Specifying peripheral aberrations in visual science

Purpose: Investigations of foveal aberrations assume circular pupils. However, the pupil becomes increasingly elliptical with increase in visual field eccentricity. We address this and other issues concerning peripheral aberration specification. Methods: One approach uses an elliptical pupil similar to the actual pupil shape, stretched along its minor axis to become a circle so that Zernike circular aberration polynomials may be used. Another approach uses a circular pupil whose diameter matches either the larger or smaller dimension of the elliptical pupil. Pictorial presentation of aberrations, influence of wavelength on aberrations, sign differences between aberrations for fellow eyes, and referencing position to either the visual field or the retina are considered. Results: Examples show differences between the two approaches. Each has its advantages and disadvantages, but there are ways to compensate for most disadvantages. Two representations of data are pupil aberration maps at each position in the visual field and maps showing the variation in individual aberration coefficients across the field. Conclusions: Based on simplicity of use, adequacy of approximation, possible departures of off-axis pupils from ellipticity, and ease of understanding by clinicians, the circular pupil approach is preferable to the stretched elliptical approach for studies involving field angles up to 30 deg.

Speeding by young novice drivers : what can personal characteristics and psychosocial theory add to our understanding?

Purpose: Young novice drivers continue to be overrepresented in fatalities and injuries arising from crashes even with the introduction of countermeasures such as graduated driver licensing (GDL). Enhancing countermeasures requires a better understanding of the variables influencing risky driving. One of the most common risky behaviours performed by drivers of all ages is speeding, which is particularly risky for young novice drivers who, due to their driving inexperience, have difficulty in identifying and responding appropriately to road hazards. Psychosocial theory can improve our understanding of contributors to speeding, thereby informing countermeasure development and evaluation. This paper reports an application of Akers’ social learning theory (SLT), augmented by Gerrard and Gibbons’ prototype/willingness model (PWM), in addition to personal characteristics of age, gender, car ownership, and psychological traits/states of anxiety, depression, sensation seeking propensity and reward sensitivity, to examine the influences on self-reported speeding of young novice drivers with a Provisional (intermediate) licence in Queensland, Australia. Method: Young drivers (n = 378) recruited in 2010 for longitudinal research completed two surveys containing the Behaviour of Young Novice Drivers Scale, and reported their attitudes and behaviours as pre-Licence/Learner (Survey 1) and Provisional (Survey 2) drivers and their sociodemographic characteristics. Results: An Akers’ measurement model was created. Hierarchical multiple regressions revealed that (1) personal characteristics (PC) explained 20.3%; (2) the combination of PC and SLT explained 41.1%; and (3) the combination of PC, SLT and PWM explained 53.7% of variance in self-reported speeding. Whilst there appeared to be considerable shared variance, the significant predictors in the final model included gender, car ownership, reward sensitivity, depression, personal attitudes, and Learner speeding. Conclusions: These results highlight the capacity for psychosocial theory to improve our understanding of speeding by young novice drivers, revealing relationships between previous behaviour, attitudes, psychosocial characteristics and speeding. The findings suggest multi-faceted countermeasures should target the risky behaviour of Learners, and Learner supervisors should be encouraged to monitor their Learners’ driving speed. Novice drivers should be discouraged from developing risky attitudes towards speeding.

Introduction

In this volume we compile and comment on a collection of some of the most important works on nascent entrepreneurship that have appeared in the last two decades. We do not go further back than that because up until1992 hardly any systematic research on the pre-operational stage of business creation was undertaken. In that year, the terms 'nascent entrepreneur' and 'nascent venture' appear for the first time in the research literature (Reynolds and Miller, Chapter l, 1992; Reynolds and White, 1992). This signals the emergence of a new research paradigm designed to study• business creation processes empirically at very early stages, before an operational firm has come into existence. The most central feature of this type of research is that it identifies a statistically representative sample of nascent entrepreneurs (NEs)- people engaged in ongoing but not yet operational business start-ups- via screening interviews with a very large random sample of adults. The overarching research questions pursued in this emerging research tradition are the following: 1. What proportion of individuals (in various population subgroups) are trying to start a new business at any given time? 2. What led them to engage in the creation of a new business? 3. What characteristics and behaviors associated with the founder(s), the venture, the environment and the process are associated with persistence, progress and success in trying to start a new business?

