Direct Measurement of Transformation Zone Strains in Toughened Zirconia

Residual strains responsible for crack tip shielding have been measured within transformation zones surrounding cracks in Mg-PSZ. Two techniques were used for strain measurement: moiré interferometry and high-resolution image matching. Both methods provide maps of differential in-plane displacements within the specimen surface intersected by the crack, the latter method with the higher resolution. The results are compared with finite-element analysis to assess surface relaxation effects, and the measured strains are used to evaluate the crack tip shielding stress intensity factor. Calculations based on the assumption that the unconstrained transformation strain is hydrostatic dilatation yielded results that were significantly smaller than the measured toughness increases.     

Analysis and simulation of the grinding process. Part II: Mechanics of grinding

This paper is the second of three parts which describe the analysis and simulation of the grinding process. Generation of the workpiece surface depends on the interactions between the grains of the wheel and the workpiece. The grinding wheel surface generated by dressing was simulated by the method described in Part I. This part describes a method to investigate the process of grinding by simulating the cutting action of every grain which engages with the workpiece. Grinding forces are analysed by simulating the force on each grain which passes a section of the workpiece. The simulated workpiece surface shows features which are similar in nature to the experimental results. A more extensive comparison of simulated and experimental grinding behaviour is presented in Part III.     

Two computational regimes of a single-compartment neuron separated by a planar boundary in conductance space

Recent in vitro data show that neurons respond to input variance with varying sensitivities. Here we demonstrate that Hodgkin-Huxley (HH) neurons can operate in two computational regimes: one that is more sensitive to input variance (differentiating) and one that is less sensitive (integrating). A boundary plane in the 3D conductance space separates these two regimes. For a reduced HH model, this plane can be derived analytically from the V nullcline, thus suggesting a means of relating biophysical parameters to neural computation by analyzing the neuron's dynamical system.     

Addressing agent loss in vehicle formations and sensor networks

In this paper, we address the problem of agent loss in vehicle formations and sensor networks via two separate approaches: (1) perform a ‘self‐repair’ operation in the event of agent loss to recover desirable information architecture properties or (2) introduce robustness into the information architecture a priori such that agent loss does not destroy desirable properties. We model the information architecture as a graph G(V, E), where V is a set of vertices representing the agents and E is a set of edges representing information flow amongst the agents. We focus on two properties of the graph called rigidity and global rigidity, which are required for formation shape maintenance and sensor network self‐localization, respectively. For the self‐repair approach, we show that while previous results permit local repair involving only neighbours of the lost agent, the repair cannot always be implemented using only local information. We present new results that can be applied to make the local repair using only local information. We describe implementation and illustrate with algorithms and examples. For the robustness approach, we investigate the structure of graphs with the property that rigidity or global rigidity is preserved after removing any single vertex (we call the property as 2‐vertex‐rigidity or 2‐vertex‐global‐rigidity, respectively). Information architectures with such properties would allow formation shape maintenance or self‐localization to be performed even in the event of agent failure. We review a characterization of a class of 2‐vertex‐rigidity and develop a separate class, making significant strides towards a complete characterization. We also present a characterization of a class of 2‐vertex‐global‐rigidity. Copyright © 2008 John Wiley & Sons, Ltd.     

Oral health assessment in dogs: study design and results

The authors have conducted a large number of canine dental studies during the past six years. Study methodologies have been driven by the need for statistical validation of results, requiring the participation of large numbers of animals in each study. For plaque, stain, and calculus evaluations, a "clean tooth" model was used, in which formation of these substrates was assessed days to weeks after an initial coronal cleaning. A primary goal of the studies described was to validate the study designs used--that is, to use accepted plaque-, calculus-, and stain-controlling agents to test whether the study methods could detect differences between treated and untreated groups. The results of clinical studies show that the methods described can be used to identify plaque, calculus, and stain control attributable to chemical agents, oral hygiene aids, and consumable products.     

Surface energy-mediated fibronectin adsorption and osteoblast responses on nanostructured diamond

Nanostructured diamond have potential applications in many biomedical related fields and demonstrated extraordinary capacity to influence cellular responses. Studying the surface property of nanodiamond and its influence to protein adsorption and subsequent cellular responses along with the mechanism behind such capacity becomes more important. Here the role of surface energy associated with nanostructured diamond in modulating fibronectin and osteoblast(OB, bone forming cells) responses was investigated. Nanocrystalline diamond(NCD) and submicron crystalline diamond(SMCD) films with controllable surface energy were prepared by microwave-enhanced plasma chemical vapor deposition(MPCVD) techniques. Fibronectin adsorption on the diamond films with varied surface energy values was measured via the enzyme-linked immunosorbent assay(ELISA) and the relationship between the surface energy and fibronectin adsorption was studied. The result indicated that fibronectin adsorption on nanostructured surfaces was closely related to both surface energy and material microstructures. The spreading and migration of OB aggregates(each containing 30–50 cells) on the NCD with varied surface energy values were also studied. The result indicates a correlation between the cell spreading and migration on nanodiamond and the surface energy of nanostructured surface.     

Quantitation by radioimmunoassay of PAF in human saliva

Approximately 75% of the PAF present in saliva is recovered on extraction of whole saliva (0.8 vol) with chloroform/methanol/water (2∶2∶1 v/v/v). PAF levels, determined by our recently developed radioimmunoassay, in saliva extracts ranged from 0.5–21 ng/mL with 59% between 2–6 ng/mL. These figures, for apparently healthy subjects, are higher than previously reported levels obtained by platelet assays. The validity of our radioimmunoassay results was checked by isolating and quantitating the PAF fraction from whole saliva. In addition, when we examined our saliva samples by platelet aggregation, low levels of PAF, comparable with the values found in the literature, were detected. Investigations revealed the presence of a substance(s) which inhibited PAF-induced platelet aggregation but which did not affect the radioimmunoassay.