Biomechanical demands differentiate transitioning vs. continuous stair ascent gait in older women

Background Stair ascent mechanics change with age, but little is known about the differing functional demands of transitioning and continuous ascent. Work investigating the risky transition from gait to ascent is sparse, and the strategies that older adults adopt to achieve these demanding tasks have not been investigated. Methods This study compared the biomechanics of a 2-step transitional (floor-to-step2) and continuous ascent cycle (step1-to-step3) and investigated the role of limb preference in relation to dynamometer-derived knee strength during this transition. A biomechanical analysis of 36 women (60–83 years) ascending a 3-step staircase was conducted. Findings The 2-step transitioning cycle was completed quicker, with a larger range of motion, increased forces, larger knee flexor and dorsiflexor moments and ankle powers (P ≤ 0.05), but reduced hip and knee flexion, smaller hip extensor moments and hip and knee powers compared to continuous ascent. During the transition, 44% of the participants demonstrated a consistent limb preference. In these cases large between-limb extensor strength differences existed (13.8%) and 71% of these participants utilised the stronger limb to execute the 2-step transitional cycle. Interpretation The preferential stronger-limb 2-step transitioning strategy conflicts with previous recommendations of a stronger lead limb for frail/asymmetric populations. Our findings suggest that most healthy older women with large between-limb differences utilise the stronger limb to achieve the considerable propulsion required to redirect momentum during the 2-step transition. The biomechanical demands of ascent, relative to limb strength, can inform exercise programmes by targeting specific muscle groups to help older adults maintain/improve general functioning

Kinematic differences exist between transtibial amputee fallers and non-fallers during downwards step transitioning.

Stair negotiation is biomechanically more challenging than level gait. There are few biomechanical assessments of transtibial amputees descending stairs and none specifically related to falls. Stair descent may elicit more differences than level gait in amputees with and without a previous falls history

Survey for Transiting Extrasolar Planets in Stellar Systems IV: Variables in the Field of NGC 1245

The Survey for Transiting Extrasolar Planets in Stellar Systems (STEPSS) project is a search for planetary transits in open clusters. In this paper, we analyze the STEPSS observations of the open cluster NGC 1245 to determine the variable star content of the cluster. Out of 6787 stars observed with V < 22, of which ~870 are cluster members, we find 14 stars with clear intrinsic variability that are potential cluster members, and 29 clear variables that are not cluster members. None of these variables have been previously identified. We present light curves, finding charts, and stellar/photometric data on these variable objects. Several of the interacting binaries have estimated distances consistent with the cluster distance determined from isochrone fits to the color magnitude diagram. Four stars at the main sequence turnoff of the cluster have light curves consistent with gamma Doradus variability. If these gamma Doradus candidates are confirmed, they represent the oldest and coolest members of this class of variable discovered to date.Comment: 20 pages, 15 figures. Submitted to AJ. PDF version with full-resolution figures at http://www.astronomy.ohio-state.edu/~pepper/ms.pd

On the stability of fissured slopes subject to seismic action

A set of analytical solutions achieved by the upper bound theorem of limit analysis and the pseudo-static approach is presented for the assessment of the stability of homogeneous c, ϕ slopes manifesting vertical cracks and subject to seismic action. Rotational failure mechanisms are considered for slopes with cracks of either known or unknown depth and location. A validation exercise was carried out based on numerical limit analyses and displacement-based finite-element analyses with strength reduction technique. Charts providing the stability factor for fissured slopes subject to both horizontal and vertical accelerations for any combination of c, ϕ and slope inclination are provided. The effect of the direction of the vertical acceleration on slope stability is specifically analysed. Yield seismic coefficients are also provided. When the presence of cracks within the slope can be ascertained with reasonable confidence, maps showing the zones within the slope where they have no destabilising effect are provided. Finally, Newmark's method was employed to assess the effect of cracks on earthquake induced displacements. To this end, displacement coefficients are provided in chart form as a function of the slope characteristics. Two examples of slopes subjected to known earthquakes are illustrated

Asteroseismology from space: the Delta Scuti star Theta2 Tauri monitored by the WIRE satellite

The first intensive photometric time-series of a Delta Scuti star was obtained from space. Theta2 Tau was monitored with the star camera on the Wide-Field Infrared Explorer (WIRE) satellite. Twelve independent frequencies were detected down to the 0.5 mmag amplitude level. Their reality was investigated by searching for them using two different algorithms and by some internal checks. All the frequencies are in the range 10.8-14.6 c\d. The histogram of the frequency spacings shows that 81% are below 1.8 c\d; rotation may thus play a role in the mode excitation. The fundamental radial mode is not observed, although it is expected to occur in a region where the noise level is very low (55 micromag). The rms residual is about two times lower than that usually obtained from successful ground--based multisite campaigns. The comparison of the results of previous campaigns with the new ones establishes the amplitude variability of some modes.Comment: 7 pages (in A&A style), 7 eps figures. Accepted for A&A Main Journa

Performance of the ground-based total ozone network assessed using satellite data

Dobson and Brewer spectrophotometer and filter ozonometer data available from the World Ozone and Ultraviolet Data Centre (WOUDC) were compared with satellite total ozone measurements from TOMS (onboard Nimbus 7, Meteor 3, and Earth Probe satellites), OMI (AURA satellite) and GOME (ERS-2 satellite) instruments. Five characteristics of the difference with satellite data were calculated for each site and instrument type: the mean difference, the standard deviation of daily differences, the standard deviation of monthly differences, the amplitude of the seasonal component of the difference, and the range of annual values. All these characteristics were calculated for five 5-year-long bins and for each site separately for direct sun (DS) and zenith sky (ZS) ozone measurements. The main percentiles were estimated for the five characteristics of the difference and then used to establish criteria for “suspect” or “outlier” sites for each characteristic. About 61% of Dobson, 46% of Brewer, and 28% of filter stations located between 60°S and 60°N have no “suspect” or “outlier” characteristics. In nearly 90% of all cases, Dobson and Brewer sites demonstrated 5-year mean differences with satellites to be within ±3% (for DS observations). The seasonal median difference between all Brewer DS measurements at 25°–60°N and GOME and OMI overpasses remained within ±0.5% over a period of more than 10 years (...

Universality of the Lyapunov regime for the Loschmidt echo

The Loschmidt echo (LE) is a magnitude that measures the sensitivity of quantum dynamics to perturbations in the Hamiltonian. For a certain regime of the parameters, the LE decays exponentially with a rate given by the Lyapunov exponent of the underlying classically chaotic system. We develop a semiclassical theory, supported by numerical results in a Lorentz gas model, which allows us to establish and characterize the universality of this Lyapunov regime. In particular, the universality is evidenced by the semiclassical limit of the Fermi wavelength going to zero, the behavior for times longer than Ehrenfest time, the insensitivity with respect to the form of the perturbation and the behavior of individual (non-averaged) initial conditions. Finally, by elaborating a semiclassical approximation to the Wigner function, we are able to distinguish between classical and quantum origin for the different terms of the LE. This approach renders an understanding for the persistence of the Lyapunov regime after the Ehrenfest time, as well as a reinterpretation of our results in terms of the quantum--classical transition.Comment: 33 pages, 17 figures, uses Revtex