Recent advances in biodegradable nanocomposites

There is growing interest in developing bio-based products and innovative process technologies that can reduce the dependence on fossil fuel and move to a sustainable materials basis. Biodegradable bio-based nanocomposites are the next generation of materials for the future. Renewable resource-based biodegradable polymers including cellulosic plastic (plastic made from wood), corn-derived plastics, and polyhydroxyalkanoates (plastics made from bacterial sources) are some of the potential biopolymers which, in combination with nanoclay reinforcement, can produce nanocomposites for a variety of applications. Nanocomposites of this category are expected to possess improved strength and stiffness with little sacrifice of toughness, reduced gas/water vapor permeability, a lower coefficient of thermal expansion, and an increased heat deflection temperature, opening an opportunity for the use of new, high performance, lightweight green nanocomposite materials to replace conventional petroleum-based composites. The present review addresses this green material, including its technical difficulties and their solutions

The implicit benefit of learning without errors

Two studies examined whether the number of errors made in learning a motor skill, golf putting, differentially influences the adoption of a selective (explicit) or unselective (implicit) learning mode. Errorful learners were expected to adopt an explicit, hypothesis-testing strategy to correct errors during learning, thereby accruing a pool of verbalizable rules and exhibiting performance breakdown under dual-task conditions, characteristic of a selective mode of learning. Reducing errors during learning was predicted to minimize the involvement of explicit hypothesis testing leading to the adoption of an unselective mode of learning, distinguished by few verbalizable rules and robust performance under secondary task loading. Both studies supported these predictions. The golf putting performance of errorless learners in both studies was unaffected by the imposition of a secondary task load, whereas the performance of errorful learners deteriorated. Reducing errors during learning limited the number of error-correcting hypotheses tested by the learner, thereby reducing the contribution of explicit processing to skill acquisition. It was concluded that the reduction of errors during learning encourages the use of implicit, unselective learning processes, which confer insusceptibility to performance breakdown under distraction.link_to_subscribed_fulltex

Cosmological particle production and causal thermodynamics

The full linear causal Israel-Stewart-Hiscock theory of bulk viscous processes in relativistic cosmological fluids is reformulated as an effective phenomenological theory for describing particle production processes in the early universe. Explicit expressions for the particle balance law and particle production rates are obtained that relate the particle creation rate to the bulk viscous (creation) pressure. The general formalism is applied to the case of a full causal cosmological fluid with bulk viscosity coefficient proportional to the Hubble function. In this case the general solution of the gravitational field equations can be expressed in an exact parametric form. For an appropriate choice of the physical parameters, the dynamics of the universe can be modelled as starting from a vacuum quasi-Minkowskian geometry, followed by an inflationary period but ending in a non-inflationary phase. The influence of the matter creation processes on the evolution of the universe and the behaviour of the energy density, temperature and entropy are investigated. © CSIRO 1999.link_to_subscribed_fulltex

Effect of surface treatment on mode I interlaminar fracture behaviour of plain glass woven fabric composites: Part I. Report of the 2nd round-robin test results

A round-robin test programme has been carried out to characterise the mode I interlaminar fracture behaviour of E-glass woven fabric reinforced vinyl ester matrix composites. Special emphasis has been placed on the effect of silane coupling agent on the stability of interlaminar crack propagation and fracture toughness. Sixteen laboratories participated in this programme. Each laboratory was supplied with composite laminates of thicknesses of its own choice and conducted-the tests according to its own procedures. The results showed that variations in interlaminar fracture toughness between laboratories were very large in spite of slight differences in the test procedures used, such as specimen dimensions, test speed and data reduction schemes. Nevertheless, the general trends were clearly identified with respect to different silane coupling agents. Other observations and the implications are discussed