Validation of the AX3 triaxial accelerometer in older functionally impaired people

Background: Studying physical activity (PA) trends in older populations and potential interventions for increasing PA is important, as PA is a factor in many age-related health outcomes such as chronic disease, premature mortality, physical function, and injuries from falls[1]. Objective measures of PA provide valuable information regarding the functional impact that ageing and chronic disease states may have on a patient’s life. Aims: The purpose of this study was to test the validity of the AX3 PA monitor in an older population, to investigate if the AX3 is a valid measure of distinct types or levels of activity in older people with a spectrum of mobility. Methods: Validity of the AX3 PA monitor was tested using the RT3 as a means of cross validating the AX3. Study participants wore both the AX3 and the RT3 accelerometers, positioned on their non-dominant side, while completing a series of standardised everyday activities. Results: Although overall correlation was high (r>0.8) between the RT3 and lower-limb mounted AX3 counts, the correlation between the two devices was much stronger for walking activity than for any of the non-walking activities. Discussion: Activity counts at all lower limb positions for the AX3 and RT3 were highly correlated. Correlation between wrist-mounted AX3 counts and lower limb AX3 counts was only moderate, and worsened when walking aids were in use. Conclusions: The results of this study indicate that the AX3 monitor is a valid tool, which might be used to objectively measure walking activity in older, functionally impaired adults; a welcome finding for this under-researched area

An analysis of photoemission and inverse photoemission spectra of Si(111) and sulphur-passivated InP(001) surfaces

Photoemission (PES) and inverse-photoemission spectra (IPES) for the sulphur-passivated InP(001) surface are compared with theoretical predictions based on density-functional calculations. As a test case for our methods, we also present a corresponding study of the better known Si(111) surface. The reported spectra for InP(001)-S agree well with the calculated ones if the surface is assumed to consist of a mixture of two phases, namely, the fully S-covered $(2\times2)$-reconstructed structure, which contains four S atoms in the surface unit-cell, and a $(2\times2)$ structure containing two S and two P atoms per unit cell. The latter has recently been identified in total-energy calculations as well as in core-level spectra of S-passivated Si(111)-$(2\times1)$ is in excellent agreement with the calculations. The comparison of the experimental-PES with our calculations provides additional considerations regarding the nature of the sample surface. It is also found that the commonly-used density-of-states approximation to the photo- and inverse- photoemission spectra is not valid for these systems.Comment: Submitted to Phys. Rev. B; 6 postscript formatted pages; 7 figures in gif format; postscript figures available upon reques

Investigating domain-specific cognitive impairment among patients with multiple sclerosis using touchscreen cognitive testing in routine clinical care

Cognitive dysfunction is present in up to 70% of patients with multiple sclerosis (MS) and has been reported at all stages and in all subtypes of the disease. These deficits have been reported across a variety of cognitive domains, but are generally under-recognized and incompletely evaluated in routine clinical practice. The aim of this study was to investigate the spectrum of cognitive impairment in patients with MS presenting to a specialist MS clinic using the Cambridge Neuropsychological Test Automated Battery (CANTAB), administered on a touchscreen platform. Ninety MS patients completed computerized CANTAB tasks assessing working memory, executive function, processing speed, attention, and episodic memory. Scores were adjusted for age, sex, and level of education and classified as normal or impaired based on comparison with a large normative data pool. We also investigated the impact of clinical and demographic variables which could potentially influence cognitive performance including patient educational level (a proxy for cognitive reserve), disease status (duration, course, and severity of MS), and depression. CANTAB testing detected cognitive impairment in 40 patients (44% of the sample). The most frequently impaired domain was executive function, present in 55% of cognitively impaired individuals. Disease duration and severity were significantly associated with performance across various cognitive domains. Patients with depressive symptoms were also more likely to exhibit impaired processing speed. Results from this study confirm that cognitive impairment is common and occurs across a range of domains among MS patients attending routine clinical visits. CANTAB tasks provide a sensitive and practical approach to cognitive testing in MS patients as part of a holistic patient assessment

Vertical cavity lasers for optical interconnects

Vertical-cavity surface-emitting lasers are generating much interest due to their geometric suitability for two-dimensional array fabrication and their potential for achieving ultra-low thresholds. Here we report on optically- and electrically-pumped microlaser devices. having transverse dimensions of a few microns and active material lengths of a few hundred A. The very small volumes are a key factor in achieving low thresholds. So far however surface recombination has prevented us from achieving thresholds much below 1 mA

Comparison of Zn_{1-x}Mn_xTe/ZnTe multiple-quantum wells and quantum dots by below-bandgap photomodulated reflectivity

