Dietary nitrate reduces muscle metabolic perturbation and improves exercise tolerance in hypoxia

The definitive version is available at www3.interscience.wiley.comExercise in hypoxia is associated with reduced muscle oxidative function and impaired exercise tolerance. We hypothesised that dietary nitrate supplementation (which increases plasma [nitrite] and thus NO bioavailability) would ameliorate the adverse effects of hypoxia on muscle metabolism and oxidative function. In a double-blind, randomised crossover study, nine healthy subjects completed knee-extension exercise to the limit of tolerance (T(lim)), once in normoxia (20.9% O(2); CON) and twice in hypoxia (14.5% O(2)). During 24 h prior to the hypoxia trials, subjects consumed 0.75 L of nitrate-rich beetroot juice (9.3 mmol nitrate; H-BR) or 0.75 L of nitrate-depleted beetroot juice as a placebo (0.006 mmol nitrate; H-PL). Muscle metabolism was assessed using calibrated (31)P-MRS. Plasma [nitrite] was elevated (P < 0.01) following BR (194 ± 51 nm) compared to PL (129 ± 23 nm) and CON (142 ± 37 nM). T(lim) was reduced in H-PL compared to CON (393 ± 169 vs. 471 ± 200 s; P < 0.05) but was not different between CON and H-BR (477 ± 200 s). The muscle [PCr], [P(i)] and pH changed at a faster rate in H-PL compared to CON and H-BR. The [PCr] recovery time constant was greater (P < 0.01) in H-PL (29 ± 5 s) compared to CON (23 ± 5 s) and H-BR (24 ± 5 s). Nitrate supplementation reduced muscle metabolic perturbation during exercise in hypoxia and restored exercise tolerance and oxidative function to values observed in normoxia. The results suggest that augmenting the nitrate-nitrite-NO pathway may have important therapeutic applications for improving muscle energetics and functional capacity in hypoxia

b-Quark Production in Proton-Proton Collisions at Center of Mass Energies of 510 GeV in the PHENIX Detector at RHIC

Heavy flavor quarks are an important probe of the initial state of the Quark Gluon Plasma formed in heavy-ion collisions. Bottom and charm quarks are produced early in the collision, primarily through hard interactions, and experience the full time evolution of the medium. Understanding bottom quark production in proton-proton collisions gives a baseline reference for studying larger collision systems. The measurement of the b-quark production ∆φ correlations gives insight into the b-quark production mechanisms. The signal can be isolated by taking advantage of the properties of neutral B meson oscillations in the invariant mass region of 5-10 GeV. Measuring like-sign dimuons within this mass range provides an enriched bottom signal with a minimal amount of open charm background and without any contributions from quarkonia or Drell-Yan pairs. b-quark production will be measured through the semi-leptonic decay like-sign dimuon signal, in the rapidity range 1.2 \u3c |y| \u3c 2.2 and at √s = 510 GeV from data recorded in 2013 at the PHENIX experiment. The measured total cross section is 14.9 ± 0.7(stat) ± 2.0(type B sys.) ± 3.4(type C sys.)[μb]

Measurements of μμ pairs from open heavy flavor and Drell-Yan in p+p collisions at s =200 GeV

PHENIX reports differential cross sections of μμ pairs from semileptonic heavy-flavor decays and the Drell-Yan production mechanism measured in p+p collisions at s=200 GeV at forward and backward rapidity (1.2&lt;|η|&lt;2.2). The μμ pairs from cc, bb, and Drell-Yan are separated using a template fit to unlike- and like-sign muon pair spectra in mass and pT. The azimuthal opening angle correlation between the muons from cc and bb decays and the pair-pT distributions are compared to distributions generated using pythia and powheg models, which both include next-to-leading order processes. The measured distributions for pairs from cc are consistent with pythia calculations. The cc data present narrower azimuthal correlations and softer pT distributions compared to distributions generated from powheg. The bb data are well described by both models. The extrapolated total cross section for bottom production is 3.75±0.24(stat)±0.500.35(syst)±0.45(global) [μb], which is consistent with previous measurements at the Relativistic Heavy Ion Collider in the same system at the same collision energy and is approximately a factor of 2 higher than the central value calculated with theoretical models. The measured Drell-Yan cross section is in good agreement with next-to-leading-order quantum-chromodynamics calculations

