Influence of rest on players’ performance and physiological responses during basketball play

Pre-match warm-ups are standard in many sports but the focus has excluded the substitute players. The aim of this research was to investigate the result of inactivity on physiological and performance responses in substitute basketball players during competition. Two basketball players from the second tier of the State League of Queensland, Australia volunteered for this study and were assessed for performance (countermovement jump—CMJ) and physiological (core temperature via ingestible pill; skin temperature at the arm, chest, calf and thigh; heart rate—HR) responses prior to and following a 20-min warm-up, and during the first half of a competitive basketball match (2 × 20-min real time quarters). Warm up resulted in increases in CMJ (~7%), HR (~100 bpm) and core (~0.8 °C) and skin (~1.0 °C) temperatures. Following the warm up and during inactivity, substitute players exhibited a decrease in all responses including CMJ (~13%), HR (~100 bpm), and core (~0.5 °C) and skin (~2.0 °C) temperatures. Rest resulted in reductions in key performance and physiological responses during a competitive match that poses a risk for match strategies. Coaches should consider implementing a warm up to enhance core/skin temperature for substitute players immediately before they engage with competition to optimise player performance

Effects of a 6-month exercise program pilot study on walking economy, peak physiological characteristics, and walking performance in patients with peripheral arterial disease

The purpose of this study was to examine the effects of a 6-month exercise program on submaximal walking economy in individuals with peripheral arterial disease and intermittent claudication (PAD-IC). Participants (n = 16) were randomly allocated to either a control PAD-IC group (CPAD-IC, n = 6) which received standard medical therapy, or a treatment PAD-IC group (TPAD-IC; n = 10) which took part in a supervised exercise program. During a graded treadmill test, physiological responses, including oxygen consumption, were assessed to calculate walking economy during submaximal and maximal walking performance. Differences between groups at baseline and post-intervention were analyzed via Kruskal–Wallis tests. At baseline, CPAD-IC and TPAD-IC groups demonstrated similar walking performance and physiological responses. Postintervention, TPAD-IC patients demonstrated significantly lower oxygen consumption during the graded exercise test, and greater maximal walking performance compared to CPAD-IC. These preliminary results indicate that 6 months of regular exercise improves both submaximal walking economy and maximal walking performance, without significant changes in maximal walking economy. Enhanced walking economy may contribute to physiological efficiency, which in turn may improve walking performance as demonstrated by PAD-IC patients following regular exercise programs

Reliability of the running vertical jump test in female team sport athletes

Injury rates to the lower limb have increased over the past 40 years, coinciding with increases in female sport participation rates. Sport specific tests such as the running vertical jump (RVJ) are utilised for injury risk profiling, however the test-retest reliability is unknown. Objectives: The aim of this study was to investigate the test-retest reliability of the thorax, pelvis and lower limb joint angular kinematics and kinetics for the RVJ test in female team sport athletes. Design: Three-dimensional motion capture with force plate integration was utilised as participants performed five trials on each limb on three separate days. Setting: Testing occurred in a biomechanics laboratory. Participants: Thirty-four females (Australian Rules Football = 15, Netball = 12, Soccer = 7) participated in this study. Main Outcome Measures: Intraclass correlation coefficients (ICC), effect sizes and typical errors (TE) of segment and joint angular kinematics and kinetics were calculated. Results: Poor to excellent reliability (ICC = −0.12 – 0.92), small to large effect sizes (0.00–0.90) and TE (0.02–289.24) were observed across segment and joint angular kinematics and kinetics. Conclusions: The RVJ test is recommended when analysing ground reaction forces and joint angular kinematics in female team sport athletes

The Galactic WN stars: Spectral analyses with line-blanketed model atmospheres versus stellar evolution models with and without rotation

