Effects of cysteinyl-leukotriene receptor antagonist, thromboxane A2 receptor antagonist, and thromboxane A2 synthetase inhibitor on antigen-induced bronchoconstriction in patients with asthma

BACKGROUND: Leukotriene (LT) and thromboxane A2 (TXA2) receptor antagonists have been used in the treatment of asthma. OBJECTIVES: We examined the effects of an LT receptor antagonist, TXA2 receptor antagonist, and TXA2 synthetase inhibitor on bronchoprovocation test (BPT) in patients with mild-to-moderate atopic asthma. METHODS: BPT was performed four times in each of six asthmatics. Development of the immediate asthmatic reaction (IAR) and late asthmatic reaction (LAR) was confirmed on the first BPT (BPT1). After a 7-day washout period, an LT receptor antagonist (pranlukast, 450 mg/d), TXA2 receptor antagonist (seratrodast, 80 mg/d), or TXA2 synthetase inhibitor (ozagrel, 800 mg/d) was administered orally over 7 days at random using a cross-over method (BPT2-4). Blood levels of LTB4, LTC4, LTD4, 11-dehydrothromboxane B2, eosinophil cationic protein, and histamine were measured at reaction phases of pre-BPT, IAR, and LAR. RESULTS: Administration of pranlukast suppressed IAR by 80.5% (p < 0.0001) and LAR by 54.6% (p = 0.0391). Ozagrel significantly suppressed IAR by 39.5% (p = 0.0413), but the fall in FEV1 was >20% (21.56+/-4.173%). Seratrodast did not suppress IAR or LAR. Blood levels of chemical mediators did not correlate with the suppressive effects of the tested drugs. CONCLUSIONS: The LT receptor antagonist was considered to be the most effective. LT might play a more important role in the pathogenesis of asthma than TXA2. Our data showed that measurement of blood levels of chemical mediators is not useful in identifying the pathogenic mechanisms of asthma.     

High-Strength and High-Fracture-Toughness Ceramics in the Al2O3/LaAl11O18 Systems

Control of microstructure in the Al₂O₃/LaAl₁₁O₁₈ system was performed. Elongated alumina grains were formed by doping with small addition of silica, and 20 vol% lanthana- luminate was formed in situ by the reaction of LaAlO₃- A1₂O₃ in an alumina matrix. Strengths of over 600 MPa and a high fracture toughness (6 MPa.m^1/2) were achieved in the material with both elongated A1₂O₃ grains and LaAl₁₁O₁₈ platelets. Generally antagonistic properties such as strength and fracture toughness have been made compatible in the same ceramic system.     

Highly Transparent Lu-α-SiAlON

Novel Lu-α-SiAlON ceramics were produced by hot pressing mixtures of Si₃N₄, Lu₂O₃, AlN, and Al₂O₃ at 1950°C for 2 h in a nitrogen atmosphere. The resultant SiAlON was fully dense and possessed a uniform, equiaxed microstructure with a grain size of ∼1 μm, which resulted in a high hardness of >19 GPa. In addition to high hardness, the sample showed very high optical transparency in the visible light region, with >70% transmission at higher wavelengths. This high transparency was attributed to the uniform, dense microstructure and lack of residual grain-boundary phase.     

Formation and Properties of Ln-Si-O-N Glasses (Ln = Lanthanides or Y)

Homogeneous Y-Si-O-N glasses containing 15 or 20 eq% nitrogen (N) were prepared from compositions with Y/Si ratios in the vicinity of that of the lowest eutectic point on the Y₂O₃–SiO₂ phase diagram. The liquidus on the phase diagram shifted toward lower temperatures by incorporation of N. The density, the elastic moduli, and the glass transition temperature of the Y-Si-O-N glasses increased with incorporation of N. This is due to the closer packing of atoms in the glasses by the substitution of N, which is in three-fold coordination with Si, for O which is in two-fold coordination, and the stronger covalent nature of the Si–N bond compared with the Si–O bond. The coefficient of thermal expansion of the Y-Si-O-N glasses increased with increasing Y content, because the discontinuity of the glass network developed with increasing nonbridging anions by the introduction of Y. In contrast, the glass transition temperature and the elastic moduli increased with Y content due to the high coordination of Y for O, and the relatively high cationic field strength of Y. Furthermore, the effect of cationic field strength on properties of Ln-Si-O-N glasses (Ln = lanthanides or Y) is discussed.     

