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Notes: The electronic properties of the (100) Si/SiO2 interfacial defect called Pb1 are quite controversial. We present electron spin resonance measurements that demonstrate: (1) that the Pb1 defects have levels in the silicon band gap, (2) that the Pb1 correlation energy is significantly smaller than that of the Pb1 defect, and (3) that the Pb1 levels are skewed toward the lower part of the silicon band gap. © 2002 American Institute of Physics.

Notes: Asthma and atopic disorders are the most common chronic diseases in the developed countries. Knowledge of the risk factors for these disorders may facilitate the development of preventive strategies aimed at reducing prevalence rates.To investigate the risk factors for asthma and allergic diseases in a large number of adults who are the parents of children in the National Asthma Campaign Manchester Asthma and Allergy Study.All pregnant women and their partners attending ‘Booking’ antenatal clinics were invited to take part in the study. Questionnaire data were collected including the history of asthma and other atopic diseases, pet ownership and smoking habits, and skin prick tests were performed. The prevalence of atopy and the risk factors for asthma and allergic disorders were investigated in all subjects who completed the questionnaire and underwent skin testing. Statistical analysis was carried out using logistic regression. Initially, risk factors were assessed by univariate analysis to see how each potential explanatory variable affected the probability of having allergic disease. Variables were then tested in a forward stepwise multivariate analysis.In 5687 adult subjects there was a very high (48.2%) prevalence of atopy, and 9.7% of subjects had a diagnosis of asthma. In a multivariate regression analysis sensitization to dust mite, cat, dog and mixed grasses were all independently associated with asthma. The odds ratios for current asthma increased with the increasing number of positive skin tests (any two allergens – OR 4.3, 95% CI 3.3–5.5; any three allergens – OR 7.0 95% CI 5.3–9.3; all four allergens – OR 10.4, 95% CI 7.7–14; P 〈 0.00001). Dog ownership (OR 1.31, 95% CI 1.10–1.57; P = 0.003) and current smoking (OR 1.36, 95% CI 1.15–1.62; P = 0.0004) were significantly and directly associated with ’asthma ever’. Thirteen per cent of participants reported a history of eczema. In the multivariate analysis the strongest independent associate of eczema was sensitization to dog (OR 1.37, 95% CI 1.14–1.63, P 〈 0.0001). Apart from dog, the strength of the association between sensitization to common allergens and eczema appeared to be much lower than in the case of asthma. The prevalence of hay fever was high (20.6%), and in the multivariate analysis the association between sensitization to pollen and hay fever was extremely strong (OR 13.6, 95% CI 11.3–16.3; P 〈 0.0001).The results of the current study emphasize the importance of sensitization to indoor allergens in asthma. However, evidence of a possible direct role of allergen exposure in asthma causation remains unclear.

Notes: Effect of microstructure on mixed-mode (mode I + II), high-cycle fatigue thresholds in a Ti-6Al-4V alloy is reported over a range of crack sizes from tens of micrometers to in excess of several millimeters. Specifically, two microstructural conditions were examined—a fine-grained equiaxed bimodal structure (grain size ∼20 µm) and a coarser lamellar structure (colony size ∼500 µm). Studies were conducted over a range of mode-mixities, from pure mode I (ΔKII/ΔKI = 0) to nearly pure mode II (ΔKII/ΔKI ∼ 7.1), at load ratios (minimum load/maximum load) between 0.1 and 0.8, with thresholds characterized in terms of the strain-energy release rate (ΔG) incorporating both tensile and shear-loading components. In the presence of through-thickness cracks—large (〉 4 mm) compared to microstructural dimensions—significant effects of mode-mixity and load ratio were observed for both microstructures, with the lamellar alloy generally displaying the better resistance. However, these effects were substantially reduced if allowance was made for crack-tip shielding. Additionally, when thresholds were measured in the presence of cracks comparable to microstructural dimensions, specifically short (∼200 µm) through-thickness cracks and microstructurally small (〈 50 µm) surface cracks, where the influence of crack-tip shielding would be minimal, such effects were similarly markedly reduced. Moreover, small-crack ΔGTH thresholds were some 50–90 times smaller than corresponding large crack values. Such effects are discussed in terms of the dominant role of mode I behaviour and the effects of microstructure (in relation to crack size) in promoting crack-tip shielding that arises from significant changes in the crack path in the two structures.