3,904 research outputs found
Acute Effects of Exercise on Cognitive Performances of Older Adults
Accelerating rates of structural decline become evident during the third and fourth decades of human life, with disproportionate degeneration occurring in the frontal, parietal, and temporal brain lobes. As the structure of the brain declines, a broad array of cognitive processes involving memory, decision making, and selective attention are reduced as well (Raz 2000, Park et al. 2001). Cardiovascular exercise has been associated with improved cognitive functioning in aging humans, suggesting that increased vascular supply enhances availability of oxygen, nutrients, and other physical entities to nourish the brain. Previous experimentation on older adults revealed significant positive effects of exercise on a variety of memory types following participation in a program six or more months in duration (Colcombe 2003, Kramer et al.1999). The primary focus of this study was to test the effects of acute aerobic exercise on cognitive functioning of adults over the age of 60. A second purpose was to determine that the positive neurological effects of exercise can start taking place immediately. The hypothesis is that memory retention, mental processing speed, and selective attention would acutely improve in the participants after they had exercised, in comparison to their cognitive state prior to exercise. Cognitive performances both before and after exercise were tested using the Stroop test. All participants completed the post-exercise test with improved scores (p=0.000) indicating an increase in cognitive ability, relating exercise and improved cognitive function
Finite volume effects in a quenched lattice-QCD quark propagator
We investigate finite volume effects in the pattern of chiral symmetry
breaking. To this end we employ a formulation of the Schwinger-Dyson equations
on a torus which reproduces results from the corresponding lattice simulations
of staggered quarks and from the overlap action. Studying the volume dependence
of the quark propagator we find quantitative differences with the infinite
volume result at small momenta and small quark masses. We estimate the minimal
box length L below which chiral perturbation theory cannot be applied to be L
\simeq 1.6 fm. In the infinite volume limit we find a chiral condensate of
||_{\bar{MS}}^{2 GeV} = (253 \pm 5.0 MeV)^3, an up/down quark mass of
m_{\bar{MS}}^{2 GeV} = 4.1 \pm 0.3 MeV and a pion decay constant which is only
ten percent smaller than the experimental value.Comment: 19 pages, 8 figures. v2: minor clarifications added, version
published in PR
Quark Condensates: Flavour Dependence
We determine the q-bar q condensate for quark masses from zero up to that of
the strange quark within a phenomenologically successful modelling of continuum
QCD by solving the quark Schwinger-Dyson equation. The existence of multiple
solutions to this equation is the key to an accurate and reliable extraction of
this condensate using the operator product expansion. We explain why
alternative definitions fail to give the physical condensate.Comment: 9 pages, 7 figures, uses appolb.cls, LaTeX. Talk presented by R.
Williams at the EURIDICE Final Meeting, August 24-27th, 2006, Kazimierz,
Polan
The decay of the and resonances in the hidden gauge formalism
Using recent results obtained within the hidden gauge formalism for vector
mesons, in which the and resonances are dynamically
generated resonances from the interaction, we evaluate the
radiative decay of these resonances into . We obtain results for
the width in good agreement with the experimental data for the
state and a width about a factor five smaller for the resonance,
which would agree with preliminary results from the Belle collaboration,
hinting at an order of magnitude smaller width for this resonance than for the
.Comment: 7 pages, 9 figures, proof of gauge invariance adde
Aspects of quark mass generation on a torus
In this talk we report on recent results for the quark propagator on a
compact manifold. The corresponding Dyson-Schwinger equations on a torus are
solved on volumes similar to the ones used in lattice calculations. The
quark-gluon interaction is fixed such that the lattice results are reproduced.
We discuss both the effects in the infinite volume/continuum limit as well as
effects when the volume is small.Comment: 3 pages, 3 figures; talk given by CF at QNP06, Madrid, June 200
Checking the transverse Ward-Takahashi relation at one loop order in 4-dimensions
Some time ago Takahashi derived so called {\it transverse} relations relating
Green's functions of different orders to complement the well-known
Ward-Green-Takahashi identities of gauge theories by considering wedge rather
than inner products. These transverse relations have the potential to determine
the full fermion-boson vertex in terms of the renormalization functions of the
fermion propagator. He & Yu have given an indicative proof at one-loop level in
4-dimensions. However, their construct involves the 4th rank Levi-Civita tensor
defined only unambiguously in 4-dimensions exactly where the loop integrals
diverge. Consequently, here we explicitly check the proposed transverse
Ward-Takahashi relation holds at one loop order in -dimensions, with
.Comment: 20 pages, 3 figures This version corrects and clarifies the previous
result. This version has been submitted for publicatio
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