280 research outputs found
Neck-cooling improves repeated sprint performance in the heat
The present study evaluated the effect of neck-cooling during exercise on repeated sprint ability in a hot environment. Seven team-sport playing males completed two experimental trials involving repeated sprint exercise (5 × 6 s) before and after two 45 min bouts of a football specific intermittent treadmill protocol in the heat (33.0 ± 0.2°C; 53 ± 2% relative humidity). Participants wore a neck-cooling collar in one of the trials (CC). Mean power output and peak power output declined over time in both trials but were higher in CC (540 ± 99 v 507 ± 122 W, d = 0.32; 719 ± 158 v 680 ± 182 W, d = 0.24 respectively). The improved power output was particularly pronounced (d = 0.51–0.88) after the 2nd 45 min bout but the CC had no effect on % fatigue. The collar lowered neck temperature and the thermal sensation of the neck (P 0.05). There were no trial differences but interaction effects were demonstrated for prolactin concentration and rating of perceived exertion (RPE). Prolactin concentration was initially higher in the collar cold trial and then was lower from 45 min onwards (interaction trial × time P = 0.04). RPE was lower during the football intermittent treadmill protocol in the collar cold trial (interaction trial × time P = 0.01). Neck-cooling during exercise improves repeated sprint performance in a hot environment without altering physiological or neuroendocrinological responses. RPE is reduced and may partially explain the performance improvement
Cynthia Izaguirre, News Anchor for the Channel 8 News at 5 and 10 o'clock
This article is a short biography of Cynthia Izaguirre, news anchor for the Channel 8 News, based on an oral history discussing her education and career
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Cynthia Izaguirre, News Anchor for the Channel 8 News at 5 and 10 o'clock
This article is a short biography of Cynthia Izaguirre, news anchor for the Channel 8 News, based on an oral history discussing her education and career
A Sub-arcsecond Survey Toward Class 0 Protostars in Perseus: Searching for Signatures of Protostellar Disks
We present a CARMA 1.3 mm continuum survey toward 9 Class 0 protostars in the
Perseus molecular cloud at 0.3 (70 AU) resolution. This
study approximately doubles the number of Class 0 protostars observed with
spatial resolutions 100 AU at millimeter wavelengths, enabling the presence
of protostellar disks and proto-binary systems to be probed. We detect
flattened structures with radii 100 AU around 2 sources (L1448 IRS2 and
Per-emb-14) and these sources may be strong disk candidates.
Marginally-resolved structures with position angles within 30 of
perpendicular to the outflow are found toward 3 protostars (L1448 IRS3C, IRAS
03282+3035, and L1448C) and are considered disk candidates. Two others (L1448
IRS3B and IRAS 03292+3039) have resolved structure, possibly indicative of
massive inner envelopes or disks; L1448 IRS3B also has a companion separated by
0.9 (210 AU). IC348-MMS does not have well-resolved
structure and the candidate first hydrostatic core L1451-MMS is marginally
resolved on 1 scales. The strong disk candidate sources were
followed-up with CO () observations, detecting velocity
gradients consistent with rotation, but it is unclear if the rotation is
Keplerian. We compare the observed visibility amplitudes to radiative transfer
models, finding that visibility amplitude ratios suggest a compact component
(possibly a disk) is necessary for 5 of 9 Class 0 sources; envelopes alone may
explain the other 4 systems. We conclude that there is evidence for the
formation of large disks in the Class 0 phase with a range of radii and masses
dependent upon their initial formation conditions.Comment: Accepted to ApJ, 58 pages, 19 Figures, 5 Table
The Spitzer c2d Survey of Nearby Dense Cores: VI. The Protostars of Lynds Dark Nebula 1221
Observations of Lynds Dark Nebula 1221 from the Spitzer Space Telescope are
presented. These data show three candidate protostars towards L1221, only two
of which were previously known. The infrared observations also show signatures
of outflowing material, an interpretation which is also supported by radio
observations with the Very Large Array. In addition, molecular line maps from
the Five College Radio Astronomy Observatory are shown.
One-dimensional dust continuum modelling of two of these protostars, IRS1 and
IRS3, is described. These models show two distinctly different protostars
forming in very similar environments. IRS1 shows a higher luminosity and larger
inner radius of the envelope than IRS3. The disparity could be caused by a
difference in age or mass, orientation of outflow cavities, or the impact of a
binary in the IRS1 core.Comment: accepted for publication in Ap
Extreme Active Molecular Jets in L1448C
The protostellar jet driven by L1448C was observed in the SiO J=8-7 and CO
J=3-2 lines and 350 GHz dust continuum at ~1" resolution with the Submillimeter
Array (SMA). A narrow jet from the northern source L1448C(N) was observed in
the SiO and the high-velocity CO. The jet consists of a chain of emission knots
with an inter-knot spacing of ~2" (500 AU) and a semi-periodic velocity
variation. The innermost pair of knots, which are significant in the SiO map
but barely seen in the CO, are located at ~1" (250 AU) from the central source,
L1448C(N). Since the dynamical time scale for the innermost pair is only ~10
yr, SiO may have been formed in the protostellar wind through the gas-phase
reaction, or been formed on the dust grain and directly released into the gas
phase by means of shocks. It is found that the jet is extremely active with a
mechanical luminosity of ~7 L_sun, which is comparable to the bolometric
luminosity of the central source (7.5 L_sun). The mass accretion rate onto the
protostar derived from the mass-loss rate is ~10^{-5} M_sun/yr. Such a high
mass accretion rate suggests that the mass and the age of the central star are
0.03-0.09 M_sun and (4-12)x10^3 yr, respectively, implying that the central
star is in the very early stage of protostellar evolution. The low-velocity CO
emission delineates two V-shaped shells with a common apex at L1448C(N). The
kinematics of these shells are reproduced by the model of a wide opening angle
wind. The co-existence of the highly-collimated jets and the wide-opening angle
shells can be explained by the unified X-wind model" in which highly-collimated
jet components correspond to the on-axis density enhancement of the
wide-opening angle wind. The CO =3--2 map also revealed the second outflow
driven by the southern source L1448C(S) located at ~8.3" (2000 AU) from
L1448C(N).Comment: 45 pages, 13 figures, Accepted for the publication in the
Astrophysical Journa
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