Preparation of cellulose graft copolymers having polypeptide side chains and their blood compatibility

Blood compatibility of cellulose graft copolymers with poly(γ-benzyl-L -glutamate) and poly(N⁵-2-hydroxyethyl-L -glutamine) (Cell-g-PBLG and Cell-g-PHEG) was examined in vivo blood tests. For this purpose, Cell-g-PBLG graft copolymers with PBLG contents ranging from 7 to 60 mol % were prepared by polymerizing N-carboxy-γ-benzyl-L-glutamate(γ-BLG NCA) using aminoethyl cellulose (AE-Cell) with degree of substitution of 0.05 as macroinitiator. Graft copolymerization was carried out under a variety of conditions at 20°C in dimethyl-sulfoxide. Monomer conversion higher than 60% were obtained for all the polymerization runs. The solubility tests revealed that all of the AE-Cell and the polypeptides formed were grafted. The Cell-g-PHEG graft copolymers were prepared by treating Cell-g-PBLG graft copolymers with 2-amino-1-ethanol. Characterization of these graft copolymers were carried out by IR spectroscopy, DSC, and water content measurement. Tests for blood compatibility, in vivo, were made by a method of peripheral vein indwelling suture which was developed by one of the authors. The coating of graft copolymers on the polyester suture was made by casting either from formic acid solution of LiCl/dimethylacetamide solutions using water as the regenerating medium, and the polymer-coated sutures were implanted into a jugular and femoral vein of a dog. The results showed that the graft copolymers examined have excellent antithrombogenic properties.     

Performance analysis of dynamic spectrum handoff scheme with variable bandwidth demand of secondary users for cognitive radio networks

Cognitive radio (CR) has attracted considerable attention as a promising technology for solving the current inefficient use of spectrum. In CR networks, available sub-channels are dynamically assigned to secondary users (SUs). However, when a primary user accesses a primary channel consisting of multiple sub-channels, data transmissions of the SUs already using the sub-channels may be terminated. In this paper, we analyze the performance of dynamic spectrum handoff scheme with channel bonding, in which the number of sub-channels used by an SU are variable. We model the multichannel CR network as a multiserver priority queueing system without waiting facility, deriving the blocking probability, the forced termination probability and the throughput for SUs. In terms of the way of forced termination, we consider two policies; one is that SUs using the largest number of sub-channels are forced to terminate their transmissions, and the other is that SUs using the smallest number of sub-channels are chosen for termination. The analysis is also validated by simulation. Numerical examples show that in both forced-termination policies, the throughput of SUs that are forced to terminate their transmissions degrades as the offered load to the system increases.     

Smoke detection using time series property of texture features

We present a method of smoke detection using image sequences from a single camera on open areas under general environmental conditions. We combine several simple image processing techniques to detect smoke with texture analysis. First, moving objects are detected from gray‐scale image sequences. Then, the texture features are extracted. Finally, we determine the existence of smoke based on the time series property of those texture features. In the experiment, the performance is evaluated using real‐scene data. © 2011 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Neural-network-controlled superconducting magnetic energy storage for power system stabilization

It has been clarified that a superconducting magnetic energy storage (SMES) is very effective for power system stabilization. The control methods proposed for power system stabilization by SMES are the pole assignment, the optimal control, and so on, each of which, however, has its drawbacks. This paper is concerned with the power system stabilization by neural network control of the active power of SMES. First, the optimal stabilizing control of the SMES power for the model power system is calculated for various power system operating conditions and fault conditions. Then these optimal controls are used as training data for the neural network. The neural network used is a multilayer type with a feedback from the output layer to the input layer. The trained neural network is examined by untrained operating conditions and faults.     

Polyhydroxyalkanoate synthase from Bacillus sp. INT005 is composed of PhaC and PhaR

