart (area density<0.1 nanowire microm(-2)), suppressing any shadowing effect by neighbouring nanowires during subsequent growth. These low density ZnO nanowires, whose c-axis is perpendicular to the substrate surface, are then used as templates to grow ZnO/ZnMgO core-shell nanowire heterostructures with conventional low-pressure pulsed laser deposition. Cathodoluminescence spectroscopy as well as transmission electron microscopy show that a sharp interface forms between the ZnO core and the ZnMgO shell. Based on these findings, we have grown a series of radial ZnO/ZnMgO quantum wells with different thicknesses that exhibit quantum confinement effects, with thicker quantum wells emitting at lower energies. Spatially resolved cathodoluminescence confirms the homogeneity of the quantum well structure along the full nanowire length of about 3 microm.

Engineering of FePt nanoparticles by e-beam co-evaporation.

Fe(50)Pt(50) nanoparticles were deposited on thermally oxidized Si substrates by electron-beam co-evaporation of Fe and Pt, at substrate temperatures T(s) between 300 and 700 degrees C. The co-deposition led to the formation of drop-like, coalesced nanoparticles, chain-like structures or continuous films, the morphology being dependent on T(s) or the nominal thickness of the layer, f. The nanoparticles have a mean diameter D(p) between 3 and 45 nm, which increases with increasing f. The degree of crystallization in the ordered face centred tetragonal (fct) phase of the samples depends strongly on the growth conditions and increases with increasing T(s) and f. Nanoparticles with a higher proportion of the fct phase exhibit higher coercivity, with a maximum value of approximately 10.3 kOe (for the specimens prepared at 600 degrees C with f = 8.5 nm). Conversely, samples with a high proportion of the cubic phase are either superparamagnetic or ferromagnetically soft. The thermal annealing performed on selected samples resulted in structural transformation as well as magnetic hardening that depended on f and D(p).

Spatial fluctuations of optical emission from single ZnO/MgZnO nanowire quantum wells.

MgZnO/ZnO quantum wells on top of ZnO nanowires were grown by pulsed laser deposition. Ensembles of spatially fluctuating and narrow cathodoluminescence peaks with single widths down to 1 meV were found at the spectral position of the quantum well emission at 4 K. In addition, the number of these narrow QW peaks increases with increasing excitation power in micro-photoluminescence, thus pointing to quantum-dot-like emission centers. Indeed, laterally strained areas of about 5 nm diameter were identified at the quantum well positions on top of the nanowires by high-resolution transmission electron microscopy.

FePt and CoPt nanoparticles co-deposited on silicon dioxide-a comparative study.

We compare CoPt and FePt nanoparticles grown under identical conditions on oxidized Si substrates by electron beam co-evaporation. Growth was performed under high vacuum conditions at substrate temperatures of 1023 K and was immediately followed by an annealing step. This process forms CoPt and FePt nanoparticles with mean diameters between ∼17 and ∼22 nm. In particular, the annealing step results in grain size enlargement for all samples and in a progressive magnetic hardening of the nanoparticles which reach maximum perpendicular coercivities of ∼6.6 kOe (for the CoPt) and ∼10.2 kOe (for the FePt nanoparticles). We show that, during this annealing step, a progressive transition towards the hard magnetic L1(0) ordered phase takes place in both materials. In contrast to FePt, CoPt nanoparticles must be annealed in order to crystallize in this phase.

Structural study of very thin anodic alumina films on silicon by anodization in citric acid aqueous solution.

The formation of thin alumina films on a silicon substrate by anodization in a mild acid, specifically in 1% wt citric acid aqueous solution, is investigated by transmission electron microscopy (TEM). We present a comparative study between two cases of starting material: pure aluminum and an alloy of aluminum with 1% silicon. In both cases the thickness of the Al layer was less than 50 nm. It was observed that under exactly the same conditions, in the first case the anodization was stopping before anodizing the whole film and a remaining non-anodized Al layer was always present, while in the second case, the Al layer was fully anodized, resulting in an alumina matrix with a very high density of silicon nanocrystals of uniform sizes embedded in it. In both cases the alumina film was compact and amorphous.

Nonneurologic hand pain versus carpal tunnel syndrome: do psychological measures differentiate?

OBJECTIVE: To determine whether psychological measures would differentiate a group of patients with physician-diagnosed nonneurologic hand pain from patients with carpal tunnel syndrome (CTS). Many patients, who also displayed symptoms of psychological distress, were referred to an electrodiagnostic clinic with a diagnosis of possible CTS; they subsequently had normal nerve conduction studies. DESIGN: Sixty patients with hand pain were referred to either of two university clinics for electrophysiologic testing, were assigned to either the CTS or nonneurologic group, and were compared on a series of psychometric tests. RESULTS: The Beck Depression Inventory and McGill Pain Questionnaire showed that the physician-assigned nonneurologic patients have a greater degree of depression, use more affective adjectives, and choose more words on the McGill Pain Questionnaire than the physician-assigned CTS group. The nonneurologic group also scored higher on indices of self-reported disability on the Pain Disability Inventory in five of seven categories. Although the CTS group perceived more control over their pain, no differences were observed in the types of coping strategies used on the Coping Strategy Questionnaire. Finally, the nonneurologic group had more Workers' Compensation Board claims. CONCLUSION: Evidence of important psychological issues in some patients with hand pain suggests a need for greater awareness among treating physicians.

