Strong Electron Confinement By Stacking-fault Induced Fractional Steps on Ag(111) Surfaces

The electron reflection amplitude $R$ at stacking-fault (SF) induced fractional steps is determined for Ag(111) surface states using a low temperature scanning tunneling microscope. Unexpectedly, $R$ remains as high as $0.6 \sim 0.8$ as energy increases from 0 to 0.5 eV, which is in clear contrast to its rapidly decreasing behavior for monatomic (MA) steps [L. B{\"u}rgi et al., Phys. Rev. Lett. \textbf{81}, 5370 (1998)]. Tight-binding calculations based on {\em ab-initio} derived band structures confirm the experimental finding. Furthermore, the phase shifts at descending SF steps are found to be systematically larger than counterparts for ascending steps by $\approx 0.4 \pi$. These results indicate that the subsurface SF plane significantly contributes to the reflection of surface states

One-dimensional surface states on a striped Ag thin film with stacking fault arrays

One-dimensional (1D) stripe structures with a periodicity of 1.3 nm are formed by introduction of stacking fault arrays into a Ag thin film. The surface states of such striped Ag thin films are studied using a low temperature scanning tunneling microscope. Standing waves running in the longitudinal direction and characteristic spectral peaks are observed by differential conductance (dI/dV) measurements, revealing the presence of 1D states on the surface stripes. Their formation can be attributed to quantum confinement of Ag(111) surface states into a stripe by stacking faults. To quantify the degree of confinement, the effective potential barrier at the stacking fault for Ag(111) surface states is estimated from independent measurements. A single quantum well model with the effective potential barrier can reproduce the main features of dI/dV spectra on stripes, while a Kronig-Penney model fails to do so. Thus the present system should be viewed as decoupled 1D states on individual stripes rather than as anisotropic 2D Bloch states extending over a stripe array.Comment: 10 pages, 6 figure

Functioning transferred free muscle innervated by part of the vascularized ulnar nerve connecting the contralateral cervical seventh root to themedian nerve: case report

<p>Abstract</p> <p>Background</p> <p>The limited nerve sources available for the reconstruction and restoration of upper extremity function is the biggest obstacle in the treatment of brachial plexus injury (BPI). We used part of a transplanted vascularized ulnar nerve as a motor source of a free muscle graft.</p> <p>Case presentation</p> <p>A 21-year-old man with a left total brachial plexus injury had received surgical intercostal nerve transfer to the musculocutaneous nerve and a spinal accessory nerve transfer to the suprascapular nerve in another hospital previously. He received transplantation of a free vascularized gracilis muscle, innervated by a part of the transplanted vascularized ulnar nerve connecting the contralateral healthy cervical seventh nerve root (CC7) to the median nerve, and recovered wrist motion and sensation in the palm. At the final examination, the affected wrist could be flexed dorsally by the transplanted muscle, and touch sensation had recovered up to the base of each finger. When his left index and middle fingers were touched or scrubbed, he felt just a mild tingling pain in his right middle fingertip.</p> <p>Conclusion</p> <p>Part of the transplanted vascularized ulnar nerve connected to the contralateral healthy cervical seventh nerve root can be used successfully as a motor source and may be available in the treatment of patients with BPI with scanty motor sources.</p

Effect of ZrC phase on high-temperature strength and room-temperature fracture toughness of ZrC-added Mo-Si-B alloys

Mo-Si-B-based alloys are one of leading candidate materials as ultra-high temperature structure materials. However, their high density and poor room-temperature fracture toughness have to be improved for the structural applications. Recently, we found that these problems can be solved by adding carbides such as TiC and ZrC. In this study, the high-temperature strength and room-temperature fracture toughness of ZrC-added Mo-Si-B alloys were investigated, and the effect of ZrC phase on the material properties were discussed. ZrC-added Mo-Si-B alloys (Mo-(3.2-7.0)Si-(6.5-14.0)B-(4.7-12.9)ZrC (at.%)) were prepared by arc-melting and heat-treated at 1800 °C for 24 h for homogenization. After heat-treatment, the microstructure was observed to investigate phase equilibria. Moreover, high-temperature compression tests at 1400 and 1600 °C and four-point bending tests with a Chevron notch at room temperature were conducted to investigate their mechanical properties. The constituent phases of the ZrC-added alloys were molybdenum solid solution (Moss), Mo5SiB2, ZrC and a small amount of Mo2B in a few cases. The density of the alloys ranged from 8.9 to 9.3 g/cm3, comparable to that of nickel-based superalloys. The alloys exhibited better high-temperature strength with relatively good deformability, for example, 1260 MPa at 1400 °C and 830 MPa at 1600 °C. The room-temperature fracture toughness of the alloys ranged from 12.4 to 20.3 MPa(m)1/2 depending on the volume fraction of Moss and ZrC. River patterns were observed on fracture surfaces of not only Moss but also ZrC phase, suggesting that ZrC also work for toughening by plastic deformation during crack propagation. Therefore ZrC plays a significant role in improving the high-temperature strength and room-temperature fracture toughness in the Mo-Si-B system