Networks in the Premodern Economy: the Market for London Apprenticeships, 1600-1749

This paper examines the importance of social and geographical networks in structuring entry into skilled occupations in premodern London. Using newly digitised records of those beginning an apprenticeship in London between 1600 and 1749, we find little evidence that networks strongly shaped apprentice recruitment. The typical London apprentice did not have an identifiable connection to his master in the form of a kin link, shared name, or shared place or county of origin. The majority of migrant apprentices' fathers came from outside of the craft sector. Our results suggest that the market for apprenticeship was strikingly open: well-to-do families of all types were able to access a wide range of craft and trade apprenticeships, and would-be apprentices had considerable scope to match their perceived ability and aptitude to opportunity.Apprenticeship, human capital formation, training, migration, networks, UK, early modern

A multi-physics method for fracture and fragmentation at high strain-rates

This work outlines a diffuse interface method for the study of fracture and fragmentation in ductile metals at high strain-rates in Eulerian finite volume simulations. The work is based on an existing diffuse interface method capable of simulating a broad range of different multi-physics applications, including multi-material interaction, damage and void opening. The work at hand extends this method with a technique to model realistic material inhomogeneities, and examines the performance of the method on a selection of challenging problems. Material inhomogeneities are included by evolving a scalar field that perturbs a material's plastic yield stress. This perturbation results in non-uniform fragments with a measurable statistical distribution, allowing for underlying defects in a material to be modelled. As the underlying numerical scheme is three dimensional, parallelisable and multi-physics-capable, the scheme can be tested on a range of strenuous problems. These problems especially include a three-dimensional explosively driven fracture study, with an explicitly resolved condensed phase explosive. The new scheme compares well with both experiment and previous numerical studies

Pilot of ‘Families for Health’ : community-based family intervention for obesity

Objective - To develop and evaluate ‘Families for Health’ - a new community based family intervention for childhood obesity. Design – Programme development, pilot study and evaluation using intention-to-treat analysis. Setting – Coventry, England Participants – 27 overweight or obese children aged 7-13 years (18 girls, 9 boys) and their parents, from 21 families. Intervention – ‘Families for Health’ is a 12 week programme with parallel groups for parents and children, addressing parenting, lifestyle change and social & emotional development. Main Outcome Measures – Primary: change in baseline BMI z-score at end of programme (3 months) and 9 month follow-up. Attendance, drop-out, parents’ perception of programme, child’s quality of life and self esteem, parental mental health, parent-child relationships and lifestyle changes were also measured. Results: Attendance rate was 62%, with 18 of the 27 (67%) children completing the programme. For the 22 children with follow-up data (including 4 drop-outs), BMI z-score was reduced by -0.18 (95%CI -0.30 to -0.05) at end of programme and by -0.21 (-0.35 to -0.07) at 9 months. Statistically significant improvements were observed in children’s quality of life and lifestyle (reduced sedentary behaviour, increased steps and reduced exposure to unhealthy foods), child-parent relationships and parents’ mental health. Fruit and vegetable consumption, participation in moderate/vigorous exercise and children’s self-esteem did not change significantly. Topics on parenting skills, activity and food were rated as helpful and were used with confidence by the majority of parents. Conclusions Families for Health is a promising new childhood obesity intervention. Definitive evaluation of its clinical effectiveness by randomised controlled trial is now required

Yersinia ruckeri isolates recovered from diseased Atlantic Salmon (Salmo salar) in Scotland are more diverse than those from Rainbow Trout (Oncorhynchus mykiss) and represent distinct subpopulations

Yersinia ruckeri is the etiological agent of enteric redmouth (ERM) disease of farmed salmonids. Enteric redmouth disease is traditionally associated with rainbow trout (Oncorhynchus mykiss, Walbaum), but its incidence in Atlantic salmon (Salmo salar) is increasing. Yersinia ruckeri isolates recovered from diseased Atlantic salmon have been poorly characterized, and very little is known about the relationship of the isolates associated with these two species. Phenotypic approaches were used to characterize 109 Y. ruckeri isolates recovered over a 14-year period from infected Atlantic salmon in Scotland; 26 isolates from infected rainbow trout were also characterized. Biotyping, serotyping, and comparison of outer membrane protein profiles identified 19 Y. ruckeri clones associated with Atlantic salmon but only five associated with rainbow trout; none of the Atlantic salmon clones occurred in rainbow trout and vice versa. These findings suggest that distinct subpopulations of Y. ruckeri are associated with each species. A new O serotype (designated O8) was identified in 56 biotype 1 Atlantic salmon isolates and was the most common serotype identified from 2006 to 2011 and in 2014, suggesting an increased prevalence during the time period sampled. Rainbow trout isolates were represented almost exclusively by the same biotype 2, serotype O1 clone that has been responsible for the majority of ERM outbreaks in this species within the United Kingdom since the 1980s. However, the identification of two biotype 2, serotype O8 isolates in rainbow trout suggests that vaccines containing serotypes O1 and O8 should be evaluated in both rainbow trout and Atlantic salmon for application in Scotland

