Genome sequence of the ultrasmall unicellular red alga Cyanidioschyzon merolae 10D

Small, compact genomes of ultrasmall unicellular algae provide information on the basic and essential genes that support the lives of photosynthetic eukaryotes, including higher plants. Here we report the 16,520,305-base-pair sequence of the 20 chromosomes of the unicellular red alga Cyanidioschyzon merolae 10D as the first complete algal genome. We identified 5,331 genes in total, of which at least 86.3% were expressed. Unique characteristics of this genomic structure include: a lack of introns in all but 26 genes; only three copies of ribosomal DNA units that maintain the nucleolus; and two dynamin genes that are involved only in the division of mitochondria and plastids. The conserved mosaic origin of Calvin cycle enzymes in this red alga and in green plants supports the hypothesis of the existence of single primary plastid endosymbiosis. The lack of a myosin gene, in addition to the unexpressed actin gene, suggests a simpler system of cytokinesis. These results indicate that the C. merolae genome provides a model system with a simple gene composition for studying the origin, evolution and fundamental mechanisms of eukaryotic cells.     

水附着状态下奥贝球铁断裂韧性的脆化行为

研究了水附着状态下奥贝球铁(ADI)断裂韧性的脆化行为．研究结果表明，干燥状态下ADI具有较高的断裂韧性，但水附着状态下ADI的弹塑性断裂韧性JIc降至干燥状态下的20％以下，发生显著的脆化行为；断裂韧性的脆化与试样水浸泡履历无关，长时间(480h)水浸泡试样经再干燥后，其断裂韧性恢复到原有水平．裂纹尖端附着的水在ADI基体塑性变形时分解放出氢，氢扩散至试样的内部使ADI基体中的应力诱变马氏体发生氢脆，导致了ADI断裂韧性的脆化．