3,200 research outputs found
Flow Fluctuations from Early-Time Correlations in Nuclear Collisions
We propose that flow fluctuations have the same origin as transverse momentum
fluctuations. The common source of these fluctuations is the spatially
inhomogeneous initial state that drives hydrodynamic flow. Longitudinal
correlations from an early Glasma stage followed by hydrodynamic flow
quantitatively account for many features of multiplicity and fluctuation
data. We develop a framework for studying flow and its fluctuations in this
picture. We then compute elliptic and triangular flow fluctuations, and study
their connections to the ridge
The Glasma and the Hard Ridge
Correlation measurements indicate that excess two particle correlations
extend over causally disconnected rapidity ranges. Although, this enhancement
is broad in relative rapidity , it is focused in a narrow
region in relative azimuthal angle . The resulting
structure looks like a ridge centered at . Similar ridge
structures are observed in correlations of particles associated with a jet
trigger (the hard ridge) and in correlations without a trigger (the soft
ridge). The long range rapidity behavior requires that the correlation
originates in the earliest stage of the collision, and probes properties of the
production mechanism. Glasma initial conditions as predicted by the theory of
Color Glass Condensate and provide a and early stage correlation that naturally
extends far in rapidity. We have previously shown that the soft ridge is a
consequence of particles forming from an initial Glasma phase that experience a
later stage transverse flow. We extend this work to study the ridge dependence
on the of the correlated pairs. We then determine the soft contribution
to the hard ridge.Comment: Proceeding of the APS meeting of the Division of Particles and Fields
2009, Detroit, Mi. Also see arXiv:0910.359
Long Range Correlations and the Soft Ridge in Relativistic Nuclear Collisions
Relativistic Heavy Ion Collider experiments exhibit correlations peaked in
relative azimuthal angle and extended in rapidity. Called the ridge, this peak
occurs both with and without a jet trigger. We argue that the untriggered ridge
arises when particles formed by flux tubes in an early glasma stage later
manifest transverse flow. Combining a blast wave model of flow fixed by
single-particle spectra with a simple description of the glasma, we find
excellent agreement with current data.Comment: revised text, results unchange
Predicting Avian Influenza Co-Infection with H5N1 and H9N2 in Northern Egypt.
Human outbreaks with avian influenza have been, so far, constrained by poor viral adaptation to non-avian hosts. This could be overcome via co-infection, whereby two strains share genetic material, allowing new hybrid strains to emerge. Identifying areas where co-infection is most likely can help target spaces for increased surveillance. Ecological niche modeling using remotely-sensed data can be used for this purpose. H5N1 and H9N2 influenza subtypes are endemic in Egyptian poultry. From 2006 to 2015, over 20,000 poultry and wild birds were tested at farms and live bird markets. Using ecological niche modeling we identified environmental, behavioral, and population characteristics of H5N1 and H9N2 niches within Egypt. Niches differed markedly by subtype. The subtype niches were combined to model co-infection potential with known occurrences used for validation. The distance to live bird markets was a strong predictor of co-infection. Using only single-subtype influenza outbreaks and publicly available ecological data, we identified areas of co-infection potential with high accuracy (area under the receiver operating characteristic (ROC) curve (AUC) 0.991)
Swansea Bay tidal lagoon annual energy estimation
UK Energy policy is focused on the challenges posed by energy security and climate change, however, efforts to develop a low-carbon economy have overlooked tidal energy a vast and unexploited worldwide resource. Since 1981, UK tidal lagoon schemes have been recommended as an economically and environmentally attractive alternative to tidal barrages. More recently, two proposals for tidal lagoons in Swansea Bay have emerged and there have been several reports documenting the potential to harness significant tidal energy from Swansea Bay using a tidal lagoon. This paper assists in determining a realistic approximation of the energy generation potential in Swansea Bay, a numerical estimation is obtained from a zero dimension, 0D, ‘backwards difference’ computational model, utilising the latest turbine data available and high-resolution bathymetric data. This paper models the behaviour of the tidal lagoon in dual mode generation, in line with the above proposals. The results of model testing using a variety of fixed and variable parameters are displayed. The ebb mode model with provision for pumping at high tide is then explored further by carrying out optimisations of the starting head, number of turbines and turbine diameter in order to determine the maximum annual energy output from the tidal lagoon
Movement kinematics and proprioception in post-stroke spasticity: assessment using the Kinarm robotic exoskeleton
Background
Motor impairment after stroke interferes with performance of everyday activities. Upper limb spasticity may further disrupt the movement patterns that enable optimal function; however, the specific features of these altered movement patterns, which differentiate individuals with and without spasticity, have not been fully identified. This study aimed to characterize the kinematic and proprioceptive deficits of individuals with upper limb spasticity after stroke using the Kinarm robotic exoskeleton.
Methods
Upper limb function was characterized using two tasks: Visually Guided Reaching, in which participants moved the limb from a central target to 1 of 4 or 1 of 8 outer targets when cued (measuring reaching function) and Arm Position Matching, in which participants moved the less-affected arm to mirror match the position of the affected arm (measuring proprioception), which was passively moved to 1 of 4 or 1 of 9 different positions. Comparisons were made between individuals with (n = 35) and without (n = 35) upper limb post-stroke spasticity.
Results
Statistically significant differences in affected limb performance between groups were observed in reaching-specific measures characterizing movement time and movement speed, as well as an overall metric for the Visually Guided Reaching task. While both groups demonstrated deficits in proprioception compared to normative values, no differences were observed between groups. Modified Ashworth Scale score was significantly correlated with these same measures.
Conclusions
The findings indicate that individuals with spasticity experience greater deficits in temporal features of movement while reaching, but not in proprioception in comparison to individuals with post-stroke motor impairment without spasticity. Temporal features of movement can be potential targets for rehabilitation in individuals with upper limb spasticity after stroke.York University Librarie
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