Micromechanical response of fibre-reinforced materials using the boundary element technique

The Boundary Element Method (BEM) and the Embedded Cell Approach (ECA) have been used to analyse the effects of constituent material properties and fibre spatial distribution on the localised behaviour of a transversely loaded, unidirectional fibre-reinforced composite. The geometrical structures examined were perfectly periodic, uniformly spaced fibre arrangements in square and hexagonal embedded cells and ten cells in which 60 fibres were randomly placed within the matrix. The models involve both elastic fibres and matrix, with the interfaces between the different phases being fully bonded. The results indicate that both the fibre packing and the material properties of the constituent phases have a significant effect on the overall stress distribution and the magnitude of localised stress concentrations within a composite. Non-periodic arrangements give rise to higher local stresses, and the magnitudes of these stress concentrations have a strong dependence on the ligament length (distance between the two neighbouring fibres that have a common high-stress region), and to a lesser extent on the angle relative to the applied load (angle between a plane containing the two fibre centres and the applied load). Furthermore, analysis of a three-phase composite, comprised of a mixture of both stiff and compliant fibres, had higher stress concentrations than the equivalent two-phase composites

Benefits of current percolation in superconducting coated conductors

The critical currents of MOD/RABiTS and PLD/IBAD coated conductors have been measured as a function of magnetic field orientation and compared to films grown on single crystal substrates. By varying the orientation of magnetic field applied in the plane of the film, we are able to determine the extent to which current flow in each type of conductor is percolative. Standard MOD/RABiTS conductors have also been compared to samples whose grain boundaries have been doped by diffusing Ca from an overlayer. We find that undoped MOD/RABiTS tapes have a less anisotropic in-plane field dependence than PLD/IBAD tapes and that the uniformity of critical current as a function of in-plane field angle is greater for MOD/RABiTS samples doped with Ca.EPSRC US Department of Energ

High Expression of Galectin-1, VEGF and Increased Microvessel Density are Associated with MELF Pattern in Stage I-III Endometrioid Endometrial Adenocarcinoma

This is the final version. Available on open access via the DOI in this recordBackground: In this study, we investigate the expression of markers of angiogenesis and microvessel density (MVD) in cases of microcystic, elongated and fragmented (MELF) pattern, with its prognostic role in the survival of endometrioid endometrial cancer (EA) patients. Materials and Methods: In this study, 100 cases of EA, 49 cases with MELF pattern and 51 without, were immunohistochemically stained for galectin-1, vascular endothelial growth factor (VEGF), and MVD. Morphometry and statistical (univariate and multivariate) analyses were performed to assess overall survival (OS) and disease-free survival. Results: The expression of VEGF (p<.001) and galectin-1 (p<.001), as well asMVD area (p=.0003) and number of vessels/mm2 (p=.0043), were significantly higher in the +MELF pattern group compared to the -MELF group. A low negative correlation between MELF-pattern and the number of days of survival (p<.001, r=-0.47) was also found. A low positive correlation of MELF-pattern with galectin-1 expression (p<.001, r=0.39), area of vessels/mm2 (p<.001, r=0.36), outcome of EA (p<.001, r = 0.42) and VEGF expression (p<.001, r=0.39) suggests potential pathological relevance of these factors in the prognosis of EA. A univariate survival analysis indicated a role for all parameters of survival. Multivariate Cox proportional hazard regression analysis revealed that only area of vessels/mm2 (hazard ratio [HR], 1.018; 95% confidence interval [CI], 1.002 to 1.033), galectin-1 (HR, 1.049; 95% CI, 1.025 to 1.074) and VEGF (HR, 1.049; 95% CI, 1.022 to 1.077) play key roles in OS. Conclusion: This study reports an increase in MVD, VEGF and galectin-1 expression in EA with MELF pattern and suggests that MELF pattern, along with the angiogenic profile, may be a prognostic factor in EA.FORCE Cancer CharityGomel State Medical Universit

