Interfacial energy states of moisture-exposed cracks in mica

Results of crack growth observations on mica in water-containing environments are described. The study focuses on equilibrium crack states for reversed loading cycles, i.e., for initial propagation through virgin solid and subsequent retraction-repropagation through healed or misoriented-healed interfaces. Departures from these equilibrium states are manifest as steady-state forward or backward crack velocities at specific applied loads. The equilibria are thereby interpreted as quiescent, threshold configurations G = W_E, with G the Griffith mechanical-energy-release rate and W_E the Dupré work of adhesion, on crack velocity (v-G) diagrams. Generally, W_E is found to decrease with concentration of water, in accordance with a Gibbs formalism. Hysteresis is observed in the forward-backward-forward crack propagation cycle, signifying a reduction in the adhesion energy on exposure of the open interface to environmental species prior to healing. This hysteresis is especially marked for those interfaces that are misoriented before healing, indicating that the structure of the underlying solid substrate as well as of the intervening fluid is an important consideration in the interface energetics. The equilibrium states for different environments can be represented on a simple energy-level diagram, as differences between thermodynamic end-point states: initial, closed-interface states refer to crystallographic bonding configurations ahead of the crack-tip adhesion zone; final, open interface states refer to configurations behind the crack-tip zone. The significance of this diagram in relation to the fundamental atomic structure of interfaces in fracture and other adhesion geometries, including implications concerning kinetics, is discussed.

Available energy

A proposed new statement of the second law of thermodynamics - the transformation of energy to work is always inefficient with respect to available energy - is conceptually and pedagogically simpler than historical entropy-based statements. It has assisted in the discovery of a new general characterisation of steady (energy dissipative) states.

Progress on building energy labelling techniques

The building sector consumes around 30–40 per cent of the primary energy in most developed countries. The importance of labelling buildings as a national strategy for energy efficiency is well recognized worldwide. The last 10–15 years have seen an emergence of programmes in different parts of the world. As seen in the United States, European Union, South America and Asia, there is a collection of rating systems or tools internationally, designed with the intention of evaluating the design, construction and operation of buildings. This study presents an overview and critical reflection on the progress on building energy labelling techniques in recent years. The scope of labelling, methodology and methods of implementation are discussed in detail.

Energy consumption at the state level: the unit root null hypothesis from Australia

In this paper, our goal is to examine the unit root null hypothesis in energy consumption for Australian states and territory. We consider sectoral energy consumption for Australia and its six states and one territory using time series data for the period 1973-2007. This is the first study that does this. Generally, except for some cases in South Australia, we find strong support that shocks to energy consumption have a temporary effect on energy consumption in Australia. © 2009 Elsevier Ltd. All rights reserved.

Relationship between processing, surface energy and bulk properties of ultrafine silk particles

Silk particles of different sizes and shapes were produced by milling and interactions with a series of polar and non-polar gaseous probes were investigated using an inverse gas chromatography technique. The surface energy of all silk materials is mostly determined by long range dispersive interactions such as van der Waals forces. The surface energy increases and surface energy heterogeneity widens after milling. All samples have amphoteric surfaces and the concentration of acidic groups increases after milling while the surfaces remain predominantly basic. We also examined powder compression and flow behaviours using a rheometer. Increase in surface energy, surface area, and static charges in sub-micron air jet milled particles contributed to their aggregation and therefore improved flowability. However they collapse under large pressures and form highly cohesive powder. Alkaline hydrolysis resulted in more crystalline fibres which on milling produced particles with higher density, lower surface energy and improved flowability. The compressibility, bulk density and cohesion of the powders depend on the surface energy as well as on particle size, surface area, aggregation state and the testing conditions, notably the consolidated and unconsolidated states. The study has helped in understanding how surface energy and flowability of particles can be changed via different fabrication approaches.

Exposure mediates transitions between bare and vegetated states in temperate mangrove ecosystems

The resilience of mangroves is dependent on their regeneration capacity. Patchy mid-19th century clearing dramatically affected this capacity, creating stable vegetated and unvegetated states in a fragmented temperate mangrove ecosystem. Mechanisms of mediation between states were tested by monitoring the survival and growth of planted mangrove seedlings and propagules on formerly forested bare mudflats and inside patches of existing forest. Survival (1 to 76%) and growth (-0.83 to 10.45 mm mo-1 increase in plant height) of seedlings was affected by (1) differing levels of exposure found at varying proximities to remnant forest and (2) differing inundation regimes both within and between sites that were randomly selected from locations that varied in aspect relative to prevailing winds. Increases in hydrodynamic energy within and between sites corresponded to a decrease in survival that was much more pronounced at locations that were exposed to prevailing winds. Growth rates were also generally lower at sites in exposed locations, but inundation regime was a more important determinant within sites, where growth was reduced at lower heights on the shore. Results suggest that stability of the bare mudflat state (caused by historical clearance of the mangrove forest) is dependent on level of exposure to hydrodynamic energy, and a return to a forested state is more likely where this exposure is lower. These results have implications for planning and implementing mangrove restoration projects and illustrate the role that physical factors can play in determining the resilience of disturbed temperate mangrove ecosystems.

Considering the chemical energy requirements of the tri-n-propylamine co-reactant pathways for the judicious design of new electrogenerated chemiluminescence detection systems

The introduction of a 'co-reactant' was a critical step in the evolution of electrogenerated chemiluminescence (ECL) from a laboratory curiosity to a widely utilised detection system. In conjunction with a suitable electrochemiluminophore, the co-reactant enables generation of both the oxidised and reduced precursors to the emitting species at a single electrode potential, under the aqueous conditions required for most analytical applications. The most commonly used co-reactant is tri-n-propylamine (TPrA), which was developed for the classic tris(2,2'-bipyridine)ruthenium(ii) ECL reagent. New electrochemiluminophores such as cyclometalated iridium(iii) complexes are also evaluated with this co-reactant. However, attaining the excited states in these systems can require much greater energy than that of tris(2,2'-bipyridine)ruthenium(ii), which has implications for the co-reactant reaction pathways. In this tutorial review, we describe a simple graphical approach to characterise the energetically feasible ECL pathways with TPrA, as a useful tool for the development of new ECL detection systems.

Energy productivity and total-factor productivity in the Australian construction industry

There is urgent need to consider energy consumption when measuring total-factor productivity in the construction industry. This paper adopts the Malmquist index method to investigate the factors affecting the energy productivity of the Australian construction industry and compares them with those decomposed from the total-factor productivity. An input-oriented distance function and a contemporaneous benchmark technology are employed to develop the data envelopment analysis models. The Malmquist productivity index is decomposed into the technological change, pure technical efficiency change and activity effect to gain comprehensive insights into changes of construction productivity in the Australian states and territories over the past two decades. Research results show that both energy productivity and total-factor productivity improved in Australia, particularly related to technological development. The pure technical efficiency and activity indices changed slightly over time or across regions. This study demonstrates that there exists a linkage between energy productivity and total-factor productivity through their technological and technical efficiency changes. The Australian construction industry could enhance these two productivities by introducing advanced technologies and implementing them efficiently.