Multichannel fiber ferrule for a stable laser-diode array module

We developed a multichannel fiber ferrule for a stable laser-diode array module. To apply YAG laser welding to parallel butt couple between the laser-diode and the single-mode fiber arrays, hermetically sealed and precisely aligned equi-interval fibers are required. We describe a V-grooved ceramic ferrule for embedding fibers. Fibers are fixed by soldering, using a flat ceramic lid and aligned with a 250 μm pitch. Our ferrule allowed a metallic, stem mounting laser-diode, to be fixed by YAG laser welding. All 30 samples tested have a leak rate of less than 1×10^-10 atm·cc/s. Optical coupling of fabricated modules was 9.7±0.2 dB and coupling loss change from 25°C to 115°C was within 0.5 dB     

Temperature Dependence of the Raman Spectrum in Lithium Oxide Single Crystal

Temperature dependence of the Raman spectrum of lithium oxide single crystal has been measured over a temperature range of 80 to 1073 K. The frequency shift and the line width of the Raman spectrum in lithium oxide were about 531 and 4.5 cm^-1 at 80 K, respectively. At 1073 K, the frequency shift and the line width attained the values of 464 and 112 cm^-1, respectively. The strong temperature dependence of the frequency shift and line width was compared with data from some crystals with a fluorite structure.     

Effect of oxygen on the wettability of sapphire by liquid palladium

The surface tension of liquid palladium and the contact angle between liquid palladium and sapphire have been measured at 1833 K as a function of oxygen pressure by the sessile drop method. Oxygen acted as a surface-active element on the surface of liquid palladium and at the interface between liquid palladium and sapphire, resulting in the decrease of the surface tension and the contact angle. The work of adhesion calculated from their values increased with increasing oxygen pressure, and had a constant value above 400 Pa. The maximum excess concentration of oxygen was estimated to be 7.3×10^–6 mol m^–2 for the surface and 6.9×10^–6 mol m^–2 for the interface.     

An application of rapid freezing,freeze substitution–fixation for scanning electron microscopy

A combined technique of the rapid freezing, freeze substitution–fixation method and the osmium–DMSO-osmium method was devised. By this combined method we clearly observed the architecture of intracellular components in three dimensions. Morphological characteristics were generally similar to those of tissue prepared by the osmium–DMSO-osmium method but different in some respects. Mucigen droplets in intestinal goblet cells, for example, appeared as separated spheres, while in specimens prepared by chemical fixation they were observed as a mass of fused droplets. In the Golgi complex, all cisternae were extremely flat, although they usually dilated on the cis side after chemical fixation. Particles on the mitochondrial tubules of liver cells were well distinguished. They were mushroom shaped, as are those observed by negative staining. The combined method, that is, the rapid freezing, osmium–DMSO-osmium method, is thought to be effective for studying the true structure of intracellular components by scanning electron microscopy.     

Stochastic Leadtimes in Two-Level Assembly Systems

Shortages of assembly parts often arise from late arrivals of one or more batches of components. We address the problem of determining planned leadtimes in two-level assembly systems with stochastic leadtimes, with the objective of minimizing the sum of inventory holding costs and tardiness costs. An algorithm is developed which exploits properties of the objective function to find optimal solutions. Computational results indicate that optimal solutions often have negative safety times for at least one of the components, as well as substantial safety times for the assembly stage.     

Flexural properties of moldings of rigid polyurethane made by reaction injection molding

Flexural properties of moldings made by Reaction Injection Molding (RIM), which are structural foams consisting of high density skin and low density core, were investigated by three-point bending tests. Two failure modes were observed in bending tests of the moldings made by RIM, and they are classified as follows according to the density ratio of skin layer to core layer: the opposite side of the skin layer to which load was subjected failed by tensile stress: and the same side of the skin layer to which load was subjected failed by compressive stress, causing wrinkling or buckling. Then the conventional composite beam theory was applied to the former failure mode and Hoff s buckling theory to the latter, and equations were derived to predict the flexural properties of the structural foams, which involved buckling from the flexural properties of solid construction. In addition, it has been shown that there exists a density distribution that maximizes the flexural strength of the moldings made by RIM with a given overall density. The results obtained here should be useful to the optimum structural design of moldings made by RIM.     

