No abstract

We propose a new model for the Fe-oxide concretion formation on Earth and that can also explain the early martian history.

Carbonate concretions occur in sedimentary rocks of widely varying geological ages throughout the world. Many of these concretions are isolated spheres, centered on fossils. The formation of such concretions has been variously explained by diffusion of inorganic carbon and organic matter in buried marine sediments. However, details of the syn-depositional chemical processes by which the isolated spherical shape developed and the associated carbon sources are little known. Here we present evidence that spherical carbonate concretions (diameters φ : 14 ~ 37 mm) around tusk-shells (Fissidentalium spp.) were formed within weeks or months following death of the organism by the seepage of fatty acid from decaying soft body tissues. Characteristic concentrations of carbonate around the mouth of a tusk-shell reveal very rapid formation during the decay of organic matter from the tusk-shell. Available observations and geochemical evidence have enabled us to construct a ‘Diffusion-growth rate cross-plot’ that can be used to estimate the growth rate of all kinds of isolated spherical carbonate concretions identified in marine formations. Results shown here suggest that isolated spherical concretions that are not associated with fossils might also be formed from carbon sourced in the decaying soft body tissues of non-skeletal organisms with otherwise low preservation potential.

No abstract

We show an unconscious self-assembling ability of block copolymers, that is, spontaneous perpendicular orientation of nanocylinders in a block copolymer thick film of polystyrene-block-polyethylenebutylene-block-polystyrene (SEBS) triblock copolymer. The perpendicular orientation of cylinders was obtained when the SEBS sample underwent morphological transition from spheres to cylinders, which was mediated by directional coalescence of spheres normal to the film sample. The direction of the cylinder orientation is determined already by the direction of the solvent evaporation, which can be referred to as an effect of a chemical potential gradient. We have not been aware of such self-assembling ability of block copolymers. Its robustness can be identified in a thick film (about 1 mm thickness), and it is expected that this opens up a wide use of block copolymers as a self-sustaining film in many practical applications.