4 research outputs found
Effect of Knee Injury on Foot Load of Rugby Players
Předmětem této práce je statistické vyhodnocení získaných dat pedobarometrického měření a zjištění jejich možné souvislosti s bolestí kolen u hráčů ragby. Nasbíraná data byla hodnocena dle různých kritérií a byly zohledněny výpovědi dotazníků, které zahrnovaly specifika bolesti kolen a úrazovou historii hráčů. Kontrolní soubor představovala zdravá končetina každého hráče, s níž byly výsledky porovnávány. V teoretické části práce se pojednává o základních anatomických, kineziologických a biomechanických aspektech sledovaných kloubů. Tato část práce také ozřejmuje obecnou etiologii zranění kolen a příčinu vzniku úrazů i v ragby, jehož představení náleží prvním stránkám práce. Metodika práce charakterizuje testovaný soubor a jeho sportovní nároky. Specifikuje pravidla a postupy provedeného pedobarometrického měření. Speciální část se věnuje interpretaci zjištěných výsledků a jejich diskuzi. Ze zjištěných hodnot dominuje umístění bodu maximálního tlaku a rozložení předozadního zatížení během chůze i stoje. Bod největšího tlaku náleží bolavé končetině a stejně tak předozadní zatížení je na sledované končetině výraznější na přední části nohy. Diskuze práce hodnotí získané výsledky a porovnává je se zahraničními autory a již proběhlými studiemi.The aim of this thesis is a statistical evaluation of the data gained from a pedobarometrical analysis and discovering their possible connection with knee pain in rugby players. The collected data were evaluated on the basis of various criteria together with the replies to questionnaires which included the specifics of knee pain and the player's injury history. All the results were compared with control samples - the non-injured limb of each player. In the theoretical framework of the thesis I deal with the basic anatomical, kinesiological and biomechanical aspects of the monitored joints. This part also includes clarification of the general etiology of knee injuries and rugby injury causes, as described on the first pages of the thesis. The methodology of work characterises the tested file and its sport demands. It specifies the rules and procedures of the made pedobarometrical measuring. The interpretation of the results and their discussion is analyzed in a special part of the thesis. Plantar peak pressure location and anteroposterior load distribution during walking and standing dominate from all the measured values. Just as the plantar peak pressure appertains to the painful limb, the anteroposterior load distribution is more distinct at the front part of the leg. The obtained results and their comparison with foreign authors and studies are evaluated in the thesis discussion
Shell galaxies as laboratories for testing MOND
Tests of MOND in ellipticals are relatively rare because these galaxies often
lack kinematic tracers in the regions where the MOND effects are significant.
Stellar shells observed in many elliptical galaxies offer a promising way to
constrain their gravitational field. Shells appear as glowing arcs around their
host galaxy. They are observed up to ~100 kpc. The stars in axially symmetric
shell systems move in nearly radial orbits. The radial distributions of shell
locations and the spectra of stars in shells can be used to constrain the
gravitational potential of their host galaxy. The symmetrical shell systems,
being especially suitable for these studies, occur in approximately 3% of all
early-type galaxies. Hence the shells substantially increase the number of
ellipticals in which MOND can be tested up to large radii. In this paper, we
review our work on shell galaxies in MOND. We summarize the paper B\'{i}lek et
al. (2013), where we demonstrated the consistency of shell radii in an
elliptical NGC 3923 with MOND, and the work B\'{i}lek et al. (2014), in which
we predicted a giant (~200 kpc), as yet undiscovered shell of NGC 3923. We
explain the shell identification method, which was used in these two papers. We
further describe the expected shape of line profiles in shell spectra in MOND
which is very special due to the direct relation of the gravitational field and
baryonic matter distribution (B\'{i}lek et al., 2014, in preparation).Comment: 21 pages, 8 figures, 1 table, accepted for publication in the special
MOND issue of the Canadian Journal of Physic
MOND implications for spectral line profiles of shell galaxies: shell formation history and mass-velocity scaling relations
Context. Many ellipticals are surrounded by round stellar shells probably
stemming from minor mergers. A new method for constraining gravitational
potential in elliptical galaxies has recently been suggested. It uses the
spectral line profiles of these shells to measure the circular velocity at the
edge of the shell and the expansion velocity of the shell itself. MOND is an
alternative to the dark matter framework aiming to solve the missing mass
problem.
Aims. We study how the circular and expansion velocities behave in MOND for
large shells.
Methods. The asymptotic behavior for infinitely large shells is derived
analytically. The applicability of the asymptotic results for finitely sized
shells is studied numerically on a grid of galaxies modeled with S\'ersic
spheres.
Results. Circular velocity settles asymptotically at a value determined by
the baryonic mass of the galaxy forming the baryonic Tully-Fisher relation
known for disk galaxies. Shell expansion velocity also becomes asymptotically
constant. The expansion velocities of large shells form a multibranched analogy
to the baryonic Tully-Fisher relation, together with the galactic baryonic
masses. For many - but not all - shell galaxies, the asymptotic values of these
two types of velocities are reached under the effective radius. If MOND is
assumed to work in ellipticals, then the shell spectra allow many details of
the history to be revealed about the formation of the shell system, including
its age. The results pertaining to circular velocities apply to all elliptical
galaxies, not only those with shells.Comment: 8 pages, 7 figures, 1 table, accepted for publication in A&
Deep imaging of the shell elliptical galaxy NGC3923 with MegaCam
Context. The elliptical galaxy NGC 3923 is known to be surrounded by a number
of stellar shells, probable remnants of an accreted galaxy. Despite its
uniqueness, the deepest images of its outskirts come from the 1980s. On the
basis of the modified Newtonian dynamics (MOND), it has recently been predicted
that a new shell lies in this region.
Aims. We obtain the deepest image ever of the galaxy, map the tidal features
in it, and search for the predicted shell.
Methods. The image of the galaxy was taken by the MegaCam camera at the
Canada-France-Hawaii Telescope in the g' band. It reached the
surface-brightness limit of 29 mag/arcsec2. In addition, we reanalyzed an
archival HST image of the galaxy.
Results. We detected up to 42 shells in NGC 3923. This is by far the highest
number among all shell galaxies. We present the description of the shells and
other tidal features in the galaxy. A probable progenitor of some of these
features was discovered. The shell system likely originates from two or more
progenitors. The predicted shell was not detected, but the new image revealed
that the prediction was based on incorrect assumptions and poor data.Comment: 14 pages, 2 tables, 19 figures, accepted for publication in A&