158 research outputs found
Double Longitudinal Spin Asymmetries of Inclusive Charged Pion Production in Polarized p+p Collisions at 200 GeV
A primary goal of the STAR Spin program at RHIC is the measurement of the
polarized gluon distribution function , which can be obtained from a
global analysis incorporating measurements of the double spin asymmetry A_{LL}
in various final state channels of polarized p+p collisions. Final states with
large production cross sections such as inclusive jet and hadron production are
analyzed as the program moves towards the measurement of A_{LL} in the
theoretically clean channel of prompt photon production. The channels p+p ->
pi^{+/-} + X are unique in that the ordering of the measurements of A_{LL} in
these two channels is sensitive to the sign of Delta G. Moreover, STAR has
already established the procedure for the identification of charged pions and
the calculation of their production cross-sections over a broad kinematic
range. This contribution will present first measurements of double longitudinal
spin asymmetries for inclusive charged pion production extracted from 3 pb^{-1}
of data at sqrt{s}=200 GeV and 50% beam polarizations. The asymmetries are
calculated over the transverse momentum region 2<p_T<10 GeV/c and compared with
theoretical predictions incorporating several gluon polarization scenarios. A
systematic bias introduced by the selection of charged pions from events
satisfying electromagnetic energy triggers will be discussed and estimated
using Monte Carlo.Comment: 4 pages, 3 figures, contribution to the Proceedings of the 17th
International Spin Physics Symposium (SPIN 2006), Kyoto, Japan, October 2-7,
200
Alterations and Specifications of Excess Post-Exercise Oxygen Consumption: A Review
This review describes oxygen consumption, both in terms of a goal of weight management and aerobic training. It introduces excess postexercise oxygen consumption (EPOC) and the benefits that can come from it. EPOC can aid in weight management as a means to continue to expend energy even after exercise has ceased. This review also discusses the many determinants of EPOC and analyzes the effects of various conditions on the elevated consumption. Such conditions include duration and intensity of exercise, training status, and supplementation. Later discussed are the possible underlying mechanisms and how they are responsible for EPOC. Although they have yet to be well-understood, these mechanisms provide insight into how EPOC is facilitated and why it occurs at all. More research is being conducted in attempts to better understand this concept and how EPOC can be advantageous to our human health.
Consistent aerobic exercise leads to many health benefits such as a positive impact on blood lipid levels and blood pressure, as well as increased energy expenditure for healthy weight management. Additionally, regular aerobic exercise can positively affect mental health, such as reducing depression and anxiety (Mersy, 1991). In general, aerobic exercise decreases the risk of the development of cardiovascular disorders, or disorders that affect the heart, blood vessels, or both. Given the significant burden of cardiovascular disease, aerobic exercise is a commonly prescribed lifestyle modification and is therefore important to fully understand.
Regular aerobic exercise causes the body to increase its oxygen consumption, otherwise known as its VO2. The consumption of oxygen fuels mitochondrial activity within muscle cells to produce ATP, the primary energy currency of all cells. During exercise, increased ATP is necessary in order to fuel contraction-relaxation cycles of muscles that together allow for body movement. With prolonged activity, the substrate for oxidative metabolism can come from stored energy sources, promoting weight loss. Ultimately it is the mass balance of energy intake versus energy expenditure that determines whether one will gain, lose, or maintain weight
Hadron plus photon production in polarized hadronic collisions at next-to-leading order accuracy
We compute the next-to-leading order QCD corrections to the polarized (and
unpolarized) cross sections for the production of a hadron accompanied by an
opposite-side prompt photon. This process, being studied at RHIC, permits us to
reconstruct partonic kinematics using experimentally measurable variables. We
study the correlation between the reconstructed momentum fractions and the true
partonic ones, which in the polarized case might allow us to reveal the
spin-dependent gluon distribution with a higher precision.Comment: 18 figures included. New version, discussion about polarized
asymmetries extended, 7 new figures, new reference
Effects of Single-Dose Dietary Nitrate on Oxygen Consumption During and After Maximal and Submaximal Exercise in Healthy Humans
