Fourier basis for the engineering assessment of cracks in residual stress fields

A theoretical basis is presented for determining the significance of a residual stress distribution of arbitrary shape on the crack tip stress intensity factor for a centre-cracked plate as a function of crack length. The Fourier series based approach enables one to increasingly add more spatial definition to the stress field and thereby determine the level of detailed knowledge of the residual stress required to make a reliable assessment of structural integrity. The approach is applied to examples of measured symmetric distributions of residual stresses in welded plates and used to determine the significance of residual stress lengthscales in fracture mechanics analysis

The architecture of cancellous bone in the hindlimb of moa (Aves: Dinornithiformes), with implications for stance and gait

The extinct, flightless moa of New Zealand included some of the largest birds to have existed and possessed many distinguishing pelvic and hindlimb osteological features. These features may have influenced stance and gait in moa compared with extant birds. One means of assessing locomotor biomechanics, particularly for extinct species, is quantitative analysis of the architecture of cancellous bone, since this architecture is adapted to suit its mechanical environment with high sensitivity. This study investigated the three-dimensional architecture of cancellous bone in the femur, tibiotarsus and fibula of three moa species: Dinornis robustus, Pachyornis elephantopus and Megalapteryx didinus. Using computed tomographic X-ray scanning and previously developed fabric analysis techniques, the spatial variation in cancellous bone fabric patterns in moa was found to be largely comparable with that previously reported for extant birds, particularly large species. Moa hence likely used postures and kinematics similar to those employed by large extant bird species, but this interpretation is tentative on account of relatively small sample sizes. A point of major difference between moa and extant birds concerns the diaphyses; cancellous bone invades the medullary cavity in both groups, but the invasion is far more extensive in moa. Combined with previous assessments of cortical geometry, this further paints a picture of at least some moa species possessing very robust limb bones, for which a convincing explanation remains to be determine

Lifestyle guidelines for managing adverse effects on bone health and body composition in men treated with androgen deprivation therapy for prostate cancer: an update

BACKGROUND: Men treated with androgen deprivation therapy (ADT) for prostate cancer are prone to multiple treatment-induced adverse effects, particularly with regard to a deterioration in bone health and altered body composition including decreased lean tissue mass and increased fat mass. These alterations may partially explain the marked increased risk in osteoporosis, falls, fracture and cardiometabolic risk that has been observed in this population. METHODS: A review was conducted that assessed standard clinical guidelines for the management of ADT-induced adverse effects on bone health and body composition in men with prostate cancer. RESULTS: Currently, standard clinical guidelines exist for the management of various bone and metabolic ADT-induced adverse effects in men with prostate cancer. However, an evaluation of the effectiveness of these guidelines into routine practice revealed that men continued to experience increased central adiposity, and, unless pharmacotherapy was instituted, accelerated bone loss and worsening glycaemia occurred. CONCLUSIONS: This review discusses the current guidelines and some of the limitations, and proposes new recommendations based on emerging evidence regarding the efficacy of lifestyle interventions, particularly with regard to exercise and nutritional factors, to manage ADT-related adverse effects on bone health and body composition in men with prostate cancer

Microbial use of low molecular weight DOM in filtered and unfiltered freshwater:Role of ultra-small microorganisms and implications for water quality monitoring

Dissolved organic matter (DOM) plays a central role in regulating productivity and nutrient cycling in freshwaters. It is therefore vital that we can representatively sample and preserve DOM in freshwaters for subsequent analysis. Here we investigated the effect of filtration, temperature (5 and 25 °C) and acidification (HCl) on the persistence of low molecular weight (MW) dissolved organic carbon (DOC), nitrogen (DON) and orthophosphate in oligotrophic and eutrophic freshwater environments. Our results showed the rapid loss of isotopically-labelled glucose and amino acids from both filtered (0.22 and 0.45 μm) and unfiltered waters. We ascribe this substrate depletion in filtered samples to the activity of ultra-small (< 0.45 μm) microorganisms (bacteria and archaea) present in the water. As expected, the rate of C, N and P loss was much greater at higher temperatures and was repressed by the addition of HCl. Based on our results and an evaluation of the protocols used in recently published studies, we conclude that current techniques used to sample water for low MW DOM characterisation are frequently inadequate and lack proper validation. In contrast to the high degree of analytical precision and rigorous statistical analysis of most studies, we argue that insufficient consideration is still given to the presence of ultra-small microorganisms and potential changes that can occur in the low MW fraction of DOM prior to analysis

