1,269 research outputs found
Effect of onset threshold on kinetic and kinematic variables of a weightlifting derivative containing a first and second pull
This study sought to determine the effect of different movement onset thresholds on both the reliability and absolute values of performance variables during a weightlifting derivative containing both a first and second pull. Fourteen men (age: 25.21 ± 4.14 years; body mass: 81.1 ± 11.4 kg; and 1 repetition maximum [1RM] power clean: 1.0 ± 0.2 kg·kg) participated in this study. Subjects performed the snatch-grip pull with 70% of their power clean 1RM, commencing from the mid-shank, while isolated on a force platform. Two trials were performed enabling within-session reliability of dependent variables to be determined. Three onset methods were used to identify the initiation of the lift (5% above system weight [SW], the first sample above SW, or 10 N above SW), from which a series of variables were extracted. The first peak phase peak force and all second peak phase kinetic variables were unaffected by the method of determining movement onset; however, several remaining second peak phase variables were significantly different between methods. First peak phase peak force and average force achieved excellent reliability regardless of the onset method used (coefficient of variation [CV] 0.90). Similarly, during the second peak phase, peak force, average force, and peak velocity achieved either excellent or acceptable reliability (CV 0.80) in all 3 onset conditions. The reliability was generally reduced to unacceptable levels at the first sample and 10 N method across all first peak measures except peak force. When analyzing a weightlifting derivative containing both a first and second pull, the 5% method is recommended as the preferred option of those investigated
Price Discovery and the Accuracy of Consolidated Data Feeds in the U.S. Equity Markets
Both the scientific community and the popular press have paid much attention
to the speed of the Securities Information Processor, the data feed
consolidating all trades and quotes across the US stock market. Rather than the
speed of the Securities Information Processor, or SIP, we focus here on its
accuracy. Relying on Trade and Quote data, we provide various measures of SIP
latency relative to high-speed data feeds between exchanges, known as direct
feeds. We use first differences to highlight not only the divergence between
the direct feeds and the SIP, but also the fundamental inaccuracy of the SIP.
We find that as many as 60 percent or more of trades are reported out of
sequence for stocks with high trade volume, therefore skewing simple measures
such as returns. While not yet definitive, this analysis supports our
preliminary conclusion that the underlying infrastructure of the SIP is
currently unable to keep pace with the trading activity in today's stock
market.Comment: 18 pages, 20 figures, 2 table
Horizontal Lloyd mirror patterns from straight and curved nonlinear internal waves
Author Posting. © Acoustical Society of America, 2012. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 131 (2012): 1689-1700, doi:10.1121/1.3666004.Experimental observations and theoretical studies show that nonlinear internal waves occur widely in shallow water and cause acoustic propagation effects including ducting and mode coupling. Horizontal ducting results when acoustic modes travel between internal wave fronts that form waveguide boundaries. For small grazing angles between a mode trajectory and a front, an interference pattern may arise that is a horizontal Lloyd mirror pattern. An analytic description for this feature is provided along with comparisons between results from the formulated model predicting a horizontal Lloyd mirror pattern and an adiabatic mode parabolic equation. Different waveguide models are considered, including boxcar and jump sound speed profiles where change in sound speed is assumed 12 m/s. Modifications to the model are made to include multiple and moving fronts. The focus of this analysis is on different front locations relative to the source as well as on the number of fronts and their curvatures and speeds. Curvature influences mode incidence angles and thereby changes the interference patterns. For sources oriented so that the front appears concave, the areas with interference patterns shrink as curvature increases, while convexly oriented fronts cause patterns to expand.The authors thank the Office of Naval Research for
funding this work. Additionally, the first author is supported
through an ONR Ocean Acoustics Traineeship
Relationship between physical performance testing results and peak running intensity during professional rugby league match play
