Showing papers by "Peter Davies published in 2010"

Global threats to human water security and river biodiversity

Abstract: Protecting the world’s freshwater resources requires diagnosing threats over a broad range of scales, from global to local. Here we present the first worldwide synthesis to jointly consider human and biodiversity perspectives on water security using a spatial framework that quantifies multiple stressors and accounts for downstream impacts. We find that nearly 80% of the world’s population is exposed to high levels of threat to water security. Massive investment in water technology enables rich nations to offset high stressor levels without remedying their underlying causes, whereas less wealthy nations remain vulnerable. A similar lack of precautionary investment jeopardizes biodiversity, with habitats associated with 65% of continental discharge classified as moderately to highly threatened. The cumulative threat framework offers a tool for prioritizing policy and management responses to this crisis, and underscores the necessity of limiting threats at their source instead of through costly remediation of symptoms in order to assure global water security for both humans and freshwater biodiversity.

Erratum: Global threats to human water security and river biodiversity

Abstract: Nature 467, 555–561 (2010) In this Article, the full present address for author P. B. McIntyre was inadvertently missing from the bottom of the page. The correct present address is: Center for Limnology, University of Wisconsin, Madison, Wisconsin 53706, USA. This has been corrected in the online PDF.

Climate Change Implications for River Restoration in Global Biodiversity Hotspots

Abstract: Global biodiversity hotspots contain exceptional concentrations of endemic species in areas of escalating habitat loss. However, most hotspots are geographically constrained and consequently vulnerable to climate change as there is limited ability for the movement of species to less hostile conditions. Predicted changes to rainfall and temperature will undoubtedly further impact on freshwater ecosystems in these hotspots. Southwestern Australia is a biodiversity hotspot and, as one of the first to experience significant climate change, is an example and potentially a global bellwether for issues associated with river restoration. In this hotspot, current and predicted water temperatures may exceed thermal tolerances of aquatic fauna. Gondwanic aquatic fauna, characteristic of southwestern Australia, are typically cold stenotherms and consequently intolerant of elevated temperatures. The hotspot in southwestern Australia is geographically restricted being surrounded by ocean and desert, and many important national parks are located on the extreme south coast, where the landscape is relatively flat. Consequently, fauna cannot change their distribution southwards or with altitude as a response to increasing temperatures. Therefore, any mitigation responses need to be in situ to produce a suitable biophysical envelope to enhance species' resilience. This could be through “over restoration” by increased riparian replanting at a catchment scale. A rule-of-thumb of a 10% increase in riparian cover would be required to reduce water temperatures by 1°C. These restoration techniques are considered applicable to other global biodiversity hotspots where geography constrains species' movement and the present condition is the desired restoration endpoint.

Fair access, achievement and geography: explaining the association between social class and students’ choice of university

Abstract: This quantitative study is concerned with what determines prospective university students’ first choice between universities of different status. The results suggest that examination performance, going to an independent school and fear of debt independently affect students’ decisions. Social factors and students’ perceived level of information on universities had no independent effect at this stage of decision‐making. There were considerable differences between two geographic areas considered in the study, with a large decrease in the probability of attending a high‐status institution in the locality with no such local institution. This particularly affects high‐achieving students, with an estimate suggesting an increased probability of 18% of going to a high‐ranking institution where such an institution is local for such students. If these findings apply similarly to other areas, the results suggest a ‘postcode lottery’ in higher education.

Improved impact performance of marine sandwich panels using through-thickness reinforcement: Experimental results

Abstract: This paper presents results from a test developed to simulate the water impact (slamming) loading of sandwich boat structures. A weighted elastomer ball is dropped from increasing heights onto rigidly supported panels until damage is detected. Results from this test indicate that honeycomb core sandwich panels, the most widely used material for racing yacht hulls, start to damage due to core crushing at impact energies around 550 J. Sandwich panels of the same areal weight and with the same carbon/epoxy facings but using a novel foam core reinforced in the thickness direction with pultruded carbon fibre pins, do not show signs of damage until above 1200 J impact energy. This suggests that these will offer significantly improved resistance to wave impact. Quasi-static test results cannot be used to predict impact resistance here as the crush strength of the pinned foam is more sensitive to loading rate than that of the honeycomb core.

