A new tool for the performance analysis of massively parallel computer systems

We present a new tool, GPA, that can generate key performance measures for very large systems. Based on solving systems of ordinary differential equations (ODEs), this method of performance analysis is far more scalable than stochastic simulation. The GPA tool is the first to produce higher moment analysis from differential equation approximation, which is essential, in many cases, to obtain an accurate performance prediction. We identify so-called switch points as the source of error in the ODE approximation. We investigate the switch point behaviour in several large models and observe that as the scale of the model is increased, in general the ODE performance prediction improves in accuracy. In the case of the variance measure, we are able to justify theoretically that in the limit of model scale, the ODE approximation can be expected to tend to the actual variance of the model

Are Current Physical Match Performance Metrics in Elite Soccer Fit for Purpose or is the Adoption of an Integrated Approach Needed?

Time-motion analysis is a valuable data-collection technique used to quantify the physical match performance of elite soccer players. For over 40 years researchers have adopted a 'traditional' approach when evaluating match demands by simply reporting the distance covered or time spent along a motion continuum of walking through to sprinting. This methodology quantifies physical metrics in isolation without integrating other factors and this ultimately leads to a one-dimensional insight into match performance. Thus, this commentary proposes a novel 'integrated' approach that focuses on a sensitive physical metric such as high-intensity running but contextualizes this in relation to key tactical activities for each position and collectively for the team. In the example presented, the 'integrated' model clearly unveils the unique high-intensity profile that exists due to distinct tactical roles, rather than one-dimensional 'blind' distances produced by 'traditional' models. Intuitively this innovative concept may aid the coaches understanding of the physical performance in relation to the tactical roles and instructions given to the players. Additionally, it will enable practitioners to more effectively translate match metrics into training and testing protocols. This innovative model may well aid advances in other team sports that incorporate similar intermittent movements with tactical purpose. Evidence of the merits and application of this new concept are needed before the scientific community accepts this model as it may well add complexity to an area that conceivably needs simplicity

Offsets and the Path to Carbon Neutrality in Higher Education and Study Abroad

Professors Paul Sylvester, Early & Middle Grades Education, and Michael Di Giovine, Anthropology, in conversation with Bradley Flamm - Offsets and the Path to Carbon Neutrality in Higher Education and Study Abroa

Match physical performance of elite female soccer players during international competition.

The purpose of the present study was to provide a detailed analysis of the physical demands of competitive international female soccer match-play. A total of 148 individual match observations were undertaken on 107 outfield players competing in competitive international matches during the 2011-2012 and 2012-2013 seasons, using a computerized tracking system (Prozone Sports Ltd., Leeds, England). Total distance (TD) and total high-speed running distances (THSR) were influenced by playing position, with central midfielders (CM) completing the highest (10985±706 m and 2882±500 m) and central defenders (CD) the lowest (9489±562 m and 1901±268 m) distances, respectively. Greater total very high-speed running (TVHSR) distances were completed when a team was without (399±143 m) compared to with (313±210 m) possession of the ball. The majority of sprints were over short distances with 76 % and 95 % being less than 5 m and 10 m, respectively. Between half reductions in physical performance were present for all variables, independent of playing position. The current study provides novel findings regarding the physical demands of different playing positions in competitive international female match-play and provides important insights for physical coaches preparing elite female players for competition

Energy and angular momentum balance in wall-bounded superfluid turbulence

A superfluid in the absence of the viscous normal component should be the best realization of an ideal inviscid Euler fluid. As expressed by d'Alembert's famous paradox, an ideal fluid does not exert drag on bodies past which it flows, or in other words, it does not exchange momentum with them. Also, the flow of an ideal fluid does not dissipate kinetic energy. We study experimentally whether these properties apply to the flow of superfluid 3He-B in a rotating cylinder at low temperatures. It is found that ideal behavior is broken by quantum turbulence, which leads to substantial energy dissipation, as observed also earlier. Here we show that remarkably, nearly ideal behavior is preserved with respect to the angular-momentum exchange between the superfluid and its container, i.e., the drag almost disappears in the zero-temperature limit. This mismatch between energy and angular-momentum transfer results in a new physical situation where the proper description of wall-bounded quantum turbulence requires two effective friction parameters, one for energy dissipation and another for momentum coupling, which become substantially different at very low temperatures.Comment: 7 pages, 3 figure

Interpreting physical performance in professional soccer match-play: Should we be more pragmatic in our approach?

