Study of the Effect of Lighting Technology in Texture Classification Systems

This work has been performed under support of the Spanish MEC project reference DPI2007- 6312

Test of hypothesis on the coefficient of coancestry in haploid populations

Neste trabalho foram estudadas as distribuições dos quadrados médios na análise de variância com as freqüências alélicas em amostras de indivíduos extraídas em populações haplóides, procurando avaliar o uso do teste F para testar a hipótese de nulidade do coeficiente de coancestria. Foi demonstrado que as expressões da soma de quadrados entre populações e da soma de quadrados entre indivíduos dentro de populações divididas pelas respectivas esperanças de quadrados médios possuem distribuições de χ2 aproximadas, indicando que o quociente entre os quadrados médios na análise de variância tem distribuição F aproximada. Um estudo de simulação foi realizado comparando-se os valores experimentais simulados com os da distribuição teórica de F, procurando-se avaliar a validade das aproximações sugeridas. Os resultados mostraram que o teste F pode ser usado para testar a hipótese de nulidade do coeficiente de coancestria quando se trabalha com pelo menos cinco populações apresentando freqüência alélica média entre 0,3 e 0,7 utilizando-se no mínimo 50 indivíduos.The distribution of the allelic frequency mean squares in the analysis of variance of samples of individuals from haploid populations were studied to evaluate the Snedecor F test, for testing the null hypothesis relative to the coancestry coefficient. It was found that the distribution of the sum of the squares among populations and the sum of squares among individuals within the populations divided by the respective expected mean squares had distribution following approximately the χ2, indicating that the quotient among the mean squares of the analysis of variance approximate the F distribution. A simulation study to validate the suggested approximations, comparing the simulated values to those of the theoretic F distribution, was carried out. The results showed that the F test may be used to test the coancestry coefficient null hypothesis, when the allelic frequency is between 0.3 and 0.7, working with 50 individuals

Combined fit to the spectrum and composition data measured by the Pierre Auger Observatory including magnetic horizon effects

The measurements by the Pierre Auger Observatory of the energy spectrum and mass composition of cosmic rays can be interpreted assuming the presence of two extragalactic source populations, one dominating the flux at energies above a few EeV and the other below. To fit the data ignoring magnetic field effects, the high-energy population needs to accelerate a mixture of nuclei with very hard spectra, at odds with the approximate E$^{-2}$ shape expected from diffusive shock acceleration. The presence of turbulent extragalactic magnetic fields in the region between the closest sources and the Earth can significantly modify the observed CR spectrum with respect to that emitted by the sources, reducing the flux of low-rigidity particles that reach the Earth. We here take into account this magnetic horizon effect in the combined fit of the spectrum and shower depth distributions, exploring the possibility that a spectrum for the high-energy population sources with a shape closer to E$^{-2}$ be able to explain the observations