485 research outputs found
Impaired limb shortening following stroke: what's in a name?
BackgroundDifficulty advancing the paretic limb during the swing phase of gait is a prominent manifestation of walking dysfunction following stroke. This clinically observable sign, frequently referred to as 'foot drop', ostensibly results from dorsiflexor weakness.ObjectiveHere we investigated the extent to which hip, knee, and ankle motions contribute to impaired paretic limb advancement. We hypothesized that neither: 1) minimal toe clearance and maximal limb shortening during swing nor, 2) the pattern of multiple joint contributions to toe clearance and limb shortening would differ between post-stroke and non-disabled control groups.MethodsWe studied 16 individuals post-stroke during overground walking at self-selected speed and nine non-disabled controls who walked at matched speeds using 3D motion analysis.ResultsNo differences were detected with respect to the ankle dorsiflexion contribution to toe clearance post-stroke. Rather, hip flexion had a greater relative influence, while the knee flexion influence on producing toe clearance was reduced.ConclusionsSimilarity in the ankle dorsiflexion, but differences in the hip and knee, contributions to toe clearance between groups argues strongly against dorsiflexion dysfunction as the fundamental impairment of limb advancement post-stroke. Marked reversal in the roles of hip and knee flexion indicates disruption of inter-joint coordination, which most likely results from impairment of the dynamic contribution to knee flexion by the gastrocnemius muscle in preparation for swing. These findings suggest the need to reconsider the notion of foot drop in persons post-stroke. Redirecting the focus of rehabilitation and restoration of hemiparetic walking dysfunction appropriately, towards contributory neuromechanical impairments, will improve outcomes and reduce disability
Optical excitation of nonlinear spin waves
We demonstrate a technique for exciting spin waves in an ultracold gas of
Rb-87 atoms based on tunable AC Stark potentials. This technique allows us to
excite normal modes of spin waves with arbitrary amplitudes in the trapped gas,
including dipole, quadrupole, octupole, and hexadecapole modes. These modes
exhibit strong nonlinearities, which manifest as amplitude dependence of the
excitation frequencies and departure from sinusoidal behavior. Our results are
in good agreement with a full treatment of a quantum Boltzmann transport
equation.Comment: 11 pages, 5 figure
Holographic gauge mediation via strongly coupled messengers
We consider a relative of semi-direct gauge mediation where the hidden sector
exists at large 't Hooft coupling. Such scenarios can be difficult to describe
using perturbative field theory methods but may fall into the class of
holographic gauge mediation scenarios, meaning that they are amenable to the
techniques of gauge/gravity duality. We use a recently found gravity solution
to examine one such case where the hidden sector is a cascading gauge theory
resulting in a confinement scale not much smaller than the messenger mass. In
the original construction of holographic gauge mediation, as in other examples
of semi-direct gauge mediation at strong coupling, the primary contributions to
visible sector soft terms come from weakly coupled messenger mesons. In
contrast to these examples, we describe the dual of a gauge theory where there
are significant contributions from scales where the strongly coupled messenger
quarks are the effective degrees of freedom. In this regime, the visible sector
gaugino mass can be calculated entirely from holography.Comment: 42 pages, 3 figures, references added, typos and minor errors
correcete
Decoherence-driven Cooling of a Degenerate Spinor Bose Gas
We investigate the relationship between the coherence of a partially
Bose-condensed spinor gas and its temperature. We observe cooling of the normal
component driven by decoherence as well the effect of temperature on
decoherence rates.Comment: 4 pages, 2 figure
The Mystery of the Ramsey Fringe that Didn't Chirp
We use precision microwave spectroscopy of magnetically trapped, ultra-cold
87Rb to characterize intra- and inter-state density correlations. The cold
collision shifts for both normal and condensed clouds are measured. The results
verify the presence of the sometimes controversial "factors of two", in
normal-cloud mean-field energies, both within a particular state and between
two distinct spin species. One might expect that as two spin species decohere,
the inter-state factor of two would revert to unity, but the associated
frequency chirp one naively expects from such a trend is not observed in our
data.Comment: Proceedings of the 18th International Conference on Atomic Physics
(ICAP 2002
Thermally Induced Losses in Ultra-Cold Atoms Magnetically Trapped Near Room-Temperature Surfaces
We have measured magnetic trap lifetimes of ultra-cold Rb87 atoms at
distances of 5-1000 microns from surfaces of conducting metals with varying
resistivity. Good agreement is found with a theoretical model for losses
arising from near-field magnetic thermal noise, confirming the complications
associated with holding trapped atoms close to conducting surfaces. A
dielectric surface (silicon) was found in contrast to be so benign that we are
able to evaporatively cool atoms to a Bose-Einstein condensate by using the
surface to selectively adsorb higher energy atoms.Comment: Improved theory curve eliminates discrepancy. JLTP in pres
Does inhibitory repetitive transcranial magnetic stimulation augment functional task practice to improve arm recovery in chronic stroke?
Introduction. Restoration of upper extremity (UE) functional use remains a challenge for individuals following stroke. Repetitive transcranial magnetic stimulation (rTMS) is a noninvasive modality that modulates cortical excitability and is being explored as a means to potentially ameliorate these deficits. The purpose of this study was to evaluate, in the presence of chronic stroke, the effects of low-frequency rTMS to the contralesional hemisphere as an adjuvant to functional task practice (FTP), to improve UE functional ability. Methods. Twenty-two individuals with chronic stroke and subsequent moderate UE deficits were randomized to receive 16 sessions (4 times/week for 4 weeks) of either real-rTMS or sham-rTMS followed by 1-hour of paretic UE FTP. Results. No differences in UE outcomes were revealed between the real-rTMS and sham-rTMS intervention groups. After adjusting for baseline differences, no differences were revealed in contralesional cortical excitability postintervention. In a secondary analysis, data pooled across both groups revealed small, but statistically significant, improvements in UE behavioral measures. Conclusions. rTMS did not augment changes in UE motor ability in this population of individuals with chronic stroke. The chronicity of our participant cohort and their degree of UE motor impairment may have contributed to inability to produce marked effects using rTMS
TLR2 and TLR4 in Ischemia Reperfusion Injury
Ischemia reperfusion (I/R) injury refers to the tissue damage which occurs when blood supply returns to tissue after a period of ischemia and is associated with trauma, stroke, myocardial infarction, and solid organ transplantation. Although the cause of this injury is multifactorial, increasing experimental evidence suggests an important role for the innate immune system in initiating the inflammatory cascade leading to detrimental/deleterious changes. The Toll-like Receptors (TLRs) play a central role in innate immunity recognising both pathogen- and damage-associated molecular patterns and have been implicated in a range of inflammatory and autoimmune diseases. In this paper, we summarise the current state of knowledge linking TLR2 and TLR4 to I/R injury, including recent studies which demonstrate that therapeutic inhibition of TLR2 has beneficial effects on I/R injury in a murine model of myocardial infarction
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