Determination of cracking resistance of thermal spray coatings during four-point bend testing using an acoustic emission technique

An acoustic emission (AE) technique was used for the determination of the onset of cracking of thermal spray self-fluxing NiCrFeBSi coatings under tensile loading using a 4-point bend testing apparatus. These coatings were flame sprayed on 42CrMoS4 cylinders having different diameters. Two different post-treatment fusing processes, induction, and flame fusing, were used. Along with the investigations of the effect of cylinder diameters and fusing processes onto the cracking resistance of the coatings, the effect of the same two parameters on the residual stresses was also investigated. Results show that, independently of the diameter of the cylinder, the flame-fused coatings possess a higher cracking resistance than their induction-fused counterparts, i.e., that the strain to fracture is higher for the flame-fused coatings. A correlation between the strain to fracture and the residual strain in the coatings has been established. This study points out that the combination of an AE technique with a bending test apparatus shows some major benefits to obtain important information on the relative ductility of thermal spray coatings.     

Myotonic dystrophy protein kinase gene expression in skeletal muscle from congenitally affected infants

Thiothrix spp., sulfide-oxidizing filamentous bacteria, were found to be a principal bacterial component of aquatic biofilms causing biofouling in selected municipal water storage tanks, private wells, and drip irrigation systems in Florida. Treatments of up to 200 ppm chlorine in the affected systems could not prevent return of the biofouling problem. The water originated from the upper Floridan aquifer and associated surficial aquifers in central and north Florida. Samples were examined where visible biofilms had a white, filamentous appearance, indicative of Thiothrix spp. The detection of Thiothrix spp. was confirmed by enzyme-liked immunosorbent assay (ELISA), indirect immunofluorescence (IIF), and microbiological procedures. It was estimated through immunocytochemical procedures that Thiothrix spp. comprised 18% of the biofilm in the municipal water storage tanks. These observations confirm that specific biological and chemical interactions may induce physical changes leading to significant biofouling.     

Magnitude of sex differences in spatial abilities: A meta-analysis and consideration of critical variables.

In recent years, the magnitude, consistency, and stability across time of cognitive sex differences have been questioned. The present study examined these issues in the context of spatial abilities. A meta-analysis of 286 effect sizes from a variety of spatial ability measures was conducted. Effect sizes were partitioned by the specific test used and by a number of variables related to the experimental procedure in order to achieve homogeneity. Results showed that sex differences are significant in several tests but that some intertest differences exist. Partial support was found for the notion that the magnitude of sex differences has decreased in recent years. Finally, it was found that the age of emergence of sex differences depends on the test used. Results are discussed with regard to their implications for the study of sex differences in spatial abilities. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Subgrain growth in Al and Al-1% Mn during annealing

The subgrain growth during annealing of cold-worked Al-1% Mn and Al(4N) has been measured in the temperature intervals 300 to 400° C and 100 to 200° C respectively. For Al-1%Mn the subgrain diameter showed a parabolic growth, while for Al the diameter gradually reached a constant value. The microstructural investigations which included in situ annealing in a high voltage electron microscope demonstrated that the operating mechanism for growth in the higher temperature range was collective migration of sub-boundary dislocations. In the lower temperature range extraction of dislocations was found to be the dominating mechanism, i.e. dislocations partly lying in the boundaries are pulled out by the stress field in the subgrain interior. The observed growth rates were consistent with models for these mechanisms presented in two previous papers.     

Personality profiles of gifted women: Psychologists.

Compared the responses to the 16PF of 124 highly successful women psychologists with women in general, college women, and successful academic men to identify personality factors enabling these women to succeed in spite of powerful sex-role expectations to the contrary. In terms of test scores, women psychologists were significantly more intelligent, socially aloof, dominant, serious, adventuresome, sensitive, flexible, imaginative, insightful, unconventional, secure, self-sufficient, and less anxiety-prone than women in general and college girls. Despite similar test profiles of successful academic men and women, the women scored higher on intelligence, radicalism, and super-ego strength, and lower on self-sentiment. Women who published extensively were more exacting and socially aloof than less productive women psychologists. (28 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Contribution of skin and stone to texture measurements of spherical model fruits

Fruits are composite materials often surrounded by a skin and sometimes containing rigid stones (pits). To understand the contribution of skin and stone to the overall texture of the fruit, model fruits were constructed from molded gelatin spheres, with rigid inclusions and a skin layer. Cross polarized light revealed the stress distribution during puncture testing and the mechanical measures of firmness, Poisson's ratio and breaking force were determined. Skin significantly raised the breaking force. Spherical stones raised the firmness—effectively reducing the deformable material in the sphere, resulting in inflated strains. Disc shaped stones compared with spherical ones, with the narrow edge normal to the force acted like an internal blade and significantly lowered the breaking force. Neither skin nor stone had any significant impact on Poisson's ratio. Three examples of real fruit (raspberries, grapes, and cherries) were tested to contextualize the findings.

Practical applications

Consumers gently squeeze fruit to gauge ripeness. Unwittingly, what we perceive while squeezing fruit is not wholly dependent on the texture of the internal flesh. In this work, we have attempted to model how the firmness and breaking force are influenced by the presence of a skin and stones of various size and shape. This has implications in both sensory and instrumental fruit testing.     

Synthesis and nano-mechanical characterization of calcium-silicate-hydrate (C-S-H) made with 1.5 CaO/SiO2 mixture

In this study, calcium silicate hydrate (C-S-H) is synthesized and characterized. C-S-H slurry was made with calcium oxide (CaO) to micro-silica (SiO₂) mixture ratio of 1.5 and enough deionized water. The slurry was continuously mixed for 7 days, then the excess water was removed. Two methods of drying were implemented: one method used the standard d-dry technique and the other was equilibrated to 11% relative humidity (RH). The dried powders were characterized using thermo gravimetric analysis (TGA), X-ray diffraction analysis (XRDA), and ²⁹Si magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy. The stoichiometric formulas of synthetic C-S-H powders dried to d-dry and 11% RH in this study were approximated as C_1.2SH_0.7 and C_1.2SH_2.4 respectively. The powders were then compacted to create specimens with porosities similar to C-S-H in hydrated cement. The specimens underwent nanoindentation to mechanically characterize C-S-H. The experiments provide insight on the nanoscale mechanical characteristics of C-S-H.     

Improved wear performance by the incorporation of solid lubricants during thermal spraying

For components that are required to function in sliding or rubbing contact with other parts, degradation often occurs through wear due to friction between the two contacting surfaces. Depending on the nature of the materials being used, the addition of water as a lubricant may introduce corrosion and accelerate the degradation process. To improve the performance and increase the life of these components, coatings may be applied to the regions subject to the greatest wear. These coatings may be engineered to provide internal pockets of solid lubricant in order to improve the tribological performance. In the present study, coatings containing a solid lubricant were produced by thermal spraying feedstock powders consisting of a blend of tungsten carbide-metal and a fluorinated ethylene-propylene (FEP) copolymer-based material. The volume content of this teflon-based material in the feedstock ranged from 3.5 to 36%. These feedstocks were deposited using a high velocity oxy-fuel (HVOF) system to produce coatings having a level of porosity below 2%. Sliding wear tests in which coated rotors were tested in contact with stationary carbon-graphite disks identified an optimum level of teflon-based material in the feedstock formulation required to produce coatings exhibiting minimum wear. This optimum level was in the range of 7 to 17% by volume and depended on the composition of the cermet constituent. Reductions in mass loss for the couples on the order of 50% (an improvement in performance by a factor of approximately 2) were obtained for the best performing compositions, as compared to couples in which the coating contained no solid lubricant.