Thermal and mechanical stability of soldering QFP with Sn-Bi-Ag lead-free alloy

Thermal stability of the circuit boards with a quad flat package (QFP) soldered with Sn-58wt%Bi-(0, 0.5 and 1.0) wt% Ag and their microstructural features were evaluated. The addition of 1.0 wt% Ag causes the formation of large primary Ag/sub 3/Sn precipitates in the solder while no primary Ag/sub 3/Sn is found in Sn-57Bi-0.5Ag. Thermo-Calc calculation indicates that the lowest limit content for the formation of primary Ag/sub 3/Sn is about 0.8 wt%. Heat-exposure below 100/spl deg/C has no serious degradation on the joint structure for all solders. Heat-exposure at 125/spl deg/C caused serious degradation in joint strength for all alloys. The contamination of Pb from Sn-Pb surface plating on the components reduces the interface tolerance by forming ternary Sn-Pb-Bi phase melting at low temperature. Thermal fatigue between -20 and 80/spl deg/C does not have any significant influence on joint structure.     

Enhanced capacitance of composite anodic ZrO₂ films comprising high permittivity oxide nanocrystals and highly resistive amorphous oxide matrix

Anodic oxide films with nanocrystalline tetragonal ZrO(2) precipitated in an amorphous oxide matrix were formed on Zr-Si and Zr-Al alloys and had significantly enhanced capacitance in comparison with those formed on zirconium metal. The capacitance enhancement was associated with the formation of a high-temperature stable tetragonal ZrO(2) phase with high relative permittivity as well as increased ionic resistivity, which reduces the thickness of anodic oxide films at a certain formation voltage. However, there is a general empirical trend that single-phase materials with higher permittivity have lower ionic resistivity. This study presents a novel material design based on a nanocrystalline-amorphous composite anodic oxide film for capacitor applications.     

涤棉针织物分散/活性一浴一步法染色工艺

通过试验，优选出适合弱碱性与中性条件下一浴一步法染涤棉混纺针织物的染料和染色工艺。ERD系列分散染料较适合一浴法碱性浴染色，使用β-环糊精有增深作用，且匀染效果明显。部分B型染料在中性条件下比在弱碱性条件下的K／S值高。     

The mixed kidney cell-lymphocyte reaction in rats

Optimal conditions for obtaining the proliverative response in mixed kidney cell-lymphocyte culture (MKLC) have been determined in rats. The addition of 2-mercaptoethanol to the culture medium was essential for successful stimulation of lymphocytes by allogeneic kidney cells. Proliferative responses by standard MLC and MKLC were compared in rats with the same or a different Ag-B locus. In most strain combinations, there was a significant correlation between MLC and MKLC reactions, However, the DA-ACI combination, compatible at the Ag-B locus, consistently showed negative MLC and positive MKLC reactions. This suggested the possibility that this technique allowed the expression of kidney specific antigens.     

Laboratory and field measurements of dry deposition of sulfur dioxide onto Chinese loess surfaces

Laboratory and field measurements were conducted to examine dry deposition of SO2 onto Chinese loess surfaces using native soil sampled in the loess plateau, China. The field tests were employed in Beijing and Lanzhou, China, by directly measuring the dry deposition of SO2 on soil, which uses soil put on a collector as an SO2 passive sampling medium. In the laboratory, a high rate of uptake to SO2 deposition for Chinese soil surfaces due to the highly alkalinity was found. The uptake of SO2 deposition was dependent on the pH soil and relative humidity. Furthermore, we evaluated some factors that affect the measurement precision: response of SO2 uptake, repeatability, recovery factor, and variability associated with the weight and the surface coverage on the collectors. As a result, it was shown that the measurement precision was primarily related to the ratio of the SO2 deposition amount relative to the sulfur content of the original soil. This result was consistent with the field observations. The laboratory and field results indicated an excellent agreement on the SO2 uptake inherent in the results from the soil surfaces in different regions.     

