43,151 research outputs found
The stability of the ways of coping (revised) questionnaire over time in parents of children with Downs-Syndrome:a research note
The stability of the Ways of Coping (Revised) Questionnaire over time was assessed by comparing the scores of 68 mothers and 53 fathers of school-aged children with Down's syndrome over a 3-year time interval on the five coping strategy subscales described by Knussen et al. (1992). For this analysis, mothers' and fathers' scores were analysed separately. It was shown by t tests that mothers' and fathers' scores on the coping strategy subscales had not significantly changed over the three-year period. Time 1 and Time 2 scores on all of the coping subscales were strongly positively associated, with the exception of fathers' scores on the Stoicism subscale. Test-retest reliability was adequate for all subscales except mothers' scores on the Passive Acceptance subscale and fathers' scores on the Stoicism subscale. These results, by demonstrating the stability of the Ways of Coping (Revised) Questionnaire over a 3-year time period, further illustrate the utility of this instrument for investigating coping in families with special problems
Collisionless heating in capacitive discharges enhanced by dual-frequency excitation
We discuss collisionless electron heating in capacitive discharges excited by a combination of two disparate frequencies. By developing an analytical model, we find, contrary to expectation, that the net heating in this case is much larger than the sum of the effects occurring when the two frequencies act separately. This prediction is substantiated by kinetic simulations, which are also in excellent general quantitative agreement with the model for discharge parameters that are typical of recent experiments
Training methods and considerations for practitioners to reduce interlimb asymmetries
Inter-limb asymmetries have been a common source of investigation in recent years with the majority of studies highlighting its prevalence in a range of athletic tasks. Few have tested whether reducing inter-limb differences are required for improved physical performance. Furthermore, there are a number of considerations that may exist which practitioners should consider prior to starting training interventions to reduce these differences. This article will discuss the available body of literature pertaining to the reduction of inter-limb asymmetries to date and provide example training programs to show how they can be addressed if their reduction is deemed necessary
Effects of inter-limb asymmetries on physical and sports performance: a systematic review
The prevalence of inter-limb asymmetries has been reported in numerous studies across a wide range of sports and physical qualities; however, few have analysed their effects on physical and sports performance. A systematic review of the literature was undertaken using the Medline and SPORT Discus databases, with all articles required to meet a specified criteria based on a quality review. Eighteen articles met the inclusion criteria, relating participant asymmetry scores to physical and sports performance measures. The findings of this systematic review indicate that inter-limb differences in strength may be detrimental to jumping, kicking and cycling performance. When inter-limb asymmetries are quantified during jumping based exercises, they have been primarily used to examine their association with change of direction speed with mixed findings. Inter-limb asymmetries have also been quantified in anthropometry, sprinting, dynamic balance and sport-specific actions, again with inconsistent findings. However, all results have been reported using associative analysis with physical or sport performance metrics with no randomised controlled trials included. Further research is warranted to understand the mechanisms that underpin inter-limb differences and the magnitude of performance changes that can be accounted for by these asymmetries
Ionized Gas Motions and the Structure of Feedback Near a Forming Globular Cluster in NGC 5253
We observed Brackett 4.05m emission towards the supernebula in
NGC 5253 with NIRSPEC on Keck II in adaptive optics mode, NIRSPAO, to probe
feedback from its exciting embedded super star cluster (SSC). NIRSPEC's
Slit-Viewing Camera was simultaneously used to image the K-band continuum at
resolution. We register the IR continuum with HST imaging, and
find that the visible clusters are offset from the K-band peak, which coincides
with the Br peak of the supernebula and its associated molecular
cloud. The spectra of the supernebula exhibit Br emission with a
strong, narrow core. The linewidths are 65-76 km s, FWHM, comparable to
those around individual ultra-compact HII regions within our Galaxy. A weak,
broad (FWHM150-175 km s) component is detected on the base of
the line, which could trace a population of sources with high-velocity winds.