Where do they come from? Prevalence and characteristics of nascent entrepreneurs

This paper reports on a unique study of a large, random sample of business start-ups that were identified prior to the actual, commercial launch of the ventures. The purpose of this paper is two-fold. First, to present frequencies on the involvement of the Swedish population in the small business sector (particularly in start-ups of firms) and to compare these with estimates from Norway and the USA, which are based on studies using a similar research design. The authors also discuss the possible reasons for the differences that emerge between countries. Second, the characteristics of nascent entrepreneurs (i.e. individuals trying to start an independent business) are analysed and compared for sub-groups within the sample and with characteristics of business founders as they appear in theoretical accounts or retrospective empirical studies of surviving all firms. In order to get a representative sample from the working age population, respondents (n = 30,427) were randomly selected and interviewed by telephone. It was found that 2.0% of the Swedish population at the time of the interview were trying to start an independent business. Sweden had a significantly lower prevalence rate of nascent entrepreneurs compared to Norway and the USA. Nascent entrepreneurs were then compared to a control group of people not trying to start a business. The results confirmed findings from previous studies of business founders pointing to the importance of role models and the impression of self-employment obtained through these, employment status, age, education and experience. Marital status, the number of children in the household, and length of employment experience were unrelated to the probability of becoming a nascent entrepreneur. The gender of the respondent was the strongest distinguishing factor. Importantly, the results suggest that while one has a reasonably good understanding of the characteristics associated with men going into business for themselves, the type of variables investigated here have very limited ability to predict nascent entrepreneur status for women.

The role of social and human capital among nascent entrepreneurs

This study examines nascent entrepreneurship by comparing individuals engaged in nascent activities (n=380) with a control group (n=608), after screening a sample from the general population (n=30,427). The study then follows the developmental process of nascent entrepreneurs for 18 months. Bridging and bonding social capital, consisting of both strong and weak ties, was a robust predictor for nascent entrepreneurs, as well as for advancing through the start-up process. With regard to outcomes like first sale or showing a profit, only one aspect of social capital, viz. being a member of a business network, had a statistically significant positive effect. The study supports human capital in predicting entry into nascent entrepreneurship, but only weakly for carrying the start-up process towards successful completion.

Does venture opportunity variation matter? Investigating systemic process differences between innovative and imitative new ventures

The central thesis in the article is that the venture creation process is different for innovative versus imitative ventures. This holds up; the pace of the process differs by type of venture as do, in line with theory-based hypotheses, the effects of certain human capital (HC) and social capital (SC) predictors. Importantly, and somewhat unexpectedly, the theoretically derived models using HC, SC, and certain controls are relatively successful explaining progress in the creation process for the minority of innovative ventures, but achieve very limited success for the imitative majority. This may be due to a rationalistic bias in conventional theorizing and suggests that there is need for considerable theoretical development regarding the important phenomenon of new venture creation processes. Another important result is that the building up of instrumental social capital, which we assess comprehensively and as a time variant construct, is important for making progress with both types of ventures, and increasingly, so as the process progresses. This result corroborates with stronger operationalization and more appropriate analysis method what previously published research has only been able to hint at.

Child welfare policy and practice on children’s exposure to domestic violence

There are emerging movements in several countries to improve policy and practice to protect children from exposure to domestic violence. These movements have resulted in the collection of new data on EDV and the design and implementation of new child welfare policies and practices. To assist with the development of child welfare practice, this article summarizes current knowledge on the prevalence of EDV, and on child welfare services policies and practices that may hold promise for reducing the frequency and impact of EDV on children. We focus on Australia, Canada, and the United States, as these countries share a similar socio-legal context, a long history of enacting and expanding legislation about reporting of maltreatment, debates regarding the application of reporting laws to EDV, and new child welfare practices that show promise for responding more effectively to EDV.

