Porous poly(L‐lactic acid)/poly(ethylene glycol) blend films

Poly(L ‐lactic acid) (PLLA: M_w = 19.4 × 10⁴)/poly(ethylene glycol) (PEG: M_w = 400) blend films were formed by use of a solvent‐cast technique. The properties and structures of these blend films were investigated. The Young's modulus of the PLLA decreased from 1220 to 417 MPa with the addition of PEG 5 wt %, but the elongation at break increased from 19 to 126%. The melting point of PLLA linearly decreased with increases in the PEG content (i.e., pure PLLA: 172.5°C, PLLA/PEG = 60/40 wt %: 159.6°C). The PEG 20 wt % blend film had a porous structure. The pore diameter was 3–5 μm. The alkali hydrolysis rate of this blend film was accelerated due to its porous structure. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 965–970, 2004     

Development of new-concept desk top size machine tool

A desktop multiprocess machinery has been designed that has two concepts: miniaturizing of machine tool and multiprocessing with a same machine tool. The prototype of desktop multiprocess machinery is developed in this study. This is tabletop size machine tool that has five changeable machining heads. Outline of main body and machining head are presented.In order to know the basic accuracy of desktop multiprocess machinery, experimental evaluation is carried out. Machining head setting error, stiffness of multiprocess machinery and straightness of X, Y, Z stage is measured. To study the basic performance of desktop multiprocess machinery, a complex machining experiment is carried out with the developed machine tool. The complex machining consists of three steps: electrode machining by milling, hole shaping by EDM, and hole finishing by ECM. These steps are performed in sequence on the same machine tool. The complex machining is successfully carried out. In order to evaluate the desktop multiprocess machinery from environmental point of view, machining energy, volume of machining liquid, and installation space of desktop multiprocess machinery are measured. The measured values are compared with estimated values with conventional machine tools. The machining energy, the volume of machining liquid, and the installation space of desktop multiprocess machinery are smaller than those of conventional machine tool.     

High-power hybrid plasma spraying of large yttria-stabilized zirconia powder

To testify to the advantage of large ceramic powder spraying, numerical simulations and experimental studies on the behavior of large yttria-stabilized zirconia (YSZ) powder in a high-power hybrid plasma spraying process have been carried out. Numeric predictions and experimental results showed that, with the high radio frequency (RF) input power of 100 kW, the most refractory YSZ powder with particle sizes as large as 88 μm could be fully melted and well-flattened splats could be formed. A large degree of flattening (ξ) of 4.7 has been achieved. The improved adhesive strength between the large splat and the substrate was confirmed based on the measurement of the crack density inside of the splats. A thick YSZ coating >300 μm was successfully deposited on a large CoNiCrAlY-coated Inconel substrate (50×50×4 mm in size). The ultradense microstructure without clear boundaries between the splats and the clean and crack-free interface between the top-coat and the bond-coat also indicate the good adhesion. These results showed that highpower hybrid plasma spraying of large ceramic powder is a very promising process for deposition of highquality coatings, especially in the application of thermal barrier coatings (TBCs).     

The effects of amino-acid mutations on specific interactions between urokinase-type plasminogen activator and its receptor: Ab initio molecular orbital calculations

During cancer invasion, the binding of urokinase-type plasminogen activator (uPA) to its receptor (uPAR) on the surface of a cancer cell is considered a trigger for invasion. Here, we present a stable structure of the solvated complex formed between uPA and uPAR (uPA-uPAR) and investigate the specific interactions between uPA and uPAR by ab initio fragment molecular orbital (FMO) calculations. The result indicates that the electrostatic interactions between the charged amino acid residues existing in both uPA and uPAR make a large contribution to the binding between uPA and uPAR. In particular, Lys23, Lys46, Lys98 and Lys61 of uPA are found to have strong attractive interactions with uPAR. To elucidate the effect of these residues on the interactions between uPA and uPAR, we substituted each of them with the uncharged amino acid Leu and investigated the interactions between the mutated uPA and wild-type uPAR. The interaction energies indicate that Lys46 and Lys98, which bind uPA to the rim of the central ligand-binding cavity of uPAR, make greater contributions to the binding between uPA and uPAR than Lys23, which is positioned at the bottom of the ligand-binding cavity of uPAR. The effect of hydrating water molecules located between uPA and uPAR is also investigated to be significant for the specific interactions between uPA and uPAR. These results are expected to be informative for developing new peptide antagonists that block the binding of uPA to uPAR.     