Re-examining the temporal locus of knowledge of results (KR): a self-paced approach to learning.

Using a self-paced procedure, the effects of unconfounded temporal locus of KR in the acquisition of a simple linear-positioning task was examined. Changes in the chronological profile of KR delivery were evaluated when participants manipulated the time course of the experiment at their own discretion. 29 participants (18 to 32 years) practiced finding an 8-in. line with no fixed starting and ending points. One-way repeated-measures analyses of variance, simple regression analyses across blocks of practice (30), and Pearson product-moment correlations between the KR-time intervals and the performance scores indicated that (a) under self-paced procedures both the KR-delay and post-KR interval decreased congruently with performance error scores, while the temporal component of the task (movement time) and the ratio between the KR-delay and the post-KR interval remained unchanged, (b) any effect on intertrial interval and interstimulus interval in motor skill acquisition should be examined in terms of the KR-delay and post-KR interval, and (c) the relationship between the performance scores and post-KR interval may be used to indicate the point at which KR is no longer required.

KR-withdrawal and self-paced motor performance.

The purpose of this study was to examine the effects of KR-withdrawal on performance and the chronological profile of KR-delivery following the self-paced procedure and the blank trial technique. 120 participants were randomly separated into 12 groups and practiced finding an 8-in. line with no fixed starting and ending points. Appropriate 12 x 3 (groups by blocks of trials) analyses of variance and a prior contrasts were conducted to analyze all dependent variables (absolute error, variable error, movement time, KR-delay, post-KR interval, and KR-delay by post-KR interval ratio). The results indicated that (a) accuracy decreased significantly when KR was withdrawn early in practice, while the effects of KR-withdrawal later in practice affected accuracy differently. (b) Early in practice, participants performed at the same level of consistency even when KR was withdrawn; however, later in practice, the participants were less variable. (c) Movement time, KR-delay, and post-KR-interval were affected differently during early and later stages of practice. (d) Moderate to high correlations between absolute error and post-KR intervals may indicate the development of mechanisms for error detection.

More practice does not necessarily enhance transfer of learning: evidence and interpretations.

The purpose of this study was to investigate what was learned and transferred of a criterion task using a transfer task and a self-paced procedure. Based on the results of two previous studies, five durations of practice were specifically selected to examine what can be transferred to a new task after different amounts of practice (40, 75, 100, 125, and 150 acquisition trials) on a criterion task. The criterion task required subjects to practice finding an 8-in. line with no fixed starting and ending points from left to right. The transfer task was different from the criterion task in two dimensions, distance (10-in. line) and direction (right to left). 50 volunteers were randomly assigned into 5 groups. Appropriate 5 x 2 (groups by blocks of practice) analyses of variance and a priori contrasts were conducted for all dependent variables (absolute error, variable error, movement time, KR-delay, post-KR interval, intertrial interval, interstimulus interval, and KR-delay by post-KR interval ratio) to examine the effects of terminal acquisition of the criterion task on the initial performance of the transfer task. Analysis indicated that, during practice, participants developed a functional interaction between performance characteristics and chronological profile of KR-delivery of the criterion task that was transferable to the transfer task. Also, practice beyond a certain point was detrimental to the ability to transfer what was learned.

Elevation of core temperature and mental functioning.

The purpose of this study was to investigate whether raised core temperature due to gradually increased amounts of exercise affects concentration and speed of information processing, 20 paid men, separated into groups of high (> 56 ml/kg/min.) and low fitness (< 46 ml/kg/min.) according to their maximal oxygen uptake (VO2max), participated in two experimental conditions (exercise and control). Concentration was measured by the Random Number Generation test of attentional deployment given every 10 min. of cycling at workloads calculated as 40, 50, 60, 70, and 80% of individual VO2max values and 10 min. after exercise cessation (exhaustion). Speed of information processing was estimated by an eight-choice reaction time/movement time task given before and after exercise and 15 min. after exercise cessation. Core temperature was recorded at the same time individuals were administered the psychological tests. Analyses indicated that core temperatures increased significantly as a function of exercise intensity for high and low fitness groups. Correlations among the psychophysiological factors indicated that increases in core temperature were not associated with mental functioning. However, at certain core temperatures, core temperature and average choice reaction time/movement time were associated with participants' fitness.

Perceived exertion during physical exercise among individuals high and low in fitness.

