2,169 research outputs found
The use of a functional test battery as a noninvasive method of fatigue assessment
To assess whether a battery of performance markers, both individually and as group, would be sensitive to fatigue, a within group random cross-over design compared multiple variables during seated control and fatigue (repeated sprint cycling) conditions. Thirty-two physically active participants completed a neuromuscular fatigue questionnaire, Stroop task, postural sway, squat jump, countermovement jump, isometric mid-thigh pull and 10 s maximal sprint cycle (Sprintmax) before and after each condition (15 min, 1 h, 24 h and 48 h). In comparison to control, larger neuromuscular fatigue questionnaire total score decrements were observed 15 min (5.20 ± 4.6), 1 h (3.33 ± 3.9) and 24 h (1.83 ± 4.8) after cycling. Similarly, the fatigue condition elicited greater declines than control at 15 min and 1 h post in countermovement jump height (1.67 ± 1.90 cm and 1.04 ± 2.10 cm), flight time-contraction time ratio (0.03 ± 0.06 and 0.05 ± 0.11), and velocity (0.06 ± 0.07 m?s-1 and 0.04 ± 0.08 m?s-1). After fatigue, decrements were observed up to 48 h for average Sprintmax cadence (4-6 RPM), up to 24 h in peak Sprintmax cadence (2-5 RPM) and up to 1 h in average and peak Sprintmax power (45 ± 60Wand 58 ± 71 W). Modelling variables in a stepwise regression demonstrated that CMJ height explained 53.2% and 51.7% of 24 h and 48 h Sprintmax average power output. Based upon these data, the fatigue induced by repeated sprint cycling coincided with changes in the perception of fatigue and markers of performance during countermovement and squat jumps. Furthermore, multiple regression modelling revealed that a single variable (countermovement jump height) explained average power output. © 2019 Hughes et al.This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited
Aircraft Engine Technology for Green Aviation to Reduce Fuel Burn
The NASA Fundamental Aeronautics Program Subsonic Fixed Wing Project and Integrated Systems Research Program Environmentally Responsible Aviation Project in the Aeronautics Research Mission Directorate are conducting research on advanced aircraft technology to address the environmental goals of reducing fuel burn, noise and NOx emissions for aircraft in 2020 and beyond. Both Projects, in collaborative partnerships with U.S. Industry, Academia, and other Government Agencies, have made significant progress toward reaching the N+2 (2020) and N+3 (beyond 2025) installed fuel burn goals by fundamental aircraft engine technology development, subscale component experimental investigations, full scale integrated systems validation testing, and development validation of state of the art computation design and analysis codes. Specific areas of propulsion technology research are discussed and progress to date
The effects of either a mirror, internal or external focus instructions on single and multi-joint tasks
Training in front of mirrors is common, yet little is known about how the use of mirrors effects muscle force production. Accordingly, we investigated how performing in front of a mirror influences performance in single and multi-joint tasks, and compared the mirror condition to the established performance effects of internal focus (IF) and external focus (EF) instructions in a two part experiment. In the single-joint experiment 28 resistance-trained participants (14 males and 14 females) completed two elbow flexion maximal voluntary isometric contractions under four conditions: mirror, IF, EF and neutral instructions. During these trials, surface EMG activity of the biceps and triceps were recorded. In the multi-joint experiment the same participants performed counter-movement jumps on a force plate under the same four conditions. Single-joint experiment: EF led to greater normalized force production compared to all conditions (P †0.02, effect-size range [ES] = 0.46â1.31). No differences were observed between neutral and mirror conditions (P = 0.15, ES = 0.15), but both were greater than IF (PP â„ 0.1, ES = 0.10â0.21). Multi-joint experiment: Despite no statistical difference (P = 0.10), a moderate effect size was observed for jump height whereby EF was greater than IF (ES = 0.51). No differences were observed between neutral and mirror conditions (ES = 0.01), but both were greater than IF (ES = 0.20â22). The mirror condition led to superior performance compared to IF, inferior performance compared to EF, and was equal to a neutral condition in both tasks. These results provide novel and practical evidence concerning mirror training during resistance type training
Countermovement jump and squat jump force-time curve analysis in control and fatigue conditions
