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

A study of the kinematics and binary-induced shaping of the planetary nebula HaTr 4

We present the first detailed spatio-kinematical analysis and modelling of the planetary nebula HaTr 4, one of few known to contain a post-common-envelope central star system. Common envelope evolution is believed to play an important role in the shaping of planetary nebulae, but the exact nature of this role is yet to be understood. High spatial- and spectral- resolution spectroscopy of the [OIII]5007 nebular line obtained with VLT-UVES are presented alongside deep narrowband Ha+[NII]6584 imagery obtained using EMMI-NTT, and together the two are used to derive the three-dimensional morphology of HaTr 4. The nebula is found to display an extended ovoid morphology with an enhanced equatorial region consistent with a toroidal waist - a feature believed to be typical amongst planetary nebulae with post-common-envelope central stars. The nebular symmetry axis is found to lie perpendicular to the orbital plane of the central binary, concordant with the idea that the formation and evolution of HaTr 4 has been strongly influenced by its central binary.Comment: 9 pages, 5 figures, accepted for publication in MNRA

A Buffer Stocks Model for Stabilizing Price of Staple Food with Considering the Expectation of Non Speculative Wholesaler

This paper is a study of price stabilization in the staple food distribution system. All stakeholders experience market risks due to some possibility causes of price volatility. Many models of price stabilization had been developed by employing several approaches such as floor-ceiling prices, buffer funds, export or import taxes, and subsidies. In the previous researches, the models were expanded to increase the purchasing price for producer and decrease the selling price for consumer. Therefore, the policy can influence the losses for non-speculative wholesaler that is reflected by the descending of selling quantity and ascending of the stocks. The objective of this model is not only to keep the expectation of both producer and consumer, but also to protect non-speculative wholesaler from the undesirable result of the stabilization policy. A nonlinear programming model was addressed to determine the instruments of intervention program. Moreover, the result shows that the wholesaler behavior affects the intervention costs. Index Terms Buffer stocks, Price stabilization, Nonlinear programming, Wholesaler behavior

Gamma-Ray Bursts observed by XMM-Newton

Analysis of observations with XMM-Newton have made a significant contribution to the study of Gamma-ray Burst (GRB) X-ray afterglows. The effective area, bandpass and resolution of the EPIC instrument permit the study of a wide variety of spectral features. In particular, strong, time-dependent, soft X-ray emission lines have been discovered in some bursts. The emission mechanism and energy source for these lines pose major problems for the current generation of GRB models. Other GRBs have intrinsic absorption, possibly related to the environment around the progenitor, or possible iron emission lines similar to those seen in GRBs observed with BeppoSAX. Further XMM-Newton observations of GRBs discovered by the Swift satellite should help unlock the origin of the GRB phenomenon over the next few years.Comment: To appear in proceedings of the "XMM-Newton EPIC Consortium meeting, Palermo, 2003 October 14-16", published in Memorie della Societa Astronomica Italian

A periodically active pulsar giving insight into magnetospheric physics

PSR B1931+24 (J1933+2421) behaves as an ordinary isolated radio pulsar during active phases that are 5-10 days long. However, the radio emission switches off in less than 10 seconds and remains undetectable for the next 25-35 days, then it switches on again. This pattern repeats quasi-periodically. The origin of this behaviour is unclear. Even more remarkably, the pulsar rotation slows down 50% faster when it is on than when it is off. This indicates a massive increase in magnetospheric currents when the pulsar switches on, proving that pulsar wind plays a substantial role in pulsar spin-down. This allows us, for the first time, to estimate the currents in a pulsar magnetospheric during the occurrence of radio emission.Comment: 12 pages, 2 figure

Deep optical imaging of nova remnants II. A southern-sky sample

We present an optical imaging study of 20 southern-sky nova remnants which has resulted in the discovery of four previously unknown nova shells -- V842 Cen, RR Cha, DY Pup and HS Pup. The study has also revealed previously unobserved features in three other known shells -- those of BT Mon, CP Pup and RR Pic. The images of BT Mon, V842 Cen, RR Cha, DY Pup and HS Pup have been processed using several deconvolution algorithms (Richardson-Lucy, maximum entropy and clean) in addition to straightforward point-source subtraction in an attempt to resolve the shells from the central stars. The use of four different methods enables us to make a qualitative judgement of the results. Notably, the shell of RR Pic displays tails extending outwards from clumps in the main ejecta similar to those previously detected in DQ Her.Comment: Accepted for publication by MNRA

Swift observations of the 2006 outburst of the recurrent nova RS Ophiuchi: II. 1D hydrodynamical models of wind driven shocks

Following the early Swift X-ray observations of the latest outburst of the recurrent nova RS Ophiuchi in February 2006 (Paper I), we present new 1D hydrodynamical models of the system which take into account all three phases of the remnant evolution. The models suggest a novel way of modelling the system by treating the outburst as a sudden increase then decrease in wind mass-loss rate and velocity. The differences between this wind model and previous Primakoff-type simulations are described. A more complex structure, even in 1D, is revealed through the presence of both forward and reverse shocks, with a separating contact discontinuity. The effects of radiative cooling are investigated and key outburst parameters such as mass-loss rate, ejecta velocity and mass are varied. The shock velocities as a function of time are compared to the ones derived in Paper I. We show how the manner in which the matter is ejected controls the evolution of the shock and that for a well-cooled remnant, the shock deceleration rate depends on the amount of energy that is radiated away.Comment: 9 pages, 5 figure