4,576 research outputs found
The Effects of Age on Gait and Functional Movement Characteristics in an Older Adult Population
The maintenance of function in an ageing population is essential to ensure current and future health in older people. The ability to walk independently in a range of situations and environments is key to successful ageing. Age-related gait adaptations including spatial-temporal parameters, joint kinematics and kinetics have been identified to be a consequence of the ageing process. For example, reduced walking speed and increased pelvic tilt are suggestive of compensation strategies to minimise falls. The majority of research has compared young adults (20-40 yrs) to older adults (≥ 50 yrs), categorising older adults into a single group regardless of actual age. An alternative approach is to explore the effects of age on gait and functional movement characteristics within an older adult population. One-hundred and fifty-eight community-dwelling older adults, age range 55 to 86 years (65.7 ± 6.8 yrs) were recruited to create a new gait database. Three-dimensional motion analysis captured five walking tasks: normal walking (with and without force plate contact), manual dual task walking and walking with obstacle clearance (stepping onto, off and over an obstacle). Age-related adaptations to walking occurred from age 75 years by adopting a joint kinetic strategy (including reduced hip extension moment) and altering gait (including a reduced walking speed). Increasing the task complexity was associated with altered gait patterns for this older adult group including a reduction in toe-clearance during manual dual task walking (increasing the likelihood of tripping) and increased arm swing during obstacle clearance (potentially increasing stability). This work represents the creation of one of the largest databases of gait in older people including three-dimensional motion analysis for normal walking and three functional walking tasks for healthy high-functioning older adults. It has the potential to be used to identify factors that predispose older adults to falling or with previously unidentified pathological changes
Dark-ages reionization and galaxy formation simulation - IX. Economics of reionizing galaxies
Using a series of high-resolution hydrodynamical simulations we show that
during the rapid growth of high-redshift (z > 5) galaxies, reserves of
molecular gas are consumed over a time-scale of 300Myr, almost independent of
feedback scheme. We find that there exists no such simple relation for the
total gas fractions of these galaxies, with little correlation between gas
fractions and specific star formation rates. The bottleneck or limiting factor
in the growth of early galaxies is in converting infalling gas to cold
star-forming gas. Thus, we find that the majority of high redshift dwarf
galaxies are effectively in recession, with demand (of star formation) never
rising to meet supply (of gas), irrespective of the baryonic feedback physics
modelled. We conclude that the basic assumption of self-regulation in galaxies
- that they can adjust total gas consumption within a Hubble time - does not
apply for the dwarf galaxies thought to be responsible for providing most UV
photons to reionize the high redshift Universe. We demonstrate how this rapid
molecular time-scale improves agreement between semi-analytic model predictions
of the early Universe and observed stellar mass functions.Comment: 17 pages, 27 figures, accepted for publication in MNRAS, minor
updates to align with final published versio
Pure Apraxia of Speech - A Case Report -
Apraxia of speech (AOS) is the impairment of motor programming. However, the exact nature of this deficit remains unclear. In particular, AOS without other speech-language deficit is called pure AOS, but it is very rare. When diagnosing AOS, the characteristic of articulation is considered a crucial criterion, which has been proposed for differentiating AOS from phonological and dysarthric disorders. The present study reports on pure AOS in a 37-year-old right-handed male after a left insular, front, temporal infarction. This report may be useful for further AOS study and diagnosis in the clinical setting
Sensitivity of ultralight axion dark matter search with optical quantum sensors
An optical quantum sensor (OQS) based on lasers and alkali-metal atoms is a
sensitive ambient-temperature magnetometer that can be used in axion dark
matter search with an inductor-capacitor (LC) circuit at kHz and MHz
frequencies. We have previously investigated the sensitivity of an LC
circuit-OQS axion detector to ultralight axion dark matter that could be
achieved using a fT-noise OQS constructed in our lab. In this paper, we
investigate the sensitivity that could be potentially reached by an OQS
performing close to the fundamental quantum noise levels of 10
aT/. To take advantage of the quantum-limited OQS, the LC
circuit has to be made of a superconductor and cooled to low temperature of a
few K. After considering the intrinsic noise of the advanced axion detector and
characterizing possible background noises, we estimate that such an experiment
could probe benchmark QCD axion models in an unexplored mass range near 10 neV.
Reaching such a high sensitivity is a difficult task, so we have conducted some
preliminary experiments with a large-bore magnet and a prototype axion detector
consisting of a room-temperature LC circuit and a commercial OQS unit. This
paper describes the prototype experiment and its projected sensitivity to
axions in detail
Dark-ages reionization and galaxy formation simulation XI: Clustering and halo masses of high redshift galaxies
We investigate the clustering properties of Lyman-break galaxies (LBGs) at
- . Using the semi-analytical model {\scshape Meraxes} constructed
as part of the Dark-ages Reionization And Galaxy-formation Observables from
Numerical Simulation (DRAGONS) project, we predict the angular correlation
function (ACF) of LBGs at - . Overall, we find that the predicted
ACFs are in good agreement with recent measurements at and from observations consisting of the Hubble eXtreme Deep Field (XDF), the
Hubble Ultra-Deep Field (HUDF) and Cosmic Assembly Near-infrared Deep
Extragalactic Legacy Survey (CANDELS) field. We confirm the dependence of
clustering on luminosity, with more massive dark matter haloes hosting brighter
galaxies, remains valid at high redshift. The predicted galaxy bias at fixed
luminosity is found to increase with redshift, in agreement with observations.
