Multiple sclerosis: Physiological, perceptive and neural responses to exercise intensity

The aim of this work was to investigate physiological, perceptive and neurological responses to exercise intensity in people with multiple sclerosis (PwMS). The thesis begins with reviews of Multiple Sclerosis (MS) and exercise followed by three main studies. The first study explores the within session and test-retest reliability of motor evoked potentials (MEPs) elicited by transcranial magnetic stimulation (TMS) from the resting tibialis anterior (TA) muscle of people with multiple sclerosis (PwMS). MEPs were recorded from 10 PwMS (2male, 8female) in 5 blocks of 5 trials using stimulators configured to fire a single pulse. MEP peak amplitudes (mV) and MEP areas (mV.mS) were measured at 2 durations MEPshort (30ms) and MEPlong (mean 50ms). The size of the first MEP (T1) from each block (mean 5.1) was significantly different to subsequent trials (T2 -T5) for MEPlong (mean 4.5 p 0.05). The testretest intraclass coefficients of correlation (ICC) and their 95% confidence intervals indicated high (>0.80) reliability for both MEParea and MEPpeak. The results showed that consistent, repeatable TMS measures were obtained from the resting TA of PwMS. The second study compared physiological and perceptive measures of PwMS to a group of healthy individuals while performing a symptom-limited graded exercise test (GXT), and through the post-exercise time-course to recovery. 54 PwMS (MSG, mean age 52.8years ± 9.0) and 17 healthy, age-matched controls (CG,mean age 48.9 years ± 5.7) performed a symptom-limited graded exercise test (GXT). Expired air (VO2), heart rate (HR), and differential ratings of perceived exertion (RPE breathing and RPE legs) were recorded during exercise, and HR and RPE (breathing and legs) during the recovery period. There were no significant differences in any baseline measure except RPEleg (MSG mean1.1±1.2; CG 0.2 ±0.4 p <0.05). During the GXT MS group means (±SD) failed to reach any criterion measure considered to represent peak performance. The control group mean exercise measures reached recognised criteria for peak testing on two measures; mean heart rate of within ± 10 beats of age predicted HRmax, mean RER value greater than 1.10. Significant differences existed between groups in all peak measures (mean MSG VO2 peak 20.1±6.4, mean CG VO2 peak 27.8 ±6.8; mean MSG HRpeak 140.1±24.8, mean CG HRpeak 167.7± 9.4; mean MSG RPE breathing 5.1±1.7, mean CG RPE breathing 6.8± 2.3; mean MS watts 97.4±35.2, mean CG watts 161.8 ± 43.4 p 0.05). There were no significant effects on the peak measures of variables when weighted by MS classification (RR-MS, SP-MS and PP- MS). There were differences between group recovery values for RPEleg at 10 mins (mean MSG 1.8 ±1.2, mean CG 1.0±1.1 p<0.05) and Temp°C at 3mins (mean MSG 36.5± 0.5, mean CG 36.9± 0.6 p<0.05) and 10mins (mean MSG 36.4±0.4, mean CG 37.0±0.3p<0.05) post-exercise. MS HR remained marginally above preexercise HR values at 10 minutes post-exercise. Differential measures of RPE for both groups recovered to pre-exercise values at 5 mins (±SD). During maximal exertion, it was observed that PwMS irrespective of disease classification, or years from onset were neither limited by their heart rate, nor their breathing, but that leg fatigue or lack of central drive to the lower limb was the reason for their inability to continue. In the third study, the physiological perceptive and central responses of PwMS were explored during exercise at low and high intensity, and through the timecourse to recovery. Participants performed 2 exercise training (ET) sessions where they performed 20 minutes of exercise on a cycle ergometer at 45% (ET45) and 60% (ET60) relative to peak watts determined during a GXT. 12 MSG and 9 CG completed the 2 exercise sessions. Repeated measures ANOVA revealed no significant differences in groups’baseline measures of HR, Temp°C, RPEbr, RPEleg or TMS measures between-groups or between-sessions. When comparing groups during ET45, measures of all variables were similar, except for RPE leg at 14mins,(mean MSG 3.3 ±1.1, CG 2.1±1.2 p<0.05). During ET60 MSG HR was higher from 14mins (mean 107.8bpm ±12.6 bpm, CG 136.8 bpm ±13.8 p<0.05). When comparing the results of MSG ET45 and ET60, during the 35 minute postexercise phase MSG HR recovered to pre-exercise values at 10 mins (mean HR 71.4bpm ±12.7, baseline 63.8 bpm ±9.8 p>0.05) after ET45, while post-ET60 HR failed to recover before session-end (mean HR 83 bpm ±11.3, baseline 64.6 bpm ±8.2, p<0.05). TMS measures were significantly depressed after both training sessions. Mean MEP size were 71% ±38% of pre-exercise levels at 30 secs post-ET45 (p<0.05) and 52% ±17.8% post ET60 at 2 minutes (p<0.05). Post-ET45 MEPs recovered to pre-exercise values at 10mins while post-ET-60 MEPs recovered at 20 mins. MEP latency and MEPρeriph were unchanged. Following ET60 we observed a strong negative relationship between Temp°C and MEPs (r=-.65, p=0.023). The investigation revealed significant, intensity-dependent, physiological and perceptive differences, during exercise and through the time-course to recovery. Analysis of responses to post-exercise TMS revealed a significant depression in corticospinal excitability, with a clear intensity-dependent difference in the depth and duration of MEP depression. In addition, an inverse relationship was found between internal body temperature and corticospinal excitability. The results may offer further guidance to clinicians for the provision of safe, appropriate and effective exercise prescription to PwMS

