We study morphological transitions between microphase-separated structures in diblock copolymers. By means of the two-mode approximation, kinetics of order−disorder (ODT) and order−order transitions (OOT) in the weak-segregation limit are investigated by solving numerically a coupled set of the amplitude equations for the fundamental modes. Breakup and reconnection of domains during the morphological transitions are explored in detail. Furthermore, we identify the metastable or unstable intermediate structures which appear in the process of ODT and OOT. The linear stability analysis is also applied to see the most unstable mode when a lamellar structure is destabilized.

The sporulation-essential gene spolIG of the S1 nuclease mapping experiments indicate that ORF3 is initially cotranscribed with spoliG from about 1 to 4 hr into the sporulation process and that later on ORF3 is transcribed independently from a new site located between spolIG and ORF3. The role of ORF3 was investigated by constructing a deletion mutation in its structural gene. The mutant exhibits normal growth but is unable to produce heat-resistant spores. We propose that the ORF3 gene product is a af factor or a related peptide essential for sporulation at a late stage of development.

Three mammalian Period (Per) genes, termed Per1, Per2, and Per3, have been identified as structural homologues of the Drosophila circadian clock gene, period (per). The three Per genes are rhythmically expressed in the suprachiasmatic nucleus (SCN), the central circadian pacemaker in mammals. The phases of peak mRNA levels for the three Per genes in the SCN are slightly different. Light sequentially induces the transcripts of Per1 and Per2 but not of Per3 in mice. These data and others suggest that each Per gene has a different but partially redundant function in mammals. To elucidate the function of Per1 in the circadian system in vivo, we generated two transgenic rat lines in which the mouse Per1 (mPer1) transcript was constitutively expressed under the control of either the human elongation factor-1␣ (EF-1␣) or the rat neuronspecific enolase (NSE) promoter. The transgenic rats exhibited an Ϸ0.6 -1.0-h longer circadian period than their wild-type siblings in both activity and body temperature rhythms. Entrainment in response to light cycles was dramatically impaired in the transgenic rats. Molecular analysis revealed that the amplitudes of oscillation in the rat Per1 (rPer1) and rat Per2 (rPer2) mRNAs were significantly attenuated in the SCN and eyes of the transgenic rats. These results indicate that either the level of Per1, which is raised by overexpression, or its rhythmic expression, which is damped or abolished in over expressing animals, is critical for normal entrainment of behavior and molecular oscillation of other clock genes.transgenic rats ͉ entrainment

We investigate three-dimensional Turing patterns in two-component reaction diffusion systems. The FitzHugh-Nagumo equation, the Brusselator, and the Gray-Scott model are solved numerically in three dimensions. Several interconnected structures of domains as well as lamellar, hexagonal, and spherical domains are obtained as stable motionless equilibrium patterns. The relative stability of these structures is studied analytically based on the reduction approximation. The relation with the microphase-separated structures in block copolymers is also discussed.