Processing, Mechanical Properties, and Oxidation Behavior of Silicon Oxynitride Ceramics

Silicon oxynitride ceramics were prepared by hot-pressing an equimolar Si₃N₄+ SiO₂ mixture with 3 mol% CeO₂. The Ce₂O₃/SiO₂ ratio of intergranular phase (liquid phase) increased as the formation of Si₂N₂O proceeded. The intergranular liquid remained as a glass on cooling until the Ce₂O₃/SiO₂ ratio exceeded a certain value, at which point the liquid crystallized. There were great differences in thermal and mechanical properties and oxideation behavior between the specimen containing intergranular glassy phase and the one containing intergranular crystalline phase (Ce₅(SiO₄)₃N–Ce_4.67(SiO₄)₃O). The specimen containing the intergranular glassy phase showed excellent hightemperature strength and oxidation resistance.     

Methanation of CO2 with H2-reduced magnetite

The methanation reaction of CO₂ was studied with H₂-reduced magnetite. A high conversion ratio of about 0.9 (in 30 min of the reaction time) with a selectivity of nearly 100% was obtained at 300°C and at 0.1 MPa for H₂-reduced magnetite which had been prepared by passing H₂ gas for 1–5 h at 300°C. From the results of X-ray diffractometry and Mössbauer spectroscopy, and from chemical analysis of the deposited carbon, H₂-reduced magnetite is considered to decompose adsorbed CO₂ into carbon, and to incorporate the oxygen of the CO₂ into the spinel-type structure of the magnetite, associated with oxidation of the Fe²⁺ ion into Fe³⁺ ion in the magnetite. The high conversion ratio in the methanation reaction is considered to come from a higher reactivity of the elementary carbon deposited on the surface of the H₂-reduced magnetite.     

A study on selective reduction of NOx by propane on Co-Beta

Selective catalytic reduction of NOx by propane was investigated on Co-Beta to clarify the loaded states of cobalt and their role in catalytic activity. At low ion exchange levels less than 100%, loaded cobalt is highly dispersed, which has a high selectivity for NOx reduction. At ion exchange levels much higher than 100%, Co₃O₄ appears as identified by Raman spectroscopy, and it contributes to propane oxidation by oxygen and lowers the selectivity especially at high temperatures. This revised version was published online in July 2006 with corrections to the Cover Date.     

Predisposing factors for severe mitral regurgitation in idiopathic mitral valve prolapse

To elucidate predisposing factors for severe mitral regurgitation (MR) in idiopathic mitral valve prolapse (MVP), 124 MVP patients were classified into the following categories: 55 with isolated clicks (click group), 35 with a late-systolic murmur (late-SM group), and 34 with a holosystolic murmur (holo-SM group). Their clinical and echocardiographic findings were compared with those of 26 patients with spontaneous chordal rupture (rupture group). In 22 patients in the click group, 24 in the late-SM group, and 22 in the holo-SM group, follow-up studies were performed for a mean of 4.5 years (range 1 to 13.5). The mean age was youngest in the click group and oldest in the rupture group. The click and late-SM groups showed a female predominance, but the holo-SM and rupture groups showed a male predominance. There was no difference in the incidence of systemic hypertension among the 4 groups. Most patients in the click and late-SM groups had anterior leaflet prolapse. In the holo-SM and rupture groups, however, the incidence of posterior leaflet involvement was significantly increased. The incidence of thickened mitral valve increased in order of the click (8%), late-SM (21%), holo-SM (38%), and rupture (50%) groups. Six patients in the holo-SM group developed chordal rupture with severe MR during the follow-up period. In the click and late-SM groups, however, there were no complications and no development into a holo-SM. Thus, aging, male sex, posterior leaflet prolapse, thickened mitral valve, and holo-SM were found to be important predisposing factors for severe MR in idiopathic MVP.     

Morphological changes in traumatized skeletal muscle: the appearance of 'opaque fibers' of cervical muscles as evidence of compression of the neck

Cervical muscles of 15 cases of compression of the neck and the other traumatized skeletal muscles from 54 autopsy cases were examined histologically and immunohistochemically. Round and thick fibers, that is, opaque fibers were observed in the muscles beneath the compression marks on the neck, whereas in areas where no force had been applied, such fibers did not exist. Furthermore, opaque changes appeared around cavities, which formed within severely compressed injured muscle tissue. The pattern of appearance of opaque fibers in the cases of compression of the neck were mainly divided into two types, 'diffuse' pattern and 'focal' pattern. In both blunt and sharp force injuries, the production of opaque fibers were common in the area directly where damage had been inflicted. In stab wounds especially, the appearance of opaque fibers and wavelike fibers, which fanned out and showed a different color from the other areas, was limited to the marginal zone. These results suggest that there is a close relationship between opaque changes and force. Opaque fibers are probably produced by damage to muscles due to extremely applied force. The high incidence of opaque fibers beneath compression marks on the neck should be regarded as a useful indication of strangulation and/or hanging. Furthermore, the distribution and direction of force to the neck might be presumed by the pattern of opaque fibers in cervical muscles, to a certain extent.     

On-chip transformation of bacteria

On-chip transformation of Escherichia coli cells was accomplished for the first time using a microbial array chip. The continuous E. coli transformation procedures were performed on a chip in which the microcompartment was composed of PDMS microfluidic channels and a silicon substrate predeposited with different plasmid DNAs. The PDMS microfluidic device enabled the parallel transformation of E. coli cells with various plasmid DNAs by separating each transformation area. The phenotypic differences reflecting different plasmid DNAs were identified by various approaches such as colorimetry, fluorometry, and electrochemical methods. This microbial array chip could become a versatile tool for many cell biological applications.     

Five years operating experience of large scale distillation test plant made of carbon steel

The distillation test plant operated since April 14, 1972 during 94.2% of the work day has the capacity to treat 1,000 cu. meter/day of sea water, to produce 850t of fresh water of excellent quality, leaving 150t of concentrated brine containing 20% solid matter. Raw sea water was pretreated to prevent scale formation and corrosion of materials in distillation. Patents have been granted in Japan, USA, United Kingdom, West Germany, France, Italy, etc. (1).This method enables use of a base metal such as common steel for construction with the following advantages:Capital investment is cheaper.No galvanic corrosion arises.Mechanical structure is rigid.Contamination of poisonous heavy metals is avoidable.Upper limit of temperature is higher.Amount of raw sea water is smaller.Amount of exhaust brine is smaller.     

Determination of the coefficient of friction in forging of porous metals from ring compression

An analysis of ring compression of porous metals was made on the basis of the plasticity theory for porous metals previously proposed by the authors. The change in geometry of rings with various porosities was obtained for various coefficients of friction. Experiments on ring compression were carried out using sintered copper powder metals. The coefficient of friction was determined for various lubricants and a proper lubricant for forging of porous metals was found.