Evidence in support of the call to ban the tackle and harmful contact in school rugby: a response to World Rugby

In a paper published in BJSM (June 2016), World Rugby employees Ross Tucker and Martin Raftery and a third coauthor Evert Verhagen took issue with the recent call to ban tackling in school rugby in the UK and Ireland. That call (to ban tackling) was supported by a systematic review published in BJSM. Tucker et al claim that: (1) the mechanisms and risk factors for injury along with the incidence and severity of injury in youth rugby union have not been thoroughly identified or understood; (2) rugby players are at no greater risk of injury than other sports people, (3) this is particularly the case for children under 15 years and (4) removing the opportunity to learn the tackle from school pupils might increase rates of injuries. They conclude that a ban ‘may be unnecessary and may also lead to unintended consequences such as an increase in the risk of injury later in participation.’ Here we aim to rebut the case by Tucker et al. We share new research that extends the findings of our original systematic review and meta-analysis. A cautionary approach requires the removal of the tackle from school rugby as the quickest and most effective method of reducing high injury rates in youth rugby, a public health priority

Pseudorapidity Dependence of Particle Production and Elliptic Flow in Asymmetric Nuclear Collisions of p+Al, p+Au, d+Au, and ^{3}He+Au at sqrt[s_{NN}]=200 GeV.

Asymmetric nuclear collisions of p+Al, p+Au, d+Au, and ^{3}He+Au at sqrt[s_{NN}]=200  GeV provide an excellent laboratory for understanding particle production, as well as exploring interactions among these particles after their initial creation in the collision. We present measurements of charged hadron production dN_{ch}/dη in all such collision systems over a broad pseudorapidity range and as a function of collision multiplicity. A simple wounded quark model is remarkably successful at describing the full data set. We also measure the elliptic flow v_{2} over a similarly broad pseudorapidity range. These measurements provide key constraints on models of particle emission and their translation into flow

Tackle-related injury rates and nature of injuries in South African Youth Week tournament rugby union players (under-13 to under-18): an observational cohort study.

OBJECTIVES: The tackle situation is most often associated with the high injury rates in rugby union. Tackle injury epidemiology in rugby union has previously been focused on senior cohorts but less is known about younger cohorts. The aim of this study was to report on the nature and rates of tackle-related injuries in South African youth rugby union players representing their provinces at national tournaments. DESIGN: Observational cohort study. SETTING: Four South African Youth Week tournaments (under-13 Craven Week, under-16 Grant Khomo Week, under-18 Academy Week, under-18 Craven Week). PARTICIPANTS: Injury data were collected from 3652 youth rugby union players (population at risk) in 2011 and 2012. OUTCOME MEASURES: Tackle-related injury severity ('time-loss' and 'medical attention'), type and location, injury rate per 1000 h (including 95% CIs). Injury rate ratios (IRR) were calculated and modelled using a Poisson regression. A χ(2) analysis was used to detect linear trends between injuries and increasing match quarters. RESULTS: The 2012 under-13 Craven Week had a significantly greater 'time-loss' injury rate when compared with the 2012 under-18 Academy Week (IRR=4.43; 95% CI 2.13 to 9.21, p<0.05) and under-18 Craven Week (IRR=3.52; 95% CI 1.54 to 8.00, p<0.05). The Poisson regression also revealed a higher probability of 'overall' ('time-loss' and 'medical attention' combined) and 'time-loss' tackle-related injuries occurring at the under-13 Craven Week. The proportion of 'overall' and 'time-loss' injuries increased significantly with each quarter of the match when all four tournaments were combined (p<0.05). CONCLUSIONS: There was a difference in the tackle-related injury rate between the under-13 tournament and the two under-18 tournaments, and the tackle-related injury rate was higher in the final quarter of matches. Ongoing injury surveillance is required to better interpret these findings. Injury prevention strategies targeting the tackle may only be effective once the rate and nature of injuries have been accurately determined