Large-area high density patterns of quantum dots with a diameter of 200 nm have been prepared from a series of four Zn_{0.93}Mn_{0.07}Te/ZnTe multiple quantum well structures of different well width (4 nm, 6 nm, 8 nm and 10 nm) by electron beam lithography followed by Ar+ ion beam etching. Below-bandgap photomodulated reflectivity spectra of the quantum dot samples and the parent heterostructures were then recorded at 10 K and the spectra were fitted to extract the linewidths and the energy positions of the excitonic transitions in each sample. The fitted results are compared to calculations of the transition energies in which the different strain states in the samples are taken into account. We show that the main effect of the nanofabrication process is a change in the strain state of the quantum dot samples compared to the parent heterostructures. The quantum dot pillars turn out to be freestanding, whereas the heterostructures are in a good approximation strained to the ZnTe lattice constant. The lateral size of the dots is such that extra confinement effects are not expected or observed.Comment: 23 pages, LaTeX2e (amsmath, epsfig), 7 EPS figure

Validation of the Godin Leisure-Time Exercise Questionnaire Classification Coding System Using Accelerometry in Multiple Sclerosis

Objective: There have been recent efforts toward creating a health contribution score (HCS) from the Godin Leisure-Time Exercise Questionnaire (GLTEQ) that reflects public-health guidelines for levels of moderate-to-vigorous physical activity (MVPA). The HCS yields categories of insufficiently active (less substantial or low benefits), moderately active (some benefits), and active (substantial benefits). The present study examined the validity of the GLTEQ HCS and its categories as reflecting levels of MVPA in multiple sclerosis (MS). Method: The sample included 684 persons with MS. Participants wore an accelerometer on an elastic belt around the waist above the nondominant hip during the waking hours of the day over a 7-day period and completed the GLTEQ. Results: The data analyses supported a large correlation between the GLTEQ HCS and accelerometer-measured MVPA, r = .46, p \u3c .0001, but small correlations with accelerometer-measured light physical activity (LPA), r = .16, p \u3c .001 and sedentary time, r = −.13, p = .001. There further was a large difference in accelerometer-measured MVPA between categories of physical activity levels (i.e., insufficiently active vs. active) based on the GLTEQ HCS (d = 0.89), but small differences in LPA (d = 0.39) and sedentary time (d = −0.31). Those results were unchanged in additional data analyses accounting for LPA and sedentary behavior. Conclusions: The GLTEQ HCS and categories primarily reflect MVPA rather than LPA and sedentary behavior in persons with MS

Fitness and cognitive processing speed in persons with multiple sclerosis

Background: Cognitive impairment is prevalent, disabling, and poorly managed in persons with MS. To date, two studies have identified aerobic capacity as a correlate of cognition in MS, but there has yet to be an investigation of multiple domains of fitness as correlates of cognition in this population. Such an examination is important for identifying the appropriate modes of exercise training for possibly improving cognition. Objective: This study examined the relationships among aerobic capacity, muscle strength, and balance with cognitive function in persons with MS. Methods: 31 persons with MS and 31 controls matched by age, height, weight, and sex completed two neuropsychological measures of cognitive processing speed (PASAT and SDMT). Participants underwent an incremental exercise test to exhaustion on a cycle ergometer as a measure of aerobic capacity; three maximal isometric extensions and one maximal isometric flexion with each knee on an isokinetic dynamometer at three different joint angles as a measure of muscular strength; and stood on a force platform without shoes for 30 seconds with eyes open to measure postural sway. Results: Independent samples t-tests indicated that MS and control groups differed in PASAT score (t = −2.13, p = .04), SDMT score (t = −2.69, p = .01), aerobic capacity (t = −2.99, p < .01), and balance (t = 4.06, p < .01), but not in muscular strength. Cognitive processing speed was significantly associated with aerobic capacity (r = .43 and .44) and balance (r= −.52 and −.52), but not muscular strength in the overall and MS samples, respectively. Lastly, hierarchical regression analysis indicated that aerobic capacity (β = .27) and balance (β = −.40) accounted for differences in cognitive processing speed between MS and control groups. Conclusions: Aerobic capacity and balance, but not muscular strength, are associated with cognitive processing speed in persons with MS, suggesting that aerobic exercise and balance training are avenues for possibly improving cognitive impairment in this population

Effects of exercise training on multiple sclerosis biomarkers of central nervous system and disease status:a systematic review of intervention studies

BackgroundMultiple sclerosis (MS) is a demyelinating and neurodegenerative disease of the central nervous system (CNS) that can be tracked through biomarkers of disease status. We investigated the effects of exercise on MS biomarkers associated with CNS status including imaging, blood‐brain barrier (BBB) function and neurotrophic factors.MethodsWe conducted open‐dated searches of Scopus, Medline, EMBASE and the Cochrane Library. We included studies written in English describing interventions of exercise that measured one or more of the biomarkers associated with MS published up to October 2018.ResultsWe located a total of 3012 citations through searches in electronic databases. Of these, 16 studies were eligible for review; six studies focused on magnetic resonance imaging (MRI) markers, nine studies focused on neurotrophic factors, and three studies focused on BBB function markers. It is of note that two studies included both neurotrophic factor and BBB function markers and are therefore included across categories of biomarkers in this review. The existing evidence from MRI studies confirmed that exercise training can improve CNS integrity and function. There is evidence of a positive effect of exercise training on modulation of BBB permeability markers and brain‐derived neurotrophic factor.ConclusionsExercise successfully improves MRI outcomes and peripheral biomarkers (i.e., brain‐derived neurotrophic factor) in people with multiple sclerosis. This suggests that exercise can be recommended as an adjuvant therapy for MS treatment. This conclusion is tempered by some methodological limitations including small sample sizes and high drop‐out rates in the reviewed studies

