Morphology and growth pattern transition of intermetallic compounds between Cu and Sn-3.5Ag containing a small amount of additives

The morphology and grain growth pattern of intermetallic compounds (IMCs) formed between the Cu substrate and Sn-3.5Ag solder doped with a small amount of additive (0.1 mass%), say, Ni or Co, was investigated. After soldering, a duplex structure due to the additive discontinuity at the (Cu, Ni)₆Sn₅ and (Cu, Co)₆Sn₅ region was detected. That is, the outer area of the (Cu, Ni)₆Sn₅ and (Cu, Co)₆Sn₅ region on the solder side contained much higher Ni or Co additive concentration than the inner area on the Cu side. The faceted-shape IMCs were observed at the outer area, while the rounded-shape were identified at the inner area of (Cu, Ni)₆Sn₅ and (Cu, Co)₆Sn₅. Based on the thermodynamic calculation, the higher solubility of additive at the outer area will enhance the enthalpy change during interfacial reaction and lead to the larger Jackson’s parameter; thus, the faceted IMC morphology was formed. Moreover, the abnormal grain growth (AGG) at the outer area of (Cu, Ni)₆Sn₅ and (Cu, Co)₆Sn₅ was demonstrated from the IMC grain size distribution, while the normal grain growth pattern was suggested for the inner area of the IMC region.     

Intermetallic compounds formed during brazing of titanium with aluminium filler metals

The effect of aluminium filler metal composition on the formation of AI-Ti intermetallic compounds was investigated in brazed aluminium-to-titanium (Al/Ti) joints and titanium-totitanium (Ti/Ti) joints. The clearance filling ability was also studied. In Ti/Ti joints, the thickness of the intermetallic compound layer was strongly dependent on the aluminium filler metal composition, whereas the clearance filling ability was independent of the composition. The maximum intermetallic compound layer thickness was observed in 99.99% highly pure aluminium filler metal; therefore all additional elements reduced the layer thickness. Above all, the addition of 0.8% Si greatly reduced the thickness. After brazing at 680° C for 3 min, the intermetallic compound formed by Al-0 to 0.8% Si filler metal was found to be of type Al₃Ti. Other compounds, of types Ti₉Al₂₃ and Ti₇Al₅Si₁₂, were also found in joints brazed by Al-3 to 10% Si filler metals. AI-0.8% Si filler metals maintained a higher joint strength than pure aluminium filler metal under brazing conditions of high temperature and long heating time. In Al/Ti joints, AI-Cu-Sn and AI-Cu-Ag filler metal mainly formed Al₃Ti, and Al-10Si-Mg filler metal mainly formed Ti₇Al₅Si₁₂ at the brazed interface of the titanium side after brazing at 600 to 620° C.     

YF476 is a new potent and selective gastrin/cholecystokinin-B receptor antagonist in vitro and in vivo

Controversy exists as to whether the diabetic heart is more or less sensitive to ischemic injury. Although a considerable number of experimental studies have directly determined the effects of ischemia on the diabetic heart, there is still no general agreement as to whether metabolic changes within the myocardium contribute to the severity of ischemic injury. This paper reviews the evidence suggesting that the diabetic heart can actually be less sensitive to an episode of severe ischemia. Possible reasons for this decreased sensitivity to injury are discussed, which include a decreased accumulation of glycolytic products during ischemia (lactate and protons), as well as alterations in the regulation of intracellular pH in the diabetic heart. Based on existing studies, we suggest that although impaired glucose metabolism in the diabetic heart contributes to injury in hypoxic hearts or in hearts subjected to low-flow ischemia, diabetes-induced decreases in glycolysis can actually be beneficial to the diabetic heart during and following a severe ischemic episode. A decreased clearance of protons via the Na+/H+ exchanger may also contribute to the decreased sensitivity to ischemic injury in the diabetic heart.     

Regular network polyesters from benzenepolycarboxylic acids and glycol

Regular network polyesters were prepared from trimesic (Y), pyromellitic (X) or mellitic (Y_H) acids and 1,6-hexanediol (6G). Prepolymers prepared by melt-polycondensation were cast from dimethylformamide solution and post-polymerized at 260°C for various times to form a network. The resultant films were transparent, flexible and insoluble in organic solvents. Degrees of reaction estimated from the infra-red absorbance of ester and methylene groups were 95, 95 and 96% for 6GY, 6GX and 6GY_H post-polymerized for 12 h, respectively. X-ray diffraction intensity curves showed the formation of some ordered structure owing to the regular networks, and the degrees of ordering were 6GY> 6GX> 6GY_H. Densities were 1.227, 1.290 and 1.289 g cm⁻³ and heat distortion temperatures measured by thermomechanical analysis were 75, 72 and 75°C for 6GY, 6GX and 6GY_H post-polymerized for 12 h, respectively. Tensile strengths were in the order 6GY> 6GX> 6GY_H and Young's moduli were 6GY_H = 6GX> 6GY. Dye absorptions were 6GX> 6GY> 6GY_H, and water absorptions and weight losses in alkali solution were 6GY_H > 6GX> 6GY. These effects of the number of functional groups on the benzene ring on the structure and properties were discussed, and compared with those of previously reported network polymers.     

