1,961 research outputs found
Letter to the editor concerning the article “Performance of gymnastics skill benefits from an external focus of attention” by Abdollahipour, Wulf, Psotta & Nieto (2015)
Abdollahipour, Wulf, Psotta, & Nieto (2015) recently published data in Journal of Sports Sciences to show that an external focus of attention promotes superior performance effects (gymnastics jump height and judged movement form score) when compared to internal or control foci during skill execution without an implement involved. While we do not contest the veracity of findings reported, nor others that have been used to support beneficial effects of an external focus of attention, in this Letter to the Editor we comment on considerable methodological limitations associated with this and previous studies which, we suggest, have resulted in serious theoretical oversights regarding the control of movement and, most crucially from our practitioner perspective, suboptimal recommendations for applied coaching practice. Specifically, we discuss the lack of consideration towards translational research in this area, the problematic nature of attentional focus cues employed, interpretation of findings in relation to other applied recommendations and coherence with mechanistic underpinning and finally, the representative nature of task involved. In summary, while (laboratory) research evidence may appear to be conclusive, we suggest that focus of attention effects are in need of more ecologically valid and rigorous testing and consideration of current coaching practices if it is to optimally serve the applied sporting domain that it purportedly aims to
Anomalous Elasticity of Polymer Cholesterics
We show that polymer cholesterics have much longer pitches than comparable
short molecule cholesterics, due to their anomalous elasticity. The pitch
of a chiral mixture with concentration near the racemic (non-chiral)
concentration diverges like with (for short molecule cholesterics ). The short molecule law is
recovered for polymers of finite molecular length once the pitch is
longer than a length that diverges like with . Our predictions could be tested by measurements of the pitch in DNA.Comment: 12 pages, Plain TeX, (1 postscript figure, compressed, uuencoded and
appended to paper), minor corrections, IASSNS-HEP-94/4
A New Phase of Tethered Membranes: Tubules
We show that fluctuating tethered membranes with {\it any} intrinsic
anisotropy unavoidably exhibit a new phase between the previously predicted
``flat'' and ``crumpled'' phases, in high spatial dimensions where the
crumpled phase exists. In this new "tubule" phase, the membrane is crumpled in
one direction but extended nearly straight in the other. Its average thickness
is with the intrinsic size of the membrane. This phase
is more likely to persist down to than the crumpled phase. In Flory
theory, the universal exponent , which we conjecture is an exact
result. We study the elasticity and fluctuations of the tubule state, and the
transitions into it.Comment: 4 pages, self-unpacking uuencoded compressed postscript file with
figures already inside text; unpacking instructions are at the top of file.
To appear in Phys. Rev. Lett. November (1995
The Fast Wandering of Slow Birds
I study a single "slow" bird moving with a flock of birds of a different, and
faster (or slower) species. I find that every "species" of flocker has a
characteristic speed , where is the mean speed of the
flock, such that, if the speed of the "slow" bird equals , it
will randomly wander transverse to the mean direction of flock motion far
faster than the other birds will: its mean-squared transverse displacement will
grow in with time like , in contrast to for the
other birds. In , the slow bird's mean squared transverse displacement
grows like , in contrast to for the other birds. If , the mean-squared displacement of the "slow" bird crosses over from
to scaling in , and from to scaling in
, at a time that scales according to .Comment: 10 pages; 5 pages of which did not appear in earlier versions, but
were added in response to referee's suggestion
Alien Registration- Toner, Murnie J. (Bingham, Somerset County)
https://digitalmaine.com/alien_docs/8592/thumbnail.jp
Flocking Regimes in a Simple Lattice Model
We study a one-dimensional lattice flocking model incorporating all three of
the flocking criteria proposed by Reynolds [Computer Graphics vol.21 4 (1987)]:
alignment, centring and separation. The model generalises that introduced by O.
J. O' Loan and M. R. Evans [J. Phys. A. vol. 32 L99 (1999)]. We motivate the
dynamical rules by microscopic sampling considerations. The model exhibits
various flocking regimes: the alternating flock, the homogeneous flock and
dipole structures. We investigate these regimes numerically and within a
continuum mean-field theory.Comment: 24 pages 7 figure
Minimal model for active nematics: quasi-long-range order and giant fluctuations
We propose a minimal microscopic model for active nematic particles similar
in spirit to the Vicsek model for self-propelled polar particles. In two
dimensions, we show that this model exhibits a Kosterlitz-Thouless-like
transition to quasi-long-range orientational order and that in this
non-equilibrium context, the ordered phase is characterized by giant density
fluctuations, in agreement with the predictions of Ramaswamy {\it et al.}
[Europhys. Lett. {\bf 62}, 196 (2003)].Comment: Submitted to Phys. Rev. Lett. 4 pages, 4 figure
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