Semi-parametric density estimation

The local likelihood method of Copas (1995a) allows for the incorporation into our parametric model of influence from data local to the point t at which we are estimating the true density function g(t). This is achieved through an analogy with censored data; we define the probability of a data point being considered observed, given that it has taken value xi, as where K is a scaled kernel function with smoothing parameter h. This leads to a likelihood function which gives more weight to observations close to t, hence the term ‘local likelihood’. After constructing this local likelihood function and maximising it at t, the resulting density estimate f(tiOt) can be described as semi-parametric in terms of its limits with respect to h. As h--oo, it approximates a standard parametric' fit f(I.O) whereas when h decreases towards 0, it approximates the non - parametric kernel density estimate. My thesis develops this idea, initially proving its asymptotic superiority over the standard parametric estimate under certain conditions. We then consider the improvements possible by making smoothing parameter h a function of /, enabling our semi parametric estimate to vary from approximating y(l) in regions of high density to f(t,0) in regions where we believe the true density to be low. Our improvement in accuracy is demonstrated in both simulated and real data examples, and the limits with respect to h and the new adaption parameter oo are examined. Methods for choosing h and oo are given and evaluated, along with a procedure for incorporating prior belief about the true form of the density into these choices. Further practical examples illustrate the effectiveness of I these ideas when applied to a wide range of data sets

Why do drivers become safer over the first three months of driving? A longitudinal qualitative study

Drivers are at high crash risk when they begin independent driving, with liability decreasing steeply over the first three months. Their behavioural development, and other changes underlying improved safety are not well understood. We adopted an innovative longitudinal qualitative design, with thirteen newly qualified drivers completing a total of 36 semi-structured interviews, one, two and three months after acquiring a full UK driving license. The interviews probed high-risk factors for new drivers, as well as allowing space for generating novel road safety issues. Analysis adopted a dual deductive and inductive interpretative thematic approach, identifying three super-ordinate themes: (1) Improvements in car control skills and situation awareness; (2) A reduction in the thrill of taking risks when driving against a background of generally increasing driving speed; (3) Early concerns about their social status in the eyes of other road users during the early stages of driving, which may put pressure on them to drive faster than they felt comfortable with. The study provides important new leads towards understanding how novice driving becomes safer over the first few months of driving, including how well-studied concepts of driving skill and style may change during development of independent driving, and a focus on the less rigorously studied concept of social status

Socioeconomic status and antisocial behaviour among children and adolescents: A systematic review and meta-analysis

Previous research on the association between socioeconomic status (SES) and child and adolescent antisocial behaviour has produced mixed findings showing variation in the strength of association. This systematic review and meta-analysis aimed to summarise evidence on the relationship between socioeconomic status and broadly conceptualised antisocial behaviour, investigating variation across a range of antisocial subtypes and other potential moderators, including age, sex and informant. We identified 133 studies containing data suitable for effect size calculation, and 139 independent effect sizes were analysed (total N = 339868). The global meta-analysis showed that lower family socioeconomic status was associated with higher levels of antisocial behaviour. Moderation analyses revealed this relationship was stronger where callous–unemotional traits were the outcome, and where antisocial behaviour was reported by parents or teachers rather than self-reported. The relationship between family SES and antisocial behaviour, however, was independent of higher-level constructs such as national income inequality. These results indicate that SES can be considered a robust correlate of broadly conceptualised antisocial behaviour but the strength of this relationship may depend on the antisocial subtype under investigation and the design of the stud

The art of face-saving and culture-changing: sculpting Chinese football’s past, present and future

In this paper, we consider the football statues of China, whose football team has dramatically underperformed relative to its population size and economic power. Although China lacks a participative grassroots football culture and has struggled to establish a credible domestic league, recent government intervention and investment has seen football’s profile rise dramatically. China’s many football statues are largely atypical in comparison to the rest of the world, including their depiction of anonymous figures rather than national or local heroes, the incorporation of tackling scenes in their designs, and their location at training camps. Through four specific examples and reference to a global database, we illustrate how these statues reflect the tensions and difficulties inherent in China’s desire to integrate itself into global football, and achieve its stated goal of hosting and winning the FIFA World Cup, whilst simultaneously upholding national, cultural and political values such as the primacy of hard work and learning, and saving face in defeat

Procrastination and health: A longitudinal test of the roles of stress and health behaviours