Determining patterns in the composition of dissolved organic matter in fresh waters according to land use and management

In fresh waters, the origins of dissolved organic matter (DOM) have been found to exert a fundamental control on its reactivity, and ultimately, its ecosystem functional role. A detailed understanding of landscape scale factors that control the export of DOM to aquatic ecosystems is, therefore, pivotal if the effects of DOM flux to fresh waters are to be fully understood. In this study we present data from a national sampling campaign across the United Kingdom in which we explore the variability in DOM composition in three broad landscape types defined by similar precipitation, geology, land use and management, hydrology, and nutrient enrichment status. We characterised samples from fifty-one sites, grouping them into one of three major underlying classifications: circumneutral streams underlain by clay and mudstone (referred to as ‘clay’), alkaline streams underlain by Cretaceous Chalk or by Carboniferous or Jurassic Limestone (‘limestone’), and acidic streams in peatland catchments underlain by a range of low permeability lithologies (‘peat’). DOM composition was assessed through organic matter stoichiometry (organic carbon: organic nitrogen; organic carbon: organic phosphorus; C/N(P)DOM) and metrics derived from ultra-violet (UV)/visible spectroscopic analysis of DOM such as specific UV absorption (a254 nm; SUVA254). We found similar SUVA254, C/NDOM and DOM/a254 relationships within classifications, demonstrating that despite a large degree of heterogeneity within environments, catchments with shared environmental character and anthropogenic disturbance export DOM with a similar composition and character. Improving our understanding of DOM characterisation is important to help predict shifts in stream ecosystem function, and ecological responses to enrichment or mitigation efforts and how these may result in species composition shifts and biodiversity loss in freshwater ecosystems

Structural and functional studies of histidine biosynthesis in Acanthamoeba spp. demonstrates a novel molecular arrangement and target for antimicrobials

Acanthamoeba is normally free-living, but sometimes facultative and occasionally opportunistic parasites. Current therapies are, by necessity, arduous and yet poorly effective due to their inabilities to kill cyst stages or in some cases to actually induce encystation. Acanthamoeba can therefore survive as cysts and cause disease recurrence. Herein, in pursuit of better therapies and to understand the biochemistry of this understudied organism, we characterize its histidine biosynthesis pathway and explore the potential of targeting this with antimicrobials. We demonstrate that Acanthamoeba is a histidine autotroph, but with the ability to scavenge preformed histidine. It is able to grow in defined media lacking this amino acid, but is inhibited by 3-amino-1,2,4-triazole (3AT) that targets Imidazoleglycerol-Phosphate Dehydratase (IGPD) the rate limiting step of histidine biosynthesis. The structure of Acanthamoeba IGPD has also been determined in complex with 2-hydroxy-3-(1,2,4-triazol-1-yl) propylphosphonate [(R)-C348], a recently described novel inhibitor of Arabidopsis thaliana IGPD. This compound inhibited the growth of four Acanthamoeba species, having a 50% inhibitory concentration (IC50) ranging from 250-526 nM. This effect could be ablated by the addition of 1 mM exogenous free histidine, but importantly not by physiological concentrations found in mammalian tissues. The ability of 3AT and (R)-C348 to restrict the growth of four strains of Acanthamoeba spp. including a recently isolated clinical strain, while not inducing encystment, demonstrates the potential therapeutic utility of targeting the histidine biosynthesis pathway in Acanthamoeba

The <i>Castalia</i> mission to Main Belt Comet 133P/Elst-Pizarro

We describe Castalia, a proposed mission to rendezvous with a Main Belt Comet (MBC), 133P/Elst-Pizarro. MBCs are a recently discovered population of apparently icy bodies within the main asteroid belt between Mars and Jupiter, which may represent the remnants of the population which supplied the early Earth with water. Castalia will perform the first exploration of this population by characterising 133P in detail, solving the puzzle of the MBC’s activity, and making the first in situ measurements of water in the asteroid belt. In many ways a successor to ESA’s highly successful Rosetta mission, Castalia will allow direct comparison between very different classes of comet, including measuring critical isotope ratios, plasma and dust properties. It will also feature the first radar system to visit a minor body, mapping the ice in the interior. Castalia was proposed, in slightly different versions, to the ESA M4 and M5 calls within the Cosmic Vision programme. We describe the science motivation for the mission, the measurements required to achieve the scientific goals, and the proposed instrument payload and spacecraft to achieve these

Tea drinking and cognitive function in oldest-old Chinese

10.1007/s12603-012-0077-1The Journal of Nutrition, Health & Aging169754-75