Performance of calcium deficient hydroxyapatite–polyglycolic acid composites: an in vitro study

The strategic incorporation of bioresorbable polymeric additives to calcium-deficient hydroxyapatite cement may provide short-term structural reinforcement and modify the modulus to closer match bone. The longer-term resorption properties may also be improved, creating pathways for bone in-growth. The aim of this study was to investigate the resorption process of a calcium phosphate cement system containing either in polyglycolic acid tri-methylene carbonate particles or polyglycolic acid fibres. This was achieved by in vitro aging in physiological conditions (phosphate buffered solution at 37°C) over 12 weeks. The unreinforced CPC exhibited an increase in compressive strength at 12 weeks, however catastrophic failure was observed above a critical loading. The fracture behaviour of cement was improved by the incorporation of PGA fibres; the cement retained its cohesive structure after critical loading. Gravimetric analysis and scanning electron microscopy showed a large proportion of the fibres had resorbed after 12 weeks allowing for the increased cement porosity, which could facilitate cell infiltration and faster integration of natural bone. Incorporating the particulate additives in the cement did not provide any mechanism for mechanical property augmentation or did not demonstrate any appreciable level of resorption after 12 weeks.     

A rolled sheet of collagen gel with cultured Schwann cells: Model of nerve conduit to enhance neurite growth

We prepared a rolled sheet of collagen gel with cultured mouse Schwann cells (SCs) as a nerve conduit (a medical device for neurosurgeons to repair an injured peripheral nerve). PC12 cells and dorsal root ganglion (DRG) cells were used as neuronal cells for evaluating the neurite growth-promoting activity of the device. As a control, we compared the rolled device with a rod device. Those neuronal cells inoculated at the terminal part of the rolled device migrated into the central part along the inter-layer space of the collagen gel layer, and then differentiated into neurons, extending many neurites for 3–12 days in culture. Significantly, this migration of neuronal cells into the device and their subsequent neurite growth was not observed in the absence of the SCs. We conclude that our rolled sheet of collagen gel with SCs was well designed and very effective to promote neurite growth, and is a promising candidate for the nerve conduit.     

Corrosion of Al-Sn-Bi alloys in alcohol at high temperatures. Part I: Effects of the metallurgical structure of the alloys and the metal salt additions to alcohol

Corrosion of free machining Al alloys that contain Sn and Bi was investigated at 391-415 K in 2-(2-(2-methoxyethoxy)ethoxy)ethanol (MEEE) and 2-(2-(2-butoxyethoxy)ethoxy)ethanol (BEEE) with/without SnCl₂, Sn(OC₂H₅)₄, FeCl₃, and CuCl₂. The Al-Sn-Bi alloy displayed severe pitting corrosion in MEEE similar to the Al-Sn alloy in BEEE at 415 K, and Sn and Sn/Bi were enriched on the surface of pits. Immersion tests of pure Al in MEEE containing Sn/Cu-salts at 415 K also showed severe corrosion and the deposition of metallic Sn and Cu on the surface. The corrosion mechanisms are discussed in terms of the electro-catalytic activity of the Sn enriched on the surface.     

Development of long range optical fiber sensors for compositesubmarine power cable maintenance

Long range optical fiber sensors for power cable maintenance have been incorporated into a newly developed 500 kV DC submarine power cable. Optical fibers are used for a distributed temperature sensor and a mechanical damage sensor. The distributed temperature sensor provides data on temperature at distances up to 30 km, and the mechanical damage sensor locates external damage points on the submarine cable. After each characteristic was investigated, optical fiber sensors were incorporated on the submarine power cable. This composite cable was evaluated by various mechanical tests. The results were satisfactory and showed the composite cable to be of practical use. This new approach of incorporating optical fiber sensors in the cable structure brings a new sophistication and reliability to cable maintenance     

Synergistic effects in the oxidation of methane on strontium and lead hydroxyapatites

The oxidation of methane has been investigated on lead hydroxyapatite (PbHAp), strontium hydroxyapatite (SrHAp) and their binary mixtures at 873 K. PbHAp showed no activity for the oxidation of methane, while SrHAp produced carbon monoxide selectively at 2–4% conversion. On binary mixtures of the hydroxyapatites the conversion of methane and the selectivity to C₂ compounds reached values higher than those of the separate constituents of the mixture. With tetrachloromethane in the feed stream a similar synergistic effect was observed with conversions of methane and selectivities to CH₃Cl higher on the binary mixtures than those on either SrHAp or PbHAp. The strontium-containing hydroxyapatite appears to play a crucial role in the activation of methane, while the presence of the lead-containing analogue is apparently required for the minimization of undesirable processes involving methyl radicals. This revised version was published online in July 2006 with corrections to the Cover Date.     