CONTEXT: Very massive stars pass through the Wolf-Rayet (WR) stage before they finally explode. Details of their evolution have not yet been safely established, and their physics are not well understood. Their spectral analysis requires adequate model atmospheres, which have been developed step by step during the past decades and account in their recent version for line blanketing by the millions of lines from iron and iron-group elements. However, only very few WN stars have been re-analyzed by means of line-blanketed models yet. AIMS: The quantitative spectral analysis of a large sample of Galactic WN stars with the most advanced generation of model atmospheres should provide an empirical basis for various studies about the origin, evolution, and physics of the Wolf-Rayet stars and their powerful winds. METHODS: We analyze a large sample of Galactic WN stars by means of the Potsdam Wolf-Rayet (PoWR) model atmospheres, which account for iron line blanketing and clumping. The results are compared with a synthetic population, generated from the Geneva tracks for massive star evolution. RESULTS: We obtain a homogeneous set of stellar and atmospheric parameters for the Galactic WN stars, partly revising earlier results. CONCLUSIONS: Comparing the results of our spectral analyses of the Galactic WN stars with the predictions of the Geneva evolutionary calculations, we conclude that there is rough qualitative agreement. However, the quantitative discrepancies are still severe, and there is no preference for the tracks that account for the effects of rotation. It seems that the evolution of massive stars is still not satisfactorily understood.Comment: 19 pages, 11 figures, A&A, in press, additional Online-material on http://www.astro.physik.uni-potsdam.de/abstracts/galwn.htm

The effect of massive binaries on stellar populations and supernova progenitors

We compare our latest single and binary stellar model results from the Cambridge STARS code to several sets of observations. We examine four stellar population ratios, the number of blue to red supergiants, the number of Wolf-Rayet stars to O supergiants, the number of red supergiants to Wolf-Rayet stars and the relative number of Wolf-Rayet subtypes, WC to WN stars. These four ratios provide a quantitative measure of nuclear burning lifetimes and the importance of mass loss during various stages of the stars' lifetimes. In addition we compare our models to the relative rate of type Ib/c to type II supernovae to measure the amount of mass lost over the entire lives of all stars. We find reasonable agreement between the observationally inferred values and our predicted values by mixing single and binary star populations. However there is evidence that extra mass loss is required to improve the agreement further, to reduce the number of red supergiants and increase the number of Wolf-Rayet stars.Comment: Accepted for publication in MNRAS, 11 pages, 10 figure

Spitzer Space Telescope observations of the Carina Nebula: The steady march of feedback-driven star formation

We report the first results of imaging the Carina Nebula with Spitzer/IRAC, providing a catalog of point sources and YSOs based on SED fits. We discuss several aspects of the extended emission, including dust pillars that result when a clumpy molecular cloud is shredded by massive star feedback. There are few "extended green objects" (EGOs) normally taken as signposts of outflow activity, and none of the HH jets detected optically are seen as EGOs. A population of "extended red objects" tends to be found around OB stars, some with clear bow-shocks. These are dusty shocks where stellar winds collide with flows off nearby clouds. Finally, the relative distributions of O stars and subclusters of YSOs as compared to dust pillars shows that while some YSOs are located within pillars, many more stars and YSOs reside just outside pillar heads. We suggest that pillars are transient phenomena, part of a continuous outwardly propagating wave of star formation driven by massive star feedback. As pillars are destroyed, they leave newly formed stars in their wake, which are then subsumed into the young OB association. Altogether, the current generation of YSOs shows no strong deviation from a normal IMF. The number of YSOs suggests a roughly constant star-formation rate over the past 3Myr, implying that star formation in pillars constitutes an important mechanism to construct unbound OB associations. Accelerated pillars may give birth to O-type stars that, after several Myr, could appear to have formed in isolation.Comment: 25 pages, 15 figures, MNRAS accepte

Learning ‘social responsibility’ in the workplace: conjuring, unsettling, and folding boundaries

This article proceeds from the argument that while the discourse of social responsibility (SR) is increasingly evident in pedagogies circulating through the workplace, its actual practices tend to be obscured beneath complex tensions and moral precepts presented as self-evident. Through an examination of individuals’ learning of SR in the workplace contexts of small enterprise, this discussion asks: How can we consider social responsibility in work, and the project of learning social responsibility in and for work, in more flexible ways that account for its complex enactments in pluralist contexts? The article explores dynamics of responsibility as both response and identity within literature on social responsibility in the workplace, and examines the process of learning SR as a matter of negotiating boundaries to enact response and identity. Drawing from findings of a qualitative study of 25 small enterprise owners engaging a process of learning SR practice, the article explores what are argued to be their boundary practices of conjuring, unsettling and folding boundaries as they developed viable locations and relations of social responsibility in their unique situations

Physical parameters of erupting Luminous Blue Variables: NGC 2363-V1 caught in the act

