Identifying Central Patterns of Motor Control in Pathological Gait

Introduction: The central pattern generator (CPG) for walking is an open loop system that drives lower limb movements in a relatively rhythmic fashion once motion has started with minimal need for additional afferent input. The role of the CPG in the pathological gait of Incomplete Spinal Cord Injury (ISCI) and Parkinson’s Disease (PD) has not been studied thoroughly. Understanding how the CPG contributes to motor control in these special populations will serve as a standard upon which to compare new treatments to improve gait function. The purpose of this study was to identify the expression of CPG patterns in individuals with ISCI and PD during walking and compare them to normative values. Methods: Thirty (N=30) subjects participated in this study equally divided amongst the following three groups: ISCI, PD, and healthy control subjects. Surface electromyography (SEMG) was used to record muscle activation from the medial gastrocnemius, tibialis anterior, biceps femoris-short head, and vastus lateralis bilaterally. A foot switch was used to mark right heel contact (Datalog, Biometrics). All SEMG signals were normalized with respect to Maximal Voluntary Isometric Contraction (MVIC). Participants then performed three trials of reciprocal over ground walking (OGW) for 10m using their preferred gait aids. Following this, subjects walked on a treadmill (TM) for three trials of 60s. SEMG data was rectified, filtered and time-normalized. Four basic muscle synergies representing the CPG were extracted from the data. The expression of these synergies during the gait cycle was computed using a least-squares method in MATLAB software. Goodness of fit of the CPG model was evaluated using the Coefficient of determination (r2). Results: All subjects demonstrated an increase in CPG representation during treadmill walking compared to over ground walking. Incomplete ISCI, PD, and control subjects demonstrated the following r2 values for gait respectively 0.4 OGW, 0.55 TM; 0.8 OGW, 0.9 TM; 0.7 OGW, and 0.8 TM. The differences between groups was statistically significant (p\u3c0.05). Conclusions: The results suggest that individuals with PD present dynamic locomotor patterns more consistent with a CPG model of muscle activation when engaging in over ground and treadmill walking. Further studies are warranted to corroborate if the festination gait seen in PD is more rhythmic and how anti-PD medication affects CPG activity. ISCI subjects may have had poor coordinated action of their CPG due to trauma relevant to their cause of spinal cord tract injury

Weyl corrections to holographic conductivity

For conformal field theories which admit a dual gravitational description in anti-de Sitter space, electrical transport properties, such as conductivity and charge diffusion, are determined by the dynamics of a U(1) gauge field in the bulk and thus obey universality relations at the classical level due to the uniqueness of the Maxwell action. We analyze corrections to these transport parameters due to higher-dimension operators in the bulk action, beyond the leading Maxwell term, of which the most significant involves a coupling to the bulk Weyl tensor. We show that the ensuing corrections to conductivity and the diffusion constant break the universal relation with the U(1) central charge observed at leading order, but are nonetheless subject to interesting bounds associated with causality in the boundary CFT.Comment: 15 pages, v2: references adde

Type I singularities and the Phantom Menace

We consider the future dynamics of a transient phantom dominated phase of the universe in LQC and in the RS braneworld, which both have a non-standard Friedmann equation. We find that for a certain class of potentials, the Hubble parameter oscillates with simple harmonic motion in the LQC case and therefore avoids any future singularity. For more general potentials we find that damping effects eventually lead to the Hubble parameter becoming constant. On the other hand in the braneworld case we find that although the type I singularity can be avoided, the scale factor still diverges at late times.Comment: More references added. Final PRD versio

Vegetation history of Laysan Island, Northwestern Hawaiian Islands

Paleoenvironmental investigations were undertaken on Laysan Island in the remote Northwestern Hawaiian Islands to investigate its flora before historical observations. Substantial impacts occurred to the island as a result of late nineteenth- and early twentieth-century guano mining, commercial feather collecting, and denudation of vegetation by feral rabbits. An account of Laysan's historically known vegetation is presented, followed by discussion of results from the investigation of a 16.41-m sediment core froin Laysan's central hypersaline lake. The 7,000-year pollen and seed record, besides indicating the former importance of Pritchardia palms on Laysan, showed the former presence of Seven Previously unkown taxa, only four of which could be identified. Diatom analysis indicated fresh to brackish lake water during the early Holocene, a finding supported by the mollusk assemblage. Diatom diversity gradually decreased over time until there is a near monoculture, with types indicating a gradual increase of salinity. Hypersaline conditions were first recognizable near the top of the sequence with the appearance of Artemia zooplankton. Generally wetter Conditions Seem to have characterized the island before about 5,150 yr B.P., with drier conditions thereafter. The pollen record also suggests two possibly very brief periods of much drier conditions, conceivably related to El Nino-Southern Oscillation episodes

The Exclusion of Restrictive Lung Disease by Spirometric Criteria in Patients with a Reduced Forced Vital Capacity

Reductions in forced vital capacity (EVC) as determined by spirometry may result from restrictive or obstructive disease, either alone or in combination. Restrictive disease is implied when measures of forced expiratory flow are relatively maintained, and obstructive disease is present when flow measurements are disproportionately reduced. In the presence of air flow obstruction, the possibility of concomitant restrictive disease contributing to the reduction in FVC is difficult to assess from spirometry alone. Static lung volumes are usually necessary to establish this diagnosis. We evaluated the FEV1/EVC%o obtained at spirometry compared to its predicted normal value. We found it to be useful in eliminating the need for additional testing in many cases in which the question of mixed obstructive and restrictive disease had been raised. Specifically, in patients with obstructive disease and a reduced FVC, an FEV1/FVC% of less than 81%, of the age-, height-, and sex-matched predicted value largely excluded the possibility that concomitant restrictive disease was also present (p\u3c.05). Higher values had no predictive value

Proposal for a low cost close air support aircraft for the year 2000: The Raptor

The Raptor is a proposed low cost Close Air Support (CAS) aircraft for the U.S. Military. The Raptor incorporates a 'cranked arrow' wing planform, and uses canards instead of a traditional horizontal tail. The Raptor is designed to be capable of responsive delivery of effective ordnance in close proximity to friendly ground forces during the day, night, and 'under the weather' conditions. Details are presented of the Raptor's mission, configuration, performance, stability and control, ground support, manufacturing, and overall cost to permit engineering evaluation of the proposed design. A description of the design process and analysis methods used is also provided