Jijo-2: an office robot that communicates and learns

Describes how the authors have combined speech recognition, dialogue management, and statistical learning procedures to develop Jijo-2; an office robot that can communicate with humans and learn about its environment.     

Gene transfer of human prostacyclin synthase prevents neointimal formation after carotid balloon injury in rats

BACKGROUND AND PURPOSE: A disordered proliferative process in the vascular wall is thought to underlie the pathogenesis of restenosis after percutaneous transluminal angioplasty and carotid endarterectomy. A growth inhibitory property of overexpressed prostacyclin (PGI2) synthase (PGIS) was recently implicated in the pathological proliferation of vascular smooth muscle cells (VSMC) in vitro. Here, we investigated the effects of increased PGI2 synthesis on the pathological proliferation of VSMCs. METHODS: The cDNA encoding human PGIS was transfected into endothelium-denuded rat carotid arteries after arterial balloon injury with the use of hemagglutinating virus Japan (HVJ). HVJ liposome vector complex without PGIS cDNA was used for vehicle control. The level of 6-keto PGF1alpha, a stable hydrolyzed metabolite of PGI2, the histological distribution of the immunoreactivity for human PGIS and the ratio of neointimal/medial area were analyzed. RESULTS: In the analyses of 6-keto PGF1alpha, the level in the carotid arteries was significantly elevated 3 days after PGIS expression-vector transfection compared with that in the arteries after vehicle transfection. Seven days after human PGIS expression-vector transfection, the PGIS cDNA-transfected neointimal cells were strongly positive for human PGIS immunoreactivity in 81% sections examined. Fourteen days after the injury, the ratio of neointimal/medial area was 1.2+/-0.4 in the PGIS expression-vector transfected group, which was significantly smaller than that of the vehicle control group, 1.7+/-0.5; P<0.01. CONCLUSIONS: It was thus demonstrated that the gene transfer of human PGIS expression-vector into rat carotid arteries resulted in the increased production of human PGI2 in the vascular wall, the expression of human PGIS in the developing neointima and significantly inhibited the neointimal formation generated after balloon injury.     

Characteristics of SiH4/H2 VHF plasma produced by short gap discharge

A SiH₄/H₂ VHF plasma was produced with the multi rod electrode and the fundamental plasma parameters were examined as a function of pressure and power, where the frequency of the power source was 60 MHz. It was found that the ion saturation current takes a peak at a certain power as well as pressure. These results were discussed from the point of view of electron trapping effect in VHF electric fields. In addition, anomalous reduction of the sheath potential was observed.     

Coupled influence of non-ideal diffusion and multilayer asymmetric porous supports on Sieverts law pressure exponent for hydrogen permeation in composite Pd-based membranes

The behaviour of the pressure exponent in the Sieverts-type empirical law is evaluated for hydrogen permeation through Pd-based membranes under the influence of non-ideal internal diffusion and transport in an asymmetric multilayer porous support. The results show that the non-ideal diffusion causes the pressure exponent to be non-monotone within the temperature range investigated (300–500 °C), showing a minimum point indicating the passage from slower internal diffusion to slower transport in support. Additionally, a detailed analysis shows that the maximum transmembrane pressure difference (in terms of maximum feed pressure with constant permeate pressure) is the only operating parameter affecting the uncertainty degree by which the pressure exponent is evaluated. This analysis also shows that the Sieverts-type empirical law can be fully used in the presence of supports. This suggests that an overall transport mechanism resulting from a combination in series/parallel of different elementary mechanisms obeying this law can be also described by the same type of law with a different value of pressure exponent and permeance.