Control of three-link underactuated manipulators using a switching method of fuzzy energy regions

In general, manipulators used for industry and in academic laboratories have actuators to drive each joint. On the other hand, underactuated manipulators handled by our research have some passive or free joints without actuators and brakes. We recently developed a switching method of fuzzy energy regions to control such manipulators. In such a method, it is necessary to design parameters related to energy regions and the gains of some partly stable controllers based on the computed torque method. Here, the switching method is applied for a three-link underactuated manipulator. We optimize such design parameters related to fuzzy energy regions by a genetic algorithm. The effectiveness of the present method is illustrated with some simulations. This work was presented in part at the 12th International Symposium on Artificial Life and Robotics, Oita, Japan, January 25–27, 2007     

Plasma etching of high-k and metal gate materials

Etching characteristics of high-k dielectric materials (HfO₂) and metal electrode materials (Pt, TaN) have been studied in high-density chlorine-containing plasmas at pressures around 10 mTorr. The etching of HfO₂ was performed in BCl₃ without rf biasing, giving an etch rate of about 5 nm/min with a high selectivity of >10 over Si and SiO₂. The etching of Pt and TaN was performed in Ar/O₂ with high rf biasing and in Ar/Cl₂ with low rf biasing, respectively, giving a Pt etch rate of about several tens nm/min and a TaN etch rate of about 200 nm/min with a high selectivity of >8 over HfO₂ and SiO₂. The etched profiles were outwardly tapered for Pt, owing to the redeposition of etch or sputter products on feature sidewalls, while the TaN profiles were almost anisotropic, probably owing to the ion-enhanced etching that occurred.     

Quantum Bit-commitment for small storage based on quantum one-way permutations

We propose a quantum bit-commitment scheme based on quantum one-way permutations with the unconditionally binding and computationally concealing property. Our scheme reduces exponentially the number of bits which the receiver needs to store until, the opening phase compared with the classical counterpart. Keisuke Tanaka, Ph.D.: He is Assistant Professor of Department of Mathematical and Computing Sciences at Tokyo Institute of Technology. He received his B.S. from Yamanashi University in 1992 and his M.S. and Ph.D. from Japan Advanced Institute of Science and Technology in 1994 and 1997, respectively. For each degree, he majored in computer science. Before joining Tokyo Institute of Technology, he was Research Engineer at NTT Information Sharing Platform Laboratories. His research interests are cryptography, quantum computation, circuit complexity, and the design and analysis of algorithms.     

Electrical characterization of high-k gate dielectrics on Ge with HfGeN and GeO2 interlayers

Two kinds of HfSiO_x/interlayers (ILs)/Ge gate stack structures with HfGeN- and GeO₂-ILs were fabricated using electron cyclotron resonance (ECR) plasma sputtering and the subsequent post deposition annealing (PDA). It was found that HfGe was formed by the deposition of Hf metal on Ge and changed to HfGeN by N₂ ECR-plasma irradiation, which was used as IL. Another IL was GeO₂, which was grown by thermal oxidation at 500 °C. For dielectrics with HfGeN-IL, PDA of 550 °C resulted in effective oxide thickness (EOT) of 2.2 nm, hysteresis of 0.1 V, and interface state density (D_it) = 7 × 10¹² cm^− 2 eV^− 1. For dielectrics with GeO₂-IL, PDA of 500 °C resulted in EOT of 2.8 nm, hysteresis of 0.1 V, and D_it = 1 × 10¹² cm^− 2 eV^− 1. The structural change of HfSiO_x/GeO₂/Ge during the PDA was clarified by using X-ray photoelectron spectroscopy, and the gate stack formation for obtaining the good IL was discussed.