Vulnerable road user groups : a review of younger drivers, motorcyclists and older drivers

Scientific efforts to understand and reduce the occurrence of road crashes continue to expand, particularly in the areas of vulnerable road user groups. Three groups that are receiving increasing attention within the literature are younger drivers, motorcyclists and older drivers. These three groups are at an elevated risk of being in a crash or seriously injured, and research continues to focus on the origins of this risk as well as the development of appropriate countermeasures to improve driving outcomes for these cohorts. However, it currently remains unclear what factors produce the largest contribution to crash risk or what countermeasures are likely to produce the greatest long term positive effects on road safety. This paper reviews research that has focused on the personal and environmental factors that increase crash risk for these groups as well as considers direction for future research in the respective areas. A major theme to emerge from this review is that while there is a plethora of individual and situational factors that influence the likelihood of crashes, these factors often combine in an additive manner to exacerbate the risk of both injury and fatality. Additionally, there are a number of risk factors that are pertinent for all three road user groups, particularly age and the level of driving experience. As a result, targeted interventions that address these factors are likely to maximise the flow-on benefits to a wider range of road users. Finally, there is a need for further research that aims to bridge the research-to-practice gap, in order to develop appropriate pathways to ensure that evidenced-based research is directly transferred to effective policies that improve safety outcomes.

New exact solutions for Hele-Shaw flow in doubly connected regions

Radial Hele-Shaw flows are treated analytically using conformal mapping techniques. The geometry of interest has a doubly-connected annular region of viscous fluid surrounding an inviscid bubble that is either expanding or contracting due to a pressure difference caused by injection or suction of the inviscid fluid. The zero-surface-tension problem is ill-posed for both bubble expansion and contraction, as both scenarios involve viscous fluid displacing inviscid fluid. Exact solutions are derived by tracking the location of singularities and critical points in the analytic continuation of the mapping function. We show that by treating the critical points, it is easy to observe finite-time blow-up, and the evolution equations may be written in exact form using complex residues. We present solutions that start with cusps on one interface and end with cusps on the other, as well as solutions that have the bubble contracting to a point. For the latter solutions, the bubble approaches an ellipse in shape at extinction.

Modelling the interaction of keratinocytes and fibroblasts during normal and abnormal wound healing processes

The crosstalk between fibroblasts and keratinocytes is a vital component of the wound healing process, and involves the activity of a number of growth factors and cytokines. In this work, we develop a mathematical model of this crosstalk in order to elucidate the effects of these interactions on the regeneration of collagen in a wound that heals by second intention. We consider the role of four components that strongly affect this process: transforming growth factor-beta, platelet-derived growth factor, interleukin-1 and keratinocyte growth factor. The impact of this network of interactions on the degradation of an initial fibrin clot, as well as its subsequent replacement by a matrix that is mainly comprised of collagen, is described through an eight-component system of nonlinear partial differential equations. Numerical results, obtained in a two-dimensional domain, highlight key aspects of this multifarious process such as reepithelialisation. The model is shown to reproduce many of the important features of normal wound healing. In addition, we use the model to simulate the treatment of two pathological cases: chronic hypoxia, which can lead to chronic wounds; and prolonged inflammation, which has been shown to lead to hypertrophic scarring. We find that our model predictions are qualitatively in agreement with previously reported observations, and provide an alternative pathway for gaining insight into this complex biological process.

Critical time scales for advection–diffusion–reaction processes

The concept of local accumulation time (LAT) was introduced by Berezhkovskii and coworkers in 2010–2011 to give a finite measure of the time required for the transient solution of a reaction–diffusion equation to approach the steady–state solution (Biophys J. 99, L59 (2010); Phys Rev E. 83, 051906 (2011)). Such a measure is referred to as a critical time. Here, we show that LAT is, in fact, identical to the concept of mean action time (MAT) that was first introduced by McNabb in 1991 (IMA J Appl Math. 47, 193 (1991)). Although McNabb’s initial argument was motivated by considering the mean particle lifetime (MPLT) for a linear death process, he applied the ideas to study diffusion. We extend the work of these authors by deriving expressions for the MAT for a general one–dimensional linear advection–diffusion–reaction problem. Using a combination of continuum and discrete approaches, we show that MAT and MPLT are equivalent for certain uniform–to-uniform transitions; these results provide a practical interpretation for MAT, by directly linking the stochastic microscopic processes to a meaningful macroscopic timescale. We find that for more general transitions, the equivalence between MAT and MPLT does not hold. Unlike other critical time definitions, we show that it is possible to evaluate the MAT without solving the underlying partial differential equation (pde). This makes MAT a simple and attractive quantity for practical situations. Finally, our work explores the accuracy of certain approximations derived using the MAT, showing that useful approximations for nonlinear kinetic processes can be obtained, again without treating the governing pde directly.