International Journal of Exercise Science 11(3): 214-225, 2018. Dietary nitrate (NO3-) has been shown to reduce oxygen consumption (VO2) during moderate to high-intensity (e.g. time to fatigue, time trials) exercise and often in trained athletes. However, less is known regarding prolonged exercise and the potential impact of NO3- on post-exercise excess oxygen consumption (EPOC), particularly in untrained individuals, who may have different metabolic goals during exercise than trained individuals. We tested the hypothesis that acute nitrate supplementation in the form of beet root juice will significantly decrease both VO2 during maximal exercise and EPOC in both maximal and submaximal exercise trials. Eight young, moderately active, healthy males (age: 24.8±1.4 years, body mass index: 23.7±0.4 kg/m2; VO2max: 34.2±3.9 ml/kg/min) performed step-wise maximal cycle exercise (n=4) and prolonged submaximal cycle exercise (n=6) (45 min; 38±2% of max work rate) in control (anti-bacterial mouthwash) and acute NO3– supplemented conditions [70ml concentrated beet root juice (0.4g NO3-), 2 hrs prior to exercise] on separate occasions. Measurements of VO2 (indirect calorimetry), arterial blood pressure (MAP; sphygmomanometry), and heart rate (HR; ECG) were made before, during, and following exercise bouts. NO3- reduced MAP at rest ~1-3mmHg. However, NO3- had no impact on VO2 during maximal (VO2max, Ctrl: 34.2±3.9 ml/kg/min vs NO3-: 31.7±4.4 ml/kg/min), submaximal exercise (average of min 25-45, Ctrl: 24.6±2.4 ml/kg/min vs NO3-: 26.8±3.3 ml/kg/min) or EPOC (area under the curve, Ctrl: 0.57±0.24 L vs NO3-: 0.66±0.16 L). Thus, while NO3- supplementation may have performance benefits in elite athletes exercising at high intensities, in recreationally active males, there appears to be little impact on changes in VO2 due to maximal or submaximal prolonged exercise
Scalability in the Presence of Variability
Supercomputers are used to solve some of the world’s most computationally demanding
problems. Exascale systems, to be comprised of over one million cores and capable of 10^18
floating point operations per second, will probably exist by the early 2020s, and will provide
unprecedented computational power for parallel computing workloads. Unfortunately,
while these machines hold tremendous promise and opportunity for applications in High
Performance Computing (HPC), graph processing, and machine learning, it will be a major
challenge to fully realize their potential, because to do so requires balanced execution across
the entire system and its millions of processing elements. When different processors take different
amounts of time to perform the same amount of work, performance imbalance arises,
large portions of the system sit idle, and time and energy are wasted. Larger systems incorporate
more processors and thus greater opportunity for imbalance to arise, as well as larger
performance/energy penalties when it does. This phenomenon is referred to as performance
variability and is the focus of this dissertation.
In this dissertation, we explain how to design system software to mitigate variability
on large scale parallel machines. Our approaches span (1) the design, implementation, and
evaluation of a new high performance operating system to reduce some classes of performance
variability, (2) a new performance evaluation framework to holistically characterize
key features of variability on new and emerging architectures, and (3) a distributed modeling
framework that derives predictions of how and where imbalance is manifesting in order to
drive reactive operations such as load balancing and speed scaling. Collectively, these efforts
provide a holistic set of tools to promote scalability through the mitigation of variability
Extraction of Spin-Dependent Parton Densities and Their Uncertainties
We discuss techniques and results for the extraction of the nucleon's
spin-dependent parton distributions and their uncertainties from data for
polarized deep-inelastic lepton-nucleon and proton-proton scattering by means
of a global QCD analysis. Computational methods are described that
significantly increase the speed of the required calculations to a level that
allows to perform the full analysis consistently at next-to-leading order
accuracy. We examine how the various data sets help to constrain different
aspects of the quark, anti-quark, and gluon helicity distributions. Uncertainty
estimates are performed using both the Lagrange multiplier and the Hessian
approaches. We use the extracted parton distribution functions and their
estimated uncertainties to predict spin asymmetries for high-transverse
momentum pion and jet production in polarized proton-proton collisions at 500
GeV center-of-mass system energy at BNL-RHIC, as well as for W boson
production.Comment: 25 pages, 15 eps figures, v2: minor changes, final version to appear
in Phys. Rev.
Improving the dE/dx calibration of the STAR TPC for the high-pT hadron identification
We derive a method to improve particle identification (PID) at high
transverse momentum () using the relativistic rise of the ionization
energy loss () when charged particles traverse the Time Projection
Chamber (TPC) at STAR. Electrons triggered and identified by the Barrel
Electro-Magnetic Calorimeter (BEMC), pure protons and pions from (), and
decays are used to obtain the value and
its width at given . We found that the deviation of the
from the Bichsel function can be up to () in p+p
collisions at GeV taken and subsequently calibrated in year
2005. The deviation is approximately a function of independent of
particle species and can be described with a function of . The deviations obtained with this method are used to
re-calibrate the data sample from p+p collision for physics analysis of
identified hadron spectra and their correlations up to transverse momentum of
15 GeV/. The ratio of (dominantly from -conversion) is
also used to correct the residual asymmetry in the negative and positive
charged hadrons due to momentun distortion in the STAR TPC.Comment: 18pages, 10 figure
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