Página 1 dos resultados de 1546 itens digitais encontrados em 0.036 segundos

## STATISTICAL TEST FOR GENOTYPE AND ENVIRONMENT CONTRIBUTION IN THE GENOTYPES x ENVIRONMENTS INTERACTION MATRIX

Araujo, Mirian Fernandes Carvalho; Araujo, Lucio Borges de; Faria, Priscila Neves; Dias, Carlos Tadeu dos Santos
Fonte: INTERCIENCIA; CARACAS Publicador: INTERCIENCIA; CARACAS
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
55.69%
The objective of the present work was to propose a method for testing the contribution of each level of the factors in a genotypes x environments (GxE) interaction using multi-environment trials analyses by means of an F test. The study evaluated a data set, with twenty genotypes and thirty-four environments, in a block design with four replications. The sum of squares within rows (genotypes) and columns (environments) of the GxE matrix was simulated, generating 10000 experiments to verify the empirical distribution. Results indicate a noncentral chi-square distribution for rows and columns of the GxE interaction matrix, which was also verified by the Kolmogorov-Smirnov test and Q-Q plot. Application of the F test identified the genotypes and environments that contributed the most to the GxE interaction. In this way, geneticists can select good genotypes in their studies.; Conselho Nacional Cientifico e Tecnologico (CNPq); Brazilian science funding agencies; Brazilian science funding agencies; CNPq

## Teste estatístico para contribuição de genótipos e ambientes na matriz de interação GE; Statistical test for contribution in the interaction matrix of genotypes and environments

Araújo, Mirian Fernandes Carvalho
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Relevância na Pesquisa
55.72%

## Genetic parameters for milk yield analyzed by test-day models in Murrah buffaloes in Brazil

Aspilcueta-Borquis, Rusbel R.; Bignardi, Annaiza B.; Seno, Leonardo de O.; Camargo, Gregorio M. F. de; Munoz-Berrocal, Milthon H.; Albuquerque, Lucia Galvão de; Di Palo, Rossella; Tonhati, Humberto
Fonte: Pagepress Publ Publicador: Pagepress Publ
Tipo: Artigo de Revista Científica Formato: 179-182
ENG
Relevância na Pesquisa
45.69%
Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); New statistical models for genetic parameters estimation based on longitudinal data have been proposed. In this study, we considered the data of 47,614 test-day milk yields from 1,578 buffaloes, with 4,757 complete lactations, calving from 1985 to 2006. Single- ,two-and multiple trait analyses were used and variance components were estimated by Restricted Maximum Likelihood. The model used to evaluate the milk yield trait at 305 days (MY305) included: i) herd-year-calving season (contemporary group) and milking number as fixed effects; ii) buffalo age at calving as covariate (linear and quadratic effect); iii) additive genetic, permanent environmental, residual and the animal as random effects. The same effects were included in the test-day milk yield model except the contemporary group, defined as herd-year-test day. The heritability estimations for TDMY vary from 0.13 to 0.23 for single-trait analyses, from 0.13 to 0.24 for two-trait analyses and from 0.15 to 0.24 for the multiple-trait analyses. The results obtained for each of the three models showed that the higher heritability estimations were always obtained in the third test month. The genetic correlations between the TDMY and MY305 were high and positive. In conclusion...

## Spectral F-Test power evaluation in the EEG during intermittent photic stimulaton

Sá,Antonio Mauricio F. L. Miranda de; Cagy,Mauricio; Lazarev,Vladimir V.; Infantosi,Antonio Fernando C.
Tipo: Artigo de Revista Científica Formato: text/html
Relevância na Pesquisa
75.69%
Intermittent photic stimulation (IPS) is an important functional test, which can induce the photic driving in the electroencephalogram (EEG). It is capable of enhancing latent oscillations manifestations not present in the resting EEG. However, for adequate quantitative evaluation of the photic driving, these changes should be assessed on a statistical basis. With this aim, the sampling distribution of spectral F test was investigated. On this basis, confidence limits of the SFT-estimate could be obtained for different practical situations, in which the signal-to-noise ratio and the number of epochs used in the estimation may vary. The technique was applied to the EEG of 10 normal subjects during IPS, and allowed detecting responses not only at the fundamental IPS frequency but also at higher harmonics. It also permitted to assess the strength of the photic driving responses and to compare them in different derivations and in different subjects.

