1,446,074 research outputs found
A Computer-Based Method to Improve the Spelling of Children with Dyslexia
In this paper we present a method which aims to improve the spelling of
children with dyslexia through playful and targeted exercises. In contrast to
previous approaches, our method does not use correct words or positive examples
to follow, but presents the child a misspelled word as an exercise to solve. We
created these training exercises on the basis of the linguistic knowledge
extracted from the errors found in texts written by children with dyslexia. To
test the effectiveness of this method in Spanish, we integrated the exercises
in a game for iPad, DysEggxia (Piruletras in Spanish), and carried out a
within-subject experiment. During eight weeks, 48 children played either
DysEggxia or Word Search, which is another word game. We conducted tests and
questionnaires at the beginning of the study, after four weeks when the games
were switched, and at the end of the study. The children who played DysEggxia
for four weeks in a row had significantly less writing errors in the tests that
after playing Word Search for the same time. This provides evidence that
error-based exercises presented in a tablet help children with dyslexia improve
their spelling skills.Comment: 8 pages, ASSETS'14, October 20-22, 2014, Rochester, NY, US
Transference of fractional Laplacian regularity
In this note we show how to obtain regularity estimates for the fractional
Laplacian on the multidimensional torus from the fractional
Laplacian on . Though at first glance this may seem quite
natural, it must be carefully precised. A reason for that is the simple fact
that functions on the torus can not be identified with functions on
. The transference is achieved through a formula that holds in
the distributional sense. Such an identity allows us to transfer Harnack
inequalities, to relate the extension problems, and to obtain pointwise
formulas and H\"older regularity estimates.Comment: 7 pages. To appear in Special Functions, Partial Differential
Equations and Harmonic Analysis. Proceedings of the conference in honor of
Calixto P. Calder\'on, Roosevelt University at Chicago, November 16-18, 2012.
C. Georgakis, A. Stokolos and W. Urbina (eds
Transient glare: its effect on the lower threshold of motion
We measured the lower threshold of motion (LTM) of suprathreshold gratings as a function of spatial frequency and contrast, for both transient glare and no-glare conditions. A two alternatives forced choice paradigm, using the method of constant stimuli, was adopted to measure the LTM. The LTM occurs at constant velocity. This velocity threshold is higher for transient glare condition than for no-glare condition. We found that the sudden onset of glare increases LTM over the whole range of contrasts. We believe the effect of transient glare sources on the lower threshold of motion is due to the transient loss of sensitivity.Fil: Barraza, Jose Fernando. Universidad Nacional de Tucumán. Facultad de Ciencias Exactas y Tecnología. Departamento de Luminotecnia, Luz y Visión; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Investigación en Luz, Ambiente y Visión. Universidad Nacional de Tucumán. Facultad de Ciencias Exactas y Tecnología. Instituto de Investigación en Luz, Ambiente y Visión; ArgentinaFil: Colombo, Elisa Margarita. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Investigación en Luz, Ambiente y Visión. Universidad Nacional de Tucumán. Facultad de Ciencias Exactas y Tecnología. Instituto de Investigación en Luz, Ambiente y Visión; Argentina. Universidad Nacional de Tucumán. Facultad de Ciencias Exactas y Tecnología. Departamento de Luminotecnia, Luz y Visión; Argentin
Ab initio molecular dynamics simulations of Aluminum solvation
The solvation of Al and its hydrolyzed species in water clusters has been
studied by means of ab initio molecular dynamics simulations. The hexa-hydrate
aluminum ion formed a stable complex in the finite temperature cluster
simulation of one aluminum ion and 16 waters. The average dipole moment of
strongly polarized hydrated water molecules in the first solvation shell of the
hexa-hydrate aluminum ion was found to be 5.02 Debye. The deprotonated
hexa-hydrate complex evolves into a tetra-coordinated aluminate ion with two
water molecules in the second solvation shell forming hydrogen bonds to the
hydroxyl groups in agreement with the observed coordination.Comment: 12 pages in Elsevier LaTeX, 5 figures in Postscript, 2 last figures
are in color, submitted to Chemical Physics Letter
The Transition to Superrotation in Terrestrial Atmospheres
We show that by changing a single non-dimensional number, the thermal Rossby
number, global atmospheric simulations with only axisymmetric forcing pass from
an Earth-like atmosphere to a superrotating atmosphere that more resembles the
atmospheres of Venus or Titan. The transition to superrotation occurs under
conditions in which equatorward-propagating Rossby waves generated by
baroclinic instability at intermediate and high latitudes are suppressed, which
will occur when the deformation radius exceeds the planetary radius. At large
thermal Rossby numbers following an initial, nearly axisymmetric phase, a
global baroclinic wave of zonal wavenumber one generated by mixed
barotropic-baroclinic instability dominates the eddy flux of zonal momentum.
The global wave converges eastward zonal momentum to the equator and deposits
westward momentum at intermediate latitudes during spinup and before
superrotation emerges, and the baroclinic instability ceases once superrotation
is established. A global barotropic mode of zonal wavenumber one generated by a
mix of high- and low-latitude barotropic instability is responsible for
maintaining superrotation in the statistically steady state. At intermediate
thermal Rossby numbers, momentum flux by the global baroclinic mode is
subdominant relative to smaller baroclinic modes, and thus strong superrotation
does not develop.Comment: accepted for publication in JGR-Planet
Comprehensive inter-laboratory calibration of reference materials for δ18O versus VSMOW using various on-line high-temperature conversion techniques
Internationally distributed organic and inorganic oxygen isotopic reference materials have been calibrated by six laboratories carrying out more than 5300 measurements using a variety of high-temperature conversion techniques (HTC) in an evaluation sponsored by the International Union of Pure and Applied Chemistry (IUPAC). To aid in the calibration of these reference materials, which span more than 125‰, an artificially enriched reference water (δ18O of +78.91‰) and two barium sulfates (one depleted and one enriched in 18O) were prepared and calibrated relative to VSMOW2 and SLAP reference waters. These materials were used to calibrate the other isotopic reference materials in this study.