The acute effects of varying intensities of treadmill walking exercise on cognition in persons with multiple sclerosis

Background: Exercise training represents a promising approach for managing cognitive impairment in persons with multiple sclerosis (MS). There is preliminary evidence that treadmill walking exercise might be the modality of exercise that exerts the greatest beneficial effects on executive control in persons with mild MS disability. However, the dose-dependent effects of varying intensities of treadmill walking exercise on this cognitive function are unknown. Such an investigation is critical for providing the final data for delineating the optimal exercise stimulus (or stimuli) for improving executive control in persons with MS. Objectives: The present study compared the acute effects of light, moderate, and vigorous intensity treadmill walking exercise on multiple aspects of executive control (i.e., interference control and response inhibition) relative to quiet rest in 24 persons with mild MS disability, using a within-subjects, repeated-measures experimental design. Methods: Participants completed four experimental conditions that consisted of 20 minutes of light intensity treadmill walking exercise, moderate intensity treadmill walking exercise, vigorous intensity treadmill walking exercise, and quiet rest in a randomized, counterbalanced order. Participants underwent a modified-flanker task and Go/No-Go task as measures of executive control immediately prior to and following each condition. Results: Repeated-measures ANOVAs indicated large, statistically significant pre-to-post reductions in the cost of interfering stimuli on reaction time, but not accuracy, on the modified-flanker task for light, moderate, and vigorous intensity exercise compared with quiet rest (F(3,69)=4.27,p=.01,ηp2=.16) that were similar in magnitude. There further were no overall effects of exercise intensities on percent accuracy from the Go/No-Go task (F(3,69)=0.33,p=.81,ηp2=.01), compared with quiet rest. Conclusions: The present results support light, moderate, and vigorous intensity treadmill walking as exercise stimuli that might particularly benefit speed-related aspects of executive control (i.e., interference control of reaction time). This represents the final step in delineating the optimal exercise stimuli for inclusion in a subsequent longitudinal exercise training intervention for improving this cognitive function in persons with mild MS disability

Physical Function Across the Lifespan in Adults with Multiple Sclerosis: An Application of the Short Physical Performance Battery

Background Multiple sclerosis (MS) typically has its onset in early and middle adulthood, but the population is steadily becoming more dominated by older adults. One of the primary consequences of both MS and aging involves declines of lower extremity physical function and mobility. This cross-sectional study compared physical function status based on Short Physical Performance Battery (SPPB) summary and component scores between persons with MS and healthy controls across 6 age groups. We further examined associations between SPPB summary scores and component scores as well as associations between summary scores and measures of physical and cognitive function for identifying the strongest correlates of SPPB summary scores. Methods The study involved secondary analysis of cross-sectional data from multiple studies. Ambulatory adults with MS who were relapse-free for the last 30 days were recruited, and controls were recruited based on similar criteria to adults with MS except without the diagnosis of MS or relapses. The sample of 345 persons with MS and 174 controls completed questionnaires regarding demographic and clinical information and underwent assessments of physical and cognitive function including the SPPB, 6-Minute Walk, Timed 25-Foot Walk, Symbol Digit Modalities Test, California Verbal Learning Test-Second Edition, and Brief Visuospatial Memory Test-Revised. Results The two-way ANOVA indicated a main effect of MS status (F(5,500)=34.74, pF(1,500)=3.88, pF(5,500)=1.20, p=.31, η2=0.012) on SPPB scores. The bivariate correlation analysis indicated that summary SPPB scores were associated with component SPPB scores in the overall samples of persons with MS (rs=0.71 to 0.83) and controls (rs=0.42 to 0.91) as well as within most age groups of MS (rs=0.63 to 0.91) and controls (rs=0.34 to 1.00). The associations between SPPB scores and physical function outcomes were larger in the sample of persons with MS (rs=–0.72 to 0.76) than controls (rs=–0.47 to 0.48). SPPB scores were further significantly associated with scores on cognitive outcomes in persons with MS (rs=0.31 to 0.43), whereas these associations were weaker in controls (rs=0.09 to 0.32). Overall, the associations between SPPB scores and physical function outcomes were stronger than the associations between SPPB scores and cognitive function outcomes. Conclusion Overall, MS status and aging have additive effects on physical function, and the summary SPPB score may be driven by a specific component within each age group. SPPB scores may be driven more by mobility rather than cognition, and are consistent with cognitive-motor coupling in MS. The novelty of this study provides evidence of worsening physical function based on the application of the SPPB and its scores across the lifespan in persons with MS and controls, and this has important implications particularly given the increasing prevalence of older adults with MS