463 research outputs found
A Mass-Loss Rate Determination For Zeta Puppis From The Quantitative Analysis Of X-Ray Emission-Line Profiles
We fit every emission line in the high-resolution Chandra grating spectrum of. Pup with an empirical line profile model that accounts for the effects of Doppler broadening and attenuation by the bulk wind. For each of 16 lines or line complexes that can be reliably measured, we determine a best-fitting fiducial optical depth, tau(*) equivalent to kappa(M) over dot/4 pi R(*)upsilon(infinity), and place confidence limits on this parameter. These 16 lines include seven that have not previously been reported on in the literature. The extended wavelength range of these lines allows us to infer, for the first time, a clear increase in tau(*) with line wavelength, as expected from the wavelength increase of bound-free absorption opacity. The small overall values of tau(*), reflected in the rather modest asymmetry in the line profiles, can moreover all be fitted simultaneously by simply assuming a moderate mass-loss rate of 3.5 +/- 0.3 x 10(-6) M(circle dot) yr(-1), without any need to invoke porosity effects in the wind. The quoted uncertainty is statistical, but the largest source of uncertainty in the derived mass-loss rate is due to the uncertainty in the elemental abundances of zeta Pup, which affects the continuum opacity of the wind, and which we estimate to be a factor of 2. Even so, the mass-loss rate we find is significantly below the most recent smooth-wind H alpha mass-loss rate determinations for zeta Pup, but is in line with newer determinations that account for small-scale wind clumping. If zeta Pup is representative of other massive stars, these results will have important implications for stellar and Galactic evolution
Isometric Posterior Chain Peak Force Recovery Response Following Match-Play in Elite Youth Soccer Players:Associations with Relative Posterior Chain Strength
A mass-loss rate determination for zeta Puppis from the quantitative analysis of X-ray emission line profiles
We fit every emission line in the high-resolution Chandra grating spectrum of
zeta Pup with an empirical line profile model that accounts for the effects of
Doppler broadening and attenuation by the bulk wind. For each of sixteen lines
or line complexes that can be reliably measured, we determine a best-fitting
fiducial optical depth, tau_* = kappa*Mdot/4{pi}R_{\ast}v_{\infty}, and place
confidence limits on this parameter. These sixteen lines include seven that
have not previously been reported on in the literature. The extended wavelength
range of these lines allows us to infer, for the first time, a clear increase
in tau_* with line wavelength, as expected from the wavelength increase of
bound-free absorption opacity. The small overall values of tau_*, reflected in
the rather modest asymmetry in the line profiles, can moreover all be fit
simultaneously by simply assuming a moderate mass-loss rate of 3.5 \pm 0.3
\times 10^{-6} Msun/yr, without any need to invoke porosity effects in the
wind. The quoted uncertainty is statistical, but the largest source of
uncertainty in the derived mass-loss rate is due to the uncertainty in the
elemental abundances of zeta Pup, which affects the continuum opacity of the
wind, and which we estimate to be a factor of two. Even so, the mass-loss rate
we find is significantly below the most recent smooth-wind H-alpha mass-loss
rate determinations for zeta Pup, but is in line with newer determinations that
account for small-scale wind clumping. If zeta Pup is representative of other
massive stars, these results will have important implications for stellar and
galactic evolution.Comment: Accepted for publication in the Monthly Notices of the Royal
Astronomical Society. 17 pages, including 14 figures (7 color
Failing boys and moral panics: perspectives on the underachievement debate
The paper re-examines the underachievement debate from the perspective of the âdiscourse of derisionâ that surrounds much writing in this area. It considers the contradictions and inconsistencies which underpin much of the discourse â from a reinterpretation of examination scores, to the conflation of the concepts of âunderâ and âlowâ achievement and finally to the lack of consensus on a means of defining and measuring the term underachievement. In doing so, this paper suggests a more innovative approach for understanding, re-evaluating and perhaps rejecting the notion of underachievement
âWe have to wait in a queue for our turn quite a bitâ Examining childrenâs physical activity during primary physical education lessons