Academic and practitioner interest in the physical performance of male professional soccer players in the competition setting determined via time-motion analyses has grown substantially over the last four decades leading to a substantial body of published research and aiding development of a more systematic evidence-based framework for physical conditioning. Findings have forcibly shaped contemporary opinions in the sport with researchers and practitioners frequently emphasising the important role that physical performance plays in match outcomes. Time-motion analyses have also influenced practice as player conditioning programmes can be tailored according to the different physical demands identified across individual playing positions. Yet despite a more systematic approach to physical conditioning, data indicate that even at the very highest standards of competition, the contemporary player is still susceptible to transient and end-game fatigue. Over the course of this article, the author suggests that a more pragmatic approach to interpreting the current body of time-motion analysis data and its application in the practical setting is nevertheless required. Examples of this are addressed using findings in the literature to examine: a) the association between competitive physical performance and ‘success’ in professional soccer, b) current approaches to interpreting differences in time-motion analysis data across playing positions and, c) whether data can realistically be used to demonstrate the occurrence of fatigue in match-play. Gaps in the current literature and directions for future research are also identified

A DISPLACED SUPERMASSIVE BLACK HOLE IN M87

Isophotal analysis of M87, using data from the Advanced Camera for Surveys, reveals a projected displacement of 6.8 +/- 0.8 pc (similar to 0 ''.1) between the nuclear point source (presumed to be the location of the supermassive black hole, SMBH) and the photo-center of the galaxy. The displacement is along a position angle of 307 degrees +/- 17 degrees and is consistent with the jet axis. This suggests the active SMBH in M87 does not currently reside at the galaxy center of mass, but is displaced in the counter-jet direction. Possible explanations for the displacement include orbital motion of an SMBH binary, gravitational perturbations due to massive objects ( e. g., globular clusters), acceleration by an asymmetric or intrinsically one-sided jet, and gravitational recoil resulting from the coalescence of an SMBIIbinary. The displacement direction favors the latter two mechanisms. However, jet asymmetry is only viable, at the observed accretion rate, for a jet age of >0.1 Gyr and if the galaxy restoring force is negligible. This could be the case in the low-density core of M87. A moderate recoil similar to 1Myr ago might explain the disturbed nature of the nuclear gas disk, could be aligned with the jet axis, and can produce the observed offset. Alternatively, the displacement could be due to residual oscillations resulting from a large recoil that occurred in the aftermath of a major merger <= 1 Gyr ago

Borders and Catastrophe: lessons from COVID-19 for the European Green Deal

This article considers how the European Union and Member States’ responses to the COVID-19 crisis in the first half of 2020 could inform climate action in Europe, and particularly the resumption of actions on the EGD. It first outlines the EU’s public health and economic responses to COVID-19 and Europe’s role in the global response to the pandemic. We find that, based on the challenges and successes of all these responses, a strong argument can be made for ‘more Europe’ – greater integration, and stronger EU-level institutions – to lead and govern the COVID-19 response. This has direct lessons for the governance and scope of future climate action

New Constraints on Mass-Dependent Disruption of Star Clusters in M51

We use UBVI,Ha images of the Whirlpool galaxy, M51, taken with the ACS and WFPC2 cameras on the Hubble Space Telescope (HST) to select star clusters, and to estimate their masses and ages by comparing their observed colors with predictions from population synthesis models. We construct the mass function of intermediate age (1-4x10^8 yr) clusters, and find that it is well described by a power law, psi(M) propto M^beta, with beta=-2.1 +/- 0.2, for clusters more massive than approximately 6x10^3 Msun. This extends the mass function of intermediate age clusters in M51 to masses lower by nearly a factor of five over previous determinations. The mass function does not show evidence for curvature at either the high or low mass end. This shape indicates that there is no evidence for the earlier disruption of lower mass clusters compared with their higher mass counterparts (i.e., no mass-dependent disruption) over the observed range of masses and ages, or for a physical upper mass limit Mc with which clusters in M51 can form. These conclusions differ from previous suggestions based on poorer-quality HST observations. We discuss their implications for the formation and disruption of the clusters. Ages of clusters in two "feathers," stellar features extending from the outer portion of a spiral arm, show that the feather with a larger pitch angle formed earlier, and over a longer period, than the other.Comment: 24 pages, 7 figures; to be published in ApJ, 727, 8

Cluster model of glass transition in simple liquids

On the basis of microscopic statistical mechanics of simple liquids the orientational interaction between clusters consisting of a particle and its nearest neighbors is estimated. It is shown that there are ranges of density and temperature where the interaction changes sign as a function of a radius of a cluster. The model of interacting cubic and icosahedral clusters is proposed and solved in mean-field replica symmetric approximation. It is shown that the glass order parameter grows smoothly upon cooling, the transition temperature being identified with the temperature of the replica symmetry breaking. It is shown that upon cooling a Lennard-Jones system, cubic clusters freeze first. The transition temperature for icosahedral clusters is about ten per cent lower. So the local structure of Lennard-Jones glass in the vicinity of glass transition should be most probably cubic.Comment: 4 pages, 3 figure