Mode Conversion of Guided Waves by Defects in Pipes

The corrosion of pipework is a major problem for the oil and gas and petro-chemical industries. Large facilities operate hundreds of kilometres of pipes which may carry corrosive substances. General wall-thinning and localised pitting corrosion can occur both from the inside and the outside of pipe walls. A high proportion of these pipes are insulated, so that even the external defects cannot be detected by conventional NDE techniques without the expense of removing of the insulation

A Clinical, Neuropathological and Genetic Study of Homozygous A467T POLG-Related Mitochondrial Disease

Mutations in the nuclear gene POLG (encoding the catalytic subunit of DNA polymerase gamma) are an important cause of mitochondrial disease. The most common POLG mutation, A467T, appears to exhibit considerable phenotypic heterogeneity. The mechanism by which this single genetic defect results in such clinical diversity remains unclear. In this study we evaluate the clinical, neuropathological and mitochondrial genetic features of four unrelated patients with homozygous A467T mutations. One patient presented with the severe and lethal Alpers-Huttenlocher syndrome, which was confirmed on neuropathology, and was found to have a depletion of mitochondrial DNA (mtDNA). Of the remaining three patients, one presented with mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes (MELAS), one with a phenotype in the Myoclonic Epilepsy, Myopathy and Sensory Ataxia (MEMSA) spectrum and one with Sensory Ataxic Neuropathy, Dysarthria and Ophthalmoplegia (SANDO). All three had secondary accumulation of multiple mtDNA deletions. Complete sequence analysis of muscle mtDNA using the MitoChip resequencing chip in all four cases demonstrated significant variation in mtDNA, including a pathogenic MT-ND5 mutation in one patient. These data highlight the variable and overlapping clinical and neuropathological phenotypes and downstream molecular defects caused by the A467T mutation, which may result from factors such as the mtDNA genetic background, nuclear genetic modifiers and environmental stressors

Arginase attenuates inhibitory nonadrenergic noncholinergic nerve-induced nitric oxide generation and airway smooth muscle relaxation

BACKGROUND: Recent evidence suggests that endogenous arginase activity potentiates airway responsiveness to methacholine by attenuation of agonist-induced nitric oxide (NO) production, presumably by competition with epithelial constitutive NO synthase for the common substrate, L-arginine. Using guinea pig tracheal open-ring preparations, we now investigated the involvement of arginase in the modulation of neuronal nitric oxide synthase (nNOS)-mediated relaxation induced by inhibitory nonadrenergic noncholinergic (iNANC) nerve stimulation. METHODS: Electrical field stimulation (EFS; 150 mA, 4 ms, 4 s, 0.5 – 16 Hz)-induced relaxation was measured in tracheal preparations precontracted to 30% with histamine, in the presence of 1 μM atropine and 3 μM indomethacin. The contribution of NO to the EFS-induced relaxation was assessed by the nonselective NOS inhibitor L-NNA (0.1 mM), while the involvement of arginase activity in the regulation of EFS-induced NO production and relaxation was investigated by the effect of the specific arginase inhibitor nor-NOHA (10 μM). Furthermore, the role of substrate availability to nNOS in EFS-induced relaxation was measured in the presence of various concentrations of exogenous L-arginine. RESULTS: EFS induced a frequency-dependent relaxation, ranging from 6.6 ± 0.8% at 0.5 Hz to 74.6 ± 1.2% at 16 Hz, which was inhibited with the NOS inhibitor L-NNA by 78.0 ± 10.5% at 0.5 Hz to 26.7 ± 7.7% at 8 Hz (P < 0.01 all). In contrast, the arginase inhibitor nor-NOHA increased EFS-induced relaxation by 3.3 ± 1.2-fold at 0.5 Hz to 1.2 ± 0.1-fold at 4 Hz (P < 0.05 all), which was reversed by L-NNA to the level of control airways in the presence of L-NNA (P < 0.01 all). Similar to nor-NOHA, exogenous L-arginine increased EFS-induced airway relaxation (P < 0.05 all). CONCLUSION: The results indicate that endogenous arginase activity attenuates iNANC nerve-mediated airway relaxation by inhibition of NO generation, presumably by limiting L-arginine availability to nNOS