387 research outputs found
Validity and reliability of an incremental double poling protocol in cross-country skiers
This study determined the validity and reliability of an incremental double poling protocol performed on a Concept II ski-ergometer and validated this against an existing treadmill ski-striding protocol. Ten well-trained male cross-country skiers (age: 19 ± 1.4 y; height: 182 ± 72 cm; body mass: 76.0 ± 10.8 kg, whole body VO2Peak: 5.2 ± 1.0 L.min-1; upper body VO2Peak: 4.6 ± 1.0 L.min-1; upper body:lower body ratio: 87.2 ± 5.6%) performed four VO2Peak tests; one treadmill ski-striding test and three double poling ski-ergometer tests over five days. Test-retest reliability of the ski-ergometer protocol was determined for maximal oxygen consumption (VO2peak). The ski-ergometer test showed excellent reliability for VO2Peak (L.min-1) (coefficient of variation [CV] = 1.9%, 95% confidence limit [95% CL] [1.2, 4.7]; r = 1.00, [0.96, 1.00]) and UBPPeak (W) (CV = 1.4%, [0.9, 3.4]; r = 1.00, [0.97, 1.00]). Very strong correlations existed between the ski-ergometer and the ski-striding protocol for VO2Peak (r = 0.95, [0.76, 0.99]). The upper body ski-ergometer test provided valid and reliable measurements of ski-specific upper body aerobic power in well-trained male cross-country skiers
The H-alpha Luminosity Function and Star Formation Rate Volume Density at z=0.8 from the NEWFIRM H-alpha Survey
[Abridged] We present new measurements of the H-alpha luminosity function
(LF) and SFR volume density for galaxies at z~0.8. Our analysis is based on
1.18m narrowband data from the NEWFIRM H-alpha Survey, a comprehensive
program designed to capture deep samples of intermediate redshift emission-line
galaxies using narrowband imaging in the near-infrared. The combination of
depth ( erg s cm in H-alpha at
3) and areal coverage (0.82 deg) complements other recent H-alpha
studies at similar redshifts, and enables us to minimize the impact of cosmic
variance and place robust constraints on the shape of the LF. The present
sample contains 818 NB118 excess objects, 394 of which are selected as H-alpha
emitters. Optical spectroscopy has been obtained for 62% of the NB118 excess
objects. Empirical optical broadband color classification is used to sort the
remainder of the sample. A comparison of the LFs constructed for the four
individual fields reveals significant cosmic variance, emphasizing that
multiple, widely separated observations are required. The dust-corrected LF is
well-described by a Schechter function with L*=10^{43.00\pm0.52} ergs s^{-1},
\phi*=10^{-3.20\pm0.54} Mpc^{-3}, and \alpha=-1.6\pm0.19. We compare our
H-alpha LF and SFR density to those at z<1, and find a rise in the SFR density
\propto(1+z)^{3.4}, which we attribute to significant L* evolution. Our H-alpha
SFR density of 10^{-1.00\pm0.18} M_sun yr^{-1} Mpc^{-3} is consistent with UV
and [O II] measurements at z~1. We discuss how these results compare to other
H-alpha surveys at z~0.8, and find that the different methods used to determine
survey completeness can lead to inconsistent results. This suggests that future
surveys probing fainter luminosities are needed, and more rigorous methods of
estimating the completeness should be adopted as standard procedure.Comment: 19 pages (emulate-ApJ format), 16 figures, 5 tables, published in
ApJ. Modified to match ApJ versio
Killer Jobs: The Dark Side of Being a Physical Education Teacher
The profession of physical education (PE) teacher involves a variety of risks. Most PE teachers or future teachers are aware of the risks associated with their students becoming injured. Sport law classes often discuss negligence, risk management, proper supervision, suitable equipment, appropriate instruction, proper matching of opponents, etc. The focus is primarily or exclusively on student safety. Rarely is the focus on the risks PE teachers face themselves. This article discusses the largely neglected topics of transportation, workplace violence, and slip/trip and falls, all of which are occupational hazards for PE teachers, potentially associated with serious injuries or death
