25 research outputs found
UK cost-effectiveness analysis of endoscopic sleeve gastroplasty versus lifestyle modification alone for adults with class II obesity
The Confrontation between General Relativity and Experiment
The status of experimental tests of general relativity and of theoretical
frameworks for analysing them are reviewed. Einstein's equivalence principle
(EEP) is well supported by experiments such as the E\"otv\"os experiment, tests
of special relativity, and the gravitational redshift experiment. Future tests
of EEP and of the inverse square law will search for new interactions arising
from unification or quantum gravity. Tests of general relativity at the
post-Newtonian level have reached high precision, including the light
deflection, the Shapiro time delay, the perihelion advance of Mercury, and the
Nordtvedt effect in lunar motion. Gravitational wave damping has been detected
to half a percent using the binary pulsar, and new binary pulsar systems may
yield further improvements. When direct observation of gravitational radiation
from astrophysical sources begins, new tests of general relativity will be
possible.Comment: 103 pages, 10 figures, accepted for publication in Living Reviews in
Relativit
Implications upon theory discrimination of an accurate measurement of the time rate of change of the gravitational parameter and other cosmological parameters
A substantial improvement in the accuracy of G-dot tests (The dot denotes the
time derivative.) would make it realistic to speak in terms of a measurement of
G-dot, rather than merely a smaller upper bound on |G-dot|. We show that the
accuracy delta|G-dot/G| \approx 10^-14 yr^-1 may be sufficient, given the
accuracy of other cosmological parameters, to observe effects predicted by
higher dimensions theories and, hence, to discriminate among different models.
The \.G design goal for the SEE (Satellite Energy Exchange) mission is
delta(G-dot/G) \approx 10^-14 yr^-1.Comment: 17 pages, 3 figures Version 2 is revised as per editorial/referee
comment
The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: measurements of the growth of structure and expansion rate at z=0.57 from anisotropic clustering
We analyze the anisotropic clustering of massive galaxies from the Sloan
Digital Sky Survey III Baryon Oscillation Spectroscopic Survey (BOSS) Data
Release 9 (DR9) sample, which consists of 264,283 galaxies in the redshift
range 0.43 < z < 0.7 spanning 3,275 square degrees. Both peculiar velocities
and errors in the assumed redshift-distance relation ("Alcock-Paczynski
effect") generate correlations between clustering amplitude and orientation
with respect to the line-of-sight. Together with the sharp baryon acoustic
oscillation (BAO) standard ruler, our measurements of the broadband shape of
the monopole and quadrupole correlation functions simultaneously constrain the
comoving angular diameter distance (2190 +/- 61 Mpc) to z=0.57, the Hubble
expansion rate at z=0.57 (92.4 +/- 4.5 km/s/Mpc), and the growth rate of
structure at that same redshift (d sigma8/d ln a = 0.43 +/- 0.069). Our
analysis provides the best current direct determination of both DA and H in
galaxy clustering data using this technique. If we further assume a LCDM
expansion history, our growth constraint tightens to d sigma8/d ln a = 0.415
+/- 0.034. In combination with the cosmic microwave background, our
measurements of DA, H, and growth all separately require dark energy at z >
0.57, and when combined imply \Omega_{\Lambda} = 0.74 +/- 0.016, independent of
the Universe's evolution at z<0.57. In our companion paper (Samushia et al.