Processing Strategy for Producing Highly Anisotropic Silicon Nitride

Silicon nitride with a preferred orientation of large elongated grains was obtained by tape casting of raw powder slurry seeded with rodlike β-Si₃N₄ particles, followed by a gas pressure sintering under 1 MPa nitrogen pressure. The large elongated grains developed from seeds lay in planes parallel to the casting direction in a two-dimensional distribution. Increased fracture toughness (11.1 MPa·m^1/2) and bending strength (1100 MPa) were achieved in the direction perpendicular to the grains alignment compared to specimens with a random distribution of elongated grains. Morover, the specimens exhibited a high Weibull modulus of 46 due to the uniform distribution of large grains.     

Silicon neuron: digital hardware implementation of the quartic model

This paper presents an FPGA implementation of the quartic neuron model. This approach uses digital computation to emulate individual neuron behavior. We implemented the neuron model using fixed-point arithmetic operation. The neuron model’s computations are performed in arithmetic pipelines. It was designed in VHDL language and simulated prior to mapping in the FPGA. We show that the proposed FPGA implementation of the quartic neuron model can emulate the electrophysiological activities in various types of cortical neurons and is capable of producing a variety of different behaviors, with diversity similar to that of neuronal cells. The neuron family of this digital neuron can be modified by appropriately adjusting the neuron model’s parameters.     

Mechanical Properties of Textured Alumina Made by High-Temperature Deformation

The mechanical properties of a textured alumina made by high-temperature deformation of normal-purity sintered alumina have been investigated. The textured alumina shows very high bending strength and extremely high fracture toughness. Fracture toughness of more than 10 MPa·m^1/2 was measured by the single-edge precracked beam method, and even using the single-edge V-notched beam method, toughness of over 8 MPa·m^1/2 was obtained. This high fracture toughness was attributed to a large number of aligned small platelike grains of the textured structure enhancing the grain bridging effect.     

Quantitative imaging of Young's modulus of solids: a contact-mechanics study

We developed equipment and methods for measuring quantitatively the local Young's modulus of solids. It consists of an electrodeless langasite oscillator and line antennas, and oscillator vibrations are generated and detected contactlessly. A constant biasing force results from oscillator mass and is independent of surface roughness. The effect of material anisotropy on the measured stiffness is theoretically discussed for studying the limitation of the quantitative measurement. The microscopy has been applied to polycrystalline copper, and the measured modulus is compared to calculations based on electron-backscatter-diffraction measurements. Also, we applied it to a duplex stainless steel and an embedded silicon-carbide fiber. The results reveal textured regions, defects with high sensitivity, and even stiffness distribution in a single grain.     

Current-induced domain nucleation in ferromagnet

A key mechanism of the current-induced magnetization dynamics is the spin torque from a spin polarized current (spin current), which couples to spatial gradient of magnetization. Recently, it was pointed out that a large spin current applied to a uniform ferromagnet leads to a spin-wave instability. In this paper, we show that such instability is absent in a state containing a domain wall. This may indicate that nucleation of magnetic domains occurs above a certain critical spin current. This scenario is supported by an explicit energy comparison between the uniformly magnetized state and the domain-wall state under spin current.     

Effects of phosphorus content on generation and growth of cracks in nickel–phosphorus platings owing to thermal cycling

We observed crack generation and structural changes in electroless nickel–phosphorus (Ni–P) plating layers formed on copper-metalized silicon nitride substrates both during thermal cycling from ? 40 to 250 °C and during storage (not cycling) at 250 °C in order to investigate the effect of the phosphorus contents on crack generation and growth in the Ni–P platings. The used platings contained phosphorus at three different contents: 2.1 wt% [Ni–P(low)], 6.5 wt% [Ni–P(med)], and 10.9 wt% [Ni–P(high)]. The generation time and the amount of cracks were strongly dependent on their phosphorus contents. More cracks appeared after thermal cycling than after storage at 250 °C. In Ni–P(low), cracks were generated after 200 thermal cycles, whereas no cracks were observed even after 250 h of storage at 250 °C. In Ni–P(med) and Ni–P(high), both during thermal cycling and storage at 250 °C, cracks formed during or after crystallization of the amorphous layers. These results suggest that the primary factors affecting the generation of cracks in electroless Ni–P platings are crystallization of the Ni–P platings and repeated changes in thermal stress.