The purpose of this study was to examine the relationship between individual athletes' physical characteristics and both the peak running intensities and the decline in peak running intensities during competition. Twenty-two professional rugby league athletes (age; 24.1 ± 4.0 years, body mass; 101.4 ± 9.5 kg) underwent a series of physical testing procedures. Peak running intensity was determined using a moving average technique, applied to the speed (m·min-1), acceleration/deceleration (m·s-2) and metabolic power (W·kg-1) during competition, across 10 different durations. The power law relationship was then established, yielding an intercept and slope for the movement variables. Mixed linear models were then used to determine the relationship between physical characteristics and intercept and slope values. There were large, positive relationships between a player’s maximal speed and both peak running speeds (ES = 0.56, 90% CI: 0.20 to 0.78) and metabolic power (0.57, 0.21 to 0.79) during competition. In contrast, there were large, negative associations between maximal speed and the rate of decline in running speed (-0.60, -0.81 to -0.27) and metabolic power (-0.65, -0.83 to -0.32) during competition. Similarly, there were negative associations between relative squat strength and the rate of decline in running speed (moderate: -0.41, -0.69 to -0.04) and metabolic power (large: -0.53, -0.77 to -0.17) during competition. The findings of this study demonstrate that a players running intensity during competition is underpinned by the individual athletes physiological qualities. Athletes demonstrating higher maximal speeds in testing were able to maintain higher running intensities over short durations, but had a greater decrease in running intensity as duration increased
Small intestinal injuries in mice caused by a new toxin, Azaspiracid, isolated from Irish mussels
Pathological changes of the small intestine caused by a new toxin, azaspiracid, from Irish mussels were studied. Human poisoning cases included both diarrhetic shellfish and paralitic shellfish poisoning symptoms. The present paper focused on the former. Injuries were observed in the Upper part of the small intestine, where lamina propria in the villi became atrophied at the initial stage, followed by desquamation of epithelial cells and shortening of villi. The injuries were different from the DSP toxin okadaic acid; 1) they developed very slowly after a lag time of about 3 hr, 2) recovery was very late, 3) initial target and process were different
Simulating chemistry efficiently on fault-tolerant quantum computers
Quantum computers can in principle simulate quantum physics exponentially
faster than their classical counterparts, but some technical hurdles remain.
Here we consider methods to make proposed chemical simulation algorithms
computationally fast on fault-tolerant quantum computers in the circuit model.
Fault tolerance constrains the choice of available gates, so that arbitrary
gates required for a simulation algorithm must be constructed from sequences of
fundamental operations. We examine techniques for constructing arbitrary gates
which perform substantially faster than circuits based on the conventional
Solovay-Kitaev algorithm [C.M. Dawson and M.A. Nielsen, \emph{Quantum Inf.
Comput.}, \textbf{6}:81, 2006]. For a given approximation error ,
arbitrary single-qubit gates can be produced fault-tolerantly and using a
limited set of gates in time which is or ; with sufficient parallel preparation of ancillas, constant average
depth is possible using a method we call programmable ancilla rotations.
Moreover, we construct and analyze efficient implementations of first- and
second-quantized simulation algorithms using the fault-tolerant arbitrary gates
and other techniques, such as implementing various subroutines in constant
time. A specific example we analyze is the ground-state energy calculation for
Lithium hydride.Comment: 33 pages, 18 figure
Mechanical design and development of TES bolometer detector arrays for the Advanced ACTPol experiment
The next generation Advanced ACTPol (AdvACT) experiment is currently underway
and will consist of four Transition Edge Sensor (TES) bolometer arrays, with
three operating together, totaling ~5800 detectors on the sky. Building on
experience gained with the ACTPol detector arrays, AdvACT will utilize various
new technologies, including 150mm detector wafers equipped with multichroic
pixels, allowing for a more densely packed focal plane. Each set of detectors
includes a feedhorn array of stacked silicon wafers which form a spline profile
leading to each pixel. This is then followed by a waveguide interface plate,
detector wafer, back short cavity plate, and backshort cap. Each array is
housed in a custom designed structure manufactured from high purity copper and
then gold plated. In addition to the detector array assembly, the array package
also encloses cryogenic readout electronics. We present the full mechanical
design of the AdvACT high frequency (HF) detector array package along with a
detailed look at the detector array stack assemblies. This experiment will also
make use of extensive hardware and software previously developed for ACT, which
will be modified to incorporate the new AdvACT instruments. Therefore, we
discuss the integration of all AdvACT arrays with pre-existing ACTPol
infrastructure.Comment: 9 pages, 5 figures, SPIE Astronomical Telescopes and Instrumentation
conference proceeding
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Furin cleavage of SARS-CoV-2 Spike promotes but is not essential for infection and cell-cell fusion.