Measurements of double-helicity asymmetries in inclusive J/ψJ/\psi production in longitudinally polarized p+pp+p collisions at s=510\sqrt{s}=510 GeV

We report the double helicity asymmetry, $A_{LL}^{J/\psi}$, in inclusive $J/\psi$ production at forward rapidity as a function of transverse momentum $p_T$ and rapidity $|y|$. The data analyzed were taken during $\sqrt{s}=510$ GeV longitudinally polarized $p$$+$$p$ collisions at the Relativistic Heavy Ion Collider (RHIC) in the 2013 run using the PHENIX detector. At this collision energy, $J/\psi$ particles are predominantly produced through gluon-gluon scatterings, thus $A_{LL}^{J/\psi}$ is sensitive to the gluon polarization inside the proton. We measured $A_{LL}^{J/\psi}$ by detecting the decay daughter muon pairs $\mu^+ \mu^-$ within the PHENIX muon spectrometers in the rapidity range $1.2<|y|<2.2$. In this kinematic range, we measured the $A_{LL}^{J/\psi}$ to be $0.012 \pm 0.010$~(stat)~$\pm$~$0.003$(syst). The $A_{LL}^{J/\psi}$ can be expressed to be proportional to the product of the gluon polarization distributions at two distinct ranges of Bjorken $x$: one at moderate range $x \approx 0.05$ where recent RHIC data of jet and $\pi^0$ double helicity spin asymmetries have shown evidence for significant gluon polarization, and the other one covering the poorly known small-$x$ region $x \approx 2\times 10^{-3}$. Thus our new results could be used to further constrain the gluon polarization for $x< 0.05$.Comment: 335 authors, 10 pages, 4 figures, 3 tables, 2013 data. Version accepted for publication by Phys. Rev. D. Plain text data tables for the points plotted in figures for this and previous PHENIX publications are (or will be) publicly available at http://www.phenix.bnl.gov/papers.htm

L\'evy-stable two-pion Bose-Einstein correlations in sNN=200\sqrt{s_{_{NN}}}=200 GeV Au++Au collisions

We present a detailed measurement of charged two-pion correlation functions in 0%-30% centrality $\sqrt{s_{_{NN}}}=200$ GeV Au$+$Au collisions by the PHENIX experiment at the Relativistic Heavy Ion Collider. The data are well described by Bose-Einstein correlation functions stemming from L\'evy-stable source distributions. Using a fine transverse momentum binning, we extract the correlation strength parameter $\lambda$, the L\'evy index of stability $\alpha$ and the L\'evy length scale parameter $R$ as a function of average transverse mass of the pair $m_T$. We find that the positively and the negatively charged pion pairs yield consistent results, and their correlation functions are represented, within uncertainties, by the same L\'evy-stable source functions. The $\lambda(m_T)$ measurements indicate a decrease of the strength of the correlations at low $m_T$. The L\'evy length scale parameter $R(m_T)$ decreases with increasing $m_T$, following a hydrodynamically predicted type of scaling behavior. The values of the L\'evy index of stability $\alpha$ are found to be significantly lower than the Gaussian case of $\alpha=2$, but also significantly larger than the conjectured value that may characterize the critical point of a second-order quark-hadron phase transition.Comment: 448 authors, 25 pages, 11 figures, 4 tables, 2010 data. v2 is version accepted for publication in Phys. Rev. C. Plain text data tables for the points plotted in figures for this and previous PHENIX publications are (or will be) publicly available at http://www.phenix.bnl.gov/papers.htm