High-performance microwave circuits on LaAlO3

Microwave properties of high-temperature films deposited on LaAlO₃ substrate are presented. The films are grownin situ using a high-pressure single-source sputtering technique. Microwave resonators and filters are fabricated and tested. The maximum measuredQ values are 1400; the surface resistances were less than 360 between 4.2 and 50 K. The filter performance was 18 dB better than a similar filter fabricated in Ag.     

Effect of surface structure of porous silica microballoons on dynamic mechanical properties of amine cured epoxy resin composites

Dynamic mechanical properties were studied for epoxy resin filled with porous silica microballoons with varying surface area, pore radius, pore volume and adsorbed water. The glass transition temperature (T_g) of the composites is 12–14°C lower than the T_g of the unfilled epoxy resin. This T_g depression is attributed to the preferential adsorption of curing agents on the porous silica microballoons. Tg of the composite increases with increase in the adsorbed water on fillers. The storage modulus has a distinct correlation with the Hg-surface area of silica microballoons, which corresponds to the sum of the surface area of pores with radii larger than about 4 nm. Tan δ_c tan δ_m decreases with increasing Hg-surface area.     

Miscibility and adhesive properties of EVA‐based hot‐melt adhesives. II. Peel strength

A series of ethylene vinyl acetate copolymers (EVA) were blended with some tackifier resins that were made from wood extracts, and possible relations between their miscibility and properties as hot‐melt adhesives (HMA) were investigated. From our previous report on miscibility of various EVA‐based HMAs, we chose some blends that represent some of the typical miscibility types and investigated their peel strengths. When the blends were miscible at testing temperatures, the temperature at which the maximum value of peel strength was recorded tended to move toward higher temperature as tackifier content of blends increased. This result corresponds to the storage modulus of the blends whose curves tended to move toward higher temperature as tackifier content of blends increased when blend components were miscible as well as their maximum values of tan δ, or glass transition temperatures. It was characteristic for peel strength that there existed second peaks on peel strengths curves at ～ 100°C, which adhesive tensile strengths for the blends did not have. In terms of relationship between miscibility and HMA performances, we suggest that there are several factors other than miscibility that affect absolute values of peel strength more directly than miscibility; this idea has to be investigated further in the a future study. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 726–735, 2002     

Releasing property from surface polyion complex gel

Surface polyion complex (sPIC) gels were prepared with a nonionic hydrogel interior core, composed of poly(N‐vinylformamide and poly(N‐vinylacetamide), and a chemically bounded polyion complex layer on the outer surface, composed of poly(vinylamine) and poly(acrylic acid). The gels were investigated as controlled drug release models based on electrostatic interactions depending on pH. Methylene blue and allura red were employed as cationic and anionic drug models, respectively, and resulted in the selective adsorption depending on pH conditions. Monovalent and multivalent anionic drug models, allura red and 1,3,6‐naphthalenetrisulfonate were observed for their releasing behavior from the sPIC gel. The results indicated that the multivalent anionic drug effectively controlled release depending on pH conditions. We further investigated sPIC gels regarding their ability to control the release of ionic molecules as a function of pH‐driven changes in electrostatic interactions. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42081.     

Synergistic Actions of Tailoring Enzymes in Pradimicin Biosynthesis

Three key tailoring enzymes in pradimicin biosynthesis: PdmJ, PdmW, and PdmN, were investigated. PdmW was characterized as the C‐6 hydroxylase by structural characterization of the corresponding product, 6‐hydroxy‐G‐2A. The efficiencies of the C‐5 and C‐6 hydroxylations, catalyzed respectively by PdmJ and PdmW, were low when they were expressed individually with the early biosynthetic enzymes that form G‐2A. When these two cytochrome P450 enzymes were co‐expressed, a dihydroxylated product, 5,6‐dihydroxy‐G‐2A, was efficiently produced, indicating that these two enzymes work synergistically in pradimicin biosynthesis. Heterologously expressed PdmN in Streptomyces coelicolor CH999 converted G‐2A to JX137a by ligating a unit of D ‐alanine to the carboxyl group. PdmN has relaxed substrate specificity toward both amino acid donors and acceptors. Through combinatorial biosynthesis, a series of new pradimicin analogues were produced.