A polyhydroxyalkanoate (PHA) biosynthesis gene locus from Bacillus sp. INT005 strain, which had been isolated from a gas field, was cloned and analyzed at the molecular level. We found that a 3.8-kbp DraI-digested fragment of genomic DNA of Bacillus sp. INT005 conferred PHA-producing ability to Escherichia coli, which was PHA-negative. The DNA fragment contained three genes, phaR, -B and -C. The activity of 3-ketoacyl-CoA reductase with NADPH was detected in the lysate from recombinant E. coli carrying the phaB gene. Although PHA synthase activity could be detected in the extract from E. coli carrying phaR, -B and -C genes, no such activity could be detected in that from E. coli carrying only the phaC gene. However, the mixture of the crude extracts of E. coli expressing phaR or phaC revealed very high PHA synthase activity. Furthermore, when His-tagged PhaC was purified by Ni-affinity chromatography from the mixture of crude extracts containing His-tagged PhaC or native PhaR, the eluate contained His-tagged PhaC and native PhaR. On the other hand, PhaR did not bind to the column directly. This purified PhaC with PhaR had 160-fold higher specific activity of PHA synthase than that without PhaR. In addition, the kinetics of the purified PhaC with PhaR revealed a lag phase that preceded the linear phase. It has been known that class III PHA synthase is composed of two different subunits, PhaC and PhaE, and phaC and phaE genes are directly linked in the genomes. Furthermore, the PHA synthase has no lag phase. We hence concluded that the PHA synthase of Bacillus sp. INT005 consists of PhaC and PhaR, and has characteristics different from class III PHA synthase.     

Narrow-beam divergence of the emission from low-threshold GaInAsP/InP double-heterostructure lasers

The angles of beam divergence perpendicular to the junction plane have been studied for low-threshold GaInAsP/InP double-heterostructure lasers with a thin active layer emitting at 1.31 ?m. The narrowest beam divergence obtained was 23° for a laser diode with an active-layer thickness of 0.05 ?m. At an active-layer thickness of 0.13 ?m, the beam divergence was 40° with a threshold current density of 770 A/cm2.     

Enzymatic synthesis of poly(3-hydroxybutyrate-co-4-hydroxybutyrate) with CoA recycling using polyhydroxyalkanoate synthase and acyl-CoA synthetase

We succeeded in developing a novel method for in vitro poly(3-hydroxybutyrate-co-4-hydroxybutyrate) [P(3 HB-co-4 HB)] synthesis with CoA recycling using polyhydroxyalkanoate synthase and an acyl-CoA synthetase. Using this method, the monomer compositions in P(3 HB-co-4 HB)s could be controlled strictly by the ratios of the monomers in the reaction mixtures.     

Prediction of Type IV creep failure of a seam-welded mod. 9Cr-1Mo elbow based on microscopic damage simulation

Utilising the random-fracture-resistance model of grain boundaries, micro-macro combined creep damage simulation was applied to the prediction of the distribution of small defects in the FGHAZ (fine-grained heat-affected zone) of longitudinal welds in an actual-size elbow of modified 9Cr-1Mo (9Cr-1MoVNb) steel subject to internal pressure at 923 K. Based on the simulation results, a prediction scheme for the final rupture life of welds was considered using the damage mechanics concept together with effective stress. The applicability of nonlinear fracture mechanics was also discussed, assuming the initial crack length determined from the microscopic simulation results. The results thus obtained are summarized as follows: As the simulation results showed, the peaks of small defect density in the subsurface could be predicted, corresponding well with the observed results. Final failure life prediction based on the damage mechanics concept was found to be applicable, by considering both the final failure surface connecting the weakest grain boundaries and the effective stress against this surface. The fracture mechanics approach was also found applicable when assuming the initial crack length from the high peaks of the simulated small defects in the last stage of creep life.     

Dissolution effect and cytotoxicity of diamond-like carbon coatings on orthodontic archwires

Nickel–titanium (NiTi) has been used for implants in orthodontics due to the unique properties such as shape memory effect and superelasticity. However, NiTi alloys are eroded in the oral cavity because they are immersed by saliva with enzymolysis. Their reactions lead corrosion and nickel release into the body. The higher concentrations of Ni release may generate harmful reactions. Ni release causes allergenic, toxic and carcinogenic reactions. It is well known that diamond-like carbon (DLC) films have excellent properties, such as extreme hardness, low friction coefficients, high wear resistance. In addition, DLC film has many other superior properties as a protective coating for biomedical applications such as biocompatibility and chemical inertness. Therefore, DLC film has received enormous attention as a biocompatible coating. In this study, DLC film coated NiTi orthodontic archwires to protect Ni release into the oral cavity. Each wire was immersed in physiological saline at the temperature 37 °C for 6 months. The release concentration of Ni ions was detected using microwave induced plasma mass spectrometry (MIP-MS) with the resolution of ppb level. The toxic effect of Ni release was studied the cell growth using squamous carcinoma cells. These cells were seeded in 24 well culture plates and materials were immersed in each well directly. The concentration of Ni ions in the solutions had been reduced one-sixth by DLC films when compared with non-coated wire. This study indicated that DLC films have the protective effect of the diffusion and the non-cytotoxicity in corrosive environment.