Severe Acute Respiratory Syndrome coronavirus 2 (SARS-CoV-2) infects cells by binding to the host cell receptor ACE2 and undergoing virus-host membrane fusion. Fusion is triggered by the protease TMPRSS2, which processes the viral Spike (S) protein to reveal the fusion peptide. SARS-CoV-2 has evolved a multibasic site at the S1-S2 boundary, which is thought to be cleaved by furin in order to prime S protein for TMPRSS2 processing. Here we show that CRISPR-Cas9 knockout of furin reduces, but does not prevent, the production of infectious SARS-CoV-2 virus. Comparing S processing in furin knockout cells to multibasic site mutants reveals that while loss of furin substantially reduces S1-S2 cleavage it does not prevent it. SARS-CoV-2 S protein also mediates cell-cell fusion, potentially allowing virus to spread virion-independently. We show that loss of furin in either donor or acceptor cells reduces, but does not prevent, TMPRSS2-dependent cell-cell fusion, unlike mutation of the multibasic site that completely prevents syncytia formation. Our results show that while furin promotes both SARS-CoV-2 infectivity and cell-cell spread it is not essential, suggesting furin inhibitors may reduce but not abolish viral spread
The Primordial Inflation Polarization Explorer (PIPER)
The Primordial Inflation Polarization Explorer (PIPER) is a balloon-borne
cosmic microwave background (CMB) polarimeter designed to search for evidence
of inflation by measuring the large-angular scale CMB polarization signal.
BICEP2 recently reported a detection of B-mode power corresponding to the
tensor-to-scalar ratio r = 0.2 on ~2 degree scales. If the BICEP2 signal is
caused by inflationary gravitational waves (IGWs), then there should be a
corresponding increase in B-mode power on angular scales larger than 18
degrees. PIPER is currently the only suborbital instrument capable of fully
testing and extending the BICEP2 results by measuring the B-mode power spectrum
on angular scales = ~0.6 deg to 90 deg, covering both the reionization
bump and recombination peak, with sensitivity to measure the tensor-to-scalar
ratio down to r = 0.007, and four frequency bands to distinguish foregrounds.
PIPER will accomplish this by mapping 85% of the sky in four frequency bands
(200, 270, 350, 600 GHz) over a series of 8 conventional balloon flights from
the northern and southern hemispheres. The instrument has background-limited
sensitivity provided by fully cryogenic (1.5 K) optics focusing the sky signal
onto four 32x40-pixel arrays of time-domain multiplexed Transition-Edge Sensor
(TES) bolometers held at 140 mK. Polarization sensitivity and systematic
control are provided by front-end Variable-delay Polarization Modulators
(VPMs), which rapidly modulate only the polarized sky signal at 3 Hz and allow
PIPER to instantaneously measure the full Stokes vector (I, Q, U, V) for each
pointing. We describe the PIPER instrument and progress towards its first
flight.Comment: 11 pages, 7 figures. To be published in Proceedings of SPIE Volume
9153. Presented at SPIE Astronomical Telescopes + Instrumentation 2014,
conference 915
Furin cleavage of SARS-CoV-2 Spike promotes but is not essential for infection and cell-cell fusion.
Severe Acute Respiratory Syndrome coronavirus 2 (SARS-CoV-2) infects cells by binding to the host cell receptor ACE2 and undergoing virus-host membrane fusion. Fusion is triggered by the protease TMPRSS2, which processes the viral Spike (S) protein to reveal the fusion peptide. SARS-CoV-2 has evolved a multibasic site at the S1-S2 boundary, which is thought to be cleaved by furin in order to prime S protein for TMPRSS2 processing. Here we show that CRISPR-Cas9 knockout of furin reduces, but does not prevent, the production of infectious SARS-CoV-2 virus. Comparing S processing in furin knockout cells to multibasic site mutants reveals that while loss of furin substantially reduces S1-S2 cleavage it does not prevent it. SARS-CoV-2 S protein also mediates cell-cell fusion, potentially allowing virus to spread virion-independently. We show that loss of furin in either donor or acceptor cells reduces, but does not prevent, TMPRSS2-dependent cell-cell fusion, unlike mutation of the multibasic site that completely prevents syncytia formation. Our results show that while furin promotes both SARS-CoV-2 infectivity and cell-cell spread it is not essential, suggesting furin inhibitors may reduce but not abolish viral spread
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