Dynamics of leg muscle function in tammar wallabies (M. eugenii) during level versus incline hopping

The goal of our study was to examine whether the in vivo force-length behavior, work and elastic energy savings of distal muscle-tendon units in the legs of tammar wallabies (Macropus eugenii) change during level versus incline hopping. To address this question, we obtained measurements of muscle activation (via electromyography), fascicle strain (via sonomicrometry) and muscle-tendon force (via tendon buckles) from the lateral gastrocnemius (LG) and plantaris (PL) muscles of tammar wallabies trained to hop on a level and an inclined (10°, 17.4% grade) treadmill at two speeds (3.3 m s^(-1) and 4.2 m s^(-1)). Similar patterns of muscle activation, force and fascicle strain were observed under both level and incline conditions. This also corresponded to similar patterns of limb timing and movement (duty factor, limb contact time and hopping frequency). During both level and incline hopping, the LG and PL exhibited patterns of fascicle stretch and shortening that yielded low levels of net fascicle strain [LG: level, -1.0±4.6% (mean ± s.e.m.) vs incline, 0.6±4.5%; PL: level, 0.1±1.0% vs incline, 0.4±1.6%] and muscle work (LG: level, -8.4±8.4 J kg^(-1) muscle vs incline, -6.8±7.5 J kg^(-1) muscle; PL: level, -2.0±0.6 J kg^(-1) muscle vs incline, -1.4±0.7 J kg^(-1) muscle). Consequently, neither muscle significantly altered its contractile dynamics to do more work during incline hopping. Whereas electromyographic (EMG) phase, duration and intensity did not differ for the LG, the PL exhibited shorter but more intense periods of activation, together with reduced EMG phase (P<0.01), during incline versus level hopping. Our results indicate that design for spring-like tendon energy savings and economical muscle force generation is key for these two distal muscle-tendon units of the tammar wallaby, and the need to accommodate changes in work associated with level versus incline locomotion is achieved by more proximal muscles of the limb

The LATDYN user's manual

The LATDYN User's Manual presents the capabilities and instructions for the LATDYN (Large Angle Transient DYNamics) computer program. The LATDYN program is a tool for analyzing the controlled or uncontrolled dynamic transient behavior of interconnected deformable multi-body systems which can undergo large angular motions of each body relative other bodies. The program accommodates large structural deformation as well as large rigid body rotations and is applicable, but not limited to, the following areas: (1) development of large flexible space structures; (2) slewing of large space structure components; (3) mechanisms with rigid or elastic components; and (4) robotic manipulations of beam members. Presently the program is limited to two dimensional problems, but in many cases, three dimensional problems can be exactly or approximately reduced to two dimensions. The program uses convected finite elements to affect the large angular motions involved in the analysis. General geometry is permitted. Detailed user input and output specifications are provided and discussed with example runstreams. To date, LATDYN has been configured for CDC/NOS and DEC VAX/VMS machines. All coding is in ANSII-77 FORTRAN. Detailed instructions regarding interfaces with particular computer operating systems and file structures are provided

Probing the Pulsar Wind Nebula of PSR B0355+54

We present XMM-Newton and Chandra X-ray observations of the middle-aged radio pulsar PSR B0355+54. Our X-ray observations reveal emission not only from the pulsar itself, but also from a compact diffuse component extending ~50'' in the opposite direction to the pulsar's proper motion. There is also evidence for the presence of fainter diffuse emission extending ~5' from the point source. The compact diffuse feature is well-fitted with a power-law, the index of which is consistent with the values found for other pulsar wind nebulae. The morphology of the diffuse component is similar to the ram-pressure confined pulsar wind nebulae detected for other sources. The X-ray emission from the pulsar itself is described well by a thermal plus power-law fit, with the thermal emission most likely originating in a hot polar cap.Comment: 9 pages (uses emulateapj.cls), 8 figures, 2 tables, accepted for publication in Ap

Optical Follow-up of New SMC Wing Be/X-ray Binaries

We investigate the optical counterparts of recently discovered Be/X-ray binaries in the Small Magellanic Cloud. In total four sources, SXP101, SXP700, SXP348 and SXP65.8 were detected during the Chandra Survey of the Wing of the SMC. SXP700 and SXP65.8 were previously unknown. Many optical ground based telescopes have been utilised in the optical follow-up, providing coverage in both the red and blue bands. This has led to the classification of all of the counterparts as Be stars and confirms that three lie within the Galactic spectral distribution of known Be/X-ray binaries. SXP101 lies outside this distribution becoming the latest spectral type known. Monitoring of the Halpha emission line suggests that all the sources bar SXP700 have highly variable circumstellar disks, possibly a result of their comparatively short orbital periods. Phase resolved X-ray spectroscopy has also been performed on SXP65.8, revealing that the emission is indeed harder during the passage of the X-ray beam through the line of sight.Comment: 9 pages, 9 figures, 2 tables, accepted for publication in MNRA

