An approach to deduce the mechanism of stabilization of the hybrid-derived populations in the Ohomopterus ground beetles has been made by comparative studies on the phylogenetic trees of the mitochondrial and nuclear DNA. A phylogenetic tree based on the internal transcribed spacer (ITS) of nuclear ribosomal gene roughly reflects the relations of morphological species group, while mitochondrial NADH dehydrogenase subunit 5 (ND5) gene shows a considerable different topology on the tree; there exist several geographically-linked lineages, most of which consist of more than one species. These results suggest that the replacement of mitochondria has occurred widely in the Ohomopterus species. In most cases, hybridization is unidirectional, i.e., the species A (♂) hybridized with another species B (♀) and not vice versa, with accompanied replacement of mitochondria of A by those of B. The results also suggest that partial or complete occupation of the distribution territory by a hybrid-derived morphological species. The morphological appearance of the resultant hybrid-derivatives are recognized as that of the original species A. Emergence of a morphological new species from a hybrid-derived population has been exemplified. 相似文献
The duality relations are derived for the n-layered q-state Potts model (symmetrically coupled Potts model on an n-layered lattice). The self-duality conditions for general n are obtained on the square lattice and it is found that the model is self-dual under those conditions. As special cases, the self-duality conditions are examined in detail for n = 3 and 4. 相似文献
In 1985, we reported that a bacterium, Mycoplasma capricolum, used a deviant genetic code, namely UGA, a "universal" stop codon, was read as tryptophan. This finding, together with the deviant nuclear genetic codes in not a few organisms and a number of mitochondria, shows that the genetic code is not universal, and is in a state of evolution. To account for the changes in codon meanings, we proposed the codon capture theory stating that all the code changes are non-disruptive without accompanied changes of amino acid sequences of proteins. Supporting evidence for the theory is presented in this review. A possible evolutionary process from the ancient to the present-day genetic code is also discussed. 相似文献
Summary: The phase development mechanism during drawing from a highly entangled melt of ultra‐high‐molecular‐weight polyethylene is analyzed by simultaneous measurements of in situ X‐ray diffraction using synchrotron radiation and stress/strain behavior. The stress/strain curve exhibits a plateau region at the initial stage of the draw, and no crystalline reflections appear on a series of in situ X‐ray diffraction patterns. However, as the sample draw proceeds above a critical strain, a metastable hexagonal reflection appears and becomes predominant, where the stress/strain curve still shows a plateau deformation. With a further increase of the strain, the intensity of the hexagonal reflection peak begins to decrease and subsequently that of the usual orthorhombic ones increase. Correspondingly, a rapid increase of draw stress, because of the strain‐hardening behavior, is recorded.
Stacked line profiles extracted from in situ WAXD patterns along the equatorial direction. The red profile was obtained at the critical time of 162.5 s. 相似文献
Oriented polyethylene (PE) films with surfaces bounded by the (100) plane were prepared. On the film surfaces, isotactic polypropylene (iPP) was crystallized epitaxially from solution as quadrits with their sides parallel and perpendicular to the polyethylene chain axis. In the through wide-angle x-ray diffraction pattern (taken with incident x-rays normal to the polyethylene film surface), the 111 iPP reflections was observed on the meridian (Parallel to the polyethylene chain axis). In the edge patterns (taken with x-rays incident on the edge of the polyethylene film), 040 and 060 reflections were observed on the equator. From the diffraction patterns, the following lattice coincidence was observed between polyethylene and isotactic polypropylene: (010)iPP//(100) PE, [101]iPP//[001] PE. The Small-angle x-ray scattering patterns showed that edge-on isotactic polypropylene lamellae 9 nm thick were arranged with their long axes inclined at an angle of 40° from the polyethylene axis. Molecular chains were oriented within the lamellae normal to the surfaces. 相似文献
Several kinds of copolymers bearing O-acyloxyimino groups were prepared and their photodegradabilities were examined. Copolymers of O-methacryloyl ketone (acetophenone, benzophenone, or 2-acetonaphthone) oxime and methyl methacrylate (or styrene) were photodegradable even in the solid phase but in the case of copolymers of O-acryloyl acetophenone oxime and methyl methacrylate (or styrene) both photodegradation and photocrosslinking were observed. From these results it was found that the photodegradability of the copolymers was not dependent on the comonomer (methyl methacrylate or styrene) but dependent on the structure of the monomer bearing O-acyloxyimino groups. From detailed analysis of photodegradation of the copolymer of O-methacyloyl acetophenone oxime and methyl methacrylate in the presence of benzophenone it was found that the benzophenone worked not only as a sensitizer for the decomposition of O-acyloxyimino groups but also as a plasticizer to assist segment motions of polymer chains and the diffusion of oxygen in the film. 相似文献
Changes in the crystalline structure during heating of melt-drawn ultrahigh molecular weight polyethylenes (UHMW-PEs) having different molecular characteristics were analyzed by in situ wide-angle X-ray diffraction measurements. A phase transition from the orthorhombic into the hexagonal phase was observed for all samples, but the perfection was enhanced and the possible temperature window for the hexagonal phase was greater for the sample containing only a higher molecular weight component. In contrast, an increase in retractive stress during heating was confirmed for the sample containing a lower molecular weight component, reflecting melting of the folded-chain crystal (FCC). Differential scanning calorimetry and transmission electron microscopy revealed the dependency of the molecular characteristics of the sample on the resultant morphologies. These results demonstrate that the existence of FCC determines both the quality and the width of the temperature window for the hexagonal phase during heating of melt-drawn UHMW-PEs. 相似文献