Fabrication of titanium multi-wall Thermal Protection System (TPS) test panel arrays

Several arrays were designed and tested. Tests included vibrational and acoustical tests, radiant heating tests, and thermal conductivity tests. A feasible manufacturing technique was established for producing the protection system panels

Re-design and fabrication of titanium multi-wall Thermal Protection System (TPS) test panels

The Titanium Multi-wall Thermal Protection System (TIPS) panel was re-designed to incorporate Ti-6-2-4-2 outer sheets for the hot surface, ninety degree side closures for ease of construction and through panel fastness for ease of panel removal. Thermal and structural tests were performed to verify the design. Twenty-five panels were fabricated and delivered to NASA for evaluation at Langley Research Center and Johnson Space Center

Interactions among Dogs, People, and the Environment in Boulder, Colorado: A Case Study

From September 1995 to April 1996 we studied interactions among dogs, people, and the environment in Boulder, Colorado. Data on behavioral disturbances by off-leash dogs who were accompanied by a person were collected with respect to dog-dog and dog-human interactions, dog-wildlife encounters, dogs trampling vegetation, and dogs entering and disturbing bodies of water. A questionnaire also was administered. Behavioral data showed that off-leash dogs generally did not travel far off trail, that when they did it was for short periods of time, and that they rarely were observed to chase other dogs, disturb people, chase wildlife, destroy vegetation, or enter bodies of water. Results from analyses of the questionnaire (skewed toward non-dog owners) showed that dog owners and non-dog owners agreed that people were more disruptive to the environment than dogs and that unruly people were more problematic than unruly dogs. We conclude that the well-being and interests of dogs should not summarily and dismissively be compromised when dogs and people attempt to share limited space that can be used by all parties for recreational purposes. Indeed, a higher percentage of people reported that the quality of dogs’ experience of the outdoors would be compromised more than their own enjoyment if dogs could not walk off-leash in areas where this is currently permitted. The methods used and the results from this case study can serve as a model for other locations in which dogs and people compete for limited spatial resources

Synchronization of many nano-mechanical resonators coupled via a common cavity field

