1,971 research outputs found
A technique to record the sedentary to walk movement during free living mobility : a comparison of healthy and stroke populations
Background
Hesitation between moving from a sedentary posture (lying/sitting) to walking is a characteristic of
mobility impaired individuals, as identified from laboratory studies. Knowing the extent to which this
hesitation occurs during everyday life would benefit rehabilitation research. This study aimed to
quantify this transition hesitation through a novel approach to analysing data from a physical activity
monitor based on a tri-axial accelerometer and compare results from two populations; stroke
patients and age-matched unimpaired controls.
Methods
Stroke patients living at home with early supported discharge (n=34, 68.9YO ± 11.8) and age matched
controls (n=30, 66.8YO ± 10.5) wore a physical activity monitor for 48hrs. The outputs from
the monitor were then used to determine the transitions from sedentary to walking. The time delay
between a sedentary posture ending and the start of walking classified four transition types: 1)
fluent (<=2s), 2) hesitant (>2s<=10s), 3) separated (>10s) and 4) a change from sedentary with no
registered walking to a return to sedentary.
Results
Control participants initiated walking after a sedentary posture on 92% of occasions. Most
commonly (43%) this was a fluent transition. In contrast stroke patients walked after changing from
a sedentary posture on 68% of occasions with only 9% of transitions classed as fluent, (p<0.05).
Discussion/Conclusion
A new data analysis technique reports the frequency of walking following a change in sedentary
position in stroke patients and healthy controls and characterises this transition according to the
time delay before walking. This technique creates opportunities to explore everyday mobility in
greater depth
A Powerful AGN Outburst in RBS 797
Utilizing ks of Chandra X-ray Observatory imaging, we present an
analysis of the intracluster medium (ICM) and cavity system in the galaxy
cluster RBS 797. In addition to the two previously known cavities in the
cluster core, the new and deeper X-ray image has revealed additional structure
associated with the active galactic nucleus (AGN). The surface brightness
decrements of the two cavities are unusually large, and are consistent with
elongated cavities lying close to our line-of-sight. We estimate a total AGN
outburst energy and mean jet power of erg and
erg s, respectively, depending on the
assumed geometrical configuration of the cavities. Thus, RBS 797 is apparently
among the the most powerful AGN outbursts known in a cluster. The average mass
accretion rate needed to power the AGN by accretion alone is
yr. We show that accretion of cold gas onto the AGN at this level is
plausible, but that Bondi accretion of the hot atmosphere is probably not. The
BCG harbors an unresolved, non-thermal nuclear X-ray source with a bolometric
luminosity of erg s. The nuclear emission is
probably associated with a rapidly-accreting, radiatively inefficient accretion
flow. We present tentative evidence that star formation in the BCG is being
triggered by the radio jets and suggest that the cavities may be driving weak
shocks () into the ICM, similar to the process in the galaxy
cluster MS 0735.6+7421.Comment: Accepted to ApJ; 20 pages, 11 low-resolution figure
Exploring Zeptosecond Quantum Equilibration Dynamics: From Deep-Inelastic to Fusion-Fission Outcomes in Ni+Ni Reactions
Energy dissipative processes play a key role in how quantum many-body systems
dynamically evolve towards equilibrium. In closed quantum systems, such
processes are attributed to the transfer of energy from collective motion to
single-particle degrees of freedom; however, the quantum many-body dynamics of
this evolutionary process are poorly understood. To explore energy dissipative
phenomena and equilibration dynamics in one such system, an experimental
investigation of deep-inelastic and fusion-fission outcomes in the
Ni+Ni reaction has been carried out. Experimental outcomes have
been compared to theoretical predictions using Time Dependent Hartree Fock and
Time Dependent Random Phase Approximation approaches, which respectively
incorporate one-body energy dissipation and fluctuations. Excellent
quantitative agreement has been found between experiment and calculations,
indicating that microscopic models incorporating one-body dissipation and
fluctuations provide a potential tool for exploring dissipation in low-energy
heavy ion collisions.Comment: 11 pages, 9 figures, 1 table, including Supplemental Material -
Version accepted for publication in Physical Review Letter
Reduced quasifission competition in fusion reactions forming neutron-rich heavy elements
Measurements of mass-angle distributions (MADs) for Cr + W reactions,
providing a wide range in the neutron-to-proton ratio of the compound system,
(N/Z)CN, have allowed for the dependence of quasifission on the (N/Z)CN to be
determined in a model-independent way. Previous experimental and theoretical
studies had produced conflicting conclusions. The experimental MADs reveal an
increase in contact time and mass evolution of the quasifission fragments with
increasing (N/Z)CN, which is indicative of an increase in the fusion
probability. The experimental results are in agreement with microscopic
time-dependent Hartree-Fock calculations of the quasifission process. The
experimental and theoretical results favor the use of the most neutron-rich
projectiles and targets for the production of heavy and superheavy nuclei.Comment: Accepted to PRC as a Rapid Communicatio
Calibrating the relation of low-frequency radio continuum to star formation rate at 1 kpc scale with LOFAR
