Assessing the Accuracy of Soot Nanoparticle Morphology Measurements Using Three- Dimensional Electron Tomography

Morphology plays an important role in determining behaviour and impact of soot nanoparticles, including effect on human health, atmospheric optical properties, contribution to engine wear, and role in marine ecology. However, its nanoscopic size has limited the ability to directly measure useful morphological parameters such as surface area and effective volume. Recently, 3D morphology characterization of soot nanoparticles via electron tomography has been the subject of several introductory studies. So-called '3D-TEM' has been posited as an improvement over traditional 2D-TEM characterization due to the elimination of the error-inducing information gap that exists between 3-dimensional soot structures and 2-dimensional TEM projections. Little follow-up work has been performed due to difficulties with developing methodologies into robust high-throughput techniques. Recent work by the authors has exhibited significant improvements in efficiency, though as yet due consideration has not been given to assessing fidelity of the technique. This is vital to confirm significant and tangible improvements in soot-characterization accuracy that will establish 3D-TEM as a legitimate tool. Synthetic ground-truth data was developed to closely mimic real soot structures and the 3D-TEM volume-reconstruction process. A variety of procedures were tested to assess the magnitude and nuances of deviations from ground-truth values. Results showed average Z-elongation due to the 'missing-wedge' at 3.5% for the previously developed optimized procedure. Mean deviations from ground-truth in volume and surface area were 2.0% and-0.1% respectively. Results indicate highly accurate 3D-reconstruction can be achieved with an optimized procedure that can bridge the gap to permit high-throughput 3D morphology characterization of soot

Why Are Male Social Relationships Complex in the Doubtful Sound Bottlenose Dolphin Population?

Copyright 2008 Elsevier B.V., All rights reserved.Peer reviewedPublisher PD

Investigation of Exhaust Particles on Different TEM Grids: A Comparison between Graphene Oxide and Silicon Nitride Grids

Two different TEM (Transmission Electron Microscopy) grids - graphene oxide (GO) and silicon nitride (SiN) - were used to capture the particulates emitted with the exhaust of a modern 1.0 L GDI (Gasoline Direct Injection) engine. One speed-load condition (1250 rpm - idle) was chosen to generate a nanometric particulate output in the sub-23 nm regime which has been traditionally difficult to analyse in terms of composition and morphology. The overall aim was to understand if additional benefits can be obtained by analysing the particles captured in the exhaust on a nanoporous silicon nitride grid compared to state-of- the-art graphene oxide grids. The behaviour of porous SiN support films was of interest since nanopores are present in the grid in the 20 nm regime and the material is thermally and dimensionally stable under high temperatures, allowing thermophoretic capture directly within the engine exhaust stream. In addition to nanostructural and morphological comparison, the elemental composition of the particles was also analysed by EDX (Energy Dispersive X-Ray). Particles were thermophoretically captured directly in the exhaust stream using a dedicated probe holding the grid. Because of their tiny 2 nm thickness, GO grids work well for studying particle nanostructure, however background noise from copper and carbon interferes with compositional analysis by EDX. In contrast, the silicon nitride grids enable particle observation without this background noise, providing an intriguing platform for the analysis of the suspended particles collected by the pores. Future research will concentrate on producing particles with graphitic areas to assess imaging advantages in terms of morphological and nanostructural examination. The two grids were similar in their particle capture within the engine, with close mean primary particle diameters using both: 13.5 ± 3.1 nm standard deviation (SD) on GO and 14.1 ± 2.6 nm SD on SiN. EDX analysis suggests SiN grids, as C-free substrates, are preferable to GO for determining the carbon load in captured particles. This investigation is part of a larger project focusing on decarbonised fuels, so a carbon-free support film is pivotal in understanding the nature and composition of the fine particles linked to the lubricant oil

Evolutionary Games with Affine Fitness Functions: Applications to Cancer

We analyze the dynamics of evolutionary games in which fitness is defined as an affine function of the expected payoff and a constant contribution. The resulting inhomogeneous replicator equation has an homogeneous equivalent with modified payoffs. The affine terms also influence the stochastic dynamics of a two-strategy Moran model of a finite population. We then apply the affine fitness function in a model for tumor-normal cell interactions to determine which are the most successful tumor strategies. In order to analyze the dynamics of concurrent strategies within a tumor population, we extend the model to a three-strategy game involving distinct tumor cell types as well as normal cells. In this model, interaction with normal cells, in combination with an increased constant fitness, is the most effective way of establishing a population of tumor cells in normal tissue.Comment: The final publication is available at http://www.springerlink.com, http://dx.doi.org/10.1007/s13235-011-0029-

Analytical model for residual bond strength of corroded reinforcement in concrete structures

