We have investigated the electromigration process at gold nanojunctions as small as several tens of atoms. Junction conductance showed successive drops by one conductance quantum, corresponding to one-by-one removal of gold atoms, only when the junction voltage exceeded certain critical values. The peak position in the histogram of the observed critical voltages agreed with the activation energies for surface diffusion of gold atoms. This fact indicates that the elementary process of electromigration in such small junctions is the self-diffusion of metal atoms driven by microscopic kinetic energy transfer from a single conduction electron to a single metal atom.

We have fabricated single C(60) molecule transistors with ferromagnetic Ni leads (FM-SMTs) by using an electrical break junction method and investigated their magnetotransport. The FM-SMTs exhibited clear gate-dependent hysteretic tunnel magnetoresistance (TMR) and the TMR values reached as high as -80%. The polarity of the TMR was found to be always negative over the entire bias range studied here. Density functional theory calculations show that hybridization between the Ni substrate states and the C(60) molecular orbitals generates an antiferromagnetic configuration in the local density of states near the Fermi level, which gives a reasonable explanation for the observed negative TMR.

We have investigated terahertz (THz) photon-assisted tunneling in single self-assembled InAs quantum dots (QDs). Two types of photon-assisted tunneling processes have been observed in the THz range: ground state resonance and photon-induced excited state resonance, depending on the relative magnitude between the orbital quantization energy of the QDs and the THz photon energy. Furthermore, we could realize a very high coupling efficiency between THz waves and QDs and observed multiphoton absorption up to the fourth-order during the tunneling process, resulting in almost complete lifting of the Coulomb blockade.

In the present study, the effect of magnetic fields on the orientation of adherent cells was investigated quantitatively using a long-term magnetic field exposure system at 8 T. Smooth muscle cells, which are classified as adherent cells, were passaged and dispersed in Dulbecco's Modified Eagle's Medium (DMEM). A cell culture flask was filled to capacity with the smooth muscle cell suspension, and placed in the center of a superconducting magnet's bore. The smooth muscle cell culture was incubated for 3 days, and exhibited randomly oriented patterns of rod-like shaped cells without magnetic field exposure. In contrast, the smooth muscle cell culture exposed to 8 Tesla (T) magnetic fields for 70 hours changed into a one-directionally oriented cell culture. To quantify the orientational order, an orientational order parameter for a 2-dimensional system was introduced by adapting the 3-dimensional order parameter. The degree of orientation of the culture with 8 T magnetic field exposure for 70 hours was 0.72, while the degree of orientation without exposure was 0.21. The results indicated that the magnetic orientational order of smooth muscle cells was lower than that of floating cells.