The formation of ultrafine ferrite and low temperature bainite through thermomechanical processing

In the current study, a novel approach was employed to produce a unique combination of ultrafine ferrite grains and low temperature bainite in a low carbon steel with a high hardenability. The thermomechanical route included warm deformation of supercooled austenite followed by reheating in the ferrite region and then cooling to bainitic transformation regime (i.e. 400-250°C). The resultant microstructure was ultrafine ferrite grains (i.e. <4μm) and very fine bainite consisting of bainitic ferrite laths with high dislocation density and retained austenite films. This microstructure offers a unique combination of ultimate tensile strength and elongation due to the presence of ductile fine ferrite grains and hard low temperature bainitic ferrite laths with retained austenite films. The microstructural characteristics of bainite were studied using optical microscopy in conjunction with scanning and transmission electron microscopy techniques.

Biodegradable Mg-Zr-Ca alloys for bone implant materials

Mg–Zr–Ca alloys were developed for new biodegradable bone implant materials. The microstructure and mechanical property of the Mg–xZr–yCa [x=0·5, 1·0% and y=1·0, 2·0% (wt-% hereafter)] alloys were characterised by optical microscopy, compressive and hardness tests. The in vitro cytotoxicity of the alloys was assessed using osteoblast-like SaOS₂ cells. The corrosion behaviour of these alloys was evaluated by soaking the alloys in simulated body fluid (SBF) and modified minimum essential medium (MMEM). Results indicated that the mechanical properties of the Mg–Zr–Ca are in the range of the mechanical properties of natural bone. The corrosion rate and biocompatibility decreases with the increase in the Ca content in the Mg–Zr–Ca alloys. The solutions of SBF and MMEM with the immersion of the Mg–Zr–Ca alloys show strong alkalisation. The Zr addition to the Mg–Zr–Ca alloys leads to an increase in the corrosion resistance, compressive strength and the ductility of the alloys, and a decrease in the elastic modulus of the Mg–Zr–Ca alloys.

The inhibition of hydrogen embrittlement in SAE 4340 steel in an aqueous environment with the rare earth compound lanthanum 4 hydroxy cinnamate

A preliminary study showed that the inhibitor lanthanum 4-hydroxy cinnamate ((La4OHcin)₃) at a concentration of 400 ppm prevented the hydrogen embrittlement (HE) of SAE 4340 steel tensile specimens when tested under slow strain rate conditions in a 0.01M NaCl. In the presence of the inhibitor, a complex film formed on the surface of specimens during the slow strain rate test (SSRT), and no corrosion pits were detected. Electrochemical polarization studies indicated that the La(4OHcin)₃ acted as an anodic inhibitor in the NaCl solution. This article also discusses the mechanism of HE inhibition by La(4OHcin)₃.

Arginase II inhibition prevents nitrate tolerance

BACKGROUND AND PURPOSE Nitrate tolerance, the loss of vascular responsiveness with continued use of nitrates, remains incompletely understood and is a limitation of these therapeutic agents. Vascular superoxide, generated by uncoupled endothelial NOS (eNOS), may play a role. As arginase competes with eNOS for L-arginine and may exacerbate the production of reactive oxygen species (ROS), we hypothesized that arginase inhibition might reduce nitrate tolerance.

EXPERIMENTAL APPROACH Vasodilator responses were measured in aorta from C57Bl/6 and arginase II knockout (argII –/–) mice using myography. Uncoupling of eNOS, determined as eNOS monomer : dimer ratio, was assessed using low-temperature SDS-PAGE and ROS levels were measured using L-012 and lucigenin-enhanced chemiluminescence.

KEY RESULTS Repeated application of glyceryl trinitrate (GTN) on aorta isolated from C57Bl/6 mice produced a 32-fold rightward shift of the concentration–response curve. However this rightward shift (or resultant tolerance) was not observed in the presence of the arginase inhibitor (s)-(2-boronethyl)-L-cysteine HCl (BEC; 100 µM) nor in aorta isolated from argII –/– mice. Similar findings were obtained after inducing nitrate tolerance in vivo. Repeated administration of GTN in human umbilical vein endothelial cells induced uncoupling of eNOS from its dimeric state and increased ROS levels, which were reduced with arginase inhibition and exogenous L-arginine. Aortae from GTN tolerant C57Bl/6 mice exhibited increased arginase activity and ROS production, whereas vessels from argII –/– mice did not.