9 figures, 6 tables and 17 pages. This paper is part of the LOFAR surveys data release 1 and has been accepted for publication in a special edition of A&A that will appear in Feb 2019, volume 622. The catalogues and images from the data release will be publicly available on lofar-surveys.org upon publication of the journal. Reproduced with permission from Astronomy & Astrophysics. © 2018 ESO.Radio continuum (RC) emission in galaxies allows us to measure star formation rates (SFRs) unaffected by extinction due to dust, of which the low-frequency part is uncontaminated from thermal (free-free) emission. We calibrate the conversion from the spatially resolved 140 MHz RC emission to the SFR surface density () at 1 kpc scale. We used recent observations of three galaxies (NGC 3184, 4736, and 5055) from the LOFAR Two-metre Sky Survey (LoTSS), and archival LOw-Frequency ARray (LOFAR) data of NGC 5194. Maps were created with the facet calibration technique and converted to radio maps using the Condon relation. We compared these maps with hybrid maps from a combination of GALEX far-ultraviolet and Spitzer 24 data using plots tracing the relation at -kpc resolution. The RC emission is smoothed with respect to the hybrid owing to the transport of cosmic-ray electrons (CREs). This results in a sublinear relation , where (140 MHz) and (1365 MHz). Both relations have a scatter of . If we restrict ourselves to areas of young CREs (; ), the relation becomes almost linear at both frequencies with and a reduced scatter of . We then simulate the effect of CRE transport by convolving the hybrid maps with a Gaussian kernel until the RC-SFR relation is linearised; CRE transport lengths are -5 kpc. Solving the CRE diffusion equation, we find diffusion coefficients of - at 1 GeV. A RC-SFR relation at GHz can be exploited to measure SFRs at redshift using MHz observations.Peer reviewe
B-Vitamins and fatty acids in the prevention and treatment of Alzheimer's disease and dementia: A systematic review
The increasing worldwide prevalence of dementia is a major public health concern. Findings from some epidemiological studies suggest that diet and nutrition may be important modifiable risk factors for development of dementia. In order to evaluate the strength of the available evidence of an association of dietary factors with dementia including Alzheimer's disease (AD), we systematically searched relevant publication databases and hand-searched bibliographies up to end July 2007. We included prospective cohort studies which evaluated the association of nutrient levels with the risk of developing dementia and randomized intervention studies examining the treatment effect of nutrient supplementation on cognitive function. One hundred and sixty studies, comprising ninety one prospective cohort studies and sixty nine intervention studies, met the pre-specified inclusion criteria. Of these, thirty-three studies (19 cohort and 14 randomized controlled trials) investigated the effects of folate, B-vitamins, and levels of homocysteine (a biomarker modifiable through B-vitamin supplementation) or fish/fatty acids and are the focus of the present report. Some observational cohort studies indicated that higher dietary intake or elevated serum levels of folate and fish/fatty acids and low serum levels of homocysteine were associated with a reduced risk of incident AD and dementia, while other studies reported no association. The results of intervention studies examining the effects of folic acid or fatty acid supplementation on cognitive function are inconsistent. In summary, the available evidence is insufficient to draw definitive conclusions on the association of B vitamins and fatty acids with cognitive decline or dementia, and further long-term trials are required
Detecting Star Formation in Brightest Cluster Galaxies with GALEX
We present the results of GALEX observations of 17 cool core (CC) clusters of
galaxies. We show that GALEX is easily capable of detecting star formation in
brightest cluster galaxies (BCGs) out to and 50-100 kpc. In most of
the CC clusters studied, we find significant UV luminosity excesses and colors
that strongly suggest recent and/or current star formation. The BCGs are found
to have blue UV colors in the center that become increasingly redder with
radius, indicating that the UV signature of star formation is most easily
detected in the central regions. Our findings show good agreement between UV
star formation rates and estimates based on H observations. IR
observations coupled with our data indicate moderate-to-high dust attenuation.
Comparisons between our UV results and the X-ray properties of our sample
suggest clear correlations between UV excess, cluster entropy, and central
cooling time, confirming that the star formation is directly and
incontrovertibly related to the cooling gas.Comment: 39 pages, 11 figures; accepted for publication in The Astrophysical
Journal. Figure quality reduced to comply with arXiv file size requirement
Holographic Roberge-Weiss Transitions
We investigate N=4 SYM coupled to fundamental flavours at nonzero imaginary
quark chemical potential in the strong coupling and large N limit, using
gauge/gravity duality applied to the D3-D7 system, treating flavours in the
probe approximation. The interplay between Z(N) symmetry and the imaginary
chemical potential yields a series of first-order Roberge-Weiss transitions. An
additional thermal transition separates phases where quarks are bound/unbound
into mesons. This results in a set of Roberge-Weiss endpoints: we establish
that these are triple points, determine the Roberge-Weiss temperature, give the
curvature of the phase boundaries and confirm that the theory is analytic in
mu^2 when mu^2~0.Comment: 37 pages, 13 figures; minor comments added, to appear in JHE
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