The overall purpose of this study was to examine childrenâs physical activity (PA) during primary physical education (PE). This was achieved through the following two research objectives: (1) to measure childrenâs PA, lesson context and teacher promotion of PA during PE lessons; and (2) to explore teachersâ and childrenâs perspectives on PA levels during PE lessons. Evidence suggests that childrenâs PA during PE is below recommended levels and further research is required to understand the reasons why. Through a mixed method design, 138 children were observed using the System for Observing Fitness and Instruction Time, 80 children participated in group interviews, and 13 teachers were interviewed, across three primary schools in England. Findings indicated that the mean percentage of lesson time allocated to moderate to vigorous PA (MVPA) was 42.4% and the average lesson length was 35.3 minutes. Qualitative themes identified were: âknowledge and beliefsâ; âteacher pedagogyâ; and âteacher developmentâ. The findings indicate that a change in perspective is needed, which includes a focus on PA during primary PE lessons. Intervention work is required that targets teachersâ knowledge and beliefs towards PE along with the development of effective teaching strategies. However, this needs to be grounded in an ecological approach which will allow researchers and schools to target the various levels of influence. It is strongly recommended that interventions are grounded in behaviour change theory, as this study indicates that sharing knowledge about pedagogical strategies to increase childrenâs MVPA does not necessarily produce changes in teachersâ behaviours
Relating Therapist Characteristics to Client Engagement and the Therapeutic Alliance in an Adolescent Custodial Group Substance Misuse Treatment Program
The Mock LISA Data Challenges: from Challenge 3 to Challenge 4
The Mock LISA Data Challenges are a program to demonstrate LISA data-analysis
capabilities and to encourage their development. Each round of challenges
consists of one or more datasets containing simulated instrument noise and
gravitational waves from sources of undisclosed parameters. Participants
analyze the datasets and report best-fit solutions for the source parameters.
Here we present the results of the third challenge, issued in Apr 2008, which
demonstrated the positive recovery of signals from chirping Galactic binaries,
from spinning supermassive--black-hole binaries (with optimal SNRs between ~ 10
and 2000), from simultaneous extreme-mass-ratio inspirals (SNRs of 10-50), from
cosmic-string-cusp bursts (SNRs of 10-100), and from a relatively loud
isotropic background with Omega_gw(f) ~ 10^-11, slightly below the LISA
instrument noise.Comment: 12 pages, 2 figures, proceedings of the 8th Edoardo Amaldi Conference
on Gravitational Waves, New York, June 21-26, 200
Seeking safety beyond refuge : the impact of immigration and citizenship policy upon refugees in the UK
Western states are concerned about maintaining and securing national borders. Across Europe, one response has been to implement restrictive asylum regimes that prevent âbogusâ applicants and grant refuge only to the âdeservingâ. Alongside these concerns, states are eager to encourage socially cohesive communities. One recent tool adopted by the UK government has been citizenship policy, including English language/life in the UK tests and citizenship ceremonies. By drawing upon in-depth interviews with refugees in Scotland (UK), this paper explores the impact of the current asylum regime and citizenship policies from the perspective of individual voices that are often absent from wider debates. It explores how temporary refugee status impacts upon individualsâ everyday lives including employment and education, and impacts upon children. The data also question the reasons for refugees deciding to become British citizens (or not) and highlight instrumental reasons alongside less tangible factors such as gaining a sense of security. Taking the discussion forward, the study explores some unintended consequences of immigration and citizenship policies in the UK. The research suggests that not only do restrictive asylum policies negatively impact upon refugees and their integration but also serve to elevate fear and uncertainty, which can unintentionally spur individuals to seek naturalisation
PTF11eon/SN2011dh: Discovery of a Type IIb Supernova From a Compact Progenitor in the Nearby Galaxy M51
On May 31, 2011 UT a supernova (SN) exploded in the nearby galaxy M51 (the
Whirlpool Galaxy). We discovered this event using small telescopes equipped
with CCD cameras, as well as by the Palomar Transient Factory (PTF) survey, and
rapidly confirmed it to be a Type II supernova. Our early light curve and
spectroscopy indicates that PTF11eon resulted from the explosion of a
relatively compact progenitor star as evidenced by the rapid shock-breakout
cooling seen in the light curve, the relatively low temperature in early-time
spectra and the prompt appearance of low-ionization spectral features. The
spectra of PTF11eon are dominated by H lines out to day 10 after explosion, but
initial signs of He appear to be present. Assuming that He lines continue to
develop in the near future, this SN is likely a member of the cIIb (compact
IIb; Chevalier and Soderberg 2010) class, with progenitor radius larger than
that of SN 2008ax and smaller than the eIIb (extended IIb) SN 1993J progenitor.
Our data imply that the object identified in pre-explosion Hubble Space
Telescope images at the SN location is possibly a companion to the progenitor
or a blended source, and not the progenitor star itself, as its radius (~10^13
cm) would be highly inconsistent with constraints from our post-explosion
photometric and spectroscopic data
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