569 research outputs found

    Detection of subsurface anomalies in fiber-reinforced polymer (FRP) wrapped timber bridge components using infrared thermography

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    This thesis presents the results of an experimental study on the use of Infrared Thermography technique for detection of subsurface anomalies in fiber reinforced polymer (FRP) wrapped timber bridge components. An extensive literature review on the application of various nondestructive evaluation techniques to composite structures has also been presented.;Simulated subsurface delaminations were constructed in the laboratory in timber piles wrapped with FRP composite fabric. The delaminations varied in size, thickness, and severity. These delaminations were placed between the 1/8&inches; thick FRP wrap and timber surface. The thermal images from the delaminated specimens were compared with thermal images from undamaged specimens to study the effect of subsurface anomalies. In addition, several field tests were conducted using the infrared imaging system on three timber railroad bridges located in Moorefield, West Virginia that were reinforced with FRP composite fabric. The field test data was used to detect debonds at the composite-timber interface and study the effect of environmental parameters on infrared images.;This study shows that the infrared thermography technique can be used to effectively to detect subsurface delaminations in timber components wrapped with FRP composite fabric. The study also shows the effect of different parameters (environmental conditions, heat source, etc.) on the clarity of infrared images

    Persister cells in Burkholderia thailandensis

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    PhD studentship “Pathways that enhance antibiotic efficacy” 1/10/12-30/9/15Persister cells are able to survive in the presence of high concentrations of antibiotic, and re-grow once the antibiotic has been removed. Unlike conventional antibiotic resistance, the antibiotic tolerance of persister cells is due to phenotypic switching, and is non-inherited. There is growing evidence for a role of persisters in various persistent bacterial diseases. Burkholderia pseudomallei is a pathogen which causes melioidosis, which often persists in the host despite antibiotic treatment. As persister cells may contribute to persistent melioidosis, this study investigated persisters in B. thailandensis, as a model for B. pseudomallei. Treatment of B. thailandensis with ceftazidime, ciprofloxacin, imipenem or trimethoprim demonstrated persister cells which survived antibiotic treatment. Persister frequencies were increased in the absence of oxygen, and higher in stationary phase cultures compared with growing cultures. Drug concentration did not affect persister frequencies, and inherited antibiotic resistance was not detected. Different persister fractions were detected using treatment with multiple antibiotics, indicating heterogeneous susceptibility to antibiotics. In order to increase understanding of the molecular basis of B. thailandensis persister cells, a transposon mutagenesis-based sequencing approach was used on persister cultures. This indicated some issues with genome coverage and mutant diversity. Genes were identified from mutants present before and/or after ciprofloxacin treatment. In order to try to eradicate persister cells from a culture, two anti-persister strategies were tested. Itaconate appeared to stimulate growth of B. thailandensis, increasing susceptibility to the antibiotic ceftazidime. However, the overall effect of the combination was no greater than ceftazidime alone in the conditions tested. Metronidazole was effective against a persister culture under anaerobic conditions, suggesting it may be useful in treating anaerobic persisters. Treatment of B. pseudomallei infected mice with metronidazole and ceftazidime did not improve survival over ceftazidime treatment alone.DSTL and University of Exete

    Fostering Reading Fluency in the School Library

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    Analysis of Haplotype Sequences

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    In this era of whole-genome, next-generation sequencing, it is important to have a clear understanding of the concept of “haplotype”. We show here that most of the important regions of the genome can be described in terms of polymorphic frozen blocks (PFB). At each PFB, there are numerous, even hundreds, of alternative ancestral haplotypes. Haplotypes, not genes, can be regarded as the principal unit of inheritance. We illustrate how sequence data can be analysed to reveal and define these ancestral haplotypes

    Three-Dimensional Turbulence Characteristics of the Bottom Boundary Layer of the Coastal Ocean

