Confidence and competence with mathematical procedures

Confidence assessment (CA), in which students state alongside each of their answers a confidence level expressing how certain they are, has been employed successfully within higher education. However, it has not been widely explored with school pupils. This study examined how school mathematics pupils (N = 345) in five different secondary schools in England responded to the use of a CA instrument designed to incentivise the eliciting of truthful confidence ratings in the topic of directed (positive and negative) numbers. Pupils readily understood the negative marking aspect of the CA process and their facility correlated with their mean confidence with r = .546, N = 336, p < .001, indicating that pupils were generally well calibrated. Pupils’ comments indicated that the vast majority were positive about the CA approach, despite its dramatic differences from more usual assessment practices in UK schools. Some pupils felt that CA promoted deeper thinking, increased their confidence and had a potential role to play in classroom formative assessment

The Caenorhabditis elegans GATA Factor ELT-1 Works through the Cell Proliferation Regulator BRO-1 and the Fusogen EFF-1 to Maintain the Seam Stem-Like Fate

Seam cells in Caenorhabditis elegans provide a paradigm for the stem cell mode of division, with the ability to both self-renew and produce daughters that differentiate. The transcription factor RNT-1 and its DNA binding partner BRO-1 (homologues of the mammalian cancer-associated stem cell regulators RUNX and CBFβ, respectively) are known rate-limiting regulators of seam cell proliferation. Here, we show, using a combination of comparative genomics and DNA binding assays, that bro-1 expression is directly regulated by the GATA factor ELT-1. elt-1(RNAi) animals display similar seam cell lineage defects to bro-1 mutants, but have an additional phenotype in which seam cells lose their stem cell-like properties and differentiate inappropriately by fusing with the hyp7 epidermal syncytium. This phenotype is dependent on the fusogen EFF-1, which we show is repressed by ELT-1 in seam cells. Overall, our data suggest that ELT-1 has dual roles in the stem-like seam cells, acting both to promote proliferation and prevent differentiation

The EFF-1A Cytoplasmic Domain Influences Hypodermal Cell Fusions in C. elegans But Is Not Dependent on 14-3-3 Proteins.

BACKGROUND: Regulatory and biophysical mechanisms of cell-cell fusion are largely unknown despite the fundamental requirement for fused cells in eukaryotic development. Only two cellular fusogens that are not of clear recent viral origin have been identified to date, both in nematodes. One of these, EFF-1, is necessary for most cell fusions in Caenorhabditis elegans. Unregulated EFF-1 expression causes lethality due to ectopic fusion between cells not developmentally programmed to fuse, highlighting the necessity of tight fusogen regulation for proper development. Identifying factors that regulate EFF-1 and its paralog AFF-1 could lead to discovery of molecular mechanisms that control cell fusion upstream of the action of a membrane fusogen. Bioinformatic analysis of the EFF-1A isoform\u27s predicted cytoplasmic domain (endodomain) previously revealed two motifs that have high probabilities of interacting with 14-3-3 proteins when phosphorylated. Mutation of predicted phosphorylation sites within these motifs caused measurable loss of eff-1 gene function in cell fusion in vivo. Moreover, a human 14-3-3 isoform bound to EFF-1::GFP in vitro. We hypothesized that the two 14-3-3 proteins in C. elegans, PAR-5 and FTT-2, may regulate either localization or fusion-inducing activity of EFF-1. METHODOLOGY/PRINCIPAL FINDINGS: Timing of fusion events was slightly but significantly delayed in animals unable to produce full-length EFF-1A. Yet, mutagenesis and live imaging showed that phosphoserines in putative 14-3-3 binding sites are not essential for EFF-1::GFP accumulation at the membrane contact between fusion partner cells. Moreover, although the EFF-1A endodomain was required for normal rates of eff-1-dependent epidermal cell fusions, reduced levels of FTT-2 and PAR-5 did not visibly affect the function of wild-type EFF-1 in the hypodermis. CONCLUSIONS/SIGNIFICANCE: Deletion of the EFF-1A endodomain noticeably affects the timing of hypodermal cell fusions in vivo. However, prohibiting phosphorylation of candidate 14-3-3-binding sites does not impact localization of the fusogen. Hypodermal membrane fusion activity persists when 14-3-3 expression levels are reduced

Creating and knowing mathematics through language and experience

The radical constructivist assertion that the student constructs his or her own knowledge as opposed to receiving it ldquoready maderdquo echoes the classical debate as to whether the human subject constitutes the world or is constituted by it. This paper shows how the philosophical traditions of post-structuralism and hermeneutic phenomenology offer approaches to effacing this dichotomy and how this forces a re-assertion of the teacher's role in the student's constructing of mathematical knowledge. It is also shown how hermeneutic phenomenology provides an opportunity to ground constructivist mathematical thinking in the material qualities of the world

Modification des acides sialiques de surface des hématies au cours de l’infestation

Les acides sialiques de surface des hématies de souris infestées par le parasite Plasmodium chabaudi sont augmentés comparativement à ceux d’hématies de souris non infestées. Cette augmentation coïncide avec celle des réticulocytes circulants. Une augmentation similaire des acides sialiques de surface est montrée par l’étude des réticulocytes induits par phénylhydrazine. De la même façon, les oses neutres et le fucose sont trouvés en quantité plus importante dans les glycopeptides trypsiques de surface desréticulocytes que dans les glycopeptides trypsiques de surface des hématies. Cette augmentation se retrouve dans les hématies de souris infestées par Plasmodium chabaudi, parallèlement à la valeur de la réticulocytémie. Ceci suggère la contribution significative des réticulocytes aux variations biochimiques observées des hématies infestées au cours de la malaria