Using amplitude equations, we show that groups of identical nano-mechanical resonators, interacting with a common mode of a cavity microwave field, synchronize to form a single mechanical mode which couples to the cavity with a strength dependent on the square sum of the individual mechanical-microwave couplings. Classically this system is dominated by periodic behaviour which, when analyzed using amplitude equations, can be shown to exhibit multi-stability. In contrast groups of sufficiently dissimilar nano-mechanical oscillators may lose synchronization and oscillate out of phase at significantly higher amplitudes. Further the method by which synchronization is lost resembles that for large amplitude forcing which is not of the Kuramoto form.Comment: 23 pages, 11 figure

Surface excitonic emission and quenching effects in ZnO nanowire/nanowall systems: limiting effects on device potential.

We report ZnO nanowire/nanowall growth using a two-step vapour phase transport method on a-plane sapphire. X-ray diffraction and scanning electron microscopy data establish that the nanostructures are vertically well-aligned with c-axis normal to the substrate, and have a very low rocking curve width. Photoluminescence data at low temperatures demonstrate the exceptionally high optical quality of these structures, with intense emission and narrow bound exciton linewidths. We observe a high energy excitonic emission at low temperatures close to the band-edge which we assign to the surface exciton in ZnO at ~ 3.366 eV, the first time this feature has been reported in ZnO nanorod systems. This assignment is consistent with the large surface to volume ratio of the nanowire systems and indicates that this large ratio has a significant effect on the luminescence even at low temperatures. The band-edge intensity decays rapidly with increasing temperature compared to bulk single crystal material, indicating a strong temperature-activated non-radiative mechanism peculiar to the nanostructures. No evidence is seen of the free exciton emission due to exciton delocalisation in the nanostructures with increased temperature, unlike the behaviour in bulk material. The use of such nanostructures in room temperature optoelectronic devices appears to be dependent on the control or elimination of such surface effects

Socioeconomic status and the brain: mechanistic insights from human and animal research

Human brain development occurs within a socioeconomic context and childhood socioeconomic status (SES) influences neural development — particularly of the systems that subserve language and executive function. Research in humans and in animal models has implicated prenatal factors, parent–child interactions and cognitive stimulation in the home environment in the effects of SES on neural development. These findings provide a unique opportunity for understanding how environmental factors can lead to individual differences in brain development, and for improving the programmes and policies that are designed to alleviate SES-related disparities in mental health and academic achievement

Effect of Motion on the ADC Quantification Accuracy of Whole-Body DWIBS

y Diffusion-weighted whole-body imaging with background body signal subtraction was introduced as a qualitative approach to detecting metastases in the body. A liver-mimicking phantom with embedded tumours that could be moved to replicate respiratory motion was developed to assess its ability to accurately quantify ADC values. RESULTS: Mean tumour ADC values were unaltered by the motion; however, a significant (p \u3c 0.05) increase in the spread of ADC values was measured, even for relatively large tumours. CONCLUSIONS: These findings may be of significance in cancer therapy monitoring where subtle changes in ADC histograms may reveal changes in tumour heterogeneity

Don’t take it personally:Analyzing gender and age differences in ratings of online humor

Computational humor detection systems rarely model the subjectivity of humor responses, or consider alternative reactions to humor - namely offense. We analyzed a large dataset of humor and offense ratings by male and female annotators of different age groups. We find that women link these two concepts more strongly than men, and they tend to give lower humor ratings and higher offense scores. We also find that the correlation between humor and offense increases with age. Although there were no gender or age differences in humor detection, women and older annotators signalled that they did not understand joke texts more often than men. We discuss implications for computational humor detection and downstream tasks

Fabrication of prepackaged superalloy honeycomb Thermal Protection System (TPS) panels

High temperature materials were surveyed, and Inconel 617 and titanium were selected for application to a honeycomb TPS configuration designed to withstand 2000 F. The configuration was analyzed both thermally and structurally. Component and full-sized panels were fabricated and tested to obtain data for comparison with analysis. Results verified the panel design. Twenty five panels were delivered to NASA Langley Research Center for additional evaluation