Aoyama Gakuin University

About: Aoyama Gakuin University is a education organization based out in Tokyo, Japan. It is known for research contribution in the topics: Superconductivity & Thin film. The organization has 3494 authors who have published 6419 publications receiving 115648 citations. The organization is also known as: Aoyama gakuin daigaku.

Directly Observing the Motion of DNA Molecules near Solid-State Nanopores

Abstract: We investigate the diffusion and the drift motion of λ DNA molecules near solid-state nanopores prior to their translocation through the nanopores using fluorescence microscopy. The radial dependence of the electric field near a nanopore generated by an applied voltage in ionic solution can be estimated quantitatively in 3D by analyzing the motion of negatively charged DNA molecules. We find that the electric field is approximately spherically symmetric around the nanopore under the conditions investigated. In addition, DNA clogging at the nanopore was directly observed. Surprisingly, the probability of the clogging event increases with increasing external bias voltage. We also find that DNA molecules clogging the nanopore reduce the electric field amplitude at the nanopore membrane surface. To better understand these experimental results, analytical method with Ohm's law and computer simulation with Poisson and Nernst-Planck (PNP) equations are used to calculate the electric field near the nanopore. These results are of great interest in both experimental and theoretical considerations of the motion of DNA molecules near voltage-biased nanopores. These findings will also contribute to the development of solid-state nanopore-based DNA sensing devices.

Electron-phonon interaction and itinerant-electron ferromagnetism

Abstract: Starting from a consideration of how the phonon frequency would change with the spin splitting of the conduction-electron energy bands in an itinerant-electron ferromagnet, we find that in the paramagnetic region the effect of the electron-phonon interaction makes the temperature dependence of the spin susceptibility Curie-Weiss-type, with the Curie temperature ${T}_{C}$ much lower than in the Stoner theory. Further, for $Tl{T}_{C}$ we find that the phonon effect on magnetization can be large enough to account for the anomalous temperature dependence of spontaneous magnetization often observed in itinerant-electron ferromagnets, especially in Invar alloys. To confirm such a conclusion, with the same model and approximation we discuss also the very closely related problem of the magnetic field effect on the sound velocity in an itinerant-electron ferromagnet, and our theory is found to explain satisfactorily the varied observed results for both $Tg{T}_{C}$ and $Tl{T}_{C}$.