1,046 research outputs found
Effects of a red background on magnocellular functioning in average and specifically disabled readers
AbstractTwo experiments were conducted using metacontrast masking to examine responses in the magno system of adults, average reading adolescents and adolescents with specific reading disability. In Experiment 1 the effects of a red background field on the metacontrast functions of adult subjects were investigated. Results showed that a red, compared to a photometrically matched white background field, significantly attenuated metacontrast magnitude, supporting the interpretation of metacontrast as due to magno system suppression of parvo system responses. The finding of a red background effect was replicated in Experiment 2 with the two adolescent groups. The metacontrast functions of the adolescent groups also differed significantly, with those with specific reading disability exhibiting weaker metacontrast than the average readers. This result is consistent with a deficit in the magno system of individuals with specific reading disability and indicates the continuation of the deficit beyond childhood
Optimal low-dispersion low-dissipation LBM schemes for computational aeroacoustics
Lattice Boltmzmann Methods (LBM) have been proved to be very effective
methods for computational aeroacoustics (CAA), which have been used to capture
the dynamics of weak acoustic fluctuations. In this paper, we propose a
strategy to reduce the dispersive and disspative errors of the two-dimensional
(2D) multi-relaxation-time lattice Boltzmann method (MRT-LBM). By presenting an
effective algorithm, we obtain a uniform form of the linearized Navier-Stokes
equations corresponding to the MRT-LBM in wave-number space. Using the matrix
perturbation theory and the equivalent modified equation approach for finite
difference methods, we propose a class of minimization problems to optimize the
free-parameters in the MRT-LBM. We obtain this way a
dispersion-relation-preserving LBM (DRP-LBM) to circumvent the minimized
dispersion error of the MRT-LBM. The dissipation relation precision is also
improved.And the stability of the MRT-LBM with the small bulk viscosity is
guaranteed. Von Neuman analysis of the linearized MRT-LBM is performed to
validate the optimized dispersion/dissipation relations considering
monochromatic wave solutions. Meanwhile, dispersion and dissipation errors of
the optimized MRT-LBM are quantitatively compared with the original MRT-LBM .
Finally, some numerical simulations are carried out to assess the new optimized
MRT-LBM schemes.Comment: 33 page
The ball in play demands of international rugby union
Objectives: Rugby union is a high intensity intermittent sport, typically analysed via set time periods or rolling average methods. This study reports the demands of international rugby union via global positioning system (GPS) metrics expressed as mean ball in play (BiP), maximum BiP (max BiP), and whole match outputs.
Design: Single cohort cross sectional study involving 22 international players, categorised as forwards and backs.
Methods: A total of 88 GPS files from eight international test matches were collected during 2016. An Opta sportscode timeline was integrated into the GPS software to split the data into BiP periods. Metres per min (m.min-1), high metabolic load per min (HML), accelerations per min (Acc), high speed running per min (HSR), and collisions per min (Coll) were expressed relative to BiP periods and over the whole match (>60min).
Results: Whole match metrics were significantly lower than all BiP metrics (p < 0.001). Mean and max BiP HML, (p < 0.01) and HSR (p < 0.05) were significantly higher for backs versus forwards, whereas Coll were significantly higher for forwards (p < 0.001). In plays lasting 61s or greater, max BiP m.min-1 were higher for backs. Max BiP m.min-1, HML, HSR and Coll were all time dependant (p < 0.05) showing that both movement metrics and collision demands differ as length of play continues.