This study aimed to reanalyze previously published discrete force data from countermovement jumps (CMJs) and squat jumps (SJs) using statistical parametric mapping (SPM), a statistical method that enables analysis of data in its native, complete state. Statistical parametric mapping analysis of 1-dimensional (1D) force-time curves was compared with previous zero-dimensional (0D) analysis of peak force to assess sensitivity of 1D analysis. Thirty-two subjects completed CMJs and SJs at baseline, 15 minutes, 1, 24, and 48 hours following fatigue and control conditions in a pseudo random cross-over design. Absolute (CMJABS/SJABS) and time-normalized (CMJNORM/SJNORM) force-time data were analyzed using SPM 2-way repeated measures analysis of variance with significance accepted at α = 0.05. The SPM indicated a magnitude of difference between force-time data with main effects for time (p \u3c 0.001) and interaction (p \u3c 0.001) observed in CMJABS, SJABS, and SJNORM, whereas previously published 0D analysis reported no 2-way interaction in CMJ and SJ peak force. This exploratory research demonstrates the strength of SPM to identify changes between entire movement force-time curves. Continued development and use of SPM analysis techniques could present the opportunity for refined assessment of athlete fatigue and readiness with the analysis of complete force-time curves
An Investigation of the Dust Content in the Galaxy pair NGC 1512/1510 from Near-Infrared to Millimeter Wavelengths
We combine new ASTE/AzTEC 1.1 mm maps of the galaxy pair NGC 1512/1510 with
archival Spitzer IRAC and MIPS images covering the wavelength range 3.6--160 um
from the SINGS project to derive accurate dust masses in each galaxy, and in
sub--galactic regions in NGC 1512. The two galaxies form a pair consisting of a
large, high--metallicity spiral (NGC 1512) and a low metallicity, blue compact
dwarf (NGC 1510). The derived total dust masses are (2.4+/-0.6) 10^7 Msun and
(1.7+/-3.6) 10^5 Msun for NGC 1512 and NGC 1510, respectively. The derived
ratio of dust mass to H I gas mass for the galaxy pair (0.0034) is much lower
than expected, while regions within NGC 1512, specifically the central region
and the arms, do not show such unusually low ratios; furthermore, the
dust--to--gas ratio is within expectations for NGC 1510. These results suggest
that a fraction of the H I included in the determination of the M_d/M_HI ratio
of the NGC 1512/1510 pair is not associated with the star forming disks/regions
of either galaxy. We also perform simple two--temperature (warm + cold)
modified--blackbody fits to the far--infrared/mm data. The warm dust
temperature of the low--metallicity NGC 1510 (~36 K) is substantially higher
than that of the high--metallicity NGC 1512 (~24 K). In both galaxies, a
substantial fraction (>93%) of the total dust mass is in a cool dust component,
with temperatures 14--16 K for NGC 1512 and 15--24 K for NGC 1510. In contrast,
the warm dust in the arms and central regions of NGC 1512 represents a much
larger fraction of the total dust content, in agreement with the fact that all
three regions have higher specific star formation rates than the average in the
galaxy.Comment: 33 pages, 4 figures, 4 tables, accepted for publication in A
The infrared compactness-temperature relation for quiescent and starburst galaxies
IRAS observations show the existence of a correlation between the infrared
luminosity Lir and dust temperature Td in star-forming galaxies, in which
larger Lir leads to higher dust temperature. The Lir-Td relation is commonly
seen as reflecting the increase in dust temperature in galaxies with higher
star formation rate. Even though the correlation shows a significant amount of
dispersion, a unique relation has been commonly used to construct spectral
energy distributions of galaxies in distant universe studies, such as source
number counting or photometric redshift determination. In this work, we
introduce a new parameter, namely the size of the star-forming region Rir and
lay out the empirical and modelled relation between the global parameters Lir,
Td and Rir of IR-bright non-AGN galaxies. IRAS 60-to-100um color is used as a
proxy for the dust temperature and the 1.4GHz radio contiuum emission for the
infrared spatial distribution. The analysis has been carried out on two
samples. The first one is made of the galaxies from the 60um flux-limited IRAS
Revised Bright Galaxy Samples which have a reliable RC size estimate from the
VLA follow-ups of the IRAS Bright Galaxy Samples. The second is made of the
sources from the 170um ISOPHOT Serendipity Sky Survey which are resolved by the
NVSS or FIRST surveys. We show that the dispersion in the Lir-Td diagram can be
reduced to a relation between the infrared surface brightness and the dust
temperature, a relation that spans 5 orders of magnitude in surface brightness.