CONCLUSION AND IMPLICATIONS Arginase II removal prevents nitrate tolerance. This may be due to decreased uncoupling of eNOS and consequent ROS production.

Feeding back and enhancing authentic learning in quality course assessment design : locating information systems education in rigorous educational research

Locating information systems education foursquare within rigorous and substantial educational research is crucial if the discipline is to receive the scholarly attention that it warrants. One way to do that is to highlight how current information systems course design in Australian undergraduate and postgraduate programs exhibits the strongest possible elements of contemporary learning theories. This paper analyses selected features of the design of an information systems postgraduate course in an Australian university, including the use of peer review of journal entries and writing professional reports to enhance authentic learning and maximise quality assessment design. The analysis is framed by the principles of instructional design theory (Snyder 2009). The authors argue that, by demonstrating theoretically grounded and effective educational practice, the course highlights the value of being located in wider educational research, and of bringing the two fields more closely together.

The behavioural response of Australian fur seals to motor boat noise

Australian fur seals breed on thirteen islands located in the Bass Strait, Australia. Land access to these islands is restricted, minimising human presence but boat access is still permissible with limitations on approach distances. Thirty-two controlled noise exposure experiments were conducted on breeding Australian fur seals to determine their behavioural response to controlled in-air motor boat noise on Kanowna Island (39°10′S, 146°18′E). Our results show there were significant differences in the seals' behaviour at low (64–70 dB) versus high (75–85 dB) sound levels, with seals orientating themselves towards or physically moving away from the louder boat noise at three different sound levels. Furthermore, seals responded more aggressively with one another and were more alert when they heard louder boat noise. Australian fur seals demonstrated plasticity in their vocal responses to boat noise with calls being significantly different between the various sound intensities and barks tending to get faster as the boat noise got louder. These results suggest that Australian fur seals on Kanowna Island show behavioural disturbance to high level boat noise. Consequently, it is recommended that an appropriate level of received boat sound emissions at breeding fur seal colonies be below 74 dB and that these findings be taken into account when evaluating appropriate approach distances and speed limits for boats.

Hormonal responses to extreme fasting in subantarctic fur seal (Arctocephalus tropicalis) pups

Surviving prolonged fasting implies closely regulated alterations in fuel provisioning to meet metabolic requirements, while preserving homeostasis. Little is known, however, of the endocrine regulations governing such metabolic adaptations in naturally fasting free-ranging animals. The hormonal responses to natural prolonged fasting and how they correlate to the metabolic adaptations observed, were investigated in subantarctic fur seal (Arctocephalus tropicalis) pups, which, because of the intermittent pattern of maternal attendance, repeatedly endure exceptionally long fasting episodes throughout their development (1–3 mo). Phase I fasting was characterized by a dramatic decrease in plasma insulin, glucagon, leptin, and total L-thyroxine (T4) associated with reductions in mass-specific resting metabolic rate (RMR), plasma triglycerides, glycerol, and urea-to-creatine ratio, while nonesterified fatty acids (NEFA) and β-OHB increased. In contrast, the metabolic steady-state of phase II fasting reached within 6 days was associated with minimal concentrations of insulin, glucagon, and leptin; unchanged cortisol and triiodothyronine (T3); and moderately increased T4. The early fall in insulin and leptin may mediate the shift to the strategy of energy conservation, protein sparing, and primary reliance on body lipids observed in response to the cessation of feeding. In contrast to the typical mammalian starvation response, nonelevated cortisol and minimal glucagon levels may contribute to body protein preservation and downregulation of catabolic pathways, in general. Furthermore, thyroid hormones may be involved in a process of energy conservation, independent of pups' nutritional state. These original hormonal settings might reflect an adaptation to the otariid repeated fasting pattern and emphasize the crucial importance of a tight physiological control over metabolism to survive extreme energetic constraints.