We find that LBGs of magnitude at reside in dark matter haloes of mean mass -
, and this dark matter halo mass does not evolve
significantly during reionisation.Comment: 14 pages, 10 figures, published in MNRA
Exploring Minimal Scenarios to Produce Transversely Bright Electron Beams Using the Eigen-Emittance Concept
Next generation hard X-ray free electron lasers require electron beams with
low transverse emittance. One proposal to achieve these low emittances is to
exploit the eigen-emittance values of the beam. The eigen-emittances are
invariant under linear beam transport and equivalent to the emittances in an
uncorrelated beam. If a correlated beam with two small eigen-emittances can be
produced, removal of the correlations via appropriate optics will lead to two
small emittance values, provided non-linear effects are not too large. We study
how such a beam may be produced using minimal linear correlations. We find it
is theoretically possible to produce such a beam, however it may be more
difficult to realize in practice. We identify linear correlations that may lead
to physically realizable emittance schemes and discuss promising future
avenues.Comment: 7 pages, 2 figures, to appear in NIM
Resistant Starches Types 2 and 4 Have Differential Effects on the Composition of the Fecal Microbiota in Human Subjects
BACKGROUND: To systematically develop dietary strategies based on resistant starch (RS) that modulate the human gut microbiome, detailed in vivo studies that evaluate the effects of different forms of RS on the community structure and population dynamics of the gut microbiota are necessary. The aim of the present study was to gain a community wide perspective of the effects of RS types 2 (RS2) and 4 (RS4) on the fecal microbiota in human individuals. METHODS AND FINDINGS: Ten human subjects consumed crackers for three weeks each containing either RS2, RS4, or native starch in a double-blind, crossover design. Multiplex sequencing of 16S rRNA tags revealed that both types of RS induced several significant compositional alterations in the fecal microbial populations, with differential effects on community structure. RS4 but not RS2 induced phylum-level changes, significantly increasing Actinobacteria and Bacteroidetes while decreasing Firmicutes. At the species level, the changes evoked by RS4 were increases in Bifidobacterium adolescentis and Parabacteroides distasonis, while RS2 significantly raised the proportions of Ruminococcus bromii and Eubacterium rectale when compared to RS4. The population shifts caused by RS4 were numerically substantial for several taxa, leading for example, to a ten-fold increase in bifidobacteria in three of the subjects, enriching them to 18-30% of the fecal microbial community. The responses to RS and their magnitudes varied between individuals, and they were reversible and tightly associated with the consumption of RS. CONCLUSION: Our results demonstrate that RS2 and RS4 show functional differences in their effect on human fecal microbiota composition, indicating that the chemical structure of RS determines its accessibility by groups of colonic bacteria. The findings imply that specific bacterial populations could be selectively targeted by well designed functional carbohydrates, but the inter-subject variations in the response to RS indicates that such strategies might benefit from more personalized approaches
Active immunization with myelin-derived altered peptide ligand reduces mechanical pain hypersensitivity following peripheral nerve injury
BACKGROUND: T cells have been implicated in neuropathic pain that is caused by peripheral nerve injury. Immunogenic myelin basic protein (MBP) peptides have been shown to initiate mechanical allodynia in a T cell-dependent manner. Antagonistic altered peptide ligands (APLs) are peptides with substitutions in amino acid residues at T cell receptor contact sites and can inhibit T cell function and modulate inflammatory responses. In the present study, we studied the effects of immunization with MBP-derived APL on pain behavior and neuroinflammation in an animal model of peripheral nerve injury. METHODS: Lewis rats were immunized subcutaneously at the base of the tail with either a weakly encephalitogenic peptide of MBP (cyclo-MBP(87-99)) or APL (cyclo-(87-99)[A(91),A(96)]MBP(87-99)) in complete Freund’s adjuvant (CFA) or CFA only (control), following chronic constriction injury (CCI) of the left sciatic nerve. Pain hypersensitivity was tested by measurements of paw withdrawal threshold to mechanical stimuli, regulatory T cells in spleen and lymph nodes were analyzed by flow cytometry, and immune cell infiltration into the nervous system was assessed by immunohistochemistry (days 10 and 30 post-CCI). Cytokines were measured in serum and nervous tissue of nerve-injured rats (day 10 post-CCI). RESULTS: Rats immunized with the APL cyclo-(87-99)[A(91),A(96)]MBP(87-99) had significantly reduced mechanical pain hypersensitivity in the ipsilateral hindpaw compared to cyclo-MBP(87-99)-treated and control rats. This was associated with significantly decreased infiltration of T cells and ED1+ macrophages in the injured nerve of APL-treated animals. The percentage of anti-inflammatory (M2) macrophages was significantly upregulated in the APL-treated rats on day 30 post-CCI. Compared to the control rats, microglial activation in the ipsilateral lumbar spinal cord was significantly increased in the MBP-treated rats, but was not altered in the rats immunized with the MBP-derived APL. In addition, immunization with the APL significantly increased splenic regulatory T cells. Several cytokines were significantly altered after CCI, but no significant difference was observed between the APL-treated and control rats. CONCLUSIONS: These results suggest that immune deviation by active immunization with a non-encephalitogenic MBP-derived APL mediates an analgesic effect in animals with peripheral nerve injury. Thus, T cell immunomodulation warrants further investigation as a possible therapeutic strategy for the treatment of peripheral neuropathic pain
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