Validity of the activPAL3 activity monitor in people moderately affected by Multiple Sclerosis

Background: Walking is the primary form of physical activity performed by people with Multiple Sclerosis (MS), therefore it is important to ensure the validity of tools employed to measure walking activity. The aim of this study was to assess the criterion validity of the activPAL3 activity monitor during overground walking in people with MS.\ud Methods: Validity of the activPAL3 accelerometer was compared to video observation in 20 people moderately affected by MS. Participants walked 20-30m twice along a straight quiet corridor at a comfortable speed.\ud Results: Inter-rater reliability of video observations was excellent (all intraclass correlations > 0.99). The mean difference (activPAL3- mean of raters) was -4.70 ± 9.09, -4.55 s ± 10.76 and 1.11 s ± 1.11 for steps taken, walking duration and upright duration respectively. These differences represented 8.7, 10.0 and 1.8% of the mean for each measure respectively. The activPAL3 tended to underestimate steps taken and walking duration in those who walked at cadences of ≤ 38 steps/minute by 60% and 47% respectively.\ud Discussion: The activPAL3 is valid for measuring walking activity in people moderately affected by MS. It is accurate for upright duration regardless of cadence. In participants with slow walking cadences, outcomes of steps taken and walking duration should be interpreted with caution

Angular dependent vortex pinning mechanisms in YBCO coated conductors and thin films

We present a comparative study of the angular dependent critical current density in YBa2Cu3O7 films deposited on IBAD MgO and on single crystal MgO and SrTiO3 substrates. We identify three angular regimes where pinning is dominated by different types of correlated and uncorrelated defects. We show that those regimes are present in all cases, indicating that the pinning mechanisms are the same, but their extension and characteristics are sample dependent, reflecting the quantitative differences in texture and defect density. In particular, the more defective nature of the films on IBAD turns into an advantage as it results in stronger vortex pinning, demonstrating that the critical current density of the films on single crystals is not an upper limit for the performance of the IBAD coated conductors.Comment: 14 pages, 3 figures. Submitted to AP

The Woods-Saxon Potential in the Dirac Equation

The two-component approach to the one-dimensional Dirac equation is applied to the Woods-Saxon potential. The scattering and bound state solutions are derived and the conditions for a transmission resonance (when the transmission coefficient is unity) and supercriticality (when the particle bound state is at E=-m) are then derived. The square potential limit is discussed. The recent result that a finite-range symmetric potential barrier will have a transmission resonance of zero-momentum when the corresponding well supports a half-bound state at E=-m is demonstrated.Comment: 8 pages, 4 figures. Submitted to JPhys

Web-based physiotherapy for people affected by multiple sclerosis: a single blind, randomized controlled feasibility study

Objective: To examine the feasibility of a trial to evaluate web-based physiotherapy compared to a standard home exercise programme in people with multiple sclerosis. Design: Multi-centre, randomized controlled, feasibility study. Setting: Three multiple sclerosis out-patient centres. Participants: A total of 90 people with multiple sclerosis (Expanded Disability Status Scale 4–6.5). Interventions: Participants were randomized to a six-month individualized, home exercise programme delivered via web-based physiotherapy (n = 45; intervention) or a sheet of exercises (n = 45; active comparator). Outcome measures: Outcome measures (0, three, six and nine months) included adherence, two-minute walk test, 25 foot walk, Berg Balance Scale, physical activity and healthcare resource use. Interviews were undertaken with 24 participants and 3 physiotherapists. Results: Almost 25% of people approached agreed to take part. No intervention-related adverse events were recorded. Adherence was 40%–63% and 53%–71% in the intervention and comparator groups. There was no difference in the two-minute walk test between groups at baseline (Intervention-80.4(33.91)m, Comparator-70.6(31.20)m) and no change over time (at six-month Intervention-81.6(32.75)m, Comparator-74.8(36.16)m. There were no significant changes over time in other outcome measures except the EuroQol-5 Dimension at six months which decreased in the active comparator group. For a difference of 8(17.4)m in two-minute walk test between groups, 76 participants/group would be required (80% power, P > 0.05) for a future randomized controlled trial. Conclusion: No changes were found in the majority of outcome measures over time. This study was acceptable and feasible by participants and physiotherapists. An adequately powered study needs 160 participants

