181 research outputs found
Physical and performance measures of university cricket players
The ability to throw a ball at high velocity and with great accuracy is critical for successful performance in many ball sports. This study examines the physical characteristics and performance measurements amongst university cricketers. A convenient sample of 40 male cricketers from four teams at the University of the Western Cape was tested. Physical characteristics comprised stature, body mass, skinfold thickness, girth circumferences and limb lengths. Isokinetic strength was measured at 60º•sec-1 and 90º•sec-1using the Biodex Pro System 4 isokinetic dynamometer. Throwing velocity was measured using a calibrated Speed Gun. The fourth team had a significantly shorter arm length than the other teams. Player experience also differed significantly between the first team and the other three teams. Age and body fat percentage correlated significantly with throwing velocity, but in the first team only. Significant correlations were found for the following variables, i.e., between age and strength ratio in the first team; between hip circumference and peak torque during internal rotation at 90º•sec-1 in the second team; between body mass and peak torque during internal rotation at 60º•sec-1 in the third team; between total arm length and peak torque during internal rotation at 60º•sec-1 in the fourth team. In conclusion, this study found that various physical characteristics such as age and body fat percentage significantly influenced throwing velocity, while body mass, hip circumference and total arm length had a significant influence on peak torque.DHE
Topology and correlations in structured scale-free networks
We study a recently introduced class of scale-free networks showing a high
clustering coefficient and non-trivial connectivity correlations. We find that
the connectivity probability distribution strongly depends on the fine details
of the model. We solve exactly the case of low average connectivity, providing
also exact expressions for the clustering and degree correlation functions. The
model also exhibits a lack of small world properties in the whole parameters
range. We discuss the physical properties of these networks in the light of the
present detailed analysis.Comment: 10 pages, 9 figure
Cross-over behaviour in a communication network
We address the problem of message transfer in a communication network. The
network consists of nodes and links, with the nodes lying on a two dimensional
lattice. Each node has connections with its nearest neighbours, whereas some
special nodes, which are designated as hubs, have connections to all the sites
within a certain area of influence. The degree distribution for this network is
bimodal in nature and has finite variance. The distribution of travel times
between two sites situated at a fixed distance on this lattice shows fat
fractal behaviour as a function of hub-density. If extra assortative
connections are now introduced between the hubs so that each hub is connected
to two or three other hubs, the distribution crosses over to power-law
behaviour. Cross-over behaviour is also seen if end-to-end short cuts are
introduced between hubs whose areas of influence overlap, but this is much
milder in nature. In yet another information transmission process, namely, the
spread of infection on the network with assortative connections, we again
observed cross-over behaviour of another type, viz. from one power-law to
another for the threshold values of disease transmission probability. Our
results are relevant for the understanding of the role of network topology in
information spread processes.Comment: 12 figure
Measurement of event shape distributions and moments in e+e- -> hadrons at 91-209 GeV and a determination of alpha_s
We have studied hadronic events from e+e- annihilation data at centre-of-mass
energies from 91 to 209 GeV. We present distributions of event shape
observables and their moments at each energy and compare with QCD Monte Carlo
models. From the event shape distributions we extract the strong coupling
alpha_s and test its evolution with energy scale. The results are consistent
with the running of alpha_s expected from QCD. Combining all data, the value of
alpha_s(M_Z) is determined to be alpha_s(M_Z) = 0.1191 +- 0.0005 (stat.) +-
0.0010 (expt.) +- 0.0011 (hadr.) +- 0.0044 (theo.). The energy evolution of the
moments is also used to determine a value of alpha_s with slightly larger
errors: alpha_s(M_Z) = 0.1223 +- 0.0005 (stat.) +- 0.0014 (expt.) +- 0.0016
(hadr.) +0.0054 -0.0036 (theo.).Comment: 63 pages 26 fi
Flavour Independent hA Search and Two Higgs Doublet Model Interpretation of Neutral Higgs Boson Searches at LEP
Upper limits on the cross-section of the pair-production process e+e- -> h0A0
assuming 100% decays into hadrons, are derived from a new search for the h0A0
-> hadrons topology, independent of the hadronic flavour of the decay products.
Searches for the neutral Higgs bosons h0 and A0, are used to obtain constraints
on the Type II Two Higgs Doublet Model (2HDM(11)) with no CP violation in the
Higgs sector and no additional non Standard Model particles besides the five
Higgs bosons. The analysis combines LEP1 and LEP2 data collected with the OPAL
detctor up to the highest available centre-of-mass energies. The searches are
sensitive to the h0, A0 -> qq, gg,tau+tau- and h0 -> A0A0 decay modes of the
Higgs bosons. The 2HDM(II) parameter space is explored in a detailed scan.