We explored the physical processes giving rise to the Sir-Td relation, and show
that it can be derived from the Schmidt law, which relates the star formation
rate to the gas surface density.Comment: 13 pages, 7 figures, accepted for publication in A&
Advanced Cardiac Resuscitation Evaluation (ACRE): A randomised single-blind controlled trial of peer-led vs. expert-led advanced resuscitation training
<p>Abstract</p> <p>Background</p> <p>Advanced resuscitation skills training is an important and enjoyable part of medical training, but requires small group instruction to ensure active participation of all students. Increases in student numbers have made this increasingly difficult to achieve.</p> <p>Methods</p> <p>A single-blind randomised controlled trial of peer-led vs. expert-led resuscitation training was performed using a group of sixth-year medical students as peer instructors. The expert instructors were a senior and a middle grade doctor, and a nurse who is an Advanced Life Support (ALS) Instructor.</p> <p>A power calculation showed that the trial would have a greater than 90% chance of rejecting the null hypothesis (that expert-led groups performed 20% better than peer-led groups) if that were the true situation. Secondary outcome measures were the proportion of High Pass grades in each groups and safety incidents.</p> <p>The peer instructors designed and delivered their own course material. To ensure safety, the peer-led groups used modified defibrillators that could deliver only low-energy shocks.</p> <p>Blinded assessment was conducted using an Objective Structured Clinical Examination (OSCE). The checklist items were based on International Liaison Committee on Resuscitation (ILCOR) guidelines using Ebel standard-setting methods that emphasised patient and staff safety and clinical effectiveness.</p> <p>The results were analysed using Exact methods, chi-squared and t-test.</p> <p>Results</p> <p>A total of 132 students were randomised: 58 into the expert-led group, 74 into the peer-led group. 57/58 (98%) of students from the expert-led group achieved a Pass compared to 72/74 (97%) from the peer-led group: Exact statistics confirmed that it was very unlikely (p = 0.0001) that the expert-led group was 20% better than the peer-led group.</p> <p>There were no safety incidents, and High Pass grades were achieved by 64 (49%) of students: 33/58 (57%) from the expert-led group, 31/74 (42%) from the peer-led group. Exact statistics showed that the difference of 15% meant that it was possible that the expert-led teaching was 20% better at generating students with High Passes.</p> <p>Conclusions</p> <p>The key elements of advanced cardiac resuscitation can be safely and effectively taught to medical students in small groups by peer-instructors who have undergone basic medical education training.</p
Measurement of advection and surface-atmosphere exchange in complex terrain.
grant NER/S/J/2004/13118Accurate observations of the carbon cycle are essential as inputs to global climate
models. Observations made by the micrometeorological technique of eddy
covariance, whist widespread, may be incorrect if air is advected away from below
the sensor system. This is potentially a serious issue for FLUXNET, a global network
of eddy flux sites. The approach in this thesis to investigate this problem was
twofold:
A full micrometeorological mass balance using an instrumented 50 m long by 50 m
wide by 6 m high Cartesian control volume (CV) covering the understorey
vegetation of a 40 m high Eucalyptus forest was carried out; situated adjacent to the
Tumbaruma eddy covariance site in Australia. At night positive (into the
atmosphere) advection fluxes caused by down-slope katabatic drainage within the
forest trunk space, dominated the CO2 flux budget of the CV, with both vertical and
horizontal advection terms having predominantly positive values. The nighttime
estimates of advection were subject to large systematic errors that were of the same
order of magnitude as the advection signal. Nevertheless, the nocturnal respiration
flux of the understorey vegetation was clearly resolved by the diurnal full mass
balance flux curve that resulted from the experiment, having a typical value of 5
ÎŒmol m-2 s-1.
