Fracture dynamics of sprayed and laser-glazed titania by an inverse processing of elastic waves

A new elastic wave (EW) or acoustic emission (AE) monitoring and signal processing system has been developed and used to elucidate the fracture behavior of sprayed and laser-glazed ceramic coatings. The system measures the minute surface displacements excited by the propagation of elastic waves. It enables elucidation of the fracture dynamics (fracture mode and kinetics) of stressed coatings. The surface displacement at the sensor position was computed by the convolution integral of an assumed source wave with the dynamic Green’s function until signals resembled the measured wave. This new signal processing method was used to determine the fracture strength and dynamics of microcracks in sprayed and laser-glazed titania subjected to four-point bending. It was found that mode II shear cracking along the interface between the coating and substrate occurred prior to mode I cleavage cracking. The fracture strength of laser-glazed titania was higher than that of as-sprayed titania in most cases; however, this depended on the coating structure. This article introduces the principle of source inversion processing of elastic waves, the monitoring system, laser glazing of sprayed titania, and experimental work on the fracture behavior of titania coatings.     

Confocal microscopy of human lens membranes in aged normal and nuclear cataracts

PURPOSE: To visualize the structure and determine the continuity of lipid membranes in lens fiber cells (LFCs) from human aged normal and cataractous lenses. METHODS: Thick sections from human nuclear cataracts and aged normal lenses were stained with the lipophilic probe DiI, and then analyzed by confocal microscopy. Staining patterns of membranes were observed in individual optical sections or three-dimensional projections of z-series taken in longitudinal section and cross-section of LFCs from different regions within the lens nucleus. RESULTS: DiI bound to and delineated the plasma membrane of LFCs from all regions of the lens nucleus. Three-dimensional projections of z-series from aged normal and cataractous lenses suggested that some of the stained lipid membranes were not continuous with LFC plasma membrane of cataractous lenses. CONCLUSIONS: The results obtained using these methods demonstrated that lipid membranes, discontinuous with the plasma membrane of LFCs, were indicative of a novel process occurring predominately in cataractous human lenses.     

Synthesis and biological activities of optically active 6-[3-(3,4-dimethoxybenzylamino)-2-hydroxypropoxy]-2(1H)-quinolinone (OPC-18790)

The enantiomers of 6-[3-(3,4-dimethoxybenzylamino)-2-hydroxypropoxy]-2(1H)-quinolinon e (OPC-18790), a novel cardiotonic agent, were synthesized and evaluated for positive inotropic activity. The key intermediates, 2,3-epoxypropoxy derivatives, were obtained by the alkylation of 6-hydroxy-2(1H)-quinolinone with optically active epichlorohydrin and subsequent ring closure. In an in vitro study, the (R)-(+)-isomer was about 10-fold more potent than the (S)-(-)-isomer.     

In vitro antifungal and fungicidal activities and erythrocyte toxicities of cyclic lipodepsinonapeptides produced by Pseudomonas syringae pv. syringae

Recent increases in fungal infections, the few available antifungal drugs, and increasing fungal resistance to the available antifungal drugs have resulted in a broadening of the search for new antifungal agents. Strains of Pseudomonas syringae pv. syringae produce cyclic lipodepsinonapeptides with antifungal activity. The in vitro antifungal and fungicidal activities of three cyclic lipodepsinonapeptides (syringomycin E, syringotoxin B, and syringostatin A) against medically important isolates were evaluated by a standard broth microdilution susceptibility method. Erythrocyte toxicities were also evaluated. All three compounds showed broad antifungal activities and fungicidal actions against most of the fungi tested. Overall, the cyclic lipodepsinonapeptides were more effective against yeasts than against the filamentous fungi. Syringomycin E and syringostatin A had very similar antifungal activities (2.5 to > 40 micrograms/ml) and erythrocyte toxicities. Syringotoxin B was generally less active (0.8 to 200 micrograms/ml) than syringomycin E and syringostatin A against most fungi and was less toxic to erythrocytes. With opportunities for modification, these compounds are potential lead compounds for improved antifungal agents.     

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.     

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