Developmental constraints on vertebrate genome evolution

Constraints in embryonic development are thought to bias the direction of evolution by making some changes less likely, and others more likely, depending on their consequences on ontogeny. Here, we characterize the constraints acting on genome evolution in vertebrates. We used gene expression data from two vertebrates: zebrafish, using a microarray experiment spanning 14 stages of development, and mouse, using EST counts for 26 stages of development. We show that, in both species, genes expressed early in development (1) have a more dramatic effect of knock-out or mutation and (2) are more likely to revert to single copy after whole genome duplication, relative to genes expressed late. This supports high constraints on early stages of vertebrate development, making them less open to innovations (gene gain or gene loss). Results are robust to different sources of data-gene expression from microarrays, ESTs, or in situ hybridizations; and mutants from directed KO, transgenic insertions, point mutations, or morpholinos. We determine the pattern of these constraints, which differs from the model used to describe vertebrate morphological conservation ("hourglass" model). While morphological constraints reach a maximum at mid-development (the "phylotypic" stage), genomic constraints appear to decrease in a monotonous manner over developmental time

Simulation of neutrophil motion and deformation: influence of rheology and flow configuration

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Thalamocortical synchronization and cognition: implications for schizophrenia?

Cognitive deficits are a core dysfunction in schizophrenia. In this issue of Neuron, Parnaudeau et al. (2013) investigated synchronization in thalamocortical pathways in an animal model to address the disconnection between brain regions as a mechanism for working memory impairments in the disorder.implicated dysfunctional neural oscillations in the explanation of cognitive deficits and certain clinical symptoms of schizophrenia. Specifically, we will focus on findings that have examined neural oscillations during 1) perceptual processing, 2) working memory and executive processes and 3) spontaneous activity. The importance of the development of paradigms suitable for human and animal models is discussed as well as the search for mechanistic explanation for oscillatory dysfunctions

Dynamic glass transition: bridging the gap between mode-coupling theory and the replica approach

We clarify the relation between the ergodicity breaking transition predicted by mode-coupling theory and the so-called dynamic transition predicted by the static replica approach. Following Franz and Parisi [Phys. Rev. Lett. 79, 2486 (1997)], we consider a system of particles in a metastable state characterized by non-trivial correlations with a quenched configuration. We show that the assumption that in a metastable state particle currents vanish leads to an expression for the replica off-diagonal direct correlation function in terms of a replica off-diagonal static four-point correlation function. A factorization approximation for this function results in an approximate closure for the replica off-diagonal direct correlation function. The replica off-diagonal Ornstein-Zernicke equation combined with this closure coincides with the equation for the non-ergodicity parameter derived using the mode-coupling theory.Comment: revised version; to be published in EP

Vonnisoplegging by roof met verswarende omstandighede

Uit teks: In ’n saak wat op 6 September 2002 voor die Kaapse Provinsiale Afdeling gedien het, is die hof, by monde van Griesel R en Oosthuizen Wnr, met die interessante vraag gekonfronteer of daar verswarende omstandighede aanwesig is waar die klaer tydens ’n rooftog met ’n speelgoed vuurwapen gedreig is. Die klaer was nie ten tye van die rooftog bewus van die feit dat die beskuldigde nie met ’n ware vuurwapen gewapen was nie

Quasistatic granular material rheology from particle simulations

We report on the quasistatic behaviour of model granular materials, as probed by DEM simulations of isotropic compression and triaxial compression tests, focussing on the macroscopic behaviour dependence on control parameters expressed in dimensionless forms that combine contact laws with test conditions, and on the influence of the initial state. A discussion of the microscopic origins of strain, which in some situations of small strains and stable contact networks are due to contact deflections, and in other cases results from the continuous breaking and repairing of networks under varying loads provides a useful classification of rheological regimes. Some guidelines for parameter choices in numerical simulations, and for some homogenization approaches, are inferre

A Bayesian analysis for censored Rayleigh model using a generalised hypergeometric prior

