Discrepancy between sub-critical and fast rupture roughness: a cumulant analysis

We study the roughness of a crack interface in a sheet of paper. We distinguish between slow (sub-critical) and fast crack growth regimes. We show that the fracture roughness is different in the two regimes using a new method based on a multifractal formalism recently developed in the turbulence literature. Deviations from monofractality also appear to be different in both regimes

ECOSYSTEM APPROACH TO FISHERIES MANAGEMENT IN THE NORTHERN BENGUELA: THE NAMIBIAN EXPERIENCE

The northern Benguela marine resources have a long history of questionable management primarily because of the limitations of management measures under the political framework of the time (either free access or under an international authority with no national representation, authority or enforcement power). Only after its Independence in 1990 could Namibia exercise its own national management policies, but by that time the most important commercial stocks were severely depleted. Since Independence, and despite strong management measures being implemented, the recovery of the stocks has not been as successful as expected. Some of the possible reasons are the effect of environmental variability on some stocks, ecosystem effects of fishing and unforeseen trophic interaction effects. To date, fisheries management has been based largely on a single-stock approach, but Namibia is committed to implement, in addition, an ecosystem approach to fisheries (EAF) management. The work leading to this implementation is described, in particular an ecosystem modelling study undertaken to summarize the current understanding of the northern Benguela ecosystem, to provide a basis for future work towards an EAF in Namibia. Model simulation results suggest that, given the present assumed trophic structure of the northern Benguela, altering the major fisheries would not result in recovery of the small pelagics to levels seen 40 years ago, suggesting that the original foodweb in the region may have been altered dramatically. Cape hake Merluccius capensis and M. paradoxus were negatively impacted when a large fishery on small horse mackerel Trachurus trachurus capensis was simulated. Model simulations illustrate the important finding that ecosystem effects of altered fishing scenarios are often not of a magnitude or direction that would be expected by considering predator-prey relationships in the absence of indirect trophic effects. Trophic effects may have large indirect consequences for some components of the system, for example seabirds.Afr. J. mar. Sci. 26: 79–9

Numbers do not tell the whole story: gender and medicine in Portugal

Despite a progressive increase in the number of women in medicine, gender inequalities remain. This article presents a study analyzing the gender dynamics of tokenism in the medical field in Portugal, through the experiences of male specialists in female areas and female specialists in male areas and through their strategies for coping with such situations. We conducted individual, semi-structured interviews with nine female doctors and eight male doctors aged between 32 and 62 years old. Results show the links between tokenism dynamics and gender asymmetry in medicine, putting female tokens at a disadvantage in relation to male tokens. Token positions occasionally produce gender arrangements but, all things considered, do not transform female and male positions either in the medical field or in the private sphere. We conclude that tokenism contributes to maintaining the gender social order.info:eu-repo/semantics/acceptedVersio

Equilibrium onions?

We demonstrate the possibility of a stable equilibrium multi-lamellar ("onion") phase in pure lamellar systems (no excess solvent) due to a sufficiently negative Gaussian curvature modulus. The onion phase is stabilized by non-linear elastic moduli coupled to a polydisperse size distribution (Apollonian packing) to allow space-filling without appreciable elastic distortion. This model is compared to experiments on copolymer-decorated lamellar surfactant systems, with reasonable qualitative agreement

A rapid method for the in-field analysis of amphetamines employing the agilent bioanalyzer

This paper reports the first analysis of small molecules on the Agilent bio-analyser. The Bioanalyzer is a commercial lab-on-a-chip instrument designed for the analysis of DNA and proteins. We demonstrate that the instrument is suitable for analyses beyond its design specifications. Amphetamine, methamphetamine and pseudoephedrine were separated with a 50 mM borate and 50 mM sodium dodecyl sulfate (SDS) buffer at pH 9.66. The analytes were derivatised with fluorescein isothiocyanate (FITC) in 3 minutes with a heating block set at 90°C, reducing the typical time of 12 hours required for amine-labelling. Analytes were detected by LED-induced fluorescence (λ = 525 nm and λ = 470 nm). Furthermore, five amphetamine analogues were baseline separated within 1 minute. An average limit of detection of 0.6 mg mL -1 and limit of quantification of 2.2μ mg mL-1 were obtained for all analytes. These rapid analyses in conjunction with a fast and reliable derivatisation method with FITC demonstrate its potential use for the in-field analysis of samples of forensic significance. © 2011 The Royal Society of Chemistry

Using LES to Study Reacting Flows and Instabilities in Annular Combustion Chambers

Great prominence is put on the design of aeronautical gas turbines due to increasingly stringent regulations and the need to tackle rising fuel prices. This drive towards innovation has resulted sometimes in new concepts being prone to combustion instabilities. In the particular field of annular combustion chambers, these instabilities often take the form of azimuthal modes. To predict these modes, one must compute the full combustion chamber, which remained out of reach until very recently and the development of massively parallel computers. Since one of the most limiting factors in performing Large Eddy Simulation (LES) of real combustors is estimating the adequate grid, the effects of mesh resolution are investigated by computing full annular LES of a realistic helicopter combustion chamber on three grids, respectively made of 38, 93 and 336 million elements. Results are compared in terms of mean and fluctuating fields. LES captures self-established azimuthal modes. The presence and structure of the modes is discussed. This study therefore highlights the potential of LES for studying combustion instabilities in annular gas turbine combustors

A portable explosive detector based on fluorescence quenching of pyrene deposited on coloured wax-printed μpADs

A new technique for the detection of explosives has been developed based on fluorescence quenching of pyrene on paper-based analytical devices (μPADs). Wax barriers were generated (150 °C, 5 min) using ten different colours. Magenta was found as the most suitable wax colour for the generation of the hydrophobic barriers with a nominal width of 120 μm resulting in fully functioning hydrophobic barriers. One microliter of 0.5 mg mL-1 pyrene dissolved in an 80 : 20 methanol-water solution was deposited on the hydrophobic circle (5 mm diameter) to produce the active microchip device. Under ultra-violet (UV) illumination, ten different organic explosives were detected using the μPAD, with limits of detection ranging from 100-600 ppm. A prototype of a portable battery operated instrument using a 3 W power UV light-emitting-diode (LED) (365 nm) and a photodiode sensor was also built and evaluated for the successful automatic detection of explosives and potential application for field-based screening. © 2013 The Royal Society of Chemistry