Roar of the Crowd: Noise-Related Safety Concerns in Sport
In sport the safety of staff, participants and spectators is of the utmost importance. Therefore, sport venue and event managers should take every precaution to address safety concerns while planning for and executing events or activities. While venue managers have a legal duty to protect fans and participants, federal regulations exist to ensure a safe workplace for all employees, including those at a sports event. This is a conceptual article intended to assist practitioners to identify potentially unexpected hazards within the work environment, as well as strategies to eliminate or manage them. The authors examine existing federal regulations, current research associated with hearing/noise-related concerns and specific research undertaken in the sport environment. The article concludes with recommended prevention strategies for facility and event managers to assist them in meeting their professional and legal obligations
Comparing the relation between star formation and galaxy mass in different environments
Analyzing 24 mu m MIPS/Spitzer data and the [O II]3727 line of a sample of
galaxies at 0.4 < z < 0.8 from the ESO Distant Cluster Survey (EDisCS), we
investigate the ongoing star formation rate (SFR) and the specific star
formation rate (SSFR) as a function of stellar mass in galaxy clusters and
groups, and compare with field studies. As for the field, we find a decline in
SFR with time, indicating that star formation (SF) was more active in the past,
and a decline in SSFR as galaxy stellar mass increases, showing that the
current SF contributes more to the fractional growth of low-mass galaxies than
high-mass galaxies. However, we find a lower median SFR (by a factor of ~1.5)
in cluster star-forming galaxies than in the field. The difference is highly
significant when all Spitzer and emission-line galaxies are considered,
regardless of color. It remains significant at z>0.6 after removing red
emission-line (REL) galaxies, to avoid possible AGN contamination. While there
is overlap between the cluster and field SFR-Mass relations, we find a
population of cluster galaxies (10-25%) with reduced SFR for their mass. These
are likely to be in transition from star-forming to passive. Comparing
separately clusters and groups at z>0.6, only cluster trends are significantly
different from the field, and the average cluster SFR at a given mass is ~2
times lower than the field. We conclude that the average SFR in star-forming
galaxies varies with galaxy environment at a fixed galaxy mass.Comment: ApJL in pres
Dust-Obscured Star-Formation in Intermediate Redshift Galaxy Clusters
We present Spitzer MIPS 24-micron observations of 16 0.4<z<0.8 galaxy
clusters drawn from the ESO Distant Cluster Survey (EDisCS). This is the first
large 24-micron survey of clusters at intermediate redshift. The depth of our
imaging corresponds to a total IR luminosity of 8x10^10 Lsun, just below the
luminosity of luminous infrared galaxies (LIRGs), and 6^{+1}_{-1}% of M_V < -19
cluster members show 24-micron emission at or above this level. We compare with
a large sample of coeval field galaxies and find that while the fraction of
cluster LIRGs lies significantly below that of the field, the IR luminosities
of the field and cluster galaxies are consistent. However, the stellar masses
of the EDisCS LIRGs are systematically higher than those of the field LIRGs. A
comparison with optical data reveals that ~80% of cluster LIRGs are blue and
the remaining 20% lie on the red sequence. Of LIRGs with optical spectra,
88^{+4}_{-5}% show [O II] emission with EW([O II])>5A, and ~75% exhibit optical
signatures of dusty starbursts. On average, the fraction of cluster LIRGs
increases with projected cluster-centric radius but remains systematically
lower than the field fraction over the area probed (< 1.5xR200). The amount of
obscured star formation declines significantly over the 2.4 Gyr interval
spanned by the EDisCS sample, and the rate of decline is the same for the
cluster and field populations. Our results are consistent with an exponentially