Based on a type II censored sample, Bayesian estimation for the scale parameter of the Rayleigh model is carried out under the assumption of the squared error loss function. A generalised hypergeometric distribution with its versatile shape of tails is introduced as a prior, and beta special cases are examined. A simulation study is carried out to investigate the sensitivity of four special cases of this beta prior family in terms of bias, frequentist coverage and mean square error and to determine their effect on robustness. Prediction bounds are derived for the lifetime of unused components using this beta prior family. A data set is used to illustrate and support some of the findings

Mobile particles in an immobile environment: Molecular Dynamics simulation of a binary Yukawa mixture

Molecular dynamics computer simulations are used to investigate thedynamics of a binary mixture of charged (Yukawa) particles with a size-ratio of 1:5. We find that the system undergoes a phase transition where the large particles crystallize while the small particles remain in a fluid-like (delocalized) phase. Upon decreasing temperature below the transition, the small particles become increasingly localized on intermediate time scales. This is reflected in the incoherent intermediate scattering functions by the appearance of a plateau with a growing height. At long times, the small particles show a diffusive hopping motion. We find that these transport properties are related to structural correlations and the single-particle potential energy distribution of the small particles.Comment: 7 pages, 5 figure

Indigenous Zulu games as an educational tool for the multicultural schools in South Africa

Active participation, and formal and informal contact on sports fields and in physical education classes can contribute to the bridging of diversity in a play setting. This ties in with the Revised National Curriculum Statement for Life Orientation which emphasizes the holistic development of all learners. There are widespread concerns about the inactivity and related disease profiles of the South African Youth, as well as the divisions of the past that still prevail. A national need for indigenous knowledge was identified and the opportunity arose for documenting and selecting indigenous Zulu games as part of a national survey. This study developed from this background. It aims to provide material for socio-cultural development as well as to address the void in the current educational dispensation regarding physical education as part of the Life Orientation Learning Area. Quantitative data on the trends, content and nature of these games was collected through the completion of a questionnaire (De Jongh, 1984 and adapted by Burnett, 2001), triangulated with information collected through structured interviews, focus groups and observations of learners at play. Visual and tape recordings assisted in the capturing of songs, physical skills and various other play patterns. Forty indigenous Zulu games and other play related activities were collected from grade seven learners (age 10 to 17) (n=217), and adults (age 40 to 70) (n=57) from rural and urban schools and communities in and around Empangeni, Eshowe, Vryheid, Nongoma and Durban in the KwaZulu-Natal Province of South Africa. The sample (N=274) comprised of Zulu-speaking boys (n=87), girls (n=130), men (n=26) and women (n=31). A theoretical framework for inventorising Zulu play and games, was developed and applied for classification, analysis and documentation of these Zulu games. These games were presented in an educational outcomes-based framework and guidelines offered for the inclusion of indigenous games in a multicultural classroom. Thirteen of these games were, however, selected for curriculum development purposes according to the criteria of the nature (indigenous content and structure), popularity and potential for cross-field educational outcomes. Appropriate strategies were offered for teaching, learning and pedagogy. These thirteen selected indigenous Zulu games may meaningfully contribute to the physical education curriculum for promoting ethnic understanding, reinforcing social skills and to provide an opportunity to use fundamental motor skills and movement concepts in dynamic settings in the multicultural classroom in the South African context. It is recommended that these indigenous Zulu games should hence be introduced to all learners in the multicultural classrooms of all South African schools, providing that sufficient time will be allocated and subject specialists will be appointed for teaching physical education. Furthermore it is recommended that research should be conducted on the indigenous games of all other ethnic groups, not only the Zulu in KwaZulu-Natal, but throughout South Africa to be included in a comprehensive physical education curriculum.Prof. C. Burnett-Louw Prof. W.J. Hollande

Vonnisoplegging by roof met verswarende omstandighede

Uit teks: In ’n saak wat op 6 September 2002 voor die Kaapse Provinsiale Afdeling gedien het, is die hof, by monde van Griesel R en Oosthuizen WnR, met die interessante vraag gekonfronteer of daar verswarende omstandighede aanwesig is waar die klaer tydens ’n rooftog met ’n speelgoed vuurwapen gedreig is. Die klaer was nie ten tye van die rooftog bewus van die feit dat die beskuldigde nie met ’n ware vuurwapen gewapen was nie