This study was conducted to investigate the influence of fitness level and gradually increased amounts of exercise on individuals' ratings of perceived exertion (RPE). 20 men served as paid subjects. They were divided into groups of high ( > 56 ml/kg/min.) and low fitness ( < 46 ml/kg/min.) according to their maximal oxygen uptake (VO2 (max)). Participants were required to pedal on a cycle ergometer at a progressively increased workload (every 10 min.) corresponding to 40, 50, 60, 70, and 80% of individual VO2 (max) values. Heart rates, RPE, and core temperatures were recorded every 5th minute after the initiation of exercising at a specific workload. Analysis indicated that, when controlling for VO2 (max) values, elevations of heart rate and core temperature were not affected by fitness. However, highly fit individuals perceived themselves under less exertion than did the group low in fitness. Correlations showed that, taking into consideration fitness, there is a stronger relationship between RPE and heart rate and RPE and core temperature for the highly fit individuals than for the less fit.

Information processing and concentration as a function of fitness level and exercise-induced activation to exhaustion.

To examine the effects of increasing amounts of exercise on attention and speed of information processing 20 paid male subjects were separated into groups of high and low fitness according to their VO2max values. The experiment involved an attentional task (Random Number Generation) that was given after every 10 min. of cycling at work-load resistances calculated as 40%, 50%, 60%, 70%, and 80% of individual VO2max values. An eight-choice reaction time-movement time task was given before and after exercise as well as after a 15-min. recovery period. Individuals were tested within 10 min. after exercise cessation (exhaustion) for concentration and within 15 min. for choice reaction time and movement time to assess whether fitness differentially interacted with these variables. Split-plot factorial analyses of variance suggested that the CNS appeared capable of maintaining performance after 50 min. of exhaustive exercise compared to values obtained at the preexercise condition. A 15-min. recovery period significantly impaired MT but relatively highly fit individuals did not appear to perform the choice RT and concentration tasks better than individuals low in fitness.

Temporal locus of knowledge of results: a meta-analytic review.

Meta-analysis was performed to evaluate the temporal locus of knowledge of results. An extensive literature review was conducted, yielding 17 published articles suitable for the meta-analyses. These studies were then separated into 2 general categories of acquisition and retention. These categories were subdivided further into KR delay interval, KR delay and motor interpolated activities, KR delay and verbal interpolated activities, post-KR interval, post-KR interval and motor interpolated activities, and post-KR interval and verbal interpolated activities. 6 of the 12 categories gave enough data for the meta-analyses. The categories which showed significant results were KR-delay, post-KR interval, and post-KR interval and verbal interpolated activities in acquisition. Although significant, effect sizes were comparatively small. The discussion of findings focused on effects of the temporal locus of KR and interpolated activities on performance and learning.

Monopolar needle evaluation of paraspinal musculature in the cervical, thoracic, and lumbar regions and the effects of aging.

Motor unit characteristics (phases, turns, amplitude, duration, and area) were measured using a monopolar needle and narrowed bandpass (500 Hz to 10 kHz) in cervical, thoracic, and lumbar paraspinal muscles in 66 subjects (36 women and 30 men) aged 22-81 years (mean age 45.7 years). Cervical motor units were of lower amplitude and area than thoracic and lumbar motor units (P = 0.0001), respectively. The durations of lumbar motor units were longer and larger than cervical and thoracic motor units (P = 0.0004). Analysis of covariance of the measured characteristics against age showed no significance in the cervical and thoracic regions. In lumbar paraspinal motor units, phases and turns increased significantly with age (P = 0.044 and P = 0.016, respectively). The increase was < 1.0 phase over 30 years. Motor unit amplitude increased with aging (P = 0.055) showing an increase of 360 microV over a 30-year time period. It is appropriate to assess the number of phases and turns, as well as the duration of the motor units in the cervical and thoracic (but not lumbar) spines in addition to seeking evidence of spontaneous, single fiber discharges.

Cerebrospinal fluid cell count following spinal cord injury.

Cerebrospinal fluid (CSF) changes after spinal cord injury (SCI) were evaulated by retrospective analysis of all patients admitted to the Acute Spinal Cord Injury Unit (ASCIU) at University Hospital, Shaughnessy Site in Vancouver, British Columbia. A total of 1,917 admissions occurred during the 10-year study period with 1,151 due to acute trauma. The charts of all patients with SCI due to trauma were reviewed to identify patients in whom a CSF puncture was performed for any reason. Traumatic SCI is associated with elevations in the corrected white blood cell count (cWBC) that we believe reflect an inflammatory response to injury. The elevation in cWBC is greatest in the first week after injury. Elevations in cWBC more than 1 week after injury do occur but are uncommon. The white cell differential count consists primarily of lymphocytes and polymorphonucleocytes. Three weeks after injury cell counts should be normal. Protein levels are elevated after trauma and should not be used to assess the presence of infection. LP should be part of the septic workup of SCI patients just as it would be for any other population if meningitis is a consideration.