Analysis of the Influence of Hydrostatic Stress on the Behaviour of an Adhesive in a Bonded Assembly

Abstract: Generally, adhesives are viscoelastic–plastic materials, for which the development of viscosity and plasticity varies depending on the type of adhesive and the stress state. Various models exist to represent the yield surface, or the so-called elastic limit, taking into account the two stress invariants, hydrostatic stress and von Mises equivalent stress. Moreover, to develop precise pressure-dependent constitutive models, it is necessary to have a large experimental database in order to accurately represent the adhesive strains which are strongly dependent on the tensile-shear loading combination. Under quasi-static loadings, for a given strain rate range viscous effects can be neglected, but only a few experimental results are available to model the behaviour of the adhesive in a bonded assembly accurately under realistic loadings. Moreover, edge effects often have a large influence on the mechanical response. This paper presents the possibility of combining the use of an experimental device, which stro...

Ophthalmoplegic migraine: the case for reclassification.

Abstract: Recurrent attacks of painful ophthalmoplegia with complete or partial recovery can usually be attributed to one of four conditions: Tolosa–Hunt syndrome, orbital myositis (orbital pseudotumour), polyneuritis cranialis (itself of heterogeneous origins) and ophthalmoplegic migraine (OM). There are specific clinical and laboratory criteria to aid the diagnosis of the first three of these. In particular, it would be extremely unusual for either of the first two conditions to resolve within weeks without corticosteroid treatment, whereas OM resolves spontaneously. OM is said to be a very rare condition, with a quoted incidence of about 0.7 per million (1), but a recent retrospective multicentre study based in France identified 52 973 adults with ‘headache associated with an oculomotor palsy firstly considered as OM’, and emphasized the heterogeneity of the semiology and the difficulty in establishing the diagnosis (2). It is more common in children than adults and attacks usually begin in childhood or even infancy. However, OM may also occur for the first time in adult life. Thomas Carlow, in his Hoyt lecture of 2002 (1), described the key features of the condition. He emphasized

Tensile fatigue behaviour of PBO fibres

Abstract: Poly(p-phenylene benzobisoxazole) (PBO) fibres are finding increasing applications on account of their exceptional stiffness and strength. This article presents results from tests on single PBO filaments, to characterize their intrinsic behaviour under quasi-static and cyclic tensile loading. Scanning electron microscopy is used to show the fibrillation mechanism leading to failure. Results are compared to data for polyester, aramid and high modulus polyethylene fibres. PBO fibres show shorter fatigue lifetimes than the other fibres when maximum stress is expressed as a percentage of quasi-static break load, but the absolute stress values applied are much higher for an equivalent lifetime.

Degradation of aramid fibers under alkaline and neutral conditions: Relations between the chemical characteristics and mechanical properties

Abstract: Aramid fibers are high-performance materials that have been used in various applications such as heat and cut protection, composites, rubber reinforcement, ropes and cables, and fabrics; today their use is proposed in geotextiles for alkaline ground reinforcement, and they have been used in cables for marine applications for a few years. However, there is a lack of experience with the long-term behavior of aramid fibers in wet and alkaline environments. Aging studies were therefore performed on Twaron 1000 fibers under different conditions (sea water, deionized water, pH 9, and pH 11). Hydrolytic degradation was evaluated with Fourier transform infrared and viscosimetry measurements, which were correlated with tensile test measurements. The tensile strength followed a logarithmic evolution with the aging time, whereas the modulus remained constant. A linear relation between the tensile strength and the reduced viscosity of the hydrolytically aged fibers is highlighted. Aging indicators are proposed that allow the hydrolytic degradation to be quantified. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Mechanical behavior of syntactic foams for deep sea thermally insulated pipeline.

