Creep rupture of a linear polyethylene: 1. Rupture and pre-rupture phenomena

The creep rupture behaviour of a high-density polyethylene was studied for material prepared at two different cooling rates. The rupture phenomena were dependent upon the morphology. The slow-cooled specimens had a degenerated spherulitic structure and all underwent brittle rupture. The fast-cooled specimens had a banded spherulitic structure and exhibited either ductile or brittle rupture depending upon the applied stress. Ductile creep rupture was associated with a large tertiary creep strain, with macro-necking and a stress whitening which corresponded to an increase in volumetric strain. Brittle creep rupture was associated with an absence of macro-necking, and either an absence or a small amount of tertiary creep. Stress whitening corresponding to a decrease in volumetric strain was a feature of both forms of failure above a threshold value of stress.     

Mechanical properties of elastomeric composite membranes made from the porous biaxially drawn ultrahigh-molecular-weight polyethylene film and polyether polyurethane materials

Fibrous composites are commonly found in soft tissue but few man-made composites are used for soft tissue replacement. In this study, fibrous composites, made from biaxially drawn ultra-high molecular-weight polyethylene (BD-UHMWPE) and polyether polyurethane materials, were fabricated by solution casting and heat compaction. The effects of processing conditions on tensile properties of the composites were evaluated, in terms of the molecular structures of the polyurethane materials, thermal behavior of the UHMWPE, and the microstructures of the as-made composites. The results indicated that composites of improved tensile properties were constructed in the form of interpenetration of polyurethane through the stacks of the BD-UHMWPE. The tensile strength and modulus of the composites (made from Toyobo TM5 and Solupor™ 7P03) are approximately 69 and 210 MPa. The as-made composite has a significant improvement on its toughness, about 5 times increase in the tensile toughness if compared to that of the BD-UHMWPE. A possible interlocking structure was suggested for those polyurethane materials (Toyobo TM5) that might be recrystallized during heat compaction. The polyurethane like Tecoflex 80A, not indicating a symptom of annealing crystallization, has no impact on increasing the tensile properties but a decrease with plasticizing the materials.     

Design optimization and fatigue testing of an electronically-driven mechanically-resonant cantilever spring mechanism

A light scanning device consisting of an electronically-driven mechanically-resonant cantilever spring-mirror system has been developed for innovative lighting applications. The repeated flexing of the cantilever spring during operation can lead to premature fatigue failure. A model was created to optimize the spring design. The optimized spring design can reduce stress by approximately one-third from the initial design. Fatigue testing showed that the optimized spring design can operate continuously for over 1 month without failure. Analysis of failures indicates surface cracks near the root of the spring are responsible for the failures.     

Ozonation of a mixture of dialkylphthalates in aqueous solution

Ozonation of dimethyl phthalate, diethyl phthalate and dipropyl phthalate was carried out to evaluate the potential of ozonation for phthalate removal from water. Phthalates with longer alkyl chains, which are often more resistant to biodegradation were found to be more degradable than those with shorter alkyl chains. The degradation of phthalates by ozonation follows the pseudo‐first‐order kinetic model. The rate of phthalates degradation increased exponentially with increasing temperature in the range studied (20 to 50 °C) and in proportion with applied ozone dosages. The rate of phthalates degradation was found to increase with increasing pH of the solution from 2.6 to 11.0, and decreased exponentially with increasing initial concentrations of the phthalates. Degradation of phthalates via ozonation was found to develop dominantly through direct reaction with hydroxyl radicals. Copyright © 2010 Society of Chemical Industry     

Sexual Versus Nonsexual Workplace Aggression and Victims' Overall Job Satisfaction: A Meta-Analysis.

A meta-analytic approach was used to examine whether sexual and nonsexual forms of nonviolent workplace aggression (both verbal and nonverbal) share equivalent or differential relationships with victims' overall job satisfaction. When the meta-analytic comparison was restricted to all-female samples to hold victims' gender constant, nonsexual aggression was found to share a significantly stronger negative relationship with victims' overall job satisfaction than was sexual aggression. In addition, nonsexual aggression was found to share a stronger negative link with women's level of job satisfaction than with men's. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Comparison of the degradation of polycaprolactone and polycaprolactone–(β‐tricalcium phosphate) scaffolds in alkaline medium

The design and fabrication of scaffolds and biodegradable devices using slow‐degrading polymers and composites (degradation/resorption > 2 years) involve the necessity for long‐term in vitro and in vivo studies. If multiple designs and materials need to be tested, then this would use much time and financial resources. Accelerated degradation systems aim to achieve comparable degradation profiles within a shorter period of time. This investigation considers the hydrolytic degradation of polycaprolactone (PCL) and PCL–calcium phosphate (CaP) scaffolds in 5 mol L^?1 NaOH at 37 °C. The scaffolds degrade via surface erosion, which proceeds in a consistent and predictable manner. The hydrolytic degradation of PCL‐based scaffolds alone is slow, governed by their high molecular weights, crystallinity, hydrophobicity, surface‐to‐volume ratio and porosity. The incorporation of CaP significantly increases the degradation rate. Copyright © 2007 Society of Chemical Industry     

Effects of binary solvent extraction system,extraction time and extraction temperature on phenolic antioxidants and antioxidant capacity from mengkudu (Morinda citrifolia)

An investigation into the effects of ethanol concentration (0–100%, v/v), extraction time (20–120 min) and extraction temperature (25–65 °C) on the extraction of phenolic antioxidants from mengkudu (Morinda citrifolia) was performed using a single-factor experiment. Total phenolic content (TPC) and total flavonoid content (TFC) assays were used for determination of phenolic compounds. Antioxidant capacity was evaluated by measuring the scavenging effect on 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) and 2,2′-diphenyl-1-picrylhydrazyl (DPPH) radicals. Experimental results showed that extraction conditions had significant effect on extraction of phenolic compounds and antioxidant capacities. The optimised conditions were 40% ethanol for 80 min at 65 °C, with values of 919.95 mg GAE/100 g DW for TPC, 472.73 mg CE/100 g DW for TFC, 791.71 μmol TEAC/100 g DW for ABTS and 1928.5 μmol TEAC/100 g DW for DPPH. TPC was significantly correlated with DPPH under the effects of ethanol concentration (r = 0.932) and extraction time (r = −0.938).     

Fluctuating asymmetry, sociosexuality, and intrasexual competitive tactics

Heterosexual men and women were told they were competing with another same-sex individual for a date with an attractive opposite-sex interviewer. After answering 6 questions, participants were asked to tell the competitor why the interviewer should choose them over the competitor. Participants' videotaped behavior was coded for different behavioral tactics. Men who were more symmetrical and who had a more unrestricted sociosexual orientation were more likely to use direct competition tactics than were less symmetrical and restricted men. Restricted men accentuated their positive personal qualities, presenting themselves as "nice guys." Structural equation modeling revealed that fluctuating asymmetry (FA) was directly associated with the use of direct competition tactics. However, the link between FA and presenting oneself as a nice guy was mediated through sociosexuality. No effects were found for women.