Development of Seebeck-Coefficient Measurement Systems Using Kelvin-Probe Force Microscopy

Thermoelectric device is investigated by a number of researchers in order to enhance the thermoelectric efficiency. It is known that the efficiency can be improved by quantum effect. However, it is difficult to measure the thermoelectric characteristics of nanometer-scale structures. Thus a new measurement method is expected to be developed. We propose to apply Kelvin-probe force microscopy (KFM) to characterization of thermoelectric materials. KFM can locally observe surface potential of Fermi energy of a sample without touching the sample surface. In the present paper, we estimate the Seebeck coefficient of thin Si-on-insulator layers using KFM

Augmentation of Neovascularizaiton in Hindlimb Ischemia by Combined Transplantation of Human Embryonic Stem Cells-Derived Endothelial and Mural Cells

BACKGROUND: We demonstrated that mouse embryonic stem (ES) cells-derived vascular endothelial growth factor receptor-2 (VEGF-R2) positive cells could differentiate into both endothelial cells (EC) and mural cells (MC), and termed them as vascular progenitor cells (VPC). Recently, we have established a method to expand monkey and human ES cells-derived VPC with the proper differentiation stage in a large quantity. Here we investigated the therapeutic potential of human VPC-derived EC and MC for vascular regeneration. METHODS AND RESULTS: After the expansion of human VPC-derived vascular cells, we transplanted these cells to nude mice with hindlimb ischemia. The blood flow recovery and capillary density in ischemic hindlimbs were significantly improved in human VPC-derived EC-transplanted mice, compared to human peripheral and umbilical cord blood-derived endothelial progenitor cells (pEPC and uEPC) transplanted mice. The combined transplantation of human VPC-derived EC and MC synergistically improved blood flow of ischemic hindlimbs remarkably, compared to the single cell transplantations. Transplanted VPC-derived vascular cells were effectively incorporated into host circulating vessels as EC and MC to maintain long-term vascular integrity. CONCLUSIONS: Our findings suggest that the combined transplantation of human ES cells-derived EC and MC can be used as a new promising strategy for therapeutic vascular regeneration in patients with tissue ischemia

Partially disordered spin structure in Ag_{2}CrO_{2} studied with μ^{+}SR

The magnetism of a metallic two-dimensional triangular antiferromagnetic (AF) compound, Ag2CrO2, has been investigated by muon-spin rotation and relaxation (mu+SR) using a powder sample in the temperature range between 1.8 and 40 K. Below T-N = 24 K, a muon-spin precession signal was clearly observed in the zero-field spectrum, indicating the formation of static AF order. It was also found that the internal field is temperature independent except for in the vicinity of T-N, as in the case for the susceptibility versus temperature curve. This suggests that the AF transition is induced by a first-order structural phase transition at T-N. Combining the mu+SR result with the prediction for muon sites in the lattice by first-principles calculations, a partially disordered AF state was found to be the most reasonable spin structure for Ag2CrO