Objectives Procrastination is a common form of self-regulation failure that a growing evidence base suggests can confer risk for poor health outcomes, especially when it becomes habitual. However, the proposed linkages of chronic procrastination to health outcomes have not been tested over time or accounted for the contributions of higher-order personality factors linked to both chronic procrastination and health-related outcomes. We addressed these issues by examining the role of chronic procrastination in health outcomes over time in which the hypothesized links of procrastination to health problems operate via stress and health behaviours. Design Three-wave longitudinal study with 1-month intervals. Methods Participants (N = 379) completed measures of trait procrastination at Time 1, and measures of health behaviours, stress and health problems at each time point, in a lab setting. Results Procrastination and the health variables were inter-related in the expected directions across the three assessments. Chronic procrastination was positively associated with stress and negatively with health behaviours at each time point. Path analysis testing a cross-lagged longitudinal mediation model found an indirect relationship operating between procrastination and health problems via stress, after accounting for the contributions of conscientiousness and neuroticism. Conclusions This research extends previous work by demonstrating that the links between chronic procrastination and poor health are accounted for mainly by higher stress, after accounting for other key traits, and that these associations are robust over time. The findings are discussed in terms of the importance of addressing habitual self-regulation failure for improving health

THE EFFECTIVENESS OF IDEA CAPTURE SCHEMES

Innovation at work is mainly driven by employees' ideas. This paper reports a study of the effectiveness (e.g., rate of suggestion making) of schemes for capturing these ideas. Based on a survey of 182 UK organizations, the study shows that decentralized suggestion schemes and work-based systems are more effective than centralized and informal schemes. The extent of planning, publicity, feedback and management support given to the scheme, and the type of reward offered to employees, also independently account for variation in effectiveness. Publicity and non-monetary rewards, though, are found to be most decisive, regardless of scheme type. Learning culture also affects the rate of suggestion making, though the effect is greater for centralized and decentralized schemes than for the others. The key implication of the findings is that by paying particular attention to how they are advertised and how participation is rewarded, organizations could improve the return on their idea capture schemes.Idea capture schemes, suggestion schemes, quality circles, effectiveness

Bactericidal and anti-biofilm effects of uncharged and cationic ultrasound-responsive nitric oxide microbubbles on Pseudomonas aeruginosa biofilms

Bacterial biofilms are a major and ongoing concern for public health, featuring both inherited genetic resistance traits and a conferred innate tolerance to traditional antibiotic therapies. Consequently, there is a growing need for novel methods of drug delivery, to increase the efficacy of antimicrobial agents. This research evaluated the anti-biofilm and bactericidal effects of ultrasound responsive gas-microbubbles (MBs) of either air or nitric oxide, using an in vitro Pseudomonas aeruginosa biofilm model grown in artificial wound medium. The four lipid-based MB formulations evaluated were room-air MBs (RAMBs) and nitric oxide MBs (NOMBs) with no electrical charge, as well as cationic (+) RAMBs+ and NOMBs+. Two principal treatment conditions were used: i) ultrasound stimulated MBs only, and ii) ultrasound stimulated MBs with a sub-inhibitory concentration (4 µg/mL) of the antibiotic gentamicin. The total treatment time was divided into a 60 second passive MB interaction period prior to 40 second ultrasound exposure; each MB formulation was tested in triplicate. Ultrasound stimulated RAMBs and NOMBs without antibiotic achieved reductions in biofilm biomass of 93.3% and 94.0%, respectively. Their bactericidal efficacy however was limited, with a reduction in culturable cells of 26.9% and 65.3%, respectively. NOMBs with sub-inhibitory antibiotic produced the most significant reduction in biofilm biomass, corresponding to a 99.9% (SD ± 5.21%); and a 99.9% (SD ± 0.07%) (3-log) reduction in culturable bacterial cells. Cationic MBs were initially manufactured to promote binding of MBs to negatively charged biofilms, but these formulations also demonstrated intrinsic bactericidal properties. In the absence of antibiotic, the bactericidal efficacy of RAMB+ and NOMB+ was greater that of uncharged counterparts, reducing culturable cells by 84.7% and 86.1% respectively; increasing to 99.8% when combined with antibiotic. This study thus demonstrates the anti-biofilm and bactericidal utility of ultrasound stimulated MBs, and specifically is the first to demonstrate the efficacy of a NOMB for the dispersal and potentiation of antibiotics against bacterial biofilms in vitro. Importantly the biofilm system and complex growth-medium were selected to recapitulate key morphological features of in vivo biofilms. The results us offer new insight for the development of new clinical treatments, for example, in chronic wounds.</p