Large regions of the 2HDM(II) parameter space are excluded at the 95% CL in the
(mh, mA), (mh, tanb) and (mA, tanb) planes, using both direct neutral Higgs
boson searches and indirect limits derived from Standard Model high precision
measurements. The region 1 lesssim mh lesssim 55 GeV and 3 lesssim mA lesssim
63 GeV is excluded at 95% CL independently of the choice of the 2HDM(II)
parameters.Comment: 37 pages, 11 figures, Submitted to Eur. Phys. J.
A measurement of the tau mass and the first CPT test with tau leptons
We measure the mass of the tau lepton to be 1775.1+-1.6(stat)+-1.0(syst.) MeV
using tau pairs from Z0 decays. To test CPT invariance we compare the masses of
the positively and negatively charged tau leptons. The relative mass difference
is found to be smaller than 3.0 10^-3 at the 90% confidence level.Comment: 10 pages, 4 figures, Submitted to Phys. Letts.
First Measurement of Z/gamma* Production in Compton Scattering of Quasi-real Photons
We report the first observation of Z/gamma* production in Compton scattering
of quasi-real photons. This is a subprocess of the reaction e+e- to
e+e-Z/gamma*, where one of the final state electrons is undetected.
Approximately 55 pb-1 of data collected in the year 1997 at an e+e-
centre-of-mass energy of 183 GeV with the OPAL detector at LEP have been
analysed. The Z/gamma* from Compton scattering has been detected in the
hadronic decay channel. Within well defined kinematic bounds, we measure the
product of cross-section and Z/gamma* branching ratio to hadrons to be
(0.9+-0.3+-0.1) pb for events with a hadronic mass larger than 60 GeV,
dominated by (e)eZ production. In the hadronic mass region between 5 GeV and 60
GeV, dominated by (e)egamma* production, this product is found to be
(4.1+-1.6+-0.6) pb. Our results agree with the predictions of two Monte Carlo
event generators, grc4f and PYTHIA.Comment: 18 pages, LaTeX, 5 eps figures included, submitted to Physics Letters
Measurement of the B0 Lifetime and Oscillation Frequency using B0->D*+l-v decays
The lifetime and oscillation frequency of the B0 meson has been measured
using B0->D*+l-v decays recorded on the Z0 peak with the OPAL detector at LEP.
The D*+ -> D0pi+ decays were reconstructed using an inclusive technique and the
production flavour of the B0 mesons was determined using a combination of tags
from the rest of the event. The results t_B0 = 1.541 +- 0.028 +- 0.023 ps, Dm_d
= 0.497 +- 0.024 +- 0.025 ps-1 were obtained, where in each case the first
error is statistical and the second systematic.Comment: 17 pages, 4 figures, submitted to Phys. Lett.
WW Production Cross Section and W Branching Fractions in e+e- Collisions at 189 GeV
From a data sample of 183 pb^-1 recorded at a center-of-mass energy of roots
= 189 GeV with the OPAL detector at LEP, 3068 W-pair candidate events are
selected. Assuming Standard Model W boson decay branching fractions, the W-pair
production cross section is measured to be sigmaWW = 16.30 +- 0.34(stat.) +-
0.18(syst.) pb. When combined with previous OPAL measurements, the W boson
branching fraction to hadrons is determined to be 68.32 +- 0.61(stat.) +-
0.28(syst.) % assuming lepton universality. These results are consistent with
Standard Model expectations.Comment: 22 pages, 5 figures, submitted to Phys. Lett.
Bending the Curve in Cardiovascular Disease Mortality: Bethesda + 40 and beyond
More than 40 years after the 1978 Bethesda Conference on the Declining Mortality from Coronary Heart Disease provided the scientific community with a blueprint for systematic analysis to understand declining rates of coronary heart disease, there are indications the decline has ended or even reversed despite advances in our knowledge about the condition and treatment. Recent data show a more complex situation, with mortality rates for overall cardiovascular disease, including coronary heart disease and stroke, decelerating, whereas those for heart failure are increasing. To mark the 40th anniversary of the Bethesda Conference, the National Heart, Lung, and Blood Institute and the American Heart Association cosponsored the "Bending the Curve in Cardiovascular Disease Mortality: Bethesda + 40" symposium. The objective was to examine the immediate and long-term outcomes of the 1978 conference and understand the current environment. Symposium themes included trends and future projections in cardiovascular disease (in the United States and internationally), the evolving obesity and diabetes epidemics, and harnessing emerging and innovative opportunities to preserve and promote cardiovascular health and prevent cardiovascular disease. In addition, participant-led discussion explored the challenges and barriers in promoting cardiovascular health across the lifespan and established a potential framework for observational research and interventions that would begin in early childhood (or ideally in utero). This report summarizes the relevant research, policy, and practice opportunities discussed at the symposium
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