An investigation of market segmentation theory and its impact on effective fundraising

This paper presents the findings of an indepth study into the effects and success of marketing segmentation, target marketing and fundraising. Organisations are constantly seeking new ways and more efficient means to raise funds so that they can fulfill their objectives. These organisations review and evaluate their resources to gain competitive advantage and increased fundraising success...

ACE research briefing paper 004 : emerging and young high potential start-ups

In this report we take a look at what separates high potential emerging and young start-ups from others. We compare the characteristics, intentions and behaviours of start-ups that we judge to be 'high potential' with other start-ups. We utilise the first two years of data from the CAUSEE study. We also compare Australian start-ups with a similar study conduced in the US.

Tear film surface quality with rigid and soft contact lenses

Objectives: To measure tear film surface quality (TFSQ) using dynamic high-speed videokeratoscopy during short-term (8 hours) use of rigid and soft contact lenses. Methods: A group of fourteen subjects wore 3 different types of contact lenses on 3 different non-consecutive days (order randomized) in one eye only. Subjects were screened to exclude those with dry eye. The lenses included a PMMA hard, an RGP (Boston XO) and a soft silicone hydrogel lens. Three 30 second long high speed videokeratoscopy recordings were taken with contact lenses in-situ, in the morning and again after 8 hours of contact lens wear, both in normal and suppressed blinking conditions. Recordings were also made on a baseline day with no contact lens wear. Results: The presence of a contact lens in the eye had a significant effect on the mean TFSQ in both natural and suppressed blinking conditions (p=0.001 and p=0.01 respectively, repeated measures ANOVA). TFSQ was worse with all the lenses compared to no lens in the eye (in the afternoon during both normal and suppressed blinking conditions (all p<0.05). In natural blinking conditions, the mean TFSQ for the PMMA and RGP lenses was significantly worse than the baseline day (no lens) for both morning and afternoon measures (p<0.05). Conclusions: This study shows that both rigid and soft contact lenses adversely affect the TFSQ in both natural and suppressed blinking conditions. No significant differences were found between the lens types and materials. Keywords: Tear film surface quality, rigid contact lens, soft contact lens, dynamic high-speed videokeratoscopy

Diurnal Variation of Retinal Thickness with Spectral Domain OCT

Purpose. To investigate whether diurnal variation occurs in retinal thickness measures derived from spectral domain optical coherence tomography (SD-OCT). Methods. Twelve healthy adult subjects had retinal thickness measured with SD-OCT every 2 h over a 10 h period. At each measurement session, three average B-scan images were derived from a series of multiple B-scans (each from a 5 mm horizontal raster scan along the fovea, containing 1500 A-scans/B-scan) and analyzed to determine the thickness of the total retina, as well as the thickness of the outer retinal layers. Average thickness values were calculated at the foveal center, at the 0.5 mm diameter foveal region, and for the temporal parafovea (1.5 mm from foveal center) and nasal parafovea (1.5 mm from foveal center). Results. Total retinal thickness did not exhibit significant diurnal variation in any of the considered retinal regions (p > 0.05). Evidence of significant diurnal variation was found in the thickness of the outer retinal layers (p < 0.05), with the most prominent changes observed in the photoreceptor layers at the foveal center. The photoreceptor inner and outer segment layer thickness exhibited mean amplitude (peak to trough) of daily change of 7 ± 3 μm at the foveal center. The peak in thickness was typically observed at the third measurement session (mean measurement time, 13:06). Conclusions. The total retinal thickness measured with SD-OCT does not exhibit evidence of significant variation over the course of the day. However, small but significant diurnal variation occurs in the thickness of the foveal outer retinal layers.