emiT: an apparatus to test time reversal invariance in polarized neutron decay

We describe an apparatus used to measure the triple-correlation term (\D \hat{\sigma}_n\cdot p_e\times p_\nu) in the beta-decay of polarized neutrons. The \D-coefficient is sensitive to possible violations of time reversal invariance. The detector has an octagonal symmetry that optimizes electron-proton coincidence rates and reduces systematic effects. A beam of longitudinally polarized cold neutrons passes through the detector chamber, where a small fraction beta-decay. The final-state protons are accelerated and focused onto arrays of cooled semiconductor diodes, while the coincident electrons are detected using panels of plastic scintillator. Details regarding the design and performance of the proton detectors, beta detectors and the electronics used in the data collection system are presented. The neutron beam characteristics, the spin-transport magnetic fields, and polarization measurements are also described.Comment: 15 pages, 13 figure

The Otterbein Miscellany - May 1965

https://digitalcommons.otterbein.edu/miscellany/1011/thumbnail.jp

Search for a T-odd, P-even Triple Correlation in Neutron Decay

Background: Time-reversal-invariance violation, or equivalently CP violation, may explain the observed cosmological baryon asymmetry as well as signal physics beyond the Standard Model. In the decay of polarized neutrons, the triple correlation D\cdot(p_{e}\timesp_{\nu}) is a parity-even, time-reversal- odd observable that is uniquely sensitive to the relative phase of the axial-vector amplitude with respect to the vector amplitude. The triple correlation is also sensitive to possible contributions from scalar and tensor amplitudes. Final-state effects also contribute to D at the level of 1e-5 and can be calculated with a precision of 1% or better. Purpose: We have improved the sensitivity to T-odd, P-even interactions in nuclear beta decay. Methods: We measured proton-electron coincidences from decays of longitudinally polarized neutrons with a highly symmetric detector array designed to cancel the time-reversal-even, parity-odd Standard-Model contributions to polarized neutron decay. Over 300 million proton-electron coincidence events were used to extract D and study systematic effects in a blind analysis. Results: We find D = [-0.94\pm1.89(stat)\pm0.97(sys)]e-4. Conclusions: This is the most sensitive measurement of D in nuclear beta decay. Our result can be interpreted as a measurement of the phase of the ratio of the axial-vector and vector coupling constants (CA/CV= |{\lambda}|exp(i{\phi}_AV)) with {\phi}_AV = 180.012{\deg} \pm0.028{\deg} (68% confidence level) or to constrain time-reversal violating scalar and tensor interactions that arise in certain extensions to the Standard Model such as leptoquarks. This paper presents details of the experiment, analysis, and systematic- error corrections.Comment: 21 pages, 22 figure

A Neutron Star Binary Merger Model for GW170817/GRB170817a/SSS17a

The merging neutron star gravitational wave event GW170817 has been observed throughout the entire electromagnetic spectrum from radio waves to $\gamma$-rays. The resulting energetics, variability, and light curves are shown to be consistent with GW170817 originating from the merger of two neutron stars, in all likelihood followed by the prompt gravitational collapse of the massive remnant. The available $\gamma$-ray, X-ray and radio data provide a clear probe for the nature of the relativistic ejecta and the non-thermal processes occurring within, while the ultraviolet, optical and infrared emission are shown to probe material torn during the merger and subsequently heated by the decay of freshly synthesized $r$-process material. The simplest hypothesis that the non-thermal emission is due to a low-luminosity short $\gamma$-ray burst (sGRB) seems to agree with the present data. While low luminosity sGRBs might be common, we show here that the collective prompt and multi-wavelength observations are also consistent with a typical, powerful sGRB seen off-axis. Detailed follow-up observations are thus essential before we can place stringent constraints on the nature of the relativistic ejecta in GW170817.Comment: 9 pages, 5 figures, accepted to ApJ Letter