## Accuracy test for in-vitro micro-computed tomography

Stoico, R.; Tassani, S.; Perilli, E.; Baruffaldi, F.; Viceconti, M.
Fonte: Springer; Germany Publicador: Springer; Germany
Tipo: Conference paper
Relevância na Pesquisa
45.69%
The present work aims to describe and discuss the application of an accuracy test for in-vitro micro-computed tomography (microCT). Accuracy of morphometric measures is required to the analysis of bone microstructure and the mechanical characterization of the tissue. The accuracy test was introduced in a program of quality control designed for trabecular bone morphometry. It was applied using a physical calibration phantom that reproduced the three-dimensional structure of the typically investigated object, i.e. trabecular bone structure. The phantom was used to test the quality of accuracy measurements. The absolute error was chosen as the quality control parameter in accuracy test. The Shewhart control chart was introduced to monitor the quality control parameter. Baseline value was calculated as reference value for the control chart during acceptance/status test. An out of control condition was defined as the monthly measure that was out of the tolerance limits determined by the adopted chart. A maintenance service has been suggested upon the occurrence of this condition. During the monitoring period of 15-months no out of control conditions in accuracy test were recorded, as confirmed by the statistical C and Kruskal Wallis tests. Thus...

## Statistical evaluation of a novel SSVEP-BCI stimulation setup based on depth-of-field

Cotrina,Anibal; Benevides,Alessandro Botti; Castillo-Garcia,Javier; Ferreira,Andre; Bastos Filho,Teodiano Freire
Tipo: Artigo de Revista Científica Formato: text/html
Relevância na Pesquisa
65.7%
AbstractIntroductionThe main drawback of a Brain-computer Interface based on Steady-State Visual Evoked Potential (SSVEP-BCI) that detects the emergence of visual evoked potentials (VEP) in reaction to flickering stimuli is its muscular dependence due to users must redirect their gaze to put the target stimulus in their field of view. In this work, a novel setup is evaluated in which two stimuli are placed together in the center of users' field of view, but with dissimilar distances from them, so that the target selection is performed by focus shifting instead of head, neck and/or eyeball movements.MethodsA model of VEP generation for the novel setup was developed. The Spectral F-test based on Bartett periodogram was used to evaluate the null hypothesis of absence of effects of the non-focused stimulus (NFS) within the VEP elicited by the focused stimulus (FS). To reinforce that there is not statistical evidence to support the presence of NFS effects, the PSDA detection method was employed to find the frequency of FS. Electroencephalographic signals of nine subjects were recorded.ResultsApproximately in 80% of the tests, the null hypothesis with 5% level of significance was non-rejected at the fundamental frequency of NFS. The average of the accuracy rate attained with PSDA detection method was 79.4%.ConclusionResults of this work become further evident to state that if the focused stimulus (FS) will be able to elicit distinguishable VEP pattern regardless the non-focused stimulus (NFS) is also present.

## Detection of movement intention using EEG in a human-robot interaction environment

Lana,Ernesto Pablo; Adorno,Bruno Vilhena; Tierra-Criollo,Carlos Julio
Tipo: Artigo de Revista Científica Formato: text/html
Relevância na Pesquisa
55.6%
Introduction: This paper presents a detection method for upper limb movement intention as part of a brain-machine interface using EEG signals, whose final goal is to assist disabled or vulnerable people with activities of daily living. Methods EEG signals were recorded from six naïve healthy volunteers while performing a motor task. Every volunteer remained in an acoustically isolated recording room. The robot was placed in front of the volunteers such that it seemed to be a mirror of their right arm, emulating a Brain Machine Interface environment. The volunteers were seated in an armchair throughout the experiment, outside the reaching area of the robot to guarantee safety. Three conditions are studied: observation, execution, and imagery of right arm’s flexion and extension movements paced by an anthropomorphic manipulator robot. The detector of movement intention uses the spectral F test for discrimination of conditions and uses as feature the desynchronization patterns found on the volunteers. Using a detector provides an objective method to acknowledge for the occurrence of movement intention. Results When using four realizations of the task, detection rates ranging from 53 to 97% were found in five of the volunteers when the movement was executed...

