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Biomedical subjects

M Kamiya

Publications and source records attributed to M Kamiya.

At least 217 records · Page 12Linked to original sources

The induced circular dichroism of proflavine intercalated to DNA. Dye-polymer exciton interactions.

The circular dichroism induced in the visible absorption band of proflavine cation isolatedly intercalated to DNA was investigated in terms of the dye-DNA base pair exciton interaction. The remarkable ionic strength dependence of the induced CD magnitude was in good accord with the CD magnitude calculated on the basis of the dye-polymer Frenkel exciton interaction model and under the extent of helix deformation required for intercalation. In particular the application of the internal and modified intercalation models coupled with the deep trap approximation implied that the preference of the modified intercalation due to electrostatic interaction between the acridine-nitrogen atom and the DNA phosphate group is combined with relatively high ionic strength compared with the internal intercalation.

Acridines↗

Spin-orbit couplings in the DNA base pairs.

The radiative lifetimes of the phosphorescent states of the adenine.thymine (A.T) and guanine.cytosine (G.C) base pairs were calculated on the basis of the singlet-triplet transition probability induced by spin-orbit couplings. The calculated radiative lifetimes averaged over the triplet sublevels of spin state were in the order of G.C less than A.T and in good correlation with those of the composite bases. On the whole the results suggested an important role for thymine triplet having a relatively long lifetime during the course of the triplet localization in DNA, in agreement with the experimental observation that the concentration of triplet is remarkably enhanced with increase in A+T content.

Chemical Phenomena↗

Fractography of human intact long bone by bending.

Human intact tibiae were tested using the static bending method to learn about the relationship between the fracture surface and the failure mode. The bending test was applied to test pieces and to whole bones. The fracture surface was observed by scanning electron microscopy. The bone fracture is closely related to the architecture of the bone substance, especially to the direction of the Haversian canals and the lamellae. The failure mode and the sequence of the break line of the bone can be found out by the observation on the fracture surface. Hardly any crushing effects caused by the compressive force is seen. The mechanical properties of the fractured bone can be estimated to some extend by considering the direction of the break line and the failure mode. The strength calculated by the simple beam formula for elastic materials can not be obtained directly because of the plastic deformation of the bone. The results of the tensile test may be applied to the fracture using the static bending moment.

Biomechanical Phenomena↗