7,696 research outputs found
Non-adiabatic Chaplygin gas
The split of a generalised Chaplygin gas with an equation of state p =
-A/\rho^{\alpha} into an interacting mixture of pressureless matter and a
dark-energy component with equation of state p_{\Lambda} = - \rho_{\Lambda}
implies the existence of non-adiabatic pressure perturbations. We demonstrate
that the square of the effective (non-adiabatic) sound speed c_s of the medium
is proportional to the ratio of the perturbations of the dark energy to those
of the dark matter. Since, as demonstrated explicitly for the particular case
\alpha = -1/2, dark-energy perturbations are negligible compared with
dark-matter perturbations on scales that are relevant for structure formation,
we find |c_s^2| << 1. Consequently, there are no oscillations or instabilities
which have plagued previous adiabatic Chaplygin-gas models.Comment: Version to appear in Physics Letters
Multidisciplinary support teams for inclusive education during emergency online teaching: experiences and practices on the pedagogical triangulations forum
The Pedagogical Triangulations – COVID19 school experiences: the journey was a multi- support iniciative that gave voice to several school actors during the experience of online emergency teaching or school at distance (referred to as E@Da) reflection. On May 26th 2020, members of three different EMAEI (Multidisciplinary Support Team for Inclusive Education) were invited to testify of the effort to maintain the inclusion and equity of all students, ensuring that none are left behind.info:eu-repo/semantics/publishedVersio
Decifrando o genoma.
Os genes, unidades biologicas que determinam as caracteristicas de um organismo, estao contidos em moleculas de DNA presentes no nucleo das celulas. Portanto, o estudo do DNA e de fundamental importancia para o entendimento de como as caracteristicas de um organismo sao formadas. Com o grande avanco alcancado pelas tecnicas de Biologia molecular nas ultimas decadas, hoje, somos capazes de isolar e sequenciar moleculas de DNA de maneira rotineira. A partir da otimizacao das tecnicas de sequenciamento, surgiram programas com o objetivo de sequenciar genomas inteiros. atualmente, estao depositados em bancos de dados mais de 3 milhoes de sequencias de DNA e, grande parte delas ainda nao tem sua funcao conhecida. O processo de caracterizacao da funcao genica envolve um volume muito maior de pesquisas e conhecimentos do que as etapas de isolamento e sequenciamento. A funcao de um gene pode ser desvendada por meio de tecnicas de genetica direta ou reversa. Descrevem-se algumas das metodologias usadas para a caracterizacao da funcao genica, bem como o potencial dos programas de sequenciamento de genomas
SuperexpressĂŁo do gene AltSB, aluminum tolerance Sorghum bicolor, em plantas transgĂŞncias de milho.
Qualidade da água na engorda de tambaqui em viveiros sem renovação da água.
bitstream/CPATC/19780/1/f_18_2007.pd
Equality of opportunity and educational achievement in Portugal
Portugal has one of the highest levels of income inequality in Europe, and low wages and unemployment are concentrated among low skill individuals. Education is an important determinant of inequality. However, there are large differences in the educational attainment of different individuals in the population, and the sources of these differences emerge early in the life-cycle when families play a central role in individual development. We estimate that most of the variance of school achievement at age 15 is explained by family characteristics. Observed school inputs explain very little of adolescent performance. Children from highly educated parents benefit of rich cultural environments in the home and become highly educated adults. Education policy needs to be innovative: (1) it needs to explicitly recognize the fundamental long run role of families on child development; (2) it needs to acknowledge the failure of traditional input based policies
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