Leaching properties of chromate-containing epoxy films using radiotracers,PALS and SEM

Model chromate-containing epoxy primer (CEP) films were applied to aluminium alloy substrates using doctor blades. The effect of exposure to NaCl solution on the chromate-containing epoxy film was followed by monitoring the leaching behaviour of Cr. The continuous leaching of chromate inhibitor from the epoxy film is a self-healing characteristic that is designed to prevent corrosion of the aluminium alloy substrate. The CEP films were doped with ⁵¹Cr chromate inhibitor (t_1/2 = 27.7 days), were exposed to NaCl solutions over time, and the ⁵¹Cr gamma emission was used to monitor its release from the film into the aqueous solution. Pulsed beam positron lifetime spectroscopy and scanning electron microscopy (SEM) were used to probe structural changes that might transport properties of chromate species in the epoxy matrix. Positron Annihilation Lifetime Spectroscopy (PALS) was used to determine changes to free volumes at the nano scale in the films and SEM was used to ascertain the chromate distribution and structural scales at the micron level and above. Both PALS and SEM studies were preformed as a function of exposure time. It was found that a SrCrO₄ depletion zone was formed at the surface as a result of the complete dissolution of the inhibitor particles, suggesting that transport of the Sr²⁺ and CrO₄²⁻ might be through a network of channels created by the voids remaining in the epoxy matrix.     

Enabling decentralised management through federation

Cross-domain management is an increasingly important concern in network management and such management capability is a key-enabler of many emerging computing environments. This paper analyses the requirements for management systems that aim to support flexible and general capability sharing between autonomously managed domains. It introduces a novel Layered Federation Model (LFM) to structure this requirements analysis and describes the Federal Relationship Manager (FRM) which instantiates several layers of this model. The FRM combines semantic mapping management and authority management technologies to help solve several of the general management problems that are encountered whenever organisations enter into capability sharing agreements. An overview of related work on federation and the technical underpinnings of our approach are discussed and our work’s particular relevance to real world problems is explained through two service-centric use cases which involve the end-to-end delivery of a multimedia stream to a user’s home across several independent operators. Finally, experimental results are presented to highlight the practical advantages of our approach.     

Effect of moisture content and water mobility on microwave expansion of imitation cheese

The effects of moisture content (60–45%), and refrigerated storage (1–9 days) on the functional properties, water mobility and microwave expansion of imitation cheese are investigated. Cheese hardness, elastic (G′) and viscous moduli (G″) increased with decreasing moisture content and decreased during storage. Flowability, loss tangent (tan δ) and water mobility decreased with decreasing moisture content and increased during storage. Microwave expansion of imitation cheese decreased with decreasing moisture content and increased with prolonging storage time prior to microwaving. The changes in texture, rheology and flowability of cheese with decreasing moisture content, changes in water mobility and storage time reflected the level of cheese plasticisation by water and had strong linear correlations with microwave expansion. This work provides evidence that moisture content influences microwave expansion of imitation cheese by providing the driving force for expansion and plasticising the cheese matrix.     

Recycled content in polymer matrix composites through the use of A-glass fibers

The utility of recycled A-glass (primarily composed of soda-lime-silicate) fibers as reinforcement for structural composites has been studied. A series of plaques of unsaturated polyster composite were resin transfer molded with an A-glass continuous strand mat (CSM) and a control with E-glass CSM. The influence of fiber volume fraction on the physical and thermo-mechanical properties of the resultant composites were investigated, both before and after environmental exposure. At the maximum fiber fraction considered (nominally 29 vol%), the use of A-glass reinforcement lowered the warp direction tensile modulus from 8.6 to 7.6 GPa and strength from 139 to 100 MPa, relative to the control. Similar results were observed for both the flexural and the tensile properties, irrespective of fiber fraction and test direction (warp vs. weft), for the A-glass reinforcement. Environmental exposure was found to affect equally the properties of A-glass and E-glass fiber reinforced composites. Based upon microscopic analyses and constituent properties, the lower mechanical properties of the A-glass fibers composites have been linked to the lower properties of A-glass fibers relative to E-glass fibers. The experimental results were also used to test a micro-mechanics models for random fiber reinforced composites. Reasonable correlation was found between the experimental results and the theoretical predictions. To offset their lower mechanical properties, A-glass fibers could be used as a reinforcement in composite applications by simply increasing the fiber fraction relative to their E-glass counterpart.     

Recyclability of a continuous e-glass fiber reinforced polycarbonate composite

Fiber reinforced plastics are multi-component materials for which physical properties are strongly dependent on fiber and resin structure. Despite the disruptive nature of recycling methods on such structures, these materials nevertheless can be recycled. In this report, the recyclability of a fiber-reinforced cyclic BPA polycarbonate has been studied. It is found that ground up composite is recyclable and possesses properties as good as or better than a comparable commercial composite. The processing techniques investigated herein are injection, extrusion compression, and compression molding. As expected, processing technique and parameters are important in determining the mechanical properties of the molded regrind. Our results show that injection and extrusion compression molding yield recycled composites with good tensile properties, though the impact strengths are relatively low. This is due to high fiber orientation and fiber bundle dispersion. On the other hand, compression molded samples, which show random fiber orientation and low fiber bundles dispersion have relatively low tensile properties, but excellent impact strength. Results are discussed in terms of microstructural details, which include resin molecular weight and fiber length and orientation.     

Universal aspects of composite viscoelastic behavior

The viscoelastic behavior of a series of vinyl ester resins and E-glass fiber-reinforced composites is discussed. It is shown that the temperature shift factors for these systems, and others, suggests a universal behavior. A similar observation is made for the aging shift rate. On the other hand, the temperature dependence of compliance components per se appear to differ from system to system. Finally, it is shown that the retardation spectra for the vinyl ester resin and composites systems are the same to within a multiplicative constant in the glassy and in the short time transition regions. This shows that the presence of fibers has no influence on the distribution of retardation times in those regions.     

The relation between risk factors for binge eating and bulimia nervosa: A population-based female twin study.

This study investigated the differential risk factors for the initiation of binge eating and the transition from binge eating to bulimia nervosa. Women from a population-based twin registry (850 complete pairs) were assessed with respect to specific measured variables (including demographics, religiosity, lifetime psychopathology, current symptomatology, and personality) and latent genetic and environmental variables. Because of the relative rarity of bulimia nervosa, statistical power was low, but findings suggested considerable overlap between the genetic risk factors for the development of binge eating and the genetic risk factors for the transition from binge eating to bulimia nervosa. Genetic risk factors for binge eating and bulimia nervosa may be largely similar, whereas nonshared environment may be important in influencing the risk for bulimia nervosa once binge eating is initiated. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Extent, pattern, and correlates of remote memory impairment in Alzheimer's disease and Parkinson's disease.

Content and contextual memory for remote public figures and events was assessed with a modified version of the Presidents Test in patients with Alzheimer's disease (AD) or Parkinson's disease (PD). Contributions of executive functioning, semantic memory, and explicit anterograde memory to remote memory abilities were also examined. The AD group had temporally extensive deficits in content and contextual remote memory not accountable for by dementia severity. The PD group did not differ from the control group in remote memory, despite anterograde memory impairment. These results support the position that different component processes characterize remote memory, various mnemonic and nonmnemonic cognitive processes contribute to remote memory performance, and anterograde and remote memory processes are dissociable and differentially disrupted by neurodegenerative disease. (PsycINFO Database Record (c) 2010 APA, all rights reserved)