prep), we explore further cosmological implications of these observations.Comment: 19 pages, 11 figures, submitted to MNRAS, comments welcom
The fundamental constants and their variation: observational status and theoretical motivations
This article describes the various experimental bounds on the variation of
the fundamental constants of nature. After a discussion on the role of
fundamental constants, of their definition and link with metrology, the various
constraints on the variation of the fine structure constant, the gravitational,
weak and strong interactions couplings and the electron to proton mass ratio
are reviewed. This review aims (1) to provide the basics of each measurement,
(2) to show as clearly as possible why it constrains a given constant and (3)
to point out the underlying hypotheses. Such an investigation is of importance
to compare the different results, particularly in view of understanding the
recent claims of the detections of a variation of the fine structure constant
and of the electron to proton mass ratio in quasar absorption spectra. The
theoretical models leading to the prediction of such variation are also
reviewed, including Kaluza-Klein theories, string theories and other
alternative theories and cosmological implications of these results are
discussed. The links with the tests of general relativity are emphasized.Comment: 56 pages, l7 figures, submitted to Rev. Mod. Phy
Bounds on the possible evolution of the Gravitational Constant from Cosmological Type-Ia Supernovae
Recent high-redshift Type Ia supernovae results can be used to set new bounds
on a possible variation of the gravitational constant . If the local value
of at the space-time location of distant supernovae is different, it would
change both the kinetic energy release and the amount of Ni synthesized
in the supernova outburst. Both effects are related to a change in the
Chandrasekhar mass . In addition, the integrated
variation of with time would also affect the cosmic evolution and therefore
the luminosity distance relation. We show that the later effect in the
magnitudes of Type Ia supernovae is typically several times smaller than the
change produced by the corresponding variation of the Chandrasekhar mass. We
investigate in a consistent way how a varying could modify the Hubble
diagram of Type Ia supernovae and how these results can be used to set upper
bounds to a hypothetical variation of . We find G/G_0 \la 1.1 and G'/G
\la 10^{-11} yr^{-1} at redshifts . These new bounds extend the
currently available constrains on the evolution of all the way from solar
and stellar distances to typical scales of Gpc/Gyr, i.e. by more than 15 orders
of magnitudes in time and distance.Comment: 9 pages, 4 figures, Phys. Rev. D. in pres
Galaxy And Mass Assembly (GAMA): Panchromatic Data Release (far-UVâfar-IR) and the low- z
Variability and predictability of elite competitive slalom canoe-kayak performance
Little is known about the race performance characteristics of elite-level slalom canoeists or the magnitude of improvement necessary to enhance medal-winning prospects. Final placing in this sport is determined by the aggregate of semi-final and final run times inclusive of penalty times. We therefore used mixed linear modelling to analyse these times for finalists ranked in the top and bottom half in the men\u27s canoe, men\u27s kayak, and women\u27s kayak boat classes at World Cups, World Championships, and Olympic Games from 2000 to 2007. The run-to-run variability for top-ranked athletes at different courses ranged from 0.8% to 3.2% (90% confidence limits ×/÷1.11-1.31), reflecting differences in how challenging these courses were. The race-to-race variability of aggregate run time was 1.2-2.1% (×/÷~1.09); 0.3 of this variability yields the smallest worthwhile enhancement of 0.4-0.6%. The variabilities of bottom-ranked finalists were approximately double those of top-ranked finalists. The home advantage was small (0.3-0.8%), and incurring a penalty had a marginal effect on reducing actual run time (0.2-0.7%). Correlation coefficients for performance predictability within competitions (0.06-0.35), within years (0.12-0.47), and between years (0.12-0.43) were poor. In conclusion, the variability of performance and smallest worthwhile enhancements in slalom canoe-kayaking are larger than those of comparable sports, and race outcomes are largely unpredictable.<br /
Activity profiles and demands of seasonal and tournament basketball competition
Competition-specific conditioning for tournament basketball games is challenging, as the demands of tournament formats are not well characterized.\ud
\ud
PURPOSE:\ud
\ud
To compare the physical, physiological, and tactical demands of seasonal and tournament basketball competition and determine the pattern of changes within an international tournament.\ud
\ud
METHODS:\ud
\ud
Eight elite junior male basketball players (age 17.8 ± 0.2 y, height 1.93 ± 0.07 m, mass 85 ± 3 kg; mean ± SD) were monitored in 6 seasonal games played over 4 mo in an Australian second-division national league and in 7 games of an international under-18 tournament played over 8 days. Movement patterns and tactical elements were coded from video and heart rates recorded by telemetry.\ud
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RESULTS:\ud
\ud
The frequency of running, sprinting, and shuffling movements in seasonal games was higher than in tournament games by 8-15% (99% confidence limits ± ~8%). Within the tournament, jogging and low- to medium-intensity shuffling decreased by 15-20% (± ~14%) over the 7 games, while running, sprinting, and high-intensity shuffling increased 11-81% (± ~25%). There were unclear differences in mean and peak heart rates. The total number of possessions was higher in seasonal than in tournament games by 8% (± 10%).\ud
\ud
CONCLUSIONS:\ud
\ud
Coaches should consider a stronger emphasis on strength and power training in their conditioning programs to account for the higher activity of seasonal games. For tournament competition, strategies that build a sufficient aerobic capacity and neuromuscular resilience to maintain high-intensity movements need to be employed. A focus on half-court tactics accounts for the lower number of possessions in tournaments
Modelling age and secular differences in fitness between junior basketball players
Concerns about the value of physical testing and apparently declining test performance in junior basketball players prompted this retrospective study of trends in anthropometric and fitness test scores related to recruitment age and recruitment year. Th