4,416 research outputs found
Snatch trajectory of elite level girevoy (Kettlebell) sport athletes and its implications to strength and conditioning coaching
Girevoy sport (GS) has developed only recently in the West, resulting in a paucity of English scientific literature available. The aim was to document kettlebell trajectory of GS athletes performing the kettlebell snatch. Four elite GS athletes (age = 29-47 years, body mass = 68.3-108.1 kg, height 1.72-1.89 m) completed one set of 16 repetitions with a 32.1 kg kettlebell. Trajectory was captured with the VICON motion analysis system (250 Hz) and analysed with VICON Nexus (1.7.1). The kettlebell followed a ‘C’ shape trajectory in the sagittal plane. Mean peak velocity in the upwards phase was 4.03 ± 0.20 m s –1, compared to 3.70 ± 0.30 m s–1 during the downwards phase, and mean radial error across the sagittal and frontal planes was 0.022 ± 0.006 m. Low error in the movement suggests consistent trajectory is important to reduce extraneous movement and improve efficiency. While the kettlebell snatch and swing both require large anterior-posterior motion, the snatch requires the kettlebell to be held stationary overhead. Therefore, a different coaching application is required to that of a barbell snatch
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Dissociation of Cerebral Blood Flow and Femoral Artery Blood Pressure Pulsatility After Cardiac Arrest and Resuscitation in a Rodent Model: Implications for Neurological Recovery.
Background Impaired neurological function affects 85% to 90% of cardiac arrest (CA) survivors. Pulsatile blood flow may play an important role in neurological recovery after CA. Cerebral blood flow (CBF) pulsatility immediately, during, and after CA and resuscitation has not been investigated. We characterized the effects of asphyxial CA on short-term (<2 hours after CA) CBF and femoral arterial blood pressure (ABP) pulsatility and studied their relationship to cerebrovascular resistance (CVR) and short-term neuroelectrical recovery. Methods and Results Male rats underwent asphyxial CA followed by cardiopulmonary resuscitation. A multimodal platform combining laser speckle imaging, ABP, and electroencephalography to monitor CBF, peripheral blood pressure, and brain electrophysiology, respectively, was used. CBF and ABP pulsatility and CVR were assessed during baseline, CA, and multiple time points after resuscitation. Neuroelectrical recovery, a surrogate for neurological outcome, was assessed using quantitative electroencephalography 90 minutes after resuscitation. We found that CBF pulsatility differs significantly from baseline at all experimental time points with sustained deficits during the 2 hours of postresuscitation monitoring, whereas ABP pulsatility was relatively unaffected. Alterations in CBF pulsatility were inversely correlated with changes in CVR, but ABP pulsatility had no association to CVR. Interestingly, despite small changes in ABP pulsatility, higher ABP pulsatility was associated with worse neuroelectrical recovery, whereas CBF pulsatility had no association. Conclusions Our results reveal, for the first time, that CBF pulsatility and CVR are significantly altered in the short-term postresuscitation period after CA. Nevertheless, higher ABP pulsatility appears to be inversely associated with neuroelectrical recovery, possibly caused by impaired cerebral autoregulation and/or more severe global cerebral ischemia
The amplitude and the resonant transition from lattice QCD
We present a determination of the -wave
transition amplitude from lattice quantum chromodynamics. Matrix elements of
the vector current in a finite-volume are extracted from three-point
correlation functions, and from these we determine the infinite-volume
amplitude using a generalization of the Lellouch-L\"uscher formalism. We
determine the amplitude for a range of discrete values of the energy
and virtuality of the photon, and observe the expected dynamical enhancement
due to the resonance. Describing the energy dependence of the amplitude,
we are able to analytically continue into the complex energy plane and from the
residue at the pole extract the transition
form factor. This calculation, at MeV, is the first to
determine the form factor of an unstable hadron within a first principles
approach to QCD.Comment: 20 pages, 16 figures, 3 table
An evolutionary perspective on the kinome of malaria parasites
Malaria parasites belong to an ancient lineage that diverged very early from the main branch of eukaryotes. The approximately 90-member plasmodial kinome includes a majority of eukaryotic protein kinases that clearly cluster within the AGC, CMGC, TKL, CaMK and CK1 groups found in yeast, plants and mammals, testifying to the ancient ancestry of these families. However, several hundred millions years of independent evolution, and the specific pressures brought about by first a photosynthetic and then a parasitic lifestyle, led to the emergence of unique features in the plasmodial kinome. These include taxon-restricted kinase families, and unique peculiarities of individual enzymes even when they have homologues in other eukaryotes. Here, we merge essential aspects of all three malaria-related communications that were presented at the Evolution of Protein Phosphorylation meeting, and propose an integrated discussion of the specific features of the parasite's kinome and phosphoproteome