INTEGRAL observations of the Small Magellanic Cloud

The first INTEGRAL observations of the Small Magellanic Cloud (carried out in 2003) are reported in which two sources are clearly detected. The first source, SMC X-1, shows a hard X-ray eclipse and measurements of its pulse period indicate a continuation of the long-term spin-up now covering ~30 years. The second source is likely to be a high mass X-ray binary, and shows a potential periodicity of 6.8s in the IBIS lightcurve. An exact X-ray or optical counterpart cannot be designated, but a number of proposed counterparts are discussed. One of these possible counterparts shows a strong coherent optical modulation at ~2.7d, which, together with the measured hard X-ray pulse period, would lead to this INTEGRAL source being classified as the fourth known high mass Roche lobe overflow system.Comment: Accepted for publication in MNRA

Utilization of the Building-Block Approach in Structural Mechanics Research

In the last 20 years NASA has worked in collaboration with industry to develop enabling technologies needed to make aircraft safer and more affordable, extend their lifetime, improve their reliability, better understand their behavior, and reduce their weight. To support these efforts, research programs starting with ideas and culminating in full-scale structural testing were conducted at the NASA Langley Research Center. Each program contained development efforts that (a) started with selecting the material system and manufacturing approach; (b) moved on to experimentation and analysis of small samples to characterize the system and quantify behavior in the presence of defects like damage and imperfections; (c) progressed on to examining larger structures to examine buckling behavior, combined loadings, and built-up structures; and (d) finally moved to complicated subcomponents and full-scale components. Each step along the way was supported by detailed analysis, including tool development, to prove that the behavior of these structures was well-understood and predictable. This approach for developing technology became known as the "building-block" approach. In the Advanced Composites Technology Program and the High Speed Research Program the building-block approach was used to develop a true understanding of the response of the structures involved through experimentation and analysis. The philosophy that if the structural response couldn't be accurately predicted, it wasn't really understood, was critical to the progression of these programs. To this end, analytical techniques including closed-form and finite elements were employed and experimentation used to verify assumptions at each step along the way. This paper presents a discussion of the utilization of the building-block approach described previously in structural mechanics research and development programs at NASA Langley Research Center. Specific examples that illustrate the use of this approach are included from recent research and development programs for both subsonic and supersonic transports

Platelet-rich plasmapheresis in cardiac surgery: A meta-analysis of the effect on transfusion requirements

AbstractObjective:Our purpose was to determine whether intraoperative platelet-rich plasmapheresis in cardiac surgery is effective in reducing the proportion of patients exposed to allogeneic red cell transfusions. Methods: A systematic search for prospective, randomized trials of platelet-rich plasmapheresis in cardiac surgery, using MEDLINE, HEALTHSTAR, Current Contents, “Biological Abstracts,” and EMBASE/Excerpta Medica up to August 1997, was completed. Trials were included if they reported either the proportion of patients exposed to allogeneic red cells or the units of allogeneic red cells transfused. Trials were abstracted by 2 independent investigators and the quality of trial design was assessed with the use of a validated scale. Results: Seventeen references met the inclusion criteria (1369 patients [675 control: 694 platelet-rich plasmapheresis]). Platelet-rich plasmapheresis reduced the likelihood of exposure to allogeneic red cells in cardiac surgery (odds ratio 0.44; 95% confidence interval 0.27, 0.72, P = .001). Platelet-rich plasmapheresis had a small but statistically significant effect on both the volume of blood lost in the first 24 hours (weighted mean difference –102 mL; 95% confidence interval –148, –55 mL, P < .0001) and the mean units transfused (weighted mean difference –0.33 units; 95% confidence interval –0.43, –0.23, P < .0001). However, platelet-rich plasmapheresis was only marginally effective (odds ratio 0.83, 95% confidence interval 0.34, 2.01, P = .68) for “good” quality trials, whereas it appeared very effective in trials with poor methodologic quality (odds ratio 0.33, 95% confidence interval 0.17, 0.62, P = .0007). Conclusions: Although platelet-rich plasmapheresis appeared effective in decreasing the proportion of patients receiving transfusions after cardiac operations, the quality of most of the supporting trials was low and the benefit was small in trials of good quality. Further clinical trials should be completed. (J Thorac Cardiovasc Surg 1998;116:641-7