Fluorescent in situ hybridization analysis of open lactic acid fermentation of kitchen refuse using rRNA-targeted oligonucleotide probes

Reproducible amounts of lactic acid accumulate in minced kitchen refuse under open conditions with intermittent pH neutralization [Sakai et al., Food Sci. Technol. Res., 6, 140 (2000)]. Here, we showed that such pH-controlled open fermentation of kitchen refuse reproducibly resulted a selective proliferation of a major lactic acid bacterial (LAB) species. In one experiment, the predominant microorganisms isolated during the early phase (6 h) were Gammaproteobacteria. In contrast, those that predominated during the late phase (48 h) were always Lactobacillus plantarum in three independent experiments. To further quantify the microbial community within open lactic acid fermentation, we performed fluorescent in situ hybridization (FISH) analysis targeting 16S (23S) rRNA. We designed two new group-specific DNA probes: LAC722(L) was active for most LAB including the genera Lactobacillus, Pediococcus, Leuconostoc and Weisella, whereas Lplan477 was specific for L. plantarum and its related species. We then optimized sample preparation using lysozyme and hybridization conditions including temperature, as well as the formamide concentration and the salt concentration in the washing buffer. We succeeded in quantification of microorganisms in semi-solid, complex biological materials such as minced kitchen refuse by taking color microphotographs in modified RGB balance on pre-coated slides. FISH analysis of the fermentation of kitchen refuse indicated that control of the pH swing leads to domination by the LAB population in minced kitchen refuse under open conditions. We also confirmed that L. plantarum, which generates lactic acid in high quantities but with low optical activity, became the dominant microorganism in kitchen refuse during the late phase of open fermentation.     

Cell cycle analysis of Chinese hamster ovary cells stimulated by phosphatidic acid in serum-free culture

When recombinant Chinese hamster ovary cells were treated with pertussis toxin or genistein, not only lysophosphatidic acid (LPA) but also phosphatidic acid (PA) failed to stimulate progression through the cell cycle in serum-free culture, suggesting that PA and LPA induce cell growth through the same signal transduction pathway. Cell cycle analysis also indicates that cell growth promoted by PA results in enhanced protein production.     

Micropatterned organoid culture of rat hepatocytes and HepG2 cells

The culture of liver cell organoids (multicellular aggregates) such as spheroids or cylindroids, which can strongly express liver functions, has been advocated as a useful technique that has advantages over monolayer culture. This paper describes a micropatterning technique for obtaining spheroids and cylindroids by using rat hepatocytes or HepG2 cells. We developed culture chips that comprised multiple, circular or rectangular microwells; the bottom surface of each microwell was modified with collagen to create a cell adhesion area, and the entire microwell, excluding the collagen-coated spots, was modified with polyethylene glycol (PEG) to create a nonadhesive area. Rat hepatocytes and HepG2 cells formed uniform spheroids and cylindroids on the circular and rectangular chips, respectively. Consequently, two-dimensional micropatterned chips containing homogeneous spheroids or cylindroids were generated. The expression of liver functions (protein secretion and ammonia removal) was greater in the spheroids and cylindroids than in the monolayer culture, and this expression was maintained for at least 2 weeks of culture. Thus, this chip technology has potential for use in various applications that involve organoid culture.     

The MHD effect and its relaxation process on electric current in the electrolysis of ferricyanide reduction and ferrocyanide oxidation

The electrolytic reduction of ferricyanide and the electrolytic oxidation of ferrocyanide have been carried out with exposing the magnetic field of 1000 or 1800 gauss. The current clearly increased after the magnetic exposure. The maximum current was obtained when the magnetic flux directed in parallel with the surface of electrode. These are speculated in terms of magnetohydrodynamic mechanism. The current decrease caused by relaxation process was observed after the removal of magnetic flux. The relaxation time obtained was temperature-dependent. Therefore the values of apparent transition energy, E_trans, were determined from the Arrhenius' plots of relaxation time against temperature. The magnitude of E_trans was dependent on the concentration of ferricyanide or ferrocyanide, and the viscosity and the conductivity of electrolyte solution. The activation energy of viscosity of electrolyte solution was compared with E_trans. As a conclusion, it was suggested that E_trans may be influenced by the velocity of magnetohydrodynamic flow, which was controlled by the diffusion current in electrolysis and the viscosity of electrolyte solution.