Thermal intermodulation backaction in a high-cooperativity optomechanical system
The pursuit of room temperature quantum optomechanics with tethered
nanomechanical resonators faces stringent challenges owing to extraneous
mechanical degrees of freedom. An important example is thermal intermodulation
noise (TIN), a form of excess optical noise produced by mixing of thermal noise
peaks. While TIN can be decoupled from the phase of the optical field, it
remains indirectly coupled via radiation pressure, implying a hidden source of
backaction that might overwhelm shot noise. Here we report observation of TIN
backaction in a high-cooperativity, room temperature cavity optomechanical
system consisting of an acoustic-frequency SiN trampoline coupled to a
Fabry-P\'{e}rot cavity. The backaction we observe exceeds thermal noise by 20
dB and radiation pressure shot noise by 40 dB, despite the thermal motion being
10 times smaller than the cavity linewidth. Our results suggest that mitigating
TIN may be critical to reaching the quantum regime from room temperature in a
variety of contemporary optomechanical systems.Comment: 8 pages, 5 figure
Towards cavity-free ground state cooling of an acoustic-frequency silicon nitride membrane
We demonstrate feedback cooling of a millimeter-scale, 40 kHz SiN membrane
from room temperature to 5 mK (3000 phonons) using a Michelson interferometer,
and discuss the challenges to ground state cooling without an optical cavity.
This advance appears within reach of current membrane technology, positioning
it as a compelling alternative to levitated systems for quantum sensing and
fundamental weak force measurements.Comment: To be published in the Applied Optics special issue: James C. Wyant
College of Optical Science
Stability Analysis of Asynchronous States in Neuronal Networks with Conductance-Based Inhibition
Oscillations in networks of inhibitory interneurons have been reported at various sites of the brain and are thought to play a fundamental role in neuronal processing. This Letter provides a self-contained analytical framework that allows numerically efficient calculations of the population activity of a network of conductance-based integrate-and-fire neurons that are coupled through inhibitory synapses. Based on a normalization equation this Letter introduces a novel stability criterion for a network state of asynchronous activity and discusses its perturbations. The analysis shows that, although often neglected, the reversal potential of synaptic inhibition has a strong influence on the stability as well as the frequency of network oscillations
Prematurity, delivery method and infant feeding type are not associated with paediatric-onset inflammatory bowel disease risk: A Scottish retrospective birth cohort study
Generalized Lévy walks and the role of chemokines in migration of effector CD8+ T cells.
Chemokines have a central role in regulating processes essential to the immune function of T cells, such as their migration within lymphoid tissues and targeting of pathogens in sites of inflammation. Here we track T cells using multi-photon microscopy to demonstrate that the chemokine CXCL10 enhances the ability of CD8+ T cells to control the pathogen Toxoplasma gondii in the brains of chronically infected mice. This chemokine boosts T-cell function in two different ways: it maintains the effector T-cell population in the brain and speeds up the average migration speed without changing the nature of the walk statistics. Notably, these statistics are not Brownian; rather, CD8+ T-cell motility in the brain is well described by a generalized Lévy walk. According to our model, this unexpected feature enables T cells to find rare targets with more than an order of magnitude more efficiency than Brownian random walkers. Thus, CD8+ T-cell behaviour is similar to Lévy strategies reported in organisms ranging from mussels to marine predators and monkeys, and CXCL10 aids T cells in shortening the average time taken to find rare targets
Resonant ⁺ → ⁺⁰ Amplitude from Quantum Chromodynamics
We present the first ab initio calculation of a radiative transition of a hadronic resonance within quantum chromodynamics (QCD). We compute the amplitude for →⋆, as a function of the energy of the pair and the virtuality of the photon, in the kinematic regime where couples strongly to the unstable ρ resonance. This exploratory calculation is performed using a lattice discretization of QCD with quark masses corresponding to mπ ≈ 400 MeV. We obtain a description of the energy dependence of the transition amplitude, constrained at 48 kinematic points, that we can analytically continue to the ρ pole and identify from its residue the ρ→⋆ form factor
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