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In situ observation of the formation process of mesophase of isotactic polypropylene (iPP) is reported in structural point of view. Combining a rapid temperature jump and a high-flux synchrotron radiation X-ray scattering techniques, very rapid transformation from the molten amorphous state to the mesophase has been observed. The transformation proceeded very quickly in a narrow temperature range accompanied by instantaneous fluctuations in micrometer scale, suggesting the mesophase formation proceeds similarly to spinodal decomposition.

Structure studies were performed on PVA gels in mixtures of dimethyl sulfoxide (DMSO) and water using various scattering methods to see the hierarchic structure. It was found that the crosslinking points are crystallites, the nearest-neighboring distance is 180–200 A and the bicontinuous structure due to phase separation is in μm scale for the gel in DMSO/water (60/40). Dynamics of three kinds of PVA gels were also studied in nm scale using neutron spin echo technique.

Cells of early mammalian embryos have the potential to develop into any adult cell type, and are thus said to be pluripotent. Pluripotency is lost during embryogenesis as cells commit to specific developmental pathways. Although restriction of developmental potential is often associated with repression of inappropriate genetic programmes1, the role of epigenetic silencing during early lineage commitment remains undefined. Here, we used mouse embryonic stem cells to study the function of epigenetic silencing in pluripotent cells. Embryonic stem cells lacking Mbd3 — a component of the nucleosome remodelling and histone deacetylation (NuRD) complex2,3 — were viable but failed to completely silence genes that are expressed before implantation of the embryo. Mbd3-deficient embryonic stem cells could be maintained in the absence of leukaemia inhibitory factor (LIF) and could initiate differentiation in embryoid bodies or chimeric embryos, but failed to commit to developmental lineages. Our findings define a role for epigenetic silencing in the cell-fate commitment of pluripotent cells.

Preface to the special issueConceptual Innovation in Polymer Science: Ichiro Sakurada Special Issue

Conformational Change and Orientation Fluctuations of Isotactic Polystyrene Prior to Crystallization

Low density polyethylene film is drawn at room temperature four times the original length and subjected to thermal annealing at 60, 80, and 100 °C keeping the film length constant. Long spacing measured by SAXS increased with increasing temperature of annealing; the increase of the long spacing is presumed to be due to the decrease of the number of micelles through relaxation during the annealing. Simultaneous measurement of the changes of the long spacing and the film length by stretching is carried out and stress-extension curves are obtained. The values of the initial moduli of the long spacingE 1 and the film lengthY are very near to each other. Elastic modulus of the crystal latticeE c is known to be 235 GN/m2 and that of the amorphous regionE a is found to be 0.15 GN/m2. When higher stress is applied than in the case of the initial modulus, the percentage of extension of film is much greater than that of the long spacing. The discrepancy is explained by the increase of the number of micelles through stress crystallization.