Bond strength deterioration in corrosion-damaged reinforced concrete structures significantly affects serviceability and load-carrying capacity in their remaining service life. This paper presents a new analytical model for predicting the cracking development in the surrounding concrete and the residual bond strength of rebar in concrete structures due to reinforcement corrosion. The proposed analytical method adopts the thick-walled cylinder model for the cover concrete and considers the realistic properties of the corrosion-induced cracked concrete such as anisotropic behavior, residual tensile strength, and reduced tensile stiffness. As corrosion progresses, three phases for bond strength evolution associated with concrete cracking development are defined and the corresponding corrosion levels in each phase are determined. By using the constructed new governing equation, the crack width growth in the concrete cover and the radial bursting pressure at the bond interface are evaluated. The ultimate bond strength is then estimated from the contributions of adhesion, confinement, and corrosion pressure as a function of corrosion level. Finally, the effectiveness of the proposed analytical model is demonstrated by comparing the predicted results with experimental data available, and the results show that the proposed model is useful for predicting the bond strength evolution of the corroded rebar in concrete structures

Do Harmonised Accounting Standards Lead to Harmonised

The objective of this paper is to investigate the level of harmonisation for IAS 39 Financial Instruments: Recognition and Measurement and to identify if different levels of harmonisation are associated with company-specific factors. Based on Rahman et al. (2002), we used the Jaccard (JACC) index to determine the level of harmonisation between IAS 39 and the financial reporting practice of a broad-based sample of European-listed companies in 2005.We applied regression analysis to identify companies’ specific characteristics that affect the level of convergence of the reporting practice of financial instruments. The results of this study show a high level of harmonisation between accounting practices of European companies included in our sample and IAS 39

Recovery of thicket in a revegetated limestone mine

The opencast extraction of limestone at the PPC Cement (Pty) Ltd Loerie quarry in the Eastern Cape, South Africa, has led to disturbance of the immediate environment. Large tracts of thicket have been removed during mining and exhausted quarry areas had to be revegetated. Revegetation commenced 16 years ago and as a result of progressive revegetation efforts since then, five seral stages were available for study. This presented an opportunity to describe the successional progression that occurs where thicket topsoil was used for revegetation. The quarry lies near the Gamtoos fault and both thicket and mountain fynbos is found in proximity to the mine. Before mining, the area was covered by thicket and quarry floors were revegetated by covering landscaped areas with thicket topsoil. The vegetation that developed in the quarry had a very low floristic relationship to fynbos. After 16 years, the vegetation also had a low similarity to thicket, even though the soils used for revegetation contained thicket propagules. The oldest seral stage (16years) was a Rhus incisa-Panicum deustum thicket in which only 46% of the species were mature thicket species. In order to develop thicket more rapidly, active intervention will be required. This could take the form of planting of saplings of key thicket species. A trial planting of such saplings showed high survival success of most species. Long-term (50year) monitoring will be required to determine whether this approach was successful

The influence of alkalosis on repeated high-intensity exercise performance and acid–base balance recovery in acute moderate hypoxic conditions

Purpose Exacerbated hydrogen cation (H⁺) production is suggested to be a key determinant of fatigue in acute hypoxic conditions. This study, therefore, investigated the effects of NaHCO3 ingestion on repeated 4 km TT cycling performance and post-exercise acid–base balance recovery in acute moderate hypoxic conditions. Methods Ten male trained cyclists completed four repeats of 2 × 4 km cycling time trials (TT1 and TT2) with 40 min passive recovery, each on different days. Each TT series was preceded by supplementation of one of the 0.2 g kg⁻¹ BM NaHCO3 (SBC2), 0.3 g kg⁻¹ BM NaHCO3 (SBC3), or a taste-matched placebo (0.07 g kg⁻¹ BM sodium chloride; PLA), administered in a randomized order. Supplements were administered at a pre-determined individual time to peak capillary blood bicarbonate concentration ([HCO3⁻]). Each TT series was also completed in a normobaric hypoxic chamber set at 14.5% FiO2 (~ 3000 m). Results Performance was improved following SBC3 in both TT1 (400.2 ± 24.1 vs. 405.9 ± 26.0 s; p = 0.03) and TT2 (407.2 ± 29.2 vs. 413.2 ± 30.8 s; p = 0.01) compared to PLA, displaying a very likely benefit in each bout. Compared to SBC2, a likely and possible benefit was also observed following SBC3 in TT1 (402.3 ± 26.5 s; p = 0.15) and TT2 (410.3 ± 30.8 s; p = 0.44), respectively. One participant displayed an ergolytic effect following SBC3, likely because of severe gastrointestinal discomfort, as SBC2 still provided ergogenic effects. Conclusion NaHCO3 ingestion improves repeated exercise performance in acute hypoxic conditions, although the optimal dose is likely to be 0.3 g kg⁻¹ BM