## A Simple Statistical Mechanical Approach for Studying Multilayer Adsorption of Interacting Polyatomics

Garcia, G. D.; Sanchez-Varretti, F. O.; Roma, F.; Ramirez-Pastor, A. J.
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
45.66%
A simple statistical mechanical approach for studying multilayer adsorption of interacting polyatomic adsorbates (k-mers) has been presented. The new theoretical framework has been developed on a generalization in the spirit of the lattice-gas model and the classical Bragg-Williams (BWA) and quasi-chemical (QCA) approximations. The derivation of the equilibrium equations allows the extension of the well-known Brunauer-Emmet-Teller (BET) isotherm to more complex systems. The formalism reproduces the classical theory for monomers, leads to the exact statistical thermodynamics of interacting k-mers adsorbed in one dimension, and provides a close approximation for two-dimensional systems accounting multisite occupancy and lateral interactions in the first layer. Comparisons between analytical data and Monte Carlo simulations were performed in order to test the validity of the theoretical model. The study showed that: (i) the resulting thermodynamic description obtained from QCA is significantly better than that obtained from BWA and still mathematically handable; (ii) for non-interacting k-mers, the BET equation leads to an underestimate of the true monolayer volume; (iii) attractive lateral interactions compensate the effect of the multisite occupancy and the monolayer volume predicted by BET equation agrees very well with the corresponding true value; and (iv) repulsive couplings between the admolecules hamper the formation of the monolayer and the BET results are not good (even worse than those obtained in the non-interacting case).; Comment: 38 pages...

## Inverse Statistical Mechanics: Probing the Limitations of Isotropic Pair Potentials to Produce Ground-State Structural Extremes

Zhang, G.; Stillinger, F. H.; Torquato, S.
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
45.59%
Inverse statistical-mechanical methods have recently been employed to design optimized short-ranged radial (isotropic) pair potentials that robustly produce novel targeted classical ground-state many-particle configurations. The target structures considered in those studies were low-coordinated crystals with a high degree of symmetry. In this paper, we further test the fundamental limitations of radial pair potentials by targeting crystal structures with appreciably less symmetry, including those in which the particles have different local structural environments. These challenging target configurations demanded that we modify previous inverse optimization techniques. Using this modified optimization technique, we have designed short-ranged radial pair potentials that stabilize the two-dimensional kagome crystal, the rectangular kagome crystal, and rectangular lattices, as well as the three-dimensional structure of CaF$_2$ crystal inhabited by a single particle species. We verify our results by cooling liquid configurations to absolute zero temperature via simulated annealing and ensuring that such states have stable phonon spectra. Except for the rectangular kagome structure, all of the target structures can be stabilized with monotonic repulsive potentials. Our work demonstrates that single-component systems with short-ranged radial pair potentials can counterintuitively self-assemble into crystal ground states with low symmetry and different local structural environments. Finally...

## Thermodynamical Test of Non Extensive Thermostatistics

Martinez, S.; Pennini, F.; Plastino, A.; Vucetich, H.
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
45.62%
An ideal mixture of parahydrogen (with nuclear spin K=0) and orthohydrogen (with K=1), in statistical weights 1/4 and 3/4, respectively, is used as a test ground for the existence of non-extensivity in chemical physics. We report on a new bound on the non extensivity parameter q - 1 that characterizes generalized thermostatistics a la Tsallis. This bound is obtained on the basis of laboratory measurements of the specific heat of hydrogen. Suggestions are advanced for the performance of improved measurements.; Comment: 4 pages, 1 figure