Protein modelling using a chimera reference protein derived from exons

Bovine pancreatic /S-trypsin (PDB ID-code: 1TPO) which is registeredin the Brookhaven Protein Data Bank (PDB) consists of four exons.The results of homology searches for each exon in the PDB showedthat homologous proteins were tonin (PDB ID-code: 1TON), ratmast cell protease (PDB ID-code: 3RP2_A), kaffikrein A (PDBID-code: 2PKA_B) and kallikrein A (2PKA_B) respectively. Thus,for the three-dimensional structure prediction of 1TPO, a chimeraprotein was constructed from the three proteins mentioned aboveand the 3-D structure prediction was performed using this chimerareference protein. The modelled structure of 1TPO was energeticallyoptimized by molecular mechanics and molecular dynamics simulationand was compared with its X-ray crystal structure registeredin the PDB. The root mean square deviations (r.m.s.d.) of mainchain atoms and the neighbouring active site (5 sphere fromHis57, AsplO2 and Serl95) between the modelled structure andthe X-ray structure were 1.66 and 0.94 respectively. Porcinepancreatic elastase (PDB ID-code: 3EST) which is registeredin the PDB was used as the reference protein and the modelledstructure from 3EST was also compared with the X-ray data. Ther.m.s.d. of main chain atoms and that of the active site were2.14 and 1.18 respectively. These results dearly support thepropriety of this method using the chimera reference protein.     

Stability of tetragonal ZrO2 phase in Al2O3 prepared from Zr-Al organometallic compounds

Zr-Al organometallic compounds have been spray-dried and heated at temperatures 600 to 1400°C to prepare ZrO₂-Al₂O₃ composite powders. The powders consist of balloon-like particles 0.5 to 2 m in diameter with homogeneously dispersed tetragonal ZrO₂ grains 0.1 to 0.2 m in diameter. The tetragonal fraction of ZrO₂ in the composite powders is higher than that in the powders prepared from sols of Zr(OBuⁿ)₄ and Al[OCH(CH₃)₂]₃. The fraction is affected by the organofunctional group in the Zr-Al compounds.Zr(OBuⁿ)₄ = Zr(OC₄Hgⁿ)₄; Al[OCH(CH₃)₂]₃ = Al(OPrⁱ)₃.     

Microstructure and superconducting properties of rapidly-quenched copper-based alloys containing immiscible lead and bismuth elements

Copper-based superconducting alloys including finely dispersed f c c lead or h c p (Pb- Bi) particles in f c c copper matrix have been obtained by rapid quenching (Cu-M)_100-x Pb_x and (Cu-M)_100-x (Pb_0.6Bi_{0.4 x} (M = aluminium, silicon or tin;x < 10 at%) alloys containing immiscible elements such as lead and bismuth. The particle size and interparticle distance were about 30 to 130 nm and 20 to 200 nm for had particles and about 30 to 60 nm and 30 to 150 nm for (Pb- Bi) particles. The transition temperature,T _c, was in the range of 3.2 to 5.5 K for the Cu-M-Pb alloys and 6.2 to 6.3 K for the Cu-M-Pb-Bi alloys. Critical magnetic field,H _c2, and critical current density,J _c, for the later alloys were 0.47 to 0.93T at 4.2 K and 1.1 × 10⁵ to 2.7 × 10⁵ Am^–2 at zero applied field and 4.21 K. The mechanism of the appearance of such a soft-type superconductivity for the rapidly quenched copper-based alloys was discussed, and inferred to be due to the formation of a percolation path of a superconducting lead or Pb-Bi phase along the grain boundaries, sub-boundaries and/or tangled dislocations where the lead or Pb-Bi phase precipitated preferentially, rather than the proximity effect based on lead or Pb-Bi particles.