Abstract: Ultra Deep offshore oil exploitation (down to 3000 meters depth) presents new challenges to offshore engineering and operating companies. Flow assurance and particularly the selection of insulation materials to be applied to pipe lines are of primary importance, and are the focus of much industry interest for deepwater applications. Polymeric and composite materials, particularly syntactic foams, are now widely used for this application, so the understanding of their behavior under extreme conditions is essential. These materials, applied as a thick coating (up to 10-15 cm), are subjected in service to: - high hydrostatic compression (up to 30 MPa) - severe thermal gradients (from 4°C at the outer surface to 150°C at the inner wall), and to high bending and shear stresses during installation. Damageable behavior of syntactic foam under service conditions has been observed previously [1] and may strongly affect the long term reliability of the system (loss of thermal properties).This study is a part of a larger project aiming to model the in-service behavior of these structures. For this purpose it is important to identify the constituent mechanical properties correctly [2, 3]. A series of tests has been developed to address this point, which includes: - hydrostatic compression - shear loading using a modified Arcan fixture This paper will describe the different test methods and present results obtained for different types of syntactic foams.

Assessing progression in students’ economic understanding: the role of threshold concepts

Abstract: This paper reports an analysis of qualitative differences between students’ understanding of flows of income in the whole economy. Previous analyses of qualitative differences in understanding of economic phenomena have been largely restricted to ‘micro’ phenomena such as price and trade. Our major interest lies in the usefulness of ‘threshold concepts’ as a way of interpreting these differences in ways of understanding. Threshold concepts (Meyer and Land 2003) have been proposed as concepts that transform and integrate previous learning with the effect that a new way of thinking is opened up. We analyse the revealed variation in conceptions of flows of income in the economy and conclude that the threshold concepts approach provides a plausible interpretation. This is important for teaching because threshold concepts potentially create considerable challenges for teachers and learners that need to be understood by both if the process of learning and teaching is to avoid slipping into create an appearance of understanding that has not been developed.

Analyse du cycle de vie d’un biocomposite

Abstract: Outre l’impact sur le changement climatique genere par l’utilisation de ressources non renouvelables pour les activites humaines [1], l’epuisement des gisements de ressources fossiles est ineluctable. Un changement de maniere de penser s’impose. Cet article presente l’analyse du cycle de vie d’un biocomposite fibres de lin/poly(L-Lactique) acide et d’un composite verre/polyester, de la fabrication en passant par la comparaison des proprietes mecaniques et la definition des epaisseurs equivalentes et sa fin de vie. L’impact environnemental global a ete evalue grâce a un outil normalise : l’Analyse de cycle de vie. Les biocomposites fibres de lin/PLLA, elabores par film stacking, presentent des proprietes en traction comparables, a masse egale, a celles des composites verre/polyester notamment en ce qui concerne la rigidite. Outre le fait d’etre compostables, les biocomposites fibres de lin/PLLA sont recyclables en fin d’usage. Enfin, l’impact du cycle de vie d’un biocomposites lin/PLLA est nettement inferieur a celui du composite verre/polyester pour les memes fonctions mecaniques. Le recyclage des biocomposites en fin d’usage permet de sequestrer la totalite du carbone present dans le materiau et d’economiser les matieres premieres. La methanisation permet une valorisation energetique par l’intermediaire de la production de biogaz et permet de sequestrer une partie du carbone inclus dans le biocomposite.

Advances in testing adhesively bonded composites

Abstract: This chapter will briefly present the current state of the art with respect to tests for composite assemblies, before describing an improved testing approach. The lap shear test is first examined in detail, through a series of results from tests on glass/epoxy and carbon/epoxy specimens. Numerical modelling is used to show the difficulties in analysing results for this specimen configuration. An original approach is then presented, based on modification of the Arcan test method. This allows the determination of adhesive failure envelopes from tests on metal substrates. The approach is then extended to composite assemblies and test results are given. The chapter concludes with a discussion of future testing requirements.