## Quantal distribution functions in non-extensive statistics and an early universe test revisited

Tirnakli, Ugur; Torres, Diego F.
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
45.55%
Within the context of non-extensive thermostatistics, we use the factorization approximation to study a recently proposed early universe test. A very restrictive bound upon the non-extensive parameter is presented: $|q-1| < 4.01 \times 10^{-3}$.; Comment: 4 pages, prl revtex style, no figures. To appear in Physica A, 1999

## Statistical mechanics models for multimode lasers and random lasers

Antenucci, F.; Crisanti, A.; Berganza, M. Ibáñez; Marruzzo, A.; Leuzzi, L.
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
45.62%
We review recent statistical mechanical approaches to multimode laser theory. The theory has proved very effective to describe standard lasers. We refer of the mean field theory for passive mode locking and developments based on Monte Carlo simulations and cavity method to study the role of the frequency matching condition. The status for a complete theory of multimode lasing in open and disordered cavities is discussed and the derivation of the general statistical models in this framework is presented. When light is propagating in a disordered medium, the system can be analyzed via the replica method. For high degrees of disorder and nonlinearity, a glassy behavior is expected at the lasing threshold, providing a suggestive link between glasses and photonics. We describe in details the results for the general Hamiltonian model in mean field approximation and mention an available test for replica symmetry breaking from intensity spectra measurements. Finally, we summary some perspectives still opened for such approaches.; Comment: 16 pages, 7 figures

## Statistical mechanics and the description of the early universe I.: Foundations for a slightly non-extensive cosmology

Pessah, M. E.; Torres, Diego F.; Vucetich, H.
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
45.59%
We analyze how the thermal history of the universe is influenced by the statistical description, assuming a deviation from the usual Bose-Einstein, Fermi-Dirac and Boltzmann-Gibbs distribution functions. These deviations represent the possible appearance of non-extensive effects related with the existence of long range forces, memory effects, or evolution in fractal or multi-fractal space. In the early universe, it is usually assumed that the distribution functions are the standard ones. Then, considering the evolution in a larger theoretical framework will allow to test this assumption and to place limits to the range of its validity. The corrections obtained will change with temperature, and consequently, the bounds on the possible amount of non-extensivity will also change with time. We generalize results which can be used in other contexts as well, as the Boltzmann equation and the Saha law, and provide an estimate on how known cosmological bounds on the masses of neutrinos are modified by a change in the statistics. We particularly analyze here the recombination epoch, making explicit use of the chemical potentials involved in order to attain the necessary corrections. All these results constitute the basic tools needed for placing bounds on the amount of non-extensivity that could be present at different eras and will be later used to study primordial nucleosynthesis.; Comment: 32 pages...

## Rigorous statistical detection and characterization of a deviation from the Gutenberg-Richter distribution above magnitude 8 in subduction zones

Pisarenko, V. F.; Sornette, D.
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
45.62%
We present a quantitative statistical test for the presence of a crossover c0 in the Gutenberg-Richter distribution of earthquake seismic moments, separating the usual power law regime for seismic moments less than c0 from another faster decaying regime beyond c0. Our method is based on the transformation of the ordered sample of seismic moments into a series with uniform distribution under condition of no crossover. The bootstrap method allows us to estimate the statistical significance of the null hypothesis H0 of an absence of crossover (c0=infinity). When H0 is rejected, we estimate the crossover c0 using two different competing models for the second regime beyond c0 and the bootstrap method. For the catalog obtained by aggregating 14 subduction zones of the Circum Pacific Seismic Belt, our estimate of the crossover point is log(c0) =28.14 +- 0.40 (c0 in dyne-cm), corresponding to a crossover magnitude mW=8.1 +- 0.3. For separate subduction zones, the corresponding estimates are much more uncertain, so that the null hypothesis of an identical crossover for all subduction zones cannot be rejected. Such a large value of the crossover magnitude makes it difficult to associate it directly with a seismogenic thickness as proposed by many different authors in the past. Our measure of c0 may substantiate the concept that the localization of strong shear deformation could propagate significantly in the lower crust and upper mantle...