Conclusions: This study uses a novel method of accurately assessing the BiP demands of rugby union. It also reports typical and maximal demands of international rugby union that can be used by practitioners and scientists to target training of worst-case scenario's equivalent to international intensity. Backs covered greater distances at higher speeds and demonstrated higher HML, in general play as well as 'worst case scenarios'; conversely forwards perform a higher number of collisions
A Comparison between the Zero Forcing Number and the Strong Metric Dimension of Graphs
The \emph{zero forcing number}, , of a graph is the minimum
cardinality of a set of black vertices (whereas vertices in are
colored white) such that is turned black after finitely many
applications of "the color-change rule": a white vertex is converted black if
it is the only white neighbor of a black vertex. The \emph{strong metric
dimension}, , of a graph is the minimum among cardinalities of all
strong resolving sets: is a \emph{strong resolving set} of
if for any , there exists an such that either
lies on an geodesic or lies on an geodesic. In this paper, we
prove that for a connected graph , where is
the cycle rank of . Further, we prove the sharp bound
when is a tree or a unicyclic graph, and we characterize trees
attaining . It is easy to see that can be
arbitrarily large for a tree ; we prove that and
show that the bound is sharp.Comment: 8 pages, 5 figure
Indocyanine green fluorescence image processing techniques for breast cancer macroscopic demarcation
Re-operation due to disease being inadvertently close to the resection margin is a major challenge in breast conserving surgery (BCS). Indocyanine green (ICG) fluorescence imaging could be used to visualize the tumor boundaries and help surgeons resect disease more efficiently. In this work, ICG fluorescence and color images were acquired with a custom-built camera system from 40 patients treated with BCS. Images were acquired from the tumor in-situ, surgical cavity post-excision, freshly excised tumor and histopathology tumour grossing. Fluorescence image intensity and texture were used as individual or combined predictors in both logistic regression (LR) and support vector machine models to predict the tumor extent. ICG fluorescence spectra in formalin-fixed histopathology grossing tumor were acquired and analyzed. Our results showed that ICG remains in the tissue after formalin fixation. Therefore, tissue imaging could be validated in freshly excised and in formalin-fixed grossing tumor. The trained LR model with combined fluorescence intensity (pixel values) and texture (slope of power spectral density curve) identified the tumor’s extent in the grossing images with pixel-level resolution and sensitivity, specificity of 0.75 ± 0.3, 0.89 ± 0.2.This model was applied on tumor in-situ and surgical cavity (post-excision) images to predict tumor presence
Signatures of partition functions and their complexity reduction through the KP II equation
A statistical amoeba arises from a real-valued partition function when the
positivity condition for pre-exponential terms is relaxed, and families of
signatures are taken into account. This notion lets us explore special types of
constraints when we focus on those signatures that preserve particular
properties. Specifically, we look at sums of determinantal type, and main
attention is paid to a distinguished class of soliton solutions of the
Kadomtsev-Petviashvili (KP) II equation. A characterization of the signatures
preserving the determinantal form, as well as the signatures compatible with
the KP II equation, is provided: both of them are reduced to choices of signs
for columns and rows of a coefficient matrix, and they satisfy the whole KP
hierarchy. Interpretations in term of information-theoretic properties,
geometric characteristics, and the relation with tropical limits are discussed.Comment: 42 pages, 11 figures. Section 7.1 has been added, the organization of
the paper has been change
Algebraic inversion of the Dirac equation for the vector potential in the non-abelian case
We study the Dirac equation for spinor wavefunctions minimally coupled to an
external field, from the perspective of an algebraic system of linear equations
for the vector potential. By analogy with the method in electromagnetism, which
has been well-studied, and leads to classical solutions of the Maxwell-Dirac
equations, we set up the formalism for non-abelian gauge symmetry, with the
SU(2) group and the case of four-spinor doublets. An extended isospin-charge
conjugation operator is defined, enabling the hermiticity constraint on the
gauge potential to be imposed in a covariant fashion, and rendering the
algebraic system tractable. The outcome is an invertible linear equation for
the non-abelian vector potential in terms of bispinor current densities. We
show that, via application of suitable extended Fierz identities, the solution
of this system for the non-abelian vector potential is a rational expression
involving only Pauli scalar and Pauli triplet, Lorentz scalar, vector and axial
vector current densities, albeit in the non-closed form of a Neumann series.Comment: 21pp, uses iopar
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