The core velocity of Br emission shifts by +13 km s from NE to
SW across the supernebula, possibly indicating a bipolar outflow from an
embedded object, or linked to a foreground redshifted gas filament. The results
can be explained if the supernebula comprises thousands of ionized wind regions
around individual massive stars, stalled in their expansion due to critical
radiative cooling and unable to merge to drive a coherent cluster wind. Based
on the absence of an outflow with large mass loss, we conclude that feedback is
currently ineffective at dispersing gas, and the SSC retains enriched material
out of which it may continue to form stars.Comment: 24 pages, 9 figure
Infrared spectroscopy of star formation in galaxies
The Brackett alpha and beta lines with 7.2 seconds angular and 350 km/s velocity resolution were observed in 11 infrared-bright galaxies. From these measurements extinctions, Lyman continuum fluxes, and luminosities due to OB stars were derived. The galaxies observed to date are NGC3690, M38, NGC 5195, Arp 220, NGC 520, NGC660, NGC1614, NGC 3079, NGC 6946, NGC 7714, and Maffei 2, all of which were suggested at some time to be starburst ogjects. The contributions of OB stars to the luminosities of these galaxies can be quantified from the measurements and range from insignificant to sufficient to account for the total energy output. The OB stellar luminosities observed are as high as 10 to the 12th solar luminosities in the galaxy NGC 1614. It is noteworthy that star formation can play very different roles in the infrared energy output of galaxies of similar luminosity, as for example Arp 220 and NGC 1614. In addition to probing the star formation process in these galaxies, the Brackett line measurements, when compared to radio and infrared continuum results, have revealed some unexpected and at present imperfectly understood phenomena: in some very luminous sources the radio continuum appears to be suppressed relative to the infrared recombination lines; in many galaxies there is a substantial excess of 10 micron flux over that predicted from simple models of Lyman alpha heating of dust if young stars are the only significant energy source
Reactive strength index and its associations with measures of physical and sports performance: a systematic review with meta-analysis
Reactive strength index (RSI) is used frequently in the testing and monitoring of athletes. Associations with sports performance measures may vary dependent on the task but a literature synthesis has not been performed. The aim of this meta-analysis was to examine associations between RSI measured during rebound jumping tasks and measures of strength, linear and change of direction speed, and endurance performance. A systematic literature search with meta-analysis was conducted using databases PubMed, SPORTDiscus, Web of Science, and Ovid. Inclusion criteria required studies to (1) examine the relationship between RSI and an independent measure of physical or sporting performance for at least one variable; and (2) provide rebound test instructions to minimise ground contact time and maximise displacement of the jump. Methodological quality was assessed using a modified version of the Downs and Black Quality Index tool. Heterogeneity was examined via the Q statistic and I . Pooled effect sizes were calculated using a random-effects model, with Egger's regression test used to assess small study bias (inclusive of publication bias). Of the 1320 citations reviewed, a total of 32 studies were included in this meta-analysis. RSI was significantly and moderately associated with strength (isometric: r = 0.356 [95% CI 0.209-0.504]; isotonic: r = 0.365 [0.075-0.654]; pooled strength measures: r = 0.339 [0.209-0.469]) and endurance performance (r = 0.401 [0.173-0.629]). Significant moderate and negative associations were indicated for acceleration (r = - 0.426 [- 0.562 to - 0.290]), top speed (r = - 0.326 [- 0.502 to - 0.151]), and significant large negative associations were noted for change of direction speed (r = - 0.565 [- 0.726 to - 0.404]). Heterogeneity was trivial to moderate across all measures (I = 0-66%), and significant for isotonic strength and change of direction speed (p < 0.1). Evidence of small study bias was apparent for both acceleration and change of direction speed (p < 0.05). We identified primarily moderate associations between RSI and independent measures of physical and sporting performance, and the strength of these relationships varied based on the task and physical quality assessed. The findings from this meta-analysis can help practitioners to develop more targeted testing and monitoring processes. Future research may wish to examine if associations are stronger in tasks that display greater specificity. [Abstract copyright: © 2021. The Author(s), under exclusive licence to Springer Nature Switzerland AG.
[S IV] in the NGC 5253 Supernebula: Ionized Gas Kinematics at High Resolution
The nearby dwarf starburst galaxy NGC 5253 hosts a deeply embedded
radio-infrared supernebula excited by thousands of O stars. We have observed
this source in the 10.5{\mu}m line of S+3 at 3.8 kms-1 spectral and 1.4"
spatial resolution, using the high resolution spectrometer TEXES on the IRTF.
The line profile cannot be fit well by a single Gaussian. The best simple fit
describes the gas with two Gaussians, one near the galactic velocity with FWHM
33.6 km s-1 and another of similiar strength and FWHM 94 km s-1 centered \sim20
km s-1 to the blue. This suggests a model for the supernebula in which gas
flows towards us out of the molecular cloud, as in a "blister" or "champagne
flow" or in the HII regions modelled by Zhu (2006).Comment: Accepted for publication in the Astrophysical Journal 4 June 201
Electron heating mechanisms in dual frequency capacitive discharges
We discuss electron heating mechanisms in the sheath regions of dual-frequency capacitive discharges, with the twin aims of identifying the dominant mechanisms and supplying closed-form expressions from which the heating power can be estimated. We show that the heating effect produced by either Ohmic or collisionless heating is much larger when the discharge is excited by a superposition of currents at two frequencies than if either current had acted alone. This coupling effect occurs because the lower frequency current, while not directly heating the electrons to any great extent, strongly affects the spatial structure of the discharge in the sheath regions
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