The seemingly large estimated combined uncertainties arise from differences in instrumentation and methodology and difficulty in accounting for all measurement bias. They are composed of the 3-fold standard errors directly calculated from the measurements and provision for systematic errors discussed in this paper. A primary conclusion of this study is that nitrate samples analyzed for δ18O should be analyzed with internationally distributed isotopic nitrates, and likewise for sulfates and organics. Authors reporting relative differences of oxygen-isotope ratios (δ18O) of nitrates, sulfates, or organic material should explicitly state in their reports the δ18O values of two or more internationally distributed nitrates (USGS34, IAEA-NO-3, and USGS35), sulfates (IAEA-SO-5, IAEA-SO-6, and NBS 127), or organic material (IAEA-601 benzoic acid, IAEA-602 benzoic acid, and IAEA-600 caffeine), as appropriate to the material being analyzed, had these reference materials been analyzed with unknowns. This procedure ensures that readers will be able to normalize the δ18O values at a later time should it become necessary.
The high-temperature reduction technique for analyzing δ18O and δ2H is not as widely applicable as the well-established combustion technique for carbon and nitrogen stable isotope determination. To obtain the most reliable stable isotope data, materials should be treated in an identical fashion; within the same sequence of analyses, samples should be compared with working reference materials that are as similar in nature and in isotopic composition as feasible.
Significance Tests for Periodogram Peaks
We discuss methods currently in use for determining the significance of peaks
in the periodograms of time series. We discuss some general methods for
constructing significance tests, false alarm probability functions, and the
role played in these by independent random variables and by empirical and
theoretical cumulative distribution functions. We also discuss the concept of
"independent frequencies" in periodogram analysis. We propose a practical
method for estimating the significance of periodogram peaks, applicable to all
time series irrespective of the spacing of the data. This method, based on
Monte Carlo simulations, produces significance tests that are tailor-made for
any given astronomical time series.Comment: 22 pages, 11 Encapsulated Postscript figures, AAS LaTeX v5.2
Submitted to Ap
Ageing, physical function, and the diurnal rhythms of cortisol and dehydroepiandrosterone
The present study examined the relationship between ageing, physical function and the diurnal rhythms of cortisol and dehydroepiandrosterone (DHEA). Participants were 36 community dwelling older adults aged between 65-86 years old. Salivary cortisol and DHEA were measured over the course of one day: immediately upon awakening, 30 min later, and then 3 h, 6 h, 9 h and 12 h post-awakening. Participants completed the Nottingham extended activities of daily living index, the Berg Balance Scale and their handgrip strength was assessed. Older participants had a significantly higher cortisol area under the curve (AUC), lower overall DHEA levels, lower DHEA AUC, a decreased diurnal slope of decline and increased cortisol:DHEA ratio. Lower diurnal cortisol levels were associated with poorer performance on the Berg Balance Scale and lower handgrip strength, and those with a flattened DHEA diurnal profile reported less independence in carrying out daily tasks. These associations withstood adjustment for age. In conclusion, this study suggests an association between cortisol, DHEA, ageing and physical function
A new Chiral Two-Matrix Theory for Dirac Spectra with Imaginary Chemical Potential
We solve a new chiral Random Two-Matrix Theory by means of biorthogonal
polynomials for any matrix size . By deriving the relevant kernels we find
explicit formulas for all -point spectral (mixed or unmixed) correlation
functions. In the microscopic limit we find the corresponding scaling
functions, and thus derive all spectral correlators in this limit as well. We
extend these results to the ordinary (non-chiral) ensembles, and also there
provide explicit solutions for any finite size , and in the microscopic
scaling limit. Our results give the general analytical expressions for the
microscopic correlation functions of the Dirac operator eigenvalues in theories
with imaginary baryon and isospin chemical potential, and can be used to
extract the tree-level pion decay constant from lattice gauge theory
configurations. We find exact agreement with previous computations based on the
low-energy effective field theory in the two special cases where comparisons
are possible.Comment: 31 pages 2 figures, v2 missing term in partially quenched results
inserted, fig 2 update
A new chiral two-matrix theory for dirac spectra with imaginary chemical potential
We solve a new chiral Random Two-Matrix Theory by means of biorthogonal polynomials for any matrix size . By deriving the relevant kernels we find explicit formulas for all -point spectral (mixed or unmixed) correlation functions. In the microscopic limit we find the corresponding scaling functions, and thus derive all spectral correlators in this limit as well. We extend these results to the ordinary (non-chiral) ensembles, and also there provide explicit solutions for any finite size , and in the microscopic scaling limit. Our results give the general analytical expressions for the microscopic correlation functions of the Dirac operator eigenvalues in theories with imaginary baryon and isospin chemical potential, and can be used to extract the tree-level pion decay constant from lattice gauge theory configurations. We find exact agreement with previous computations based on the low-energy effective field theory in the two special cases where comparisons are possible
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