Controlling soliton refraction in optical lattices

We show in the framework of the 1D nonlinear Schrödinger equation that the value of the refraction angle of a fundamental soliton beam passing through an optical lattice can be controlled by adjusting either the shape of an individual waveguide or the relative positions of the waveguides. In the case of the shallow refractive index modulation, we develop a general approach for the calculation of the refraction angle change. The shape of a single waveguide crucially affects the refraction direction due to the appearance of a structural form factor in the expression for the density of emitted waves. For a lattice of scatterers, wave-soliton interference inside the lattice leads to the appearance of an additional geometric form factor. As a result, the soliton refraction is more pronounced for the disordered lattices than for the periodic ones.

Does competitive entry structurally change key marketing metrics?

To what extent does competitive entry create a structural change in key marketing metrics? New players may just be a temporal nuisance to incumbents, but could also fundamentally change the latter's performance evolution, or induce them to permanently alter their spending levels and/or pricing decisions. Similarly, the addition of a new marketing channel could permanently shift shopping preferences, or could just create a short-lived migration from existing channels. The steady-state impact of a given entry or channel addition on various marketing metrics is intrinsically an empirical issue for which we need an appropriate testing procedure. In this study, we introduce a testing sequence that allows for the endogenous determination of potential change (break) locations, thereby accounting for lead and/or lagged effects of the introduction of interest. By not restricting the number of potential breaks to one (as is commonly done in the marketing literature), we quantify the impact of the new entrant(s) while controlling for other events that may have taken place in the market. We illustrate the methodology in the context of the Dutch television advertising market, which was characterized by the entry of several late movers. We find that the steady-state growth of private incumbents' revenues was slowed by the quasi-simultaneous entry of three new players. Contrary to industry observers' expectations, such a slowdown was not experienced in the related markets of print and radio advertising.

Evaluating authentic behaviour change in leadership development programmes

The global economic crisis that hit the western countries strongly has emphasised the need to abandon the economic-performance significance of leadership and return to a meaning-making significance. While a lot of research has been done in the field of leadership and management disciplines, little has been done on how to develop leadership. This study evaluated the degree in which leadership training in the market-place today was effective at developing authentic leadership and, therefore, at changing individual behaviour. Since none of the leadership theories address how behavioural change is actually achieved, theories of change were integrated in the current study. A conceptual model combining Authentic Leadership Development (ALD) theory and the Theory of Planned Behaviour (TPB) was proposed. Furthermore, this study explored the relationship between a positive contemplation of change and the actual change observed in individuals after the leadership intervention. In order to test this conceptualisation, a longitudinal quasi-experimental study was conducted. Leaders were surveyed in this study one month before and one month after the programme. Three complementary questionnaires were distributed to participants in one of four leadership development programmes (two corporate initiatives and two business-school programmes). Analyses showed that leaders who attended a leadership intervention (as compared to a control group) developed higher levels of authentic leadership, as rated by them-selves and others in their working environment and controlling for baseline scores. The results also indicated that intentions were developed through the interventions and that the development of such intentions translated into changes in authentic behaviour. Intentions mediated the relationship between attitude and authentic leader-ship. In addition, when contemplation of change was high and attitudes towards authentic leadership were positive, the development of intentions was stronger. The implications of these findings for the theory and practice of leadership development programmes and the impact on organisational performance are discussed.

Long-term efficacy of orthokeratology contact lens wear in controlling the progression of childhood myopia

Purpose: The primary outcome of this study is to compare the axial length growth of white European myopic children wearing orthokeratology contact lenses (OK) to a control group (CT) over a 7-year period. Methods: Subjects 6–12 years of age with myopia −0.75 to −4.00DS and astigmatism ≤1.00DC were prospectively allocated OK or distance single-vision spectacles (SV) correction. Measurements of axial length (Zeiss IOLMaster), corneal topography, and cycloplegic refraction were taken at 6-month intervals over a 2-year period. Subjects were invited to return to the clinic approximately 5 years later (i.e., 7 years after the beginning of the study) for assessment of their ocular refractive and biometric components. The CT consisted of 4 SV and 12 subjects who switched from SV to soft contact lens wear after the initial 2 years of SV lens wear. Changes in axial length relative to baseline over a 7-year period were compared between groups. Results: Fourteen and 16 subjects from the OK and CT groups, respectively, were examined 6.7 ± 0.5 years after the beginning of the study. Statistically significant changes in the axial length were found over time and between groups (both p <0.001), but not for the time*group interaction (p = 0.125). The change in the axial length for the OK group was 22% (p = 0.328), 42% (p = 0.007), 40% (p = 0.020), 41% (p = 0.013), and 33% (p = 0.062) lower than the CT group following 6, 12, 18, 24, and 84 months of lens wear, respectively. Conclusion: A trend toward a reduction in the rate of axial elongation of the order of 33% was found in the OK group in comparison to the CT group following 7 years of lens wear.