Developments in mapping of seabed habitats for Marine Protected Area planning and monitoring

Abstract: To date a total area of approximately 275 km2 of continental shelf waters within the Solitary Islands Marine Park and adjacent waters has been swath mapped. This data, combined with maps of shallow reefs digitised from aerial photos, underwater video surveys and Geographical Information System (GIS) analysis is used to create a number of spatial products such as digital elevation models (with analysis of slope and rugosity), vector based seabed habitat maps and spatially-linked data on macro-benthic floral and faunal assemblages.

Migraine with atypical visual aura caused by colloid cyst of the third ventricle

Abstract: There are many case reports of structural brain lesions that appear to cause or provoke headaches that are clinically indistinguishable from primary headache syndromes. ‘Symptomatic migraine’ is the term used under the second edition of the International Classification of Headache Disorders (ICHD-II) to describe such cases, which mimic migraine. However, symptomatic migraine with visual aura (MA) is rare. It has been reported most often in association with parieto-occipital arteriovenous malformations and rarely with cerebral venous thrombosis, extracranial artery dissection and cerebral metastases (1). Migrainous visual aura is believed to be caused by cortical spreading depression (CSD) generated in the visual cortex, and in ‘symptomatic’ cases the anatomical relationship of the lesion to this brain region is presumed to explain the aura. However, we report here the rapid evolution of MA in a patient who proved to have a colloid cyst of the third ventricle, an area remote from the visual cortex. There was no previous or family history of migraine and the MA symptoms resolved immediately and completely following removal of the cyst. On review more than a year later, the patient had experienced no further headache or aura, suggesting that the colloid cyst had provoked the syndrome.

Recruitment and growth of two small‐bodied resident fish species (Gobiidae and Atherinidae) in oligohaline, seasonally open lagoons

Abstract: Spatio-temporal recruitment patterns, growth and survival of the Swan River goby Pseudogobius olorum and western hardyhead Leptatherina wallacei are described from two small, coastal lagoons on the south coast of Western Australia. In these lagoons, estuarine salinity dynamics were relatively stable over much of the autumn–spring period when freshwater inputs from rivers were reduced and there was no oceanic connection. Preflexion and flexion stages of both fish species contributed strongly to population size structure in downstream reaches, whereas upstream reaches were dominated by postflexion larvae and juvenile stages. Spawning of both species was protracted and largely asynchronous, although the episodic presence of stronger preflexion and flexion cohorts suggested some synchronized spawning had occurred. Comparison with estuarine conditions over this period provided evidence that synchronized spawning may be related to temperature and salinity variations from a combination of freshwater inputs and periods of marine exchange. Uninterrupted growth and the progression of cohorts through to juvenile stages were consistent with the generally stable estuarine conditions. Larval and juvenile stages of both species were also tolerant of abrupt changes in salinity and temperature, which occurred due to a non-seasonal oceanic connection. These findings were consistent with the euryhaline nature of adults of both species.

An immanent social class effect on participation in higher education? A rejoinder to Harrison and Waller

Abstract: This article responds to criticisms, put forward by Harrison and Waller in this issue, of an earlier paper by Noble and Davies. In particular, we argue that our interpretation of earlier quantitative research is correct, that Harrison and Waller have misconstrued the purpose of our previous paper and the analysis it contains, and that they (mis‐)attribute to us a series of propositions and standpoints that are not in our paper. In the light of increasing policy interest in the extent to which providing information can lead to ‘more well‐informed choices’ about participation in higher education, we remain of the view that researching the role of cultural capital in the students’ immanent choices is a matter of considerable importance.

Wave impact resistance of racing yacht composites

Abstract: Repeated wave impact is a critical loading condition for racing yacht design. A test that was initially used to compare materials has been further developed to provide quantitative results and input for numerical modelling.