Sintering and Properties of Monazite-Type CePO4

Monazite-type CePO₄ powder (average grain size 0.3 μm) was dry-pressed to disks or bars. The green compacts began to sinter above 950°C. Relative density ≧ 99% and apparent porosity <1% were achieved when the specimens were sintered at 1500°C for 1 h in air. The linear thermal expansion coefficient and thermal conductivity of the CePO₄ ceramics were 9 × 10⁻⁶/°C to 11 × 10⁻⁶/°C (200° to 1300°C) and 1.81 W/(m · K) (500°C), respectively. Bending strength of the ceramics (average grain size 4 μm) was 174 ± 28 MPa (room temperature). The CePO₄ ceramics were cracked or decomposed by acidic or alkaline aqueous solutions at high temperatures.     

Cation-Exchange Characteristics of Sintered Hydroxyapatite in the Strongly Acidic Region

The ion-exchange behavior of hydroxyapatite (Ca₁₀(PO₄)₆-OH)₂) (HAp), fired at high temperatures, has been investigated in the strongly acidic region (pH 2 and 3). According to the present study, HAp fired above 1000°C can exchange ions from Ca²⁺ to Pb²⁺, even at pH 2, without dissolution. The molar ratios of Pb²⁺/Ca²⁺ after ion exchange are approximately unity in all cases. Ion exchange occurs in a thin layer near the surface of HAp particles fired at 1300°C. After ion exchange, Pb-Cl-apatite crystals are created in the strongly acidic region (pH 2).     

Design, Synthesis, and Catalysis of Bio-inspired Immobilized Metallocomplex Catalyst

Novel immobilized metallocomplex catalyst based on bio-inspired concept has been developed. The allyl functional group in the anionic chelating ligand reacts with thiols to give the linker for immobilization. The immobilization of the chelating ligand onto amorphous silica supports results in the isolated metal-binding sites giving the coordinatively unsaturated metal center. The biomimetic iron complex-immobilized silica exhibits the catalysis for olefin epoxidation with aqueous H₂O₂ at ambient temperature.     

Methyl 3‐Hydroxymyristate,a Diffusible Signal Mediating phc Quorum Sensing in Ralstonia solanacearum

Ralstonia solanacearum, a plant pathogenic bacterium causing “bacterial wilt” on crops, uses a quorum sensing (QS) system consisting of phc regulatory elements to control its virulence. Methyl 3‐hydroxypalmitate (3‐OH PAME) was previously identified as the QS signal in strain AW1. However, 3‐OH PAME has not been reportedly detected from any other strains, and this suggests that they produce another unknown QS signal. Here we identify (R)‐methyl 3‐hydroxymyristate [(R)‐3‐OH MAME] as a new QS signal that regulates the production of virulence factors and secondary metabolites. (R)‐3‐OH MAME was synthesized by the methyltransferase PhcB and sensed by the histidine kinase PhcS. The phylogenetic trees of these proteins from R. solanacearum strains were divided into two groups, according to their QS signal types—(R)‐3‐OH MAME or (R)‐3‐OH PAME. These results demonstrate that (R)‐3‐OH MAME is another crucial QS signal and highlight the unique evolution of QS systems in R. solanacearum.     

Electrical and elastic properties of conductor-polymer composites

Several series of conductor-polymer composites were prepared from metal, graphite and conducting ceramics as filler materials, and epoxy, silicone rubber, polyethylene and polypropylene as polymer matrix. Their percolation curves, pressure dependence of resistivity, and Young's modulus were examined for applications such as a pressure sensor.     

Dereverberation and Denoising Using Multichannel Linear Prediction

Reverberation in a room severely degrades the characteristics and auditory quality of speech captured by distant microphones, thus posing a severe problem for many speech applications. Several dereverberation techniques have been proposed with a view to solving this problem. There are, however, few reports of dereverberation methods working under noisy conditions. In this paper, we propose an extension of a dereverberation algorithm based on multichannel linear prediction that achieves both the dereverberation and noise reduction of speech in an acoustic environment with a colored noise source. The method consists of two steps. First, the speech residual is estimated from the observed signals by employing multichannel linear prediction. When we use a microphone array, and assume, roughly speaking, that one of the microphones is closer to the speaker than the noise source, the speech residual is unaffected by the room reverberation or the noise. However, the residual is degraded because linear prediction removes an average of the speech characteristics. In a second step, the average of the speech characteristics is estimated and used to recover the speech. Simulations were conducted for a reverberation time of 0.5 s and an input signal-to-noise ratio of 0 dB. With the proposed method, the reverberation was suppressed by more than 20 dB and the noise level reduced to -18 dB.     

Natural outcome of idiopathic macular hole

To ascertain the natural outcome of idiopathic macular holes, we studied 186 eyes with the disorder: stages 1 (48 eyes), 2 (30 eyes), 3 (71 eyes), and 4 (37 eyes), which were followed for over twelve months. In 11 (23%) eyes with stage 1 lesions full-thickness macular hole developed during the follow-up period, and in 12 (25%) eyes visual acuity decreased two or more Snellen lines. Twenty-five (83%) and 21 (70%) eyes with stage 2 lesions, 39 (55%) and 22 (31%) eyes with stage 3 lesions, and 7 (19%) and 5 (14%) eyes with stage 4 lesions had enlarged macular holes and decreased visual acuity during the follow-up, respectively. The present results suggest that different stages of macular holes have different natural outcomes and the treatment should be based on their stages.