A quantitative study of the Luminous Blue Variable NGC 2363-V1 in the Magellanic galaxy NGC 2366 (D = 3.44 Mpc) is presented, based on ultraviolet and optical HST/STIS spectroscopy. Contemporary WFPC2 and WHT imaging reveals a modest V-band brightness increase of ~ 0.2 mag per year between 1996 January and 1997 November, reaching V=17.4 mag, corresponding to Mv=-10.4 mag. Subsequently, V1 underwent a similar decrease in V-band brightness, together with a UV brightening of 0.35 mag from 1997 November to 1999 November. The optical spectrum of V1 is dominated by H emission lines, with Fe II, He I and Na I also detected. In the ultraviolet, a forest of Fe absorption features and numerous absorption lines typical of mid-B supergiants are observed. From a spectral analysis with the non-LTE, line-blanketed code of Hillier & Miller (1998), we derive stellar parameters of T*=11kK, R*=420Ro, log(L/Lo)=6.35 during 1997 November, and T*=13kK, R*=315Ro, log(L/Lo)=6.4 for 1999 July. The wind properties of V1 are also exceptional, with Mdot ~ 4.4 x 10e-4 Mo/yr and $v_{\infty} ~$300 km/s, allowing for a clumped wind (filling factor = 0.3), and assuming H/He ~ 4 by number. The presence of Fe lines in the UV and optical spectrum of V1 permits an estimate of the heavy elemental abundance of NGC 2363 from our spectral synthesis. Although some deficiencies remain, allowance for charge exchange reactions in our calculations supports a SMC-like metallicity, that has previously been determined for NGC 2363 from nebular oxygen diagnostics. Considering a variety of possible progenitor stars, V1 has definitely undergone a giant eruption, with a substantial increase in stellar luminosity, radius, and almost certainly mass-loss rate.Comment: 29 pages, 10 figures, Submitted to Ap

Synthetic High-Resolution Line Spectra of Star-Forming Galaxies Below 1200A

We have generated a set of far-ultraviolet stellar libraries using spectra of OB and Wolf-Rayet stars in the Galaxy and the Large and Small Magellanic Cloud. The spectra were collected with the Far Ultraviolet Spectroscopic Explorer and cover a wavelength range from 1003.1 to 1182.7A at a resolution of 0.127A. The libraries extend from the earliest O- to late-O and early-B stars for the Magellanic Cloud and Galactic libraries, respectively. Attention is paid to the complex blending of stellar and interstellar lines, which can be significant, especially in models using Galactic stars. The most severe contamination is due to molecular hydrogen. Using a simple model for the H$_2$ line strength, we were able to remove the molecular hydrogen lines in a subset of Magellanic Cloud stars. Variations of the photospheric and wind features of CIII 1176, OVI 1032, 1038, PV 1118, 1128, and SIV 1063, 1073, 1074 are discussed as a function of temperature and luminosity class. The spectral libraries were implemented into the LavalSB and Starburst99 packages and used to compute a standard set of synthetic spectra of star-forming galaxies. Representative spectra are presented for various initial mass functions and star formation histories. The valid parameter space is confined to the youngest ages of less than 10 Myr for an instantaneous burst, prior to the age when incompleteness of spectral types in the libraries sets in. For a continuous burst at solar metallicity, the parameter space is not limited. The suite of models is useful for interpreting the restframe far-ultraviolet in local and high-redshift galaxies.Comment: 33 pages including 13 figures, accepted for publication in Ap

Functional role of T-cell receptor nanoclusters in signal initiation and antigen discrimination

Antigen recognition by the T-cell receptor (TCR) is a hallmark of the adaptive immune system. When the TCR engages a peptide bound to the restricting major histocompatibility complex molecule (pMHC), it transmits a signal via the associated CD3 complex. How the extracellular antigen recognition event leads to intracellular phosphorylation remains unclear. Here, we used single-molecule localization microscopy to quantify the organization of TCR–CD3 complexes into nanoscale clusters and to distinguish between triggered and nontriggered TCR–CD3 complexes. We found that only TCR–CD3 complexes in dense clusters were phosphorylated and associated with downstream signaling proteins, demonstrating that the molecular density within clusters dictates signal initiation. Moreover, both pMHC dose and TCR–pMHC affinity determined the density of TCR–CD3 clusters, which scaled with overall phosphorylation levels. Thus, TCR–CD3 clustering translates antigen recognition by the TCR into signal initiation by the CD3 complex, and the formation of dense signaling-competent clusters is a process of antigen discrimination