The slope of the psychometric function and non-stationarity of thresholds in spatiotemporal contrast vision

The slope of the two-interval, forced-choice psychometric function (e.g. the Weibull parameter, ß) provides valuable information about the relationship between contrast sensitivity and signal strength. However, little is known about how or whether ß varies with stimulus parameters such as spatiotemporal frequency and stimulus size and shape. A second unresolved issue concerns the best way to estimate the slope of the psychometric function. For example, if an observer is non-stationary (e.g. their threshold drifts between experimental sessions), ß will be underestimated if curve fitting is performed after collapsing the data across experimental sessions. We measured psychometric functions for 2 experienced observers for 14 different spatiotemporal configurations of pulsed or flickering grating patches and bars on each of 8 days. We found ß ˜ 3 to be fairly constant across almost all conditions, consistent with a fixed nonlinear contrast transducer and/or a constant level of intrinsic stimulus uncertainty (e.g. a square law transducer and a low level of intrinsic uncertainty). Our analysis showed that estimating a single ß from results averaged over several experimental sessions was slightly more accurate than averaging multiple estimates from several experimental sessions. However, the small levels of non-stationarity (SD ˜ 0.8 dB) meant that the difference between the estimates was, in practice, negligible

Contrast and lustre:a model that accounts for eleven different forms of contrast discrimination in binocular vision

Our goal here is a more complete understanding of how information about luminance contrast is encoded and used by the binocular visual system. In two-interval forced-choice experiments we assessed observers' ability to discriminate changes in contrast that could be an increase or decrease of contrast in one or both eyes, or an increase in one eye coupled with a decrease in the other (termed IncDec). The base or pedestal contrasts were either in-phase or out-of-phase in the two eyes. The opposed changes in the IncDec condition did not cancel each other out, implying that along with binocular summation, information is also available from mechanisms that do not sum the two eyes' inputs. These might be monocular mechanisms. With a binocular pedestal, monocular increments of contrast were much easier to see than monocular decrements. These findings suggest that there are separate binocular (B) and monocular (L,R) channels, but only the largest of the three responses, max(L,B,R), is available to perception and decision. Results from contrast discrimination and contrast matching tasks were described very accurately by this model. Stimuli, data, and model responses can all be visualized in a common binocular contrast space, allowing a more direct comparison between models and data. Some results with out-of-phase pedestals were not accounted for by the max model of contrast coding, but were well explained by an extended model in which gratings of opposite polarity create the sensation of lustre. Observers can discriminate changes in lustre alongside changes in contrast

Designing a Mobile Game to Generate Player Data - Lessons Learned

User friendly tools have lowered the costs of high-quality game design to the point where researchers without development experience can release their own games. However, there is no established best-practice as few games have been produced for research purposes. Having developed a mobile game without the guidance of similar projects, we realised the need to share our experience so future researchers have a path to follow. Research into game balancing and system simulation required an experimental case study, which inspired the creation of “RPGLite”, a multiplayer mobile game. In creating RPGLite with no development expertise we learned a series of lessons about effective amateur game development for research purposes. In this paper we reflect on the entire development process and present these lessons

Assessing spinal movement during four extrication methods:a biomechanical study using healthy volunteers

BACKGROUND Motor vehicle collisions are a common cause of death and serious injury. Many casualties will remain in their vehicle following a collision. Trapped patients have more injuries and are more likely to die than their untrapped counterparts. Current extrication methods are time consuming and have a focus on movement minimisation and mitigation. The optimal extrication strategy and the effect this extrication method has on spinal movement is unknown. The aim of this study was to evaluate the movement at the cervical and lumbar spine for four commonly utilised extrication techniques. METHODS Biomechanical data was collected using inertial Measurement Units on 6 healthy volunteers. The extrication types examined were: roof removal, b-post rip, rapid removal and self-extrication. Measurements were recorded at the cervical and lumbar spine, and in the anteroposterior (AP) and lateral (LAT) planes. Total movement (travel), maximal movement, mean, standard deviation and confidence intervals are reported for each extrication type. RESULTS Data from a total of 230 extrications were collected for analysis. The smallest maximal and total movement (travel) were seen when the volunteer self-extricated (AP max = 2.6 mm, travel 4.9 mm). The largest maximal movement and travel were seen in rapid extrication extricated (AP max = 6.21 mm, travel 20.51 mm). The differences between self-extrication and all other methods were significant (p < 0.001), small non-significant differences existed between roof removal, b-post rip and rapid removal. Self-extrication was significantly quicker than the other extrication methods (mean 6.4 s). CONCLUSIONS In healthy volunteers, self-extrication is associated with the smallest spinal movement and the fastest time to complete extrication. Rapid, B-post rip and roof off extrication types are all associated with similar movements and time to extrication in prepared vehicles