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    The form and dynamics of ocean turbulence are critical to all marine processes; biological, chemical and physical. The three-dimensional turbulence characteristics of the bottom boundary layer of the coastal ocean are examined using a series of 29,991 instantaneous velocity distributions. These data, recorded by a submersible 3D-PTV system at an elevation of 0.64 m above the seabed, represent conditions typical of moderate tidal flows in the coastal ocean. A complexity associated with submersible 3D-PTV in the coastal ocean is that gaps and noise affect the accuracy of the data collected. To accommodate this, a new Physics-Enabled Flow Restoration Algorithm has been tested for the restoration of gappy and noisy velocity measurements where a standard PTV or PIV laboratory set-up (e.g. concentration / size of the particles tracked) is not possible and the boundary and initial conditions are not known a priori. This is able to restore the physical structure of the flow from gappy and noisy data, in accordance with its hydrodynamical basis. In addition to the restoration of the velocity flow field, PEFRA also estimates the maximum possible deviation of the output from the true flow. 3D-PTV measurements show coherent structures, with the hairpin-like vortices highlighted in laboratory measurements and numerical modelling, were frequently present within the logarithmic layer. These exhibit a modal alignment of 8 degrees from the mean flow and a modal elevation of 27 degrees from the seabed, with a mean period of occurrence of 4.3 sec. These appear to straddle sections of zero-mean along-stream velocity, consistent with an interpretation as packets. From these measurements, it is clear that data collected through both laboratory and numerical experiments are directly applicable to geophysical scales – a finding that will enable the fine-scale details of particle transport and pollutant dispersion to be studied in future. Conditional sampling of the Reynolds shear stress (without using Taylor’s hypothesis) reveals that these coherent structures are responsible for the vertical exchange of momentum and, as such, are the key areas where energy is extracted from the mean flow and into turbulence. The present study offers the first assessment of the magnitude of the errors associated with assuming isotropy on shear-based sensors of the TKE dissipation rate and its consequential effect on the Kolmogorov microscale using 3D-PTV data from the bottom boundary layer of the coastal ocean. The results indicate a high degree of spatial variability associated with the low conditions. The averaged data supports the validity of measurements obtained by horizontal and vertical profilers, however along-stream velocity derivatives underestimate the TKE dissipation rate by more than 40% – a factor of two higher than for the equivalent cross-stream and vertical estimates. This has important implications for the deployment of these sensors and the subsequent interpretation of higher-order statistics. Finally, the data have been processed to test four popular sub-grid scale (SGS) stress models and SGS dissipation rate estimates for Large-Eddy Simulations using these in situ experimental data. When the correlation and SGS model coefficients are assessed, the nonlinear model represents the best stress models to use for the present data, consistent with the substantial anisotropy and inhomogeneity associated with these flows. The detailed measurement and analysis of coherent structures in the coastal ocean undertaken therefore supports the development of numerical models and assists with the understanding of all marine processes

    A Comprehensive Three-Dimensional Model of the Cochlea

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    The human cochlea is a remarkable device, able to discern extremely small amplitude sound pressure waves, and discriminate between very close frequencies. Simulation of the cochlea is computationally challenging due to its complex geometry, intricate construction and small physical size. We have developed, and are continuing to refine, a detailed three-dimensional computational model based on an accurate cochlear geometry obtained from physical measurements. In the model, the immersed boundary method is used to calculate the fluid-structure interactions produced in response to incoming sound waves. The model includes a detailed and realistic description of the various elastic structures present. In this paper, we describe the computational model and its performance on the latest generation of shared memory servers from Hewlett Packard. Using compiler generated threads and OpenMP directives, we have achieved a high degree of parallelism in the executable, which has made possible several large scale numerical simulation experiments that study the interesting features of the cochlear system. We show several results from these simulations, reproducing some of the basic known characteristics of cochlear mechanics.Comment: 22 pages, 5 figure

    The integrin alpha 6 beta 4 is a laminin receptor

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    In this study, the putative laminin receptor function of the alpha 6 beta 4 integrin was assessed. For this purpose, we used a human cell line, referred to as clone A, that was derived from a highly invasive, colon adenocarcinoma. This cell line, which expresses the alpha 6 beta 4 integrin, adheres to the E8 and not to the P1 fragment of laminin. The adhesion of clone A cells to laminin is extremely rapid with half-maximal adhesion observed at 5 min after plating. Adhesion to laminin is blocked by GoH3, and alpha 6 specific antibody (60% inhibition), as well as by A9, a beta 4 specific antibody (30% inhibition). Most importantly, we demonstrate that alpha 6 beta 4 binds specifically to laminin-Sepharose columns in the presence of either Mg2+ or Mn2+ and it is eluted from these columns with EDTA but not with NaCl. The alpha 6 beta 4 integrin does not bind to collagen-Sepharose, but the alpha 2 beta 1 integrin does bind. Clone A cells do not express alpha 6 beta 1 as evidenced by the following observations: (a) no beta 1 integrin is detected in beta 1 immunoblots of GoH3 immunoprecipitates; and (b) no alpha 6 beta 1 integrin is seen in GoH3 immunoprecipitates of clone A extracts that had been immunodepleted of all beta 4 containing integrin using the A9 antibody. These data establish that laminin is a ligand for the alpha 6 beta 4 integrin and that this integrin can function as a laminin receptor independently of alpha 6 beta 1

    Blood and saliva-derived exomes from healthy Caucasian subjects do not display overt evidence of somatic mosaicism

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    Somatic mosaicism is a normal occurrence during development in the tissues and organs. As part of establishing a “healthy population “(HP) background or base-line, we investigated whether such mosaicism can be routinely detected in the circulating DNA secured from a rigorously designed healthy human liquid biopsy clinical trial (saliva, blood). We deployed next generation (NG) whole exome sequencing (WES) at median exome coverage rates of 97.2 % (-to-30x) and 70.0 % (-to-100x). We found that somatic mosaicism is not detectable by such standard bulk WES sequencing assays in saliva and blood DNA in 24 normal healthy Caucasians of both sexes from 18 to 60 years of age. We conclude that for circulating DNA using standard WES no novel somatic mutational variants can be detected in protein-coding regions of normal healthy subjects. This implies that the extent within normal tissues of somatic mosaicism must be at a lower level, below the detection threshold, for these circulating DNA WES read depths. © 2020 The Author(s
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