Impact echo data from bridge deck testing: Visualization and interpretation

Accurate assessment of the condition of bridges leads to their economic management. Ultrasonic seismic methods can be successfully used for this purpose through evaluation of changes in material characteristics and detection of the development of defects and zones of deterioration. The impact echo (IE) method is of special benefit in evaluation of corrosion-induced deck delamination, due to the method's nondestructive nature, speed of evaluation, and ability to detect delaminated zones at various stages of deterioration: from initial to progressed and developed. The traditional approach in condition assessment of bridge decks by IE on the basis of review of individual test point records and a new automated approach based on three-dimensional (3-D) data visualization are presented. The developed 3-D visualization platform allows both the advanced presentation and interpretation of IE data. The data presentation is provided as 3-D translucent visualizations of reflectors in a bridge deck section and horizontal and vertical cross sections through all distinctive zones, including a zone of delamination. The associated interpretation platform allows both (a) the overall assessment of the condition of the deck, through cumulative distributions and histograms of reflection intensity, and (b) identification of deteriorated zones of the deck for repair or rehabilitation in an efficient and intuitive way. The visualization platform effectively enables an IE device to be used as a type of bridge deck sonar device

Raptor talon shape and biomechanical performance are controlled by relative prey size but not by allometry

Most birds of prey (raptors), rely heavily on their talons for capturing prey. However, the relationship between talon shape and the ability to take prey is poorly understood. In this study we investigate whether raptor talons have evolved primarily in response to adaptive pressures exerted by different dietary demands, or if talon morphology is largely constrained by allometric or phylogenetic factors. We focus on the hallux talon and include 21 species in total varying greatly in body mass and feeding ecology, ranging from active predation on relatively large prey to obligate scavenging. To quantify the variation in talon shape and biomechanical performance within a phylogenetic framework, we combined three dimensional (3D) geometric morphometrics, finite element modelling and phylogenetic comparative methods. Our results indicate that relative prey size plays a key role in shaping the raptorial talon. Species that hunt larger prey are characterised by both distinct talon shape and mechanical performance when compared to species that predate smaller prey, even when accounting for phylogeny. In contrast to previous results of skull-based analysis, allometry had no significant effect. In conclusion, we found that raptor talon evolution has been strongly influenced by relative prey size, but not allometry and, that talon shape and mechanical performance are good indicators of feeding ecology

Finite Element Studies of Transient Wave Propagation

The National Bureau of Standards (NBS) has been working to develop a nondestructive test method for heterogenous solids using transient stress waves [1-5]. The method is referred to as the impact-echo method. The technique involves introducing a transient stress pulse into a test object by mechanical impact at a point and measuring the surface displacement caused by the arrival of reflections of the pulse from internal defects and external boundaries. Successful signal interpretation requires an understanding of the nature of transient stress wave propagation in solids containing defects. A primary focus of the NBS program is on using the finite element method to gain this understanding.</p

Dihydrolipoic Acid Conjugated Carbon Dots Accelerate Human Insulin Fibrillation

Protein fibrillation is believed to play an important role in the pathology and development of several human diseases, such as Alzheimer’s disease, Parkinson’s disease and type 2 diabetes. Carbon dots (CDs), as a new type of nanoparticle have recently been extensively studied for potential biological applications, but their effects on protein fibrillation remain unexplored. In reality, any application in biological systems will inevitably have “contact” between proteins and CDs. In this study, human insulin was selected as a model protein to study the effects of CDs on protein fibrillation, as proteins may share a common mechanism to form fibrils. Hydrophobic CDs were conjugated with dihydrolipoic acid (DHLA-CDs) to facilitate their water solubility. Characterizations from thioflavin T fluorescence, circular dichroism spectroscopy and atomic force microscopy demonstrate that the presence of DHLA-CDs results in a higher rate of human insulin fibrillation, accelerating the conformational changes of human insulin from α-helix to β-sheet. This promoting effect is likely associated with the locally increased concentration of human insulin adsorbed on the surface of DHLA-CDs

Anisotropic diffusion of water molecules in hydroxyapatite nanopores

Funded by EPSRC Grant EP/K000128/1