Mechanical and thermal properties of polyolefin thermoplastic elastomer blends

ABSTRACT

Polyolefin thermoplastic elastomers (POEs) are a class of thermoplastic elastomer (TPE) that can be easily processed. POEs have broad applications from automobiles to footwear and it is desirable to be able to alter the microstructure and properties. In this work, a systematic study of how blending and thermal processing of POEs affects mechanical and thermal properties is undertaken. Ethylene-octene copolymer POEs with different degrees of crystallinity are blended, compounded, and moulded and then slow cooled, quenched, or annealed. Differential scanning calorimetry (DSC) results show that the blends are immiscible and that quenching suppresses crystallinity while annealing thickens crystals. More crystals of the same thickness or thicker crystals of the same amount in the blends result in a higher modulus, lower elastic recovery, and more residual strain or permanent deformation after tensile testing. Microstructural control will allow for the optimal design of elastomeric materials with anticipated properties.     

In–Situ Transmission Electron Microscopy Crystallization Studies of Sol–Gel-Derived Barium Titanate Thin Films

Barium titanate (BaTiO₃) thin films that were derived from methoxypropoxide precursors were deposited onto (100) Si, Pt/Ti/SiO₂/(100) Si, and molecular-beam-epitaxy-grown (MBE-grown) (100) BaTiO₃ on (100) Si substrates by spin coating. The crystallization behavior of the amorphous-gel films was characterized using in-situ transmission electron microscopy heating experiments, glancing-angle X-ray diffraction, and differential thermal analysis/thermogravimetric analysis. Amorphous-gel films crystallized at a temperature of ∼600°C to an intermediate nanoscale (5–10 nm) barium titanium carbonate phase, presumably BaTiO₂CO₃, that subsequently transformed to nanocrystalline (20–60 nm) BaTiO₃. Random nucleation in the bulk of the gel film was observed on all substrates. In addition, oriented growth of BaTiO₃ was concurrently observed on MBE-grown BaTiO₃ on (100) Si. High-temperature decomposition of the intermediate carbonate phase contributed to nanometer-scale residual porosity in the films. High concentrations of water of hydrolysis inhibited the formation of the intermediate carbonate phase; however, these sols precipitated and were not suitable for spin coating.     

Information systems sourcing: examining the privatization option in USA public administration

The process and content of decision-making on sourcing information systems (IS) is assessed. Two case histories from the USA public sector are examined in detail. We find that outsourcing IS problems, as opposed to tasks, rarely works in either private or public sectors. The findings suggest that both sectors must develop similar IS competencies before considering sourcing decisions. These include fostering relationships with senior management, bench-marking performance, creating shared IS objectives, understanding requirements, diagnosing IS problems, evaluating in-house versus market capabilities and, in the case of outsourcing, developing competencies in contract negotiation and post-contract management. The major difference between public and private sector sourcing was found to be that public sector agencies faced more environmental constraints, including dictated budgets and requirements, and restrictions on civil servant salaries.     

Brief Intelligence Testing in Australia, Canada, the United Kingdom, and the United States.

Do you use brief measures of intelligence? There is available an increasing variety of short forms and new and revised quick tests of intelligence. However, little is known about clinical practice using these abbreviated instruments. The authors report the results of a 4-country exploratory survey of the extent and circumstances of the use of short forms and quick tests. Such measures are commonly used, and practitioners generally followed literature-based advice about the role of brief measures. However, idiosyncratic subtest combinations and inappropriate prorating were also prevalent with short forms. Frequently used quick tests were identified, as were the reasons for using brief measures. The authors offer specific recommendations for the appropriate use of brief measures. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

An emotion-induced attentional blink elicited by aversively conditioned stimuli.

The current study examines whether aversively conditioned stimuli can modulate attention to such a degree that they impair the perception of subsequently presented nonemotional targets. In the initial phase of this study, participants viewed 3 categories of photographs, 1 of which was paired with an aversive noise. Following conditioning, participants searched for a target embedded within a series of 17 rapidly presented images on each trial. Critically, a conditioned or unconditioned item from the initial phase appeared 200 ms or 800 ms before the target. At 200-ms lags but not 800-ms lags, the conditioned images impaired target detection relative to the other distractors. Thus, temporary visual deficits can be induced by otherwise neutral distractors whose aversive associations have only recently been learned. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Tensile properties of two responsive hydrogels

Temperature-responsive hydrogels were prepared from N-vinyl caprolactam/ethylene glycol dimethacrylate (PVCL) or from hydroxypropylcellulose/divinyl sulfone (HPC). Both gels undergo reversible volume shrinkage between room temperature and 50 °C, and for both, the tensile stress–strain behavior in the collapsed state above the temperature-induced transition is qualitatively different from that at room temperature. At the higher temperature, PVCL gels become stiffer, more ductile, and more viscoelastic. HPC gels, on the other hand, have lower initial tangent moduli in the high-temperature state. Possible molecular mechanisms are suggested, and implications for the design of temperature-responsive actuators (‘artificial muscles’) from these materials are discussed.     

Simulation of the transmission of Salmonella enteritidis phage type 4 in a flock of laying hens

Simulation of disease transmission in laying flocks infected with Salmonella enteritidis phage type 4 over a 48-week egg-production period indicated that the maximum weekly incidence risk could range from 0.05 to 0.28, and the maximum proportion of culture-positive birds could range from 0.20 to 0.77 of the flock, depending on the effective contact rate. If the egg contamination proportion were 0.08, contaminated egg production could vary from a weekly maximum of 0.42 per cent to 2.24 per cent depending on the effective contact rate, but the actual rate of contamination was more important in determining the numbers of infected eggs produced. The results from previous studies suggest that this proportion could range from 0.075 to 0.25. The model produced levels of infected and immune birds similar to those reported in the literature, suggesting effective contact rates of between 2 and 4.5. There is insufficient information on transmission cycles to validate the model, but it does provide a mechanism for consolidating research findings, reviewing areas for further research, and aiding more effective planning for disease control.     

Evidence that the age at diagnosis of IDDM is genetically determined

Recent studies have suggested that clot-bound thrombin plays an important role in thrombus growth. In this study, we examined the effects of recombinant human soluble thrombomodulin (rhsTM) on clot-induced coagulation. rhsTM enhanced the activation of protein C by clots, and attenuated clot-induced thrombin generation and fibrinopeptide A (FPA) production in a dose-dependent manner. The inhibitory effect of rhsTM was abolished by anti-protein C antibody. The inhibitory effect of rhsTM on clot-induced thrombin generation continued for over 60 min after the addition of the clot, while an active site-directed thrombin inhibitor, argatroban, produced a more transient inhibition. rhsTM also inhibited the regrowth of the clot in (125)I-fibrinogen-supplemented plasma. We also examined the effect of rhsTM by thromboelastography, rhsTM reduced the growth of the clot but had little effect on the time to begin clotting, while heparin and Fragmin (low molecular weight heparin) had effects opposite to those of rhsTM. These findings suggest that rhs-TM attenuates the growth of the clot by activating protein C and inhibiting further thrombin generation in the clot.