941,615 research outputs found
The multi-functional foot in athletic movement: Extraordinary feats by our extraordinary feet
The unique architecture of the foot system provides a sensitive, multi-tensional method of communicating with the surrounding
environment. Within the premise of the paper, we discuss three themes: complexity, degeneracy and bio-tensegrity. Complex
structures within the foot allow the human movement system to negotiate strategies for dynamic movement during athletic
endeavours. We discuss such complex structures with particular attention to properties of a bio-tensegrity system. Degeneracy
within the foot structure offers a distinctive solution to the problems posed by differing terrains and uneven surfaces allowing
lower extremity structures to overcome perturbation as and when it occurs. This extraordinary structure offers a significant
contribution to bipedalism through presenting a robust base of support and as such, should be given more consideration when
designing athletic development programmes
Ordinary and Extraordinary Hadrons
Resonances and enhancements in meson-meson scattering can be divided into two
classes distinguished by their behavior as the number of colors N_c in QCD
becomes large: The first are ordinary mesons that become stable as N_c goes to
infinity. This class includes textbook q-bar q mesons as well as glueballs and
hybrids. The second class, extraordinary mesons, are enhancements that
disappear as N_c goes to infinity; they subside into the hadronic continuum.
This class includes indistinct and controversial objects that have been
classified as q-bar q-bar q q mesons or meson-meson molecules. Pelaez's study
of the N_c dependence of unitarized chiral dynamics illustrates both classes:
the p-wave pi-pi and K-pi resonances, the rho(770) and K*(892), behave as
ordinary mesons; the s-wave pi-pi and K-pi enhancements, the sigma(600) and
kappa(800), behave like extraordinary mesons. Ordinary mesons resemble Feshbach
resonances while extraordinary mesons look more like effects due to potentials
in meson-meson scattering channels. I build and explore toy models along these
lines. Finally I discuss some related dynamical issues affecting the
interpretation of extraordinary mesons.Comment: 18 pages, 10 figures, talk presented at the 2006 Yukawa International
Seminar: New Frontiers in QCD, Kyoto University, November 2006. This talk is
dedicated to the memory of R. H. Dalit
Extraordinary vacuum black string solutions
In addition to the boosted static solution there are two other classes of
stationary string-like solutions of the vacuum Einstein equation in
(4+1)-dimensions. Each class is characterized by three parameters of mass,
tension, and momentum flow along the fifth coordinate. We analyze the metric
properties of one of the two classes, which was previously assumed to be naked
singular, and show that the solution spectrum contains black string and
wormhole in addition to the known naked singularity as the momentum flow to
mass ratio increases. Interestingly, there does not exist new zero momentum
solution in these cases.Comment: 20 pages, 4 figures, add 2 reference
Double grating formation in anisotropic photorefractive crystals
Double gratings form in anisotropic photorefractive crystals when two plane waves intersecting inside the crystal have both extraordinary and ordinary wave components. The effect can be observed by reading out the two gratings with extraordinary or ordinary light. Experiments confirm the theoretical predictions. The relevance of these results in using photorefractive crystals for holographic storage is discussed
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