A second experiment carried out at the Griffin forest in Scotland demonstrated the
presence of sub-canopy katabatic/gravity flows at night that would be likely to cause
scalar advection resulting in underestimation of the nocturnal respiration flux of CO2.
Finally, it is recommended that the micrometeorological mass balance technique
should not be deployed across FLUXNET because of financial cost and issues of
systematic error
Selection of ULIRGs in Infrared and Submm Surveys
We examine the selection characteristics of infrared and sub-mm surveys with
IRAS, Spitzer, BLAST, Herschel and SCUBA and identify the range of dust
temperatures these surveys are sensitive to, for galaxies in the ULIRG
luminosity range (12<log(LIR)<13), between z=0 and z=4. We find that the extent
of the redshift range over which surveys are unbiased is a function of the
wavelength of selection, flux density limit and ULIRG luminosity. Short
wavelength (<200{\mu}m) surveys with IRAS, Spitzer/MIPS and Herschel/PACS are
sensitive to all SED types in a large temperature interval (17-87K), over a
substantial fraction of their accessible redshift range. On the other hand,
long wavelength (>200{\mu}m) surveys with BLAST, Herschel/ SPIRE and SCUBA are
significantly more sensitive to cold ULIRGs, disfavouring warmer SEDs even at
low redshifts. We evaluate observations in the context of survey selection
effects, finding that the lack of cold ULIRGs in the local (z<0.1) Universe is
not a consequence of selection and that the range of ULIRG temperatures seen
locally is only a subset of a much larger range which exists at high redshift.
We demonstrate that the local luminosity-temperature (L-T) relation, which
indicates that more luminous sources are also hotter, is not applicable in the
distant Universe when extrapolated to the ULIRG regime, because the scatter in
observed temperatures is too large. Finally, we show that the difference
between the ULIRG temperature distributions locally and at high redshift is not
the result of galaxies becoming colder due to an L-T relation which evolves as
a function of redshift. Instead, they are consistent with a picture where the
evolution of the infrared luminosity function is temperature dependent, i.e.
cold galaxies evolve at a faster rate than their warm counterparts.Comment: 11 pages, 6 figures, accepted for publication in MNRA
The local FIR Galaxy Colour-Luminosity distribution: A reference for BLAST, and Herschel/SPIRE sub-mm surveys
We measure the local galaxy far-infrared (FIR) 60-to-100 um colour-luminosity
distribution using an all-sky IRAS survey. This distribution is an important
reference for the next generation of FIR--submillimetre surveys that have and
will conduct deep extra-galactic surveys at 250--500 um. With the peak in
dust-obscured star-forming activity leading to present-day giant ellipticals
now believed to occur in sub-mm galaxies near z~2.5, these new
FIR--submillimetre surveys will directly sample the SEDs of these distant
objects at rest-frame FIR wavelengths similar to those at which local galaxies
were observed by IRAS. We have taken care to correct for temperature bias and
evolution effects in our IRAS 60 um-selected sample. We verify that our
colour-luminosity distribution is consistent with measurements of the local FIR
luminosity function, before applying it to the higher-redshift Universe. We
compare our colour-luminosity correlation with recent dust-temperature
measurements of sub-mm galaxies and find evidence for pure luminosity evolution
of the form (1+z)^3. This distribution will be useful for the development of
evolutionary models for BLAST and SPIRE surveys as it provides a statistical
distribution of rest-frame dust temperatures for galaxies as a function of
luminosity.Comment: 12 pages, 7 figures. MNRAS in press. This revision matches final
published version. Fixes typos in footnote 1 and equation 8. Minor
modifications to text and references. Final results unchange
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