1,074 research outputs found
The ACTN3 Gene and Differences between Playing Positions in Bone Mineral Content, Fat Mass and Lean Tissue Mass in the Arms, Legs and Trunk Of Rugby Union Football Players
Aim: The function of the present study was to identify differences
between individual playing positions in bone mineral content, fat
mass, and lean tissue mass, in the arms, trunk and legs of young adult
Rugby Union football players who carried the ACTN3 gene.
Subjects and methods: A cross-sectional case control study
was carried out using a candidate gene approach (n=55). Individuals
belonged to a homogeneous group of players relative to age, gender,
ability, and ethnicity. Players were allocated to their preferred playing
position. These were the front row (n=14), second and back rows
(n=16), scrum and outside-half (n=11), and centres, wings and fullbacks
(n=14). A 5 ml sample of saliva was obtained from each player
and specimens stored at 4oC until buccal cell DNA extraction was
carried out. Height was measured to the nearest 0.1 cm and body mass
to the closest 0.1 kg. Dual-energy X-ray absorptiometry was measured
using a Hologic QDR Discovery fan beam model. Statistical analyses
were undertaken using ANOVA, ANCOVA and MANOVA.
Results: The study sample comprised 22% RR, 60% RX, and 18%
XX genotypes of the ACTN3 gene respectively. Players in the second
and back rows were significantly taller than other positions. Body
mass differences, were significantly greater in forwards than backs.
There were non-significant differences between positions in adjusted
bone mineral content or adjusted lean tissue mass. Adjusted fat mass
reflected differences between left and right arms, but not left and right
legs.
Conclusion: At a developmental level of performance, an
understanding and practical application of the structural, physiological
and body composition characteristics of individual players, will
facilitate personal and team accomplishment, efficiency of training
and conditioning, and nurture the potential of young adult players
Positive Self-Adjoint Operator Extensions with Applications to Differential Operators
In this paper we consider extensions of positive operators. We study the connections between the von Neumann theory of extensions and characterisations of positive extensions via decompositions of the domain of the associated form. We apply the results to elliptic second-order differential operators and look in particular at examples of the Laplacian on a disc and the Aharanov-Bohm operator
A simple proof of Hardy-Lieb-Thirring inequalities
We give a short and unified proof of Hardy-Lieb-Thirring inequalities for
moments of eigenvalues of fractional Schroedinger operators. The proof covers
the optimal parameter range. It is based on a recent inequality by Solovej,
Soerensen, and Spitzer. Moreover, we prove that any non-magnetic Lieb-Thirring
inequality implies a magnetic Lieb-Thirring inequality (with possibly a larger
constant).Comment: 12 page
Hardy's inequality and curvature
A Hardy inequality of the form \int_{\tilde{\Omega}} |\nabla f({\bf{x}})|^p
d {\bf{x}} \ge (\frac{p-1}{p})^p \int_{\tilde{\Omega}} \{1 + a(\delta, \partial
\tilde{\Omega})(\x)\}\frac{|f({\bf{x}})|^p}{\delta({\bf{x}})^p} d{\bf{x}},
for all , is considered for , where can be either or with a domain in , , and
is the distance from to the
boundary The main emphasis is on determining the
dependance of on the geometric
properties of A Hardy inequality is also
established for any doubly connected domain in in terms
of a uniformisation of that is, any conformal univalent map of
onto an annulus
A nonhomogeneous boundary value problem in mass transfer theory
We prove a uniqueness result of solutions for a system of PDEs of
Monge-Kantorovich type arising in problems of mass transfer theory. The results
are obtained under very mild regularity assumptions both on the reference set
, and on the (possibly asymmetric) norm defined in
. In the special case when is endowed with the Euclidean
metric, our results provide a complete description of the stationary solutions
to the tray table problem in granular matter theory.Comment: 22 pages, 2 figure
Exponential localization of hydrogen-like atoms in relativistic quantum electrodynamics
We consider two different models of a hydrogenic atom in a quantized
electromagnetic field that treat the electron relativistically. The first one
is a no-pair model in the free picture, the second one is given by the
semi-relativistic Pauli-Fierz Hamiltonian. We prove that the no-pair operator
is semi-bounded below and that its spectral subspaces corresponding to energies
below the ionization threshold are exponentially localized. Both results hold
true, for arbitrary values of the fine-structure constant, , and the
ultra-violet cut-off, , and for all nuclear charges less than the
critical charge without radiation field, . We obtain
similar results for the semi-relativistic Pauli-Fierz operator, again for all
values of and and for nuclear charges less than .Comment: 37 page
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