declining LIRG fraction, with the decline in the field delayed by ~1 Gyr
relative to the clusters.Comment: 15 pages, 9 figure
The H-alpha Luminosity Function and Star Formation Rate Volume Density at z=0.8 from the NEWFIRM H-alpha Survey
[Abridged] We present new measurements of the H-alpha luminosity function
(LF) and SFR volume density for galaxies at z~0.8. Our analysis is based on
1.18m narrowband data from the NEWFIRM H-alpha Survey, a comprehensive
program designed to capture deep samples of intermediate redshift emission-line
galaxies using narrowband imaging in the near-infrared. The combination of
depth ( erg s cm in H-alpha at
3) and areal coverage (0.82 deg) complements other recent H-alpha
studies at similar redshifts, and enables us to minimize the impact of cosmic
variance and place robust constraints on the shape of the LF. The present
sample contains 818 NB118 excess objects, 394 of which are selected as H-alpha
emitters. Optical spectroscopy has been obtained for 62% of the NB118 excess
objects. Empirical optical broadband color classification is used to sort the
remainder of the sample. A comparison of the LFs constructed for the four
individual fields reveals significant cosmic variance, emphasizing that
multiple, widely separated observations are required. The dust-corrected LF is
well-described by a Schechter function with L*=10^{43.00\pm0.52} ergs s^{-1},
\phi*=10^{-3.20\pm0.54} Mpc^{-3}, and \alpha=-1.6\pm0.19. We compare our
H-alpha LF and SFR density to those at z<1, and find a rise in the SFR density
\propto(1+z)^{3.4}, which we attribute to significant L* evolution. Our H-alpha
SFR density of 10^{-1.00\pm0.18} M_sun yr^{-1} Mpc^{-3} is consistent with UV
and [O II] measurements at z~1. We discuss how these results compare to other
H-alpha surveys at z~0.8, and find that the different methods used to determine
survey completeness can lead to inconsistent results. This suggests that future
surveys probing fainter luminosities are needed, and more rigorous methods of
estimating the completeness should be adopted as standard procedure.Comment: 19 pages (emulate-ApJ format), 16 figures, 5 tables, published in
ApJ. Modified to match ApJ versio
The IR Luminosity Functions of Rich Clusters
We present MIPS observations of the cluster A3266. About 100 spectroscopic
cluster members have been detected at 24 micron. The IR luminosity function in
A3266 is very similar to that in the Coma cluster down to the detection limit
L_IR~10^43 ergs/s, suggesting a universal form of the bright end IR LF for
local rich clusters with M~10^15 M_sun. The shape of the bright end of the
A3266-Coma composite IR LF is not significantly different from that of nearby
field galaxies, but the fraction of IR-bright galaxies (SFR > 0.2M_sun/yr) in
both clusters increases with cluster-centric radius. The decrease of the blue
galaxy fraction toward the high density cores only accounts for part of the
trend; the fraction of red galaxies with moderate SFRs (0.2 < SFR < 1 M_sun/yr)
also decreases with increasing galaxy density. These results suggest that for
the IR bright galaxies, nearby rich clusters are distinguished from the field
by a lower star-forming galaxy fraction, but not by a change in L*_IR. The
composite IR LF of Coma and A3266 shows strong evolution when compared with the
composite IR LF of two z~0.8 clusters, MS 1054 and RX J0152, with L*_IR \propto
(1+z)^{3.2+/-0.7},Phi*_IR \propto (1+z)^{1.7+/-1.0}. This L*_IR evolution is
indistinguishable from that in the field, and the Phi*_IR evolution is
stronger, but still consistent with that in the field. The similarity of the
evolution of bright-end IR LF in very different cluster and field environments
suggests either this evolution is driven by the mechanism that works in both
environments, or clusters continually replenish their star-forming galaxies
from the field, yielding an evolution in the IR LF that is similar to the
field. The mass-normalized integrated star formation rates (SFRs) of clusters
within 0.5R_200 also evolve strongly with redshift, as (1+z)^5.3.Comment: 15 pages, 8 figures, 1 table, accepted by Ap
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