## On the failure of the volume function in granular statistical mechanics and an alternative formulation

Blumenfeld, Raphael; Amitai, Shahar; Jordan, Joe F.; Hihinashvili, Rebecca
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
45.59%
We first show that the currently accepted statistical mechanics for granular matter is flawed. The reason is that it is based on the volume function, which depends only on a minute fraction of all the structural degrees of freedom and is unaffected by most of the configurational microstates. Consequently, the commonly used partition function underestimates the entropy severely. Secondly, we propose a new formulation, replacing the volume function with a connectivity function that depends on all the structural degrees of freedom and accounts correctly for the entire entropy. We discuss the advantages of the new formalism and derive explicit results for two- and three-dimensional systems. We test the formalism by calculating the entropy of an experimental two-dimensional system, as a function of system size, and showing that it is an extensive variable.; Comment: 5 pages, 3 figures

## The coverage probabililty of confidence intervals in regression after a preliminary F test

Kabaila, Paul; Farchione, Davide
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
45.69%
Consider a linear regression model with regression parameter beta=(beta_1,..., beta_p) and independent normal errors. Suppose the parameter of interest is theta = a^T beta, where a is specified. Define the s-dimensional parameter vector tau = C^T beta - t, where C and t are specified. Suppose that we carry out a preliminary F test of the null hypothesis H_0: tau = 0 against the alternative hypothesis H_1: tau not equal to 0. It is common statistical practice to then construct a confidence interval for theta with nominal coverage 1-alpha, using the same data, based on the assumption that the selected model had been given to us a priori(as the true model). We call this the naive 1-alpha confidence interval for theta. This assumption is false and it may lead to this confidence interval having minimum coverage probability far below 1-alpha, making it completely inadequate. Our aim is to compute this minimum coverage probability. It is straightforward to find an expression for the coverage probability of this confidence interval that is a multiple integral of dimension s+1. However, we derive a new elegant and computationally-convenient formula for this coverage probability. For s=2 this formula is a sum of a triple and a double integral and for all s>2 this formula is a sum of a quadruple and a double integral. This makes it easy to compute the minimum coverage probability of the naive confidence interval...

## Hiding solutions in random satisfiability problems: A statistical mechanics approach

Barthel, W.; Hartmann, A. K.; Leone, M.; Ricci-Tersenghi, F.; Weigt, M.; Zecchina, R.
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
45.59%
A major problem in evaluating stochastic local search algorithms for NP-complete problems is the need for a systematic generation of hard test instances having previously known properties of the optimal solutions. On the basis of statistical mechanics results, we propose random generators of hard and satisfiable instances for the 3-satisfiability problem (3SAT). The design of the hardest problem instances is based on the existence of a first order ferromagnetic phase transition and the glassy nature of excited states. The analytical predictions are corroborated by numerical results obtained from complete as well as stochastic local algorithms.; Comment: 5 pages, 4 figures, revised version to app. in PRL

## Experimental test of curvature-driven dynamics in the phase ordering of a two dimensional liquid crystal

Sicilia, Alberto; Arenzon, Jeferson J.; Dierking, Ingo; Bray, Alan J.; Cugliandolo, Leticia F.; Martinez-Perdiguero, Josu; Alonso, Ibon; Pintre, Inmaculada C.
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
45.58%
We study electric field driven deracemization in an achiral liquid crystal through the formation and coarsening of chiral domains. It is proposed that deracemization in this system is a curvature-driven process. We test this prediction using the exact result for the distribution of hull-enclosed areas in two-dimensional coarsening in non-conserved scalar order parameter dynamics recently obtained [J.J. Arenzon et al., Phys. Rev. Lett. 98, 061116 (2007)]. The experimental data are in very good agreement with the theory. We thus demonstrate that deracemization in such bent-core liquid crystals belongs to the Allen-Cahn universality class, and that the exact formula, which gives us the statistics of domain sizes during coarsening, can also be used as a strict test for this dynamic universality class.; Comment: 4 pages, 4 figures

## $1/f^\alpha$ noise and integrable systems

Barba, J. C.; Finkel, F.; Gonzalez-Lopez, A.; Rodriguez, M. A.
Tipo: Artigo de Revista Científica