High temperatures during rice grain ripening reduced yield and grain quality. The proportion of milky white grains was 43.6 % at 30°C but only 6.5 % at 25°C. Grain filling was initially faster at 30°C and finished earlier, and the final dry matter content was less, than at 25°C. High temperature strongly suppressed the expression of the sucrose transporter gene OsSUT1 and starch synthesisrelated genes SuSy2, AGPS2b, BEIIb and Granule-bound starch synthase in grains during early grain filling; the transcription levels of OsSUT1 at 14 days after flowering (DAF) were about 60 % lower in grains, flag leaf blade, flag leaf sheath and first leaf sheath. These facts are possibly involved in the earlier termination of grain filling at 21 DAF, following the rapid rise of grain dry weight from 0 to 7 DAF, due to possible reduction in assimilate supply via OsSUT1 under the high temperature. When panicles were partly clipped, the resultant increase in assimilate supply to the remaining grains significantly upregulated the expression of OsSUT1 and the starch synthesis-related genes at 14 DAF, which consequently accelerated starch accumulation in the grains and ultimately increased the grain weight of remaining grains at 30°C. These results indicate that high temperature during grain filling reduces grain yield and quality by changing the expression of OsSUT1 and starch synthase-related genes, resulting in earlier ripening due to hastened or premature assimilate supply to grains.
A monolayer of dodecanethiol-stabilized gold nanoparticles changed into two-dimensional and three-dimensional self-organized structures by annealing at 323 K. Subsequent crystal growth of gold nanoparticles occurred. Thiol molecules, although chemisorbed, form relatively unstable bonds with the gold surface; a few thiols desorbed from the surface and oxidized to disulfides at 323 K, because the interaction energy between thiol macromolecules is larger than that between a thiol and a nanoparticle. The gold nanoparticles approached each other and grew into large single or twinned crystals because of the van der Waals attraction and the heat generated by the exothermic formation of disulfides.
The mechanism of crystalline Si island formation from an amorphous film was discussed in relation to the free energy of the Si/SiO2 system. Agglomeration of the Si crystallite occurred forming islands, thus preventing a further increase in free energy. Crystal growth proceeded in two steps. At first, the size distribution of Si islands was unimodal but finally became bimodal during the crystallization process.
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